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MCAT - Nervous System
CH 13: Nervous System
Terms in this set (99)
Nervous System responsibilities
Sensory experience and perception, higher-level thinking, control of muscular movement and glandular secretions. NS cell is the neuron (differnt types and functions).
What is located in the soma aka cell body?
The nucleus, ER and ribosomes
What part of the neuron is made to receive information?
dendrites petruding from soma
Once the information has been received by the cell body from the dendrites, it is integrated at the ______.
integrated at the axon hillock.
The axon hillock, nerve fiber, provides a connection between the cell body and the axon;
What is Myelin? Myelin is produced by __________ in the central nervous system and by ____________ in the peripheral NS.
Myelin (Scwann cells) covers and helps conduct electrical messages down the axon; also, helps increase speed of conduction much like an insulating wire.
oligodendrocytes, Schwann cells
The small breaks in the myelin sheath of the axon are termed?
nodes of Ranvier
The end of the axon is termed what? Why is this structure enlarged and flatten?
nerve terminal (synaptic bouton); this structure is enlarged and flattened to maximize neurotransmission to the next neuron and ensure propure production of neurotransmitter.
The small space in between the neurons is referred to as?
synaptic cleft or synapse
listen in on signals traveling down axons and relay chemical messages to oligodendrocytes (similar to neurotransmitter); modify the signals neurons send and or receive; the "end-feet" connect to blood vessels in the brain. By signaling blood vessels to expand or narrow, astrocytes regulate local blood flow to provide oxygen and nutrients to neurons in need.
Neurons use all or nothing messages called _______ to relay information to and from the central nervous systems.
What is the resting membrane potential at?
-70mV; voltage potential difference
The inside of the neuron cell is positive or negative relative to the outside?
Inside the cell ___ is high and ____ is low? (resting membrane potential)
K+ is high and Na+ is low (net negative charge); K+ can exit down its concentration gradient but Na+ cannot because it cannot readily enter the cell; Na + builds up on the outside (membrane relatively impermeable to Na+), K+ leaves inside (- comparitively).
For every ___ Na+ the Na+/K+ ATPase moves out of the cell ___ K+ move into the cell.
3 Na+ out (goes against charge gradient and concentration gradient), 2K+ in (goes against concentration gradient); restores this gradient after an action potential (active transport)
For every 3 Na+ transported out of the cell and 2 K+ into the cell how much ATP is used?
Inhibitory inputs cause __________ by making the cell __________ negative.
hyperpolarization; more negative; - ions enter, sent down dendrites of the cell.
______________ is caused by excitatory inputs and makes the cell _________ negative.
depolarization; less negative.
How far must a cell be depolarized to propogate an action potential?
To some threshold value; usually between -55 mV to -40 mV; signals to dendrites are additive to reach threshold (summation).
What ion wants to go inside the cell when an action potential has been generated? Why?
Na+ because it is more negative on the inside
After an action potential has been generated, what moves into the cell and at what voltage does the membrane voltage ion channel close?
Na+ moves into the cell via voltage-gated ion channels due to concentration and charge gradient; channel closes at +35 mV.
After an action potential has started, ______ is transported outside the cell.
K+ ; transported out due to concentration gradient and positive potential created by Na+ influx; channels were triggered by positive potential inside that part of the cell that had an influx of Na+.
The movement of K+ out of the cell after the influx of Na+ is called?
repolarization; restores (-) cell potential, but often over shoots leading to hyperpolarization
What type of refractory period can an action potential not be generated?
What type of refractory period can generate an action potential, but just at a higher amount of excitatory stimulation?
The sodium potassium pump occurs where on the neuron cell? Where does the action potential begin propagation?
There is a wavelike fashion of depolarization down a axon is called ____________.
The sodium channels open causing a _________ and the potassium channels opening will cause a _________
Why doesn't the action potential move backward (back up the axon)?
the region of the axon is refractory immediately after it has fired an action potential
What determines the speed of the action potential?
length and cross sectional area of the axon; physics connection: R = pL/A, ↑L ↑R (resistance), ↑A ↓R
A signal that hops from node to node is termed ______.
saltatory conduction; membrane is only permeable to ions at the nodes of Ranvier.
