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Engelking Phys Review > Section2.Neuromscular physiology and special senses > Flashcards

Section2.Neuromscular physiology and special senses Flashcards

1
Q

Voltage gated channels

A

the molecular conformation of the gate responds to the electrical potential across the cell membrane

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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

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3
Q

Voltage gating is involved in

A

action potential propagation along the axons of nerves

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4
Q

Chemical gating is involved in

A

transmission of signals from one nerve cell to another, and from nerve cells to muscle cells

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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)

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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

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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

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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

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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)

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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

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11
Q

Which electrolyte has the highest membrane conductance in the resting state?

A

K

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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

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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

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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

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15
Q

capacitance

A

membranes ability to store or separate a small amount of charge across it surface

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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

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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

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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

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19
Q

What is the effect of myelination on conduction velocity?

A

myelination r (m) and decreases c (m), thereby increasing conduction velocity

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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

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21
Q

Na (and K) channels are most concentrated in which part of the myelinated neuron?

A

Nodes of Ranvier

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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

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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

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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

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25
Q

What is the relative refractory period?

A

period following repolarization, the nerve cell becomes capable of firing a second action potential, yet a stronger than normal stimulus is required and

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26
Q

The relative refractory period is due to what electrolytes?

A

is due to the high K conductance occurring during this time

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27
Q

70% of the energy used by a nerve goes toward which function?

A

maintaining the polarity of its membrane through the action of Na/K Atpase

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28
Q

For a short period of time following the spike of an action potential, the membrane becomes

A

even more negative than the original resting potential
called the undershoot

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29
Q

What is the overshoot period?

A

period during depolarization when the membrane potential spikes and normally overshoots zero mV to approximately +35 mV

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30
Q

Define orthodromic conduction

A

an impulse passing along an axon from cell body to the nerve terminal
**normal in mammals

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31
Q

define antidromic conduction

A

moving toward the cell body
**rarely occurs

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32
Q

Chemical synapses

A

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

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33
Q

Which type of synapse has displays a synaptic delay?

A

Chemical synapses

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34
Q

An endplate potential or synaptic potential is transient because

A

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

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35
Q

What are miniature endplate potentials?

A

due to the spontaneous and random releases of ACh from pre-synpatic nerve terminals at the skeletal neuromuscular junction

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36
Q

Patients with Myasthenia gravis, end plate potentials is related to

A

reduced numbers of ACh receptors on the post-synaptic membrane of skeletal muscle fibers that is most likely due to autoimmune destruction

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37
Q

Why do treatments, such as neostigmine, physostigmine or diisopropyl fluorophosphate work in the treatment of Myasthenia gravis?

A

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

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38
Q

What is the most prevalent inhibitory amino acid neurotransmitter in the brain?

A

GABA

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39
Q

What are the most prevalent excitatory neurotransmitters in the brain?

A

Glutamate and Aspartate

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40
Q

Which neurotransmitters are thought to undergo reuptake intact into the neuron that secretes them?

A

-norepinephrine
-serotonin
-GABA
-glutamate

acetylcholine does not

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41
Q

What is spatial summation?

A

two EPSPs are additive, while one IPSP is capable of canceling one EPSP

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42
Q

What is temporal summation?

A

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

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43
Q

define augmentation

A

pertains to the enhancement of synaptic efficacy that occurs intermediately between facilitation and posttetanic potentiation

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44
Q

define posttetanic potentiation

A

may occur for several seconds after a presynaptic neuron is sitmulated tetanically

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45
Q

define facilitation

A

When a presynaptic axon is fired repeatedly, the postsynaptic response may grow with each stimulus

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46
Q

Muscarinic, M1 receptors are found where

A

in the brain

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47
Q

Muscarinic, M2 receptors are found where

A

smooth and cardiac muscle

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48
Q

Muscarinic, M4 receptors are found where

A

pancreatic acinar and islet tissue and smooth mm

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49
Q

Muscarinic M1, M4 and M5 receptors function through what second messenger system?

A

through IP3 (and thus Ca) and diacylglycerol

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50
Q

Muscarinic, M2 and M3 receptors function through what second messenger system?

A

through cyclic-AMP mediated pathways

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51
Q

What are distinguishing characteristics of Type I skeletal mm fibers?

