Brainscape's Knowledge GenomeTM

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


See full index

Neurology > Physiology > Flashcards

Physiology Flashcards

1
Q

what do dendrites do

A

receive inputs from other neurones and convey graded eletrical signals passively to the soma

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

what does the soma contain

A

nucleus, ribosomes, mitochondria, endoplasmic reticulum

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

what is the axon hillock and initial segment

A

site of initiation of the all or non action potential

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

what is the role of the axon

A

conducts ouput signals as action potentials to the presynaptic terminal

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

what is the synapse

A

point of chemical communication between neurones

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

what type of neurones are: peripheral autonomic neurones

A

unipolar

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

what type of neurones are: dorsal root ganglions

A

pseudounipolar (one neurite that bifurcates)

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

what type of neurones are: retinal neurones

A

bipolar (2 neurites)

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

what type of neurones are: lower motor neurones

A

mulitpolar (3 or more neurites)

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

what is a neurite

A

process that arises from a soma

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

why do passive signals not spread far from their site of origin

A

as the diminish as they spread (leaky membranes) - action potentials is different, have constant amplitude and dont diminish

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

what is membrane potential change

A

as the current passes through axons it leaks into extracellular space creating a potential change

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

how does passive conduction affect action potential velocity

A

passive conduction is a factor in AP propagation

the further the local current spread the fast the AP conduction velocity

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

how is passive current spread (and therefore AP velocity) sped up

A

increase membrane resistance (myelination)

decrease axial resistance of axoplasm (increase axon diameter)

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

what cells myelinate

A

schwann cells in PNS
oligodendrocytes in the CNS
(both macroglia)

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

is conduction in myelinated axons faster or slower than unmyelinated axons of the same diameter

A

faster

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

what is saltatory conduction

A

the action potential jumps from one node of ranvier to the next

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

name two demyelinating disorders

A 
mulitple sclerosis (CNS)
guillian barre (PNS)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what are the steps of chemical neurotransmission

A
  1. uptake of precursor
  2. synthesis of transmitter
  3. storage of transmitter
  4. depolarisation by action potential
  5. Calcium influx
  6. calcium induces release of transmitter (exocytosis)
  7. receptor activation
  8. enzyme mediated inactivation of transmitter or re uptake of transmitter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is the synaptic cleft

A

gap between pre and post synaptic membranes

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

what is in the synaptic cleft

A

fibrous extracellular protein

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

what holds the neurotransmitter in the synapse

A

vesicles in the pre synaptic terminal

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

what are the synaptic membrane differentiations

A

presynaptically- active zones around which vesicles cluster

postsynaptically- the postsynaptic density which contains neurotransmitter receptors

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

what are the morpholgical types of synapses

A

axodendritic
axosomatic
axoaxonic

(the location of the presynaptic terminal upon the post synaptic cell)

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

what is the most common CNS neurotransmitter for excitatory synapses

A

glutamate

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

what is the most common CNS neurotransmitter for inhibitory synapses

A

GABA or glycine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is the inhibitory/ excitatory post synaptic potential

A

a local graded excitatory (depolarising) or inhibitory (hyperpolarising) response to transmitter (glutamate or GABA or glycine)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what type of neurotransmitters are glutamate, GABA and glycine

A

amino acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is synaptic integration

A

when either:
-many inputs converge upon a neurone to determine its output (spacial summation)
or
-when a single input modulates output by variation in action potential frequency of that input (temporal summation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what type of neurotransmitter are dopamine, histamine, noradrenaline and serotonin

A

amines

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q 
what type of neurotransmitter are cholecystokinin
dynorphin
enkephalins 
neuropeptides
somatostatin
substance P
TRH
vasoactive intestinal polypeptide
A

peptides

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

what releases acetylecholine, amino acids and amines

A

synaptic vesicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what releases peptides

A

secretory vesicles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what do Glutamate, GABA, glycine, acetylcholine, and 5-HT activate and mediate

A

ionotropic ligand gated ion channels

mediate fast neurotransmission

All, except glycine, can also activate metabotropic G-protein-coupled receptors. These mediate relatively slow neurotransmission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what is direct gating

