L5 - Intro to Motor Control

Question 1

Why do we study motor control?

Answer 1

Because the purpose of the nervous system (inc brain) is to create movement

Question 2

What are the 3 kinds of muscle cells/fibres?

Answer 2

• Skeletal (striated)
• Cardiac - heart
• Smooth - gut and lungs

Question 3

Describe skeletal muscle

Answer 3

• striated
• responsible for all skeletal muscle movement
• approx 700 muscles, some attached to tendons and other muscles
• there are antagonist muscles (extensors) which extend the muscle back out again
  and agonist muscles (flexors) which bring it in
• muscles only make one movement - contract.

Question 4

Describe muscle contraction

Answer 4

isotonic - tone stays constant, muscle shortens
isometric - tone changes, length unchanged

sliding filament theory - how contractions happen

Question 5

Describe skeletal muscle anatomy

Answer 5

• many muscle fibres in each muscle
• each muscle fibre is innervated by 1 axon, but 1 axon can innervate many fibres - varies depending on function

fibre types: fast twitch (ANAEROBIC) and slow twitch (AEROBIC)

Question 6

Which type of fibre can be used for longer periods of time?

Answer 6

Slow twitch, although it is not as strong, it uses oxygen as it works so it lasts longer.

Question 7

Describe Muscle fibre structure.

Answer 7

T tubule - membrane folded in that goes deep into the cell
Myofibril - fibres, has stripes and gives striped appearance
Sarcoplasmic Reticulum - modified version of ER, full of calcium and is critical for contraction.

Question 8

Describe the process of muscle contraction

Answer 8

1. Ach released into junction and binds to receptors
2. Na+ channels open and rushes into the muscle, and depolarises it
3. Muscles don’t have a depolarisation threshold, so each time there is an AP there’s a small contraction.
4. AP runs in all directions (unlike neurons) and runs down T tubules - critical bc the AP then hits the sarcoplasmic R. causing, calcium to be released
5. Causes filaments in myofibrils to run along each other and cause contraction

Question 9

What does the all or nothing approach of muscle fibres refer to?

Answer 9

Referes to how an AP always results in a muscle twitch - we modulate force by how many motor neurons we activate.

Question 10

Describe the process of muscle contraction in terms of extrafusal and intrafusal muscle fibres

Answer 10

1. Message is sent down from brain and reaches spinal cord
2. Gamma motor neuron innervates intrafusal fibres and alpha motor neuron innerates extrafusal
3. Extrafusal contracts bulk of muscles. Intrafusal also contrcts muscles within spindle
4. Afferent nerves wrapped around intrafusal fibres pick up whether the muscle has been lengthened and feeds back to the spinal cord.

Question 11

Stretch reflex?

Answer 11

?

important to stand straight after a long time etc when muscles get tired

Question 12

What are golgi tendon organs

Answer 12

• within the tendon
• when tension is detected in the tendon, info is sent back via sensory neuron to the spinal cord, and the alpha motor neuron is inhibited to limit chances of damage

Question 13

What does tetrodotoxin do?

Answer 13

Main component of blue ringed octopus venum which blocks sodium channels and kills human, mainly due to respiratory muscle paralysis

Question 14

What does botox do?

Answer 14

Enters terminals of axons and blocks Ach release - paralysis

Question 15

What is brody Myopathy

Answer 15

Severe cramping of skeletal muscles after exercise - gene mutation for a protein channel found in sarcoplasmic reticulum that helps bring Ca2+ back into SR at the end of muscle contraction
–> the calcium stays arund for too long and keeps the muscle contracted.
painful.