Muscle

Question 1

what determines Max Tension in a muscle fiber

Answer 1

i. number of cross bridges formed—more cross bridges mean more tension ii. Muscle length—longer muscle, means more sarcomeres, means more cross bridges iii. Muscle type—fast vs slow twitch

Question 2

ligament vs tendon

Answer 2

Ligament: bone to bone Tendon: muscle to bone

Question 3

3 types of muscle and innervation

Answer 3

Cardiac: striated. Very similar to skeletal, but innervated by autonomic nervous system. Skeletal: striated. Aka, how proteins in msucle (actin + myosin) are set up. Innervated by motor neurons. Function: movement, posture Smooth : not striated. Innervated by autonomic nervous system. Function: digestion, breath, vasculature (venoconstriction) reproductive tract

Question 4

motor unit

Answer 4

Motor nueron and muscle cells that innervate it = motor unit In hamstrings; 1 motor neuron innervating 50 motor cells . Don’t need fine coordination In eyeball: 1 motor neuron to 1 muscle cell!!! Very fine control .

Question 5

what are each of these?

Answer 5

I band: only actin

M line : only myosin (stabilized w/ proteins)

A band: both

H zone : only myosin alone in the center

Question 6

THICK = ___

THIN =___

Answer 6

THICK = MYOSIN

THIN = ACTIN

Question 7

what do t-tubules do?

Answer 7

T tubules. when you fire an action potential into muscle cell, comes down into muscle cell membrane , down T-tubules, carried deep into cell, interacts with sarcoplasmic reticulum, causes calcium release (the signal for contraction)

-t-tubules are like the slides of the cell; shit slides down them and into the cell

Question 8

characteristics of myosin heads?

Answer 8

Myosin: myosin heads have a magnesium -ATP complex, and ATPase activity.( hydrolyze the ATP) and a site that binds to actin. Titan, protein, provides elasticity and stabilizes myosin

Question 9

how is calcium related to skeletal muscle function?

Answer 9

action potential. Goes down t tubules, deep into cell. Sarcoplas retic- action potential causes a change in t tubule membrane –acts as Ca+ channel. Opens up, pour Ca out of sarcoplasmic reticulum into cytoplasm

**ca binds to troponin, allowing actin/myosin binding**

Question 10

twitch vs tetanus

Answer 10

twitch: When the muscle is stimulated with a single electric shock of sufficient voltage, it quickly contracts and relaxes
tetanus: no visible relaxation between successive twitches. Contraction is smooth and sustained, as it is during normal muscle contraction in vivo. This smooth, sustained contraction is called complete tetanus.

Question 11

what is a crossbridge?

Answer 11

the globular head of a myosin molecule that projects from a myosin filament in muscle and in the sliding filament hypothesis ofmuscle contraction is held to attach temporarily to an adjacent actin filament and draw it into the A band of a sarcomere between the myosin filaments.

Question 12

tension vs muscle length results?

Answer 12

while muscle is too short, can’t generate enough tension- optimal at resting muscle state- and suboptimal again when muscle is too long, sarcomeres pulled apart

Question 13

what 3 factors influence muscle velocity?

Answer 13

1. Load
2. ATP-ase type (fast or slow)
3. Sarcomere length (comparing humans to a mouse, etc. same within species.)

• short sarcomeres high velocity . Long have slow velocity
• Why? Bc if youre longer, takes a longer amount of time for that same contraction to make it thru. This is why mice run so much faster than us.

Question 14

cardiac vs skeletal muscle refractory period

Answer 14

skeletal muscle refractory period is very short, while cardiac is quite long

why?

we do not want tetanus in cardiac muscle!!

Question 15

what does creatine phosphate do?

Answer 15

generates ATP, by Phosphorylating ADP.

Question 16

Muscle innervation experiments- what happpens if you take a muscle fiber and remove its motor neuron (denervate) a type 1 muscle and replace it with a type 2 motor neuron?

Answer 16

1. If you denervate Type 1 muscle and then reinervate with type 2 motor neuron, the type 1 cell adjusts and makes acetylcholine receptor and it will change into a type 2 muscle cell
2. If you denervate type 2 muscle and then reinervate with type 1 motor neuron, the cell becomes a type 1 muscle cell

Question 17

skeletal muscle innervated by ___

cardiac muscle innervated by ___

Answer 17

motor neurons

autonomic NS

Question 18

what do you call a bunch of myofibrils shortening? what are myofibrils made of?

Answer 18

a muscle contraction! myofibrils are composed of sarcomeres

Question 19

smooth muscle mechanism of contraction

Answer 19

1. Calcium goes into the cell through cell membrane. Calcium inside cell binds to calmodulin
2. Calmodulin goes to actin and removes the caldesmon and calponin regulatory proteins. Calmodulin also activates myosin kinase (adds phosphate

Question 20

when shortening (skeletal muscle) ; what band stays the same and what band gets smaller?

Answer 20

A band stays the same

I band gets smaller