A

when neurotransmitters act directly on the ion channel

done by ionotropic receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what is indirect gating

A

when neurotransmitters acts indirectly on the ion channel

mediated by activation of metabotropic receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what causes fast excitatory postsynaptic potentials

A

activation of nicotinic (ionotropic) ACh receptors. Channels conduct Na+ and K+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what causes slow excitatory postsynaptic potentials

A

activation of muscarinic (G protein- coupled) ACh receptors. ACh closes a K+ channel (M-type)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

via what does glutamate have inhibitory effects

A

metabotrophic glutamate receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

how can Ionotropic Glutamate receptors be classified

A

classified via their response to non-endogenous agonists that mimic glutamate
non-NMDA receptors bind the agonists kainate or AMPA controlling a channel permeable to Na+ and K+
NMDA receptor controls a channel permeable to Na+, Ca2+ and K+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what do non NMDA ionotropic receptors (AMPA and kainate)

do

A

mediate fast excitatory synaptic transmission in the CNS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what do NMDA ionotropic receptors do

A

contributes a slow component to the excitatory synaptic potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what is the clinical relevance of NMDA receptors

A

Certain anaesthetic agents e.g ketamine and psychomimetric agents e.g. phencyclidine are selective blockers of NMDA-operated channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

how do metabotropoc glutamate work

A

don’t have an integral ion channel but exert their effect by activation of a second messenger cascade

Role is modulation of neurotransmission.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what is mechanosensation

A

fine discriminatory touch (light touch, pressure, vibration, flutter and stretch)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

what is nociception

A

pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

what is the exteroceptive division of somatosensation

A

(cutaneous senses) registers information from the surface of the body by numerous receptor types

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

what is the proprioceptive division of somatosensation

A

monitors posture and movement (sensors in muscle, tendons and joints)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

what is the enteroceptive division of somatosensation

A

reports upon the internal state of the body and is closely related to autonomic function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

how many neurones in series usually make up a somatosensory pathway- what and where are they

A

3
1st= primary sensory afferent (in either dorsal root ganglia or cranial ganglia)
2nd= projection neurone (dorsal horn of spinal cord or brainstem nuclei)
3rd= projection neurone in thalamic nuclei
somatosensory cortex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

where in brain does proprioceptive input go to

A

cerebellum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

what potential does a sensory stimulus create

A

stimulus (mechanical, thermal, or chemical) opens cation selective ion channels in peripheral terminal of primary sensory afferent eliciting a depolarising receptor potential

the amplitude of the receptor potential is graded and proportional to the stimulus intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

what does a supra threshold receptor potential trigger

A

all or non action potentials conducted by the axon, at a frequency proportional to its amplitude

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

what is an all or none response

A

the strength of a response of a nerve cell or muscle fiber is not dependent upon the strength of the stimulus. If a stimulus is above a certain threshold, a nerve or muscle fiber will fire. Essentially, there will either be a full response or there will be no response at all for an individual neuron or muscle fiber

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

what do action potentials arriving at the central terminal of the 1st order neurone cause

A

a graded release of neurotransmitter on to second order neurones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

what is the modality of a sensory unit

A

what type of stimulus excited it (the adequate stimulus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

what is the threshold of a sensory unit

A

what intensity of stimulus is required for excitation of the sensory receptor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

what is the adaption rate of a sensory unit

A

does the sensory unit discharge action potentials continuously during the stimulus or does it respond preferentially to a changing stimulus
(whether they change their firing rate only in response to a stimulus of changing intensity, or fire continuously throughout a constant stimulus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

what is the conduction velocity of a sensory unit

A

how rapidly it conducts APs along its axon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

what is the receptive field of a sensory unit

A

site and extent of its peripheral termination - can have a small/ large anatomical distribution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

what is the sensory unit for pain

A

mechanical, thermal and polymodal nociceptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

what mediates discriminatory touch

A

low threshold mechanoreceptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

what are high threshold units

A 
nociceptors:
mechano 
thermal 
chemical 
polymodal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

what are polymodal nociceptors

A

respond to at least 2 types of stimuli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

