Section2.Neuromscular physiology and special senses Flashcards
(181 cards)
1
Q
Voltage gated channels
A
the molecular conformation of the gate responds to the electrical potential across the cell membrane
2
Q
Chemical gated channels
A
the binding of another molecule with protein receptors on the membrane causes a conformational change in the protein molecule that opens or closes the gate
3
Q
Voltage gating is involved in
A
action potential propagation along the axons of nerves
4
Q
Chemical gating is involved in
A
transmission of signals from one nerve cell to another, and from nerve cells to muscle cells
5
Q
What are examples of physiologic stimuli for certain excitable cells?
A
hormonal (epi acting on adrenergic receptors)
thermal (skin temp receptors)
mechanical (displacement of outer lamellae of pacinian corpuscles or auditory hair cells)
electromagnetic radiation (retinal rods)
chemical (protons and salts acting on gutatory receptors of the tongue)
6
Q
What does the Gibbs Donnan equation show?
A
a higher concentration of a nondiffusible ion on one side of a membrane, the destruction of other more permeable ions ins predictably affected
7
Q
The Gibbs-Donnan effect on the distribution of ions across the capillary endothelium is important because of
A
In plasma has a larger concentration of nondiffusible protein anions that is normally found in interstitial fluid
8
Q
Gibbs-Donnan forces in the glomerulus of the kidney
A
cause a nonlinear increase in the colloid osmotic pressure of plasma, thus limiting the degree of filtration
9
Q
Gibbs Donnan forces in the gallbladder normally result in an increase in the concentration of:
A
Ca, K , Na (increase)
Cl and Bicarb (decrease)
10
Q
What is the equilibrium (or Nernst) potential (E) for a diffusible ion?
A
the electrical potential necessary to balance its concentration gradient across the membrane
at its equilibrium potential an ion diffuses at an equal rate in either direction
11
Q
Which electrolyte has the highest membrane conductance in the resting state?
A
K
12
Q
What is the primary difference between the Nernst equation and the Goldman-Hodgkin-Katz (GHK) equation is that the
A
GHK equation considers ion conductance as well as concentration differences across cell membranes
13
Q
The Na/K pump is on all cell membranes of the body actively extruding Na in exchange for K
A
This pump is not equal since its pumps 3 Na ions to the outside for each 2 ions it brings to the inside of the cells
14
Q
How does Na/K pump perform its action?
A
uses energy form the terminal phosphate ester bond of ATP to actively transport these ions
15
Q
capacitance
A
membranes ability to store or separate a small amount of charge across it surface
16
Q
Resting conditions of a nerve cell are maintained by:
A
-the concentration gradients of the permeant ions
-the electrical gradients of the permeant ions
-selective membrane permeability
-active transport
17
Q
The speed of electrotonic conduction along a nerve fiber is primarily determined by the:
A
combined effect of membrane capacitance and the electrical resistance to the flow of current
18
Q
In relation to nerve fiber size and conduction velocity, as what does the effect of larger/smaller fiber size?
A
larger fibers have faster conduction velocities
19
Q
What is the effect of myelination on conduction velocity?
A
myelination r (m) and decreases c (m), thereby increasing conduction velocity
20
Q
What is the Hodgkin cycle?
A
positive feedback cycle of Na influx depolarizing the cell and promoting the opening of more Na gates is the source of the regenerative current responsible for the depolarization phase of the action potential
21
Q
Na (and K) channels are most concentrated in which part of the myelinated neuron?
A
Nodes of Ranvier
22
Q
What are nodes of Ranvier?
A
sites where nerve impulses are generated during saltatory conduction in a myelinated neuron, thus allowing for a more rapid spread of the depolarizing current
23
Q
A property of mixed nerves have what kind of action potential?
A
Multipeaked (or compound) action potentials
**compound action potentials occur b/c the nerve contains different fibers with varying speeds of conduction
24
Q
What is the absolute refractory period?