A

**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

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52
Q

Type I vs Type II skeletal muscle fibers are used for what kinds of exercise?

A

Type I: aerobic fibers, used for sustained exertion

Type II: anaerobic fibers, more useful during short periods of heavy lifting

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53
Q

Thick filaments of vertebrate skeletal and cardiac mm are largely composed of

A

Myosin

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54
Q

Myofibrils make up what percentage of skeletal muscle vs cardiac muscle?

A

skeletal mm= 80 to 87% of cell interior is myofibrils

cardiac mm= 50% of cell interior is myofibrils

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55
Q

Describe Thin myofibrillar filaments

A

-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

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56
Q

Describe thick myofibrillar filaments

A

-14-16 nm
-contain protrusions or cross-bridges that extend outward from their surfaces at regular intervals
-contain all the myosin in the myofibril

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57
Q

What proteins make up thick filaments

A

95% myosin
5% C-protein

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58
Q

what proteins make up thin filaments?

A

actin
Beta-actinin
tropomyosin
-3 forms of troponin (TnT, TnI, TnC)

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59
Q

What protein makes up the darkly staining amorphous part of the Z-disk?

A

alpha-Aactinin

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60
Q

Describe what phase or twitch fibers are

A

a propagated action potential and twitch response following nerve stimulation
–fast contraction times

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61
Q

Describe what slow or tonic fibers are

A

muscle fibers respond to nerve stimulation with a prolonged contracture and usually exhibit no propagated action potential

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62
Q

Tonic muscle fibers are usually innervated in what format?

A

En grappe type of innervation

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63
Q

Phasic fibers are generally innervated in what format?

A

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)

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64
Q

What is the difference between phasic muscle fibers and tonic muscle fibers, when acetylcholine is applied?

A

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

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65
Q

A majority of mammalian skeletal muscle fibers are of what kind?

A

phasic or fast type

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66
Q

Define excitation-contraction coupling

A

mechanism by which the action potential, passing along the plasmalemma and T-tubules, eventually initiates contraction

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67
Q

T-tubules function

A

conduct a signal from a nerve impulse to the interior of the skeletal mm or cardiac mm cell

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68
Q

What are the two sets of tubules within skeletal mm cells?

A

T-system: transverse sys
L-system: longitudinal sys

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69
Q

L system of t-tubules is also called the

A

sarcoplasmic reticulum

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70
Q

invaginations of the sarcolemma forms which skeletal muscle tubules?

A

T-tubules

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71
Q

T tubules run what direction in respect to the long axis of skeletal and cardiac muscle cells?

A

perpendicular

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72
Q

T-tubules occur at regular intervals along the length of the muscle cell, what is the difference between cardiac mm and skeletal mm?

A

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

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73
Q

Ca-ATPase within the muscle cell sarcoplasmic reticulum function

A

keeps the cytplasmic Ca concentration in resting muscle cells at a low level

74
Q

What is the voltage sensor in skeletal muscle responsible for initiating the contraction process is the:

A

Dihydropyridine receptor

75
Q

What occurs after a T-tubule is depolarized, in a skeletal mm fiber

A

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
Q

The binding of calcium to troponin C (TnC) causes

A

Troponin I (TnI) to loose its affinity for actin/

77
Q

After troponin I looses its affinity for actin, what occurs to the troponin-tropomyosin complex?

A

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
Q

What occurs when there is no ATP available to dissociate the actin-myosin complex?

A

The thick and thin filaments cannot be separated and rigor mortis ensues

79
Q

When does relaxation of mm occur?

A

When calcium is removed from the cytoplasm by Ca pumps located on the sarcoplasmic reticulum

80
Q

What occurs when intracellular Ca concentration falls in skeletal mm cells?

A

troponin returns to its original conformational state, tropomyosin inhibition of myosin-actin interaction is restored and cross bridge cycling stops

81
Q

In regards to skeletal mm, hypermagnesemia is associated with

A

a decrease in neuromuscular irritability

82
Q

Muscle fatigue is most likely caused by:

A

H

**when lactic acid dissociates

83
Q

Ca release from teh sarcoplasmic reticulum of cardiac mm is done through

A

the ryanodine receptor (or channel)

84
Q

What is the difference between cardiac mm and skeletal mm during exercise?