what do slow adapting units respond to

A

provide continuous information to CNS the whole time there is a stimulus - provides information about position, degree of stretch or force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

what do fast adapting units do

A

only produce APs proportional to the rate of change of the stimulus
do not constantly produce APs when stimulus is constant
detects changes in stimulus strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

what do very fast adapting units do

A

responds only to very fast movement (will not respond to slow changes in stimulus or a constant stimulus)
e.g. pacinian corpuscle (e.g. rapid vibration)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

what do Aalpha axons do

A

proprioceptors of skeletal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
69
Q

what do Abeta axons do

A

mechanoreceptors of skin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
70
Q

what do Adelta axons do

A

temperatures, pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
71
Q

what do C axons do

A

temperature, pain and itch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
72
Q

how and why does the conduction velocity change between Aalpha, Abeta, Adelta and C axons

A

from Aalpha, Abeta, Adelta to C get less myelinated and therefore slower conduction velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
73
Q

what is the receptive field

A

the target territory from which a sensory unit can be excited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
74
Q

how is receptive field relative to innervation density

A

inversely proportionate

low density of innervation= large RF= high sensory acuity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
75
Q

what do afferent nerve fibres end in

A

either free nerve endings (partially naked)

or associated with specialised structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
76
Q

what is spatial acuity

A

two point discrimination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
77
Q

where do you not get meissners copuscles

A

hairy skin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
78
Q

where are ruffini endings and what do they do

A

within dermis

pressure sensation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
79
Q

where are pacinian corpuscles and what do they do

A

semis and fascia

pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
80
Q

what do merkle discs, krause end bulbs, root hair plexuses and meissner corpuscles do

A

sense touch

81
Q

what do free nerve endings sense

A

pain, temperatuere

82
Q

how are low threshold mechanoreceptors classified

A

by their rates of adaption and size of receptive field

83
Q

what are the low threshold mechanoreceptoes

A

free nerve endings, follicular nerve endings, merkel cell neurite complexes, encapsulated nerve endings (meissner corpuscles, ruffini endings, pacinian corpuscles)

84
Q

does a pacinian or meissners corpuscle have a bigger receptive field

A

pacinian

85
Q

which has a higher human detection threshold meissner or pacinain corpuscle

A

meissners

86
Q

at what frequency are are pacinian corpuscles most sensitive

A

150- clinical test using a 128Hz tuning fork

87
Q

what part of nerve is affected in shingles

A

dorsal root ganglion

88
Q

what virus is shingles

A

varicella zoster

89
Q

what class of fibres are nociceptors

A

Adelta and C

90
Q

what class of fibres are low threshold mechanoreceptors

A

Abeta

91
Q

what class of fibres are proprioceptors

A

Aalpha

92
Q

what is the grey matter of the spinal cord divided into

A

10 distinct laminae of rexed

93
Q

how does the dorsal medial lemniscal pathway ascend

A

1st. order neurone enters dorsal horn and branches forming: (i) synapses deep in the dorsal horn upon 2nd. order neurones (important in spinal reflexes) and (ii) a long ascending axon (via the dorsal column gracile, or cuneate tracts) synapsing in either the dorsal column gracile nucleus (GN) or cuneate nucleus (CN)

Axons of 2nd. cross collectively in the great sensory decussation and ascend in the medial lemniscus to the ventral posterior lateral (VPL) nucleus of the thalamus

3rd order primary somatosensory cortex via posterior internal capsule

94
Q

what does the dorsal column medial leminscal pathway carry

A

info on discriminatory touch, pressure, vibration, conscious proprioception

95
Q

how does the spinothalamic tract ascend

A

decussate as it enters spinal cord, goes to thalamus, cortex

96
Q

what does the spinothalamic tract do

A

carry info on pain, thermosensation, crude touch, itch, tickle

97
Q

what are the parts of the dorsal column of the spinal cord

A

medial gracile tract (info from T6 and below) and the lateral cuneate tract (above T6)

from lateral to medial carry info from cervical, thoracic, lumbar, sacral

98
Q

what do the dorsal and ventral spinocerebella tracts do

A

convey unconscious proprioceptive information to the cerebellum

99
Q

what is the major route by why touch and CONSCIOUS proprioception ascends to the cerebral cortex

