2: Muscle Physiology I Flashcards
What are some physiological functions of skeletal muscle?
Posture
Voluntary and involuntary movement (inc. respiratory movement)
Heat production
Transport of metabolites between organs (whole body metabolism)
What are the three types of muscle?
Cardiac muscle
Skeletal muscle
Smooth muscle
Muscle is the largest type of ___ in the body.
tissue
What function do all three types of muscle have in common?
Produce tension and movement through CONTRACTION
Which types of muscle are striated?
Cardiac muscle
Skeletal muscle
Which type of muscle is unstriated?
Smooth muscle
How is striation recognised under a microscope?
Alternating light (actin) and dark (myosin) bands
Which division of the nervous system innervates skeletal muscle?
Somatic nerves
Skeletal muscle is (voluntary / involuntary).
voluntary
Which division of the nervous system innervates involuntary cardiac and smooth muscle?
Autonomic nervous system
Initiation of contaction in skeletal muscle is ___genic.
neurogenic
Skeletal muscle is arranged into ___ units.
motor
Are skeletal muscle cells joined by gap junctions?
No
one neuromuscular junction between motor neuron and motor unit
Does skeletal muscle have gap junctions?
No
Which ion triggers contraction of skeletal and cardiac muscle?
Ca2+
What is the only source of Ca2+ in skeletal muscle?
Sarcoplasmic reticulum
What two factors control the “power” of skeletal muscle contraction?
Motor unit recruitment i.e how many muscle fibres are contracting?
Summation of contractions i.e are contractions being reactivated rapidly?
There is no continuity of ____ between nerve and skeletal muscle cells.
cytoplasm
What is the neurotransmitter found at neuromuscular junctions?
Acetylcholine
What is a motor unit?
A single alpha motor neuron and ALL the skeletal muscle fibres it innervates
The excitation of one alpha motor neuron will stimulate the contraction of (one / multiple) motor units(s).
multiple units
What affects the number of motor units served by an alpha motor neuron?
Function of the muscle
Muscles which serves fine, precision movements (give examples) are have (more / fewer) muscle fibres.
Eye movements
Facial expression
Hand movements
FEWER FIBRES
Muscles which have powerful functions have (more / fewer) muscle fibres.
more
e.g limb movements
A muscle fibre is made up of how many cells?
One cell
A motor unit encompasses all the ___ ___ supplied by an ___ ___ ___.
muscle fibres
alpha motor neuron
What are the specialised contractile elements found within skeletal muscle cells?
Myofibrils
What is the functional unit of a myofibril?
Sarcomere
Name the two proteins found in a sarcomere, what colour they appear on microscopy and why?
Actin - light - thinner filaments
Myosin - dark - thicker filaments
Skeletal muscle fibres are (parallel / divergent).
parallel
By which structures are skeletal muscle fibres attached to bones?
Tendons
Each muscle fibre contains many ___.
myofibrils
Myofibrils have alternating segments of which two proteins?
Actin
Myosin
Within myofibrils, actin and myosin filaments are arranged into ___.
sarcomeres
What is the definition of an organ’s functional unit?
What is the functional unit of skeletal muscle?
Smallest component capable of performing all the organ’s functions
Sarcomere
What are Z lines?
Boundary lines splitting up sarcomeres
What are A bands?
Sections of overlapping actin and myosin filaments
What are H zones?
Lighter area in the middle of A bands where actin doesn’t overlap - myosin only
What are M lines?
Line extending down the centre of the A band, right in the middle of the H zone
What are I bands?
Remaining area of sarcomere where only actin is found
What is required for the sliding of myosin and actin filaments, which itself produces muscle contraction?
ATP
What binds to the myosin head to trigger detachment from the actin fibre?
ATP
Even if ATP is present, binding of the myosin head to a new section of actin filament will not occur without?
Ca2+
Why does rigor mortis occur?
No ATP present, so myosin head remains attached to actin fibre
Nerves generate an ___ ___, which travels to the ___ ___ junction and then to the skeletal muscle fibres.
action potential
neuromuscular junction
What is excitation contraction coupling?
Process by which surface action potential triggers contraction of skeletal muscle
In skeletal muscle, where is Ca2+ released from?
Sarcoplasmic reticulum
What structures are extensions of the surface membrane and invaginate into muscle cells, allowing surface action potentials to reach the sarcoplasmic reticulum?
T-tubules
Ca2+ is released by which specific part of the sarcoplasmic reticulum?
Lateral sacs
The myosin-binding sites on actin filaments are covered by which protein complex?
Troponin-tropomyosin complex
When Ca2+ binds to the troponin-tropomyosin complex, what happens?
Conformational change, complex moves and allows myosin to form cross bridge with actin
After an action potential, Ca2+ is (passively / actively) reabsorbed into the sarcoplasmic reticulum.
actively
requiring ATP
ATP is also required for cross bridge detachment
ATP is required for (contraction / relaxation) of skeletal muscle.
both
