Test 2 Objectives Flashcards
(170 cards)
1
Q
Mechanically gated ion channels
A
Open in response to binding of a mechanical stimulus (touch, pressure, vibration, tissue stretching)
- anything that causes physical distortion of the membrane surface
- location: dendrites of sensory neurons (touch/pressure/pain receptors)
2
Q
What ions pass thru mechanically gated channels?
A
Ca2+, K+, Na+
3
Q
Ligand gated channels
A
Open in response to binding of a ligand (chemical) stimulus
- location: dendrites of sensory neurons (pain receptors), dendrites and cell bodies of interneurons/motor neurons
4
Q
What are the 3 things that ligands can be?
A
- neurotransmitters (at NM junction or neuron to neuron)
- neuromodulators
- intracellular signal molecules
5
Q
What are the ions that pass thru ligand channels?
A
Na+, Ca2+, K+, Cl-
6
Q
Voltage-gated channels
A
Open in response to a voltage stimulus (change in membrane potential)
- location: axons of all types of neurons
7
Q
What are the ions that pass thru voltage-gated channels?
A
Na+, Ca2+, K+, Cl-
8
Q
*Which channel is most important for NM transmission?
A
Ligand gated channels
9
Q
*Which channel is most important for tactile sensation?
A
Mechanically gated channels
10
Q
*Which channel is most important for action potential transmission in the axon?
A
Voltage gated channels
11
Q
Membrane potential is a _____
A
Voltage
12
Q
*Membrane potential’s voltage is determined by _______
A
Differences in the concentrations of ions
13
Q
*Membrane potential sets up what 2 types of gradients?
A
- concentration
- electrical
14
Q
*What are the 5 main ions contributing to membrane potential voltage?
A
- Na+ (extracellular)
- Cl- (extracellular)
- K+ (intracellular)
- Ca2+ (extracellular)
- anions (intracellular)
15
Q
*What 2 things are anions made of?
A
- protein (-)
- PO4 (-)
16
Q
The sodium gradient requires ______ of cell’s energy output
A
25%
17
Q
*The sodium gradient is maintained through what pump?
A
Na+/K+ ATPase pump
- maintains concentration gradient
- 3 Na+ out for 2 K+ in
- contributes -4mV
18
Q
*What would happen if the balance of Na significantly differed from inside to outside?
A
Cell would shrink/swell from osmotic pressure
- intracellular/extracellular osmolarity must be the same to prevent this
19
Q
*_____ is the only important ion that can freely diffuse across the membrane
A
K+
20
Q
Movement of K+
A
K+ moves down its concentration gradient outward thru “K+ leak channels”
- creates elecropositivity outside the membrane and electronegativity inside
21
Q
______ determines the membrane potential
A
K+
22
Q
*What ion is the most tightly regulated it cannot diffuse through the membrane?
A
Calcium
- cannot cross the membrane through diffusion
23
Q
*What is K+ equilibrium potential?
A
Vk = -96.81 mV (lower limit)
24
Q
*What is Ca++ equilibrium potential?
A
Vca = +137.04 mV (upper limit)
25
Internal negative charge prevents what ion from mass entry into the cell?
Chloride
26
What ions are the basis for the negative charge inside the cell?
Anions (proteins and phosphates)
27
Diffusion potential
Difference between the tendency of a cation to diffuse "down" its concentration gradient and its tendency to move in the opposite direction "down" the electrical gradient
28
*What is the resting membrane potential for the neuronal membrane?
- 70 mV
| - determined by K+, Na+, Cl-
29
*The membrane potential allows the neuron, dendrites and axons to have _____ membranes so they can transmit signals
Excitable
30
*The trigger zone is located (in an efferent neuron) at the __________
Axonal hillock
| - is the integrating center of the neuron (the initial segment)
31
*You must reach the _____ to stimulate the axon to transmit an action potential
Threshold
| - between -40 and -55 mV
32
What are 2 types of signals created by membrane potentials?
