Neurophysiology

Question 1

Give an example of a unipolar cell

Answer 1

Peripheral autonomic neurone

Question 2

Give an example of a bipolar neurone

Answer 2

Retinal

Question 3

Where are passive signals found in the neurone?

Answer 3

In the dendrites and body (NOT the axon)

Question 4

Describe spatial summation

Answer 4

Lot of inputs into neurone

Signals converge to determine output

Question 5

Describe temporal summation

Answer 5

Single input

Modulates output by variation in action potential FREQUENCY

Question 6

Give an example of an ionotropic and metabotropic receptor.

Answer 6

Ionotropic - nicotinic receptor

Metabotropic - muscarinic receptor

Question 7

What are the main 2 differences between non-NMDA and NMDA receptors

Answer 7

NMDA is slow and transmits calcium as well as potassium and sodium.

Question 8

Are NMDA and non-NMDA receptors ionotropic or metabotropic?

Answer 8

Both ionotropic

Question 9

Where are the cell bodies of second order neurones in the somatosensory system?

Answer 9

Dorsal horn of spinal cord
OR
CN nuclei

Question 10

Where are the cell bodies of third order neurones in the somatosensory system?

Answer 10

Thalamus

Question 11

What is another name for high threshold units?

Answer 11

Nociceptors

Question 12

Describe slow adapting neurones and give an example

Answer 12

Continously fire while stimulus detected

Stretch receptors

Question 13

Describe fast adapting neurones and give an example

Answer 13

Detects change in stimulus strength
Number of impulses proportional to rate of change
E.g. muscle spindle, hair follicle afferents

Question 14

Describe very fast adapting neurones and give an example

Answer 14

Responds only to V fast movement such as rapid vibration

Pacinian corpuscle

Question 15

Give an example of Aalpha fibres

Answer 15

Proprioceptors

Question 16

Give an example of Abeta fibres

Answer 16

Mechanoreceptors in skin

Question 17

Give examples of Adelta fibres

Answer 17

Pain

Temp

Question 18

Give examples of C fibres

Answer 18

Temp
Pain
Itch

Question 19

What is a type 1 and type 2 receptive field?

Answer 19

Type 1 - small receptive field

Type 2 - large receptive field

Question 20

What are the laminae of Rexed?

Answer 20

10 areas of the grey matter of the spinal cord

Question 21

What laminae of Rexed do nociceptors go to?

Answer 21

I and II

Question 22

What laminae of Rexed do low threshold mechanoreceptors (Abeta) fibres go to?

Answer 22

III to VI

Question 23

What laminae of Rexed do proprioceptors go to?

Answer 23

VII to IX

Question 24

Which of the fasciculus gracilis and fasciculus cuneatus are lateral and medial?

Answer 24

Medial - fasciculus gracilis

Lateral - fasciculus cuneatus

Question 25

From lateral to medial, what spinal levels are the white matter in the dorsal columns of the spinal cord?

Answer 25

Cervical -> sacral

Question 26

Where in the thalamus do the neurones from the dorsal columns synapse?

Answer 26

The ventral posterior lateral (VPL) nucleus of the thalamus

Question 27

What is stereognosis?

Answer 27

Ability to recognise an object by feeling it.

Question 28

What is contrast enhancement?

Answer 28

As info goes up the sensory pathway, the differences in activity of adjacent neurones are amplified e.g. through lateral inhibition.

Question 29

Describe lateral inhibition.

Answer 29

When one neurone is activated, it inhibits the activity of its neighbours via inhibitory interneurones.

Question 30

Where in the thalamus do neurones from the trigeminal system go to?

Answer 30

Ventroposteriomedial (VPM) nucleus

Question 31

What Brodmann areas make up the somatosensory cortex?

Answer 31

1, 2, 3a and 3b

Question 32

What layer of the somatosensory cortex receives inputs from the thalamus and is this superficial or deep?

Answer 32

Layer IV | Deep (goes from I-VI with I being the most superficial)

Question 33

What is the function of the posterior parietal cortex?

Answer 33

Deciphers deeper meaning of the info from the somatosensory cortex.

Question 34

Where in the spinal cord are more LMNs found?

Answer 34

The cervical and lumbar enlargements.

Question 35

What 3 inputs can there be to an alpha motor neurone?

Answer 35

DRG cells innervating muscle spindle UMNs Spinal interneurones

Question 36

Describe the alpha motor neurones innervating fast type muscle in comparison to slow type.

Answer 36

Fast type - larger with faster conducting axons.

Question 37

Describe type I, IIa and IIb/x muscle fibres.

Answer 37

I - ATP from oxidative phosphorylation, red (high myoglobin), slow contraction, fatigue resistant IIa - ATP from oxidative phosphorylation, red, fast contraction, fatigue resistant IIb/x - ATP from glycolysis, white, fast contraction, not fatigue resistant

Question 38

Are smaller or larger alpha-motor neurones activated more easily?

Answer 38

Smaller

Question 39

In what order are muscle fibres activated with increasing tension?

Answer 39

Type I -> type IIa -> type IIx

Question 40

What is the myotatic reflex?

Answer 40

When a skeletal muscle is pulled, it pulls back (stretch reflex)

Question 41

What do muscle spindles consist of?

Answer 41

Fibrous capsule Intrafusal muscle fibres Sensory afferents (myelinated fast conduction) Gamme motor neurone

Question 42

How many synapses are involved in the myotatic (stretch) reflex?

Answer 42

One (monosynaptic)

Question 43

In what muscles is the myotatic reflex most prominent in?

Answer 43

Extensors

Question 44

What part of intrafusal fibres are contractile?

Answer 44

The polar ends.

Question 45

What are the 3 types of muscle spindle fibres, what type of afferent and efferent fibres innervate them and what are they sensitive to?

