lect 11 pt 6

What does muscle placement affect?

Leverage, speed, and excursion.

What happens when muscles are attached closer to the joint?

You can get more speed and more excursion out of them.

What happens when muscles are attached farther away from the joint?

You get more leverage.

What are agonists?

Groups of muscles that can do the same actions.

When doing a certain action, how are agonist muscles usually used?

Usually there is one main agonist muscle.

What can happen with the other agonist muscles during an action?

You may recruit some of the other agonists to help.

What are the other agonists called when they are recruited to help the main agonist?

Synergies.

What does "muscles are dynamic" mean in the lecture?

Muscles can change through strain, lack of strain, chronic shortening, and chronic stretching.

What happens when a muscle is strained?

Strain causes hypertrophy.

What happens to sarcomeres when strain causes hypertrophy?

Sarcomeres are added.

What happens when there is a lack of strain?

Lack of strain causes atrophy.

What happens to sarcomeres when lack of strain causes atrophy?

Sarcomeres are removed.

What happens to the muscle when sarcomeres are added in parallel?

Its cross-sectional area increases.

What does increased cross-sectional area from sarcomeres in parallel do?

It makes the muscle grow in diameter and gives it more strength.

What does "in series" mean when referring to sarcomeres?

Sarcomeres are arranged end to end.

What happens when a sarcomere is removed from the end of a muscle?

The muscle shortens.

What happens when a sarcomere is added to the end of a muscle?

The muscle lengthens.

What happens to muscle cells when they are diverse?

They have different fiber types and different strengths that we are born with.

Are people born with the same amount of each muscle fiber type?

No. People are born with a certain ratio and may have more of one type than another.

What can having more of one fiber type potentially make you better at?

It may make you a better marathoner or a better sprinter.

How can muscles be physiologically distinct?

Different muscles can have different predominant fiber types.

What type of fibers is the soleus mostly devoted to?

Slow oxidative fibers.

What type of fibers is the gastrocnemius mostly devoted to?

Fast glycolytic fibers.

Can motor units vary in size?

Yes.

Do muscles vary in their number of motor units?

Yes.

What does a greater number of motor units allow?

A greater gradation of force.

What does finesse and dexterity require?

Smaller motor units.

Which muscles does the lecture say may have the smallest motor units?

The eye muscles, possibly with about a 1-to-1 ratio.

Why do eye muscles need very small motor units?

They allow the finest, smoothest movements of the eyeballs.