A

cardiac muscle removes lactate from blood and utilizes it for energy

85
Q

Because cardiac cells rely heavily on aerobic metabolism, cardiac muscle cells contains

A

many mitochondria and a lot of myoglobin

86
Q

What are intercalated disks of cardiac muscle?

A

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
Q

Function of intercalated disks of cardiac mm

A

strong attachment between fibers at the intercalated disks maintains cell to cell adhesion necessary for individual units pulling each other along during contraction

88
Q

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

A

gap junctions

89
Q

Unlike skeletal mm, cardiac mm is resistant to

A

tetany– because it is generally refractory to repeated stimuli

90
Q

Teh positive inotropic effet of catecholamines is mediated through what receptors?

A

b1 adrenergic receptors and intracellulary by cyclic-AMP

91
Q

Digitalis glycosides inhibit what in the cell membranes of cardiac mm fibers?

A

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
Q

What are characteristics of multi-unit smooth muscle?

A

-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
Q

Unitary smooth muscle characterstics

A

-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
Q

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?

A

unitary smooth muscle

95
Q

What are caveolae of smooth mm?

A

-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
Q

Excitation-contraction coupling of smooth muscle is thought to be regulated by:

A

Ca-induced phosphorylation of myosin

97
Q

What are ways that calcium can enter the smooth mm cells?

A
  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
Q

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?

A

Nitric oxide

99
Q

What is the primary function of the autonomic nervous system?

A

control the immediate, dynamic process of tissues glands and organs it innervates
**vs long term physiological processes controlled by endocrine system

100
Q

The classical efferent visceral component of the ANS, is subdivided into both anatomically and physiologically into

A

parasympathetic and sympathetic divisions

101
Q

Both sympathetic and parasympathetic divisions contain two neuron pathways with cell bodies of preganglionic neurons located where?

A

within the CNS ( spinal cord or motor nuclei of cranial nerves)

102
Q

The parasympathetic nervous system primary contains which fibers?

A

cholinergic (both pre and postganglionci fibers)

103
Q

Preganglionic neurons fo the PNS are associated with what cranial nerves?

A

III: oculomotor
VII: facial
IX: glossopharyngeal
X: vagus

  • as well as sacral regions of the spinal cord
104
Q

Stimulation of the sympathetic nervous system results in what fight or flight responses?

A

INC heart rate
bronchial dilatation
INC blood pressure
INC blood glucose (dec in insulin secretion)
piloerection
sweating
dilation of the pupil
Etc.

105
Q

Which division of the ANS exerts the greatest influence on heart rate during the resting state?

A

The parasympathetic division, because if you cut both vagal and sympathetic fibers to the SA node, heart rate increases

106
Q

In comparison, norepinephine spreads further/ closer and has short duration or prolonged action than acetylcholine?

A

Norepinephrine spreads farther and has a more prolonged action than acetylcholine

107
Q

Where does the majority of norepinephrine diffuse into blood from?

A

from noradrenergic (sympathetic) nerve endings

108
Q

Acetylcholinesterase at cholinergic nerve endings functionsin

A

hydrolyzes excess acetylcholine
into choline and acetate

109
Q

Does re-uptake of acetylcholine occur at nerve terminals?

A

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
Q

Which enzyme catalyzes the hydrolysis of acetylcholine?

A

choline acetylase– substrates being choline and active acetate

111
Q

Parasympathetic, postganglionic neuroeffector sites are

A

Muscarinic

112
Q

synapses at ganglion cells of the entire autonomic nervous system, as well as somatic myoneural junctions are:

A

nicotinic

113
Q

The muscarinic vs the nicotinic receptors are blocked by which drugs (that differentiates them)?

A

Muscarinic blocked by atropine

Nicotinic blocked by nicotine, bis quaternary compounds or curare

114
Q

Anticholinesterases have what effect on ehart rate?

A

decrease heart rate

– because they prolonged the effect of AcH

115
Q

Anticholinesterase drugs are used to treat what disease?

A

myaasthenia gravis– an autoimmunse disease with circulating antibodies ot nicotinic recpetors

116
Q

What is the rate-limiting enzyme in catecholamine biosynthesis?

A

tyrosine hydroxylase

117
Q

Where are these catecholamines primarily produced:
norepinephrine
epinephrine
dopamine

A

NE: adrenergic nerve cells in ANS
Epi: chromaffin cells in adrenal medulla
Dopamine: primary adrenergic activity in the CNS

118
Q

What are degradative enzymes that convert catecholamines into inactive compounds?

A

monoamine oxidase
catecholamine-O-mmethyltransferase

119
Q

Glucocorticoids enhance adrenal epinephrine synthesis by activating which enzyme?

A

phenylethanolamine-N-methyltransferase

120
Q

Where is epinephrine formed?

A

in the adrenal medulla from NE, by action of phenylethanolamine-N-methyltransferase

121
Q

Regarding re-uptake of norepinephrine (or its degradative product) at the adrenergic nerve terminal– what occurs?

A

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
Q

monoamine oxidase is a degradative enzyme located where?

A

within mitochondria

123
Q

measurement of which of the following compounds in urine would be the best index of the rate of adrenal catecholamine secretion?

A

metanephrines and vanillylmandelic acid

**breakdown products of Epi/NE/dopamine

124
Q

What does beta adrenergic receptor activity involve?

A

stimulation of adenyl cyclase, leading to an increase in intracellular cyclic-AMP

125
Q

What does alpha receptor activity involve?

A

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
Q

all pre-synaptic alpha-adrenergic receptors are thought to be of whcih variety?

A

alpha 2

127
Q

Post-synpatic receptors appear to be of what alpha-adrenergic receptor?

A

alpha 1 (a few of alpha 2s)

128
Q

Presynpatic alpha 2 adrenergic recpetor are response for

A

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
Q

Postsynaptic alpha 2 receptor stimulation leads to

A

increase in Ca influx that is largely independent of the c-AMP messenger system

130
Q

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

A

alpha 2 and muscarinic

beta 2 and angiotensin II

131
Q

sensitive D1 receptors for dopamine act by

A

enhancing intracellular activity of adenyl cyclase

132
Q

sensitive D2 receptors for dopamine act by

A

reducing intracellular activity of adenyl cyclase

133
Q

dopamine inactivation requires

A

DOPA hydroxylase

134
Q

Synaptic dopamine can be recaptures via

A

an active re-uptake mechanism similar to that described for NE

135
Q

Beta 1 adrenergic receptors are found

A

in heart, on fat cells and on juxtaglomerular cells of the kidney

136
Q

stimulation of beta2 receptors casues

A

vasodilation in pulmonary coronary, skeletal and visceral circulation and relaxation of bronchiolar smooth mm

137
Q

where are allpha 1 adrenergic receptors found

A

on radial smooth mm of iris and sitmulated cause mydriasis

138
Q

atropine blocks

A

muscarinic receptors

139
Q

isoproterenol stimulates

A

beta-adrenergic receptors

140
Q

What occurs when norepinephrine is infused slowly into normal, resting subjects?

A

-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
Q

In the heart, what is the effect of NE and epi?

A

increase the contractile force of the heart, bediated by ebta1 adrenergic receptors

142
Q

Different from norepinephrine, epinphrine causes

A

dilates blood vessels in skeletal mm and liver via beta 2 receptor stim

143
Q

Why does epinephrine cause a widening of the pulse pressure?

A

b/c of an increased systolic and decreased diastolic pressure (cardiac rate and output increase)

144
Q

Sympathetic innervation may provide reciprocal innervation t through:

A

alpha: generally stimulatory

beta: generally inhibitory

145
Q

Which adrenergic receptors are on coronary blood vessels

A

adrenergic: alpha1, beta2

cholinergic: ach

146
Q

Erection is a (parasymp/sympath)response and ejaculation is a (blank)response?

A

erection is a parasympathetic response, ejculation is an alpha adrenergic response

147
Q

What are examples of beta adrenergic responses

A

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
Q

What is the net effect of activating sympathetic nervous system discharge to the endocrine pancreas?