A
The nerve cell membrane is completely refractory to further stimulation, meaning that no matter how strong a second stimulus might be, it neither influences the existing action potential nor causes another
25
What is the relative refractory period?
period following repolarization, the nerve cell becomes capable of firing a second action potential, yet a stronger than normal stimulus is required and
26
The relative refractory period is due to what electrolytes?
is due to the high K conductance occurring during this time
27
70% of the energy used by a nerve goes toward which function?
maintaining the polarity of its membrane through the action of Na/K Atpase
28
For a short period of time following the spike of an action potential, the membrane becomes
even more negative than the original resting potential
**called the undershoot**
29
What is the overshoot period?
period during depolarization when the membrane potential spikes and normally overshoots zero mV to approximately +35 mV
30
Define orthodromic conduction
an impulse passing along an axon from cell body to the nerve terminal
**normal in mammals
31
define antidromic conduction
moving toward the cell body
**rarely occurs
32
Chemical synapses
an action potential causes a neurotransmitter to be released from presynaptic neuron, which diffuses across the synaptic space to bind with receptors on the postsynaptic membrane, thus causing a change in its electrical properties
33
Which type of synapse has displays a synaptic delay?
Chemical synapses
34
An endplate potential or synaptic potential is transient because
action of acetylcholine is ended by its hydrolysis to choline and acetyl-CoA by the enzyme acetylcholinesterase , which is prevalent in the extracellular space (cleft) between nerve and muscle cells
35
What are miniature endplate potentials?
due to the spontaneous and random releases of ACh from pre-synpatic nerve terminals at the skeletal neuromuscular junction
36
Patients with Myasthenia gravis, end plate potentials is related to
reduced numbers of ACh receptors on the post-synaptic membrane of skeletal muscle fibers that is most likely due to autoimmune destruction
37
Why do treatments, such as neostigmine, physostigmine or diisopropyl fluorophosphate work in the treatment of Myasthenia gravis?
inhibit the action of AchEase on the post-synaptic membrane makes ACh more available to bind with post-synaptic receptors and thus partially compensates for the reduced number
38
What is the most prevalent inhibitory amino acid neurotransmitter in the brain?
GABA
39
What are the most prevalent excitatory neurotransmitters in the brain?
Glutamate and Aspartate
40
Which neurotransmitters are thought to undergo reuptake intact into the neuron that secretes them?
-norepinephrine
-serotonin
-GABA
-glutamate
**acetylcholine does not**
41
What is spatial summation?
two EPSPs are additive, while one IPSP is capable of canceling one EPSP
42
What is temporal summation?
when two or more action potentials in a single pre-synaptic neuron are fired in rapid succession, thus allowing the resulting postsynaptic potential to overlap in time
43
define augmentation
pertains to the enhancement of synaptic efficacy that occurs intermediately between facilitation and posttetanic potentiation
44
define posttetanic potentiation
may occur for several seconds after a presynaptic neuron is sitmulated tetanically
45
define facilitation
When a presynaptic axon is fired repeatedly, the postsynaptic response may grow with each stimulus
46
Muscarinic, M1 receptors are found where
in the brain
47
Muscarinic, M2 receptors are found where
smooth and cardiac muscle
48
Muscarinic, M4 receptors are found where
pancreatic acinar and islet tissue and smooth mm
49
Muscarinic M1, M4 and M5 receptors function through what second messenger system?
through IP3 (and thus Ca) and diacylglycerol
50
Muscarinic, M2 and M3 receptors function through what second messenger system?
through cyclic-AMP mediated pathways
51
What are distinguishing characteristics of Type I skeletal mm fibers?
**slow-twitch, oxidative aerobic fibers
-longer contraction times
-more myoglobin
-many mitochondria (therefore fewer contractile elements)
-less glycogen
-more lipid
-less blood flow
-less well-developed sarcotubular system
-greater resistance to fatigue
-slower rate of Ca uptake and release
52
Type I vs Type II skeletal muscle fibers are used for what kinds of exercise?
Type I: aerobic fibers, used for sustained exertion
Type II: anaerobic fibers, more useful during short periods of heavy lifting
53
Thick filaments of vertebrate skeletal and cardiac mm are largely composed of
Myosin
54
Myofibrils make up what percentage of skeletal muscle vs cardiac muscle?
skeletal mm= 80 to 87% of cell interior is myofibrils
cardiac mm= 50% of cell interior is myofibrils
55
Describe Thin myofibrillar filaments
-6-8 nm
-anchored at one of the Z-disk and interdigitate between thick filaments at the other end
-contain all the actin the myofibril
56
Describe thick myofibrillar filaments
-14-16 nm
-contain protrusions or cross-bridges that extend outward from their surfaces at regular intervals
-contain all the myosin in the myofibril
57
What proteins make up thick filaments
95% myosin
5% C-protein
58
what proteins make up thin filaments?
actin
Beta-actinin
tropomyosin
-3 forms of troponin (TnT, TnI, TnC)
59
What protein makes up the darkly staining amorphous part of the Z-disk?
alpha-Aactinin
60
Describe what phase or twitch fibers are
a propagated action potential and twitch response following nerve stimulation
--fast contraction times
61
Describe what slow or tonic fibers are
muscle fibers respond to nerve stimulation with a prolonged contracture and usually exhibit no propagated action potential
62
Tonic muscle fibers are usually innervated in what format?
