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Clinical Neuro > Functional Neuroanatomy & The Exam > Flashcards

Functional Neuroanatomy & The Exam Flashcards

1
Q

What is the resting membrane potential for a large nerve fiber?

A

-90 millivolts

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2
Q

What happens when you have a calcium deficit?

A

Causes Na+ channels to become activated with little increases in membrane potential, leading to a very excitable nerve (ie. Tetany)

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3
Q

What is the threshold for stimulation of an action potential?

A

-65 mV

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4
Q

What 3 things result in the inhibition of excitability?

A

High extracellular Ca (decr membrane permeability to Na), local anesthetics (Na channel blockers), when AP strength to excitability threshold = <1

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5
Q

What are the different cells that form myelin for the CNS and PNS, and what is the clinical significance of this?

A

CNS: oligodendroglial cell processes; PNS: rolled up Schwann cell membrane; different populations of cells > get different cancer manifestations

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6
Q

The amount of Ca inflow from voltage-gated Ca channels on the presynaptic membrane after an AP depolarizes it is directly related to what?

A

Transmitter release

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7
Q

What are the two types of ion channels located on the postsynaptic neuron?

A
  • Cation channels (allow Na ions to enter, excitatory)
  • anion channels (allow Cl ions to enter, inhibitory)
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8
Q

What is occurring during excitation of a postsynaptic receptor?

A
  • Opening Na channels
  • decr conduction thru Cl/K channels (both raise intracellular membrane potential towards zero)
  • internal metabolic changes to excite cell activity
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9
Q

What is occurring during inhibition of a postsynaptic receptor?

A

Opening of Cl channels, incr K out of neuron (both make the intracellular membrane potential more negative), activation of receptor enzymes to inhibit cellular activity

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10
Q

How do small-molecule neurotransmitters differ from neuropeptides and what are some examples of each?

A

Small molecule NTs are rapidly acting, while neuropeptides are slow acting or they are growth factors that have central and long-acting effects

  • Small: ACh, NE, Epi, GABA, Glycine, Glutamate
  • Neuropeptides: ACTH, GH, Insulin, Glucagon, Angiotensin
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11
Q

Describe acetylcholine

A
  • Acetyl coenzyme A + choline
  • transported into vesicles
  • released into cleft
  • rapidly split into acetate/choline by cholinesterase in cleft
  • choline actively recycled
  • usually excitatory (inhibitory in some PS nerve endings ie. Vagus)
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12
Q

What is a condition in which the patient has adequate ACh, but doesn’t have enough receptors for it to bind to?

A

Myasthenia gravis

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13
Q

Describe norepinephrine

A

Synthesized in the adrenergic nerve terminal (tyrosine>dopa>dopamine), transported into vesicles> dopamine to NE

Removal: active reuptake into adrenergic endings, diffusion away, enzymatic destruction (ie. monoamine oxidase)

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14
Q

An excitatory postsynaptic potential does what to elicit an action potential?

A

Incr Na permeability, neutralizing the RMP, and requires a discharge of many terminal at once or in sequence (spatial vs. temporal summation)

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15
Q

Inhibitory postsynaptic potentials do what to prevent the generation of an action potential?

A

Open Cl channels > Cl in and/or K out, incr negativity in the cells (hyperpolarization)

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16
Q

What occurs with presynaptic inhibition?

A

Release of inhibitory substance (GABA) onto presynaptic fibrils > cancels effect of sodium influx; occurs in many sensory pathways to minimize sideways spread

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17
Q

What is the effect of fatigue on synaptic transmission?

A

Decrease in discharge of postsynaptic neuron

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18
Q

What is the effect of pH on synaptic transmission?

A

Alkalosis increases excitability, acidosis depresses it

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19
Q

What are the effects of caffeine, theophylline and theobromine on synaptic transmission?

A

Reduce threshold for excitation

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20
Q

What are the effects of strychnine on synaptic transmission?

A

Inhibits glycine (inhibitory NT) in spinal cord, causing excitation/tetany

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21
Q

What are the effects of anesthetics on synaptic transmission?

A

Anesthetics increase threshold for excitation, decreasing transmission

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22
Q

Describe the process of skeletal muscle excitation

A

Mostly Na enters the muscle fiber, creating a local positive potential in the muscle fiber (the end plate potential)

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23
Q

When does fatigue occur at neuromuscular junctions?

A

Stimulation of the nerve >100x/second for minutes depletes ACh vesicles, so impulses fail to pass, resulting in fatigue

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24
Q

What 3 drugs stimulate the muscle fiber by ACh-like action and are long-lasting because they are not broken down by cholinesterase?

