What is an organ system?
a group of organs each with specific structures and functions that coordinate and integrate with one another
What are examples of an organ system?
Nervous, circulatory, respiratory, digestive, excretory, endocrine, and reproductive
What makes up the nervous system?
brain, spinal cord, nerves, and associated ganglia
Ganglia are not as ____ as _____, but they do have a specific _____ and ____.
obvious, organs, structure, function
What makes up the circulatory system?
heart, blood vessels, lymph nodes, lymph vessels
What is the general function of the nervous system?
short term coordination and integration of body functions
What is the nervous system controlled by?
electrochemical communication (nerve impulses or action potentials)
Without impulses and action potentials, what would happen?
There would be no coordination of body functions
What are the properties of the nervous system?
1. Irritability or excitability
What is irritability or excitability?
the ability to react to stimuli followed by the generation of nerve impulses
What is conductivity?
the ability to transmit nerve impulses/APs from one area of the body to another
(if the NS could not do this, there would be no function for APs or nerve impulses)
What is the functional sequence of events for short term coordination?
1. reception of stimuli
2. conversion of stimuli
3. transmission of APs
4. Production of a response or an action
Reception of stimuli is received from where?
from external or internal environments
Conversion of stimuli -->
into nerve impulses/APs
Transmission of APs -->
over correct pathways
What is an example of production of a response or an action for short term coordination?
Muscle contraction --> gland secretion
What are the two divisions of the nervous system?
central nervous system and peripheral nervous system (CNS, PNS)
What does the CNS consist of?
the brain and spinal cord
What does the PNS consist of?
1. Nerves and ganglia of somatic NS
2. Nerves and ganglia of autonomic NS
What are the nerves and ganglia of the somatic NS associated with?
What are ganglia?
a collection of nerve cell bodies
What are the two divisions of the autonomic nervous system?
1. Sympathetic NS
2. Parasympathetic NS
What are the 3 histological elements of the nervous system?
Neurons (nerve cells), neurological/glial cells, and white fibrous collagenous connective tissue
What is another term for neuron?
What is another term for nerve cells?
What are neurons?
the basic unit of cellular function
What is the function of neurons?
they generate and conduct nerve impulses
How many neurons are in the brain?
over 100 billion
How many neurons are in the nervous system?
over 1 trillion
Neuroglial/glial cells provide what?
A variety of functions
How many glial cells are in the nervous system compared to neurons?
What is another term for schwann cells?
What is another term for neurolemmocytes?
Where are schwann cells found?
only in the PNS, NOT in the brain or spinal cord!
What are schwann cells described as?
being insulator cells
What are found associated with portions of neurons?
Schwann cells are found associated with what?
portions of neurons (axons and dendrites)
Where is white fibrous collagenous connective tissue found?
mainly in peripheral nerves, little is found directly in the brain
What is the dura mater?
a membrane that surrounds the brain
What is the dura mater made of?
white collagenous connective tissue
What are the 2 component parts of a neuron?
the cell body and the processes of fibers
What is another name for the cell body?
Where is the nucleus found?
in the cell body
Where are the processes of fibers?
they extend off the cell body
What are the two processes of fibers called?
dendrite and axon
Describe a dendrite
there are one or more (200) and usually short in length
Describe an axon
there is ONLY one and most often longer in length than dendrites
How long is the longest axon?
Where is the longest axon found?
in the posterior thigh region
What are the three morphological classifications of neurons?
What is the function of pseudo-unipolar neuron axons?
they carry APs to the cell body then continue to carry the AP away from the cell body
Describe a pseudo-unipolar neuron fiber
the fiber is divided in two but in both cases, it is an axon, and the term dendrite is not used in classification
What is typical of sensory neurons?
they have a fiber that is divided in two but in both cases, they are axons
Sensory neurons have cell bodies located in what?
cranial and spinal ganglia
Describe a bipolar neuron
it has one dendrite and one axon
What are bipolar neurons associated with?
Where are bipolar neurons found?
1. the retina of the eye
2. the olfactory epithelium of the nose (detect odors)
3. the taste buds of the tongue
Describe a multipolar neuron
has many dendrite but ONLY ONE axon
What is the most common neuron in the nervous system?
the multipolar neuron
Which neuron do we focus on in terms of structure and function?
the multipolar neuron
The multipolar neuron is the most focused on in terms of what?
structure and function
What are the 3 functional classification of neurons?
What is another term for motor neurons?
What is another term for sensory neurons?
What is another term for interneurons?
association neurons or internuncial (older term) neurons
Where do motor neurons transmit APs?
from the brain/spinal cord to muscles or glands
What kind of neuron is a motor neuron?
Where do sensory neurons transmit APs?
from peripheral receptors to spinal cord or brain
What kind of neuron is a sensory neuron?
mostly pseudo unipolar
Where do interneurons transmit APs?
from sensory neurons to other interneurons or to motor neurons
What kind of neuron is an interneuron?
Where are interneurons confined to?
a region of the CNS called the gray matter
Where are interneurons found?
ONLY in gray matter
What is a dendrite?
short fibers which extend off of the cell body/perikaryon
What is the function of a dendrite?
they transmit APs TO the cell body
Some dendrite have tips that are modified into what?
