Chapter 10 (Muscular Tissue XIV)

Question 1

Smooth Muscle Tissue

Answer 1

Usually activated involuntarily
Action potentials are spread through the fibers by gap junctions
Fibers are stimulated by certain neurotransmitter, hormone, or autorhythmic signals

Question 2

Smooth Muscle Tissue is found in the

Answer 2

Walls of arteries and veins
Walls of hollow organs
Walls of airways to the lungs
Muscles that attach to hair follicles
Muscles that adjust pupil diameter
Muscles that adjust focus of the lens in the eye

Question 3

Microscopic Anatomy of Smooth Muscle

Answer 3

Contains both thick filaments and thin filaments which are not arranged in orderly sarcomeres
No regular pattern of overlap thus not striated
Contain only a small amount of stored Ca++
Filaments attach to dense bodies and stretch from one dense body to another
Dense bodies

Question 4

Dense bodies

Answer 4

Function in the same way as Z discs

During contraction the filaments pull on the dense bodies causing a shortening of the muscle fiber

Question 5

Visceral (Single Unit) Smooth Muscle

Answer 5

Tubular arrangement in walls of small arteries, veins, and hollow organs
Autorhythmic, connected with gap junctions, contract in unison

Question 6

Multiunit Smooth Muscle

Answer 6

Many nerve connections, few gap junctions

Found in large arteries, airways, arrector pili muscles, muscles in eye that adjust pupil diameter and lens focus

Question 7

Physiology of Smooth Muscle

Answer 7

Contraction lasts longer than skeletal muscle contraction
Contractions are initiated by Ca++ flow primarily from the interstitial fluid
Ca++ move slowly out of the muscle fiber delaying relaxation
Able to sustain long-term muscle tone

Question 8

How is the Smooth Muscle able to sustain long-term muscle tone?

Answer 8

Prolonged presence of Ca++ in the cell provides for a state of continued partial contraction

Question 9

The Smooth Muscle’s ability to sustain long-term muscle tone is important in the …

Answer 9

Gastrointestinal tract where a steady pressure is maintained on the contents of the tract
In the walls of blood vessels which maintain a steady pressure on blood

Question 10

Most smooth muscle fibers contract or relax in response to:

Answer 10

Action potentials from the autonomic nervous system
Stretching
Hormones
Changes in pH, oxygen and carbon dioxide levels