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121 Cards in this Set
- Front
- Back
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What is a circumscribed collection of neurons in the CNS called? Outside the CNS?
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Nucleus
Ganglion |
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Where does the spinal cord terminate in the dog? In the horse? How about humans?
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L6 - dog
S2 - horse L2 - humans |
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Where is CSF located with respect to the meninges?
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Subarachnoid space
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Where is the lumbar cistern in dogs? In cats? In the horse? Cow? Sheep? Pig?
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Dog/cat - L5/L6 (+/- 1)
All others - lumbosacral space |
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In which of the 5 brain regions would the reticular formation be found?
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Mylencephalon, metencephalon, mesencephalon, diencephalon (?)
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In which of the 5 brain regions would the pineal gland, facial nerve, and olfactory bulb be found?
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Pineal - diencephalon
Facial - myelencephalon Olfactory - telencephalon |
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In which of the 5 brain regions would the oculomotor n., corpus callosum, lateral ventricles be found?
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Oculomotor - mesencephalon
corpus and ventricles - telencephalon |
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In which of the 5 brain regions would the substantia nigra, red nucleus, and optic nerve be found?
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nigra and red - mesencephalon
Optic n. - diencephalon |
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In which of the 5 brain regions would the hypothalamus, middle cerebellar peduncles, and fourth ventricle be found?
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hypo - diencephalon
peduncles - metencephalon ventricle - metencephalon and mylencephalon |
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In which of the 5 brain regions would the hippocampus, caudate nucleus, and cerebral peduncles be found?
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hippo and caudate - telencephalon
peduncles - mesencephalon |
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What is the principal structure responsible for the blood/brain barrier? Blood/csf barrier? brain/csf barrier?
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Blood/brain - tight junctions of endothelial cells of capillaries
Blood/CSF - choroid epithelial tight junctions Brain/CSF - ependymal cells and glial membrane |
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Which structures comprise the limbic system?
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Amygdala, hippocampus, pyriform lobe, septal area, anterior nucleus of the thalamus
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Which spinal cord segments lie within the 5th lumbar vertebra of a dog?
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Caudal L7, S1 - S3
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Which spinal cord segments contain LMNs for the thoracic limb in the cat and dog?
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C6 - T1
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Which spinal cord segments supplies the pelvic limbs? How 'bout the pelvic cavity?
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Limbs - L4 - S2
Cavity - S1 - S3 |
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What are the three types of efferent neurons and what do they innervate?
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Alpha - sleketal muscle
Beta - smooth, cardiac muscle, and glands Gamma - muscle spindle |
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What is the rate of axonal regrowth? What is the critical timeframe of regrowth before a neuron will completely die?
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1mm/day or 1in/month
1 year is critical |
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T or F
In a hyperpolarized neuron, membrane potential is more negative than the normal RMP. |
True!
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When a nerve cell becomes hyperpolarized, in what direction do K ions flow?
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Into the cell
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T or F:
Increasing stimulus strength to 5x over threshold increases the rate of depolarization and the amplitude of the signal. |
False! It does increase the depolarization rate but the amplitude (overshoot height) remains the same.
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What provides the electrostatic force keeping K ions within the cell?
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Protein anions within the cell.
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What two factors allow for cell repolarization after an AP is initiated?
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Close Na gates
Efflux of K |
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What is the major cause of the rapid depolarization phase of an AP?
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Opening of Na gates (Na influx)
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What two factors determine the length constant of a nerve?
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Degree of myelination
Radius of fiber |
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Which type of fiber conducts signals the fastest? Which is the slowest?
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A alpha (Ia and Ib)
C (pain fibers) |
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Which type of fiber is most susceptible to local anesthetics? To hypoxia? To pressure?
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C - anesthetics
B - hypoxia A - pressure |
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Classify A, B, and C fibers by whether they are afferent or efferent.
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A - afferent and efferent
B - efferent C - efferent and afferent |
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What are some advantages of saltatory conduction in a mammal?
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Metabolic efficiency (use less ions)
Increase conduction speed (ion exchange only occurs at internodes) |
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What is the main neurotransmitter used for nociception? What neurotransmitter inhibits it? What is this inhibition called?