What does the cell body/perikaryon contain?
usual cell organelles suspended in cytosol
What is the nucleus?
a cell organelle that contains the nucleolus and chromatin
Where is the nucleolus located?
in the nucleus
Where are chromatin located?
in the nucleus
Where are cell organelles found?
in the cell body suspended in cytosol
What is mitochondria?
a cell organelle found also in synaptic knobs of the axon
What is the golgi complex?
a cell organelle that produces vesicles containing neurotransmitters
Where are neurotransmitters made?
in the cell body
Where are neurotransmitters incorporated into vesicles?
the golgi apparatus
What happens to neurotransmitters in the golgi apparatus?
they are incorporated into vesicles
What is nissl substance?
concentrated areas of rough ER and RNA
The areas where you find the nissl substance, are where you will also find _____.
The cytoskeletal components maintain what?
1. the shape of neurons
2. the cell shape
Cytoskeletal components contain what structures?
What is another name for microtubules?
Where are cytoskeletal components found?
in all parts of the neuron, cell bodies, dendrites and axons
What is an axon?
a single long fiber that extends AWAY from the cell body
Can axons be branched?
What is the branch of an axon called?
an axon collateral
Where do axons carry APs?
from the cell body AWAY to other cells
Axons arise from where?
the cell body at a region called the axon hillock
Where do APs originate?
the axon hillock
What is the axon hillock?
a funnel shaped structure that leads into cell fibers
Axons or its _____ end in ____ ____.
collaterals, axon terminals
Are axon terminals highly branched?
Where do axon terminals end?
in structures called synaptic knobs
What is another term for synaptic knob?
boutons or end feet
What is another term for bouton?
Synaptic knob, end feet
What is another name for end feet?
synaptic knob, bouton
What does the synaptic knob innervate?
other neurons, muscle cells, or gland cells
What is a neurotubule's function?
they assist in the transport of neurotransmitters vesicles down the axon
Neurotubules allow ___ ___ to move from the ___ ___ to ____ ___.
synaptic vesicles, cell body, synaptic knob
Where do axons send APs?
away from the cell body
What are branches of axons called?
Where can one axon send one signal?
To several different cells
What are the two types of axons and dendrites in the PNS?
myelinated and unmyelinated
What do schwann cells do?
1. they line up on one axon
2. each one individually wraps around the axon
3. they produce a myelin sheath
What is a myelin sheath composed of?
layers of schwann cell plasma membranes rich in the lipid myelin
What is myelin?
Schwann cell plasma membranes are rich in what?
What type of cell is a schwann cell?
a glial cell in the PNS
What is the neurilemma?
a layer of schwann cell cytoplsam outside of the myelin sheath
Schwann cells exert a very important ____ on ____ that have them.
Where do schwann cells NOT cover?
the axon hillock or axon terminals
What are the ends of axons referred to?
What is the nodes of ranvier?
spaces between schwann cells where an axon is NOT covered
In the nodes of ranvier, the plasma membrane of the axon is not...
exposed to the extracellular fluid
Where is extracellular fluid located?
outside of the axon
Unmyelinated axons have several what?
fibers (axons or dendrites)
What fiber is most commonly found in unmyelinated axons?
Where are axons in unmyelinated embedded?
in the cytoplasm of a series of schwann cells
Multiple fibers in unmyelinated axons prevent what?
schwann cells from coiling around the axons
Can the multiple fibers of an unmyelinated axon form a myelin sheath?
In unmyelinated axons, axon _____ are exposed to ____ all along the length of ____.
membranes, ECF, axons
Peripheral components include what?
2. perineurium and fascicles
What is the epineurium?
outer covering of peripheral nerve
What is the epineurium made of?
white fibrous connective tissue
The epineurium layer covers what?
the outer surface of the peripheral nerve
What is the perineurium?
a layer of white fibrous connective tissue that extends from the epineurium into a nerve and makes compartments called fascicles
What is the perineurium made of?
white fibrous connective tissue
Where does the perineurium extend from?
the epineurium into a nerve
The perineurium makes compartments called?
What are fascicles?
sub-compartments of a nerve
The perineurium serves as the...
outer sheath of a fascicle
The fascicle is a group of...
axons and/or dendrites
The fibers of the axons and/or dendrites of a fascicle...
may be myelinated or unmyelinated
What is the endoneurium?
an areolar tissue that covers the surface of each fiber in a fascicle
What is a function of connective tissue components?
serve as a pathway for blood vessels to penetrate a nerve
What is the pathway for blood vessels to penetrate a nerve?
What is the function of the epineurium?
it holds fascicles together as a nerve
The function of the perineurium?
holds fibers together as a fascicle
The function of the endoneurium?
it interconnects fibers
Where are neurologlial cells found?
only in the CNS and PNS
Where are schwann cells found?
What do schwann cells produce?
myelinated axons and myelinated dendrites (mostly axons)
Where are oligodendrocytes found?
What do oligodendrocytes produce?
myelinated axons and myelinated dendrites from late fetus through 2 years
What is a glioma?
a brain tumor
What are brain tumors derived from?
glial cells, NOT neurons
What is multiple sclerosis?
a demyelinating disease (probably auto-immune)
The break down of myelin sheaths happens in what disease?
In multiple sclerosis, what happens to myelin sheaths?
they are broken down
What is an auto-immune disease where myelin sheaths are destroyed?
Microgliocytes are a type of what?
What are microgliocytes?
macrophage-like cells found only in the CNS
Where are microgliocytes found?