A

dorsal column medial lemniscial pathway

100
Q

what are the capabilities of the dorsal column medial lemniscal pathway

A 
stereognosis (recognise object by touch)
vibration detection 
fine touch
two point discrimination 
conscious proprioception
weight discrimination
101
Q

what is contrast enhancement

A

when information is conveyed from one neurone to the next in a sensory pathway, differences in the activity of adjacent neurones are amplified
when one neurone is active it inhibits the activity of its neighbours via inhibitory interneurones= lateral inhibition

102
Q

what is the point of lateral inhibition

A

sharpens stimulus perception

103
Q

where are the soma of sensory neurones of the trigeminal nerves found

A

trigeminal sensory ganglion

104
Q

what is the path of the trigeminal nerve to the brain

A

Central terminals of the trigeminal nerve synapse upon second order neurones in the chief sensory nucleus (general tactile stimuli), or spinal nucleus (pain, temperature information) which in turn decussate and project (via the trigeminal lemniscus) to the ventroposteriomedial (VPM) nucleus of the thalamus

Third order neurones relay information to the cortex via thalamocortical neurones

105
Q

what makes up the central sulcus

A

brodmann areas 1 (texture discrimination), 2 (pressure and joint position) ,3a (propriocpetors) and 3b body position)

106
Q

what parts of body on what parts of the somatosensory cortex

A

The toes are at the top of the post central gyrus with the tongue, pharynx and intra abdominal organs at the lower end, the hand separates the head from the face

107
Q

how is the somatosensory cortex organised

A

is layered and columnar

108
Q

are somatotopic maps constant

A

no are plastic
if area of sensation lost (amputated) area of somatosensory cortex will be utilized by other sensory inputs
if sensory input from an area increases the cortical representation of that area increases, relative that of inputs generating less activity

109
Q

what does the posterior parietal cortex do

A

Receives and integrates information from central sulcus and other cortical areas (visual, auditory) and sub-cortical areas (thalamus)

Deciphers the deeper meaning of the information

110
Q

what can damage to the posterior parietal cortex cause

A

neurological disorders (e.g. agnosia (inability to process sensory information), astereognosia (cant identify objects by touch), hemispatial neglect syndrome) with simple sensory skills remaining intacta

111
Q

where are upper and lower motor neurones

A

upper in brain

lowerin brainstem and ventral horn of the spinal cord

112
Q

what is the relationship between upper and lower motor neurones

A

UMN supply input to LWN to modulate their activity

113
Q

what do LWN recieve input from

A

upper motor neurones
proprioceptors
interneurons

114
Q

what commands muscle contraction

A

lower motor neurones

115
Q

what makes up lower motor neurones

A

alpha motor neurones- innervate the bulk of fibres within a muscle that generates a force

116
Q

what do gamma motor neurones do

A

innervate a sensory organ within the muscles known as a muscle spindle

117
Q

give examples of synergistic muscles

A

biceps brachii and brachialis
triceps brachii and anconeus

(ALSO as these muscles pairs oppose the other pairs actions they are agonists)

118
Q

what do axial muscles do

A

control the movement of the trunk (posture)

119
Q

where are proximal or girdle muscles

A

shoulder, elbow, pelvis and knee

120
Q

how do axons of lower motor neurones leave the spinal cord

A

in central roots (or via cranial nerves)

121
Q

what is a motor unit

A

an alpha motor neurone and all the muscle fibres it innervates- the smallest functional component of the motor system

122
Q

what is a motor neurone pool

A

a collection of alpha motor neurones that innervate a single muscle

123
Q

how do alpha motor neurones grade force of muscle contraction

A

frequency of action potential discharge of the alpha-MN (each causes a twitch)
the recruitment of additional synergistic motor units

124
Q

where in spinal cord are the cell bodies of the lower motor neurones

A 
ventral horn
(ones going to axial muscles are medial to those going to distal muscles. flexors dorsal to extensors)
125
Q

what are the three sources of input to an alpha motor neurone (LMN) that can regulate its activity

A

central terminals of dorsal root ganglion cells (whose axons innervate muscle fibres)
UMN in motor cortex and brainstem
spinal interneurones

