Muscles

Question 1

What is the purpose of muscle?

Answer 1

Force, movement, allows us to express and regulate ourselves

Question 2

Name two types of striated muscle.

Answer 2

Skeletal muscle (Voluntary movements - diaphragm) 
Cardiac (heart)

Question 3

Where is smooth muscle found?

Answer 3

Round things !! - GI tract, blood vessels, airways, uterus, bladder

Question 4

Describe skeletal muscle fibre

Answer 4

groups of cells joined together. Nuclei pushed to outside

Question 5

Describe Cardiac muscle cell

Answer 5

one nucleus in middle. Wee tentacles on ends that allow electrical signals to travel, and provide back up if anything goes wrong

Question 6

When and skeletal muscle formed and what from?

Answer 6

in utero - from mononucleate myoblasts

Question 7

Do myoblasts replace muscle when it is damaged? What happens ?

Answer 7

No. Cells can be replaced after injury by satellite cells but there is limited supply of these. (form new cells by differentiation).
Other fibres can undergo hypertrophy
Scar tissue may be made by fibroblasts

Question 8

Can smooth muscle cells replace themselves if damaged?

Answer 8

Yep - they can easily divide and repair

Question 9

What are muscles fibre bundles encased in?

Answer 9

connective tissue sheaths

Question 10

what attaches muscles to bones

Answer 10

tendons.

Question 11

why are muscles rich in blood supply

Answer 11

require lots of energy

Question 12

what is a myofibril? what is a sarcomere?

Answer 12

A myofibril is a wee bit of a muscle fibre (a straw out of a box of straws) It is a long chain of actin and myosin filaments.
A sarcomere is repeating units of myofibril

Question 13

Which muscle filament is thick and which is thin, and which one is the cross bridge on?

Answer 13

thick - myosin - cross bridge

thin - actin

Question 14

name a guiding protein in the sarcomere and state what it does.

Answer 14

Titan - makes sure the actin and myosin keep their shape and don’t hit each other or whatever

Question 15

What shapes do actin and myosin make and how many surround each other?

Answer 15

myosin are triangles
Actin is hexagons

each myosin is surrounded by 6 actin filaments

Question 16

what is the h zone.

Answer 16

The only thing that changes (actin and myosin filaments do not change size) it is the distance between them.

Question 17

Describe the cross -bridge cycle.

Answer 17

1- calcium levels rise - stimulate cycle
2- Energised (Due to ATP - pi) Myosin cross bridge binds to actin
3- ADP + Pi released , cross bridge flicks and contracts muscle
4- ATP binds to myosin - cross bridge detaches
5- hydrolysis of ATP to ADP + Pi energises the cross bride

Question 18

what develops with more overlap between actin and myosin?

Answer 18

MORE TENSION

Question 19

what are troponin and tropomyosin

Answer 19

regulatory proteins - regulate the access myosin has to actin

Question 20

Describe troponin and tropomyosin acting as a cooperative block.

Answer 20

So tropomyosin partially covers actin’s binding site for myosin
Troponin holds this in position.
Calcium binds to troponin.
Troponin changes shape, pulls the tropomyosin again.

When calcium is removed it goes back to the start

Question 21

What is the point of troponin and tropomyosin?

Answer 21

prevent random connection of cross bridges

Question 22

Where is calcium found in the body?

Answer 22

Sarcoplasmic reticulum - transverse tubules throughout the entirety of muscle fibre.
Mitochondria stores energy safety so it does not cause trouble

Question 23

how is calcium released from the sarcoplasmic reticulum?

Answer 23

DHP receptor connects to PHYONODINE receptor.
This is connected to the Ca2+ (voltage gated??) channel in the sarcoplasmic reticulum.
Depolarisation - ca channel opens
small release makes bigger release - positive feedback control .

Question 24

how is calcium taken back into the sarcoplasmic reticulum?

Answer 24

Calcium pump

Question 25

why cannot calcium remain in the screen for long?

Answer 25

it is highly toxic - infact cells can kill themselves by the rapid release of calcium

Question 26

What is a motor unit?

Answer 26

Motor neuron + muscle fibres.

one motor neurone innervates a lot of muscle fibres.

Question 27

what is force exerted by a muscle called?

Answer 27

Tension

Question 28

What is force exerted on a muscle called?

Answer 28

Load

Question 29

what are isometric contractions - examples

Answer 29

contraction of a constant length - e.g. weight lifting

Question 30

what is a isotonic contraction?

Answer 30

contracting with shortening length - (also called concentric) e.g running

Question 31

what is lengthening contraction ?

Answer 31

contraction with increasing length

Question 32

What does a single Action Potential to a muscle cause? and why would ya do this?

Answer 32

A twitch - to study muscles and motor neurones.

Question 33

what is the latent period?

Answer 33

time before excitation contraction starts - time taken for signal to travel and signal transduction to occur.

Question 34

what is contraction time? and what does it depend on?

Answer 34

occurs between start of tension and peak tension - depends on calcium conc.

Question 35

describe isometrics latent period and contraction event

Answer 35

shorter latent period - longer contraction event

Question 36

how does increasing load affect velocity and distance shortened?

Answer 36

velocity and distance shortened decreases

Question 37

What is tetanus?

Answer 37

A large amount of sustained level contraction . APS add up - summation. motor nerve that innervates a skeletal muscle emits action potentials at a very high rate.

Question 38

Why is titanic tension greater than twitch tension>

Answer 38

levels of Ca never get low enough to remove troponin and tropomyosin

Question 39

Is fused or unfused tetanus constant

Answer 39

fused

Question 40

what is the muscle length greatest isometric tension known as?

Answer 40

optical length - L0