Microgliocytes possess what?
ameboid movement (they can move about)
What is the function of a microgliocyte?
to destroy microorganisms and dead cellular debris in tissues of the nervous system
What happens in a hemorrhagic stroke?
damage occurs to blood vessels with bleeding into nervous tissues
In a hemorrhagic stroke, large numbers of microgliocytes appear where?
at the site to eliminate dying tissues
What are microgliocytes attracted to?
damage area of blood vessels
What are astrocytes nicknamed?
star shaped cells
Where are astrocytes found?
What kind of cells are astrocytes?
Astrocytes connect ___ to ___.
neurons, blood vessels
What do astrocytes assist in?
the regulation of chemical concentration of substances in the ECF of the CNS
What is the BBB?
the blood-brain barrier
What is the BBB established by?
morphology of brain capillaries
What is a brain capillary?
tight junctions of endothelial cells
What is the BBB function?
it impedes movement of water-soluble substances in ECF of brain and spinal cord tissues
What 3 elements move by special transport mechanisms?
Na+, K+, and glucose
Na+, K+ and glucose move by?
special transport mechanisms
Can penicillin cross the BBB?
Can erythromycin cross the BBB?
What are examples of lipid-soluble substances?
alcohol, anesthetics, and heroin
What can pass through the BBB easily?
How do lipid-soluble substances reach the brain tissue?
With ease because of lipid solubility
How do astrocytes contribute to BBB?
What do perivascular feet of astrocytes associated with blood capillaries do?
help control the concentration/level of K+ in the brain ECF
What helps the concentration/level of K+ in the brain ECF?
perivascular feet of astrocytes associated with blood capillaries
Where are ependymal cells located?
they line ventricles of brain and central canal of spinal cord
What is a ventricle?
a hollow fluid-filled interior space or cavity
How many ventricles in brain and spinal cord?
Covered capillaries of ventricles of brain and spinal cord are made of what?
a combination of ependymal cells and capillaries (choroid plexes)
What is a choroid plexes?
a combination of blood capillaries and the covering of ependymal cells
What do ependymal cells have for moving CSF through ventricles and central canal?
Ependymal cells have ciliated surfaces for what function?
moving cerebrospinal fluid through ventricles and central canal
How is CSF produced?
by filtration of blood through choroid plexes
What do ependymal cells help control?
substance levels in CSF
How do ependymal cells control substance levels in CSF?
by special transport mechanisms
What is a resting potential?
electrical potential difference that exists across the cell membrane of a neuron that is NOT conducting an action potential
What is a voltage?
electrical potential difference
Resting potentials are mostly studied in...
What is the value of the resting potential of an axon?
What is the basis of a resting potential?
it is produced by UNEQUAL electrical charges on either side of the axon membrane
What is the basis produced by?
UNEQUAL electrical charges on either side of the axon membrane
What are factors that produce the unequal charge distribution?
1. sodium pump
2. differential permeability of Na+ and K+ in terms of diffusion
3. presence of non-diffusible anions
The sodium pump is an active ____ ____, therefore it requires ____.
transport mechanism, ATP
What is the sodium pump function?
it moves 3 Na+ OUT of the axon and 2 K+ INTO the axon
Why is ATP used in sodium pump?
because ions are moving against their concentration gradients
What does the sodium pump establish outside the axon in ECF?
-high Na+ concentration
-low K+ concentration
What does the sodium pump establish inside the axon in ICF?
-low Na+ concentration
-high K+ concentration
What does the sodium pump establish but not maintain?
the resting potential
How do Na+ and K+ ions diffuse?
through always open or non-gated leak channels with their concentration gradient (high to low)
Potassium diffuses ____ than sodium.
K+ diffuses ___ of the axon 100x ___ than Na+ diffuses ____ the axon through their respective ___ ___.
OUT, faster, INTO, leak channels
Why is ICF negative relative to the ECF?
because the axon is losing more positive charges (K+) than it is gaining positive charges (Na+)
Because the axon is losing more positive charges (K+) than it is gaining positive charges (Na+)...
the ICF is negative relative to ECF
What are non-diffusible anions?
negatively charged proteins in the ICF
Non-diffusible anions can't what?
move out of the axon
Non-diffusible anions contribute what?
a small degree of negative charges to the ICF
What ion is responsible for the resting potential?
K+ ions move ___ of an axon 100x ___ than Na+ ions move ___ an axon by ____.
OUT, faster, INTO, diffusion
The ICF is relatively more negative compared to what?
the charge in the ECF
Why is the ICF more negative compared to the ECF?
because there is a net loss of positive charges in the ICF
What is a threshold?
point where a local depolarization(s) stimulate an action potential
Another term for local depolarizations?
How many local depolarizations does it take to raise the resting potential to the threshold potential?
at least 2 or more
It takes at least two or more local depolarizations to do what?
raise the resting potential to the level of threshold potential
What is the level of threshold potential?
When is an action potential stimulated?
once it's at the threshold potential
When a threshold potential is reach, what happens?
an AP is stimulated
Sequence of events of AP being stimulated: step one
Axon is at resting potential
What is resting potential for an axon?
Sequence of events of AP being stimulated: step two
adequate stimulus is applied to an axon
What is an example of an adequate stimulus?
heat, cold, electrical, mechanical
What does an adequate stimulus result in?
increased Na+ permeability
Sequence of events of AP being stimulated: step 3
increased Na+ permeability (Na+ can move from outside of axon to inside)
How does Na+ move from the ECF into the ICF?
through Na+ voltage-gated channels of the axon membrane
Sequence of events of AP being stimulated: step 4
Reversal of electrical charge due to Na+ entry-full depolarization results in action potential
What makes the ICF become relatively positive?
enough Na+ enters the axon
What makes the ECF become relatively negative?
enough Na+ enters the axon
When enough Na+ enters the axon, membrane potential goes from?
