Muscle Tissue

Question 1

4 basic tissue types of the body

Answer 1

1. Epithelium
2. Connective Tissue
3. Muscle Tissue
4. Nervous Tissue

Question 2

Muscle cells (myocytes/myofibers) are specialized cells capable of contraction to produce movement for…

Answer 2

locomotion
propulsion
pressure regulation

Question 3

Muscle cells originate from the

Answer 3

mesoderm

Question 4

Sarcoplasm

Answer 4

cytoplasm of muscle cells

Question 5

sarcolemma

Answer 5

plasma membrane of a muscle cell

Question 6

Sarcoplasmic Reticulum

Answer 6

Smooth ER of muscle cell. Regulates Ca++ flow.

Question 7

Classifications of muscle tissue

Answer 7

Cross striated (skeletal and cardiac)
Smooth
Myoepithelial cells (basket cells)

Question 8

Size of skeletal muscle fiber

Answer 8

10 - 110um diameter

4mm - 50cm in length

Question 9

Size of cardiac muscle cell

Answer 9

15um diameter

100um length

Question 10

Size of smooth muscle cell

Answer 10

6 - 8um diameter
20 - 40um length
up to 1mm long in uterus

Question 11

Strongest muscles in the body

Answer 11

tongue (skeletal)
masseter (skeletal)
heart (cardiac)

Question 12

Muscle type that contracts fast and voluntarily

Answer 12

skeletal

Question 13

Steps in skeletal muscle development

Answer 13

1. Mesenchymal myoblasts align and fuse together, forming multinucleated tubes (myotubes)
2. Myotubes differentiate, forming functional myofilaments, and nuclei are displaced against the plasma membrane.
3. Some cells (satellite) do not differentiate and remain as mesenchymal cells. Role in muscle repair.

Question 14

CT layer that surrounds the muscle

Answer 14

epimysium

Question 15

CT that surrounds each fascicle

Answer 15

perimysium

Question 16

Reticular fiber between muscle fibers (myocytes)

Answer 16

endomysium

Question 17

Levels of organization of skeletal muscle

Answer 17

Muscle > fascicle > muscle fiber > myofibrils > myofilaments

Question 18

Dark vs light bands on muscle fiber

Answer 18

Dark = myosin
Light = actin

Question 19

Contractile elements of skeletal muscle

Answer 19

myofibrils - composed of repeating sections of myofilaments (myosin and actin, seen only in EM)

Question 20

Peripheral nuclei, AKA

Answer 20

hypolemmal nuclei

Question 21

What kind of protein is tropomyosin?

Answer 21

Regulatory. (regulates binding site on actin)

Question 22

A bands contain

Answer 22

Actin and myosin filaments overlapping (dark)

Question 23

I bands contain

Answer 23

actin only (light)

Question 24

H zone/M line contains

Answer 24

myosin only

Question 25

Z line

Answer 25

Bisects each I band. Where actin filaments are anchored. Length from one Z line to another denotes a sarcomere.

Question 26

What holds actin and myosin in position in the skeletal myofibril?

Answer 26

Desmin, tropomyosin, troponin

Question 27

Which myofilament moves during skeletal muscle contraction?

Answer 27

Actin slides across myosin toward the M line. I band and H band get shorter, but A band stays the same length (length of myosin filaments).

Question 28

Steps in skeletal muscle contraction

Answer 28

1. Ca++ binds to troponin, causing a conformational change in tropomyosin and exposing the binding site on actin 2. ATP > ADP on myosin heads allows formation of cross bridge. 3. Release of ADP causes myosin head action and slides actin toward the M line, shortening the sarcomere and causing muscle contraction

Question 29

T Tubules

Answer 29

Invaginations of the sarcolemma that allow membrance depolarization to quickly penetrate to the interior of the cell and induce calcium release from SR

Question 30

Type 1 muscle fibers

Answer 30

``` "red" slow contraction/slow fatigue oxidative metabolism lots of mitochondria high fat/low glycogen myoglobin ```

Question 31

Type 2 muscle fibers

Answer 31

``` "white" fast contracting/fast fatiguing anaerobic/glycolytic metabolism fewer mitochondria low fat, high glycogen ```

Question 32

Characteristics of Cardiac muscle cells

Answer 32

``` "cardiomyocytes" single cell with central nucleus striated and branching intercalated discs (gap junctions and desmosomes) many mitochondria sarcoplasmic reticulum ```

Question 33

Intercalated discs

Answer 33

Hold cardiomyocytes together. Transversely with desmosomes for structural support. Longitudinally with gap junctions for communication. Allows muscle fibers with work as syncytium, and AP to proliferate across membranes of cells.

Question 34

Purkinje cells

Answer 34

Cardiac muscle cells involved in impulse conduction. Bundles make up purkinje fibers. Cells are bigger and paler than contractile cardiac muscle cells, with sparse myofibrils at the periphery.

Question 35

Characteristics of smooth muscle cells

Answer 35

``` spindle shaped basal lamina and reticular fibers surround involuntary single, central nucleus no striations dense bodies instead of Z discs myofilaments are not ordered no T tubules poorly developed SR ```

Question 36

Single unit smooth muscle

Answer 36

sparse innervtion, but cells communicate via gap junctions, which allows them to act as a syncytium. In visceral organs.

Question 37

Multi unit smooth muscle

Answer 37

each fiber is independently innervated, contract separately, no gap junctions. In iris of eye.

Question 38

Functions of smooth muscle

Answer 38

1. Peristalsis (GI tract) 2. Vascular dynamics (alter blood flow, BP) 3. Propulsion (urinary bladder, uterus) 4. Secretion (minor role)

Question 39

Tunica mucosa

Answer 39

mucous membrane

Question 40

Tunica muscularis

Answer 40

innermost circular layer | outer longitudinal layer

Question 41

Appearance of smooth muscle upon contraction

Answer 41

Oblique arrangement of myosin, actin and intermediate filaments (allow shortening of the cell bu up to 80%), corkscrew shaped nucleus

Question 42

Myoepithelial cells

Answer 42

``` "Basket cells" Contractile, non muscle cells. Surround glandular cells Contain actin and myosin Role in muscle repair Similar to smooth muscle ```

Question 43

Satellite cells (skeletal muscle)

Answer 43

Don't differentiate Positioned between basal lamina and sarcolemma Retain mitotic potential Some muscle repair, allow limited regeneration

Question 44

Regeneration ability of muscle types

Answer 44

Cardiac: NO Smooth: limited regeneration from mesenchymal cells Skeletal: Limited via satellite cells *repair is always completed by scar tissue formation (fibroblasts)