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BAMS > Locomotion > Flashcards

Locomotion Flashcards

1
Q

How do we convert a stimulus into an electrical action potential?

A

Via specific sensory receptors

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2
Q

What are the 4 properties of a stimulus?

A

Quality (type of receptor)
Intensity (AP frequency, number neurons activated)
Duration (duration of AP)
Location (where?)

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3
Q

What is the definition of a neurons receptive field?

A

Each neuron has a cluster of peripheral nerve branches, each with a nerve ending (Receptor)

The distribution of these receptors defines a neuron’s receptive field

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4
Q

Where are receptive fields the largest?

A

Large on the trunk

Small in the periphery

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5
Q

What is two point discrimination?

A

The ability to discern two separate mechanical stimuli

Areas with small 2-point discrimination = Areas with small receptive fields

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6
Q

How is an action potential produced?

A 
Stimulus
Change in receptor membrane permeability
Influx of cations 
Depolarisation: Receptor potential 
Action potential
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7
Q

What is meant by intensity in sensory coding?

A

All action potential same

  • Frequency of AP discharge
  • Increase in stimulus intensity thus means increase in AP frequency
  • Different receptors have different thresholds

Also means numbers of neurons activated

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8
Q

What is meant by a neural pathway?

A

Neural pathway is a connection formed by axons that project from neurons to make synapses onto neurons in another location, to enable a signal to be sent from one region of the nervous system to another.

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9
Q

What is a ganglion?

A

A group of nerve cell bodies located in the ANS or sensory nervous system.

They house the cell bodies of afferent or efferent nerves.

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10
Q

What are examples of cutaneous/subcutaneous mechanoreceptors and what type of axons are they?

A
  • Meissner’s corpuscle
  • Merkel disk
  • Hair follicle receptors
  • Pacinian corpuscle
  • Ruffini’s ending

A-beta afferents

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11
Q

What is the brachial plexus?

A

Innervates the upper limb

Consists of the nerves

  • Axillary
  • Musculocutaneous
  • Radial
  • Ulnar
  • Median
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12
Q

What is epineurium?

A

It is the outermost layer of dense irregular connective tissue surrounding a peripheral nerve

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13
Q

What are fascicles?

A

A small bundle of nerve fibres enclosed by the perineurium

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14
Q

What is the perineurium?

A

A protective sheath covering nerve fascicles

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15
Q

What are the features of A(ɑ) nerve fibres?

A
  • Largest - diameter of 13-20 micrometres
  • Fastest - conduction speed - 80-120m/sec
  • Proprioreceptors (limb position) of skeletal muscle
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16
Q

What are the features of A(β) nerve fibres?

A
  • Second largest - diameter of 6-12 micrometres
  • Second fastest - 35-75m/sec
  • Mechanoreceptors of skin
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17
Q

What are the features of A(δ) nerve fibres?

A
  • Third largest - 1-5 micrometres
  • Third fastest - 5-30m/sec
  • Pain/Temperature
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18
Q

What are the features of C nerve fibres?

A
  • Smallest - unmyelinated - 0.2-1.5 micrometres
  • Slowest - 0.5-2 m/sec
  • Temperature/pain/itch
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19
Q

What are dorsal and ventral roots?

A

Sensory axons enter CNS via dorsal roots

Cell bodies of sensory axons are located in the dorsal root ganglia (DRG)

Motor axons exit CND via ventral roots

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20
Q

What are the three neurons of a typical sensory pathway?

A

1st neuron - Primary sensory neuron - Periphery
2nd neuron - Secondary sensory neuron - CNS
3rd neuron - Tertiary sensory neuron - Thalamus

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21
Q

What is the primary neuron in the somatosensory pathway?

A

In the periphery, primary neuron is the sensory receptor that detects stimuli.

Cell body of primary neuron is located in the DRG of a spinal nerve, or, if sensation in head/neck the ganglia of the trigeminal or cranial nerves (trigeminothalamic tract)

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22
Q

What is the secondary neuron in the somatosensory pathway?

A

Secondary neuron acts as a relay and is located in either the spinal cord or the brainstem. This neurons axons will decussate to the opposite side of the spinal cord or brainstem and travel up the spinal cord to the brain.

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23
Q

What is the tertiary neuron in the somatosensory pathway?

A

Tertiary neurons have cell bodies in the thalamus and project to the postcentral gyrus of the parietal lobe, forming a sensory homunculus in the case of touch.

