Lecture 15 - movement and muscles

Question 1

What are the 6 ways we can characterise movement?

Answer 1

1. muscle groups/limb configuration
2. speed
3. accuracy/variability
4. force output
5. rhythmically
6. dynamic/postural

Question 2

What are muscles called when they pull in the same direction?

Answer 2

synergists

Question 3

What are muscles called when they pull in opposite directions?

Answer 3

antagonists

Question 4

What is a neuromuscular junction?

Answer 4

the synapse of motoneurons with muscle

Question 5

Describe how motoneurons work?

Answer 5

1. AP at MN synapse releases ACh presynaptically
2. ACh activates Na+ channels on sarcolemma
3. AP in muscle goes to T tubules then sarcoplasmic reticulum
4. SR releases Ca++ ions
5. Ca++ binds to troponin
6. Troponin interacts with myosin
7. Myosin can now interact with actin
8. Once AP has passed, Ca++ pumped back into SR
9. Myosin and actin uncouple

Question 6

What are the 2 different types of muscle fibres?

Answer 6

1. Type I - takes longer to reach high capacity and have a high resistance to fatigue
2. Type II - faster, can generate high force but not resistant to fatigue

Question 7

What is proprioception/kinaesthesia?

Answer 7

the awareness of position and state of our various body parts without the help of vision.

Question 8

What does proprioception rely on?

Answer 8

sensors that provide sensory feedback to the CNS about the state of the muscles

Question 9

Describe muscle spindles.

Answer 9

• found near the centre of the muscle
• have muscle fibres at either end
• inside there is a collagen fibre with sensory endings wrapped around the fibres

Question 10

What are the 2 types of sensory neurons that innervate muscle spindles?

Answer 10

1. group IA afferents
2. group II afferents

Question 11

When do group IA afferents respond?

Answer 11

during dynamic changes in muscle length

Question 12

When do group II afferents respond?

Answer 12

convey less information on the dynamic aspects of changes in length and more on the static length of muscle

Question 13

What do Golgi afferents do?

Answer 13

gives information on the tension in the muscle

Question 14

What does alpha/gamma co activation allow for?

Answer 14

the spindle to be pulled at either side so to remain active during contraction and give feedback to the neurons

Question 15

What is a motor unit?

Answer 15

a motoneuron and the muscle fibres it innervates
smallest functional unit in the body
muscle fibre only innervated by one motoneuron but a motoneuron can innervate several muscle fibres

Question 16

Name the 5 descending spinal pathways.

Answer 16

1. corticospinal - voluntary and fine manipulative movements
2. rubrospinal - voluntary movements
3. reticulospinal - posture, locomotion, some control of voluntary movements and grasping
4. tectospinal - neck and head movements
5. vestibulospinal - posture and balance