Skeletal Muscle and Nerve Tissue Histology

Question 1

What is the main function of skeletal muscle?

Answer 1

generate force for movement by turning ATP into mechanical energy, voluntary movements and postural stability

Question 2

What are the key characteristics of skeletal muscle?

Answer 2

The muscle is striated and multinucleated, located in the periphery (not center)

Question 3

What is a sacromere?

Answer 3

a contractile unit of muscle made of actin and myosin myofilaments

Question 4

What do chains of sacromeres link together form? and what do those form?

Answer 4

Sacromere chains linked together form myofibrils, which form the myofiber (which is the muscle cell)

Question 5

What fascial covering surrounds myofibrils?

What fascial covering surrounds a group of myofibers (fascicle)?

What fascial covering surrounds a group of fascicles (muscle)?

Answer 5

Endomysium

Perimysium

Epimysium

Question 6

List from one to four, the formation of muscle

Answer 6

1. Groups of sacromeres form myofibrils
2. Groups of myofibrils form muscle fiber (myofiber)
3. Groups of myofiber form the fascicle
4. Groups of fascicles form the Muscle

Question 7

Myosin are thick filaments, what makes up myosin and what holds it in place?

Answer 7

They have 2 heavy chains with globular heads, which bind to actin with ATPase domains
2 light chains
Myosin is held in place by Titin proteins connected to Z-disk

Question 8

Actin or thin filaments are made of filamentous actin (f-actin) monomers, which bind to form double stranded chains. The length of the actin filament are determined by nebulin. Where are tropomyosin and troponin located in the Actin?

Answer 8

Tropomyosin strands wrap between the actin strands and troponin sits on tropomyosin strands and covers myosin bindin sites on actin filament so the myosin does not randomly contract

Question 9

What is the M-line of the sarcomere (myosin and actin together)?

Answer 9

attachment site for myosin (in the middle)

Question 10

What are z-disk in sarcomeres?

Answer 10

they separate sarcomeres, and is the site of attachment for actin and titin

Question 11

What is the H-band in sarcomeres?

Answer 11

space on either side of M-line where there is no actin (Hband/zone will shorter with contraction)

Question 12

What is the A-band in sarcomeres?

Answer 12

distance from the end of one myosin head to the head of the opposite myosin, where actin and myosin overlap

Question 13

What is the I-band in sarcomeres?

Answer 13

space on either side of the Z-disk where there is no myosin, (I-band will shorten with contraction)

Question 14

For contraction to occur, myosin must bind to actin, however, troponin blocks the myosin binding sites on the actin filaments, how contraction activated?

Answer 14

Calcium is released from the sarcoplasmic reticulum and binds to troponin

This causes a conformational change which pulls tropomyosin away, exposing the myosin binding sites so myosin and actin can bind

Question 15

For sliding filament mechanism of muscle contraction, what are key things to remember? (4)

Answer 15

1. thin filaments slide past thick filaments
2. Z-disks are closer together, H and I bands are smaller
3. All myofibrils contract at the same time
4. **Actin and myosin do not change in length, they just overlap

Question 16

What are typical of type I skeletal muscle fibers?

Answer 16

Slow, less powerful contraction

Many mitochondria

Slow fatigability

Question 17

What are typical of type IIA skeletal muscle fibers?

Answer 17

Intermediate, powerful contraction

Some mitochondria

Intermediate fatigability

Question 18

What are typical of type IIB skeletal muscle fibers?

Answer 18

Fast, powerful contraction

Few mitocondria

Rapid fatigability (anaerobic respiration)

Question 19

What is a sarcolemma?

Answer 19

membrane around each muscle cell

Question 20

What do transverse (T) tubules do?

Answer 20

membrane system penetrating the muscle cell to convey electrical impulses from sarcolemma into cell

Question 21

What are the sarcoplasm and sarcoplasm reticulum (SR)?

Answer 21

Sarcoplasm is cyotplasm of muscle cell

SR: tubular system acting like smooth ER, which are the terminal cisternae (flattened sac of SR on either side of T tubule) releases Ca to get contraction

Question 22

What is a triad for electrical impulse transmission?

Answer 22

the T tubule and 2 terminal cisternae

Question 23

What are the End feet?

Answer 23

connect T tubles with SR to allow Calcium release

Question 24

How is skeletal muscle innervation and how many nerves per muscle fiber?

Answer 24

they are innervated by peripheral alpha motor neurons from the anterior horn

1 nerve per muscle fiber, >1 muscle fiber per nerve

Question 25

How do the nerve axons transmit the signal to the muscle?

Answer 25

Release acetocholine into the synaptic cleft, causes end feet to release Ca+ and causing the contraction

Question 26

What soes the neruromuscular spindle apparatus do?

Answer 26

it has a relfexive response to prevent over stretching of a muscle

Question 27

What do extrafusal and intrfusal muscle fibers do in neuromuscular spindle apparatus?

Answer 27

Extrafusal contract the muscle Intrafusal (deep) sense length and rate of chang of the muscle, cause the response

Question 28

What do type Ia sensory nerve fibers do?

Answer 28

they are the afferent innervation of intrafusal fibers that send signals to the spinal cord

Question 29

what do alpha motor and gamma motor nerve fibers do?

Answer 29

they are the efferent innervation of extrafusal (alpha) and intrafusal (gamma) muscle fibers

Question 30

How do the type Ia fibers and alpha and gamma fibers talk to eachother?

Answer 30

Afferent Ia fibers sense stretch in intrafusal fibers and send signal to A and G efferent fibers, causing extra/intrafusal fibers to contract and shorten, relieving the stretch

Question 31

What makes up a neuron and what do they do?

Answer 31

Soma/body: contains organelles of neurons Dendrite: receives signals from other neurons Axon Hillock: connection between some and axon, summates all signals to make action potention Axon: conveys electrical impulse to synapse Synapse: transfers impulse from neuron to target tissue

Question 32

What makes up a nerve?

Answer 32

Axons-> groups of axons = Fasicle -> Nerve =groups of fascicles

Question 33

What fascia covers each axon, each fascicle and each nerve?

Answer 33

axon: endoneurium fascicle: perineurium Nerve: epineurium

Question 34

What are multipolar neurons?

Answer 34

multiple dendrites and one axon

Question 35

What are bipolar neurons?

Answer 35

one single dendrite with multiple extensions and one axon with the cell body in the middle

Question 36

What are pseudounipolar neurons?

Answer 36

one cell process with a single dendrite branch (receives signal) and axon branch (sends signal to muscle), with the cell body connected by a short single process

Question 37

What is a schwann cell (in PNS)?

Answer 37

surround axon and create myelin sheath in PNS, wrap around one part of one axon

Question 38

What is an oligodendrocyte?

Answer 38

surround axon and create myelin sheath in CNS, wrap around a part of many axons

Question 39

What is a myelin sheath?

Answer 39

circumferential layers of myelin allowing for faster signal conduction velocity