Smooth Muscle
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Created by:
EasyMedPhys on April 3, 2011
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13 terms
Terms | Definitions |
|---|---|
 tonic contraction | one of the types of SM contraction - sphincters |
| phasic contraction | one of the types of SM contraction - GI tract (phasic contractions are rhythmic) |
| dense bodies | Actin filaments of contractile units are attached to dense bodies. They appear to serve as anchors from which the thin filaments can exert force. |
| stretch-relaxation response | if smooth muscle is quickly stretched, it contracts, but over time, it gradually relasxes adjusting to a new length. |
| stretch-relaxation | ability of smooth muscle to be stretched and then relax maintaining constant pressure (ex: bladder filling with urine) |
| myosin phosphorylation | Myosin can't bind to actin unless it is phosphorylated! (begins contraction) Calmodulin > (Calcium) > Calcium-Calmodulin Inactive myosin kinase > (Calcium-Calmodulin) > Active myosin kinase Inactive myosin > (Active myosin kinase) > Phosphorylated myosin! |
| how does Ca+2 enter the cell | Smooth muscle doesn't have t-tubules and has small sarcoplasmic reticulum. Calcium enters from the ECF bia Ca+2 channels. |
| calcium blockers | 1. Verapamil 2. Nifedipine 3. Norvasc antagonists to dihydropyradines -> block receptors *last line of protection |
| unitary smooth muscle | function independently from eachother each smooth muscle innervated independently neurogenic (from the neuron) no AP in this type of muscle found in vessels, airways, eye, erector pili |
| single unit smooth muscle | most abundant "visceral" contracts as a single unit electrically linked by gap junctions forms functional synctium self excitable rather than requiring nervous stimulation pacemaker cells can depolarize on their own do not have resting membrane potential myogenic (from the muscle) innervated - metabotrophic receptors respond to Ca from 2nd messenger systems symp and parasymp don't intitiate contraction, but rate and force |
| spontaneous depolarization | two types: pacemaker potential (reproductive, urinary tract) slow wave potential (only found in gut, peristalisis) |
| smooth muscle innervation | Norepi and ACh can be excitatory or inhibitory. They are usually antagonistic to eachother and is the case for multiunit smooth muscle. Can be Norepi, ACh, oxytocin, serotonin, angiotensin, histamine that alter Ca+2 levels. |
| Ca+2 channels | 2 categories: V sensitive (dihydropyradine receptors) Receptor mediated (g-proteins) |
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