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Locomotion Flashcards

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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
How can pain be classified?
- Nociceptive pain | - Clinical pain - acute or chronic
26
What fibres mediate nociceptive pain?
A-delta (noxious mechanical/heat) and C fibres (polymodal)
27
What is nociceptive pain?
Only elicited when intense/noxious stimuli threaten to damage normal tissue - protective function Characterised by a high threshold and limited duration
28
What is acute clinical pain?
Results from soft tissue injury or inflammation - protective
29
What is chronic clinical pain?
Sustained sensory abnormality - e.g. chronic inflammation Pain is maladaptive, offering no survival advantage Resistant to treatment
30
What are 5 diagnostic features in pain?
``` Location Pain quality Pain intensity Frequency/duration Provoking/relieving events ```
31
What is referred pain?
Pain felt in one part of body but pathology is elsewhere.
32
Where are the nociceptive afferents in the tooth? and how does this sensory pathway work differently to if it was not head/neck?
Free nerve fibre endings extend into the dentine Trigeminothalamic tract - Cell body of primary neuron in trigeminal ganglion as opposed to DRG
33
What is the CNS relay cell and pathway for pain not in head/neck?
Spinal dorsal horn | Spinothalamic tract
34
CNS relay cell and pathway for pain in head/neck?
Spinal trigeminal nucleus | Anterior trigeminothalamic tract
35
What factors affect pain perception?
``` Genetic Molecular Cellular Anatomical Physiological Psychological Social ```
36
What mutation causes pathology of pain sensation?
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
What is the gate control theory of pain?
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
What is triple response?
- Red reaction - Flare - Wheal
39
What type of movement are reflexes?
Involuntary actions
40
What part of the CNS are reflexes centred on?
Motor neuron cell bodies found in: - Spinal cord (somatic) - Brainstem (cranial nerves)
41
What are common final pathways?
Motor neurons by which nerve impulses from many central sources pass to a muscle or gland in the periphery
42
Where do dorsal roots enter the spinal cord?
Posterolateral sulcus
43
Where do ventral roots leave the spinal cord?
Anterolateral sulcus
44
What are the regions of grey matter?
Grey matter is the region of cell bodies of neurons - Intermediate horn - Dorsal horn - Ventral horn
45
What is white matter in spinal cord?
Axons
46
In basic terms, how does the reflex pathway occur?
``` Stimulus Receptor Afferent (sensory) neuron Synapse (s) Efferent (motor) neuron Effector (muscle, gland) Response ```
47
What are examples of somatic reflexes?
- Tendon-jerk reflexes | - Cutaneous reflexes
48
What are the receptors for tendon-jerk reflexes?
Proprioreceptor endings Group 1a muscle afferents Homonymous motor neurons
49
What are the receptors for cutaneous reflexes?
Mechanoreceptor endings | Nociceptor endings
50
What are other somatic reflex receptors?
Chemoreceptors | Photoreceptors
51
What is the ankle-jerk reflex?
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
Apart from ankle-jerk, what are other commonly tested reflex reactions?
- Bicep Jerk - Tricep Jerk - Rectus Abdominis Reflex
53
What is the jaw-jerk reflex?
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
How are somatic reflexes used as protection mechanisms?
- Escape mechanism - Prevention of muscle overloading - Prevention of inadvertent foreign body ingestion - Digestive aid
55
How does somatic reflex prevent overloading of muscle?
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
How does muscle loading in jaw muscles work?
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
How does the pharyngeal reflex (gag reflex) work?
- 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
What are semi-automated actions?
Voluntary, but you dont have to think about them e.g. walking, breathing, chewing May be driven by central pattern generators
59
What are the areas within white matter?
- Dorsal funiculus - Lateral funiculus - Ventral funiculus
60
What allows the two hemispheres of the brain to communicate?
corpus callosum
61
In what lobe does the somatic motor cortex exist?
Frontal
62
In what lobe does the somatic sensory cortex exist?
Parietal
63
What type of motor neurons are found in spinal cord?
Spinal motor neurons
64
What type of motor neurons are found in the brainstem?
Cranial motor neurons
65
What is the corticobulbar tract?
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
What are the two motor descending pathways?
Corticospinal | Corticobulbar
67
What is anaesthesia and paraesthesia?
anaesthesia - loss of sensation | Paraesthesia - altered sensations
68
What is palsy?
Lesions to motor pathways cause paralysis
69
How can paralysis occur in lower motor neurons?
Lesions in final common pathway
70
How can paralysis occur in upper motor neurons?
Lesions in either - Corticospinal tract - Corticobulbar tract
71
What is the basal ganglia?
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
What is the corpus striatum divided into?
Lentiform nucleus (globus pallidus and putamen) Caudate nucleus
73
What are the different action selection centres? | And what pathology does damage to these areas cause?
- Corpus striatum - Sub-thalamic nuclei - Substantia nigra Parkinsons/Huntingtons
74
What is Parkinsons disorder?
Hypokinetic disorder | Dopamine deficiency in substantia nigra
75
What is Huntingtons disorder?
Hyperkinetic disorder | Imbalance of neurotransmitters
76
What are the two components of the cerebellum?
Vermis | Lateral hemisphere
77
What is the function of the cerebellum?
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
How can cerebellar disorders be characterised?
``` Loss of co-ordination Unsteady gait Imprecise actions Inability to co-ordinate alternating contractions of antagonistic muscles Intention tremor ```
79
What are correcting actions?
They help keep the position of the head in line with the body's centre of gravity

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