Muscle

Question 1

3 types of contractile cells and what are their roles?

Answer 1

Myoepithelial cells- Surrounds glands and squeeze to help it release its contents.

Pericytes- Smooth muscle like cells that alter diameter of capillaries and venules . Used if needed to move blood to different places throughout body.

Myofibroblasts- Transformed fibroblasts that assist with wound healing. Capable of collagen synthesis.

Question 2

Skeletal muscle layers

Answer 2

Myofilaments composed of actin and myosin

Myofibril- this is the muscle cell. Many nuclei that are displaced peripherally.

Muscle fiber

Fascicle

Muscle (largest)

Question 3

Endomysium

Answer 3

Thin connective tissue that is vascularized and surrounds a muscle fiber.

Question 4

Perimysium

Answer 4

Thin connective tissue that surrounds fascicle

Question 5

Epimysium

Answer 5

Thin connective tissue that is vascularized and surrounds muscle

Question 6

Sarcomere

Answer 6

Basic contractile unit of muscle. Z lines are the boundaries

Question 7

Anchors for the actin myofilaments

Answer 7

Z lines

Question 8

Z line is located in the middle of the ___ band

Answer 8

I band, which is strictly actin only

Question 9

H band consists of which myofilaments

Answer 9

Myosin only

Question 10

M line is in the middle of the ___ band

Answer 10

H band, which is myosin only

Question 11

A band contains which myofilaments

Answer 11

overlapping actin and myosin filaments

Question 12

During contraction, which two bands shrink?

Answer 12

HI:)
H (only myosin) and I bands (only actin) shrink.

causes overall sarcomere to shorten, and Z lines will come closer together

Question 13

During contraction, what happens to the A band?

Answer 13

It stays constant, same size

Question 14

T system

Answer 14

Facilitates synchronous contractions

Question 15

T tubules

Answer 15

At the A band/ I band junction. Extension of plasma membrane.

Question 16

Sarcoplasmic reticulum

Answer 16

Adjacent to t-tubules
Similar to smooth ER found in other types of cells
-Contains Ca2+, which is released during depolarization. Dispersed by T tubules and activates Actin and myosin sliding.

Question 17

Where is cardiac muscle located

Answer 17

In the myocardium of the heart wall

Question 18

Character of cardiac muscles

Answer 18

Has characteristics of both smooth muscle and skeletal muscle
Like smooth muscle, it has continuous contraction due to the autonomic nervous system
Like skeletal muscle in that the contractions are forceful and have multiple nuclei/mitochondria per cell. (Some cardiac cells have only 1 nuclei, but most have 2)

Involuntary (SM), forceful, continuous contraction, initiation of contraction modulated by autonomic nervous system

Question 19

Contraction of cardiac muscles are coordinated by

Answer 19

Purkinje fibers, which are modified cardiac muscle cells

Question 20

Cardiac muscle appearance

Answer 20

Woven appearance
Striated structure 
Central nuclei- single of binucleate 
-Fiber ends branch longitudinally.
-Contains intercalated discs. Contractile anchors between adjacent cells. Rapid conduction of depolarization.

Question 21

How do cardiac muscles communicate

Answer 21

Gap junctions within intercalated discs. Intercalated discs anchor adjacent cells and allow rapid conduction of depolarization.

Question 22

Intercalated discs

Answer 22

Site of gap junction. anchor adjacent cells and allow rapid conduction of depolarization.

Question 23

Smooth muscle location

Answer 23

Typically lines walls of hollow viscera (gut, ureter, fallopian tubes)

Question 24

Organization of smooth muscle

Answer 24

Circumferential, longitudinal,

Question 25

innervation of smooth muscle

Answer 25

Involuntary, autonomic control in MOSTLY parasympathetic, but some sympathetic

Question 26

__ fibers surround the outside of a smooth muscle cell

Answer 26

Elastic

Question 27

Characteristics of smooth muscle

Answer 27

• Fusiform-shaped cell (spindle shape appearance)
• Single, central nuclei
• Contractions are sustained, forceful, require little ATP, contractions reduce lumen diameter

Also contains actin and myosin filaments and elastic fibers on the outside

Question 28

How does smooth muscle appear when contracted

Answer 28

When contracted, it shrinks and twists (due to actin and myosin and elastic fibers) and appears like a cork screw

Question 29

Two main types of smooth muscle activation

Answer 29

Electrical coupling

• Single unit smooth muscle
• Multi unit smooth muscle

Contractile responses

• Tonic (continuous)
• Phasic (rhythmic)

Question 30

Are smooth muscles commonly single or multi unit?

Answer 30

Single unit is most common. This is when the cells contract as a single unit waves of slow, spontaneous contraction.
Found in gut, bladder

Question 31

Characteristics of multi unit smooth muscle

Answer 31

Less common compared to single unit. Rapid, brief, and intermittent contraction.

Found in the iris, large arteries, and veins

Question 32

Tonic vs phasic smooth muscle contractile responses

Answer 32

Tonic- Constant tone. BV walls airways and sphincters. Prevents muscle from being stretched out of shape.

Phasic- on/off/on/off. Typically not contracted, but has intermittent contractions.

GI, urinary, large arteries, reproductive tract