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Neurobiology > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

muscle contractions and relaxations that are rapid, stereotyped, involuntary, and coordinated (knee jerk, swallowing, pain withdrawal)

A

reflex responses

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2
Q

initiation and termination are

voluntary and triggered by peripheral stimuli (running, walking, chewing)

A

rhythmic motor patterns

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3
Q

initiated movements to accomplish a specific goal; largely learned movements that improve with practice (as one learns to anticipate and correct for environmental obstacles)

A

voluntary movements

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4
Q

What is the upper motor system responsible for?

A

planning and selecting movements

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5
Q

What is the lower motor system responsible for?

A
  • executing movements

* simple sensory-motor reflexes

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6
Q

measures electrical activity in muscles

A

EMG - electromyograph

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7
Q

type of motor neurons that originate in ventral horn of spinal cord; form the “final common pathway”

A

Aα type

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8
Q

Each Aα type motor neuron innervates fibers within a ___. Each muscle fiber innervated by a ___.

A

single muscle

single motor neuron

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9
Q

All motor neurons innervating a single muscle are grouped in clusters called ____.

A

motor pools

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10
Q

Motor pools are located with a slight spread along the ____.

A

anterior-posterior axis

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11
Q

Describe the proximal to distal spatial map for the ventral horn.

A

Distal muscles are located at the outer edges, axial muscles are located toward the center

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12
Q

Describe the flexor to extensor spatial map for the ventral horn.

A

Flexors are located more dorsal (towards back), extensors are located more ventral (towards front)

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13
Q

What are some characteristics of lower motor neuron diseases?

A

decreased tone, weakness, retardation of movement, hyporeflexia, and muscle wasting

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14
Q

How is polio spread?

A
  • spread by fecal-oral route
  • attaches to receptors in cells of small intestine
  • diarrhea and/or upset stomach
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15
Q

Polio that stops at the GI tract

A

abortive poliomyelitis

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16
Q

15% of polio cases result in this

A

aseptic meningitis

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17
Q

____ occurs in __% of cases. It targets motor neurons to cause muscle weakness (~__% of nerves affected. Nerve death results in ___. Progression stops only when ___ (paralysis is permanent).

A 
paralytic poliomyelitis
1-5
50
paralysis
immune system overcomes the virus
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18
Q

ALS (___) is the result of both genetic and spontaneous mechanisms. It can results from mutations in ___, which is __. It causes hardening of ___.

A

Amyotrophic lateral sclerosis
SOD1
autosomal dominant
lateral corticospinal columns

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19
Q

What are the symptoms of ALS?

A
  • muscle wasting
  • hyper-reflexia (combination of both upper and motor neuron signs of disease)
  • increasing muscle weakness (especially in arms and legs)
  • clumsiness
  • muscle cramps and spasms
  • difficulty speaking, swallowing, and breathing
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20
Q

lower motor neuron and all the muscle fibers it innervates

A

motor unit

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21
Q

____ are small fibers and with small motor units. “Red” fibers contract slowly but are relatively ____. They are rich in ___ (oxidative phosphorylation) and allow for ____ (e.g., posture).

A

slow (S), aka Type I
resistant to fatigue
mitochondria
sustained muscle contraction

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22
Q

___ are large fibers and involve larger, more powerful motor units. They are the larger pale muscle fibers. The contain sparse mitochondria (use ___ instead) and are ____.

A

fast fatigable (FF), aka Type IIa
mitochondria
glycolysis
easily fatigued

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23
Q

__ fibers are intermediate in size and ___ than FF but ___.

A

fast fatigue-resistant (FR), aka Type IIb
slower
less fatigable

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24
Q

What is Henneman’s Size Principal?

A

That fibers are recruited in order of size. Aka., low stimulation – only Type I fibers, then IIb, then IIa. There is a range of forces to perform different motor tasks. The largest motor units recruited only when maximum force is needed

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25
Q

Describe (temporal) summation in muscle fibers.

A

muscle fiber activated by new AP before relaxed from the previous AP –> produce more force; forces generated by temporally overlapping contractions are summed

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26
Q

tereotyped movements elicited by activation of skin or muscle receptors

A

spinal reflexes

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27
Q

innervate extrafusal muscle fibers; generate forces needed for movement

A

α motor neurons

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28
Q

innervate intrafusal muscle fibers; embedded within connective tissue of muscle; innervated by both sensory and motor neurons; report info about length and tension of muscle

A

γ motor neurons

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29
Q

sensory organ for determining muscle length and stretch; embedded in muscle

A

muscle spindle

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30
Q

During the stretch (___) reflex, discharge of ___ occurs related to ___ of muscle. When muscle stretched, it ___ firing rate.
When muscle is shortened (goes slack), it ____ firing rate. Ia axon synapses on ___ and is ____.

