Physio Lect 12 - Excitation Contraction Coupling

What percent of body mass does skeletal muscle make up?

40%

What muscle is the main component of the heart?

cardiac

Where do we find most smooth muscle?

GI tract, bladder, airways, blood vessels (hollow structures)

T/F: Cardiac muscle is a striated voluntary muscle

F - striated but involuntary

T/F: Skeletal Muscle is a striated voluntary muscle.

T

Which muscles are striated?

Cardiac and skeletal

Rank the muscles from most to least on sarcoplasmic reticulum content:

Skeletal, cardiac, smooth

All muscles require ___ for contraction

calcium

An increase in calcium results in ____. While a decrease in calcium results in ______.

contraction

relaxation

How does calcium move through the cell?

comes in through the sarcolemma, the sarcoplasmic reticulum stores and releases calcium, the mitochondria has minimal role

T/F: we need to use ATP in our muscles or contractions/energy

T

What ATPases do we use that are specific for muscles?

Myosin ATPase and Calcium ATPase

Explain the steps of skeletal muscle contraction:

signal comes from brain to motor neuron

action potential moves down T-tubule

Calcium released from ryanodine receptors on SR

Calcium binds troponin C, moves tropomyosin and exposes actin binding sites for myosin to bind

The sliding filament with myosin binds to actin through ATP hydrolyzation

Explain the steps of skeletal muscle relaxation:

SR takes up Ca through the SR Ca ATPase

Calcium in the SR is bound to calsequestrin - stores Ca

How do we increase contraction in skeletal muscle?

recruit more motor neurons to fire or increase the number of action potentials in the motor neuron in the limited amount of time.

Understand steps 1-4 for contraction and 1-3 for relaxation (rest covered in later lecture)

yay

Cardiac Myocytes are _____ cells, they are ____ and share the same basic structure as a _____ muscle cell.

specialized and involuntary

striated

skeletal

Contraction for myocytes is ______, based upon the propagation of action potential from the _____ node through intercalated discs

involuntary

sinoatrial

What sets Cardiac Myocytes aside from skeletal muscle?

action potential duration

ions

Looking at this diagram of the action potential, where is phase zero, and why do we see this spike?

This is due to sodium

Looking at this diagram of the action potential, where is phase one, and why does it look like that?

Slight repolarization due to potassium

Looking at this diagram of the action potential, where is phase two, and why does it look like that?

When calcium ions are entering into the cell, right when phase two is occuring is when we get force generation and relaxation

Understand the way that this diagram functions - it is very busy but you can do it.

great job

How can we increase cardiac muscle contraction?

we increase the action/myosin overlap (length tension relationship)

phosphorylation changes of proteins increase calcium sensitivity/activity of an enzyme (EG. phospholamban, calcium channel, troponin I)