Topic 7 Muscular System: Smooth Muscle

Question 1

• Mainly involuntary, contains one central nucleus, lacks striation, stimulated by the autonomic nervous system (lining of bladder, uterus, digestive tract, blood vessel walls) are slow to contract
• Smooth muscle does not rely on sarcomere organization: intermediate filaments are attached to dense bodies spread throughout the cell

Answer 1

Note

Question 2

• Thick and thin filaments are attached to intermediate filaments, which contract -> intermediate filaments pull dense bodies together -> smooth muscle length shrinks

Answer 2

Contraction occurs as follows

Question 3

• Single-unit

- Multi-unit

Answer 3

Types of Smooth Muscle

Question 4

• visceral, connected by gap junctions, contract as a single unit (found in stomach, uterus, and urinary bladder)

Answer 4

Single-unit

Question 5

• each fiber is directly attached to the neuron; can contract independently (found in iris and bronchioles)

Answer 5

Multi-unit

Question 6

• In addition to the neuron response, smooth muscles can respond to hormones, changes in pH, O2, CO2 levels, temperature, and ion concentration
• Smooth muscle does not have T-tubules, striations, troponin, or tropomyosin. It instead uses myosin light change kinase to overcome lack of troponin

Answer 6

Note