A

Methacholine, carbachol, nicotine > can result in long-lasting toxicities

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25
Q

What are 4 drugs that stimulate the NMJ by inactivating acetylcholinesterase?

A

Neostigmine, physostigmine, diisopropyl, fluorophosphate > cause muscle spasm

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26
Q

What type of drugs block transmission at the NMJ?

A

Curariform drugs; e.g. D-tubocurarine blocks ACh on the receptor, preventing AP

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27
Q

Describe the process going on during skeletal muscle contraction

A

AP travels along a motor nerve to the NMJ > nerve secretes ACh > opens ACh-gated channels > Na diffuses in, intimating AP > AP travels along muscle membrane, T tubules > AP depolarizes muscle, causing SR to release Ca > Ca intimates actin and myosin sliding > Ca pumped back into SR, stopping contraction

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28
Q

What is the function of transverse or T-tubules in skeletal muscle?

A

Skeletal muscle fibers are too large for surface AP to cause current flow deep in the muscle, so T tubules penetrate all the way through, acting as internal extensions of the muscle membrane

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29
Q

Ca is pumped back into the SR and bound by what molecule?

A

Calsequestrin

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30
Q

What are some characteristics of smooth muscle structure?

A

Can be multi-unit or unitary, have dense bodies, not Z-discs, have slow myosin head cycling (less ATPase activity and lower energy requirements), and have calmodulin, but no troponin

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31
Q

Describe smooth muscle action potentials

A

APs are typically a spike, but those with plateaus account for prolonged contraction, and they have many voltage-gated Ca and few Na channels

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32
Q

Describe the concept of slow wave potentials in smooth muscle

A

Some smooth muscle is self-excitatory, and APs can be generated by stretch/can get contraction without AP in small fibers

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33
Q

All autonomic preganglionic neurons are what type?

A

Cholinergic; ACh is excitatory to all postganglion neurons

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34
Q

Most parasympathetic postganglionic neurons are what, compared to what most sympathetic postganglionic neurons are?

A

PS: cholinergic; S: adrenergic

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35
Q

Where would you find muscarinic receptors vs. nicotinic receptors?

A

M: on all effector cells stimulated by postganglionic cholinergic neurons of S/PS systems

N: in autonomic ganglia at synapses b/t pre- and postganglionic neurons of S/PS systems; NMJs

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36
Q

Describe a reflex arc

A

polysynaptic w/ multiple inter neurons more common

  • receptor endings of primary afferent axon > cell body in DRG > synapses on efferent neuron in ventral horn > motoneuron axon passes out into spinal nerve to effector organ
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37
Q

Describe alpha/skeletomotor neurons?

A

Innervate oridinary (extramural) skeletal muscle fibers; large diameter myelinated axon > fast conduction

38
Q

Describe fusimotor (gamma) neurons

A

Innervate intrafusal muscle fibers (part of the muscle spindle), and are thin myelinated axon, so slower conduction

39
Q

Describe intrafusal muscle fibers

A
  • No actin/myosin centrally
  • fusimotor (gamma) neurons innervate end-portions
  • detects stretch
  • rate of firing related to degree of stretch
40
Q

What is the difference between alpha, gamma, and interneurons?

A
  • Alpha - innervate sk mm, single fiber + all mm fibers it innervates = motor unit
  • Gamma = transit impulses thru smaller nerves, intrafusal mm fibers to control mm tone
  • Interneurons = present in spinal cord gray matter, renshaw cells - lateral inhibition of motor neurons
41
Q

Define lower motor neuron

A

The efferent neuron of the PNS that connects the CNS with the muscle to be innervated

42
Q

What nerves constitute general somatic efferent (GSEs)

A
  • Striated skeletal muscle
  • all spinal nerves
  • CN II, IV, V, VI, VII, IX, X, XI, XII
43
Q

What nerves constitute general visceral efferent (GVEs)

A
  • Innervate smooth and cardiac mm and glands
  • sympathetic: all spinal & splanchnic nerves
  • PS: sacral spinal nerves, CN III, VII, IX, X, XI
44
Q

What sections of the brain does the forebrain include?

A
  • Cerebrum (telencephalon):
    • cerebral cortex (frontal, piriform, parietal, temporal, occipital lobes)
    • hippocampus
    • basal nuclei
  • Diencephalon: thalamus, hypothalamus
45
Q

What does the midbrain (mesencephalon) contain?