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Substance P (inhibited by enkphalins through presynaptic inhibition)
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How is Ach inactivated in the synaptic cleft?
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Cholinesterase breaks it down into choline and acetate. These are resorbed by the presynaptic membrane.
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Where are electrical synapses found?
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Eye and cerebral cortex; also invertebrates
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What is the major difference between an EPP and an EPSP.
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An EPP occurs within a muscle cell while an EPSP occurs at a synaptic cleft.
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T or F:
An EPP is actually made up of multiple (sometimes hundreds) of MEPPs. |
True!
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How does an IPSP make a neuron less able to fire an AP? (i.e. what subcellular mechanisms are involved)?
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Increase permeability of K and Cl
Hyperpolarize the cell |
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What NT is released by Renshaw cells? By preganglionic sympathetic neurons? At the neuromuscular endplate?
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Glycine
Ach Ach |
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Which NT is antagonized by LSD? An axo-axonic inhibitory neurotransmitter? The most common excitatory NT?
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Serotonin
GABA or Enkephalin Glutamate |
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Which NT is associated with addiction? Produced by Substantia nigra? Antagonized by strychnine?
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Dopamine
Dopamine Glycine |
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Which neurotansmitter is the postganglionic sympathetic NT? Is made by raphe nuclei? Is associated with the locus ceruleus?
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NE
Serotonin NE |
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Which NT is associated with the hippocampus and alzheimers? The NT of pain fibers? Released by substantia gelatinosa cells?
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Ach
Substance P Enkephalin |
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Which NT is inhibited by botulism toxin? Has gallamine as an agonist?
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Ach
Ach |
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Where does botulism toxin have its effect?
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Binds to Ca preventing Ach release at NM junction, preventing muscle contraction
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What is the difference between strychnine and tetanus toxins? who's reversible?
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both affect Renshaw cells
Tetanus inhibits the Renshaw cells directly Strychnine binds to glycine receptors to block renshaw activity tetanus is irreversible, strychnine is reversible |
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How does Atropine work?
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Blocks Ach at postsynaptic receptor
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What are the nondepolarizing NM blocking agents and how do they work?
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Curare and Gallamine
competes with Ach for receptors |
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What drug is used in short term equine anesthesia?
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Succinylcholine
depolarizes muscles so they cant' repolarize until it's cleared Does not deaden pain. |
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Name some cholinesterase inhibitors. Which are irreversible?
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Neostigmine
Physostigmine parathion (irreversible) malathion (irreversible) dichlorovos (irreversible) nerve gas (irreversible) |
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Which drugs impact GABA and how?
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Valium - increase GABA effectiveness
Ivermectin - GABA agonist |
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Which receptors convey unconscious proprioception? To where do they send their information?
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muscle spindle and golgi tendon organs send info to the cerebellum
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Compare/contrast lesions of UMNs and LMNs.
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Both lack voluntary movement.
UMNs have reflex; LMNs have no reflex. |
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How is the excitatory state of LMNs modulated?
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Through EPSPs and IPSPs. Increased EPSPs = excitation; increased IPSPs = attenuation.
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Which of the following species has flow from the basilar artery contributing to the brain arterial supply?
Horse, dog, cow, sheep, cat |
Horse and dog
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Which space in the brain does NOT produce CSF?
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Cerebral aqueduct
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Which spinal cord segments originate under L3? Under L5?
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L3 - L3 and cranial L4
L5 - Caudal L7, S1 - S3 |
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Which spinal cord segments originate under L4? L6?
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L4 - caudal L4, L5, L6, cranial L7
L6 - Ca 1-5 |
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Spinal cord segments T2 - L3 are responsible for which region(s) of the body? How about C1 - C5?
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Sympathetic outflow and muscles of respiration.
Neck meat. |
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What are the 5 segments or zones of neurons? Which are graded in their response?
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Receptive (graded)
trigger zone conductile transmissive (graded) trophic |
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T or F:
An EPP always results in depolarization. |
True!
