Term
| Why does skeletal muscle have an effect on body temperature? |
|
Definition
| The body is 40% muscle (when not including fat). As metabolic rate goes up, this large mass increases body temperature. |
|
|
Term
| What is a requirement for contraction of muscle fibers? |
|
Definition
| Muscle cells are electrically isolated from each other. They have to receive motor neuron input at EVERY muscle fiber. |
|
|
Term
| What innervates the heart? |
|
Definition
| Autonomic nervous system. |
|
|
Term
| Where are the biggest and smallest heart cells found? |
|
Definition
| Biggest: Purkinje cells. Smallest: SA and AV node cells. |
|
|
Term
| Smooth muscle cells are interlaced with what? |
|
Definition
|
|
Term
| What do the calcium pumps of the sarcoplasmic reticulum do? |
|
Definition
| Called SERCA, they are ATP-dependent, and take calcium in from the cytoplasm. They are the "rate limiting step" on the road to relaxation. |
|
|
Term
| How many actin filaments surround one myosin filament? |
|
Definition
| Six actin surround one myosin. |
|
|
Term
| In the cytosol of skeletal and cardiac muscles, myofilaments "see" this, and it allows them to contract: |
|
Definition
|
|
Term
| In cardiac muscle, what does the relationship between the calcium transient and the L-type channels imply? |
|
Definition
| Most of the calcium in the Ca transient comes from the SR> So, influx of calcium by only the L-type calcium channels isn't enough to cause a full contraction. Basically, think of the L-type channels as activating the RyRs in the SR. |
|
|
Term
| During exercise, what hormones are around the cardiac cell and how does this increase contraction force? |
|
Definition
| Epinephrine (and norepinephrine) stimulate L-type channels, causing a larger SR release of calcium, causing a more forceful contraction. |
|
|
Term
| How do we keep calcium levels in the cardiac cell cytosol low? |
|
Definition
| Mostly via the Na-Ca exchange (3 Na IN for 2 Ca OUT), and also by the ATP-dependent sarcolammal Ca pump. |
|
|
Term
| In skeletal muscle, the calcium channels in the t-tubules act like what? |
|
Definition
| A voltage sensor that actually connects to the SR Ca release channel. This makes the Ca channel a "plug" for the RyR. |
|
|
Term
| Calcium-induced-calcium release is seen in which muscle type? What about mechanical coupling mechanism? |
|
Definition
| Calcium-induced-calcium release: Cardiac Muscle. Mechanical coupling mechanism: Skeletal Muscle. |
|
|
Term
| Which type of muscle is dependent on extracellular calcium concentration for contraction? |
|
Definition
| Cardiac. Skeletal muscle can contract for a long time without extracellular calcium. |
|
|
Term
| How do we get almost all of the calcium back into the SR? |
|
Definition
| By SERCA pumps. There are a few exchangers and pumps (like cardiac muscle) but very, very few. |
|
|
