Spinal Control of Movement Flashcards
1
Q
- What did Sherrington call the “final common pathway,” and why?
A
- Upper motor neurons= from brain which bring info to spinal cord
- Lower motor neurons = somatic motor neurons in VENTRAL horn of the spine which tell muscle to finally contract (this is the final common pathway)
2
Q
- Define, in one sentence, motor unit. How does it differ from motor neuron pool?
A
- Motor unit= 1 alpha motor neuron + muscle fiber being innervated
- Motor neuron pool= collection of many alpha motor neurons that innervate a single muscle
3
Q
- When and why does rigor mortis occur?
A
- No ATP = myosin stay binded to actin filaments = no exposure site for binding and contraction
4
Q
- Your doctor taps the tendon beneath your kneecap and your leg extends. What is the neural basis of this reflex? What is it called?
A
- Knee jerk reflex= when tap, tendon stretches quads for a bit then, contracts causing leg to extend.
5
Q
- What is the function of gamma motor neurons?
A
Alpha neurons
Gamma motor neurons
Innervates extrafusal muscle fibres= contraction
Innervate intrafusal/ muscle spindles
- Keep spindles in line during contraction by causing poles of spindles to contraxct
6
Q
- Lenny, a character in Steinbeck’s classic book Of Mice and Men, loved rabbits, but when he hugged them, they were crushed to death. Which type of proprioceptive input might Lenny have been lacking?
A
- Ia neuron (from muscle spindle) detect info on muscle length
- Ib neuron from golgi tendon organ detect info on muscle tension
- Lenny probably didn’t input from Ib neurons and thus couldn’t feel how hard he was actually hugging, thus killing the rabbit.
7
Q
- What is the difference between upper and lower motor neurons?
A
- Upper motor neurons= in brain
- Lower motor neurons = in spinal cord ventral horn which sends info to 3 different areas of body
- axial muscles
- proximal muscles- shoulders, elbows, pelvis and knee
- distal: fingers, hands, feet and toes
8
Q
- What diseases can occur when motor neurons are damaged?
A
- ALS/ Lou Gehrig’s disease: weak muscle due to degeneration of CNS neurons-> gradual loss of movement -> paralysis
- Progressive muscular atrophy
- Spinal muscular atrophy
9
Q
- How are lower motor neurons distributed in the spinal cord
A
- Located in the ventral horn
- Distributed based depending on muscle type
- Axial muscles are more medial so that means in the ventral horn, motor neurons will be more medial compared to neurons which supply distal muscles
- Flexors are more posterior and medial compared to extensors.
10
Q
- What are the types of lower motor neurons?
A
Alpha neurons
Gamma motor neurons
Innervates extrafusal muscle fibres= contraction
Innervate intrafusal/ muscle spindles
- Keep spindles in line during contraction by causing poles of spindles to contraxct
11
Q
- What is the difference between a slow and fast motor unit?
A
Slow (Red)
Fast (pale white)
- More mitochondria
- Antigravity leg muscles
- Slow fatigue
- Sustained contraction
- Anerobic respiration (less mitochondria)
- Fast contraction = quick fatigue
- Jumping muscles
12
Q
- What is neuromuscular matchmaking?
A
- When you take a lower motor neuron which normally is responsible for innervating slow muscles and use it to innervate a fast muscle=> the fast muscle will become ‘slow’
13
Q
- Describe the molecular process of muscle contraction
A
- Ca2+ stored in sarcoplasmic reticulum released + bind with troponin
- Myosin (thick) + link with actin (thin)
- Myson pivots head = slide
14
Q
- Describe important structures of a myofibril:
A
- Z discs= divides muscle fiber in segments
- Thin filaments= actin
- Thick = myosin
15
Q
- What is the role of muscle spindles and how are they oriented in muscle fibers?
A
- They are small sensory units which can detect change in length of muscles and tell the spinal cord via 1a sensory axons that mucle has stretched
- Positioned in parallel (in line) with fibres (makes sense bc it wants to know length)
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