The connection between two neurons is called a
The neuron using its axon (terminal before the synapse) is called what?
The neuron receiving information through its dendrites is called the?
If a neuron signals to a gland or muscle that cell is termed an?
Most synapses are chemical in nature, they use small molecules referred to __________ to communicate.
Neurotransmitter release is dependent on the _______ ions.
Ca²+ ions entering the terminal due to the presence of an action potential; neurotransmitter vesicles stored in the terminal release their contents via exocytosis.
What determines whether a neuron sends an excitatory message or an inhibitory?
Type of neurotransmitter being released.
What are three ways in which the neurotransmitter can be halted so that the transmission does not continue on forever?
broken down via enzymes, reuptake carriers(recylced) and some may diffuse out of the area.
Afferent neurons carry information from the _______ to the __________.
afferent neurons carry info from the periphery (senses) to the brain or spinal cord; signals accepted.
Efferent neurons carry information from the _______ to the __________.
efferent neurons carry info from the brain or spinal cord to the periphery; signals exit.
The nervous system bundles many axons together into______.
bundles many axons into nerves which may be sensory, motor or mixed.
neuron cell bodies will cluster in the peripheral nervous system into structures called _______.
In the central nervous system cell bodies that cluster are called?
What are neurons that are involved in local circuits?
Nervous System Divisions Chart
There are only two components of the central nervous system?
brain and spinal cord
Brain has folds called _____; unmyelinated parts of the brain are called _______ matter and myelinated parts are called _________ matter.
folds called gyri (incrrease surface area for higher order functioning); gray matter is unmyelinated and white matter is myelinated.
We can divide the brain into what three sections?
forebrain, midbrain and hindbrain.
The telencephalon and the diencephalon are components of the __________; it is the most recently evolved part of the CNS.
A large portion of the telencephalon is the _______ and it can be seperated into the right and left hemisphere.
cerebral cortex; highly convoluted grey matter; responsible for thought, also integrates sensory info and controls movement.
Each hemisphere of the brain can be sectioned off into 4 lobes?
frontal, parietal, occipital, and temporal (FPOT)
What is the large connection btwn the two hemispheres that allow them to communicate?
The diencephalon consists of the _______ and _______.
diencephalon consists of thalamus and hypothalamus
All ascending sensory information is passed through the ________ before being relayed to the cortex.
What purpose does the midbrain serve?
serves as a relay pointy between periphery and forebrain; passes sensory and visual info to forebrain while receiving instructions from the forebrain to be passed to the hindbrain.
The hindbrain is responsible for ________ functions.
involuntary; e.g. respiration
The hindbrain is made up of the _____, _______ and ________ which together are referred to as ________.
cerebellum, pons and medulla
The cerebellum checks ______ for the ________ to make sure it is in agreement with the ______ from the ______.
that the motor signal from cortex to make sure it is in agreement with the sensory signal from the body.
Cerebellum is chiefly responsible for ______, the pons for _____ and the medulla for _______.
cerebellum: coordinates balance and movement.
pons: relays messages between body and the brain.
medulla: breathing, heart rateand blood pressure.
The hindbrain is connected to the other half of the central nervous system the ________.
hindbrain connects to the spinal cord.
What are the division of the spinal cord? Innerviated by? Protected by?
starting at the base of skull down: cervical, thoracic, lumbar and sacral divisions; innerviated by sensory and motory nerves at each vertebrae; protected by vertebral column.
The cell bodies of sensory neurons are termed what? Sensory neurons enter ______ and motor neurons enter _____.
dorsal root ganglion; sensory neurons enter on the back side (dorsally) and motor neurons enter from the front (ventrally).
The somatic nervous system is responsible for ________ movement.
the interface between the neuron and muscle is the ______________; reflexes do not require input or integration from _______ to occur.
neuromuscular junction; do not require input from the brain they are for protection.
The release of what leads to contraction of a muscle?
In monosynaptic reflexes there is a ______ synapse between the sensory neuron that received the information and the motor neuron that responds.
single synapse; e.g. knee jerk; withdrawl reflex involves both mono and poly mono pulls up from dangerous stimulus interneuron takes this info and plants alternate foot down for stability.
