Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

functional neuroanatomy > Week 6 - lower motor neurons > Flashcards

Week 6 - lower motor neurons Flashcards

1
Q

Which part o the reticular formation produces noradrenaline?

A

noradrenaline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What neurotransmitter is produced by the substantial nigra?

A

dopamine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What neurotransmitter is produced by Ralph nuclea ?

A

serotonin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what produces movement?

A

spatial and temporal patterns of muscular contractions, which are orchestrated by neural circuits in the brain and spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do neural circuits make

A

simple movements eg. knee-jerk reflex
complex motor movements eg. playing musical instrument

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

ascending

A

always sensory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

descending

A

always motor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what motor neurons originate in the motor cortex

A

voluntary movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what motor neuorns originate in the brain stem?

A

involuntary movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Lower motor neuron

A

spinal cord to muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

upper motor neuron

A

brain to spinal cord

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

interneurons

A

found only in CNS
connector between sensory/ motor system in real time
found in both spinal cord+ Brain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

example of a pathway

A

receptor -> dorsal root ganglion on sensory -> interneurone at lateral horn -> motor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

local interneuron

A

short axon, only connects with nearby neurones, a lot in reflex chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

relay interneurons

A

long axons, tracts connect separate regions of brain for large scale processing, most common in Brian

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

are interneurons multi or unipolar?

A

always multi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are interneurons important for?

A

learning, decision making (relay) and synchronised muscle movement (local)

can release excitatory glutamate or inhibitory GABA as neurotransmitters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

where do upper neurons cell bodies lie ?

A

brainstem or cerebral cortex with axons descending to synapse with local circuit neurons or more rarely lower motor neurones directly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are upper motor neurons that originate in the motor cortex responsible for?

A

initiation of voluntary movements

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are upper motor neurones that originate in brainstem responsible for?

A

basic navigational movements and regulating posture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the basal ganglia

A

upper motor neurons in cortex will relay through it, checkpoint, ensure its the right response, can inhibit constant excitation eg. seizure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

cerebellum

A

coordination of movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

coordinates Which types of neuron primarily inputs to LMNs ?

A

inhibitory interneurones -> need to stop incorrect movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are lower motor neurons?

A

motor neurons in cord and brainstem that directly innervate SKELETAL muscle contraction and bind to motor synaptic junction always ACETYLCHOLINE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Name the two types of lower motor neuron found in pools of the ventral horn

A

alpha and gamma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Alpha motor nurons

A
  • innervate extrafusal muscle fibres
  • largest, widest axons, prevent inhibition of organelles as get in the way, more myelin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are gamma motor neurones

A
  • smaller, less myelinated
  • innervate intramural muscle fibres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What do extrafusal muscles do?

A
  • generate force
  • on outside
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What do intramural muscles do?

A
  • on inside
  • measures stretch also assists in contraction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What are motor units

A

small functional motor unit in nervous system
made up of an individual alpha motor neuron and extrafusal fibres it innervates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

in femur

A

lot of muscle fibres innervated by single motor neuron, the bigger the motor units, the more muscle fibres innervated at once

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

motor unit subtypes

A
  • slow-contracting, fatigue-resistant MUs (s) - needed for sustained, low effort ie. posture eg. cardiac muscle
  • fast-contracting, fatigue resistant MUs (FR) - intermediate ie. walking
  • fast-cot rating but fatiguable units (FF) - brief exertion ie sprinting
33
Q

What do distinctions between motor units help explain?

A
  • how the Ns produces movements appropriate diff circumstances
  • strucutal differences between muscle groups
34
Q

What is the best example of a large motor unit

A

in the calf (gastronemius) around 100 muscle fibres in each one

35
Q

which of these is proprioceptive

A

LMN intramural

36
Q

how is muscle contraction force generated?

A
  • recruitment of motor units
  • impulse frequency
37
Q

recruitment of motor units

A

increasing or decreasing number of motor units active at any one time changes the amount of force produced by a muscle
-> size principle

38
Q

impulse frequency

A

frequency of impulse contributes to twitch strength - nr of units recruited
- at low frequency stimulation, each AP in motor neuron results in single twin of recruited muscle fibres
- at higher frequency, twitches sum to produce a force greater than that produced by single twitches

39
Q

tetanus

A

at higher frequency o stimulation, the force produced is greater, but individual twitches are still apparent - unfused tetanus
- highest rate of motor neuron activation, individual twitches are no longer apparent, the response is referred to as fused tetanus
-> can’t see individual muscle contractions as it is constant

40
Q

which motor units are recruited to gastrocnemius to allow a massive jump

A

S, FR, FF

41
Q

reflex arc

A
  • spinal pathway in which a motor response is generated in response to a sensory stimulus
  • local interneurons within the spinal cord initiate sensory motor reflex actions
42
Q

simples reflex arc

A

entails sensory response to muscle stretch, which provides direct excitatory input to the lower motor neuones innervating muscle that has been stretched
-> sensory signal for stretch reflex originates in muscle spindle

43
Q

muscle spindle

A
  • highly specialised organs found in most skeletal muscles that provide mechanosensory information about muscle length
44
Q

how are muscle spindles organised?