- graded potentials (do not travel far)
| - action potentials (principal means of neural communication)
33
Nerve impulse
An action potential in the axon of a neuon
34
*A depolarization makes the membrane potential more _____
Positive
35
*A hyperpolarization makes the membrane potential more _____
Negative
36
Each Na+ channel has 2 ______
Voltage-regulated gates
- activation gates: closed in resting state
- inactivation gates: open in resting state
37
*1st step of action potential: _____ is reached
Threshold; makes depolarization self-generating via graded potentials
38
*2nd step of AP: Triggers opening of _______
Activation gates of the voltage gated Na+ channels
| - channel is open for a predetermined amount of time until the inactivation gate closes
39
*Once the inactivation gates close, _____ rushes into the cell down its potential
Na+; makes the membrane more positive on the inside
| - triggers neighboring voltage gated Na+ channels to open propagating the action potential
40
*Absolute refractory period
Time from the opening of the Na+ activation gates until the closing of the inactivation gates
41
3 functions of the absolute refractory period
- prevents neuron from generating another AP
- ensures that each AP is separate
- enforces one-way transmission of nerve impulses
42
*3rd step of AP: ________ open and _____ rushes down its concentration gradient
Voltage gated K+ channels; K+
| - membrane becomes more negative as K+ leaves the cell
43
*Extra negativity creases a ______ membrane potential
Hyperpolarized
44
*The hyperpolarized membrane potential creates the ______
Relative refractory period
- Na+ gates are closed
- K+ gates are open
- repolarization occurs
45
During the relative refractory period, the neuron can ____
Fire again, but the threshold level is elevated
| - requires a stronger than normal stimuli
46
*To reach the threshold potential to create a new AP, you have to get from hyperpolarized potential ____ to the threshold at _____
~-80 to - 90 mV; -55 mV
47
*The Na/K ATPase pump kicks into high gear to get the ____ out of the cell and the ____ back in
Na+; K+
- returns membrane to its resting membrane potential
- restores ionic redistribution
48
*The action potential consists of ______, ______, and _______
Depolarization, repolarization, and hyperpolarization
49
Mechanisms that increase conduction velocity of an action potential
- increase axon diameter (decreases internal resistance)
| - insulate axon membrane (decreases current leak, increases distance of passive flow, obtained via myelin sheath)
50
*Where does myelin live?
On axons
51
*Who creates myelin in the CNS?
Oligodendrocytes
| - ratio is 1:many axons
52
*Who creates myelin in the PNS?
Schwann cells
| - ratio is 1:1 in myelinated and 1:many in unmyelinated
53
*What are the 3 functions of myelin?
- protection of axon
- electrically insulating fibers from one another
- increases speed of nerve impulse transmission through saltatory conduction, jumping from Nodes of Ranvier
54
Saltatory conduction
Action potential travels by jumping from one node of Ranvier to the next
55
What 3 things determine how much compression the axon can tolerate before loss of function?
- size of the axon
- location in the cord
- degree of myelination
56
*Which axons are affected first with spinal cord compression?
Large heavily myelinated fibers
| - more vulnerable to injury, but are the fastest at conduction velocity
57
What is the order of loss following compression?
- proprioception
- motor function is decreased
- autonomic function
- motor function - absent
- tactile sensation - present
- tactile sensation - absent
58
* What is the last function lost with severe spinal cord compression/disease?
Deep pain
59
*What is the prognosis for return to function with deep pain loss?
50/50 depending on time
60
*Synapses occur where?
Between a neuron and another neuron or effector cell (axon terminals)
61
What is the difference between pre and postsynaptic neruons?
- presynaptic: conducts impulses toward the synapse
| - postsynaptic: transmits impulses away from the synapse
62
What are the 2 types of synapses?
- electrical: travels thru gap junctions in both directions (cardiac/smooth)
- chemical: use neurotransmitters and synaptic cleft
63
*As the action potential reaches the axon terminal, the change in membrane potential opens voltage gated ___ channels
Ca2+
64
*Increased Ca2+ causes ____ to fuse with axon membrane
Synaptic vesicles; causes exocytosis of neurotransmitter into synaptic cleft
65
*Receptors on the post synaptic membrane are of which variety?
Ligand
66
*What ion do they allow into the post synaptic cell?
Na*
67
*If enough Na+ enters the cell it triggers the opening of _______ channels and triggers an action potential
Voltage gated Na+
68
*At the synapses you are taking an _____ signal turning it to a _____ signal and then back to an _____ signal
Electrical; chemical; electrical
69
*What are 3 ways to remove a neurotransmitter from the synaptic cleft?
- diffusion
- re-uptake via active transport
- degradation of enzymatic destruction of enzymes located in cell membranes of pre and postsynaptic cells
70
*Excitatory post-synpatic potential _______ membrane potential slightly
Depolarizes
- opens Na+ channel
- makes membrane more positive --> increases probability of an action potential
71
*Inhibitory post-synaptic potential _______ membrane potential
Hyperpolarizes
- opens Cl- channel
- makes membrane more negative --> decreases probability of an action potential
72
*What must a neurotransmitter do to be considered a neurotransmitter?
