3.6.3 Skeletal Muscle Flashcards
Label a skeletal muscle
Check the biology folder
Label a sacromere
Check biology folder
https://quizlet.com/245378977/sarcomere-labeling-diagram/
What is the ratio between myosin and actin
1:6
What is another way of saying myosin and actin
Thin filament - actin
Thick filament - myosin
What are the different types of muscle
Skeletal muscle (conscious)
Cardiac muscle (unconscious)
Smooth muscle (unconscious)
Describe the structure of skeletal muscle
Muscle tissue/ Tendon -> bundle of muscle fiber -> singular muscle fiber -> myofibrils -> sarcomere
How do muscle cells add strength
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
What does multinucleated mean
Many nuclei in one cell
Where are the mitochondria
In the sarcoplasm outside the sarcomeres
Why do muscle fibres cells need to be multinucleated
Instruction for protein synthesis available along whole myofibril , no
Describe the key features of fast twitch fibres
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
Describe key features of slow twitch fibres
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
What is the definition of
Slow twitch /fast twitch fibres
Slow less powerful muscle contraction/ faster more rapid muscle contraction
What is the definition of
Isotopic
The lighter bands where actin and myosin do not overlap
What is the definition of:
Anisotropic
The darker bands in which actin and myosin filaments overlap
What is the definition of:
myofibrils
single muscle fibres consisting of the protein myofilaments (actin and myosin) that make up the bundles of muscle fibres.
What is the definition of:
Myosin
The thick filament protein found in skeletal muscle
What is the definition of:
Actin
The thin filament protein that found in skeletal muscle
What is the definition of:
Myoglobin
a bright red molecule found in muscle cells that stores oxygen
What is the definition of:
Sarcoplasm
the cytoplasm shared between muscle fibre cells
What is the definition of:
Sarcomere
a section of myofibril between two Z-lines that forms the basic structural unit of skeletal muscle.
draw a diagram of a nuromuscular junction
check along side this link :
https://www.pinterest.co.uk/pin/551128073136443166/
skeletal muscle is under the control of what
motor neurone and central nervous system as the actions are volentary
how do motor neurones interact with muscles
it at a place called the neuromusclar junction , This is a specialized form of synapse that forms between a neurone and muscle fibre.
blurb about the neuromusclar contraction of skeletal muscle
An impulse from a motor neurone arrives at thepresynaptic membrane, the action potential causescalcium ions to diffuseinto the neurone
This stimulatesvesiclescontaining the neurotransmitteracetylcholine(ACh) tofusewith the presynaptic membrane
The ACh that is released diffuses across the neuromuscular junction andbinds to receptor proteinson thesarcolemma(surface membrane of the muscle fibre cell)
This stimulatessodium ion channelsin the sarcolemma toopen, allowingsodium ionstodiffuse in
Thisdepolarises the sarcolemma,generating anaction potentialthat passes down theT-tubulestowards the centre of the muscle fibre
These action potentials causevoltage-gated calcium ion channel proteinsin the membranes of thesarcoplasmic reticulum(which lie very close to the T-tubules) toopen
Calcium ionsdiffuseout of the sarcoplasmic reticulum(SR) andinto the sarcoplasmsurrounding 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/
when muscles contract :
The I-band gets
shorter
when muscles contract :
The I-band gets
contracts / shortens
when muscles contract :
H-zone gets
gets shorter
when muscles contract :
the A-band gets :
stays the same
describe a myosin filiment
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
describe the structure of actin filliment
The actin filament is formed from globular protein whose molecules are arranged in long chains that are twisted into a helix.
draw and anitate a actin chain :
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
explain how a muscle contracts in the sacromere
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+.
describe muscle relaxation
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.
list 3 ways in which atp can be supplied to skeleral muscles :
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.
what is myoglobin
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
what does somatic mean
means volentary movement
what is a sacroplasm
it is the cytoplasm for sarcomeres
how do muscles act
they act in antagonist pairs against a incompressable skeleten
