Exam 2 Flashcards
Which channel is most important for NM transmission?
Ligand channels
Which channel is most important for tactile sensation?
Mechanically gated channels
Which channel is most important for action potential transmission in the axon?
Voltage gated channels
What is the membrane’s potential determined by?
Differences in the concentrations of ions
What are the 2 types of gradients created by the different ion concentrations that determine membrane potential’?
Concentration gradients
Electrical gradients
What are the main ions that contribute to membrane potentials? Include their charge and their location of highest concentration
Na: + extracellular K: + intracellular Ca: + extracellular Cl: - extracellular Anions: - intracellular
What are anions made of?
Protein
PO4
What pump is the sodium gradient maintained through?
Na/K ATPase
How does the Na/K ATPase pump work?
It removes 3 Na in exchange for 2 K and contribute -4 mV to the membrane potential
What would happen if the balance of Na significantly differed form inside to outside?
The cell would shrink or swell
Which ion is the most important to be able to diffuse across the membrane? What is its equilibrium potential?
Potassium
-96.81 mV
Which ion is so tightly regulated it cannot diffuse through the membrane? What is its equilibrium potential?
Calcium
+137.04 mV
What is the resting potential for the neuronal membrane?
-70 mV
What does the membrane potential allow the neuron, dendrites, and axons to have?
Excitable membranes so they can transmit signals
Where is the trigger zone (Dr. Beasley’s favorite area)located?
At the axon hillock
What must happen in order to transmit an action potential?
You must reach the threshold to stimulate the axon
What is the membrane potential of the trigger zone?
Between -40 mV and -55 mV
Does a depolarization make the membrane potential more positive or negative?
Positive
Does a hyper polarization make the membrane potential more positive or negative?
Negative
What are the steps of action potential?
Threshold is reached, making depolarization self-generating via graded potentials
This triggers opening of the activation gates of the voltage gated Na channels, which are open for a predetermined amount of time until the inactivation gates close
Sodium rushes into the cell down its potential making the membrane on the inside more positive
This triggers neighboring voltage gated sodium channels to open propagating the action potential, but only in the direction of axon flow because of the absolute refractory period
The voltage gated potassium channels open and the potassium rushes out down its concentration gradient
The membrane becomes extra negative as too much potassium leaves the cell, which creates a hyperpolarized membrane potential
To reach the threshold potential to create a new action potential, you have to get from hyperpolarized membrane to the threshold at -40 to -55 mV
The Na/K ATPase pumps kick into high gear to get the Na out of the cell and the K back in returning the membrane to its resting membrane potential
What is the hyperpolarized membrane potential?
-80 to -90 mV
More simply put, what does the action potential consist of?
Depolarization, repolarization, hyperpolarization
Where does myelin live?
On the axons
What creates myelin in the CNS?
Oligodendrocytes
What is the ratio of oligodendrocytes to axons?
1:many
What creates myelin in the PNS?
Schwann cells
What is the ratio of Schwann cells to axons?
1: 1 myelinated
1: many unmyelinated
What does myelin do?
Protection of the axon
Electrically insulating fibers from one another
Increasing the speed of nerve impulse transmission
Which axons are affected first with spinal cord compression?
Large, heavily myelinated fibers
What is the last function lost with severe spinal cord compression/disease?
Tactile sensation/deep pain
What does the loss deep pain mean for prognosis for return to function?
It is 50:50 or less than 20% depending on time
Where do synapses occur?
Axon terminals
What happens as the action potential reaches the axon terminal?
The change in membrane potential opens voltage gated Ca channels
What does the calcium from a change in membrane potential cause?
Synaptic vessels to fuse with axon membrane and exocytosis of neurotransmitter into the synaptic cleft
Which variety are the receptors on the post synaptic membrane?
Ligand
What ion do the ligand receptors on the post synaptic membrane allowing into the post synaptic cell?
Na
What happens if enough Na enters the post synaptic cell?
It triggers the opening of the voltage gated Na channels and get triggering of an action potential
What happens with signals at the synapses?
You are taking an electrical signal, turning it into a chemical signal and then back to an electrical signal
What are the 3ways to remove neurotransmitters from the synaptic cleft?
Diffusion
Re-uptake
Degradation of enzymatic destruction
What is involved in re-uptake?
Active transport into presynaptic neuron
Active transport into astrocytes
What do excitatory post-synaptic potentials do?
Depolarizes membrane potential a little
What happens when the membrane potential depolarizes a little? Does this make the membrane more positive or negative?
Opens Na channels
Positive
What do inhibitory post-synaptic potentials do?
Hyperpolarizing the membrane potential a little
What happens when the the membrane potential hyperpolarizes a little? Does this make the membrane more positive or negative?
Opens Cl channels
Negative
What must a neurotransmitter do to be considered a neurotransmitter?
Substance must be present within presynaptic neuron
Substance must be released in response to presynaptic depolarization and must be Ca dependent
Specific receptors for the substance must be present on post-synaptic cell
Which would mimic the action of a neurotransmitter by binding to its receptor, agonist or antagonist?