Regarding posture, the tertiary neuron is located in the cerebellum.

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24
Q

What is stereognosis?

A

The ability to recognise objects by ‘the feel’ alone

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25
Q

How can pain be classified?

A
  • Nociceptive pain

- Clinical pain - acute or chronic

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26
Q

What fibres mediate nociceptive pain?

A

A-delta (noxious mechanical/heat) and C fibres (polymodal)

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27
Q

What is nociceptive pain?

A

Only elicited when intense/noxious stimuli threaten to damage normal tissue - protective function

Characterised by a high threshold and limited duration

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28
Q

What is acute clinical pain?

A

Results from soft tissue injury or inflammation - protective

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29
Q

What is chronic clinical pain?

A

Sustained sensory abnormality - e.g. chronic inflammation
Pain is maladaptive, offering no survival advantage
Resistant to treatment

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30
Q

What are 5 diagnostic features in pain?

A 
Location
Pain quality
Pain intensity
Frequency/duration
Provoking/relieving events
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31
Q

What is referred pain?

A

Pain felt in one part of body but pathology is elsewhere.

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32
Q

Where are the nociceptive afferents in the tooth? and how does this sensory pathway work differently to if it was not head/neck?

A

Free nerve fibre endings extend into the dentine

Trigeminothalamic tract - Cell body of primary neuron in trigeminal ganglion as opposed to DRG

33
Q

What is the CNS relay cell and pathway for pain not in head/neck?

A

Spinal dorsal horn

Spinothalamic tract

34
Q

CNS relay cell and pathway for pain in head/neck?

A

Spinal trigeminal nucleus

Anterior trigeminothalamic tract

35
Q

What factors affect pain perception?

A 
Genetic
Molecular
Cellular
Anatomical
Physiological
Psychological
Social
36
Q

What mutation causes pathology of pain sensation?

A

SCN9A-mutation = loss of Nav 1.7 function which is strongly expressed in nociceptive afferents as it encodes alpha subunit of the sodium channel

37
Q

What is the gate control theory of pain?

A

This theory asserts that non-painful input closes the nerve ‘gates’ to painful input, which prevents pain sensation from travelling to the CNS.

Nonnociceptive fibres - A-beta fibres inhibit the effects of firing by Aδ and C fibres.

38
Q

What is triple response?

A
  • Red reaction
  • Flare
  • Wheal
39
Q

What type of movement are reflexes?

A

Involuntary actions

40
Q

What part of the CNS are reflexes centred on?

A

Motor neuron cell bodies found in:

  • Spinal cord (somatic)
  • Brainstem (cranial nerves)
41
Q

What are common final pathways?

A

Motor neurons by which nerve impulses from many central sources pass to a muscle or gland in the periphery

42
Q

Where do dorsal roots enter the spinal cord?

A

Posterolateral sulcus

43
Q

Where do ventral roots leave the spinal cord?

A

Anterolateral sulcus

44
Q

What are the regions of grey matter?

A

Grey matter is the region of cell bodies of neurons

  • Intermediate horn
  • Dorsal horn
  • Ventral horn
45
Q

What is white matter in spinal cord?

A

Axons

46
Q

In basic terms, how does the reflex pathway occur?

A 
Stimulus
Receptor
Afferent (sensory) neuron
Synapse (s)
Efferent (motor) neuron
Effector (muscle, gland)
Response
47
Q

What are examples of somatic reflexes?

A
  • Tendon-jerk reflexes

- Cutaneous reflexes

48
Q

What are the receptors for tendon-jerk reflexes?

A

Proprioreceptor endings
Group 1a muscle afferents
Homonymous motor neurons

49
Q

What are the receptors for cutaneous reflexes?

A

Mechanoreceptor endings

Nociceptor endings

50
Q

What are other somatic reflex receptors?

A

Chemoreceptors

Photoreceptors

51
Q

What is the ankle-jerk reflex?

A

Hammer tap to achilles’ tendon
Stretches spindles within gastrocnemius
APs conducted along 1a muscle afferents to spinal cord
Monosynaptic activation of motor neurons of gastrocnemius muscle
Axon potentials travel along A-alpha motor axon
Gastrocnemius muscle contracts
Foot extends

52
Q

Apart from ankle-jerk, what are other commonly tested reflex reactions?

A
  • Bicep Jerk
  • Tricep Jerk
  • Rectus Abdominis Reflex
53
Q

What is the jaw-jerk reflex?

