Somatic Motor Control Flashcards
(54 cards)
1
Q
What is the motor division?
A
- the output division of the peripheral nervous system
- it controls muscles & glandular activity
2
Q
What is the motor division divided into?
A
- the somatic nervous system
- the autonomic nervous system
3
Q
What does the somatic nervous system do?
A
- innervates skeletal muscle
- somatic nerves control body movements
4
Q
What does the autonomic nervous system do?
A
- innervates blood vessels & viscera
- which are made of smooth muscle
- and the heart, which is made of = cardiac muscle
- controls unconscious / involuntary muscle activity
- controls glandular secretion
5
Q
A - the autonomic pathway summary:
A
- sensory neuron
- dorsal root ganglion
- interneurons in the spinal cord
- preganglionic fiber
- autonomic ganglion
- postganglionic fiber
- visceral
- blood vessel is effected
6
Q
B - the somatic pathway summary:
A
- skin
- sensory neurone
- dorsal root ganglion
- interneurons in the spinal cord
- somatic motor neuron
- skeletal muscle is effected
7
Q
What are the two areas of the frontal lobe are involved in initiating & creating muscle movements?
A
- motor association (premotor) area
- primary motor area (precentral gyrus)
8
Q
What does the motor association (premotor) area do?
A
- generates a plan for the degree & sequence of muscle contraction
- relays this information to the primary motor area
9
Q
What does the primary motor area (precentral gyrus) do?
A
- the program is sent along the relevant pathway, to eventually reach the appropriate muscles
10
Q
Is the amount of cortex in the primary motor area for a given body region proportional to the size of the region itself?
A
- NO
- it is proportional to the number of muscles and motor units in that region
11
Q
What is the motor homunculus for?
A
- each body part is allocated an area of cortex in the primary motor area
12
Q
What do areas that require fine motor control have?
A
- example = hand
- have a higher number of individual muscles
- these muscles express a higher number of motor units than muscles elsewhere
13
Q
The greater the degree of control over muscle activity required to carry out movements of a given body part…..the……
A
- larger the area of the cortex devoted to that specific control
14
Q
What do some neurones from the primary motor cortex do?
A
- synapse with neurones of the spinal cord, to stimulate movement
15
Q
What is the pathway motor neurones take to reach skeletal muscle?
A
- corticospinal tract
16
Q
Where do most fibres cross the medulla oblongata?
A
- 80%
- cross the medulla oblongata on their way to the spinal cord
17
Q
Where do the remaining 20% of fibres cross?
A
- the level of innervated muscle
18
Q
What do the motor areas of the left side of the brain control?
A
- skeletal muscle of the right side of the body
19
Q
What do motor areas of the right side of the brain control?
A
- skeletal muscle on the left side of the body
20
Q
What do the corticospinal tracts do?
A
- innervates distal muscles of the body
- the muscles that mediate voluntary skeletal muscle activity
21
Q
What do other neurons in the primary motor cortex do?
A
- synapse with neurones in lower brain areas
- in the cerebellum and basal ganglia
- allowing these areas to help with the control of movement
22
Q
What are the two other descending tracts involved in motor control?
A
- the reticulospinal tract
- the vestibulospinal tract
- neither of these tracts cross
23
Q
What are those two last tracts important for?
A
- balance and posture
- they innervates proximal muscles = the muscles closest to the trunk
- vestibulospinal specifically involved with = control of the position of the head
24
Q
Why is regulating balance and posture important?
A
- creates a stable background for voluntary body movement
25
Where is the cerebellum located?
- just above the brainstem
- beneath the occipital lobes at the base of the skull
26
What does the cerebellum do?
- receives signals from the primary motor cortex about intended movements
- receives signals from sensory receptors in skeletal muscle = proprioreceptors
- from the ear = about actual movements occuring
- smooths movements, important in balance & posture
27
What is the first function of the basal ganglia?
- related to voluntary movement
- has a role in initiating movements
28
What do individuals suffering from lesions of the basal ganglia show?
- akinesia
- bradykinesia
- the basal ganglia exhibits electrical activity before movement takes place
29
What is the second function of the basal ganglia?
- related to resting muscle tone
- The basal ganglia help maintain and regulate resting muscle tone by modulating signals from the motor cortex to the muscles. They do this by balancing excitatory and inhibitory inputs to prevent excessive muscle activity or rigidity.
30
What does ischemic damage to the basal ganglia during a stroke cause?
- spastic paralysis
31
What do Parkinson’s patients exhibit at rest?
- rigidity
- tremor
32
What are the two types of proprioceptor important in detecting mechanic stimuli?
- muscle spindles
- Golgi tendon organs
33
What are the function of mechanoreceptors?
- enable movement to be charted & modified
- helps posture
- protection
34
What is the structure of muscle spindles?
- consists of a number of highly specialised muscle fibres within a collagenous capsule
35
What are the muscle fibres known as?
- intrafusal fibres
- central portion that has NO actin or myosin
36
As the central portion cannot contract, what does this mean?
- it is able to act as a sensory receptors
37
Why can intrafusal fibres detects changes in muscle length?
- because they run in parallel with the normal contractile fibres
38
When the muscle is stretched…the spindles….
- are also stretched
39
What is activation of muscle spindles important for?
- proprioreception
- activates the reflex arc
40
Reflex arc:
- muscle spindle
- sensory nerve
- motor nerve
- stretch reflex
41
Describe what happens in the reflex arc?
- activation of motor neurones via the spinal cord
- to the stretched muscle
- so that the muscle contracts more forcefully
42
What is the response from the reflex arc called?
- the stretch reflex
- helps maintain posture
43
Example of the stretch reflex:
- head tips forward
- stretches muscles at the back of the neck
- stimulating the muscle spindles
- they relay signals to the spinal cord
- motor nerves are activated, innervating those muscles
- they contract more forecefully
- raising your head
44
What are Golgi tendon organs?
- mechanoreceptors
- nerve endings which innervate tendons and detect differences in muscle tension, not length
45
What are the two conditions by which golgi tendons discharge impulses?
- in response to excessive tension created in the muscle when it shortens itself
- in response to excessive tension created in the muscle when it is passively stretched
46
What do the Golgi tendons do?
- sends signals to the cerebellum
- bring about reflex inhibition of muscles that they supply
- this protects the muscles from being overstretched
47
Reflex inhibition via Golgi tendon organ summary:
- they are present in muscle
- sensor nerve from tendon organ
- spinal cord
- inhibitory interneurons
- alpha motor neurone
- stops muscle overstretching
48
What are the tracts carrying signals from proprioreceptors to the cerebellum called?
- posterior and anterior spinocerebellar tracts
49
What do these tracts allow?
- let the cerebellum to gather information about the degree of stretch in the muscle,
- the tension generated by individual muscles,
- the relative positions of the parts of the body at any time
= unconscious proprioception
50
51
What is the posterior column?
- made of two tracts
- they cross in the medulla oblongata
- gracile fasciculus
- cuneate fasciculus
52
What does the gracile fasciculus do?
- carries sensations of limb & trunk position and movement from vertebrae T6 & below,
- from the middle of the chest and lower parts of the body
53
What does the cuneate fasciculus do?
- carries these sensations from above T6,
- from the chest and upper limbs
54
Where do signals from these two tracts reach and what does it do?
- reach the somatosensory cortex at the parietal lobe
- gives us conscious awareness of body position & movement
= conscious proprioception
