Smooth Muscle

Question 1

Basic Smooth Muscle Anatomy

Answer 1

• No striations
• Uninucleated
• Small
• Spindle shaped
• No motor end-plate

Question 2

2 Types of Smooth Muscle Tissue

Answer 2

• Single-unit

- Multi-unit

Question 3

Single-Unit

Answer 3

• “visceral Smooth”
• Forms walls of internal organs
• joined by gap junctions
• contain internal pacemakers
• used for long contractions

Question 4

Multi-Unit

Answer 4

• No gap junctions
• No internal pacemakers
• Used for Fine muscle movement

Question 5

Contractile Element Structure - Actin

Answer 5

• longer
• high actin:myosin ratio (10-15:1)
• filaments are crosshatched

Question 6

Contractile Element Structure - Myosin

Answer 6

• longer

- myosin light chain (regulatory protein in myosin head)

Question 7

Contractile Element Structure - Arrangement

Answer 7

• arranged in diagonal bundles
• fibers become globular when contracted
  “Like wringing a wet towel”

Question 8

Contractile Element Structure - Sarcoplasmic Reticulum

Answer 8

• less overall than skeletal Muscle
• IP3-receptor channel (no t-tubules)
• most CA comes from extracellular fluid)

Question 9

Contractile Element Structure - Dense Bodies

Answer 9

• The “Z-lines” in Smooth Muscle

- Where actin attaches

Question 10

Smooth Muscle Potentials

Answer 10

Depolarization caused by Ca entry