Muscle Histology

Question 1

Skeletal muscle facts

Answer 1

Single multinucleated striated cells

Uses calcium to start contraction

Contractions are all or nothing in motor end plates

Somatic Muscles that are limited in regeneration.

Question 2

Smooth muscle tissue histology

Answer 2

Single, centrally located, elongated nuclei that run parallel with each other.

This occurs in both the inner and outer layers

Appears vaguely spindle shaped

Can appear wavy at times

Question 3

Smooth muscle innervation

Answer 3

Visceral autonomic nerves

Paracrine signaling also plays an important part

Slow twitch muscles

Question 4

Cardiac muscle histology

Answer 4

Cylindrical shaped, uni-nucleated cells with intercalated discs

Can appear branched because of the intercalated disc

Question 5

Cardiac muscle Innervation

Answer 5

Visceral autonomic Innervation via its conduction system (SA and AV nodes)

Takes innervation from vagus nerve also (parasympathetic)

All or nothing contractions fast twitch

Question 6

Skeletal myofiber formation

Answer 6

Originate from embryonic paraxial mesoderm

Multiple myoblasts fuse and differentiate to form one single muscle fiber.

Undifferentiated myoblasts become satellite cells which can give rise to new myofibers during injury

Question 7

Motor unit

Answer 7

One motor neuron innervates all myofibers near by

• cell body is located in ventral horn of spinal cord and axons are myelinated
• axon has several terminal branches that innervate multiple myofibers. Also consists of Motor end plates.

Question 8

Motor end plates

Answer 8

Site of axon: myofiber synapse

Question 9

Triad of myofiber

Answer 9

Encircle each myofibril

Contains
T-tubules (1)
Terminal cisternae of Sarcoplasmic reticulum (2)

Question 10

Sarcoplasmic / endoplasmic reticulum

Answer 10

Extensive network of smooth ER which stores calcium in muscles

Question 11

Sarcolemma

Answer 11

Cell membrane of myofibers

Question 12

Myofibrils

Answer 12

Longitudinal bundles of thin and thick myofilaments organized into sarcomeres

Contain mitochondria in between each myofibril

Question 13

Thick filaments

Answer 13

Myosin chains that have actin binding sites and ATP binding sites

Question 14

Thin filaments

Answer 14

Polymer of G-actin monomers

Contains my sling binding sites that are covered by tropomyosin

Question 15

Tropomyosin

Answer 15

Polypeptide chains that cover the myosin binding site on thin filaments

Troponin prescience removes tropomyosin and allows interaction between thin and thick filaments.

Question 16

3 subunits of troponin

Answer 16

TNT: binds to tropomyosin

TnC: binds to calcium

Tnl: regulates the interaction of actin-myosin interactions

Question 17

A band

Answer 17

dArk bands

Contains some over lap of thick and thin filaments

Question 18

H zone

Answer 18

Spots in the A band where no overlapping of thick and thin occurring

Question 19

I band

Answer 19

LIght band

Composed of only thin filaments (no thick filaments)

Question 20

Z disc

Answer 20

Middle area of I band that helps stabilize and keep thin filaments organized.

Question 21

Sarcomere

Answer 21

Functional contractile unit of muscle cells

Z disc- Zdisc

Question 22

M line

Answer 22

Middle of H zone and A band that keeps thick filaments organized and stable.

Question 23

Titin

Answer 23

Large protein w/ elastic properties that secure each end of the thick filaments to their Z disc

Prevents hyper stretching of the thick filaments

Question 24

(A)-actinin

Answer 24

Attaches proximal end of thin filaments to adjacent Z disc

Question 25

Desmin

Answer 25

Attaches a Z disc to a neighboring myofibril or neighboring Z-disc for stability

Question 26

Dystrophin

Answer 26

Attaches F-actin near the periphery to external lamina

Question 27

Unmyelinated vs myelinated nerves

Answer 27

Unmyelinated = 1 satellite cell covers multiple neurons 1 or 2 times.

Myelinated = 1 satellite cell covers 1 neuron multiple times