Lecture 17: Cardiac And Smooth Muscle Tissue

Question 1

Describe the 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

Describe the cardiac muscle T-tubule system

Answer 2

• Not as extensive as in skeletal muscle
• Each T-tubule interacts with one cisterna (rather than two as in skeletal muscle)
• • Forms a diad rather than a triad.
• • Diads are located at the level of the Z-lines.

Question 3

Describe the composition of intercalated discs in cardiac muscle tissue

Answer 3

• Macula adherentes (desmosomes)
• • Link intermediate filaments (desmin) of adjoining cardiac muscle cells
• • Part of transverse component
• Fascia adherentes
• • Anchor actin filaments of sarcomeres
• • Part of transverse component
• Gap junctions:
• • Part of longitudinal component
• See Slides 6-9

Question 4

What are ANPs?

Answer 4

Atrial Natriuretic Peptides:

• Secreted by cardiac muscle cells in atria
• Regulate fluid electrolyte balance
• Relax vascular smooth muscle:
• • Reduces blood volume and pressure
• Stored as prohormone in secretory vesicles
• Release is stimulated by atrial stretch.
• • Results in cleavage of prohormone

Question 5

Incomplete

Answer 5

Resume at slide 11