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120 terms

PCOM: Anatomy 3 - week 2, reader Pg 17 - 29

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characteristics of Group A fibers
largest in diameter, thick myelin sheaths, conduct nerve impulses rapidly
function of Type A fibers
mostly somatic sensory and motor innervating the skin, skeletal muscles and joints
characteristics of Type B fibers
slightly myelinated, intermediate in diameter, conduct much more slowly than Type A, but faster than Type C
characteristics of Type C fibers
unmyelinated and smallest in diameter; conduct impulses slowly
function of Type B and Type C fibers
predominately autonomic , visceral sensory and smaller somatic from skin (pain and light touch)
definition of synapse
the junction between neurons or a neuron and effector organ that allows information in the form of an action potential to be passed along
axodendritic synapse
synapse between the axon of one neuron and the dendrite of another - most common
axosomatic synapse
synapse between the axon of one neuron and the cell body of another
axoaxoninc synapse
synapse between the axon of one neuron and the axon of another - uncommon
term for neurons that transmit action potentials toward the synapse
presynaptic neuron
term for neurons that transmit action potentials away from the synapse
postsynaptic neuron
the 2 types of synapses
electrical and chemical
structure of electrical synapses
consist of gap junctions containing a protein channel (like a bridge) that connect the cytoplasm of neighboring neurons, allowing substances (ions and small molecules) to flow from one neuron to the next
term for the protein channels in the electrical synapses
connexons
mechanism of chemical synapses
no gap junction - communication is via neurotransmitters release from the presynaptic neuron
term for the space between presynaptic and postsynaptic neurons in chemical synapses
synaptic cleft
presynaptic structures of chemical synapses
synaptic vesicles in the knob-like contain 1000's of neurotransmitters
postsynaptic structures of chemical synapses
a protein receptor area on the postsynaptic cell to receive the neurotransmitters
Area separating the presynaptic and postsynaptic neurons
synaptic cleft - filled with interstitial fluid
ion that causes the synaptic vesicles to fuse with the axon membrane and release neurotransmitters
Ca2+
stages of information transfer across the synaptic cleft
1 - Action potential arrives at the axon terminal of the presynaptic neuron
2 - depolarization fo the axon terminal opens Na+ and Ca2+ voltage gates
3 - Ca2+ rushes into the axon terminal
4 - Ca2+ causes the synaptic vesicles to merge withe the axon terminal membrane and release neurotransmitters
5 - neurotransmitters diffuse across the synaptic cleft and bind with receptors on the postsynaptic membrane
6 - binding neurotransmitters open ion channels causing excitatory or inhibitory hyperpolarization graded potentials depending on the neurotransmitter
7 - neurotransmitters are removed from the postsynaptic receptors, usually by enzymes
type of gates neurotransmitter receptors are
chemically gated or ligands
factors influencing the graded potential created on the postsynaptic membrane by neurotransmitters
vary by how much neurotransmitter is released into the synaptic cleft and by how long the neurotransmitters remain on the receptors
term for the accumulation of stimuli creating a graded potential
summate
two types of summation
temporal and spatial
temporal summation
strength of the graded potential increases (greater depolarization) due to repeated neurotransmitter stimulus within a relatively short timeframe
spatial summation
strength of the graded potential increases due to 2 or more simultaneous neurotransmitter stimuli at different locations on the postsynaptic membrane
term for excitatory potentials created on the postsynaptic membrane by certain neurotransmitters
excitatory postsynaptic potential (EPSP)
function of the EPSP
to create and action potential at the axon hillock of the postsynaptic neuron by creating ionic currents along the dendrite which, if strong enough, depolarize the axon hillock and open Na+ voltage gated channels
term for inhibitory potentials created on the postsynaptic membrane by certain neurotransmitters
inhibitory postsynaptic potential (IPSP)
function of the IPSP
hyperpolarization of the postsynaptic membrane by the opening of K+ influx or Cl- efflux ligands by specific neurotransmitters, but not affecting Na+ channels
Types of neurotransmitters
Acetylcholine, biogenic amines, amino acids, peptides, purines, gases
term for the synapse between motor neurons and the skeletal muscle
neuromuscular junction
neurotransmitter released at the neuromuscular junction
Ach - Acetylcholine
abbreviation for acetylcholine receptors
AchR
name of the enzyme that breaks down Ach
acetylcholinesterase - ACHE
two types of biogenic amines
catecholamines and indolamines
the three catecholamines
epinephrine, norepinephrine, dopamine
two types of indolamines
seratonin and histamine
amino acid used in the synthesis of dopamine and norepinephrine
tyrosine
amino acid used in the synthesis of seratonin
tryptophan
two key types of peptides
substance P and endorphins
function of substance P
to mediate pain signals
function of endorphins
natural opiates which reduce pain
function of purines
ATP - can trigger fast or slow excitatory response dependent on the ATP receptor
component of ATP that acts as a potent inhibitor
adenosine - blocked by caffeine, creating a stimulatory effect
main gas neurotransmitter
nitric oxide
function of nitric oxide as a neurotransmitter
short-lived, not stored in vesicles which participate in a variety of brain processes
classifications of neurotransmitters
excitatory, inhibitory or both
what determines the function of neurotransmitters
the receptor on the postsynaptic membrane to which they bind
two ways neurotransmitters act on the postsynaptic neuron
directly and indirectly
how neurotransmitters work directly
open ion channels
how neurotransmitters work indirectly
via a 2nd messenger chemical which influences ion channels, activate enzymes or activates genes
two key types of 2nd messenger molecules
cyclic AMP and Ca2+
embryonic layer ultimately giving rise to the CNS
ectoderm
differentiation of the ectoderm in the embryo at 2 weeks
