3.6.3 Skeletal Muscle

Question 1

Label a skeletal muscle

Answer 1

Check the biology folder

Question 2

Label a sacromere

Answer 2

Check biology folder

https://quizlet.com/245378977/sarcomere-labeling-diagram/

Question 3

What is the ratio between myosin and actin

Answer 3

1:6

Question 4

What is another way of saying myosin and actin

Answer 4

Thin filament - actin

Thick filament - myosin

Question 5

What are the different types of muscle

Answer 5

Skeletal muscle (conscious)

Cardiac muscle (unconscious)

Smooth muscle (unconscious)

Question 6

Describe the structure of skeletal muscle

Answer 6

Muscle tissue/ Tendon -> bundle of muscle fiber -> singular muscle fiber -> myofibrils -> sarcomere

Question 7

How do muscle cells add strength

Answer 7

Muscle cells fuse together and share nuclei and cytoplasm called sarcoplasm

If joined together like cells they would have weak points , myosin and actin overlap to provide strength

Question 8

What does multinucleated mean

Answer 8

Many nuclei in one cell

Question 9

Where are the mitochondria

Answer 9

In the sarcoplasm outside the sarcomeres

Question 10

Why do muscle fibres cells need to be multinucleated

Answer 10

Instruction for protein synthesis available along whole myofibril , no

Question 11

Describe the key features of fast twitch fibres

Answer 11

Rapid intense contractions
ATP from anaerobic respiration
Few mitochondria
Little myoglobin
Rapid build up of lactate
High concentration of anaerobic respiration enzymes
A store of phospho creatin

Question 12

Describe key features of slow twitch fibres

Answer 12

Sustain long contraction over long time intervals
Need to carry out aerobic respiration
Many mitochondria high conc of respiration enzyme
Lots of myoglobin (dark colour)
Many capillaries to ensure sufficient blood flow

Question 13

What is the definition of
Slow twitch /fast twitch fibres

Answer 13

Slow less powerful muscle contraction/ faster more rapid muscle contraction

Question 14

What is the definition of
Isotopic

Answer 14

The lighter bands where actin and myosin do not overlap

Question 15

What is the definition of:
Anisotropic

Answer 15

The darker bands in which actin and myosin filaments overlap

Question 16

What is the definition of:
myofibrils

Answer 16

single muscle fibres consisting of the protein myofilaments (actin and myosin) that make up the bundles of muscle fibres.

Question 17

What is the definition of:
Myosin

Answer 17

The thick filament protein found in skeletal muscle

Question 18

What is the definition of:
Actin

Answer 18

The thin filament protein that found in skeletal muscle

Question 19

What is the definition of:
Myoglobin

Answer 19

a bright red molecule found in muscle cells that stores oxygen

Question 20

What is the definition of:
Sarcoplasm

Answer 20

the cytoplasm shared between muscle fibre cells

Question 21

What is the definition of:
Sarcomere

Answer 21

a section of myofibril between two Z-lines that forms the basic structural unit of skeletal muscle.

Question 22

draw a diagram of a nuromuscular junction

Answer 22

check along side this link :

https://www.pinterest.co.uk/pin/551128073136443166/

Question 23

skeletal muscle is under the control of what

Answer 23

motor neurone and central nervous system as the actions are volentary

Question 24

how do motor neurones interact with muscles

Answer 24

it at a place called the neuromusclar junction , This is a specialized form of synapse that forms between a neurone and muscle fibre.

Question 25

blurb about the neuromusclar contraction of skeletal muscle

Answer 25

An impulse from a motor neurone arrives at the presynaptic membrane, the action potential causes calcium ions to diffuse into the neurone This stimulates vesicles containing the neurotransmitter acetylcholine (ACh) to fuse with the presynaptic membrane The ACh that is released diffuses across the neuromuscular junction and binds to receptor proteins on the sarcolemma (surface membrane of the muscle fibre cell) This stimulates sodium ion channels in the sarcolemma to open, allowing sodium ions to diffuse in This depolarises the sarcolemma, generating an action potential that passes down the T-tubules towards the centre of the muscle fibre These action potentials cause voltage-gated calcium ion channel proteins in the membranes of the sarcoplasmic reticulum (which lie very close to the T-tubules) to open Calcium ions diffuse out of the sarcoplasmic reticulum (SR) and into the sarcoplasm surrounding the myofibrils Enzymes in the synaptic cleft hydrolyse ACh and it is reabsorded into the presynaptic bulb to be reformed and packaged into vesicles https://theory.labster.com/muscle-contraction/

Question 26

when muscles contract : The I-band gets

Answer 26

shorter

Question 27

when muscles contract : The I-band gets

Answer 27

contracts / shortens

Question 28

when muscles contract : H-zone gets

Answer 28

gets shorter

Question 29

when muscles contract : the A-band gets :

Answer 29

stays the same

Question 30

describe a myosin filiment

Answer 30

formed from a number of myosin proteins wound together . each ends in a myosin head , which contains ATPase myosin head - gobular proteins myosin filiment - fibrous protein made up of several hundread molecules

Question 31

describe the structure of actin filliment

Answer 31

The actin filament is formed from globular protein whose molecules are arranged in long chains that are twisted into a helix.

Question 32

draw and anitate a actin chain :

Answer 32

go to 55 seconds https://www.youtube.com/watch?app=desktop&v=AM9-QyjSbno myosin head binding site actin sub unit Tropomyosin – long thin threads that are wound around the actin filament Troponin

Question 33

explain how a muscle contracts in the sacromere

Answer 33

1 An action potential travels into the T-tubules within the muscle fibre. 2.The action potential opens Ca2+ channels on the endoplasmic (sarcoplasmic) reticulum and Ca2+ diffuse into sarcoplasm down a concentration gradient. 3.Ca2+ cause tropomyosin molecules to pull away from the binding sites on the actin filament 4.ADP molecules attached to myosin heads allow them to bind to the actin filament and form a cross-bridge 5.Once attached the myosin heads changes angle, pulling the actin filament along and releases an ADP molecule. 6.An ATP attaches to the myosin head causing it to detach from the actin. 7.Ca2+ activate ATPase which hydrolyses ATP to ADP providing energy for the myosin head to return to its original position. 8.The myosin head (with ADP) reattaches further along the actin filaments and the cycle is repeated as long as there is Ca2+.    

Question 34

describe muscle relaxation

Answer 34

When nervous stimulation ceases, Ca2+ are actively transported back into the sacroplasmic reticulum. Tropomyosin blocks the actin filament again Myosin heads can’t bind any more, the muscle relaxes Antagonistic muscles can pull actin filaments out from between myosin.

Question 35

list 3 ways in which atp can be supplied to skeleral muscles :

Answer 35

Aerobic respiration - in mitochondria (dependent on adequate oxygen supply). Anaerobic respiration - (glycolysis), releasing lactic acid. Phosphocreatine - is stored in the sarcoplasm. Phosphates from phosphocreatine (creatine phosphotransferase) are added to ADP very quickly forming ATP. Phosphocreatine is replenished using phosphate from ATP when the muscle is relaxed.

Question 36

what is myoglobin

Answer 36

is a protein similar to haemoglobin , it has a high affinity for oxygen and only releses it when oxygen conc in the cell falls very low so acts as an oxygen store within muscle cells

Question 37

what does somatic mean

Answer 37

means volentary movement

Question 38

what is a sacroplasm

Answer 38

it is the cytoplasm for sarcomeres

Question 39

how do muscles act

Answer 39

they act in antagonist pairs against a incompressable skeleten