Table 12-3: Comparison of Three Muscle Types

Smooth Muscles: Contrasted to Skeletal Muscle

• Homeostatic role– Control fluid– Sphincters

• Tonic contractions– Support tubes– Move products

• Slow contractions– Little fatigue– Low O2 use

Smooth Muscles: Contrasted to Skeletal Muscle

Figure 12-25a: Types of smooth muscle

• Stimulation– Electrically coupled– Hormones– Paracrines– Various receptors– Single Unit – Multiple unit

• Single tapered cells

• Longer actin & myosin

Smooth Muscles: Characteristics

Smooth Muscle Contraction: Mechanism

Figure 12-28: Smooth muscle contraction

Smooth Muscle Relaxation: Mechanism

Figure 12-29: Relaxation in smooth muscle

Cardiac Muscle: Contrasted to Skeletal

• Short branched fibers

• Single nucleus

• Intercalated discs

• Gap junctions

• Stimulation– Pacemaker– Autonomic

• Hormonal

Cardiac Muscle: Contrasted to Skeletal

Figure 14-7h: ANATOMY SUMMARY: The Heart

Action Potentials

• Smooth muscle cells are linked electrically via gap junctions so they can stimulate each other causing a wave like action potential

• This is also referred to as a FUNCTIONAL SYNCYTIUM