-70mV to +30mV
What is the value of an AP?
Sequence of events of AP being stimulated: step 5
What happens during repolarization?
1. Na+ voltage-gated channels close
2. K+ voltage-gated channels open
What enters the axon during repolarization?
little to no Na+
What exits the axon during repolarization?
large quantities of K+
What does the loss of K+ in the axon do?
it returns the membrane potential back to -70mV or lower
What is hyperpolarization?
if an axon loses more K+ than Na+ gained
Ion concentrations after hyperpolarization:
are NOT normal in ICF so the sodium pump returns ion concentrations to normal levels associated with the resting potential
All or none law
AP has a full magnitude of 100mV or it does NOT occur at all; either you get the full AP or you get nothing
What are the refractory periods?
absolute and relative
Absolute refractory period
threshold potential to end of repolarization
-55 to +30 to -70
Relative refractory period
Importance of absolute refractory period
no other AP can be stimulated during absolute refractory period
In absolute refractory period...
it is impossible to stimulate a second AP
What can a higher than normal stimulus produce?
an AP during relative refractory period
What does the relative refractory period limit?
the number of APs that can pass over an axon (100-1000/sec)
Unmyelinated axon-sequence of events
1. axon hillock depolarizes and repolarizes
2. segment to segment stimulation
3. AP is self-propagating
Segment to segment stimulation: where does electron current flow from?
depolarized axon hillock to next adjacent segment of the axon causing depolarization at the new location and is followed by a repolarization
stimulates a series of APs down the length of an axon
AP is self propagating (stimulates a series of APs down the length of an axon)
Continuous conduction occurs in what kind of axon?
Myelinated axons: sequence of events
1. axon hillock depolarizes and repolarizes
2. depolarization of axon hillock causes electrical current to flow to the first node of ranvier, and it will go through a depolarization/repolarization cycle
What does the first nodes of ranvier stimulate?
the same reaction in the next node
What is saltatory conduction?
APs jumping from node to node
Where does saltatory conduction occur?
myelinated axons ONLY
How do myelinated fibers conduct?
faster than unmyelinated
What is conduction velocity?
the speed of propagation down the length of an axon
Large vs. small diameter axons:
conduction is faster in LARGE diamater axons
Myelinated vs. unmyelinated axons: conduction
conduction is 10x faster in myelinated axons compared to unmyelinated axons of the same diameter
Why are myelinated faster?
because of saltatory conduction
What does saltatory conduction eliminate?
a large surface area of axon membrane that must participate in conduction (thats why it is faster)
Example of myelinated axons involved in conduction:
hand on a burner; you want myelinated axons involved because they are faster
Does the axon membrane under schwann cells depolarize?
What part of the axon membrane depolarizes?
the nodes of ranvier in myelinated axons
In AP trasmission from neuron to neuron, how are neurons sent?
the presynaptic neuron sends AP to a postsynaptic neuron
What is a synapse?
site where two neurons associate with one another
Types of synapse?
electrical and chemical
What happens during electrical synapse?
AP passes through gap junctions between neurons without use of chemicals
Where does electrical synapse occur?
What does chemical synapse require?
release of a chemical neurotransmitter from a presynaptic neuron to stimulate an AP in a post-synaptic neuron
What does the structure of chemical synapse include?
1. synaptic knob
2. synaptic cleft
3. postsynaptic membrane
Synaptic knob job in chemical synapse
a synaptic knob from a presynaptic neuron terminates on a dendrite, cell body, or axon of a postsynaptic neuron
What do synaptic knobs contain?
vesicles that are filled with neurotransmitters
What are neurotransmitters?
a chemical that is excitatory or inhibitory
What is the synaptic cleft?
the space between the presynaptic and postsynaptic neurons
What is the postsynaptic membrane?
portion of the cell membrane of a postsynaptic neuron at the synapse
What does the postsynaptic membrane contain?
receptors (protein molecules) that specifically bind to a neurotransmitter as it crosses the synapse
What are the 3 chemical synaptic associations?
axon to dendrite
axon to cell body
axon to axon (FEW, INHIBITORY)
Both _____ and ____ presynaptic neurons may ____ on the same _____ neuron.
excitatory, inhibitory, synapse, postsynaptic
What happens during "excitation at the synapse"?
presynaptic neuron stimulates an AP in a postsynaptic neuron
Sequence of excitation at the synapse: step 1
AP moves down presynaptic axon terminal to synaptic knob
Sequence of excitation at the synapse: step 2
AP arrives at synaptic knob; stimulates Ca+2 entry into synaptic knob
Sequence of excitation at the synapse: step 3
-Ca+2 causes vesicles to release their neurotransmitter by exocytosis into the synaptic cleft
-it diffuses across the synaptic cleft
-it combines with receptors on the postsynaptic membrane
Sequence of excitation of the synapse: step 4
if sufficient amounts of neurotransmitter combine with the receptors, this initiates local depolarization called excitatory postsynaptic potentials
ESPSs can ____, reach ____ potential and initiate APs in the ____ ____ of the _____ neuron.
summate, threshold, axon hillock, postsynaptic
Examples of excitatory neurotransmitters:
-dopamine and substance P
What are dopamine and substance P?
pain impulses in the spinal cord
What are different ways to eliminate the neurotransmitter?