126
Q

what does muscle stength depend on

A

activation of muscle fibres

  • firing rate of LMNs
  • number of LMNs that are stimultaneously active
  • coordination of the movement (antagonist, intergration/ control of reflexes)

force production by innervated muscles fibres

  • fibre size (hypertrophy)
  • fibre phenotype (fast or slow contracting muscle)
127
Q

what needs to summate for a muscle to contract

A

action potentials- a single AP will cause a muscle fibre to twitch

128
Q

how does the size of alpha MN (soma diameter) change with motor unit size

A

small motor units are innervated by small alpha MN and vise versa

129
Q

how does the size of alpha MN (soma diameter) change with the muscle fibre type

A

α-MNs innervating fast type tend to be larger and have faster conducting axons than those of slow units

130
Q

what are the two major types of muscle fibres and how do they differ

A

slow twitch and fast twitch
differ in how quickly myosin ATPse splits ATP to provide energy for cross bridge formation- reflected in time to develop peak tension

also express different myosin heavy chains

131
Q

what are type I muscle fibres

A

slow oxidative

132
Q

where do slow oxidative muscle fibres get their ATP from

A

oxidative phosphorylation

133
Q

what do slow oxidative fibres do (type I)

A

slow contraction and relaxation
fatigue resistant
antigravity, sustained movement

134
Q

why are slow oxidative fibres red

A

high myoglobin content

135
Q

what are type II muscle fibres

A

fast types:

  • type IIa
  • type IIx (or IIb)
136
Q

where do type II fibres get their ATP from

A

type IIa- oxidative phosphorylation

type IIx- glycolysis

137
Q

what do type IIa muscle fibres do

A

fast contraction and relaxation
fatigue resistant
(red and reasonably well vascularised)
sustained locomotion

138
Q

what do type IIx muscle fibres do

A

fast contraction
not fatigue resistant
(pale in colour and poorly vascularised)
burst power

139
Q

how does the threshold and size of alpha MN change with the different muscle fibres

A

fast fatiguing (IIx) have large alpha MN and high threshold

type IIa have intermediate alpha MN and threshold

type I have small alpha MN and low threshold

140
Q

how does the tension change between types of muscle fibres

A

IIX- very high
IIa- high
I-low

141
Q

what is the henneman size principle

A

The susceptibility of an α-MN to discharge action potentials is a function of its size. Smaller α-MNs (part of slow motor units) have a lower threshold than larger ones (part of fatigue resistant, or fast fatiguing, motor units). Slow motor units are more easily activated and “trained” by any training that activates the muscle.

Motor units (LMNs and the muscle fibres that they innervate) are recruited in the order of their size (i.e. progressively increasing – small LMNs are more easily excited than large LMNs)

142
Q

what does the activation of motor units in order of size and from type I first to IIa to IIx allow

A

a fine control of muscle force

143
Q

what is the myotatic reflex

A

when a skeletal muscles is pulled it contracts

144
Q

what does a muscle spindle to

A

senses change in length and rate of this change

contributes to non conscious proprioception

145
Q

what makes up a muscle spindle

A

fibrous capsule
intrafusal muscle fibres
sensory afferents (Ia, myelinated, fast conducting, that innervates intrafusal muscle fibres
(btw extrafusal fibres generate force)
gamma motor neurone efferents that innervate intrafusal fibres

146
Q

what are the steps of the myotatic reflex

A 
(is a monosynaptic arc)
stretch of muscle spindle 
activate Ia afferent 
excitatory synaptic transmission in spinal cord (mediated by release of glutamate)
activation of alpha MN
contraction of homonymous muscle
147
Q

what spinal level does the biceps jerk test

A

C5-C6

148
Q

what spinal level does the supinator (wrist) jerk test

A

C5-C6

149
Q

what spinal level does the triceps jerk test

A

C7

150
Q

what spinal level does the quadriceps (knee) jerk test

A

L3-4

151
Q

what spinal level does the gastocnrmius (ankle) jerk test

A

S1

152
Q

what can reinforce the knee jerk

A

jendrassik maneeuvre (pulling apart interlocked fingers)

