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Flashcards in Physiology Deck (199):
1

what do dendrites do

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

2

what does the soma contain

nucleus, ribosomes, mitochondria, endoplasmic reticulum

3

what is the axon hillock and initial segment

site of initiation of the all or non action potential

4

what is the role of the axon

conducts ouput signals as action potentials to the presynaptic terminal

5

what is the synapse

point of chemical communication between neurones

6

what type of neurones are: peripheral autonomic neurones

unipolar

7

what type of neurones are: dorsal root ganglions

pseudounipolar (one neurite that bifurcates)

8

what type of neurones are: retinal neurones

bipolar (2 neurites)

9

what type of neurones are: lower motor neurones

mulitpolar (3 or more neurites)

10

what is a neurite

process that arises from a soma

11

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

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

12

what is membrane potential change

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

13

how does passive conduction affect action potential velocity

passive conduction is a factor in AP propagation
the further the local current spread the fast the AP conduction velocity

14

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

increase membrane resistance (myelination)
decrease axial resistance of axoplasm (increase axon diameter)

15

what cells myelinate

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

16

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

faster

17

what is saltatory conduction

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

18

name two demyelinating disorders

mulitple sclerosis (CNS)
guillian barre (PNS)

19

what are the steps of chemical neurotransmission

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

20

what is the synaptic cleft

gap between pre and post synaptic membranes

21

what is in the synaptic cleft

fibrous extracellular protein

22

what holds the neurotransmitter in the synapse

vesicles in the pre synaptic terminal

23

what are the synaptic membrane differentiations

presynaptically- active zones around which vesicles cluster

postsynaptically- the postsynaptic density which contains neurotransmitter receptors

24

what are the morpholgical types of synapses

axodendritic
axosomatic
axoaxonic

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

25

what is the most common CNS neurotransmitter for excitatory synapses

glutamate

26

what is the most common CNS neurotransmitter for inhibitory synapses

GABA or glycine

27

what is the inhibitory/ excitatory post synaptic potential

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

28

what type of neurotransmitters are glutamate, GABA and glycine

amino acid

29

what is synaptic integration

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)

30

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

amines

31

what type of neurotransmitter are cholecystokinin
dynorphin
enkephalins
neuropeptides
somatostatin
substance P
TRH
vasoactive intestinal polypeptide

peptides

32

what releases acetylecholine, amino acids and amines

synaptic vesicles

33

what releases peptides

secretory vesicles

34

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

ionotropic ligand gated ion channels

mediate fast neurotransmission

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

35

what is direct gating

when neurotransmitters act directly on the ion channel
done by ionotropic receptors

36

what is indirect gating

when neurotransmitters acts indirectly on the ion channel
mediated by activation of metabotropic receptors

37

what causes fast excitatory postsynaptic potentials

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

38

what causes slow excitatory postsynaptic potentials

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

39

via what does glutamate have inhibitory effects

metabotrophic glutamate receptors

40

how can Ionotropic Glutamate receptors be classified

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+

41

what do non NMDA ionotropic receptors (AMPA and kainate)
do

mediate fast excitatory synaptic transmission in the CNS

42

what do NMDA ionotropic receptors do

contributes a slow component to the excitatory synaptic potential

43

what is the clinical relevance of NMDA receptors

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

44

how do metabotropoc glutamate work

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


Role is modulation of neurotransmission.

45

what is mechanosensation

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

46

what is nociception

pain

47

what is the exteroceptive division of somatosensation

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

48

what is the proprioceptive division of somatosensation

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

49

what is the enteroceptive division of somatosensation

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

50

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

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

51

where in brain does proprioceptive input go to

cerebellum

52

what potential does a sensory stimulus create

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

53

what does a supra threshold receptor potential trigger

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

54

what is an all or none response

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

55

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

a graded release of neurotransmitter on to second order neurones

56

what is the modality of a sensory unit

what type of stimulus excited it (the adequate stimulus)

57

what is the threshold of a sensory unit

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

58

what is the adaption rate of a sensory unit

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)

