Final Review Flashcards
what are NTs of the AVS
acetycholine (efferent)
glutamate aspartate - excite AVS
gaba glycine - inhibit in AVS
what is a NT of the neuromuscular
acetycholine
Explain the process of stimulus all the way to synapsing of neurons
Neuron is sitting at resting membrane potential with all ion channels closed and inner voltage resting at -70 mV.
Outside trigger (like a spider brushing up against a knee, or a finger touching the hand) causes the mechanically gated ion channels (sodium channel) to open and sodium rushes in the membrane causing the cell to become depolarized
RP stays local where the stimulus was
RP are graded (amplitude modulated) signals with the amount of depolarization representing the strength of the signal.
Stimulus is strong enough to cause a threshold reach of the RP (about -55 mV)
AP (all or none, NO degradation, forward propagating, saltatory conduction)
at the axon hillock, Voltage-gated ion channels open at the first node of Ranvier and sodium rushes in, depolarizing that spot. Then the next (forward) node is stimulated and sodium rushes in so the AP propagates forward by saltatory conduction.
AP propagates down a neuron, activating sodium and potassium channels in a wave, it eventually reaches the presynaptic terminal
Reaching this terminal activates the voltage-gated calcium channels (Ca2+) to open and release calcium into the neuron’s cytoplasm (inside terminal bouton)
The flow of positively charged calcium ions causes the tiny synaptic vesicles (w/ NT) to fuse with the cell membrane and release those chemical messengers
these NT’s diffuse across the synaptic gap and bind to receptor sites on the postsynaptic neuron
Depending which NT binds to which receptor, the post neuron can either be excited or inhibited
correct order that they would occur during sensory transduction for a receptor in the skin and neuron of the ascending sensory pathway
Cell is at rest with a resting membrane potential of -65mV
2. Stimulus triggers a receptor potential
3. depolarization during the receptor potential initiates the action potential
4. Action potential reaches the terminal bouton and triggers synaptic transmission.
5. neurotransmitter is released into the synaptic cleft
purpose of the sodium potassium pump
for every two potassium ions that come in from the extracellular fluid ot the cytoplasm inside the membrane (pumps in), 3 sodium ions are pumped out
what cells create myelin in PNS & CNS
PNS - schwann cells, one axon per cell
CNS - oligodendrocytes, many axons
How does an AP encode intensity of a stimulus?
frequency modulation
a weak stimulus tends to trigger less frequency AP’s (like picking up an egg)
an intense stimulus increases the frequency of APs (like crushing a can)
explain 4 things of an AP
all or none, NO degradation, forward propagating, saltatory conduction)
Action potentials can be conducted along neurons quickly due the presence of myelin and saltatory conduction.
The AP can carry information over relatively long distances without degrading (without getting weaker) so it does not degenerate or lose information on its way to or from the brain
an action potential is all or none
Action potentials carry information about the stimulus as a frequency modulated signal with faster firing rates for stronger stimuli.
period when it cannot respond to any other stimulus no matter how strong (helps prevent signals from traveling in both directions down the axon at once)
absolute refractory period
where is A1
A1 is located on the transverse gyri of the superior temporal gyrus of the temporal lobe, inside the lateral fissure.
Describe Spiral ganglia and Scarpa’s ganglia
Scarpa’s -
The cell bodies of the bipolar afferent vestibular CN VIII fibers located in the internal auditory canal
Spiral ganglia - cochlea nuclei
what does ectoderm form
outer ear (skin) and inner ear (sense organs), membranous labyrinth
what does mesoderm form
ossicles, temporal bone and bony labyrinth
what does endoderm form
middle ear epithelial lining, aerated mastoid cavities, & ET
first sign outside of embryo that inner ear is forming?
otic cyst that invaginated from ectoderm and became inner ear
all 3 germ layers contribute
ME cavity - primordial structure that becomes middle ear
tubotympanic recess - tubo becomes ET, tympanic is the middle ear cavity
Which arches contribute to Ossicles?
1&2
how is outer ear/pinna formed
6 hillocks at 6 weeks that form this shape
how is the canal formed
form bw 1 & 2 arches
only opens later in development because it has meatal plug
how does the TM develop its 3 layers
from all 3 germ layers
ecto outside, meso in middle, endo in middle ear
During embryologic development, six hillocks of tissue form around both sides of the first branchial groove. What do these hillocks eventually become?
pinna of external ear
During embryological development of the central nervous system, which secondary vesicle of the neural tube becomes the pons, cerebellum and a portion of the fourth ventricle?
metencephalon
Which branchial arches play a major role in development of ear structures?
1&2
Embryologically, the central nervous system (including the brain and spinal cord), sense organs such as the cochlear and vestibular hair cells, and the skin are derived from which of the germ layers?
ectoderm