A

CN III, CN IV, rostral and caudal colliculi

46
Q

What will you find within the rostral fossa and caudal fossas, and what structure lies between these 2 fossas?

A

Rostral: cerebrum, dienceophalon

Caudal: cerebellum, brainstem, midbrain

  • separated by the tentorium cerebellum
47
Q

What is the difference between upper and lower motor neurons?

A

UMN: starts in the brain and goes down spinal cord to synapse on motor neuron

LMN: comes from SC and goes to the periphery

48
Q

What are LMN signs?

A
  • Loss of reflexes
  • loss of tone
  • paresis to paralysis (motor deficit); weak and floppy
49
Q

What are upper motor neuron signs?

A
  • normal to increased reflexes
  • increase in tone
  • paresis to paralysis
  • weak and stiff
50
Q

What is the purpose of the ascending reticular activating system?

A

Directs all the sensory info coming into your body towards the brain and SC, which is relayed through the thalamus and projected constantly up to the cortex to stimulate and keep you awake (where caffeine works)

51
Q

What tracts will you find in the dorsal vs. the ventral and lateral columns of the spinal cord?

A

Dorsal = sensory

Ventral/lateral = motor

52
Q

How does the information regulating conscious proprioception make it to the brain?

A
  • Travels from distal receptors up the peripheral nerve, then up the SC via the dorsal funiculi.
  • These tracts are ipsilateral until they decussate at the level of the pons before radiating to the cortex
53
Q

How do postural responses differ from reflexes?

A

Responses not reflexes b/c must travel to the brain, be interpreted, then acted upon with the resultant physical movement

54
Q

Why are CP deficits often the first abnormalities seen with disease of the spinal cord?

A

B/c most pathways consistent of large myelinated fibers with very fast transmission times that are most often situated on the periphery of the SC, making them susceptible to the first effects of compressive lesions

55
Q

If a compressive lesion affecting CP is located caudal to or below the rostral brainstem (b/t pons and medulla), what side would you expect the deficit to be on?

A

The same side as the lesion

56
Q

How do you test for pain perception?

A
  • use a strong instrument (ie hemostats or Carmalts) to squeeze the bone of the digit
  • a positive response is a conscious response (turning toward stimulus, trying to bite)

*with a severed SC, the leg can still pull back b/c of withdrawal reflex

57
Q

What is the difference between paresis and plegia?

A
  • Paresis is a motor deficit or weakness
    • an affected limb cannot support weight well and may not be able to move well
  • Plegia is if there is no voluntary movement at all
58
Q

Describe the complex controls of gait

A
  • Is controlled from midbrain and brainstem descending pathways
  • a cerebrocortical lesion may affect gait, but will not abolish it (plegia)
59
Q

What is ataxia and what are the 3 types of it?

A

Lack of coordination

  1. cerebellar - dysmetria w/ movements that are too long/too short (e.g. goosestepping)
  2. vestibular - often involves leaning/listing to one side, as well as crossing over of feet at walk
  3. proprioceptive - involves scuffing and hypometria
60
Q

What are some indications for a neuro exam?

A
  • Seizures
  • behavior change
  • circling, paresis
  • ataxia
  • pain
  • lameness
  • trauma
61
Q

What are the 6 components of a neuro exam?

A
  • Mentation
  • gait and posture
  • cranial nerves
  • postural reaction
  • segmental reflexes
  • palpation and range of motion
62
Q

What is the difference between the various mentation states?

A
  • Inappropriate: Disoriented, confused
  • Obtunded: dull, lethargic, less wakeful or responsive
  • Stuporous: responsive to noxious stimuli
  • Comatose: unresponsive to noxious stimuli
  • Vegetative: lacks awareness but brainstem ok
  • Brain dead: coma, apneic, no reflexes, flat EEG
63
Q

The personality component of mentation is controlled by what part of the brain?

A

The limbic system

64
Q

What sensory tract activates Purkinje cells and what side does it detect?

A

Spinocerebellar; ipsilateral

65
Q

Which sensory tract registers pain?

A

Spinothalamic; bilateral sensation

66
Q

Which sensory tracts detect pelvic limb sensation? Thoracic limb sensation?

A

PL: fasciculus gracilis

TL: fasciculus cuneatus

*Contralateral sensation

67
Q

What do you look at when you’re checking a patient’s posture?

A

Head: tilt, turn, resting or intention tremors, head held low, neck guarding

Body: kyphosis, lordosis, scoliosis, torticollis, laterally recumbent

68
Q

What is the difference between decerebrate, decerebellate, and Schiff-Sherrington?

