Muscle physiology

Question 1

What are the types of muscles?

Answer 1

Skeletal muscle
Cardiac muscle
Smooth muscle

Question 2

Explain each one

Answer 2

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

Question 3

What is the characteristic skeletal and cardiac muscle share?

Answer 3

Both are striated muscle that can be seen thanks to light and dark bands under microscope

Question 4

How is skeletal muscle attached to bones?

Answer 4

Attached via tendons

Question 5

What are the types of muscle twitches?

Answer 5

Type I (slow twitch)
Type II (fast twitch oxidative)
Type IIb (fast twitch glycolytic)

Question 6

Explain each type

Answer 6

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

Question 7

What is an extensor muscle?

Answer 7

Bones moves away from each other when muscle contracts

Question 8

What are muscle fibers?

Answer 8

Long, cylindrical cells with up to several hundred nuclei

Question 9

True or false: Are skeletal muscles sheathed in connective tissue?

Answer 9

True. Sheathed in connective tissue with groups of adjacent muscle fibers bundled together

Question 10

How do cell organelles names change when they are muscle cells?

Answer 10

Sarcoplasm - cytoplasm
Sarcolemma - cell membrane
Sarcoplasmic reticulum - endoplasmic reticulum

Question 11

Explain smooth muscle

Answer 11

Found in walls of “tube” such as blood vessels, gi tract in sphincters
Associated with autonomic functions
Hass less myosin than skeletal

Question 12

What influences smooth muscle?

Answer 12

Sympathetic and parasympathetic neurons and hormones and paracrine signals

Question 13

Explain contraction in smooth muscle

Answer 13

Alternates between contraction and relaxation

Question 14

What is phasic smooth muscle?

Answer 14

Muscles that undergo periodic contraction and relaxation cycles

Question 15

What is tonic smooth muscle?

Answer 15

Muscle that is continuously contracted

Question 16

How do cells communicate with neighboring cells?

Answer 16

Cells that are electrically connected by gap junctions are single unit smooth muscle.
Cells that aren’t link electrically are multiunit smooth muscle

Question 17

How is muscle contraction defined?

Answer 17

By how shape of muscle which is contracting changes or by extension or motion

Question 18

What governs muscle contracion?

Answer 18

Sliding filament theory

Question 19

What is sliding filament theory?

Answer 19

overlapping thick and thin filaments slide past each other in an energy dependent manner as a result of actin-myosin crossbridge movement

Question 20

What are the two important types of contraction?

Answer 20

Isometric
Isotonic

Question 21

Explain the effect on muscle these contractions have (Isometric)

Answer 21

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

Question 22

Explain the effect on muscle these contractions have (Isotonic)

Answer 22

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

Question 23

What do the T-tubules of the skeletal muscle fiber do?

Answer 23

Allow action potentials to move rapidly into the interior fiber and release calcium from sacroplasmic reticulum

Question 24

What is myofibril of the skeletal muscle fiber?

Answer 24

Intracellular bundles of contractile and elastic proteins

Question 25

Explain thick filaments and thin filaments

Answer 25

Thick filament: made of myosin Thin filament: made of actin Myosin binds to actin -> creates crossbridge between thick and thin filament

Question 26

What is the contractile unit of myofibril?

Answer 26

Sacromere

Question 27

What is the myofibril composed of?

Answer 27

Of two Z disks and filaments between them

Question 28

What bands are found in the myofibirl?

Answer 28

I band: thin filaments A band: runs in length of thick filaments Central H band: occupied by tick filament

Question 29

Which disks represent attachment site for myosin and actin?

Answer 29

M line and Z disks

Question 30

Explain neuro-muscular junction

Answer 30

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

Question 31

What is the neurotransmitter responsible for signal transduction at neuromuscular junction?

Answer 31

Acetylcholine which binds to nicotinic receptors on the post synaptic membrane which possess an integral ion channel protein

Question 32

What impulses are transmitted by neuromuscular junction?

Answer 32

Transmits excitatory impulses from motor neurons to muscle fibers

Question 33

What does the process of excitatory impulse involve?

Answer 33

Involves the release of acetylcholine from vesicles in the motor neuron axon terminal into the synaptic cleft

Question 34

What happens when the action point reaches the motor neuron?

Answer 34

A large volume of ACh is released which leads to sufficient EPP that trigger self-propagating muscle action potential

Question 35

What are motor units?

Answer 35

Comprised of one motor neuron and all of the muscle fibers which are innervated by various branches of its axon

Question 36

Explain how large motor units affect axon and cell body

Answer 36

Large motor units = larger the axon = larger cell body

Question 37

What is recruitment and summation?

Answer 37

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

Question 38

True or false: all motor units stimulated in muscle contraction

Answer 38

False: NOT all motor units stimulated in muscle contraction -> positive force of contraction increase rate of firing of motor units

Question 39

How many bands of muscle are there?

Answer 39

4