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Z MD1 neurology > physiology > Flashcards

physiology Flashcards

1
Q

what is the type of skin called that is not covered by hair and has skin ridges

A

glabrous skin

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2
Q

4 types of mechanoreceptors in glabrous skin

A

Meissner corpuscles

Merkel complexes

Ruffini organs

Pacinian corpuscles

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3
Q

where are Meissner corpuscles located

A

in the epidermis

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4
Q

where are Merkel complexes located

A

in the epidermal-dermal ridges

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5
Q

where are Ruffini corpuscles?

A

in the dermis

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6
Q

where are Pacinian corpuscles

A

in the subcutaneous layer

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7
Q

how do the mechanoreceptors of the skin create an AP

A

the distortion of the skin causes an opening of Na channels –> AP

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8
Q

what is the difference between slow and rapid adapting fibres?

A

slow - have an ongoing response - tells you about the ongoing stumulus

rapid - fire only with a change in stimulus

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9
Q

what do pacinian corpuscles respond to, and how big are their receptor fields

A

vibration - relatively large R fields compared to Meissners corpuscles

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10
Q

which mechanoreceptors of the skin are slow adapting and which are rapidly adapting

A

merkel complexes and Ruffini endings - slow

meissner and pacinian - fast

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11
Q

what do merkel complexes respond to

A

indentation of the skin

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12
Q

what do ruffini endings respond to

A

skin movement - tells you about posture

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13
Q

what do meissner receptors respond to

A

transient response to skin movement

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14
Q

which mechanoreceptors are superficial and which are deep

A

superficial - meissner and merkel

deep - ruffini and pacinian

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15
Q

which mechanoreceptors have a high density of receptors and which have a low density

A

high - merkel and meissner

low - pacinian and ruffini

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16
Q

when picking up an object with your hand… which receptors convey what information

A

meissner - encode rate of force

merkel - encode grip force

pacinian - encode vibrations

ruffini encode hand posture

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17
Q

what is a receptor field

A

a measure of how much territory a single receptor is responsive to

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18
Q

in which areas of the body are the receptor fields in a high density

A

in the hands, feet and face

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19
Q

what is the approx conduction velocity of sensory fibres for touch

A

~50m/s - fast (highly myelinated)

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20
Q

how many dermatomes do we have

A

31

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21
Q

why are the dermatomal patterns and the peripheral nerve patterns different at the periphery

A

due to the formation of plexuses

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22
Q

in what “column” does sensory (touch) information travel in?

A

the posterior/dorsal columns

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23
Q

what is the gross regional topography of the posterior columns in the spinal cord

A

lower body is more medial and upper body is more lateral

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24
Q

where does the decussation of somatosensory (touch) neurons occur?

A

in the caudal medulla (at the top of the posterior columns)

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25
Q

what are the 2 general areas of the posterior columns called that take information from the lower limbs and the upper limbs

A

lower limbs = gracile fasiculus

upper limbs = cuneate fasiculus

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26
Q

how many neurons are involved in the chain for the somatosensory pathway

A

3 (first to caudal medulla, second to thalamus and third to cortex)

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27
Q

in what area of the caudal medulla do somatosensory information synapse with the 2nd neuron of the sequence for upper and lower limb information

A

upper limb = cuneate nucleus

lower limb = gracile nucleus

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28
Q

somatosensory pathway: after decussating, what is the tract called in which they ascend?

A

the medial lemniscus

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29
Q

what is the change in orientation of the areas corresponding for the upper and lower limb somatosensory information through the medial lemniscus (anatomy)

A

at decussation - on the ventral side (lower limb info lower than upper limb info) then twist laterally to the R side with lower limb more lateral then twist again so in the cortex - the lower limb is above the upper limb info

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30
Q

what are the internal arcuate fibres of the somatosensory pathway?

A

the neurons that decussate in the caudal medulla

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31
Q

where does the medial lemniscus go to?

A

the ventral posterolateral nucleus of the thalamus

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32
Q

where can lesions be if you have lost touch sensation on the left side

A
  • epsilateral side of the spinal cord or peripheral nerve
  • contralateral part of the brain
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33
Q

where is the primary somatosensory cortex located

A

in the postcentral gyrus

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34
Q

what are the 4 subdivisions of the primary somatosensory cortex

A

1, 2, 3a, 3b

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35
Q

where does information come from for the secondary somatosensory cortex

A

from both the primary somatosensory cortex and the thalamus directly

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36
Q

which region of the primary somatosensory pathway does the majority of information go to

A

3b

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37
Q

which region of the primary somatosensory pathway goes on to give info to the posterior parietal cortex