153
Q

what are intrafusal fibres made up of

A

a non contractile equatorial region innervated by Ia sensory neurones

contractile polar ends that receive efferent input from gamma MN with cell bodies in the ventral horn of spinal cord (these are driven by higher centres NOT the Ia fibres)

154
Q

what happens to alpha and gamma MN during voluntary movement

A

are co activated so that intrafusal muscle fibres contract in parallel with the extrafusal fibres

155
Q

what are the types of intrafusal muscle fibres

A

nuclear bag fibres: -bag 1/ dynamic (sensitive to rate of change of muscle length. innervated by dynamic gamma MN)
-bag 2/ static (sensitive to absolute length of muscle, innervated by static gamma MN)

chain fibres;
- sensitive to absolute length of muscles, innervated by static gamma MN

156
Q

what types of afferent fibres innervate the intrafusal fibres

A

Ia (more sensitive to rate of change)
II (more sensitive to absolute length of intrafusal fibres)
both respond to stretch

rate of change= dynamic response
absolute length= steady state or static response

157
Q

which type of gamma fibres are active when

A

In activities in which muscle length changes slowly and predictably only static γ-MNs are active

Dynamic γ-MNs are active during behaviours in which muscle length changes rapidly and unpredictably

158
Q

what are golgi tendon organs

A

located at the junction of muscle and tendon
monitor changes in muscle tension
act to regulate muscle tension

159
Q

what innervates the golgi tendon organs

A

group Ib sensory afferents

160
Q

where do the Ib fibres go from the golgi tendon apparatus

A

enter spinal cord and synapse upon inhibitory interneurones which then synapse upon the alpha motor neurones of the homonymous muscles
(this forms the basis of the reverse myotatic reflex)

161
Q

what are the components of the reverse myotatic reflex

A

an inhibitory interneurone between an Ib afferent and an alpha MN
gets info from golgi tendon organ

162
Q

where are proprioceptive axons

A

in connective tissue of joints

can be fast or slow adapting for different movements

163
Q

what is the role of proprioceptive axons

A

Respond to changes in angle, direction and velocity of movement of a joint. Also prevent excessive flexion, or extension

164
Q

what are the three places proprioceptive information arises from

A

muscle spindles
golgi tendon organs
joint receptors

165
Q

what 4 sources do spinal interneurones recieve input from

A

primary sensory axons
descending axons from the brain
collateral branches of LMNs
other interneurones

this input may be excitatory or inhibitory
the interneurones themselves may be excitatory or inhibitory

166
Q

what is the role of interneurones

A

integrate incoming information to generate an output

167
Q

what do inhibitory interneurones mediate

A

the inverse myotatic response
and reciprocal inhibition between extensor and flexor muscles

explanation (Myotatic reflex causes the homonymous extensor muscle (quadriceps) to contract, but for the leg to extend the antagonist flexor muscle (hamstring) must simultaneously relax
the Ia afferent from the muscle spindle extensor makes an excitatory monosynaptic contact with the α-MN innervating the homonymous muscle. Via a polysynaptic pathway involving an inhibitory interneurone, the Ia fibre also inhibits the α-MN supplying the flexor muscle)

168
Q

what movement will initiate the myotactic reflex

A

voluntary contraction of an extensor will strecth an antagonist flexor- initiates reflex

169
Q

how are descending pathways involved in the myotactic reflex

A

descending pathways that activate the alpha MN controlling the agonist muscles also via inhibitory interneurones inhibit the alpha MN supplying the antagonist muscles allowing unopposed movement

170
Q

what do excitatory interneurones mediate

A

the flexor reflex and the crossed extensor reflex

171
Q

what is the flexor reflex

A

when noxious stimuli causes the limb to flex by

  • contraction of flexor muscles via EXCITATORY interneurones
  • relaxation of extensor muscles via EXCITATORY AND INHIBITORY interneurones
172
Q

what is the crossed extensor reflex

A

noxious stimuli causes the limb to extend by;