A

decreased insulin and increased glucagon secretion

149
Q

hexamethonium blocks
(bis-quaternary compounds)

A

block nicotinic action of acetylcholine at autonomic ganglia, but not at the skeletal neuromuscular junction

150
Q

Atropine blocks

A

the muscarinic actions of acetylcholine at parasympathetic, postganglionic neuroeffector sites

151
Q

D0tubocurarine (curare) blocks

A

the nicotinic action of acetylcholine at the skeletal neuromuscular junction, but does not block the nicotinic action of acetylcholine at autonomic ganglia

152
Q

Isoproterenol stimulates

A

both alpha and beta adrenergic receptors, but predominantly beta receptors

153
Q

Propranolol blocks

A

the beta-adrenergic actions of catecholamines

154
Q

In relation to the eye, postganglionic sympathetic neurons innervate:

A

-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
Q

What is the first refractive surface of the eye?

A

cornea– and strongest optical protion of theeye

156
Q

The lacrimal gland that is located near the lateral canthus of the eye, produces in tears in response to

A

parasympathetic nerve stimulation (CN VII)

157
Q

Drugs with what properties penetrate the corneal wall?

A

both polar (water soluble) and nonpolar (lipid soluble) properties penetrate the corneal wall

158
Q

Which cranial nerve offers sensory fibers to the cornea?

A

Ophthalmic branch of the trigeminal (5th) crnaial nerve

159
Q

aqueous humour is formed by

A

ciliary processes through mechanisms of filtration and secretion

160
Q

Aqueous humor is formed in which chamber?

A

posterior chamber by filtration across fenestrated capillaries in teh cilary processes and by secretion fo solutes accompanied by water across the ciliary epithelium

161
Q

Where does aqueous humor drain?

A

From anterior chamber into uveal venous blood

162
Q

In comparison to plasma, aqueous humor contains

A

far less protein and urea than plasma, but more ascorbic acid

163
Q

What drug administration would most likely slow aqueous humor formation?

A

beta adrenergic blocking agents

164
Q

The outflow of aqueous humor can be affected by

A

-the condition of the endothelium
-tension of the iris
-tension of the ciliary mm

165
Q

The vitreous humour provides

A

physical support to the lens and holds the retina against the choroid

166
Q

What are the two substances that different vitreous humor from aqueous humor?

A

hyaluronic acid and a framework of collagen fibrils

167
Q

The constrictor muscle fibers have what kind of receptors?

A

muscarinic receptors innerved by the oculomotor nerve (parasympathetic portion)

168
Q

Parasympathetic activation of the oculomotor to the pupil results in

A

constriction of the pupil

169
Q

Another network of smooth muscle fibers to the pupil consist of what receptors?

A

alpha 1 adrenergic receptors
-sympathetic innervation that follow the long ciliary enrve– part of the ophthalmic branch of the trigeminal nerve

170
Q

Activation of the sympathetic innervation to the pupil results in

A

dilation of the pupil

171
Q

Following administration of an atropine-like drug (muscarinic blocker) this has what effect on the eye?

A

the pupil constricts, the lens becomes more convex and the eye accommodates for viewing near objects

172
Q

What is the foveal region of the retina

A

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
Q

Compared to cone vision, rod vision lacks resolution because

A

of convergence of rods on bipolar cells

174
Q

What is rhodopsin?

A

The photsensitive pigment in outer segment disc membranes of rods

175
Q

Which cells of the retina exhibit depolarizing action potentials?

A

Ganglion cell axons carry action potentials to the brain through optic nerves

176
Q

What are components of the middle ear?

A

tympanic membrane, tympanic cavity, auditory tube, auditory ossicles

177
Q

The auditory ossicles (malleus, incus and stapes) and their mm and ligaments functionally connect

A

the tympanic membrane to the inner ear

178
Q

The inner ear has two receptor systems:

A

vestibular apparatus: detects the position of the head in space

cochlea: a coiled tube that contains the receptor mechanism for hearing

179
Q

What is the primary function of the vestibular apparatus

A

to sense forces of acceleration, both linear and rotational

180
Q

Vestibular hair cells form synapses onto sensory fibers of which cranial nerve?

A

VIII

181
Q

What is the main role of ascending vesitbular pathways to oculomotor nuclei, mainly from the semicircular canals

A

Reflex control of eye movements, otherwise known as teh vesitbuloocular reflex

Engelking Phys Review (5 decks)

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