En grappe type of innervation
63
Phasic fibers are generally innervated in what format?
En plaque type of innervation
by a single, relatively large motor neuron (or infrequently by two motor neurons) that impinges on cells at a small, discrete area on the sarcolemmal surface (known as the motor-end plate)
64
What is the difference between phasic muscle fibers and tonic muscle fibers, when acetylcholine is applied?
tonic: ACh elicits contraction when applied at several different a locations along the surface of the mm cell
phasic: ACh is applied tat the proper receptor held location will cause contraction
65
A majority of mammalian skeletal muscle fibers are of what kind?
phasic or fast type
66
Define excitation-contraction coupling
mechanism by which the action potential, passing along the plasmalemma and T-tubules, eventually initiates contraction
67
T-tubules function
conduct a signal from a nerve impulse to the interior of the skeletal mm or cardiac mm cell
68
What are the two sets of tubules within skeletal mm cells?
T-system: transverse sys
L-system: longitudinal sys
69
L system of t-tubules is also called the
sarcoplasmic reticulum
70
invaginations of the sarcolemma forms which skeletal muscle tubules?
T-tubules
71
T tubules run what direction in respect to the long axis of skeletal and cardiac muscle cells?
perpendicular
72
T-tubules occur at regular intervals along the length of the muscle cell, what is the difference between cardiac mm and skeletal mm?
cardiac mm: they are found at level of every Z-disk-- one tubule for every sarcomere
skeletal mm: T tubules are at every level of A-I junction; two tubules for every sarcomere
73
Ca-ATPase within the muscle cell sarcoplasmic reticulum function
keeps the cytplasmic Ca concentration in resting muscle cells at a low level
74
What is the voltage sensor in skeletal muscle responsible for initiating the contraction process is the:
Dihydropyridine receptor
75
What occurs after a T-tubule is depolarized, in a skeletal mm fiber
the DHP voltage sensor pulls a foot process away from a ryanodine Ca release channel in the sarcoplasmic reticulum and release Ca form the Sr is then available to initiate contraction
76
The binding of calcium to troponin C (TnC) causes
Troponin I (TnI) to loose its affinity for actin/
77
After troponin I looses its affinity for actin, what occurs to the troponin-tropomyosin complex?
The troponin-tropomyosin complex moves laterally into the groove between actin strands, thus uncovering the active sites on actin and myosin
**cross bridge closes and contraction begins
78
What occurs when there is no ATP available to dissociate the actin-myosin complex?
The thick and thin filaments cannot be separated and rigor mortis ensues
79
When does relaxation of mm occur?
When calcium is removed from the cytoplasm by Ca pumps located on the sarcoplasmic reticulum
80
What occurs when intracellular Ca concentration falls in skeletal mm cells?
troponin returns to its original conformational state, tropomyosin inhibition of myosin-actin interaction is restored and cross bridge cycling stops
81
In regards to skeletal mm, hypermagnesemia is associated with
a decrease in neuromuscular irritability
82
Muscle fatigue is most likely caused by:
H
**when lactic acid dissociates
83
Ca release from teh sarcoplasmic reticulum of cardiac mm is done through
the ryanodine receptor (or channel)
84
What is the difference between cardiac mm and skeletal mm during exercise?
cardiac muscle removes lactate from blood and utilizes it for energy
85
Because cardiac cells rely heavily on aerobic metabolism, cardiac muscle cells contains
many mitochondria and a lot of myoglobin
86
What are intercalated disks of cardiac muscle?
occur at the Z lines of cardiac mm, are areas where the end of one muscle fiber abuts another
**as does the T-tubular system of cardiac mm
87
Function of intercalated disks of cardiac mm
strong attachment between fibers at the intercalated disks maintains cell to cell adhesion necessary for individual units pulling each other along during contraction
88
What are the low-resistance bridges for the spread of excitation from one cardiac mm fiber to the next known as
**also make it unnecessary for each muscle fiber to be innervated
gap junctions
89
Unlike skeletal mm, cardiac mm is resistant to
tetany-- because it is generally refractory to repeated stimuli
90
Teh positive inotropic effet of catecholamines is mediated through what receptors?
b1 adrenergic receptors and intracellulary by cyclic-AMP
91
Digitalis glycosides inhibit what in the cell membranes of cardiac mm fibers?
