Muscle fun facts from lecture

Question 1

Myocyte

Answer 1

Cardiac muscle cell

Question 2

Troponin is like…

Answer 2

Calmodulin, because it binds lots of calcium.

Also you look for troponin antibodies in the blood of someone whom you suspect to have had a heart attack!

Question 3

Is smooth muscle striated?

Answer 3

NOPE. But cardiac and skeletal are :)

Question 4

Diameters of muscle cells

Answer 4

Smooth: 5um
Skeletal: 50-100um
Cardiac: 50-100um

It’s crucial that smooth has small diameter, because Ca can diffuse from SR on surface and still be effective (vs t-tubule with skeletal and cardiac).

Question 5

Tell me about DHPR and RyR

Answer 5

The key here in skeletal muscle is that DHPR is in t-tubule system is a Cav and is PHYSICALLY LINKED to Ryr, which means that you can take away Ca, and if channel still opens you can cause contraction.
This is different in cardiac muscle, where the receptors are physically separated so that you if you remove Ca you do NOT get muscle contraction

Question 6

Myosin head is

Answer 6

An ATPase

Question 7

Noodle analogy

Answer 7

Myofibril is an individual spaghetti noodle (actin and myosin) that has an ER.
All these noodles together make up one muscle cell (ie the bag of spaghetti is one cell).

Question 8

How long does the skeletal muscle cycle continue?

Answer 8

As long as there is Ca!

Question 9

with exercise

Answer 9

Add new myofibrils, which is necessary because you want to have each myofibril with an SR for Ca.. otherwise muscle would get thicker and you’d be SOL without Ca into the middle of it.
Myofibrils do NOT increase in diameter

Question 10

Myokines released by muscle

Answer 10

IL-6 is secreted by muscle cells and exercise increases secretion.
LIF (leukemia inhibitory factor) induces proliferation of satellite cells.
Irisin is released by muscle and increases energy expenditure by changing fat cells into brown-fat-like cells. In mice it reduces diabetes and obesity