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What is the formula for length constant? Which factor is important in mammals? In invertebrates?
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((membrane resistance x radius)/(2 x axoplasm reistance))^0.5
Mammals modulate membrane resistance while invertebrates change radius. |
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Give examples of presynaptic inhibition.
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Enkaphalins (from substantia gelatinous cell) inhibit substance P release (from nocioceptive fiber).
GABA inhibits DA release. |
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Name a phasic receptor and a tonic receptor.
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Phasic - pacinian corpuscle
Tonic - joint receptor |
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What is the rate-limiting step in catecholamine synthesis?
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Tyrosine Hydroxylase
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evolutionary levels of the cerebral cortex
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archicortex--hippocampus
paleocortex--primitive olfactory bulb neocortex--cerebral cortex |
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neurons reaction to injury?
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swelling of cell body, nucleus, and nucleolus
displacement of nucleus (eccentric) dispersal of nissl's substance (this happens no matter what part of the nerve is injured, axon, dendrite, whatever) |
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what happens is a peripheral nerve is severed?
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wallerian degeneration:
axon becomes beaded and microglia phaocytize it and the myelin around it degeneration happens back to the first unaffected node of ranvier |
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what is gliosis?
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proliferation of astrocytes in damaged areas of the CNS
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neuroma
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painful mass of twisted axons from faulty regrowth
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what is the pathogenesis of spina bifida? anencephaly?
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the backbone and spinal canal don't close before birth due to failure of caudal neural tube closer
failure of skull bones to close and being |
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where does cn 5 come from in the brain?
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pons
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where do cn 3-4 come from?
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midbrain
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where do cn 6-12 come from?
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medulla
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how do spinal nerves exit their respective vertebra?
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exit behind similarly numbered vertebrae except in the neck where they exit before their numbered vertebrae
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areas of brain most susceptible to anoxia
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cerebral cortex and cerebellum
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what is the conus medullaris?
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end of the spinal cord
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what is the cauda equina?
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the collection of nerves after the spinal cord ends
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which region of the functional regions of the spinal cord supplies the sympathetic system and respiration?
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T2-L3, called the thoracic and cranial lumbar
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which functional region of the spinal cord supplies the pelvic limbs?
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lumbosacral/lumbar enlargement! L4-S2
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which functional region of the spinal cord supplies the thoracic limb and diaphragm?
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brachial enlargement C6-T1
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what is the rete mirable?
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a venous network found in the head of most species that cools the blood before it enters the brain
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in what species does the basilar artery run caudally?
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sheep, cat, and ox
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what is the primary blood supply to the brain in the dog? secondary? what's so special about it?
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maxillary, basilar and internal carotid
it has the greatest ability to develop collateral circulation (multiple pathways to supply the brain) |
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what is the only blood supply to the sheep and the cat? why, don't they have a basilar artery?
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maxillary
yes, but it runs caudal |
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what is the blood supply to the brain of an ox?
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maxillary and vertebral
so, if you slice common carotid maxillary bleeds out but vertebral still keeps them concious |
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where is csf absorbed?
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arachnoid villi
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who supplies blood to a horse's brain?
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internal carotid and basilar
basilar flows towards the brain! hooray! only the horse and the dog have it flowing cranially |
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what are the arteries that drain from the circle of willis?
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rostral cerebral artery
middle cerebral artery caudal cerebral artery rostral cerebellar artery caudal cerebellar artery |
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what are the three functions of the reticular formation?
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arousal (ascending)
center for homeostasis tells gamma efferent what to do |
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what type of fibers are Ia?
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Alpha fibers from primary ending muscle spindle (afferent)
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what type of fibers are Ib?
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alpha fibers from golgi tendon organs (afferent)
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what are the four topographic types of syanpses?
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axo-axonic
axo-dendritic axo-somatic dendodendritic |
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what is an EPP?
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end plate potential--a depolarization in the muscle cell from a motor neuron, always excitatory in healthy muscle
depol. due to Na and K influx/efflux |
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what is an IPSP?