A

Hammer tap to chin
Stretches spindles of jaw elevator muscles
APs conducted along 1a muscle afferents to brainstem
Monosynaptic activation of motor neurons of jaw elevator muscle
APs travel along A-alpha motor axon
Jaw elevator muscles contract
Jaw jerks upwards, mouth closes

54
Q

How are somatic reflexes used as protection mechanisms?

A
  • Escape mechanism
  • Prevention of muscle overloading
  • Prevention of inadvertent foreign body ingestion
  • Digestive aid
55
Q

How does somatic reflex prevent overloading of muscle?

A

Receptor activated by stretch and contraction
Afferent signals cause INHIBITION of motor neuron activation
Inverse of stretch reflex (myotatic reflex)
Prevents overloading of muscle

56
Q

How does muscle loading in jaw muscles work?

A

No golgi tendon organs (proprioreceptors that detect change in muscle tension)
Bite force controlled by increased loading of periodontal ligament
Afferents inhibit jaw elevator muscle motor neurons
Anaesthesia of molars increases maximum bite force

57
Q

How does the pharyngeal reflex (gag reflex) work?

A
  • Mass contraction of both sides of the posterior oral and pharyngeal musculature
  • Activation: mechanoreceptor afferent from the posterior part of the tongue/soft palate
  • Stimulation of sensory fibres from the glossopharyngeal nerve (IX)
  • Afferents terminate in the caudal part of the spinal trigeminus nucleus (SpVn)
  • Interneurons project from SpVn to nucleus ambiguus (X motor nucleus)
  • X afferents terminate innervate muscles
58
Q

What are semi-automated actions?

A

Voluntary, but you dont have to think about them
e.g. walking, breathing, chewing

May be driven by central pattern generators

59
Q

What are the areas within white matter?

A
  • Dorsal funiculus
  • Lateral funiculus
  • Ventral funiculus
60
Q

What allows the two hemispheres of the brain to communicate?

A

corpus callosum

61
Q

In what lobe does the somatic motor cortex exist?

A

Frontal

62
Q

In what lobe does the somatic sensory cortex exist?

A

Parietal

63
Q

What type of motor neurons are found in spinal cord?

A

Spinal motor neurons

64
Q

What type of motor neurons are found in the brainstem?

A

Cranial motor neurons

65
Q

What is the corticobulbar tract?

A

Pathway connecting the motor cortex to the medullary pyramids in the brainstem’s medulla oblongata

Involved in carrying the motor function on non oculomotor cranial nerve

66
Q

What are the two motor descending pathways?

A

Corticospinal

Corticobulbar

67
Q

What is anaesthesia and paraesthesia?

A

anaesthesia - loss of sensation

Paraesthesia - altered sensations

68
Q

What is palsy?

A

Lesions to motor pathways cause paralysis

69
Q

How can paralysis occur in lower motor neurons?

A

Lesions in final common pathway

70
Q

How can paralysis occur in upper motor neurons?

A

Lesions in either

  • Corticospinal tract
  • Corticobulbar tract
71
Q

What is the basal ganglia?

A

Theyre comprised of several sub-cortical nuclei that link to cerebral cortex via feedback loops

They influence/regulate output from the motor cortex
Act to initiate actions and to switch from one action to another

72
Q

What is the corpus striatum divided into?

A

Lentiform nucleus (globus pallidus and putamen)

Caudate nucleus

73
Q

What are the different action selection centres?

And what pathology does damage to these areas cause?

A
  • Corpus striatum
  • Sub-thalamic nuclei
  • Substantia nigra

Parkinsons/Huntingtons

74
Q

What is Parkinsons disorder?

A

Hypokinetic disorder

Dopamine deficiency in substantia nigra

75
Q

What is Huntingtons disorder?

A

Hyperkinetic disorder

Imbalance of neurotransmitters

76
Q

What are the two components of the cerebellum?

A

Vermis

Lateral hemisphere

77
Q

What is the function of the cerebellum?

A

Important in co-ordinating movements
Regulates actions of antagonistic muscle groups
Important in maintaining balance
Acts to compare actual performance with what is intended

78
Q

How can cerebellar disorders be characterised?

A 
Loss of co-ordination 
Unsteady gait
Imprecise actions
Inability to co-ordinate alternating contractions of antagonistic muscles 
Intention tremor
79
Q

What are correcting actions?

A

They help keep the position of the head in line with the body’s centre of gravity

BAMS (14 decks)

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