Na/K ATPase, which makes it more difficult for Na to leave--> this reduces Na influx and Ca efflux by the Na/Ca antiporter in plasma membranes--> the strength of contraction decreases
92
What are characteristics of multi-unit smooth muscle?
-discrete fibers that operate independently of each other
-each innervated by a single neuron
-contraction is mainly controlled by neural rather than non-neural stimuli
-innervated by autonomic nerve fibers
93
Unitary smooth muscle characterstics
-aggregated into sheets and cell membranes are adherent to each other at multiple oints
-gap junctions can spread action potentials from one cell to the next
-force generation in one fiber can be trnasmitted to the next
94
walls of most hollow viscera, or organs of the body, including the gut, bile ducts, ureters, uterus and many blood vessels are examples of what kind of muscle?
unitary smooth muscle
95
What are caveolae of smooth mm?
-small invagination of the surface membrane that serve to increase smooth muscle surface area
- function to couple membrane potential changes to the smooth reticulum
96
Excitation-contraction coupling of smooth muscle is thought to be regulated by:
Ca-induced phosphorylation of myosin
97
What are ways that calcium can enter the smooth mm cells?
1. extracellular fluid following stimulation by a neurotransmitter, opens receptor activated Ca channels in the sarcolemma
2. from ECF via voltage-activated Ca channels during the smooth muscle action potential
3. from SR via IP3 activation
98
Vascular endothelial cells are thought to produce vasoactive substances that act locally upon vascular smooth muscle. Which compound is thought to be produced by vascular endothelial cells, and relaxes vascular smooth muscle?
Nitric oxide
99
What is the primary function of the autonomic nervous system?
control the immediate, dynamic process of tissues glands and organs it innervates
**vs long term physiological processes controlled by endocrine system
100
The classical efferent visceral component of the ANS, is subdivided into both anatomically and physiologically into
parasympathetic and sympathetic divisions
101
Both sympathetic and parasympathetic divisions contain two neuron pathways with cell bodies of preganglionic neurons located where?
within the CNS ( spinal cord or motor nuclei of cranial nerves)
102
The parasympathetic nervous system primary contains which fibers?
cholinergic (both pre and postganglionci fibers)
103
Preganglionic neurons fo the PNS are associated with what cranial nerves?
III: oculomotor
VII: facial
IX: glossopharyngeal
X: vagus
* as well as sacral regions of the spinal cord
104
Stimulation of the sympathetic nervous system results in what fight or flight responses?
INC heart rate
bronchial dilatation
INC blood pressure
INC blood glucose (dec in insulin secretion)
piloerection
sweating
dilation of the pupil
Etc.
105
Which division of the ANS exerts the greatest influence on heart rate during the resting state?
The parasympathetic division, because if you cut both vagal and sympathetic fibers to the SA node, heart rate increases
106
In comparison, norepinephine spreads further/ closer and has short duration or prolonged action than acetylcholine?
Norepinephrine spreads farther and has a more prolonged action than acetylcholine
107
Where does the majority of norepinephrine diffuse into blood from?
from noradrenergic (sympathetic) nerve endings
108
Acetylcholinesterase at cholinergic nerve endings functionsin
hydrolyzes excess acetylcholine
into choline and acetate
109
Does re-uptake of acetylcholine occur at nerve terminals?
No-- rather 50% of ahline produced as a result of acetylcholien hydrolysis is activelyt aken up and used in teh resynthesis of new trnasmitter
110
Which enzyme catalyzes the hydrolysis of acetylcholine?
choline acetylase-- substrates being choline and active acetate
111
Parasympathetic, postganglionic neuroeffector sites are
Muscarinic
112
synapses at ganglion cells of the entire autonomic nervous system, as well as somatic myoneural junctions are:
nicotinic
113
The muscarinic vs the nicotinic receptors are blocked by which drugs (that differentiates them)?