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inhibitory postsynaptic potential
neuron releasing an NT on a postsynaptic cell to hyperpolarize it (Cl influx or K+ efflux) |
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what is an EPSP
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excitatory pre synaptic potential
neuron releasing a NT on a postsynaptic cell to depolarize it slightly (excitatory) increases |
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what is presynaptic inhibition?
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the reduction of transmitter release from a presynaptic terminal (rather than affect the postynaptic membrane)
presynaptic is longer than postynaptic |
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what is quanta?
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a fixed amount of NT
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what is an MEPP?
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spontaneous depolarizations in post-synaptic membrane caused by spontaneous release of quanta from presynaptic terminal
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what is spatial summation?
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many presynaptic fibers on a neuron, causing multiple EPSPs and an AP
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what is temporal summation?
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a single synapse firing multiple times very rapidly causing an AP
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neuron-neuron synapses vs neuromuscular junction
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neuron-neuron has EPSPs, individually they're subthreshold
neuromuscular junction has EPPs, suprathreshold |
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factors that determine how influential a synapse is on another neuron or muscle
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duration ad quantity of NT released (Ca availability)
size of synaptic area membrane resistance of postynaptic cell (size) excitatory or inhibitory number of synapses distance to axon hillock (hillock= lowest threshold) firing rate |
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criteria of NT classification
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has to be made and stored in presynaptic neuron
has to be released when terminal is activated has to mimic effect of synaptic activityhen applied to post synaptic membrane artificially must have a removal mechanism in the cleft |
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what NTs are classified as monoamines? cholinergic? catecholamines?
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dopamine and histamine
Ach norep, ep, serotonin |
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what is axoplasmic flow?
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2 directional flow of components necessary to maintain an axon
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how fast is slow axoplasm flow and what direction does it move in? fast?
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1mm/day, only anterograde
10-20cm/day, both anterograde and retrograde |
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why is axoplasmic flow important?
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growth rate of neurons
we think rabies and tetanus gets up axons this way |
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how does reserpine work?
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it depletes stores of DA and NE, used to illegally calm horses
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how does curare works?
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binds competitively with Ach rececptors in NMJ to prevent muscle contraction
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how does gallamine work?
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used as a muscle paralyzer, uses for heart/lung ****
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what are the physiochemical energies that serve as stimuli?
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thermal energy (heat or lack of it)
mechanical energy electromagnetic energy (light) mechanical energy chemical |
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what is a specific/adequate stimuli
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the stimuli that a receptor most readily responds to and requires least amount of energy to start a nerve impulse
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threshold stimulus
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the least amount of energy required to start a nerve impulse
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effective stimulus
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different forms of energy that can act on a receptor and cause APs (some receptors can respond to multiple stimuli)
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generator potential
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a change in membrane potential caused by a stimulus, is proportional to signal strength
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adaptation
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the decrease of generator potential as a constant stimulus is being applied
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name the 3 types of receptors classified by location
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exteroreceptors--on body wall surface, cutaneous
proprioreceptors--in muscle and tendons enteroreceptors--sensory from viscera |
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name receptors classified by stimuli
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mechanoreceptors--detect deformation
thermoreceptors--detect changes in temperature nociceptors--detect noxious/harmful stimuli electromagnetic--detect light on retina chemoreceptors--taste, smell, osmolality of body fluids |
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sensory modalities include
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pain, warm, cold, taste, hearing, sight, smell
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what is unconcious proprioception?
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signals from receptors in muscle spindles and golgi tendon organs, is what goes to your cerebellum
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what is concious proprioception
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knowing where your body is in space, travels to cerebral cortex (from mechanoreceptors)
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what are phasic receptors?
example? |
rapidly adapting receptors that respond to a signal starting or stopping, can't transmit info of constant stimuli
pacinian corpuscle |
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what are tonic receptors?
example? |
slowly adapting receptors that continuously transmit action potentials as long as the stimulus is present (minutes or hours)
muscle spindles |
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chain of events from touching a receptor to stimulating peripheral nerve
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stimulus depresses corpuscle-->na influx-->generator potential-->flow of current to first node of ranvier-->if strong enough to reach threshold, AP results-->moves along nerve fiber
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