Agonist
Who are the major excitatory neurotransmitters? What ion enters through their ligand gated channels?
Acetylcholine (Na)
Glutamate (Ca and Na)
Epinephrine, norepinephrine, dopamine, serotonin, and histamine
Who are the major inhibitory neurotransmitters? What ion enters through their ligand gated channels?
Gamma-amino butyric acid (GABA) (Cl)
Glycine (Cl)
Where are nicotinic receptors found?
Neuromuscular junction in preganglionic ANS
Who binds to nicotinic receptors?
Acetylcholine
Where are muscarinic receptors found?
Postganglionic parasympathetic nervous system
Who binds to muscarinic receptors?
Acetylcholine
What degrades acetylcholine?
Acetylcholinesterase
What neurotransmitter do we believe is responsible for excitotoxicity following head trauma?
Glutamate
What neurotransmitters are affected in tetanus?
GABA and Glycine
What nuerotransmitters are affected with strychnine toxicity?
Glycine
What are the neurotransmitters and receptors of the post-gnaglion neurons of the SANS?
Norepinephrine and epinephrine
Alpha and beta receptors
What neurotransmitter has agonist created to be anti-seizure medications?
GABA
Which neurotransmitters are often manipulated for behavior modification?
Serotonin, dopamine, and histamine
What nerve is involved in the patella reflex? Where does it live in the spinal cord?
Femoral nerve
L4 and L5
What nerves are involved in withdrawal in the hindlimbs?
L4-S3
Stifle and hock: Sciatic nerve (L6, L7, S1)
What nerves are involved in withdrawal in the forelimbs?
Musculocutaneous (C6-8) Axillary (C7-8) Radial (C7-T1) Median (C8-T1) Ulnar (C8-T1)
Which diffuse LMN disease affects the cranial nerves as well as the peripheral nerves?
Botulism
What is attacked and its location in coonhound paralysis? What is the grown up term for this disease?
Myelin fibers of the ventral nerve roots
Polyradiculoneuritis
What animals are most prone to botulism? Which are least susceptible?
Horses and cows
Dogs, cats, and pigs
Why does treating an animal with myasthenia gravis with an anticholinesterase inhibitor work?
Leaves Ach in synaptic cleft so it can find the Ach receptors not attacked by antibody and internalized
What would happen in an overdose of anticholinesterase (similar to OP toxicity)?
SLUTD
What ticks cause tick paralysis in the US?
Dermacenter ticks
What nerve results in a dropped elbow when damaged?
Radial nerve
What nerve results in a dropped jaw when damaged?
Mandibular branch of trigeminal nerve
What is an axon belonging to an UMN called?
Tract
What is an axon belonging to a LMN called?
Nerve
What does UMN usually synapse on, interneuron or LMN?
Interneuron
What tracts are the exceptions to UMN synapsing on interneurons?
Corticospinal and vestibulospinal
Which is better for a function recovery after neuronal cell loss, interneuron or LMN?
Interneuron
Are any descending motor tracts in the dorsal funiculus?
No, they are only ascending
What do tracts in the lateral funiculus do and what phase of the gait is this?
Flex
Swing phase
What tracts are in the lateral funiculus?
Lateral corticospinal
Rubrospinal
medullary reticulospinal
What do tracts in the ventral funiculus do and what phase of the gait is this?
Extensor
Support/stance/protraction
What tracts are in the ventral funiculus?
Vestibulospinal
Pontine reticulospinal
Ventral corticospinal
What is the exception to tracts in the ventral funiculus doing extensors?
Ventral corticospinal
I have a dog who cannot move his back legs at all but still feels his feet, how would you tell me what this is?
Paraplegic, deep pain positive
I have a dog that can walk but it is very ataxic in all four limbs and can feel his feet, how would you tell me what this is?
Ambulatory tetraparetic
What are the 3 pyramidal tracts?
Corticopontine
Corticonuclear
Corticospinal
Which of the pyramidal tracts allow cerebellar input?
Corticopontint
What peduncles are involved in cerebellar input?
Middle afferent
Rostral efferent
Which pyramidal tracts control LMN in the spinal cord?
Corticospinal
What of the corticospinal tracts decussates at the pyramidal decussation?
Lateral
Which pyramidal tract control LMN in the brainstem?
Corticonuclear
Which pyramidal tract does not make it to the pyramids?
Corticopontine
What mammals have the best developed pyramidal tracts?
Primates
Raccoon
Horse
Cat
Where are extrapyramidal UMN located?
MIdbrain
Pons
Medulla
Which extrapyramidal tracts decussates? Which do not?
Decussates: Rubrospinal
Does not: Pontine, medullar reticulospinal, and vestibulospinal
What are the 4 basal nuclei?
Caudate
Putamen
Globus pallidus
Claustrum
Which of the 4 basal nuclei is located medial to the internal capsule?
Caudate
What nucleus influences the neostriatum? What does it release?