A

region 2

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38
Q

what is neuroplasticity

A

changes in neural pathways and synapses which are due to changes in behavior, environment and neural processes, as well as changes resulting from bodily injury (cortex does not waste space)

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39
Q

where is the site for lumbar puncture

A

L3-L4

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40
Q

what is the composition of the spinal cord (in terns of white and grey matter) as you move up the spinal cord

A

more and more white matter (more fibres have joined the spinal cord)

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41
Q

what are alpha motor neurons

A

motor neurons that directly innervate skeletal muscle and have connections to sensory inputs

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42
Q

what is the topography of the motor neurons in the ventral horn

A

the more lateral –> the more distal and the further away from the midline

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43
Q

what is a motor neuron pool

A

all of the neurons that innervate a certain muscle

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44
Q

what detects stretch of the muscle

A

specialised sensory fibre in the muscle encapsulated in a protective sheath

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45
Q

what innervates the specialised sensory fibres for stretch in muscle and why?

A

gamma motor neurons - to allow it to adjust its position in accordance to movement of the muscle

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46
Q

what are the only muscles of the body without specialised sensory fibres for stretch?

A

intraocular muscles

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47
Q

what detects force of the muscle

A

Golgi Receptors

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48
Q

explain the monosynaptic reflex mechanism

A

1) tap on the tendon of extensor muscle –> causes stimulation of a sensory neuron
2) stimulates the motor neuron of the extensor muscle (excitatory) –> contraction
3) stimulates the inhibitory interneuron to cause relaxation of the flexor muscle

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49
Q

what is the monosynaptic reflex needed for

A

in order to maintain postural tone

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50
Q

explain the force (Golgi) reflex of muscle

A

1) Golgi receptor detects force on the extensor muscle
2) stimulates sensory neuron
3) stimulates inhibitory interneuron to cause inhibition and therefore relaxation of the extensor
4) stimulates excitatory interneuron to cause stimulation and therefore contraction of the flexor (excites the antagonistic muscle)

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51
Q

what is a lower motor neuron

A

the cholinergic motor neuron in the ventral horn that innervate skeletal muscle

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52
Q

what is an upper motor neuron

A

any neuron that effects the excitability of the LMN

53
Q

what are the UMN lesion symptoms

A

hyper-reflexes and spastic contraction

54
Q

what are the LMN lesion symptoms

A

muscle atrophy and no contraction and no reflexes

55
Q

why do you get hyper-reflexes and spastic contraction when you have a UMN lesion

A

because the UMN is usually providing primarily inhibitory signals to the LMN, and therefore with a lesion - this inhibition is lost and the LMN is therefore over excited

56
Q

what are the 4 types of pain

A

nociceptive pain - physiological

inflammatory pain - physiological

neuropathic pain - pathological

functional pain syndromes - pathological

57
Q

what is the difference between nocioception and pain?

A

nocioception is the pathway from transduction the cortex pain is the higher order process that occurs in the cortex to tell you its painful

58
Q

what types of things do nocioceptors detect

A

Protons

high levels of heat

noxious cold

intense mechanical force/pressure

chemical irritants

59
Q

what are the fibres involved in nocioception? and what are their difference from each other

A

C fibres - not myelinated, go only to the most superficial layers of the dorsal horn laminae

A-delta - myelinated, go down to the deep layers of laminae of the dorsal horn (also superficial)

60
Q

what is the difference between nocioceptors and pacinian corpusles in regards to transduction?

A

pacinian corpusles only send signals when the stimulus is still there nocioceptors continue to send signals when the stimulus is removed to signal tissue damage

61
Q

what is the timeline of signals sent by C fibres and A-delta fibres with a stimulus

A

A-delta signal sent initially = sharp pain, precisely localised Then followed by slow, burning, throbbing pain by the C fibres

62
Q

which pathway carries nocioception to the brain

A

anterolateral system (cross over in the spinal cord)

63
Q

what are the two synapses made by fibres carrying nocioception

A

1) reflex pathway in the spinal cord through interneuron and motor neuron to remove body from the stimulus
2) anterolateral system to the cortex for “pain” recognition

64
Q

why can inflammatory pain by spontaneous and continuous

A

due to the inflammatory mediators released by the tissue damage –> pain

65
Q

which receptor does capsaicin activate

A

TRPV1 (heat receptor)

66
Q

how does capsaicin cause “heat”

A

TRPV1 opened –> drops the threshold for activation so that the channels is always open, so that you detect the heat at normal temperatures

67
Q

what can sensitisation of the fibres carrying nocioception ultimately cause

A

allodynia - painful response to a normally innocuous stimulus hyperalgesia - an increased response to a normally painful stimulus