- substance must be present within a presynaptic neuron
- substance must be released in response to presynaptic depolarization and must be Ca2+ dependent
- specific receptors for the substance must be present on postsynaptic cell
73
*Which would mimic the action of a neurotransmitter by binding to its receptor: agonist or antagonist?
Agonist
- could be full, super, or partial
- inverse agonist binds to same site as agonist but induces opposite response (blocks)
74
Antagonist
Binds to a neurotransmitter receptor and blocks the action of the endogenous neurotransmitter
75
*What are 7 major excitatory neurotransmitters?
- Ach
- glutamate
- epinephrine
- norepinephrine
- dopamine
- serotonin
- histamine
- -> Na+ enters their ligand gated channels
76
*What are the 3 major inhibitory neurotransmitters?
- GABA
- glycine
- -> Cl enters thru their ligand gated channels
77
*Where are nicotinic receptors found? Who binds to them?
Neuromuscular junction (somatic) or preganglion neurons in ANS
- Ach binds to them
- ionotropic receptor
78
*Where are muscarinic receptors found? Who binds to them?
Post ganglionic neuron of parasympathetic nervous system (PSANS)
- Ach binds to them
- metabotropic receptor
79
*What degrades Ach?
Acetylcholinesterase
- Acetylcholine is degraded to choline which is transported back into neuron
- target for treatment of Alzheimers and myasthenia gravis, and pesticides
80
What is the difference between metabotropic and ionotropic receptors?
Metabotropic: slow, prolonged response
- G protein-linked receptors with a second messenger system to trigger biochemical changes
Ionotropic: fast, short acting response
- ligand gated channel produces brief change in membrane potential
81
*What neurotransmitter do we believe is responsible for excitotoxicity following head trauma?
Glutamate
| - major excitatory neurotransmitter in CNS
82
*What neurotransmitters are affected in tetanus?
GABA (major inhibitory neurotransmitter) and glycine (major inhibitory neurotransmitter in spinal cord)
83
*What neurotransmitters are affected with strychnine toxicity?
Glycine
| - blocks glycine binding so all the cells see are excitatory neurotransmitters
84
*What are the neurotransmitters and receptors of the post-ganglion neurons of the SANS?
Epinephrine, norepinephrine, a1, a2, b1, b2, b3
85
*What neurotransmitter has agonist created to be anti-seizure medications?
GABA
86
*Which neurotransmitters are often manipulated for behavior modifications?
- serotonin: mood/arousal/anxiety
- dopamine: ADHD
- histamine: arousal/sleep
87
*What nerve is involved in the patella reflex?
```
Femoral nerve (sensory and motor)
- L4-5
```
88
*What nerves are involved in withdrawal in the hindlimb and forelimbs?
Hindlimb
- sciatic nerve (sensory and motor): L6-7, S1
Forlimb
- motor: musculocutaneous (C6-8), axillary (C7-8), median (C8-T1), ulnar (C8-T1), radial (C7-T1)
- sensory: varies with area stimulated
89
*Which diffuse LMN disease affects the cranial nerves as well as the peripheral nerves?
Botsulism
| - cranial nerve GSE components affected
90
*What is attacked and its location in coonhound paralysis? What is the doctor term for this disease?
Myelin in the ventral nerve root via contact with a raccoon
- polyradiculoneuritis
- cranial nerves should be normal
91
*What animals are most prone to botulism vs. which are least susceptible?
Most prone: cow/horse
| Least susceptible: cat, dog, pigs
92
*Why does treating an animal with myasthenia gravis with an anticholinesterase inhibitor work?
Leaves Ach in cleft so it can find Ach receptors not attacked
- treat with anticholinesterase
93
*What would happen in an anticholinesterase overdose (similar to OP toxicity)?
Overstimulation of somatic and parasympathetic/sympathetic nervous system
- muscarininc receptor overload and parasymptathetic mimetic
- SLUTD
94
*What ticks cause tick paralysis in the US?
Female dermacantor
95
*Damage to what nerve results in a dropped elbow?
Radial
96
*Damage to what nerve results in a dropped jaw?
Mandibular branch of trigeminal
97
*An axon belonging to a UMN is a ______
Tract
| - cell body and axon within the CNS
98
*An axon belonging to a LMN is a ___
Nerve
| - cell body within CNS, axon travels into periphery
99
*UMN usually synapse on what?
