muscular system 2-smooth and cardiac muscle

Question 1

what are the smooth muscle structures and characteristics

Answer 1

 Not striated, fibers smaller than those in
skeletal muscle

 Spindle-shaped; single, central nucleus

 More actin than myosin

 Dense bodies instead of Z disks as in skeletal muscle; have noncontractile intermediate filaments

 Ca2+ required to initiate contractions

Question 2

what are the functional properties of smooth muscles?

Answer 2

 Some visceral muscle exhibits autorhythmic contractions

 Tends to contract in response to sudden
stretch but not to slow increase in length

 Exhibits relatively constant tension: smooth muscle tone

 Amplitude of contraction remains constant although muscle length varies

Question 3

Regulation of smooth muscle?

Answer 3

 Innervated by autonomic nervous system

 Neurotransmitters are acetylcholine and norepinephrine

 Hormones important are epinephrine and oxytocin

 Receptors present on plasma membrane;
which neurotransmitters or hormones bind determines response

Question 4

Cardiac muscle:

Answer 4

 Found only in heart

 Striated

 Each cell usually has one nucleus

 Has intercalated disks and gap junctions

 Autorhythmic cells

 Action potentials of longer duration and longer refractory period

 Ca2+ regulates contraction