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Unit 11 > W1: The somatic nervous system > Flashcards

W1: The somatic nervous system Flashcards

1
Q

What are the different structural classifications of the nervous system?

A

The central nervous system - brain and spinal cord
The peripheral nervous system - cranial nerves and spinal nerves

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2
Q

What are the different functional classifications of the nervous system?

A

Sensory v motor
Somatic v autonomic

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3
Q

What makes up the sensory components of the nervous system?

A

Sensory ganglia and nerves
Sensory receptors (at the surface and within the body)

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4
Q

What makes up the different motor components of the nervous system?

A

Visceral motor system - autonomic ganglia and nerves, consists of parasympathetic, sympathetic and enteric division

Somatic motor system - motor nerves

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5
Q

What are the different effectors in the nervous system?

A

The visceral system - smooth muscle, cardiac muscle and glands etc

The somatic system - skeletal/striated muscle

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6
Q

What is the organisation of sensory nerves seen at the individual spinal cord level?

A

Dorsal and ventral rami converge on a spinal nerve, which then splits into dorsal and ventral root.
Dorsal rami carrier primary sensory afferents with cell bodies in the dorsal root ganglion, axon terminals are in the dorsal horn

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7
Q

Describe the organisation of alpha motor neurons in the spinal cord?

A

Cell bodies in the ventral horn, project along the ventral root, into the spinal nerve then out along the dorsal or ventral rami

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8
Q

Describe the location of sympathetic nerves at the spinal cord level.

A

Thoracolumbar output
Cell bodies in the lateral horn
Project out via the ventral root through the spinal nerve.
Travel past the grey rami then travel down the white (myelinated) rami, into the sympathetic chain ganglion where synapse occurs (may then travel up or down the vertebral level through the sympathetic chain ganglion), then travel out the grey rami

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9
Q

Where are interneurons found in the spinal cord?

A

Found throughout.

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10
Q

What are the different classifications of nerves to do with what they supply and where they are travelling?

A

Somatic afferent e.g carry localised pain
Somatic efferent - skeletal muscle activation
Visceral afferent - GI pain
Visceral efferent - GI muscle activation (vomiting)

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11
Q

What is meant by a somatic afferent?

A

Somatosensory afferents within nerves - pain, touch, position, temperature and itch

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12
Q

What is meant by a somatic efferent?

A

Motor axons within nerves

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13
Q

What is meant by a visceral afferent?

A

A viscerosensory afferent within nerves of the viscera and blood vessels

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14
Q

What is meant by a visceral efferent?

A

Smooth and cardiac motor axon within nerves
E.g gland and gut wall innervating

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15
Q

What is the red A broadmand area?

A

Area 6
Premotor area

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16
Q

What is the red B broadmann area?

A

Area 6
Supplementary motor area

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17
Q

What is red C broadmann area?

A

Area 4
Primary motor cortex

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18
Q

What is green A broadmann area?

A

Area 1,2,3
Somatosensory cortex

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19
Q

What is green B broadman area?

A

Visual cortex
17,18,19

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20
Q

What is the green C broadmann area?

A

Auditory cortex
Area 41 and 42

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21
Q

What is the large purple area C?

A

Prefrontal cortex

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22
Q

What is the purple A broadman area?

A

Posterior parietal cortex
Area 5,7

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23
Q

What is the role of the posterior parietal cortex?

A

Spatial representation of objects for planning and motor control.

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24
Q

What is the purple area B broadmann area?

