Skeletal Muscle Physiology 1 01/10/18 Flashcards
What are the 5 physiological functions of skeletal muscle/
Maintenance of posture Purposeful movement in relation to external environment Respiratory movements Heat production Contribution to whole body metabolism
What is the largest type of tissue in the human body?
Muscle
How many muscle types are there?
3
What are the three types of muscle?
Skeletal
Cardiac
Smooth
What are all three muscle types capable of?
Developing tension and producing movement through contraction
Which two muscle types are striated?
Skeletal
Cardiac
Which muscle type is unstriated?
Smooth
Which two muscle types are involuntary?
Cardiac
Smooth
Which muscle type is voluntary?
Skeletal muscle
What is striation visualized as under a microscope?
Alternating light and dark bands
Why are dark and light bands seen?
Alternating Actin (light) and Myocin (light) filaments
What innervates skeletal muscle?
Somatic nervous system
What innervates cardiac and smooth muscle?
Autonomic nervous system
Is the initiation of contraction in skeletal muscle neurogenic?
Yes
Is the initiation of contraction of cardiac muscle neurogenic?
No its Myogenic
Which has neuromuscular junctions present, cardiac or skeletal?
Skeletal
Which has Gap junctions present, skeletal or cardiac?
Cardiac
Where is the calcium from in skeletal muscle contraction?
Entirely from sarcoplasmic reticulum
Where is the calcium from in cardiac muscle contraction/
Extra cellular fluid
Sarcoplasmic reticulum
What is responsible for the gradation of contraction in skeletal muscle?
Motor unit recruitment
Summation of contractions
What is responsible for the gradation of contraction in cardiac muscle?
Depends on the extent of the heart filling with blood (preload)
Can one motor neurone be responsible for more than one muscle fibre?
Yes it can be responsible for many
What is a motor unit?
The motor neurone and all of the muscle fibres that is supplies
Is there continuity of cytoplasm between nerve and muscle cells?
No
What is the transmitter at a neuromuscular junction?
Acetylcholine
What connects cardiac muscle fibres?
Desmosomes and gap junctions
What does the number of muscle fibres per motor unit depend on?
The functions served by a muscle Fine movements (eye, facial expression) have fewer fibres
Where power is more important than precision are there many or few motor fibres?
Thousands
What are the parts of a muscle?
Whole muscle Muscle fibre Myofibril Sarcomere Actin and Myocin
Which filaments are thick and dark, actin or myocin?
Myocin
Are skeletal muscle fibres parallel or perpendicular?
Parallel lol
How long is a skeletal muscle cell/fibre?
The entire length of the muscle
How are skeletal muscle fibres bundled together?
Connective tissue
How are skeletal muscles attached to bones?
Tendons
What do bones, joints and muscle form to allow body movements?
Lever systems
What does each muscle fibre contain?
Myofibrils
What is a myofibril?
Specialised contractile intracellular structures
What are actin and myocin arranged into inside myofibrils?
Sarcomeres
What are the functional units of muscle?
Sarcomeres
What do Z lines seperate?
Sarcomeres
What are the 4 zones of a sarcomere?
A-band
H-zone
M-line
I-band
What is the A-band made of?
Thick filaments with thin filaments that overlap at both ends of the thick filament
What is the H-zone?
Lighter area within the middle of the A-band where thin filaments don’t reach
What is the M-line?
Extends vertically down the middle of A-band within the centre of the H-zone
What is the I-Band?
Consists of remaining portion of thin filaments that do not project in A-band
How is muscle tension produced?
Sliding of actin and myocin filaments
What is force generation dependent on?
ATP
True/False: ATP is only required for contraction
FALSE
It is also required for relaxation
What is required to switch on crossbridge formation?
Calcium
What is excitation contraction coupling?
The process whereby the surface action potential results in the activation of the contractile structures of the muscle fibre
When is calcium released from the sarcoplasmic reticulum in skeletal muscle?
When the surface action potential spreads down the transverse tubules, this is triggered by spread of action potentials down the T-tubules
Explain the excitation of actin/myocin
Ca2+ binds wiith troponin, pulling tropomyosin complex aside to expose the cross-bridge binding site for binding to occur
Binding of actin and myocin cross bridge triggers power stroke that pulls the thin filament inwards during contraction
Explain the massive diagram about how muscle contraction occurs
Ach is released from axon of a motor neurone, which causes an action potential to go down the T-tubules.
This triggers the release of calcium from the sarcoplasmic reticulum.
Calcium ions released bind to troponin on actin filaments which means tropomyosin is moved and the cross-bridge binding site is exposed.
The myosin cross bridge attaches to the actin and bends, pulling the actin towards the middle, powered by ATP.