68
Q

what is secondary hyperalgesia

A

when sensitisation has occured in the level of the spinal cord –> there is an expansion of the area that is sensitised

69
Q

what is maladaptive pain

A

pain that does not respond to drug treatment

70
Q

what is neuropathic and dysfunctional pain

A

neuropathic pain - some kind of damage to the somatosensory system itself

dysfunctional pain - no neural leasions and no identifiable tissue or physiological pathology can be identifed

71
Q

what causes peripheral neuropathic pain

A

when the nerve has been damaged –> causes generation of pain signals when there is no stimulation of these terminals

72
Q

what is the major system in which emotions can influence pain, and how does it work?

A

through the PAG system - relays through the ventral medulla down to the dorsal horn of the spinal cord and vice versa

73
Q

explain the “top down psychological modulation of pain”

A

fear through amygdala, anterior cingulate, prefrontal cortex and insula –> engages the descending pain modulation system (PAG) –> pain desensitivity

74
Q

the ANS innervates everything except

A

CNS tissue and skeletal muscle

75
Q

what is the anatomical difference of the SNS and PNS

A

SNS fibres originate from the thoraco-lumbar spinal cord and have ganglia close to the spinal cord/far away from organs

PNS fibres originate from the cranial and sacral spinal cord and have ganglia close to the organs/far from the spinal cord

76
Q

what are the two ganglia associated with the SNS

A

para-vertebral

pre-vertebral

77
Q

what are the NTs associated with the PNS and SNS

A

SNS - ACh (N) (pre) –> NA mostly with ACh (M) to glands PNS - ACh (N) (pre) –> ACh (M)

78
Q

what is the difference in myelination in the autonomic nervous system

A

pre ganglionic fibres are lightly myelinated or unmyelinated while postganglionic are all unmyelinated

79
Q

what are extra-junctional responses

A

where receptors for a NT can be expressed remotely from the synapse (and therefore can be affected by exogenous agonists)

80
Q

what parts of the spinal cord do the pre-ganglion fibres of the SNS and PNS come from

A

SNS - intermediolateral cell column

PNS - intermediate grey column (sacral fibres), brainstem (cranial)

81
Q

what is the purpose of having ganglia for the SNS

A

essential for integration and coordination of sympathetic control between organs/tissues

82
Q

what are the primary purposes of the prevertebral ganglia and the paravertebral ganglia

A

pre - innervate non-vascular smooth muscle

para - innervation for vasoconstriction of BVs

83
Q

explain the concepts of divergence and convergence of postganglionic Sympathetic fibres

A

divergence - one post ganglionic fibre can activate many, many neurons

convergence - lots of preganlionic fibres converge and integrate their message onto one post-ganglionic fibres

84
Q

is the adrenal medulla innervated by pre or postganlgionic SNS fibres

A

pre

85
Q

what are the 4 parasympathetic nuclei in the brainstem

A

Edinger Westphal

salivatory nucleus

dorsal motor nucleus of vagus

nucleus ambiguus

86
Q

what is the rule breaking of the pelvic plexus

A
  • many of the parasympathetic ganglion neurons have unusually long axons contain many sympathetic neurons = mixed ganglia
87
Q

true or false - the typical autonomic reflex does not involve the brain

A

False (most autonomic reflexes involve the brain)

88
Q

where is the central processing centre for the afferent signals of the autonomic nervous system

A

the nucleus of the solitary tract

89
Q

what are the projections of the nucleus of the solitary tract for the autonomic system

A
  • provide feedback to the local reflexes
  • provide information to higher centres to drive more complex responses
90
Q

what is the central processing centre for the efferent output of the autonomic nervous system from the brain

A

the hypothalamus

91
Q

what is the action of the hypothalamus in the ANS

A

compares situations to biological set points and if there is a deviation, it initiates and coordinates an appropriate response

92
Q

what is the advantage of having a large motor end plate of LMNs

A

they can innervate multiple muscle fibres = motor unit

93
Q

What is Henneman’s size principle

A

As you want a bigger force you recruit larger and larger motor units (leave the largest motor units until last)

94
Q

Why is the neuromuscular synapse described as “secure” and 1:1?