Muscarinic blocked by atropine
Nicotinic blocked by nicotine, bis quaternary compounds or curare
114
Anticholinesterases have what effect on ehart rate?
decrease heart rate
-- because they prolonged the effect of AcH
115
Anticholinesterase drugs are used to treat what disease?
myaasthenia gravis-- an autoimmunse disease with circulating antibodies ot nicotinic recpetors
116
What is the rate-limiting enzyme in catecholamine biosynthesis?
tyrosine hydroxylase
117
Where are these catecholamines primarily produced:
norepinephrine
epinephrine
dopamine
NE: adrenergic nerve cells in ANS
Epi: chromaffin cells in adrenal medulla
Dopamine: primary adrenergic activity in the CNS
118
What are degradative enzymes that convert catecholamines into inactive compounds?
monoamine oxidase
catecholamine-O-mmethyltransferase
119
Glucocorticoids enhance adrenal epinephrine synthesis by activating which enzyme?
phenylethanolamine-N-methyltransferase
120
Where is epinephrine formed?
in the adrenal medulla from NE, by action of phenylethanolamine-N-methyltransferase
121
Regarding re-uptake of norepinephrine (or its degradative product) at the adrenergic nerve terminal-- what occurs?
approx 80% of the NE is taken back in the nerve terminal intact, where it can be resecreted, stored or degraded by the intracellular mitochondrial enzyme, monamine oxidase
122
monoamine oxidase is a degradative enzyme located where?
within mitochondria
123
measurement of which of the following compounds in urine would be the best index of the rate of adrenal catecholamine secretion?
metanephrines and vanillylmandelic acid
**breakdown products of Epi/NE/dopamine
124
What does beta adrenergic receptor activity involve?
stimulation of adenyl cyclase, leading to an increase in intracellular cyclic-AMP
125
What does alpha receptor activity involve?
increase in membrane permeability to Ca, with a consequent elevation in the cytoplasmic Ca concentration (through alpha 1 receptor stim) or to decrease activity of adenyl cyclase through alpha 2 receptor stim
126
all pre-synaptic alpha-adrenergic receptors are thought to be of whcih variety?
alpha 2
127
Post-synpatic receptors appear to be of what alpha-adrenergic receptor?
alpha 1 (a few of alpha 2s)
128
Presynpatic alpha 2 adrenergic recpetor are response for
reducing transmitter release in response to neural stimulation
may act by either dec adenyl cyclase activity or by restricting Ca entry into the nerve terminal
129
Postsynaptic alpha 2 receptor stimulation leads to
increase in Ca influx that is largely independent of the c-AMP messenger system
130
While there is evidence for presynaptic inhibition of norepinephrine release via (blank) and (blank) adrenergic receptors, there is also evidence for presyaptic enhancement of transmitter release via (blank) and blank)- adrenergic receptors
alpha 2 and muscarinic
beta 2 and angiotensin II
131
sensitive D1 receptors for dopamine act by
enhancing intracellular activity of adenyl cyclase
132
sensitive D2 receptors for dopamine act by
reducing intracellular activity of adenyl cyclase
133
dopamine inactivation requires
DOPA hydroxylase
134
Synaptic dopamine can be recaptures via
an active re-uptake mechanism similar to that described for NE
135
Beta 1 adrenergic receptors are found
in heart, on fat cells and on juxtaglomerular cells of the kidney
136
stimulation of beta2 receptors casues
vasodilation in pulmonary coronary, skeletal and visceral circulation and relaxation of bronchiolar smooth mm
137
where are allpha 1 adrenergic receptors found
on radial smooth mm of iris and sitmulated cause mydriasis
138
atropine blocks
muscarinic receptors
139
isoproterenol stimulates
beta-adrenergic receptors
140
What occurs when norepinephrine is infused slowly into normal, resting subjects?
-systolic and diastolic blood pressures rise
-total peripheral resistance increases from vasoconstriction in most, if not all organs (alpha 1 receptor stim)
-plasma glucose concentration rises bc of sitm of hepatic glycogenlysis (alpha and beta stim)
141
In the heart, what is the effect of NE and epi?
increase the contractile force of the heart, bediated by ebta1 adrenergic receptors
142
Different from norepinephrine, epinphrine causes
dilates blood vessels in skeletal mm and liver via beta 2 receptor stim
143
Why does epinephrine cause a widening of the pulse pressure?
b/c of an increased systolic and decreased diastolic pressure (cardiac rate and output increase)
144
Sympathetic innervation may provide reciprocal innervation t through:
alpha: generally stimulatory
beta: generally inhibitory
145
Which adrenergic receptors are on coronary blood vessels
adrenergic: alpha1, beta2
cholinergic: ach
146
Erection is a (parasymp/sympath)response and ejaculation is a (blank)response?
