Muscles Structue and Function

Question 1

Types of muscle

Answer 1

Smooth
Spindle, non straited, uni nucleated, involuntary, internal organs

Cardiac
Straighted, branched, uni nucleated, intercollated discs, involuntary,heart wall

Skeletal
Straited, tubular, multinucleated, voluntary, attatched to skelton 40/50 body weight

Question 2

Skeletal muscle

Answer 2

Made of muscle fibres

Each muscle fibre is a syncytial (fused embryonic cells) myoblasts fuse and form muscle cell

Muscle fibres are multinucleated cylindrical and parallel to one another

Question 3

Function skeletal muscle

Answer 3

Produce and control movement

Question 4

Connective tissue of skeletal muscle

Answer 4

Contractile and non contractile elements

Protects muscle fibres but need to be extendable and elastic

Connective tissue surrounds muscle,fibres and whole muscle:

> epimysium very dense surrounds whole muscle

> Extends beyond muscle as a tendon and connect to bone tendon blends with fibres if perimysuim
bundles of fibres are called fascicles and are surrounded by perimysium

> fascia supports muscle - surrounds it

> forms pathways for nerves blood vessles and lymphatics- good blood supply for continuous muscle contraction

> Endomysium surrounds individual muscle fibres- thin and inner part is called the basal lamena

Question 5

Sarcomella

Answer 5

specialised cell membrane which surrounds striated muscle fiber cells.

Question 6

Sarcoplasm

Answer 6

Muscle fibres cytoplasm

Contains mitochondria glycogen myoglobin

Gel like substance

Question 7

T tubules

Answer 7

Extension of sarcolema

Invagination a of the sarcolemma

Transmit the action potential from the cell membrane to the myofibrils to stimulate muscle to contract

Question 8

Sarcoplasmic recticulum

Answer 8

Extends through sarcoplasm

Network of fluid fillied membrane enclosed tubules which surrounds myofibrils

Storages and regulation of calcium released on demand

Question 9

Myofibrils + myofiliments

Answer 9

Myofibrils= within muscle fibres bundles of fibres

Run in a parallel fashion

Composed x2 myofilaments actin and myosin

Question 10

Sarcomere

Answer 10

Region between 2 z lines

Contractile unit of myofibrils

Repeated units of over lapping myofilaments

Lattice arrangement

Question 11

Z line

Answer 11

Dense protein material these supporting proteins run transversely across myofibrils and anchor thin actin filament

Attatched to sacrolema to provide stability

Question 12

A band

Answer 12

Darker middle composed of actin and myosin over lap near end rejoins

Extends whole length of myosin

Question 13

I band

Answer 13

Lighter less dense area contains rest of action no myosin

Z lines passes through the centre of each I band

Question 14

Straition

Answer 14

Alternating A bands and I bands cause striation appearance

Question 15

H zone

Answer 15

Only thick myosin

Question 16

M line

Answer 16

Support proteins that hold the myosin filaments together at the H zone is called the M line

Question 17

Myosin

Answer 17

Two identical twisted polypeptide chains each molecule has to globular head is attached to a flexible neck and a tail

The individual myosin molecules form a thick filament

Heads contain ATP binding sites and enzymes

Question 18

Actin

Answer 18

Individual actin join to form and actin filament that is twisted into a double helix

Each actin molecule has the myosin binding site where a myosin head can attach

Contains two other protein molecules – tropomyosin and a troponin complex

Question 19

Regulatory proteins

Answer 19

Help switch muscle contraction processes off and on

1. Tropomyosin- component of thin filament when skeletal muscle is relaxed it covers the myosin binding site in actin molecules preventing binding
2. Troponin- component of thin filament when Ca+ ions bind to troponin it changes shape this moves tropomyosin away from binding site and muscle contraction begins as myosin binds to actin

Question 20

Calcium Concentration

Answer 20

An increase in calcium concentration in the sarcoplasm starts muscle contraction

A decrease stops it

Question 21

Sliding filament theory

Answer 21

1. An action potential stimulates the muscle fibre as it travels through its extensive system of T tubules arriving at the neuromuscular junction
2. The action potential causes acetylcholine to be released attaching to receptors and then calcium ion channels in the sarcoplasmic reticulin to open
3. This causes the calcium ions stored in the sarcoplasmic reticulum to diffuse into the sarcoplasm down a concentration gradient
4. C.A.+ ions bind to troponin
5. Myosin head contains ATP binding site that acts as ATPase which hydrolises ATP to ADP and energy released is stored in myosin head
6. Troponin causes the ancillary protein tropomyosin that normally covers the binding sites on the acting filaments to be moved enabling the energised myosin bulbous head to link with the actin binding site forming cross bridges releasing phosphate
7. Once attached the myosin heads change their angle from 90° to 45° as it changes position it pulls the thin filament past the thick filament towards the centre of the sarcomere generating tension = powerstoke requires ATP and after this ADP is released
8. At the end of the powerstroke the cross bridge remains firmly attached to the actin until it finds another molecule of ATP as ATP binds to the ATP binding site on the myosin head the myosin head detaches from Actin

Question 22

Relaxation of muscle

Answer 22

1. When action potentials stop the release of ACH stops and acetylchlolinesterase breaks down ACH already in the synaptic cleft
2. This ends and the generation of muscle action potentials
3. Calcium channels in the sarcoplasmic reticulin close
4. Calcium is rapidly transported from the sarcoplasm to sarcoplasmic reticulum
5. Levels of calcium fall the tropomyosin slides back over the myosin binding sites on Actin
6. Thin filament slip back into relax positions

Question 23

Muscle tone

Answer 23

Small unit of muscle involuntary contracting to maintain muscle tone results in sustained contraction of muscle fibres What are units are constantly active and inactive Controlled by motor neurons in the brain

Question 24

Energy for contraction

Sources

Answer 24

X

Question 25

Explosive very short lived contractions use?

Answer 25

ATP and creatine phosphate

Question 26

High-intensity exercise

Answer 26

Glycolysis as an energy source it’s stored glycogen from muscle and liver anaerobic cellular respiration

Question 27

Insurance e.g. longer than 60 seconds

Answer 27

Aerobic cellular respiration

Question 28

Fascicle

Answer 28

Bundle of skeletal muscle surrounded by perimysium

Question 29

Fascia

Answer 29

Bundle of connective tissue primarily collagen