A

because as soon as a signal impulse comes down the fibres, it will contract impulse=contraction

95
Q

what type of Receptor is used at a neuromuscular endplate

A

Nicotinic ACh receptor

96
Q

What causes fibrillations of a muscle

A
  • hypersensitivity of the R - increased ACh R expression
97
Q

what are fibrillations

A

tiny contraction caused by activity of a single muscle cell

98
Q

what are fasciculations

A

groups of muscle fibres contracting involuntarily

99
Q

what causes fasciculations

A

probably due to spontaneous activation of a degenerating motor neuron

100
Q

what are the two receptors involved in the monosynaptic reflex

A

intrafusal muscle fibre Rs - encode length

Golgi tendon organs - encode force

101
Q

LMN signs

A

weakness/paralysis

decreased superficial reflexes

hypoactive deep reflexes

decreased tone

fasiculations and fibrilaltions

severe muscle atrophy

102
Q

what are the two spinal cord pathways involved in motor control

A

lateral corticospinal tract

ventromedial pathways

103
Q

explain the topography of the LMNs synapse to the UMN in the ventral horn

A

lateral = distal muscles

medial = proximal muscles

104
Q

what is the major role of the lateral and medial vestibulospinal tracts

A

postural control - role in ongoing postural maintenance

105
Q

what is the major role of the reticulospinal tract

A

role in maintaining muscles in the midline - role in the position of the body

106
Q

what is the major role of the colliculospinal tract

A

role in orientation reflexes also initiates the reflex that prevents falling

107
Q

UMN signs

A

spasticity

increased tone

hyperactive deep reflexes

clonus

babinskis sign

loss of fine voluntary movement

108
Q

explain the body positioning of decerebrate and decorticate rigidity

A

decerebrate - both upper and lower limbs are extended

decorticate - upper limbs flexed while lower limbs are extended

109
Q

what is the use of looking at whether someone has decerebrate or decorticate rigidity

A

tells you where abouts the disconnection is between the brain and the spinal cord

110
Q

what structures in the brain influence decerebrate and decorticate ridigity? and where are they?

A

Red nucleus - midbrain

reticular formation - medulla and pons

111
Q

why do you get decorticate rigidity

A

loss of inhibitory control over the red nucleus and the reticular formation

  • red nucleus - causes flexion of upper limbs
  • reticular formation - causes extension of both upper and lower limbs
  • (flexion wins in the upper arms)
112
Q

why do you get decerebrate rigidity

A

loss of inhibitory control over the reticular formation and no longer influenced by the midbrain

  • reticular formation - causes extension of both upper and lower limbs
113
Q

what does babinski’’s sign mean

A

that the brain is no longer in normal control of the motor neurons originating in the spinal cord that control the muscles of the foot

114
Q

why is there different patterns of motor loss to the face

A

because some cranial nuclei receive bilateral innervation while others dont (lower facial muscles and hypoglossal nuclei)

115
Q

what are the UMN and LMN signs on the face

A

UMN - weakness of inferior facial muscles only

LMN - weakness of both superior and inferior facial muscles

116
Q

what are the two “outputs” for motor control

A

anticipation and movement

117
Q

what spinal “tract” is presumably involved in the anticipation of a movement

A

the ventral corticospinal tract that does not cross (ipsilateral)

118
Q

where does the locomotion pattern generator originate

A

in the lumbar-sacral spinal cord

119
Q

what initiates the swing phase of locomotion

A

the sensory feedback from extensor muscles

120
Q

how is the cortex involved in the pattern generator

A

its not its only responsible for altering it in anticipation of a change

121
Q

where is the division between information traversing the gracile and cuneate fasiculi

A

gracile - T7 and below

cuneate - T6 and above

122
Q

what is the topographical arrangment of UMN-LMN synapses to do with flexors and extensor, and proximal and distal muscles

A

proximal - medial

distal - lateral

flexors - dorsal

extensors - ventral

123
Q

how do sensory neurons traverse from the lateral ventroposterior nucleus of the thalamus to S1

A

through the internal capsule

124
Q

what three pathways are in the anterolateral system

A

spinothalamic (anterior and lateral)

spinoreticular

spinotectal

125
Q

What is the Tract of Lissauer

A

the fibres carrying pain, temp and crude touch that enter the dorsal horn go into the tract of lissauer where they ascend or descend 1-2 spinal nerve segments where they synapse at the dorsal horn of that level

126
Q

explain the second order neuron of the spinothalamic pathway

A

starts off from its synapse within the dorsal horn and then decussates to the contralateral side via the anterior white commissure and then travels up the anterolateral segment of the spinal cord in the lateral funiculus until it reaches the lateral ventroposterior nucleus and synapses with 3rd order neuron

127
Q

explain the route of the 3rd order neuron of the spinothalamic pathway

A

travels from the lateral ventroposterior nucleus of the thalamus up the internal capsule to S1

128
Q

what are the 2 types of LMN

A

alpha motor neuron

gamma motor neuron

129
Q
A

Z MD1 neurology (17 decks)

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