Answer 45

Nuclear bag 1 fibres - Ia afferents, dynamic gamma motor neurones, rate of change of muscle length. Nuclear bag 2 and chain fibres, Ia and II afferents, static gamma motor neurones, absolute muscle length.

Question 46

What are the 2 types of afferent fibres of the muscle spindle and what do they do?

Answer 46

Ia - wrap around centre of all intrafusal fibres, sense rate of change. II - wrap around bag 2 and chain fibres, more sensitive to absolute length.

Question 47

When are static gamma MNs active and when are dynamic ones active?

Answer 47

Static - when muscle length changes slowly and predictably. | Dynamic - when muscle length changes rapidly and unpredictably.

Question 48

What type of sensory afferent innervates golgi tendon organs?

Answer 48

Ib

Question 49

What reflex involves golgi tendon organs?

Answer 49

The reverse myotatic reflex.

Question 50

Describe the reverse myotatic reflex.

Answer 50

Golgi organ stimulated -> Ib afferent stimulated -> inhibitory interneurone in spinal cord -> alpha motor neurone inhibited.

Question 51

How do interneurones affect the myotatic reflex?

Answer 51

The afferent neurone from the spindle will synapse both with the alpha motor neurone of the extensor and an inhibitory interneurone. This interneurone will then inhibit the alpha motor neurone of the flexor muscle.

Question 52

Why is the myotatic reflex of a flexor not activated when an extensor contracts?

Answer 52

Descending control from the motor cortex to inhibitory interneurones inhibits the alpha motor neurones of antagonistic muscle

Question 53

Describe the flexor and crossed extensor reflex.

Answer 53

``` Noxious stimuli causes activation of neurones causing ipsilateral limb to flex. Also causes (through excitatory interneurones) the contralateral limb to extend. ``` Enhances postural support.

Question 54

What controls the lateral and ventromedial descending spinal tracts?

Answer 54

Lateral - cerebral cortex | Ventromedial - brainstem

Question 55

Where does the rubrospinal tract start and what is it's main function?

Answer 55

The red nucleus in the midbrain | Limb flexion

Question 56

What is the function of the lateral vestibulospinal tract?

Answer 56

Extension of antigravity muscles

Question 57

What is the function of the medial vestibulospinal tract?

Answer 57

Activate cervical spinal circuits that control neck and back muscles guiding head movements.

Question 58

Where does the tectospinal tract start and what is its function?

Answer 58

The superior colliculus of the midbrain (optic tectum) | Influences muscles of neck, upper trunk and shoulders to orientate head and eyes to new visual stimuli

Question 59

What is the function of the pontine (medial) reticulospinal tract?

Answer 59

Maintains posture by contracting extensor muscles of lower limbs

Question 60

What is the function of the medullary (lateral) resticulospinal tract?

Answer 60

Opposes medial tract action | Releases antigravity muscles from reflex control

Question 61

What is the pathway for signal transmission in the retina?

Answer 61

Photoreceptors -> bipolar cells -> ganglion cells

Question 62

What are the cells that connect laterally in the retina?

Answer 62

Horizontal cells | Amacrine cells

Question 63

What do horizontal cells receive input from?

Answer 63

Photoreceptors

Question 64

What do amacrine cells receive input from?

Answer 64

Bipolar cells

Question 65

Do photoreceptors depolarise or hyperpolarise when light is shone on them?

Answer 65

Hyperpolarise

Question 66

What does retinal in rhodopsin convert from and into when it absorbs light?

Answer 66

From 11-cis-retinal to all-trans-retinal

Question 67

What does convergence mean in the retina?

Answer 67

How many photoreceptors transmit to one ganglion cell. | E.g. high convergence in rods as lots of rods converge on one ganglion cell

Question 68

Which of the OFF or ON pathway has ionotropic or metabotropic glutamate receptors in the ganglion cells?

Answer 68

OFF - ionotropic | ON - metabotropic

Question 69

What is the function of amacrine cells?

Answer 69

Lateral inhibition

Question 70

What is the function of horizontal cells?

Answer 70

Lateral inhibition | Releases GABA when excited allowing centre-surround organisation to work.

Question 71

Which of A-delta and C fibres are polymodal?

Answer 71

C-fibres

Question 72

What is the family name for thermoreceptors?

Answer 72

Transient receptor potential (TRP)

Question 73

Which thermoreceptor is greatly sensitised in inflammation to become active at body temperature?

Answer 73

TRPV1

Question 74

Give some examples of chemical stimuli for nociceptors and what receptors are activated by them.

Answer 74

H+ - acid sensing ion channels (ASICs) ATP - P2X and P2Y Bradykinin - B2 receptors

Question 75

What type of nociceptors have both afferent and efferent function?

Answer 75

Peptidergic polymodal nociceptors (subset of C fibres)

Question 76

What is released by the nociceptors which contributes to neurogenic inflammation?

Answer 76

Pro-inflammatory mediators (calcitonin, CGRP, substance P)

Question 77

What is the long term effect of noxious stimulation on the spine?

Answer 77

Increases spinal excitability | Contributes to hyperalgesia and allodynia

Question 78

What types of neurone receive signals from nociceptors and proprioceptors?

Answer 78

Wide dynamic range neurones

Question 79

What is viscerosomatic pain?

Answer 79

Sharp well localised pain when inflammatory exudate from a diseased organ contacts a body wall structure e.g. appendicitis.

Question 80

Describe the gate control theory in terms of nociceptors and proprioceptors.

Answer 80

When proprioceptors are more active than nociceptors, pain is less perceived and vice versa.

Question 81

What tract largely transmits slow C-fibre pain and what is its function?

Answer 81

Spinoreticular tract | Autonomic and emotional response to pain