Skeletal and Cardiac Muscle Physiology

Chip Asbury

Skeletal muscles are organized

Hierarchically

Each invdvidal muscle cell is called

A muscle fiber

Muscle cells are

multinucleated

Individual muscle cell can extend how long

To the length of one whole muscle

Muscle fibers are packed with what

Myofibrils (little bundle of drinking straws)

Each myofibril is what

Chain of contractile units

How many muscle fibers can you have

hundreds to make up a myofibril

What is a sarcomere

the basic contractile unit of muscle fiber

Each sarcomere are composed of what

interdigitated filaments

What are examples of filaments

F-actin, Myosin

What does actin look like

Thin rope

What does myosin look like

Cross bridges

What do myosin cross bridges do

Responsible for shortening

1 sarcomere is composed of

thin and thin interdigitated filaments

What drives the shortening of the sarcomere

the sliding between the thick and thin filaments

Thick filaments are studded with what

little bumps

what is the structure of a myosin molecule

coiled 2 alpha-helices which make up the stock, and two bumps which are N-terminus

What is actin composed of?

Thousands of identical little building blocks - globular actin

What is rigor mortis?

when your limbs become stiff postmortem

Electrical activation of the muscle turns on what?

the actin myosin interaction that drives the shortening

The command from your brain telling your muscle to contract comes from what

action potential activity on a motor neuron

What is a motor neuron?

A neuron that connects to a muscle cell

Electrical signals come down the axon terminal of a somatic motor neuron to trigger what

Acetylcholine to be released into between the end of the motor neuron and the beginning of the muscle

Acetylcholine binds to what

receptors on the muscle cell

what do receptors on the muscle cell do that are activated by acetylcholine?

Open and allow ions to flow

The opening of the channels does what

causes a rapid depolarization electrical change on the membrane

does the membrane voltage go up or down, why?

goes up because the channels open and starts a wave of electrical activity that propagates over the entire surface of the muscle cell

What kind of gated channels do muscle cells have

voltage gated