forms the neural plate which invaginates, forming the neural groove
progression of the embryonic neural groove from week 2 to week 4
fuses at the superior edges forming the neural tube which then descends to a deeper position
structure that becomes the CNS
the neural tube
portion of the neural tube that becomes the three primary brain vesicles
the anterior portion of the neural tube
how the brain vesicles form
the anterior neural tube expands and constricts in three places, forming the three vesicles
the three primary brain vesicles
prosencephalon (forebrain), mesencephalon (hindbrain), and rhombencephalon (midbrain)
what the posterior neural tube forms
the spinal cord
what occurs in the formation of the CNS in week 5 of development
the 3 primary vesicles give rise to the 5 secondary vesicles
the 5 secondary vesicles
telencephalon, diencephalon, metencephalon, myelencephalon, mesencephalon
secondary vesicles arising from the forebrain
telencephalon and diencephalon
secondary vesicles arising from the hindbrain
metencephalon and myelencephalon
structures in the adult brain arising from the telencephalon
cerebrum: cerebral hemispheres (cortex, white matter, basal nuclei)
structures in the adult brain arising from the diencephalon
thalamus, hypothalamus, epithalamus, retina
structures in the adult brain arising from the metencephalon
brainstem: pons and cerebellum
structures arising from the myelencephalon
brainstem: medulla oblongata
structures arising from the mesencephalon
brainstem: midbrain
structures of the brainstem, superior to inferior
midbrain, pons, medulla oblongata
what happens as the cerebral hemisphere continues to grow and form
due to restricted space in the skull cavity, the cerebral hemispheres mushroom out and grow over the diencephalon and midbrain and fold and creases appear, forming greater surface area in the brain
what the lumen of the neural tube forms
the 4 ventricles
subdivisions of the adult brain
cerebral hemispheres, diencephalon, brainstem, cerebellum
grey matter of the CNS
neuron cell bodies and unmyelinated axons
white matter of the CNS
myelinated axon tracts
characteristics of the structure of the 4 ventricle
continuous with each other and the central canal of the spinal cord
what filles the ventricles
cerebrospinal fluid
what lines the ventricles
ependymal cells
ventricles of the cerebral hemispheres
paired lateral ventricles - one in each hemisphere
ventricle of the diencephalon and its characteristics
the 3rd ventricle which is continuous with the lateral ventricles
the channel that connects the lateral and 3rd ventricles
intraventricular foramen or Foramen of Monroe
ventricle of the brainstem and it characteristics
the 4th ventricle which is continuous with the 3rd ventricle and has 3 openings in its walls
the openings of the 4th ventricle's walls
paired lateral apertures on its sides and the median aperture on its roof
the canal that connects the 3rd and 4th ventricles
the cerebral aqueduct
with what the 4th ventricle is continuous
the central canal of the spinal cord
significance of the apertures of the 4th ventricle
open to the CSF filled subarachnoid space surrounding the brain and spinal cord
name for the elevated ridges of the cerebral hemisphere
gyri
name of the grooves between the ridges of the cerebral hemisphere
sulci
the deeper grooves of the brain separating large areas of the brain
fissures
fissure separating the cerebral hemispheres
longitudinal fissure
fissure separating the cerebral hemispheres from the cerebellum
transverse fissure
5 lobes of the cerebral hemispheres
frontal, parietal, occipital, temporal, insula
sulcus separating the frontal lobe from the parietal lobe and its orientation
the central sulcus is located on the coronal plane
name of the gyri on either side of the central sulcus
the pre-central and post-central gyrus
name of the sulcus separating the temporal and parietal lobes
lateral sulcus
lobe of the cerebral hemisphere that lies deep to the lateral sulcus and the temporal, parietal and frontal lones
insula
regions of the cerebral hemisphere
cortex, white matter, basal nuclei
structure of the cortex
gray matter - groups of nerve cell bodies, dendrites, neuroglia and blood vessels
structure of the white matter
myelinated axons
structure of the basal nuclei
gray matter - groups of nerve cell bodies within the cerebrum
functions of the cerebral cortex
conscious mind, perception of sensations, communications and muscles activity, memory, awareness of surroundings
three functional areas of the cerebral cortex
motor, sensory, association
types of neurons in the cerebral cortex
interneurons
characteristic of sensory and motor control of the cerebral hemispheres
contralateral - controls the opposite side of the body
characteristic of the integration of the different areas of the cerebral cortex
all areas work together in conscious behavior - no area acts alone and the entire cortex is involved
characteristic of the functions of the hemispheres
lateralization - each hemisphere has unique functions and abilities
location of the motor area of the cerebral cortex
posterior part of the frontal lobes
location of the primary motor cortex
the precentral gyrus of the frontal lobes of each hemisphere
neurons of the precentral gyrus responsible for voluntary movement of skeletal muscles
pyramidal cells
structures and locations of the axons of the pyramidal cells
form pyramidal or corticospinal tracts which are located throughout the spinal cord
structure that forms in the primary motor cortex representing the different areas of the entire body
motor homunculus
characteristic of motor innervation of the primary motor gyrus
contralateral - controls the opposite side of the body
location of the premotor cortex
anterior to the precentral gyrus
functions of the premotor cortex
controls learned motor skills or a repeated or patterned nature, influences the primary motor cortex and motor activity and supplies about 15% of the corticospinal tracts
location of Broca's Area
anterior to the inferior region of the premotor cortex and usually only in one hemisphere - usually the left
function of Broca's Area
muscular/motor function of speech; becomes active when preparing to speak or in the planning many voluntary motor activities
location of the frontal eye field
partially anterior to the Premotor cortex and superior to Broca' Area
function of the frontal eye field
voluntary movement of the eyes