Interneurons that go on to synapse on a LMN
100
*Exceptions to UMN synapses are which 2 tracts?
Corticospinal and vestibulospinal
101
*Which is better for a functional recovery after neuronal cell loss?
UMN to synapse on interneuron before synapsing on LMN
102
*Are any descending motor tracts in the dorsal funiculus?
No, strictly ascending sensory
103
Lateral funiculus
Descending motor tracts facilitating flexor muscle activity and inhibiting extensor muscle
104
Ventral funiculus
Descending motor tracts facilitating extensor muscle activity and inhibiting flexor muscles
- exception: ventral corticospinal tract
105
*What do tracts in the lateral funiculus do and what phase of the gait is this?
- flex/swing phase
- lateral corticospinal, rubrospinal, medullary reticulospinal
- facilitated by cerebral input
106
*What do tracts n the ventral funiculus do and what phase of the gait is this?
Extensor - support, stance, protraction
- vestibulospinal, pontine reticulospinal, ventral corticospinal
- inhibited by cerebral input
107
_____ is dependent on extensor tone
Posture
108
* I have a dog who cannot move his back legs at all but still feels his feet, how would you tell me this in doctor words?
Pain positive, paraplegic
109
*I have a dog that can walk but it is very ataxic in all four limbs and can feel his feet, how you you describe this?
Ambulatory tetraparetic
110
*What are the 3 main pyramidal tracts?
- corticopontine
- corticonuclear
- corticospinal
111
*Which pyramidal tract allows cerebellar input?
Corticopontine
- feed back loop: how cerebellum controls/modulates motor activity leaving the brain
- involves middle afferent and rostral efferent peduncles
112
*Which pyramidal tract controls LMN in the spinal cord?
Corticospinal
| - lateral tract decussates at the pyramids
113
*Which pyramidal tract controls LMN in the brainstem?
Corticonulcear
| - mediates voluntary eye movements, mastication, facial expression, swallowing, neck/tongue movement
114
*Which pyramidal tract does not make it to the pyramids?
Corticopontine
115
*What mammals have the best developed pyramidal tracts?
Primates, raccoons, horse, cats
| - most developed thru thoracic intumescence
116
*Where are extrapyramidal UMN located?
Midbrain, pons, medulla
| - important for posture and locomotion
117
*Which extrapyramidal UMN decussate vs do no decussate?
Decussate: rubrospinal
| Do not decussate: medullar reticulospinal, pontine reticulospinal, vestibulospinal
118
*What is the extrapyramidal connection to the cerebellum?
Olivary nucleus
- efferents from red nucleus and reticular formation to contralateral cerebellum via caudal cerebellar peduncle
- creates feed back loop
119
*What is the most important tract for motor in dogs?
Rubrospinal
| - facilitator to flexor muscles
120
*What conditions result in extensor rigidity?
- decerebrate rigidity: lesion in midbrain between rostral and caudal colliculi (sensorium deficits)
- decerebellate rigidity: pelvic limbs in extension but flexed at hips (sensorium normal)
- Schiff sherrington
121
*What are the 4 basal nuclei?
- caudate nucleus
- putamen
- globus pallidus
- claustrum
122
*Which basal nuclei is located medial to the internal capsule?
Caudate nucleus
123
Which basal nuclei is located outside the internal capsule?
Globus pallidus, putamen, claustrum
124
Neostriatum
- caudate nucleus
| - putamen
125
Paleostriatum
Globus pallidus
126
Lentiform
- globus pallidus
| - putamen
127
*What nucleus influences the neostriatum?
Substantia nigra
| - releases dopamine to neostriatum
128
*What nucleus does the lateral globus pallidus influence?
Subthalamic nucleus
| - is excitatory to medial GP, increases inhibition to thalamus and decreases thalamus ability to excite the cortex
129
*Who talks to the thalamus?
Medial globus pallidus
| - inhibits thalamus with GABA directly
130
*Who influences the medial GP?
Neostriatum: caudate, substantia nigra, subthalamic nucleus/lateral GP
131
*What are the 3 kinds of ataxia?
- proprioceptive
- vestibular
- cerebellar
132
*Which ataxia is found with weakness?
Spinal
133
*A lesion in the medulla on the right side of the body would cause deficits on which side of the body?
