MUSCLE

Question 1

what is the definition of muscle + what does it do

Answer 1

• a bundle of fibrous tissue that can contract to to produce movement

Question 2

what are the 3 types of muscle

Answer 2

• striated - locomotion and posture - voluntary
• smooth - involuntary
• cardiac

Question 3

what is the epimysium

Answer 3

a sheath of fibrous elastic tissue surrounding a muscle

Question 4

what is the perimysium

Answer 4

a sheath of connective tissue surrounding a bundle of muscle fibres (fascicles)

Question 5

what is the endomysium

Answer 5

connective tissue that surrounds each individual muscle fiber

Question 6

how is muscle developed in embryos - first step

Answer 6

muscle pattern laid down

Question 7

how is muscle developed in fetus

Answer 7

cells fuse and myofibril production

Question 8

how is the way muscle produced changed in adults

Answer 8

the ability to make new muscle is reduced

Question 9

what type of cells are skeletal muscle fibres made from + their general structure

Answer 9

• fused cells
  
  • multinucleated
• 3 cell types
  -sarcolemma
  -sarcoplasm
  -sarcoplasmic reticulum (SR)
  -transverse tubular system (TT)

Question 10

what is the structure of a sarcomere

Answer 10

unit of contraction of the myofibril

Z-line
either end of sarcomere
thin fiaments insertion

M-line
origin of thick filaments

A-band
overlap of thick and thin filaments

I-band
only thin filaments

Question 11

what is the structure of myosin and the 2 types of light chains

Answer 11

head - actin binding

tail - 2 intertwined heavy chains

2 regulatory light chains - ATPase activity

2 alkali light chains - stabilize myosin head

hinge - movement of myosin head

Question 12

what is the role of troponin on the actin filament

Answer 12

blocks myosin receptors

Question 13

what is the role of troponin on the actin filament

Answer 13

controls tropomyosin position

Question 14

what is the ‘triad’ made up from

Answer 14

2 cisternae and 1 T tubule

Question 15

how are T tubules formed

Answer 15

plasma membrane invaginating into muscle fibre

Question 16

how is contraction initiated - 5 steps , start from when motor nerve releases acetylcholine

Answer 16

motor nerve releases acetylcholine

action potential travels down T tubule

sarcoplasmic reticulum releases Ca++ into sarcoplasm

Ca++ activates troponin C

myofibril contracts

Question 17

how is calcium released into the sarcoplasm

Answer 17

• AP activates T tubule voltage gated L-type Ca++ (DHP receptor)
  - couple with ryanodine receptors on sarcoplasmic reticulum
  - opens channels to release Ca++ into sarcoplasm
  Ca++ released into myofibril activating troponin C and cross bridge cycling

Question 18

what is a DHP receptor

Answer 18

dihydropyridine receptor,
- normally a voltage-dependent calcium channel

Question 19

what is channel coupling

Answer 19

when CaV1.1 receptor DHP
- undergoes a conformational change
and leads to calcium being released from the SR store

Question 20

what are the 3 troponin molecules and what do they bind to

Answer 20

• C - binds Ca++
• I - anchors complex to actin
• t - binds to tropomyosin

Question 21

how is the cross bridge cycle initiated (sliding filament model basically)

Answer 21

• tropomyosin blocks myosin binding site
• Ca++ binds to troponin C causing a conformational change in the troponin complex
• troponin I moves away from actin filament
• Troponin T pushes tropomyosin away from myosin binding site on actin
• myosin head binds to actin

Question 22

what is the cross bridge cycle in 5 stages

Answer 22

1. atp binding
2. atp hydrolysis
3. cross bridge formation
4. release of Pi from myosin
5. adp release

Question 23

in what position is myosin originally in at the start of the cross bridge cycle

Answer 23

myosin head is attached to actin filament bc of power stroke from previous cycle

Question 24

how is ca2+ removed from the cytoplasm

Answer 24

-ca2+ pump at plasma membrane
-Na-Ca exchanger (NCX)
-Ca reuptake into Sr via Ca pump

Question 25

when contracting, what does the amount of force generated depend on?

Answer 25

no. of active muscles
cross sectional area of muscle
initial resting length of muscle
rate at which muscle shortens
frequency of stimulation

Question 26

what is the lenght-tension relationship in muscles a direct result of?

Answer 26

the cross bridge formation
and anatomy of thick + thin filaments

Question 27

why are muscles elastic (what molecule)

Answer 27

titin - need to double check this lol

Question 28

what is the force velocity relationship between muscles

Answer 28

as velocity increases force decreases