Topic 7 - Muscles II

Question 1

What is the portion of muscle fibers controlled by a single nerve called?

Answer 1

Motor unit

*Note: a single muscle can have multiple motor units

Question 2

How are muscles connected to bones?

Answer 2

• They’re connected by tendons
• Tendons don’t change length with muscles exerting force on bones through pulling tendon.

*Notes only contracting muscles can shorten/pull bones.

Question 3

How does contraction of the muscle occur?

Answer 3

Occurs only when ACh is in contact with nicotinic receptor.

Question 4

What do flexing and extension refer to in muscles?

Answer 4

• Flexion = refers to bending of a limb
• Extension refers to straightening of a limb

Question 5

What does amplification of the force and speed of muscle contractions do?

Answer 5

It increases the strength and speed of limb movement by leverage.

Question 6

What happens if the bicep muscle shortens?

Answer 6

The hand moves a distance of 7cm

*Note: This is due to anatomical connection of bicep to forearm

Question 7

What is the disadvantage of the leaver system?

Answer 7

The bicep muscle needs to be x7 greater force than load that’s moved.

*Note: Velocity of hand is more rapid than shorten of bicep

Question 8

What are some examples of smooth muscle (autonomic nervous system) that’s involuntary?

Answer 8

Sympathetic:
- Blood vessels (noradrenaline)
- Sweat glands (ACh)
- Adrenal glands (ACh)

Parasympathetic
- Salivary glands (ACh)

Question 9

What are the characteristics of smooth muscle cells?

Answer 9

• much smaller than skeletal muscle fibres
• single nucleus
• divide throughout life (esp. when injury)

Question 10

What do myosin and actin do in muscle cells?

Answer 10

They both play a part in contraction of muscle cells (inside the muscle cell)

Question 11

What is the difference between mechanisms for smooth muscle vs skeletal muscle?

Answer 11

• Smooth muscle shortening is MUCH slower than skeletal muscle -> lower rate fatigue -> longer contracting periods