A 
myotatic
Ia sensory axons
length
increases
decreases
alpha motor neuron
monosynaptic
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31
Q

large diameter sensory fibers coiled around muscle spindles; thickest myelinated axons in body; fastest

A

Ia sensory axons

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32
Q

Stretch imposed on a muscle stretches ___ –> activates mechanically gated ion channels in ___ and initiates an AP. These sensory neurons synapse with ___ in the same muscle and with synergistic muscles in ___.
The sensory neurons activate local ___ connections for ___ muscles.

A 
intrafusal muscle fibers
Ia axons
motor neurons
spinal cord ventral horn
inhibitory
antagonistic
33
Q

a polysynatpic reflection that compensates posture during withdrawal from pain

A

flexor (withdrawal) reflex

34
Q

During the flexor reflex, pain axon enters spinal cord
and activates ____, which eventually excite ___ that control ___ muscles of affected limb. Other ___ inhibit ___ that control ___.

A 
interneurons
alpha motor neurons
flexor 
inhibitory interneurons
alpha motor neurons
extensors
35
Q

A reflex that activates extensor muscles and inhibit flexor muscles on the opposite side in response to a flexor reflex

A

crossed extensor reflex

36
Q

inhibition that compensates for the excess load imposed by limb withdrawal

A

reciprocal inhibition

37
Q

limb is extended and in

contact with the ground (can get quicker)

A

stance phase

38
Q

limb is flexed to leave the ground and then brought forward to bring the next stance phase (stays relatively constant)

A

swing phase

39
Q

Where are central pattern generators (CPG) located?

A

spine

40
Q

individual neurons whose membrane properties allow them to generate rhythmic activity

A

pacemaker neurons

41
Q

Pacemaker neurons neuron possesses both __

channels and ___ channels. They will fire rhythmically when stimulated with ____.

A

Ca2+-activated K+
NMDA
glutamate

42
Q

Pacemaker neurons have regular __ channels to generate APs. NMDA channel blocked by ___ at hyperpolarizing membrane potential. Internal __ dissipates and __ channel shuts off. ___ block is removed upon depolarization.

A 
voltage-gated Na+ and K+
Mg2+ 
Ca2+
Ca2+ -activated K+
Mg+2
43
Q

axons from ___ descend to influence local circuits in brainstem and spinal cord

A

upper motor neurons

44
Q

What areas do upper motor pathways include?

A

-brainstem centers
-cortical areas in frontal
lobe

45
Q

The brainstem is especially important for ___.

A

postural control

46
Q

The motor and premotor cortex are responsible for ___.

A

planning and precise control of voluntary movement

47
Q

The ___ is responsible for balance and posture; receives input from brainstem ___.

A

medial ventral horn

bilaterally

48
Q

The ____ is responsible for voluntary movement of distal extremities; its controlled by ___ motor cortex (distal muscles operate
independently).

A

lateral ventral horn

contralateral

49
Q

The primary motor cortex is located in the ___. It receives input from __, ___ (incorporates multiple sensory modalities, used for planning). It controls the ___ side of the body and uses ____.

A 
precentral gyrus
S1
posterior parietal
contralateral
topographic organization
50
Q

over-representation of brain regions that are required for most complicated motor behaviors (i.e., more space given to fine motor control)

A

homunculus

51
Q

The primary motor cortex has _ layers; layer V is the ___. It is mapped the same way that sensory cortex is mapped. The ___ is essential in planning movements but does not provide direct input to __; coordinates movements in space.

A

6
output layer (pyramidal cells)
posterior parietal
spinal cord

52
Q

The direct pathway from the cortex to the spinal cord is the ___. Axons cross in the __ and innervate the ___ ventral horn.

A

corticospinal tract
medulla
opposite

53
Q

The indirect pathway from the cortex to the spinal cord is the ___. It allows for ___, especially for axial and proximal muscles.

