Lecture 18 Smooth and Cardiac Muscle Tissue

Question 1

Characteristics of Cardiac Muscle Tissue

Answer 1

Single mononucleated cells
Centrally positioned nuclei
Sarcomeric arrangement 
Cells communicate via gap junctions (intercalated discs)
Cells not directly innervated

Question 2

T-tubules of Cardiac Muscle Tissue

Answer 2

Not as extensive as in skeletal muscle
Each t-tubule interacts with one cisterna (rather than two in skeletal muscle) - diad rather than triad
Located at the level of the Z lines

Question 3

Composition of Intercalated disks

Answer 3

Macula Adherentes (desmosomes)
Fascia Adherentes
Gap Junctions

Question 4

Macula Adherentes of Intercalated Disks

Answer 4

Link intermediate filaments (desmin) of adjoining cardiac muscle cells
Part of transverse component

Question 5

Fascia Adherentes of Intercalated Disks

Answer 5

Anchor actin filaments of sarcomeres

Part of transverse component

Question 6

Gap Junctions of Intercalated Disks

Answer 6

Part of longitudinal component

Question 7

Atrial Natriuretic Peptides (ANPs) are secreted by:

Answer 7

Cardiac muscle cells in atria

Question 8

What are the functions of ANPs?

Answer 8

Regulate fluid electrolyte balance

Relax vascular smooth muscle - reduces blood volume and pressure

Question 9

ANP is stored as a ______ in secretory vesicles

Answer 9

Prohormone

Question 10

The release of ANP is stimulated by:

Answer 10

Atrial stretch - results in cleavage of prohormone

Question 11

Synonyms of Smooth Muscle Tissue

Answer 11

Involuntary

Visceral

Question 12

Characteristics of Smooth Muscle Tissue

Answer 12

Single mononucleated cells w/ central nuclei 
No sarcomeric arrangement
Innervated via ANS or enteric system 
Do not respond "all or none"
Connected via gap junctions

Question 13

In smooth muscle cells, Actin and Myosin bundles are incorporated into a _______ arrangement

Answer 13

Meshwork

Found throughout cytoplasm except in nuclear area

Question 14

What are the functions of Dense Bodies?

Answer 14

Anchor actin filaments to each other and to cell membrane

Communicate force of contraction to cytoskeleton and cell membrane

Question 15

Dense bodies contain:

Answer 15

alpha-actinin

Question 16

Dense bodies are interconnected by:

Answer 16

specific type of desmin

Question 17

Where are dense bodies found?

Answer 17

In cytoplasm and in the cell membrane

Question 18

True or False:

Smooth Muscle cells have t-tubules and an extensive SR

Answer 18

False

Smooth muscle cells do NOT have t-tubules or extensive SR

Question 19

Smooth muscle cells depend on extracellular ______ for contraction

Answer 19

Calcium

Question 20

In smooth muscle cells, pinocytotic vesicles:

Answer 20

may transport calcium ions from extracellular fluids to sarcoplasmic reticulum

Question 21

Caveolae and Lipid Rafts in Smooth muscle cells

Answer 21

Permanent depressions of the cell membrane that are involved in fluid and electrolyte transport

Question 22

Caveolae and lipid rafts are preceded by membrane lipid rafts composed of:

Answer 22

Cholesterol and Sphingolipids

Question 23

_______ binds to the cholesterol in the lipid rafts and initiates the formation of caveolae

Answer 23

Caveolin

Question 24

True or False:

Innervation of smooth muscle may either facilitate or inhibit contraction of the muscle cells.

Answer 24

True

Question 25

Types of smooth muscle neurotransmitter receptors

Answer 25

Adrenergic and muscarinic receptors - linked to G-proteins

Nicotinic cholinergic receptors - cation channel

Question 26

True or False:

Smooth muscle sheets of most major organs are highly innervated.

Answer 26

False

They are poorly innervated - excitation is spread through numerous gap junctions