Muscle Tissue- Week 9

Question 1

what are the 3 different muscle types

Answer 1

Skeletal, cardiac & smooth muscle

Question 2

Compare and contrast the 3 types of muscle (Speed of contraction, Voluntary control. Nuclei/cell, Contraction control, function)

Answer 2

*Speed of contraction:
skeletal-Fast
Cardiac- Intermediate
smooth- Slow
*Voluntary control:
skeletal-yes
cardiac-No
smooth-No
*Nuclei/cell:
Skeletal-many
Cardiac-single
Smooth-single
*Contraction control
Skeletal- Nerves
Cardiac- spontaneous(moved by nerves)
Smooth- Nerves, hormones, stretch
*Function:
Skeletal- body movement
Cardiac- cardiac contraction
smooth- visceral and circulatory

Question 3

Describe how skeletal & cardiac muscle contracts

Answer 3

-neuromuscular junction releases acetylcholine- bind to receptors nicotinic channels(ion channels)
-cation channel opens- influx of sodium & calcium ions to enter
-membrane potential increases- wave of depolarisation along the sarcolemma- when reaches a T-tubule
-wave of depolarisation goes down the T-tubule
-triggers the opening of voltage gated calcium channels to open on the SR
-Calcium (Ca2+) is stored in sarcoplasmic reticulum (SR)
-causes the calcium ions to travel out the SR and into the sarcoplasm
-free intracellular calcium conc increases in sarcoplasm
-calcium binds to troponin exposing myosin-binding site
- crossbridge-cycle happens- muscle contracts

Question 4

what is the pathway of skeletal muscles/ how’s it organised

Answer 4

Muscle → muscle fibre bundle → muscle fibre → myofibrils → myofilaments

Question 5

what is the ER called in muscle cells

Answer 5

sarcoplasmic reticulum (SR)

Question 6

describe how cardiac muscle contacts

Answer 6

• no neuromuscular junction, its just a current from the SAN (sinoatrial node)
  -this spreads via gap junctions into the next cardio myside
  -spread of depolarisation along the sarcolemma
  -reaches voltage gated calcium channel and they open
  -calcium ions flood in the sarcoplasm
• calcium then can bind to the calcium gated calcium channels
  -this enables for the release from the SR
• the wave of depolarisation keeps traveling and goes down the T-tubule which reaches voltage gated calcium channel on the SR
  -causes release of calcium from the SR
• Calcium binds to troponin, exposing myosin binding site
• cross-bridge cycle happens -muscle fibre contracts

Question 7

how are the calcium ions restored back to normal in cardiac muscle and skeletal muscles

Answer 7

as the SR is smaller it will always have a larger concentration of calcium ions than the sarcoplasm- therefore there is an ATP pump which actively transports calcium back into the SR or can be actively pumped out the cell
*this causes tropomyosin to cover the myosin binding sites and muscle fibre relaxes

Question 8

why is calcium important

Answer 8

it allows for actin and myosin to interact with each other

Question 9

Describe how smooth muscle contracts

Answer 9

-intermediate filaments are bonded to dense proteins- forms a cytoskeleton
- and the actin is bonded to these dense proteins, each myosin molecules are surrounded by actin molecules
- there are heads on either side of the myosin filament which flick in opposite directions
-causes the actin filaments to become shorter and therefore the dense bodies gets pulled closer together
- results in the whole smooth muscle cell to contract

Question 10

What is the sarcolemma of a muscle fibre

Answer 10

the cell membrane