59

what is the conduction velocity of a sensory unit

how rapidly it conducts APs along its axon

60

what is the receptive field of a sensory unit

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

61

what is the sensory unit for pain

mechanical, thermal and polymodal nociceptors

62

what mediates discriminatory touch

low threshold mechanoreceptors

63

what are high threshold units

nociceptors:
mechano
thermal
chemical
polymodal

64

what are polymodal nociceptors

respond to at least 2 types of stimuli

65

what do slow adapting units respond to

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

66

what do fast adapting units do

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

67

what do very fast adapting units do

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)

68

what do Aalpha axons do

proprioceptors of skeletal muscle

69

what do Abeta axons do

mechanoreceptors of skin

70

what do Adelta axons do

temperatures, pain

71

what do C axons do

temperature, pain and itch

72

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

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

73

what is the receptive field

the target territory from which a sensory unit can be excited

74

how is receptive field relative to innervation density

inversely proportionate

low density of innervation= large RF= high sensory acuity

75

what do afferent nerve fibres end in

either free nerve endings (partially naked)
or associated with specialised structures

76

what is spatial acuity

two point discrimination

77

where do you not get meissners copuscles

hairy skin

78

where are ruffini endings and what do they do

within dermis
pressure sensation

79

where are pacinian corpuscles and what do they do

semis and fascia
pressure

80

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

sense touch

81

what do free nerve endings sense

pain, temperatuere

82

how are low threshold mechanoreceptors classified

by their rates of adaption and size of receptive field

83

what are the low threshold mechanoreceptoes

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

84

does a pacinian or meissners corpuscle have a bigger receptive field

pacinian

85

which has a higher human detection threshold meissner or pacinain corpuscle

meissners

86

at what frequency are are pacinian corpuscles most sensitive

150- clinical test using a 128Hz tuning fork

87

what part of nerve is affected in shingles

dorsal root ganglion

88

what virus is shingles

varicella zoster

89

what class of fibres are nociceptors

Adelta and C

90

what class of fibres are low threshold mechanoreceptors

Abeta

91

what class of fibres are proprioceptors

Aalpha

92

what is the grey matter of the spinal cord divided into

10 distinct laminae of rexed

93

how does the dorsal medial lemniscal pathway ascend

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

what does the dorsal column medial leminscal pathway carry

info on discriminatory touch, pressure, vibration, conscious proprioception

95

how does the spinothalamic tract ascend

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

96

what does the spinothalamic tract do

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

97

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

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

what do the dorsal and ventral spinocerebella tracts do

convey unconscious proprioceptive information to the cerebellum

99

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

dorsal column medial lemniscial pathway

100

what are the capabilities of the dorsal column medial lemniscal pathway

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

101

what is contrast enhancement

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

what is the point of lateral inhibition

sharpens stimulus perception

103

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

trigeminal sensory ganglion

104

what is the path of the trigeminal nerve to the brain

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

what makes up the central sulcus

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

106

what parts of body on what parts of the somatosensory cortex

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

how is the somatosensory cortex organised

is layered and columnar

108

are somatotopic maps constant

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

what does the posterior parietal cortex do

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

what can damage to the posterior parietal cortex cause

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

where are upper and lower motor neurones

upper in brain
lowerin brainstem and ventral horn of the spinal cord

112

what is the relationship between upper and lower motor neurones

UMN supply input to LWN to modulate their activity

113

what do LWN recieve input from

upper motor neurones
proprioceptors
interneurons

114

what commands muscle contraction

lower motor neurones

115

what makes up lower motor neurones

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

116

what do gamma motor neurones do

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

117

give examples of synergistic muscles

biceps brachii and brachialis
triceps brachii and anconeus

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

118

what do axial muscles do

control the movement of the trunk (posture)

119

where are proximal or girdle muscles

shoulder, elbow, pelvis and knee

120

how do axons of lower motor neurones leave the spinal cord

in central roots (or via cranial nerves)

121

what is a motor unit

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

122

what is a motor neurone pool

a collection of alpha motor neurones that innervate a single muscle

123

how do alpha motor neurones grade force of muscle contraction

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

124

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

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

125

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

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

126

what does muscle stength depend on

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

what needs to summate for a muscle to contract

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

128

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

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

129

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

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

130

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

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

what are type I muscle fibres

slow oxidative

132

where do slow oxidative muscle fibres get their ATP from

oxidative phosphorylation

133

what do slow oxidative fibres do (type I)

slow contraction and relaxation
fatigue resistant
antigravity, sustained movement