A

8-10 intramural fibres arranged in parallel with the extrafusal fibres that make up bulk of muscle

45
Q

what are the two structural classes of intramural fibres?

A
  • nuclear bad fibres and nuclear chain fibres that differ in sensitivity to stretch
46
Q

How many nuclear bag fibre and nuclear chain fibres are contained in most muscle spindles?

A

3 bag
twice as many nuclear chain fibres

47
Q

muscle spindle Ia

A

afferents are sensory icons that coil around central part of each class of intramural fibre

48
Q

group 2 afferents

A

form secondary endings mainly on nuclear chain fibres

49
Q

what does the stretch imposed on muscle fo

A

deforms intramural muscle fibres, which turn initiate action potential by activating mechanically gated ion channels in afferent axons innervating spindle

50
Q

what do muscle spindles do

A

detect muscle length
- fire action potential spontaneously at steady rate at resting muscle lengths
- when stretched action potential firing rate briefly increases
- muscle spindle can therefore be viewed as a muscle length detector

51
Q

How can we detect and measure action potentials in real time?

A

EMG electromycrogram

52
Q

stretch reflex circuitry

A
53
Q

what is the highest level of afferent stretch circuitry

A

spinal local interneurons - brain not involved in reflex

54
Q

gamma motor neurons

A
  • innervate intramural fibres
  • in stretch: work in tandem with alpha motor neurons
  • alpha simulated alone, response of Ia fibre decreases muscle contracts, when both alpha and g-motor in Ia firing during muscle shortening, thus g-motor neurones regulate gain of muscle spindles so they can operate efficiently at any muscle length
55
Q

Golgi tendon organ

A

encapsulated afferent nerve endings located at junction of muscle and a tendon at the junction o muscle and tendon that provide mechanosensory information about sucre tension

56
Q

gogli tendon negative feedback - not in exam

A
57
Q

what afferents are sensory axons that could around central part of each class of intramural fibre ?

A

group Ia

58
Q

organisation of descending motor control

A

UMN pathways differ in where they terminate in SC
innervate different muscles
white matter tracts want to be as short as possible for efficient

59
Q

brodmann’s areas

A
  • developed in 1909
  • defined via cytoarchitecture
  • distinct under microscope
60
Q

Area 9 and 46

A

prefrontal cortex - planning future movements

61
Q

Area 6 and 8

A

muscle contractions - premotor area

62
Q

area 4

A

primary motor cortex - execution fo simple motor programs

63
Q

area 1 and 3

A

somatosensory cortex

64
Q

dorsolateral prefrontal cortex

A
  • located in area 9 and 46
  • executive functions
  • highest cortical area involved with motor planning
65
Q

pre-motor cortex

A
  • sensory input form inferior (visual) and superior (touch) parietal lobes
  • prefrontal areas in frontal lobe have input regarding motivation
66
Q

primary motor cortex

A
  • located in pre central gyrus in area 4
  • strong axonal connections to LMNs (thick axons)
67
Q

Types of PMC cells

A
  • pyramidal cells of cortical layer 5 are upper motor neuons of primary motor cortex
  • Among these neurons, Betz cells, which are the largest neurons in the human CNS but only account for -5% of projections to spinal cord
68
Q

posture is controlled via which region fo white matter?

A

medial

69
Q

corticobulbar spinal tract

A
  • axons leave tract at appropriate level of brainstem:
    1. cranial nerve nuclei eg. hypoglossal nucleus for motor supply of tongue nucleus
    2. reticular formation - important wakefulness
  • corticobulbar axons can also terminate among nuclei at base of pons
70
Q

Tracts

A
  • axons of LMNs descend into corticobulbar and corticospinal tracts (axons that terminate in brainstem or spinal cord respectively)
  • internal capsule > cerebral peduncle> pons > pontine fibres
71
Q

lateral corticospinal tract

A

large majority of axons -90% cross caudal part of medulla to form lateral corticospinal tracts ins spinal cord

72
Q

ventral corticospinal tract

A

remaining corticospinal axons -10% that do not cross in caudal part of medulla terminate bilateraly to ventral corticospinal tract

73
Q

what are lateral axons involved in

A

innervating muscles of forearm and hand

74
Q

where do ventral axons arise form primarily?

A

from dorsal and medial motor cortex and serve axial and proximal limb muscles

75
Q

where are spinal lock interneurones found?

A

intermediate horn

76
Q

What happens when motor systems are damaged?

A
  • lower - 99% axon - can repair, cell bodes can’t
  • > spinal cord/brain much worse
77
Q

symptoms of lower

A
  • weakness or paralysis
    decreased superficial reflexes
    hypoactive deep reflexes
    decreased tone
    fasciculations and fibrillations
    severe muscle atrophy
78
Q

symptoms of upper

A

weakness
spasticity
increased tone
hyperactive deep refills
clonus
babinskis sign
loss of fine voluntary movements

79
Q

what is decussation?

A

axons crossing the contralateral side across the midline

functional neuroanatomy (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions