Human Phys 2.9 Flashcards
(27 cards)
What do smooth muscles lack?
Striations
Do smooth muscles have actin and myosin?
Yes, but they are not arranged in sarcomeres
Motility
To propel chyme down the GI tract (Phasic)
Tension
To maintain appropriate vascular diameter in blood vessels (tonic)
What are the types of smooth muscles?
Unitary/visceral/single unit
Multi unit
Combination
What are single unit smooth muscles linked by?
Gap junctions
What are single unit smooth muscles present in?
GI tract
Bladder
Uterus
Ureter
What are single unit smooth muscles characterized by?
Spontaneous pacemaker activity (slow waves) (Phasic contractions)
Are multi unit smooth muscles linked by gap junctions?
No
What are multiunit smooth muscles present in?
Iris
Ciliary muscles of the lens
Vas deferens
What are characteristics in multiunit smooth muscles?
Each muscle fiber behaves as a separate motor unit
Little or no coupling between cells
Densely innervated by the ANS
What type of contractions do multiunit smooth muscles do?
Tonic
What is a combination of both types of smooth muscles present in?
Vascular smooth muscle
What do smooth muscles not contain?
Troponin complex
What are dense bodies in smooth muscles?
Behave like Z disc in the skeletal muscles
Have much of there length can smooth muscles contract?
80% (skeletal can do 30%)
What is the myosin ATPase activity in the smooth muscles compared to the skeletal muscles?
1/10 compared to 1/300 is required ti maintain the same tension
Why is myosin cross bridge much slower in smooth muscles compared to skeletal muscles?
Because less energy is used
What does smooth muscle require more time for?
To contract and relax (slow onset of contraction)
What is the maximum force of contraction in smooth muscle compared to skeletal muscle?
Much higher (4-6 kg/cm2)
How can smooth muscles maintain prolonged tonic contractions, for hours using minimal energy?
Via the latch mechanism
Stress relaxation and reverse stress relaxation
Allows hollow organs to maintain constant luminal pressure despite large changes in volume
What is poorly developed in the smooth muscle?
Sarcoplasmic reticulum
What is used in smooth muscles instead of troponin?
Calmodulin
