Muscle physiology Flashcards
What are the types of muscles?
Skeletal muscle
Cardiac muscle
Smooth muscle
Explain each one
Skeletal: attached to bone, facilitate movement around joints
Cardiac: only in hear, moves blood through circulatory system
Smooth muscle: muscle for internal organs and tubes, influences movement of material into, out of and within body
What is the characteristic skeletal and cardiac muscle share?
Both are striated muscle that can be seen thanks to light and dark bands under microscope
How is skeletal muscle attached to bones?
Attached via tendons
What are the types of muscle twitches?
Type I (slow twitch)
Type II (fast twitch oxidative)
Type IIb (fast twitch glycolytic)
Explain each type
Type I: subset of skeletal muscle associated with endurance type performance
Type II: associated with performance where power needs to be generated (100m sprint) - uses oxidative pathway
Type IIb: associated with power generation but its explosive generation of power (jump, punching, power lifting) - uses glycolytic pathways
What is an extensor muscle?
Bones moves away from each other when muscle contracts
What are muscle fibers?
Long, cylindrical cells with up to several hundred nuclei
True or false: Are skeletal muscles sheathed in connective tissue?
True. Sheathed in connective tissue with groups of adjacent muscle fibers bundled together
How do cell organelles names change when they are muscle cells?
Sarcoplasm - cytoplasm
Sarcolemma - cell membrane
Sarcoplasmic reticulum - endoplasmic reticulum
Explain smooth muscle
Found in walls of “tube” such as blood vessels, gi tract in sphincters
Associated with autonomic functions
Hass less myosin than skeletal
What influences smooth muscle?
Sympathetic and parasympathetic neurons and hormones and paracrine signals
Explain contraction in smooth muscle
Alternates between contraction and relaxation
What is phasic smooth muscle?
Muscles that undergo periodic contraction and relaxation cycles
What is tonic smooth muscle?
Muscle that is continuously contracted
How do cells communicate with neighboring cells?
Cells that are electrically connected by gap junctions are single unit smooth muscle.
Cells that aren’t link electrically are multiunit smooth muscle
How is muscle contraction defined?
By how shape of muscle which is contracting changes or by extension or motion
What governs muscle contracion?
Sliding filament theory
What is sliding filament theory?
overlapping thick and thin filaments slide past each other in an energy dependent manner as a result of actin-myosin crossbridge movement
What are the two important types of contraction?
Isometric
Isotonic
Explain the effect on muscle these contractions have (Isometric)
Isometric: occurs when two ends of a muscle are held at a fixed distance, causes the development of tension with the muscle -> series elastic elements allow the fibers to maintain constant length -> muscle remains static
Explain the effect on muscle these contractions have (Isotonic)
Isotonic: occurs when on end of muscle is free to move and the muscle shortens -> creates force as the muscle shortens and moves a lot -> constant tension
What do the T-tubules of the skeletal muscle fiber do?
Allow action potentials to move rapidly into the interior fiber and release calcium from sacroplasmic reticulum
What is myofibril of the skeletal muscle fiber?
Intracellular bundles of contractile and elastic proteins
Explain thick filaments and thin filaments
Thick filament: made of myosin
Thin filament: made of actin
Myosin binds to actin -> creates crossbridge between thick and thin filament
What is the contractile unit of myofibril?
Sacromere
What is the myofibril composed of?
Of two Z disks and filaments between them
What bands are found in the myofibirl?
I band: thin filaments
A band: runs in length of thick filaments
Central H band: occupied by tick filament
Which disks represent attachment site for myosin and actin?
M line and Z disks
Explain neuro-muscular junction
Synaptic connection between the terminal end of a motor nerve and a muscle
Skeletal muscle concentration require neuronal activation of muscle fibers by either reflex or voluntary neuronal pathways
What is the neurotransmitter responsible for signal transduction at neuromuscular junction?
Acetylcholine which binds to nicotinic receptors on the post synaptic membrane which possess an integral ion channel protein
What impulses are transmitted by neuromuscular junction?
Transmits excitatory impulses from motor neurons to muscle fibers
What does the process of excitatory impulse involve?
Involves the release of acetylcholine from vesicles in the motor neuron axon terminal into the synaptic cleft
What happens when the action point reaches the motor neuron?
A large volume of ACh is released which leads to sufficient EPP that trigger self-propagating muscle action potential
What are motor units?
Comprised of one motor neuron and all of the muscle fibers which are innervated by various branches of its axon
Explain how large motor units affect axon and cell body
Large motor units = larger the axon = larger cell body
What is recruitment and summation?
Grading the amount of force used in any given action
- recruiting more motor units for given contraction
- increasing the frequency of rate of firing of motor units
True or false: all motor units stimulated in muscle contraction
False: NOT all motor units stimulated in muscle contraction
-> positive force of contraction increase rate of firing of motor units
How many bands of muscle are there?
4
