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28 Cards in this Set

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V
what are the steps of depolarization
a. stimulus
b. chemically-gated sodium channels open
c. sodium influx
d. graded depolarization of dendrite or cell body
e. spreads to axon hillock: if threshold reached, voltage-gated sodium channels open
f. sodium influx
g. timed gates on sodium channels close, potassium channels open for repolarization
V
what are the steps of repolarization
a. sodium channels close, gated potassium channels open
b. potassium leaves cell, taking pos. charge
c. potassium continues to leave until RMP is passed (undershoot)
d. gated potassium channels close
e. sodium/potassium pumps return to RMP
V
what is the refractory period
The refractory period is the time during which neuron membrane does not respone normally to additional stimuli
The Absolute Refractory Period is during depolarization and the beginning of repolarization: sodium channels will not open at all.
The Relative Refractory Period is at the end of repolarization and during undershoot: the sodium channels may open if the stimulus is strong enough.
V
What are the two types of impulse conduction
a. Continuous impulse conduction involves passing AP along entire membrane (only unmyelinated fibers)
b. Saltatory impulse conduction involves AP passed from one node of Ranvier to the next (myelinated fibers)
and is much faster than continuous impulse conduction.
V
what are type A fibers and where are they found
Type A fibers have the thickest diameter and thickest myelin sheath. They include somatic motor and some somatic sensory
V
what are types B and C fibers and where are they found
Type B fibers have intermediate diameter and thin myelin sheath. Type C have no myelin sheath and are the smallest. Both types are found in autonomic NS motor fibers to viscera, sensory fibers from viscera, and small somatic fibers from skin
V
How does temperature influence speed of conduction
higher temperatures increase the speed
V
How does pH influence the speed of conduction
decresed pH (<7.35) means depression, increased pH (>7.35) means increased excitability
V
what chemicals depress speed of conduction
alcohol, sedatives, anesthetics
V
what chemicals increase speed of conduction
caffeine, nicotine
V
how do calcium levels influence speed of conduction
low calcium increases excitability, high calcium decreases excitability
V
define NEJ, NMJ, NGJ
a. neuroeffector junction
b. neuromuscular junction
c. neuroglandular junction
V
what are telodendria
terminal branches of the axon, allowing axons to contact more than one cell or one cell in more than one place
V
what is the synaptic cleft
space between presynaptic and postsynaptic neuron
V
describe the events at chemical synapses
a. impulse within presynaptic neuron reaches axon terminal & depolarizes membrane
b. volatage-gated sodium and calcium channels opin in presynaptic membrane and calcium enters
c. the entrance of calcium into presynaptic neuron signals vessicles containing neurotransmitters to fuse with cell membrane, spilling then into synaptic cleft (exocytosis)
d. NT travels across cleft to postsynaptic neuron and binds to receptor sites there
e. ion channels open in postsynaptic neuron allowing ion movement
V
what is acetylcholinesterase (AChE)
acetylcholinesterase is the enzyme in presynaptic neurons that is used to degrade the NT acetylcholine (ACh) after termination of NT effects
V
what are EPSP
excitatory postsynaptic potentials, which depolarize the membrane of the postsynaptic nerve, increasing the likeliness of it reaching threshold
V
what are IPSP
inhibitory postsynaptic potentials, which hyperpolarize the membrane of the postsynaptic neuron and make reaching threshold less likely
V
what is temporal summation
the added effects of a presynaptic nerve firing multiple times over a short period of time, before the previous one fades
V
what is spacial summation
the added effect of more than one presynaptic neuron firing at the same time
V
what are simple series circuits and where are they found
simple series circuits are one presynaptic nerve synapsing with one postsynaptic nerve. They are found in simple reflex arc
V
what are converging circuits and where are they found
converging circuits are several presynaptic axon terminals go to a single postsynaptic neuron. They are found in voluntary vs. subconscious breathing
V
what are diverging circuits and where are they found
one presynaptic neuron acts on several postsynaptic neurons. e.g. motor neuron from brain may go to several meotor neurons in spinal cord
V
what are reverberating circuits and where are they found
chains of neurons with synapses to earlier neurons in the chain. e.g. sleep-wake cycle.
V
what are parallel after-discharge circuits and where are they found
one presynaptic neuron fires to several postsynaptic neurons arranged in parallel that eventually result in a common output. e.g. may be involved in problem solving
VI
what happens in early brain development
a. brain and spinal cord develop from neural ectoderm (outer layer of embryo on dorsal surface)
b. opening of neuroal tube becomes ventricles of brain and central canal of spinal cord
c. later, the tube becomes convoluted and cerebral hemispheres grow up over other structures
VI
what are the four adult brain regions
a. cerebrum
b. diencephalon
c. brain stem
d. cerebellum
VI
what are the regions of the cerebrum
a. cerebral cortex
b. white matter
c. basal nuclei