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
|
|
Term
| Are there t-tubules in smooth muscle? |
|
Definition
|
|
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
|
|
Term
| What are the thin filaments of smooth muscle made of? |
|
Definition
|
|
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
|
|
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
|
|
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
|
|
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
|
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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