A

The infarotemporal cortex
Area 20,21,37

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25
What is the Boradmann area shown in the smaller brain?
Gustatory cortex Area 43.
26
What is important about the functional design of the primary motor cortex?
Has a topographic map of the body Higher density of cortical neurons proportional to the degree of control in the body.
27
What is the layout of the topographic map in the primary motor cortex (M1)?
28
Describe how neurons supplying the face travel out of the motor cortex?
M1 neurons controlling the face travel along the corticobulbar tract Project out through the genu part of the internal capsule
29
Describe how motor neurons travelling to supply the body leave the motor cortex?
Follow the corticospinal tract Leave M1 (primary motor cortex) by projecting through the posterior limb of the internal capsule
30
Describe the structure of the internal capsule.
Conists of an anterior limb, a genu and a posterior limb. Shaped like a more than/less than sign, eating the lateral side
31
What is the corticospinal tract?
Motor neurons from M1 that supply the axial and limbs, project through the posterior limb of the internal capsule Then to cerebellar peduncles To the medullary pyramids where most of the desecation occurs. (Description of the pyramids) Desiccated: To the lateral funiculus which contains the lateral corticospinal tract in the white matter of the spinal cord Not dedicated: to the anterior corticospinal tract in the white matter of the spinal cord, at the correct vertebral level will desiccate at the anterior white commissure. Then re-enters the spinal cord and synapses in the ventral horn with a lower motor neuron which will travel to the skeletal muscle
32
What is the proportion of fibres in the corticospinal tract that desicate at the destination of the pyramids?
85% desiccate at the desiccation of the pyramids Remaining 15% travel in the anterior corticospinal tract and will desciate in the anterior white comissure
33
What is the pattern of the corticobulbar tract?
Originates from M1 for supply of the face Projects through the genu of the internal capsule Synapses with the cranial motor nuclei found within the midbrain, pons and medulla
34
What is the pattern of synapsis for the Upper Motor Neurons in the corticobulbar tract with the cranial motor nuclei?
CN3,4,5,6 - bilateral CN7 splits into upper and lower - upper is bilateral and lower is contralateral Nucleus ambiguous - CN9,10,11 (cranial accessory) - bilateral CN11 (spinal accessory) - bilateral CN12 - contralateral only.
35
How does the corticobulbar tract underpin the difference between how a stroke and bells palsy present?
Stoke - upper motor neuron lesion Bells - lower motor neuron lesion Upper face - bilateral synpasis from the corticobulbar tract Lower face - contralateral synapsis Therefore in an upper motor neuron lesion, the upper face would recover (as can still be supplied by opposite side of brain) but the lower side of the face would remain damage. However in a lower motor neuron lesion neither part of the face would recover
36
Define what is meant by a lower motor nueron
A neuron that directly innervates muscle
37
What nuclei in the brainstem give rise to lower sensory neurons?
The trigeminal sensory nucleus The vestibular and cochlear nuclei Nucleus solitarus
38
What nuclei in the brain stem gives rise to lower motor neurons?
Edinger-Westphal nucleus Oculomotor nucleus Trochlear nucleus Trigeminal motor nucleus Abducens nucleus Facial motor nucleus Superior and inferior salivatory nuclei Nucleus ambiguous Dorsal motor nucleus of the vagus Hypoglossal nucleus
39
Define what is meant by an upper motor neuron
Control lower motor neurons
40
What is an example of an upper motor neuron?
Layer 5 Betz neurons - whose axon form the corticospinal and corticobulbar tract.
41
What do proprioceptive afferents do?
Sense muscle tension
42
What are the different type of muscle fibres?
Extrafusal muscle fibres - cause muscle tension/contraction Intrafusal muscle fibres - sense tension in the muscle
43
What afferents innervates the intrafusal muscle fibres?
Type 1a and type 2 afferents
44
What structures play a role in proprioception of skeletal muscle?
Intrafusal muscle fibres - innervates by type 1a and type 2 afferents Golgi tendon organs - innervated by type 1b proprioceptors
45
What is a Golgi tendon organ?
Role is proprioception Loacted within the collagen fibres of tendons and within joint capsules Recieves information from a muscle tendon about tension
46
What is the response in a skeletal muscle during passive muscle stretching? In relation to proprioception
GTOs are under tension due to stretch Intrafusal muscle fibres are under tension Therefore, type 1a and type 2 (IMF) and type 1b (gto) afferents will show activity
47
What is the response in the skeletal muscle during active muscle contraction in relation to active muscle contraction?
GTO is under tension (think as pulled by muscle) Intrafusal fibres relax in length as the muscle shortens around them Therefore - activity in the T1a and Type 2 afferents is none existent and activity from Type 1b afferents is high
48
What is an intrafusal muscle fibre?