1. enzymatic degradation in synaptic cleft
2. re-uptake into presynaptic neuron
3. diffusion out of synaptic cleft to ECF
(these all destroy ACh)
Inhibition at the synapse:
presynaptic neuron causes hyperpolarization in a postsynaptic neuron
Sequence of inhibition at the synapse: A
a. AP moves down presynaptic axon terminal to synaptic knob
Sequence of inhibition at the synapse: B
b. AP arrives at synaptic knob; stimulates Ca+2 entry into synaptic knob
Sequence of inhibition at the synapse: C
c. Ca+2 causes vesicles to release their neurotransmitter by exocytosis into the synaptic cleft and it diffuses across the synaptic cleft and combines with receptors on the postsynaptic membrane
What are steps a-c describing?
the excitation of the synapse
Sequence of inhibition at the synapse: D
d. sufficient amount of neurotransmitter combines with its receptors on postsynaptic membrane
Sequence of inhibition at the synapse: E
e. increase permeability of K+ or Cl-1 in the postsynaptic membrane
What is Cl-1?
There is an increased ____ of ____ from the postsynaptic neuron.
There is an increased ____ of ____ into the postsynaptic neuron.
During step E, what happens for inhibition?
potassium leaves and chloride enters the postsynaptic neuron
Potassium leaves and chloride enters the postsynaptic neuron for what?
Increased K+ or Cl- permeability causes the resting potential to do what?
go from -70mV to -80mV (hyperpolarization)
The resting potential moving from -70mV to -80mV is...
difficult to stimulate
What is an IPSP?
an inhibitory postsynaptic potential
What is an inhibitory postsynaptic potential?
the resting potential moving from -70mV to -80mV
IPSP prevents what?
the postsynaptic neuron from being stimulated under normal conditions
EPSP stimulates what easily?
IPSP stimulates postsynaptic neurons...
with more difficulty than EPSPs
Examples of inhibitory neurotransmitters?
gamma-amino butyric acid
Inhibitory neurotransmitters are very important in what?
nervous tissues, stimulation, and inhibition
Enkephalins and endorphins are important for what?
repressing painful stimuli in CNS
Which two inhibitory neurotransmitters are important in repressing painful stimuli in the CNS?
enkephalins and endorphins
What is the neuro transmitter junction structure?
end plate, synaptic cleft, and motor plate (a structure)
Sequence of events: step 1
1. movement of AP to end foot uptake of Ca release
Sequence of events: step 2
Ach diffuses across synaptic cleft and combines with its receptors on the motor end plate
If enough ACh combines with receptors...
this initiates end plate potentials in the motor end plate
EPPS are the same as what?
EPSPs, but larger in magnitude
What is the EPPs function?
they summate and initiate an AP that spreads from the neuromuscular junction over the entire surface of the sarcolemma, causing the cell to contract
What causes the cell to contract?
the EPPs summate and initiate an AP that spreads from the neuromuscular junction over the entire surface of the sarcolemma
Acetylcholine esterase does what?
destroys ACh in the synaptic cleft after it has stimulated the muscle cell to contract
What are 3 exogenous chemicals affecting transmission at the neuromuscular junction?
curare, atropine, and physostigmine
Curare has a similar chemical structure as?
Curare combines with ____ ____ on the ____ ____.
ACh receptors, end plate
What does curare prevent?
ACh from stimulating APs and causes paralysis
How long does it take for succinyl choline to cause paralysis?
What is another name for physostigmine?
What is eserine's function?
it inhibits acetylcholine esterase in synaptic cleft; ACh is not destroyed so it keeps stimulating the motor end plate and muscle cell contractions
Myasthenia gravis affects how many?
1:5000 people that have normal nerves and normal muscles
Symptoms of myasthenia gravis?
muscular weakness, easy fatigue, paralysis
What kind of disease is myasthenia gravis?
autoimmune disease; antibodies are made against ACh receptors and ACh cannot properly stimulate the motor end plate
What is treatment for myasthenia gravis?
What does physostigmine inhibit?
What does physostigmine allow ACh to do?
exist in the synaptic cleft for longer than normal, giving it time to stimulate the motor end plate
Physostigmine is NOT a ____, it only _____ symptoms.
What is a palliative agent?
an agent that alleviates symptoms of a disease
three consecutive tissues that surround the brain and spinal cord
outermost membrane made of white fibrous connective tissue
What is the dura mater composed of?
two layers over the brain
What are the two layers dura mater is composed of?
1. cranial/periosteal dura mater
2. meningeal dura mater
What is another name for cranial dura mater?
periosteal dura mater
What does the cranial dura mater do?
it makes direct contact with cranial bones
Where is the meningeal dura mater found?
below and separate from the cranial dura mater
In some areas, meningeal DM layers are separated by?
spaces filled with blood
What is a venous blood sinuses?
spaces filled with blood
Example of venous blood sinuses?
superior sagittal sinus
In some areas, the two layers of meningeal DM are?
fused and form a partition
a partition between two cerebral hemispheres
a partition between the cerebrum and cerebellum
has one layer called the meningeal dura mater
What is another term for meningeal DM?
spinal dura mater
What is the meningeal/spinal DM of the spinal cord continuous with?
the meningeal DM of the brain
potential free space located between the meningeal DM of brain/spinal cord and the arachnoid membrane
What is a subdural hematoma?
a blood clot in the subdural space
What is an arachnoid?
the middle meninge
adjacent to meningeal DM of brain and spinal cord
fine partitions that create compartments within sub-arachnoid space below arachnoid membrane
filled with CSF; contains small arterioles
inner meninge, highly vascularize and is in direct contact with the brain and spinal cord
inflammation of meninges caused by bacterial or viral infections
major portion of human brain
Fissures and lobes:
deep groves that subdivide the cerebrum into L and R cerebral hemispheres
Each hemisphere is divided into:
Longitudinal fissure location:
Longitudinal fissure creates:
left and right cerebral hemispheres
Central fissure/sulcus of rolando:
separates frontal and parietal lobes
Lateral fissure of slyvius:
separates frontal and parietal lobes from temporal lobe
separates parietal lobe from occipital lobe, back of cerebrum
"5th lobe" located at base of lateral fissure
Which lobe is not visible at the surface of the brain?