erection is a parasympathetic response, ejculation is an alpha adrenergic response
147
What are examples of beta adrenergic responses
relaxation of bronchiolar smooth mm
increased melatonin synthesis & secretion from the pineal gland
increased lipolysis in adipocytes
increased renin secretion from juxtaglomerular cells of the kidney
148
What is the net effect of activating sympathetic nervous system discharge to the endocrine pancreas?
decreased insulin and increased glucagon secretion
149
hexamethonium blocks
(bis-quaternary compounds)
block nicotinic action of acetylcholine at autonomic ganglia, but not at the skeletal neuromuscular junction
150
Atropine blocks
the muscarinic actions of acetylcholine at parasympathetic, postganglionic neuroeffector sites
151
D0tubocurarine (curare) blocks
the nicotinic action of acetylcholine at the skeletal neuromuscular junction, but does not block the nicotinic action of acetylcholine at autonomic ganglia
152
Isoproterenol stimulates
both alpha and beta adrenergic receptors, but predominantly beta receptors
153
Propranolol blocks
the beta-adrenergic actions of catecholamines
154
In relation to the eye, postganglionic sympathetic neurons innervate:
-the muscle that helps life the upper eyelid
-the muscle that helps keep the third eyelid or nictating membrane in place
-sweat glands to the face
-vascular smooth muscle to the face
155
What is the first refractive surface of the eye?
cornea-- and strongest optical protion of theeye
156
The lacrimal gland that is located near the lateral canthus of the eye, produces in tears in response to
parasympathetic nerve stimulation (CN VII)
157
Drugs with what properties penetrate the corneal wall?
both polar (water soluble) and nonpolar (lipid soluble) properties penetrate the corneal wall
158
Which cranial nerve offers sensory fibers to the cornea?
Ophthalmic branch of the trigeminal (5th) crnaial nerve
159
aqueous humour is formed by
ciliary processes through mechanisms of filtration and secretion
160
Aqueous humor is formed in which chamber?
posterior chamber by filtration across fenestrated capillaries in teh cilary processes and by secretion fo solutes accompanied by water across the ciliary epithelium
161
Where does aqueous humor drain?
From anterior chamber into uveal venous blood
162
In comparison to plasma, aqueous humor contains
far less protein and urea than plasma, but more ascorbic acid
163
What drug administration would most likely slow aqueous humor formation?
beta adrenergic blocking agents
164
The outflow of aqueous humor can be affected by
-the condition of the endothelium
-tension of the iris
-tension of the ciliary mm
165
The vitreous humour provides
physical support to the lens and holds the retina against the choroid
166
What are the two substances that different vitreous humor from aqueous humor?
hyaluronic acid and a framework of collagen fibrils
167
The constrictor muscle fibers have what kind of receptors?
muscarinic receptors innerved by the oculomotor nerve (parasympathetic portion)
168
Parasympathetic activation of the oculomotor to the pupil results in
constriction of the pupil
169
Another network of smooth muscle fibers to the pupil consist of what receptors?
alpha 1 adrenergic receptors
-sympathetic innervation that follow the long ciliary enrve-- part of the ophthalmic branch of the trigeminal nerve
170
Activation of the sympathetic innervation to the pupil results in
dilation of the pupil
171
Following administration of an atropine-like drug (muscarinic blocker) this has what effect on the eye?
the pupil constricts, the lens becomes more convex and the eye accommodates for viewing near objects
172
What is the foveal region of the retina
is an area of the eye where inner ganglion and bipolar cells are some what pushed aside, allowing light rays direct access to photoreceptors
173
Compared to cone vision, rod vision lacks resolution because
of convergence of rods on bipolar cells
174
What is rhodopsin?
The photsensitive pigment in outer segment disc membranes of rods
175
Which cells of the retina exhibit depolarizing action potentials?
Ganglion cell axons carry action potentials to the brain through optic nerves
176
What are components of the middle ear?
tympanic membrane, tympanic cavity, auditory tube, auditory ossicles
177
The auditory ossicles (malleus, incus and stapes) and their mm and ligaments functionally connect
the tympanic membrane to the inner ear
178
The inner ear has two receptor systems:
vestibular apparatus: detects the position of the head in space
cochlea: a coiled tube that contains the receptor mechanism for hearing
179
What is the primary function of the vestibular apparatus
to sense forces of acceleration, both linear and rotational
180
Vestibular hair cells form synapses onto sensory fibers of which cranial nerve?
VIII
181
What is the main role of ascending vesitbular pathways to oculomotor nuclei, mainly from the semicircular canals
Reflex control of eye movements, otherwise known as teh vesitbuloocular reflex