Substantia nigra
Dopamine
What nucleus does the lateral globus pallidus influence?
Subthalamic
Who talks to the thalamus?
Medial globus pallidus
Who influences the medial globus pallidus?
Neostriatum (caudate and putamen, subthalamic nucleus and lateral globus pallidus)
What are the 3 kinds of ataxia?
Spinal/proprioceptive
Vestibular
Cerebellar
What ataxia is often found with weakness?
Spinal
A lesion in the medulla on the right side would cause deficits on which side of the body?
Right
A lesion in the cerebral cortex on the right side would cause deficits on which side of the body?
Left
Which results in increased extensor tone or spasticity, LMN or UMN?
UMN
Which would cause increase in the reflexes, LMN or UMN?
UMN
Damage to what areas of thee spinal cord will result in UMN signs, only to the hindlimbs?
T3-L3
Damage to what area of the spinal cord could create LMN signs in the forelimbs? Hindlombs?
C6-T2
L3-S3
Damage to what area of the spinal cord would result in UMN signs to all 4 limbs?
C1-C5
What are the 2 types of LMNs?
Alpha and gamma
What are intrafusal muscles also known as?
Muscle spindles
What is the afferent axon from golgi tendon organs? Where do these receptors live?
1b
Tendons
If the body wants to contract a muscle spindle, which LMN is involved?
Gamma
What is the afferent axon from muscle spindles?
1a
What LMN do afferent axons from muscle spindles innervate?
Alpha
What reflex is the simplest using just the afferent axon and LMN?
Femoral/patella
An UMN creates muscle tone through innervating what LMN?
Gamma
Eliciting a flexor reflex in an animal with UMN disease can produce what?
Hyper reflexia
Crossed extensor
What reflex can help to localize the are of spinal cord injury to the vertebra and not just functional spinal cord divisions?
Cutaneous trunci
What nerve is involved in the reflex that can help to localize the are of spinal cord injury to the vertebra and not just functional spinal cord divisions? Muscle?
Lateral thoracic
Cutaneous trunci
Where do the LMN of the lateral thoracic nerve and cutaneous trunci live in the spinal cord?
C8-T1
What nerve are involved in the perineal reflex?
Pudendal, caudal
Would a dog with an injury to just the sacrum be able to walk?
Yes
What allows a dog to with a functional or anatomic transection of the spinal cord to walk?
Central pattern generators
Would a dog “walk” with a T3-L3 lesion?
Yes
Would the dog “walk” with a L3-S3 lesion?
No
I have a dog with paraplegia (UMN) but increased extensor tone in the forlimbs, where could the lesion be in the spinal cord? What disease is this?
T3-L3
Schiff Sherrington
What are the 3 layers of the cerebellar gray matter?
Molecular
Purkinje
Granule
What is the least cellular layer of cerebellar gray matter?
Molecular
Describe the purkinje layer of the cerebellar gray matter
Contain purkinje cells
Release GABA neurotransmitter
Synapse on Deep Cerebellar nuclei
Describe the granule layer of cerebellar gray matter?
Contain granule cells, which are excitatory, and golic cells, which release GABA and are inhibitory
What are the 2 fibers that ascend into the cerebellum?
Mossy
Climbing
Describe mossy fibers
Excitatory
Make up the MCP from the pontine nuclei from the corticopontine tract
Synapse on DCN
Granule cells and golgi cells
Describe climbing fibers
Excitatory with aspartate
Synapse on DCN and molecular layer
From olivary nucleus
What are the peduncles?
Rostral
Middle
Caudal
Which peduncle is mainly output?
Rostral
What are the signs of cerebellar disease?
No loss of strength/weakness
Hypermetria
Intention tremors
Ipsilateral menace deficits
What is supposed to be the only source of output from the cerebellum?
Deep cerebellar nuclei
What do purkinke cells of flocculonodular lobes synapse on?
Directly on the vestibular nuclei througn the CCP
What makes up the deep cerebellar nuclei?
Fastigial
Interposed
Dentate
Describe fastigial nucleus
Associated with vermis (spinocerebellum) and vestibulo cerebellum
Describe interposed nucleus
Intermediate zone (spinocerebellum)
Describe dentate nucleus
Hemisphers, cerebrocerebellum, RCP
What are the nerve endings/types for proprioception?
Pacinian corpuscle Ruffin's corpuscle Muscle spindles Golgi tendon organs Joint receptors
Where is a good dermatome for testing the radial nerve?
Front of radius/ulna
What pathway transmits proprioceptive/non-painful sensation?
Medial meniscus
Where does the medial meniscus travel in the spinal cord?
Dorsal funiculus
What pathway transmits pain signals?
Spinothalamic
Where does the spinothalamic pathway in the spinal cord?
Lateral funiculus
What conditions result in extensor rigidity?
Decerebrate rigidity
Decerebellate rigidity
Schiff Sherrington
Which condition that results in extensor rigidity affects the patient’s sensorium?
Decerebrate rigidity