Right
| - lesions on pontine and medullary reticular formation induces ipsilateral deficits
134
*A lesion in the cerebral cortex on the right side would cause deficits on which side of the body?
Left
135
*Which results in increased extensor tone or spasticity?
UMN
136
*Which would cause increase in the reflexes?
UMN
137
*Damage to what areas of the spinal cord will result in UMN signs, only to the hindlimbs?
T3-L3
138
*Damage to what area of the spinal cord could create LMN signs in the forelimbs?
C6-T2
- hindlimbs: L3-S3
139
*Damage to what area of the spinal cord would result in UMN signs to all 4 limbs?
C1-C5
140
*What are the 2 types of LMN's?
Alpha: innervate extrafusal (skeletal) muscles
Gamma: innervate intrafusal muscle fibers of muscle spindle
141
*Intrafusal muscle fibers are also known as?
Muscle spindles
142
*What is the afferent axon from golgi tendon organs?
Type 1b sensory fibers
| - responds to higher tension than is needed to activate a muscle spindle
143
*What LMN do 1b fibers innervate?
Provides feedback inhibition to alpha motor neuron
144
*What reflex is the simplest using just the afferent axon and LMN?
Femoral/patella
145
*An UMN creates "muscle tone" through innervating what LMN?
Gamma
| - high activity if movements require rapid and precise execution
146
*Eliciting a flexor reflex in an animal with UMN disease can produce what?
Hyper reflex, crossed extensor
| - should not be present if animal is in lateral recumbency
147
*What reflex can help to localize the area of spinal cord injury to the vertebra not just functional spinal cord divisions?
Cutaneous trunci
| - start caudally
148
*What nerve is involved, what muscle is innervated and where do the LMN live in the spinal cord?
Lateral thoracic, cutaneous trunci, C8-T1
149
*What nerves are involved in the perineal reflex?
Pudendal (sensory and motor), caudal
150
*Would a dog with an injury to just past the sacrum be able to walk?
Yes
151
*What allows a dog with a functional or anatomic transection of the spinal cord to "walk"?
Central pattern generators
- each limb has a pattern generator responsible for alternating flexion and extension of the limb during locomotion (do not require connections with UMNs or sensory input)
152
*Would the dog do this with a T3-L3 lesion?
Yes
153
*Would the dog do this with a L3-S3 lesion?
No
154
*I have a dog with paraplegia (UMN) but increased extensor tone in the forlimbs, where could the lesion be in the spinal cord?
Injury to T3-L3
| - Schiff Sherrington
155
*What are the 3 layers of the cerebellar gray matter?
- molecular: least cellular
- purkinje: contain purkinje cells, release GABA (inhibitory) --> synapse on DCN
- granule: contain ganule cells (excitatory) and golgi cells (inhibitory) --> release GABA
156
*What are 2 fibers that ascend into the cerebellum?
- mossy: excitatory, make up the MCP from the pontine nuclei from the corticopontine tract, synapse on DCN, granule cells and golgi cells
- climbing: excitatory with aspartate, synapse on DCN and molecular layer, from olivary nucleus
157
*Peduncles: which is mainly output?
Rostral
158
*What are the signs of cerebellar disease?
No loss of strength/no weakness, hypermetria, intention tremors, ipsilateral menance deficits
159
*Deep cerebellar nuclei are supposed to be ________
The only source of output from the cerebellum
160
*Exception to this rule ______
Purkinje fibers of flocculonodular lobes
| - synapse directly on the vestibular nuclei thru the CCP
161
*Fastigal nuclei
Associated with vermis (spinocerebellum) and vestibulo cerebellum
162
*Interposed nuclei
Internudiate zone (spinocerebellum)
163
*Dentate nuclei
Hemispheres, cerebrocerebellum, RCP
| - modulating control of voluntary motor (most ipsilateral)
164
*What are the nerve endings/types for proprioception?
Pacinian corpuscle, Ruffini's corpuscle, muscle spindles, golgi tendon organs, joint receptors
165
*Where is a good dermatome for testing the radial nerve?
Front of radius/ulna
166
Dermatome
Areas of skin innervated by the sensory nerve fibers of a single spinal nerve
167
*What happens when you loose the radial nerve?
Dropped elbow
168
*What pathway transmits proprioceptive/non-painful sensation?
Medial lemniscus
169
*Where does the medial lemniscus travel in the spinal cord?
Dorsal funiculus
170
*What pathway transmits pain signals?
Spinothalamic
| - travels in the lateral funiculus