Where is the insula found?
underneath parietal and frontal lobes
made of gray matter
convulsions or ridges
shallow grooves that separate gyri from each other
Sulci are ____ in depth compared to ____.
located interior to cerebral cortex gray matter (under brain)
Regions of myelinated nerve fibers form what?
arcuate, association, commissural, projection
connect adjacent gyri within the same lobe to each other (LOCAL)
connect DISTANT gyri within different lobes of the same cerebral hemisphere to each other
connect two corresponding lobes in L and R cerebral hemispheres to each other
connect cerebral cortex to ALL OTHER parts of the CNS such as basal ganglia, thalamus, hypothalamus, and spinal cord
Physiological divisions of cerebral cortex:
What are the two types of motor cortex?
primary motor cortex, broca's area
Primary motor cortex:
located in frontal lobe anterior to the fissure of rolando
Primary motor cortex function:
initiates and controls contraction of skeletal muscles
Example of primary motor cortex function:
tells you to pick up a pencil...the beginning action
found in the L frontal lobe
Broca's area function:
initiates contraction of muscles controlling speech patterns
regions of the cortex that interpret sensory impulses
Parts of sensory cortex:
1. primary sensory/somesthetic cortex
2. olfactory cortex
3. auditory cortex
4. taste cortex
5. visual cortex
Primary sensory/somesthetic cortex:
found in parietal lobe posterior to the fissure of rolando
Primary sensory/somesthetic cortex function:
specifically interprets sensory stimuli that comes from skin surface, skeletal muscles, and joints
found in the frontal lobe
Olfactory cortex function:
interprets odor stimuli (smell)
found in temporal lobe
Auditory cortex function:
interprets sound stimuli (hearing)
found in parietal lobe
Taste cortex function:
interprets stimuli from dissolved chemical substances in the oral cavity (taste)
found in occipital lobe
Visual cortex function:
interprets light stimuli (sight)
areas that relate past experiences to current incoming stimuli
Premotor cortex/motor ascending cortex:
found in frontal lobe anterior to primary motor cortex
Premotor cortex function:
coordinates contractions of skeletal muscle groups
found in frontal lobe anterior to premotor cortex
Prefrontal cortex function:
involves emotional responses, judgement and reasoning...the "picking" part of the brain, the logical part
Visual association cortex:
found in occipital lobe
Auditory association cortex:
found in the temporal lobe (singer)
found in parietal and temporal lobes
Wernicke's area function:
involves understanding of written and spoken word
What are basal ganglia?
cerebral or basal nuclei; contain regions of gray matter scattered in white matter of cerebrum
How many basal ganglia?
Where are most basal ganglia found?
in the cerebrum
Basal ganglia main function:
modify motor output from cerebral cortex by inhibition of some nervous stimuli to skeletal muscles
(this allows for the production of fine and even muscular contractions)
Caudate, putamen, and globus pallidus are located where?
in regions of grey matter suspended in white matter of the cerebrum
Substantial nigra and subthalamic nucleus are located where?
in the midbrain
Substantial nigra is associated with?
Subthalamic nucleus is associated with?
a unit by itself, gray matter
inferior to corpus callosum and superior to brainstem (between the two)
made of 20 functional groups of nerve cell bodies
Thalamus function- sensory relay station:
all sensory impulses pass through the thalamus and are directed to the correct portions of the sensory complex EXCEPT olfactory sensory impulses
Thalamus function- gross pain receptor:
perceives general pain and thermal stimuli readily
What is a 3rd function of the thalamus?
modification of sensory input from other brain centers to cerebral nuclei at the cerebellum
Sensory inputs in the thalamus are sent where?
to the motor cortex
Thalamus assists in what?
reticular formation in maintaing consciousness by sending stimuli to reticular formation
inferior to the thalamus
Hypothalamus posterior region connects...
DIRECTLY to the posterior pituitary gland (neurohypophsis)
Hypothalamus- regulation of body temperature:
-region of the hypothalamus that stimulates vasodilation and vasoconstriction in dermal arterioles
-stimulates sweating in skin (too high)
-stimulates shivering in skeletal muscles (too low)
Hypothalamus- regulation water balance:
produces antidiuretic hormone (ADH) that stimulates water reabsorption in the kidneys
Hypothalamus- feeding/satiety center:
-monitors levels of glucose, fatty acids, and amino acids in blood
-stimulates "hunger" feelings before a meal and "full" feelings after a meal
Hypothalamus- produces releasing hormones:
that in turn control secreting activity of the anterior pituitary gland
The hypothalamus affects cardiovascular reactions that are related to what?
gross emotional, fear, anger, and rage responses
Hypothalamus- sexual response center:
related to sensations associated with sexual orgasms
posterior and inferior to the cerebrum
What is the 2nd largest portion of the brain?