Located deep within the muscle Sense muscle tension to contribute to proprioception Have a swelling in the middle called a nuclear bag fibre Are innervated by type 1a and 2 afferents (proprioception) and gamma motor nuerons to contract them
49
What are the different types of motor neurons found in skeletal muscle?
𝞪 motor neurons - innervate extrafusal fibres - generate contractile force 𝞬 motor neurons - innervate intrafusal muscle fibres - stimulate to contract to maintain sensitivity of proprioception
50
How does proprioception adapt to different levels of muscle contraction?
Gamma motor neurons - innervate intrafusal fibres - cause to contract - this shortens the fibre hence increases tension again - leads to higher sensitivity of proprioception. THis is all relative to the level of alpha motor neuron activity
51
What is meant by a gain of proprioception?
Increase in the sensitivity of proprioception Done by increasing y motor nueroon contraction relative to alpha motor neuron contraction - allows the intrafusal muscle fibre to shorten and increase tension alongside a shortening muscle This is controlled by lower subconscious circuits and upper conscious circuits.
52
What is the role of inhibitory interneurons in the spinal cord?
Are GABAergic neurons - inhibit motor neurons - hence prevent contraction Are considered upper motor neurons
53
What is the consequence of a damaged inhibitory interneuron?
Type of upper motor neuron Results in spasticity or clonus of the joint
54
What is the function of the reticulospinal tract?**
Responsible for subconscious motor control e.g posture and breathing Role in preparatory and movement-related activities. Co-ordination of motor signals. Role in spinal reflex arcs Unconscious proprioception
55
What makes up the reticulospinal tract?
Pontine reticular formation orignates in the pontine tegmentum, travel through the medullar and into the spinal cord through the reticulospinal tract to synapse. The medullary reticular formation originates in the gigantocellularis, will also travel in the reticulospinal tract to spinal in the spinal cord. Fibres can be found scattered in throughout the ventral and lateral columns of the spinal cord.
56
What does additional reading suggest is the function of the reticulospinal tract?
Pontine reticulospinal fibres - extensor muscles Medullary reticulospinal tract flexor muscles Normally act in a balanced coordinated fashion to control muscle tone. Act on both alpha and gamma motor nuerons.
57
What is meant by a vestibular sensation?
A sense of balance/head position Helps maintain equilibrium , posture, head position and clear vision with movement.
58
What are the different vestibular reflexes?
Vestibulospinal reflex Vestibulocollic reflex Vestibulo-ocular reflex
59
What is the role of the vestibulospinal reflex?
Sense head movement Stops falling over by innervating the spinal cord LMNs, often cause extension of upper limbs and flexion of lower limbs to protect from impact of fall. Controls body balance
60
What is the role of the vestibulocollic reflex?
Keeps your head up by innervating cervical lower motor neurons Stabilises the position of the head.
61
What is the role of the vestibular-ocular reflex?
Keeps your gaze fixed by innervating cranial nuclei of 3,4,6 - the extra-ocular nerves.
62
What is the link between all the different vestibular reflexes?
The vestibular nuclei A bilateral structure found in the floor of the fourth ventricle in the medulla. Upper motor nuerons will synpase in the ventral horn with lower motor neurons
63
What is meant by tectum in neuroanatomy?
The roof - e.g the cerebral aqueduct between the 3rd and 4th ventricles Tectum = the superior colliculus and the inferior colliculus (found in midbrain)
64
What is the role of the superior and inferior colliculus?
Superior colliculus - responsible for visual reflexes Inferior colliculus - auditory refelxes
65
What is the tectospinal tract?
Originates in the superior colliculus/inferior colliculus of the midbrain Desicates in the dorsal tegmental decussation, ventral to the periaqueductal grey matter. Descends in the medial part of the ventral funiculus of the spinal cord Synapse in the ventral horn, typically with upper cervical cord motor neurons
66
What is the role of the tectospinal/tectobulbar tract?
Reflex orientation of the head and neck motor movements in response to visual and auditory stimuli Tectospinal responsible fir head and back movements terminates in spinal cord Tectobulbar responsible for movement of eyes and head - terminates in brain stem
67
What is the function of the corticospinal tract?
Control primary motor activity to the somatic system aka voluntary control of skeletal muscle From the neck downwards - innervates lower motor neurons that are spinal nerves.
68
What is the function of the corticobulbar tract?
Provides motor innervation input to cranial nerve nuclei
69
What is the function of the spinothalamic tract?
Responsible for pain Responsible for temperature Responsible for crude touch Responsible for conscious proprioception
70
What is the function of the dorsal column medial lemniscus pathway?
responsible for light touch and vibration
71
What are the different tracts responsible for proprioception?
Conscious - DCML - from the periphery to Primary sensory cortex. Unconscious proprioception - the reticulospinal tract.

Unit 11 (21 decks)

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