A

corticoreticulospinal tract

postural adjustments

54
Q

adjacent to primary motor cortex, extensive reciprocal connections; projects directly to spinal cord

A

premotor cortex

55
Q

In the premotor cortex, neurons fire ___; responsible for conditional motor tasks that pair movement with a ____.

A

earlier

visual cue

56
Q

neurons fire before initiation of task; cells fire when just thinking about an event

A

intention

57
Q

What are the symptoms of upper motor neuron lesions?

A 
weakness
spasticity
increased tone
hyperactive deep reflexes
clonus
Babinski's sign
loss of fine voluntary movements
58
Q

What are the symptoms of lower motor neuron lesions?

A 
weakness
paralysis
decreased superficial reflexes
hypoactive deep reflexes
decreased tone
fasciculations and fibrillations
severe muscle atrophy
59
Q

influence movements through upper motor neurons

A

basal ganglia

60
Q

What are the 3 main nuclei of the basal ganglia?

A

caudate, putamen, globus pallidus

61
Q

The basal ganglia form a loop with the ___ and the ___ to link the cortex with ___. They are required for ___.

A

substantia nigra
subthalamic nucleus
upper motor neurons
voluntary movements

62
Q

Inputs to caudate and putamen from the cortex are ____. They also receive ___ inputs from substantia nigra. Interneurons and thalamic neurons form ___.

A

excitatory (glutamatergic)
dopaminergic
inhibitory synapses

63
Q

Neurons in the basal ganglia fire in anticipation of a ___ (putamen = ___, caudate = ___).

A

movement
body movements
eye movements

64
Q

Caudate and putamen send inbihitory GABAergic projections to…?

A

– globus pallidus (internal and external segments)

– substantia nigra (pars reticulata)

65
Q

GPi (globes pallidus) neurons project back to cortex via ____.

A

thalamus

66
Q

When striatal neurons fire (in anticipation of movement), they ____.
This allows upper motor neurons to send commands to lower motor neurons to ___.

A

inhibit the inhibition (i.e., disinhibition)

initiate movement

67
Q

Spontaneous activity of the GABAergic GPi and pars reticulata neurons prevents ____.

A

unwanted movements

68
Q

In the indirect pathway, the striatum projects to ___, then to ____. STN projects to ___, then to ____. STN projections are ____, which increases inhibition of GPi. (does the OPPOSITE of direct pathway!)

A 
globus pallidus external nuclei
subthalamic nuclei of central thalamus
Gpi
thalamus
excitatory
69
Q

Striatal neurons from the substantial nigra that project to GPi have __ receptors (___). Striatal neurons that project to GPe have __ receptors (____)

A

D1
excitatory
D2
inhibitory

70
Q

Dopamine ___ the direct pathway and ___ the indirect pathway.

A

excites

inhibits

71
Q

Huntington’s Diseases is entirely ____ and ____.

A

genetic

autosomal dominant

72
Q

In Huntington’s disease, the coding region has an abnormal amount of ____. This gets larger with each ___. This leads to the selective loss of ___, and in turn, the loss of inhibition of ___. This results in increased stimulation of ____ by basal ganglia.

A 
CAG repeats
generation
stratal GABAergric neurons
GPe
motor cortex
73
Q

What are the symptoms of Huntington’s?

A

rapid, jerky movements with no clear purpose (chorea)

psychiatric symptoms as well

74
Q

A neurodegenerative movement disorder that usually develops after age 50

A

Parkinson’s Disease

75
Q

What are the symptoms of Parkinson’s?

A 
difficulty walking, movement and coordination
tremor
rigidity
akinesia
postural instability
76
Q

In Parkinson’s, ____ are destroyed over time. ___ accumulates in deposits called ___ within dopamine neurons.

A

dopaminergic neurons
alpha-synuclein
Lewy bodies

77
Q

Parkinson’s is usually ___ but it has once been tied to ____ due to influenza. In 1976, contaminated batches of synthetic heroin (MPTP instead of MPPP) led to ____.

A

genetic
molecular mimicry
drug-induced Parkinson’s

78
Q

In Parkinson’s, you lose dopaminergic neurons in ____, which decreases the ___ pathway and increases the ___ pathway. This leads to decreased stimulation of motor cortex by ____.

A

SN pars compacta
direct
indirect
basal ganglia

79
Q

What are the most popular treatments for Parkinson’s?

A

L-dopa (can cross BBB)

sub thalamic deep brain stimulation

Neurobiology (9 decks)

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