How are the cerebellum and cerebrum separated?
by the transverse fissure
What is located in the transverse fissure?
a double layer of meningeal DM called the falx cerebelli
Cerebellum external structure:
two cerebellar hemispheres that are connected by a central structure
What is the central structure between the two cerebellar hemispheres?
Outer surface of cerebellum:
is gray matter; made of small ridges (folia/gyri) and shallow grooves (sulci)
Cerebellum internal structure:
made of white matter or nerve tracts (arbor vitae)
Cerebellum nerve tracts make connections towhat?
the pons, medulla oblongata, midbrain, thalamus, and cerebellum
What does the cerebellum compare?
sensory input from skeletal muscles to motor output from cerebrum
What does the cerebellum modify?
motor output to muscles for maintenance of balance and posture
Types of sensory inputs include:
light, sound, and equilibrium
What does the cerebellum coordinate?
synergistic and antagonistic voluntary muscle contractions for manual dexterity
(putting thread through a needle is an example of precise motor function)
Brainstem is composed of?
midbrain, pons, and medulla oblongata
located posterior and inferior to the thalamus
Cerebral peduncles function:
-send sensory fibers from spinal cord to pons to thalamus
-send motor fibers from cerebrum to pons
Corpora quadrigemina contain:
superior and inferior colliculi
associated with sensory reflexes related to very bright light stimuli (visual reflexes)
associated with sensory reflexes related to very loud sound stimuli (auditory reflexes)
The inferior colliculi provides two levels of protection:
2. inhibition of eardrum movement momentarily
a basal ganglia but NOT located in the cerebrum!!
Describe a substantia nigra:
has a dark pigmented region (melanin)
What does the substantia nigra produce?
a neurotransmitter called dopamine
What does a gradual degeneration of the substantia nigra cause?
What does Parkinson's disease cause?
muscular tremor and muscular rigidity (facial expressions, flailing arms)
Initial treatment for Parkinson's disease?
posterior and inferior to midbrain
What passes through the pons?
nerve tracts (white matter) from the medulla oblongata
What do nerve tracts connect?
-the medulla to the thalamus, cerebellum, and cerebrum
-the motor fibers to the medulla
Ancillary breathing centers:
1. pontine respiratory group (pneumotaxic center)
2. apneustic center
Medulla oblongata location:
posterior and inferior to the pons; terminates at foramen magnum where spinal cord begins
The medulla oblongata is largely composed of what?
What does the medulla oblongata contain?
physiological centers that are diffused regions of gray matter
Physiological centers of medulla oblongata:
1. cardiac center
2. vasomotor center
3. respiratory center
4. coughing, swallowing, and vomitting centers
Cardiac center controls:
Vasomotor center controls:
Respiratory center controls:
The medulla oblongata receives nerve tracts from?
The medulla oblongata transmits nerve tracts to?
the spinal cord
Reticular activating system/reticular formation is a:
diffuse system of neurons and their fibers located throughout the brainstem
Reticular formation function:
sends impulses up to the cerebrum to maintain arousal and consciousness
When impulses are active:
person is awake and conscious
When impulses are inactive:
person is asleep, unconscious, or in a coma
Ventricular system structure:
-ventricles are fluid filled spaces found in all lobes of the cerebral hemispheres EXCEPT the insula
-also located in the brainstem
Where are ventricles found?
in all lobes of the cerebral hemispheres EXCEPT the insula and the brainstem
What is the fluid in ventricles?
cerebrospinal fluid (CSF)
What is another term for 1st and 2nd ventricles?
Where are the 1st and 2nd ventricles located?
one lacted in each cerebral hempisphere
Where is a portion of a ventricle found?
in ALL lobes of a cerebral hemisphere EXCEPT the insula
What is each lateral ventricle connected to?
the 3rd ventricle by a separate foramen of monro
What connects the lateral ventricle to the 3rd ventricle?
a separate foramen of monro
What is another term for the foramen of monro?
the interventricular foramen
What does the foramen of monro connect?
a lateral ventricle to the 3rd ventricle
located below corpus callosum and just above the midbrain
Cerebral aqueduct of slyvius passes through where?
Cerebral aqueduct of slycius connects what?
the 3rd ventricle to the 4th ventricle
4th ventricle location:
posterior to medulla oblongata
4th ventricle function:
exit of fluid from ventricular system to other regions
pons and medulla
The 4th ventricle opens into the ____ ____ of the ____ ____.
central canal, spinal cord
Ventricular system is responsible for the formation and circulation of what?
cerebrospinal fluid (CSF)
group of capillaries covered by ependymal cells found in ALL ventricles
Formation of CSF: blood filters through what?
Formation of CSF: fluid enters ventricles from where?
Formation of CSF: what is the fluid called after it enters ventricles from blood?
cerebrospinal fluid (CSF)
CSF contains very little what?
CSF concentrations of ____ and ____ are not the same as found in ____ ____.
ions, glucose, blood plasma
Why are concentrations of ions and glucose in CSF not the same as found in blood plasma?
because of active transport mechanisms present in ependymal cells of the choroid plexes
Flow of CSF through ventricles begins where?
at the lateral ventricles
What is the flow of CSF through ventricles?
foramina of monro-->
What happens once CSF gets to the 4th ventricle?
fluid must exit the system and get OUTSIDE of the brain/spinal cord
What would happen is CSF did not exit the 4th ventricle?
the brain would enlarge
Where does some of the CSF in 4th ventricle exit?
into the central canal of the spinal cord
CSF in 4th ventricle exits into what?
the subarachnoid space
CSF in the 4th ventricle exits into the subarachnoid space by?
one of three foramina
What are the 3 foramina the 4th ventricles exits from?