134

why are slow oxidative fibres red

high myoglobin content

135

what are type II muscle fibres

fast types:
-type IIa
-type IIx (or IIb)

136

where do type II fibres get their ATP from

type IIa- oxidative phosphorylation

type IIx- glycolysis

137

what do type IIa muscle fibres do

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

138

what do type IIx muscle fibres do

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

139

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

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

how does the tension change between types of muscle fibres

IIX- very high
IIa- high
I-low

141

what is the henneman size principle

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

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

a fine control of muscle force

143

what is the myotatic reflex

when a skeletal muscles is pulled it contracts

144

what does a muscle spindle to

senses change in length and rate of this change
contributes to non conscious proprioception

145

what makes up a muscle spindle

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

what are the steps of the myotatic reflex

(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

what spinal level does the biceps jerk test

C5-C6

148

what spinal level does the supinator (wrist) jerk test

C5-C6

149

what spinal level does the triceps jerk test

C7

150

what spinal level does the quadriceps (knee) jerk test

L3-4

151

what spinal level does the gastocnrmius (ankle) jerk test

S1

152

what can reinforce the knee jerk

jendrassik maneeuvre (pulling apart interlocked fingers)

153

what are intrafusal fibres made up of

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

what happens to alpha and gamma MN during voluntary movement

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

155

what are the types of intrafusal muscle fibres

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

what types of afferent fibres innervate the intrafusal fibres

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

which type of gamma fibres are active when

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

what are golgi tendon organs

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

159

what innervates the golgi tendon organs

group Ib sensory afferents

160

where do the Ib fibres go from the golgi tendon apparatus

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

what are the components of the reverse myotatic reflex

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

162

where are proprioceptive axons

in connective tissue of joints
(can be fast or slow adapting for different movements)

163

what is the role of proprioceptive axons

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

164

what are the three places proprioceptive information arises from

muscle spindles
golgi tendon organs
joint receptors

165

what 4 sources do spinal interneurones recieve input from

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

what is the role of interneurones

integrate incoming information to generate an output

167

what do inhibitory interneurones mediate

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

what movement will initiate the myotactic reflex

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

169

how are descending pathways involved in the myotactic reflex

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

what do excitatory interneurones mediate

the flexor reflex and the crossed extensor reflex

171

what is the flexor reflex

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

what is the crossed extensor reflex

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

what do the flexor and crossed extensor reflexes have in common

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

174

how can a spinal central pattern generator command limb movement

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

175

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

neocortical assocaition areas
basal ganglia

176

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

motor cortex and cerebellum

177

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

brain stem and spinal cord

178

what do the descending tracts arise from

cerebral cortex and the brain stem

179

what do the descending pathways do

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

180

what controls the lateral descending pathways and what do they do

cerebral cortex

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

181

what controls the ventromedial descending pathways and what do they do

brainstem

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

182

what brodmans areas are responsible for the control of movement

4 and 6

183

what is the other name for the corticospinal tract

pyramidal

184

where are the cell bodies of the corticospinal tract found

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

185

what is the path of the corticospinal tract

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

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

contralateral

187

where are the cell bodies of the rubrospinal tract

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

188

where do axons in the rubrospinal tract decussate

ventral tegmental decussation

189

where does the rubrospinal tract terminate

ventral horn

190

what muscles does the rubrospinal tract control

limb flexors

191

what do lesions of the lateral columns cause

loss of fractionated movements
slowing and impairment of accuracy of voluntary movements

192

where are the nuclei of the vestibulospinal tract

vestibular nuclei (medial and lateral)

193

where do the vestibular nuclei receive input from

CN VIII (vestibular nerve) from the vestibular labyrinth
and cerebellum

194

what is the path of the vestibulospinal tract

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

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

superior colliculis (aka optic tectum)

get input from retina and visual cortex

196

what is the path of the tectospinal tract

axons decussate in the dorsal tegmental decussation
descend to cervical spine (influence the muscles of the neck, upper trunk and shoulders)

197

where do the potine and medullary reticulospinal tracts arise from

reticular formation

198

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

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

199

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

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