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Week 9
Lecture 3
31
Anatomy
Undergraduate 2
10/30/2014

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Cards

Term
Where is smooth muscle located?
Definition
-walls of different organs
ex:
-digestive tract
-urinary tract
-respiratory tract
-reproductive tract
Term
How is smooth muscle organized?
Definition
sheets of muscle cells split into two layers:
1. longitudinal layer
2. circular layer
Term
What is the outcome of having two layers in smooth muscle?
Definition
you can squeeze and push material through a tube
Term
What is smooth muscle innervated by?
Definition
the autonomic nervous system
Term
What is different about the innervation of smooth muscle vs. skeletal muscle?
Definition
the nerve endings are called bulbous varicosities and they have a poorly organized neuromuscular junction
Term
What do the cells of smooth muscle look like?
Definition
-small, spindle-shaped
-surrounded by connective tissue
-joined together by gap junctions
Term
What is the purpose of gap junctions in smooth muscle?
Definition
allows the cells to communicate with each other
Term
What are the characteristics of the sarcoplasmic reticulum in smooth muscle?
Definition
-less well developed that that of skeletal muscles
-touches the plasma membrane
Term
What is a defining characteristic of the plasma membrane of smooth muscle?
Definition
has cavities called caveoli
Term
What is the purpose of caveoli?
Definition
stores calcium
Term
Are there t-tubules in smooth muscle?
Definition
no
Term
What is the ratio of thick to thin filaments in smooth muscle?
Definition
1:16 (much more than skeletal muscles)
Term
What are the thick filaments of smooth muscle made of?
Definition
mysosin
Term
What are the thin filaments of smooth muscle made of?
Definition
actin and tropomyosin
Term
What are the steps of smooth muscle contraction?
Definition
-neurotransmitter is released from bulbous varicosity
-sarcoplasmic reticulum receives stimulus
-Ca2+ enters cytoplasm from SR and caveoli
-contraction then occurs
Term
How does the action potential spread across smooth muscle sheets?
Definition
gap junctions
Term
What is the mechanism of smooth muscle contraction?
Definition
1. initiated by Ca2+ entry into cytoplasm
2. Ca2+ binds to calmodulin
3. calmodulin activates kinase
4. kinase uses ATP to phosphoralate the myosin head
5. cross bridges form
6. contraction occurs
Term
What are the two types of smooth muscle?
Definition
-single unit
-multi unit
Term
What are characteristics of single unit smooth muscle?
Definition
cells contract as a unit; contractions are rhythmical; gap junctions allow current flow from cell to cell
Term
What are characteristics of multi unit smooth muscle?
Definition
muscle fibers that are independent of one another; rare gap junctions and rare spontaneous action potentials; respond to hormones and have ANS innervation
Term
Where can single unit smooth muscle typically be found?
Definition
organs
Term
Where can multi unit smooth muscle typically be found?
Definition
can be found in muscles that regulate pupil size, arrector pili, large airways, and larger arteries
Term
How is smooth muscle regulated?
Definition
-neurotransmitters
-receptors
-stretching
-hormones and local factors
Term
What are the neurotransmitters that regulate smooth muscle?
Definition
acetlycholine and norepinephrine
Term
What are the receptors that regulate smooth muscle?
Definition
inhibitory receptors or excitatory receptors
Term
How does stretching influence smooth muscle regulation?
Definition
there is more vigorous contraction if stretched
Term
What are the hormones and local factors that regulate smooth muscle?
Definition
stimulatory and inhibitory
Term
What are some unique features of smooth muscle?
Definition
-length tension
-hyperplasia
-secretion
Term
What is length tension in regards to smooth muscle?
Definition
when you stretch smooth muscle, it contracts more vigorously
Term
What is hyperplasia?
Definition
smooth muscle can grow or increase its size; especially important during pregnancy
Term
What is secretion in regards to smooth muscle?
Definition
secrete the elastin and collagen of connective tissue
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