Autonomic nervous system is sometimes referred to as the _________ nervous system.
involuntary; requires no conscious control.
Somatic vs. Autonomic NS Diagram
The primary difference between the somatic nervous system and the autonomic nervous system is that the autonomic nervous system is a two neuron system, true or false?
true; in SNS motor neuron goes directly to muscle, in ANS synapses on another neuron along the way.
The first neuron of the ANS is referred to as ________ and the second is referred to as ________
preganglionic neuron, postganglionic neuron
The preganglionic neuron is located where and synapses where?
starts in central nervous system synapses on postganglionic in PNS.
Sympathetic Nervous System vs. Parasympathetic NS
"fight-or-flight" vs "rest-and-digest"
In the sympathetic nervous system, the preganglionic neurons use _________ whereas postganglionic neurons use _________. The parasympathetic uses ______ for both pre and postganglion.
acetylcholine and norepinephrine; acetylcholine only.
The ______ nerve is responsible for many of the parasympathetic effects in the thoracic and abdominal cavities.
vagus nerve and parasympathetic NS
What are the three types of sensory neurons?
interoceptors, proprioceptors and exteroceptors
Interoceptors monitor which type of environment?
internal; exs: monitor blood volume, blood pH and partial pressure of CO₂in blood.
Proprioreceptors are important for our ______ sense.
position; e.g. where we are in the dark.
Exteroreceptors are responsible for monitoring the ______ environment.
external; exs: light, sound, touch, painand temp.
What type of receptors sense pain and relay that info to the brain?
The thick layer that covers our eye is known as the?
The white of our eye is known as the?
What supplies our eyes with nurtrients and oxygen?
choroid which is right underneath the sclera.
The innermost layer of the eye is the _______.
retina contains cells (photoreceptors) that tranduce light into electrical info for brain.
Light first passes through the _______ which does what to the light?
cornea bends and focuses the light.
After moving through the cornea, light moves through the ________.
The muscular pigment _____ can adjust the amount of light entering the eye?
What is the final thing which light passes before the retina receives it?
lens does final focusing; ciliary muscles can adjust how thick lens is (focusing).
Rods are responsible for which type of light?
black and white; respond to low intensity light (useful for night).
cones are responsible for which types of light? Which do people with color blindness lack?
red, blue, green (wavelength absorbed); color blindness lack one are all three.
Rods have only one pigment, which is _________.
rhodopsin; this explains why they only respond to black and white.
After excitation the photoreceptors send a signal to the ______ cells which relay the info to the _______ whose axons bundlle to form the _______.
bipolar; retinal ganglion cells whose axons bundle to form the optic nerve.
ear collects longitudinal sound waves and converts them into electrical signals that the brain can understand.
The sound waves first make their way through the ________ and the ________ which both make up the ________. Next they make their way to the ________ which is the beginning of the ________ which also includes 3 ossicles: ________, _________ and ________.
auricle (pinna) and the auditory canal which both makeup the outer ear Next they make their way to the tympanic membrane which is the beginning of the middle ear which also includes 3 ossicles: malleus, incus and stapes.
Transduction of sound through the ear...
auricle--->auditory canal--->tympanic membrane ---> ossicles (malleus, incus, stapes) ----> oval window ---> fluid filled inner ear ---> depolarizes hair cells of cochlea --->electrical signaldown auditory nerve to brain
3: one on x, y, and z plane; allows us to tell where we are orientated in the world; each canal fluid filled with endolymph; movement puts pressure on hair cell; brain integrates to maintain balance; interprets sudden acceleration and deceleration.
Taste and smell take ______ and turn them into ______ termed _______ and _______.
chemicals and turn them into electrical signals; termed gustation and olfaction
Taste buds (taste pores with microvilli containing receptors) --> interwoven around buds are network of nerve fibers they stimulate -->neurons signal brainstem via 3 cranial nerves --> respond preferentially to one of four stimuli (sweet, salty, sour, bitter) i.e. lower threshold
hairs petrude from olfactory receptors in olfactory membrane ---> form dense mat in upper nasal mucosa-->odor enters--->nasal cavity-->bind to hair--->depolarizes receptor---> axons join to form olfactory nerves --->nerves project into olfactory bulb at brain base
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Parts of the brain and their functions
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