A

Decerebrate: comatose, midbrain lesion, rigid extension in all limbs

Decerebellate: acute cerebellar lesions, extended TLs, flexed PLs (“star gazing)

SS: severe, acute T3-L3 lesions, not prognostic

69
Q

List the 12 cranial nerves

A

I: Olfactory

II: Optic

III: Oculomotor

IV: Trochlear

V: Trigeminal

VI: Abducent

VII: Facial

VIII: Vestibulocochlear

IX: Glossopharyngeal

X: Vagus

XI: Accessory

XII: Hypoglossal

70
Q

CN I is linked to what parts of the brain?

A

limbic system and rhinencephalon

71
Q

What nerves does the PLR test?

A

II & III

72
Q

What nerves does the menace reflex test?

A

II and VII

73
Q

What nerves does the dazzle reflex test?

A

II and VII, sub-cortical reflex

74
Q

What muscles does the oculomotor nerve (CN III) innervate?

A

dorsal, medial, ventral rectus, ventral oblique, and levator palpebrae of superior eyelid; PS motor fibers for pupillary constriction

75
Q

What does the trochlear nerve (CN IV) control?

A

motor pathway to the dorsal oblique m.

76
Q

What are the different branches of the trigeminal nerve (CN V), where do they come out of, and what do they innervate?

A

Sensory branches:

  • Ophthalmic n. (V1) - orbital fissue
  • Maxillary n. (V2) - round foramen

Motor branches:

  • Mandibular n. (V3) - oval foramen
    • Muscles of mastication
77
Q

What does the abducent nerve (CN VI) innervate? What would a lesion to this nerve cause?

A

motor to the lateral rectus and retractor bulbi mm; lateral strabismus with inability to retract the globe

78
Q

What does the facial nerve (CN VII) innervate?

A

Motor: muscles of facial expression

Sensory:

  • taste
  • palate
  • rostral 2/3 of tongue
  • inner surface of the pinna
79
Q

What are the branches of the vestibulocochlear nerve (CN VIII) and what do they innervate? What are some signs of vestibular disease?

A

Vestibular: sensory for orientation of the head with respect to gravity

  • physiological/pathological nystagmus (doll’s eye)
  • strabismus
  • head tilt
  • ataxia

Cochlear: sensory for hearing, difficult to test, BAER

80
Q

What do CN IX, X, and XI control?

A
  • Nucleus ambiguus (IX, X)
  • sternocleidomastoid and trapezius mm.
  • gag reflex
  • larynx
81
Q

How do you test CN XII?

A

tongue strength, movement, and position

  • look for asymmetrical tongue
82
Q

What cranial nerves are you testing for with the palpebral reflex?

A
  • Medial canthus: afferent - V1, efferent - VII
  • Lateral canthus: afferent - V2, efferent - VII

*lateral ALWAYS weaker

83
Q

What cranial nerves are you testing for when you’re checking for physiologic nystagmus?

A

Afferent: CN VIII

Efferent: CN III, IV, VI

  • also checking strabismus, positional nystagmus
84
Q

What nerves are you testing with the gag reflex test?

A

Afferent: CN IX, X

Efferent: IX

85
Q

What CN are you testing when checking tongue function?

A

CN XII

86
Q

What postural reactions do you test during the neuro exam?

A
  • placing/knuckling (CP)
  • hopping
  • hemistanding/hemiwalking
  • wheelbarrow
  • visual and tactile placing
  • extensor postural thrust
87
Q

What are you testing with the thoracic limb withdrawal segmental reflex?

A
  • biceps and musculocutaneous n.
    • C6-C8
  • Triceps and radial n.
    • C8 -T2
88
Q

What segmental reflex are you testing with the cutaneous trunci test?

A
  • lateral thoracic n. and C8-T1
89
Q

What segmental reflex are you testing with the patellar reflex test?

A
  • femoral n. and L4-L6
  • Gastroc/cranial tibial n.
90
Q

What segmental reflex are you testing with the pelvic limb withdrawal test?

A
  • Mostly sciatic n. and L6-S1
91
Q

What do you check for with the perineal reflex?

A

tail tuck and anal sphincter contraction

92
Q

T or F: you can sever the spinal cord cranial or caudal to the cell bodies involved in a segmental reflex (intumescence) and the reflex will still be intact

A

True; NOT voluntary motor function!

Clinical Neuro (7 decks)

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