Skeletal muscle physiology Flashcards
What are the three types of muscle?
Smooth, cardiac, skeletal
Which muscle types are striated?
skeletal and cardiac
Cardiac muscle is subject to voluntary control. TRUE OR FLASE
False- skeletal muscle is subject to voluntary control
What initiated skeletal muscle contraction?
motor neurone stimulation (neurogenic mechanisms)
as they are innervated by the somatic nervous system
Neuromuscular junctions present-NO gap junctions
What are skeletal muscle fibres organised into?
motor units
What does the number of muscle fibres per motor unit depend on
the function served by the muscle
What is a sarcomere and where is it found?
the functional unit of skeletal muscle
found between two Z lines
What is a motor unit
a single alpha motor neuron and all the skeletal muscle fibres it innervates
What are cardiac and smooth muscle innervated by?
autonomic nervosa system- involuntary
What are the dark and light bands visible under a light microscope
dark- caused by myosin thick filaments
light- caused by actin thin filaments
What initiates cardiac muscle contraction?
Myogenic (pacemaker potential) initiation of contraction
No neuromuscular junction but GAP JUNCTIONS PRESENT
In skeletal and cardiac muscle where is the Ca++ from?
skeletal- Ca++ entirely from sarcoplasmic reticulum
Cardiac- Ca++ from ECF and sarcoplasmic reticulum
What does the graduations of contraction depend on in skeletal muscle?
1- motor unit recruitment
2-summation of contractions
What does cardiac muscle graduations of contraction depend on?
The extent of heart filling with blood( preload) - Frank-starling mechanism
There is continuity of cytoplasm between nerve and skeletal muscle cells . TRUE or FALSE
false- there is no continuity of cytoplasm between nerve and skeletal muscle cells. Acetylcholine is the transmitter at neuromuscular junction
Give 3 examples of places where there are fewer fibres per motor unit and why?
they serve fine movements
external eye muscles
muscles of facial expression
intrinsic hand muscles
Give 3 examples of places where there are fewer fibres per motor unit and why?
they serve fine movements(~10 fibres per motor unit)
external eye muscles
muscles of facial expression
intrinsic hand muscles
Give an example of where Power is more important than precision and how many fibres per motor unit does the muscle have?
Thigh muscle
hundreds to thousands fibres per motor unit
muscles are attached to bones via
tendons
What is the functional unit of any organ?
the smallest component capable of performing all the functions of the organ
What are the four zones the sarcomere?
A-band
H-zone
M-line
I-band
What is the A-band?
Made up of thick filaments along with portions of thin filaments that overlap in both ends of thick filaments
What is the H-zone?
Lighter area within middle of A-band where thin filaments don’t reach
What is the M-line?
Extends vertically down middle of A-band within the centre of H-zone
What is the I-band?
Consists of remaining portion of thin filaments that do not project into A-band
Muscle tension is produced by sliding of myosin filaments over actin filaments TRUE OR FLASE
False- muscle tension is produced by sliding of actin filaments on myosin filaments
Force generation depends upon ________ ______ between thick (myosin) and thin (actin) filaments
ATP-dependent interaction
TRUE OR FLASE
ATP is required for both contraction and relaxation
TRUE
Ca++ is required to switch __ cross bridge formation
on
What is excitation contraction coupling
the process whereby the surface action potential results in activation the contractile structures of the muscle fibre
In the skeletal muscle fibres where is the Ca++ released from?
the lateral sacs of the sarcoplasmic reticulum
Where does the surface action potential spread down to?
transerve (T) tubules
- these are extensions of the surface membrane that dip into the muscle fibre
What does Ca++ bind to and what does this result in
binds to troponin- this results in repositioning of troponin-tropomyosin complex to uncover the cross-bridge binding sites on actin
What is the transmitter at the neuromuscular junction?
acetylcholine
Why is ATP needed during muscle contraction and relaxation
during muscle contraction- to power cross bridges
during relaxation- to release cross bridges and to pump Ca++ back into the sarcoplasmic reticulum