-foramen of magendie
-foramina of luschka (2)
What kind of aperture are foramen of magendie?
What kind of aperture are foramina of luschka?
What is the flow of CSF in the subarachnoid space of the spinal cord?
down the posterior side of the spinal cord, laterally and up the anterior side to the brain
What is the flow of CSF in the subarachnoid space of the brain?
1. upward from the base of the brain
2. over the cerebrum and cerebellum, toward the longitudinal fissure
3. arachnoid villi
4. venous sinuses
5. veins found in the meninges
6.internal jugular vein
Where does CSF in the subarachnoid space flow into?
arachnoid villi, venous sinuses, or veins
What are venous sinuses?
spaces filled with blood
Where are the veins that CSF in the subarachnoid space flows to found?
in the meninges
Once the CSF flows into the internal jugular vein, the fluid has...
now been returned to the circulatory system
Properties of CSF:
1. normal volume 90-150 ml
2. clear watery fluid
3. contains less protein, glucose, and K+ than blood plasma
4. contains more Na+ and Cl- than blood plasma
The CSF serves as what for the CNS?
How does the CSF mechanically protect the CNS?
by acting as a shock absorber
The CSF serves as a medium of what?
exchange of nutrients and waste products for nerve cells
How does one obtain a CSF sample?
What can one identify through a lumbar puncture obtaining CSF?
multiple sclerosis, infection, tumors
What is the location and length of the spinal cord?
location and length extends from foramen magnum to L1 vertebra within vertebral canal
What is another name for vertebral canal?
What is the spinal cord covered by?
the 3 meninges
What are the 3 meninges?
meningeal DM, arachnoid, and pia mater
-terminal end of spinal cord
-cone like shape at L1 vertebra
made up of last 10 pairs of spinal nerves
Where does the cauda equine exit the spinal cord?
at the conus medullaris
Some nerves exit the ___ ___ whereas others exit the ___ ___ by ___ ___.
vertebral canal, sacral canal, sacral foramina
thin fine cord of pia mater tissue
Filum terminale location:
extends from the conus to the coccyx to anchor the terminal end of the spinal cord
Spinal cord: cross sectional structure:
-almost divided in half by dorsal median sulcus and ventral median fissure
Another term for dorsal median sulcus?
posterior median sulcus
Another term for ventral median fissure?
anterior median fissure
The cross-sectional structure of the spinal cord is what shape?
Cross sectional structure of spinal cord is almost divided in half by:
dorsal median sulcus and ventral median fissure
How is the cross-sectional structure of the spinal cord arranged?
in an H shape
What does the gray commisure surround?
the central canal
White matter is composed of:
myelinated axons and dendrites
What does the white matter surround?
the gray matter
columns of white matter that run vertically
How are funiculi arranged?
in 3 pairs (anterior, lateral, and posterior)
specialized nerve tracts within a funiculus
sensory impulses to the brain
motor impulses from brain to periphery
Functions of the spinal cord:
1. two way conduction pathway for passage of nerve impulses between the brain and all other body regions
2. acts as a reflex center in association with spinal nerves
The spinal cord is a two way conduction pathway for passage of what?
nerve impulses between the brain and all other body regions
The spinal cords acts as a ___ ___ in association with ____ ____.
reflex center, spinal nerves
How many pairs of cranial nerves are there?
Where do cranial nerves arise/originate from?
the ventral(inferior) side of the brain
In general, cranial nerves supply?
the head, neck, and shoulders
Do cranial nerves arise from the cerebellum?
Cranial nerve fibers are:
either predominantly sensory, predominantly motor, or they can be mixed
-sense of smell
-sense of vision
Optic chiasma location:
on ventral (inferior) side of cerebrum
What converges at the optic chiasma?
both optic nerves
Some nerve fibers of ___ ___ nerve go to the ___ ___ and then enter the ___ ___ on the same side of the brain.
one optic, optic chiasma, optic tract
Other nerve fibers from the same optic nerve go to the optic chiasma BUT?
cross over to the optic tract on the opposite side of the brain!
-supplies extrinsic and intrinsic eye muscles
-supplies extrinsic eye muscles
-sensory: head, neck, teeth and gums
-motor: muscles of mastication and muscles of swallowing
-supplies extrinsic eye muscles
-sensory: taste buds, anterior 2/3 of tongue
-motor: muscles of facial expression, salivary glands, and lacrimal glands
-associated with organ of corti
-detects sound stimuli
-balance and equilibrium
-associated with semicircular ducts, utricle, and saccule
-sensory: taste buds, posterior 1/3 of tongue; sensations from throat and monitors blood pressure
-motor: muscles for swallowing, muscles of vocal cords, secretion of some salivary glands
-sensory: monitors blood pressure sensations form respiratory and digestive tracts to brain
-motor: slows heart rate, stimulates secretion of gastric glands (stomach acid) and pancreas (digestive enzymes); stimulates peristalsis in digestive tract
What is the longest cranial nerve?
Where does the vagus stretch?
into medulla, into neck, into abdomen
Spinal accessory nerve:
-supplies muscles that move head and shoulders
-supplies muscles of tongue for speech and swallowing