  • contraction of extensor muscles via EXCITATORY interneurones
  • relaxation of flexor muscles via EXCITATORY AND INHIBITORY INTERNEURONES
173
Q

what do the flexor and crossed extensor reflexes have in common

A

both act to aviod noxious stimuli
both contract muscles by excitatory interneurones
both relax muscles by excitatory and inhibitory interneurones

174
Q

how can a spinal central pattern generator command limb movement

A

by excitatory interneuones to display oscillatory or pacemaler activity (synchronicity of the flexor and extensor LMN circuits)

175
Q

what structures control the strategy of a movement (its aim and how it is best achieved)

A

neocortical assocaition areas

basal ganglia

176
Q

what structures control the tactics of a movement (what sequence of muscle contractions and relaxations will fulfil the strategic aim)

A

motor cortex and cerebellum

177
Q

what structures control the execution of a movement (activation of motor and interneurone pools)

A

brain stem and spinal cord

178
Q

what do the descending tracts arise from

A

cerebral cortex and the brain stem

179
Q

what do the descending pathways do

A

control movement, muscle tone, spinal reflexes, spinal autonomic function, modulation of sensory trasmission to higher centre (gate keeper)

180
Q

what controls the lateral descending pathways and what do they do

A

cerebral cortex

voluntary control of distal musculature- fine movements
lateral corticopsinal and rubrospinal tract

181
Q

what controls the ventromedial descending pathways and what do they do

A

brainstem

posture and locomotion
(reticulospinal tracts, lateral vestibulospinal tract, tectospinal tract, ventral corticospinal tract)

182
Q

what brodmans areas are responsible for the control of movement

A

4 and 6

183
Q

what is the other name for the corticospinal tract

A

pyramidal

184
Q

where are the cell bodies of the corticospinal tract found

A

in motor cortex (BA 4 and 6) and somatosensory areas of the parietal cortex

185
Q

what is the path of the corticospinal tract

A

motor cortex
base of medulla (form medullary pyramid)
fibres cross at the pyramidal decussation (form lateral corticospinal tract)
remainder stay ipsilateral (and form the ventral corticospinal tract which cross more caudally)
terminate in dorsolateral region of the ventral horn (location of LMN and interneurones)

186
Q

does the right or left hemisphere control the contra or ipsilateral side muscluclature via the corticospinal tract

A

contralateral

187
Q

where are the cell bodies of the rubrospinal tract

A

red nucleus (receives input from the motor cortex and the cerebellum)

188
Q

where do axons in the rubrospinal tract decussate

A

ventral tegmental decussation

189
Q

where does the rubrospinal tract terminate

A

ventral horn

190
Q

what muscles does the rubrospinal tract control

A

limb flexors

191
Q

what do lesions of the lateral columns cause

A

loss of fractionated movements

slowing and impairment of accuracy of voluntary movements

192
Q

where are the nuclei of the vestibulospinal tract

A

vestibular nuclei (medial and lateral)

193
Q

where do the vestibular nuclei receive input from

A 
CN VIII (vestibular nerve) from the vestibular labyrinth
and cerebellum
194
Q

what is the path of the vestibulospinal tract

A

axons from lateral vestibular nuclei descend ipsilaterally as the lateral vestibulo spinal tract to the lumbar spinal cord (this tract controls extensor MN of antigravity muscles)

axons form the medial vestublar nuclei descend as the medial vestibulospinal tract to the cervical spinal cord (control neck and back muscles guiding head movement)

195
Q

where are the cell bodies of the tectospinal tract - where do they get input from

A

superior colliculis (aka optic tectum)

get input from retina and visual cortex

196
Q

what is the path of the tectospinal tract

A

axons decussate in the dorsal tegmental decussation

descend to cervical spine (influence the muscles of the neck, upper trunk and shoulders)

197
Q

where do the potine and medullary reticulospinal tracts arise from

A

reticular formation

198
Q

what is the path and role of the pontine (medial) recticulospinal tract

A

descends ipsilaterally
enhances antigravity reflexes of the spinal cord
helps maintain posture- contracts extensors of the lower limbs

199
Q

what is the path and role of the medullary (lateral) recticulospinal tract

A

descends bilaterally
opposes the action of the medial tract
releases antigravity muscles from reflex control

Neurology (35 decks)

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