Physiology Lecture 9 Q-Bank (Smooth Muscle Structure, Contraction, And Relationships)
6
What are multiunit smooth muscles? What are single unit smooth muscles? In multiunit smooth muscle, each smooth muscle acts as its own. In single smooth muscle, smooth muscle work as one through gap junctions What does gap junction allow? Only 1 smooth muscle needs to be stimulated, and all other muscles respond as one What happens when smooth muscle contract? They change volume Describe the 5 ways Ca 2+ enters the smooth muscle cell Ca 2+ leakage channel DHP receptor – Ca 2+ voltage gated channel Ryanodine (RyR) receptors – ligand gated channel for calcium P2X receptors – ligand gated Ca 2+ channel **G coupled receptor – produces IP3 Of the 5 ways calcium enters the SMOOTH MUSCLE, which channel is the primary source of Ca 2+ for contraction?
description
Physio, USMLE, prep questions
Transcript of Physiology Lecture 9 Q-Bank (Smooth Muscle Structure, Contraction, And Relationships)
What are multiunit smooth muscles? What are single unit smooth muscles?
In multiunit smooth muscle, each smooth muscle acts as its own.
In single smooth muscle, smooth muscle work as one through gap junctions
What does gap junction allow?
Only 1 smooth muscle needs to be stimulated, and all other muscles respond as one
What happens when smooth muscle contract?
They change volume
Describe the 5 ways Ca2+ enters the smooth muscle cell
Ca2+ leakage channelDHP receptor Ca2+ voltage gated channelRyanodine (RyR) receptors ligand gated channel for calciumP2X receptors ligand gated Ca2+ channel**G coupled receptor produces IP3
Of the 5 ways calcium enters the SMOOTH MUSCLE, which channel is the primary source of Ca2+ for contraction?
DHP receptors
What is the ligand for purinergic receptor P2X?
ATP
What is the ligand for Ryanodine receptors?
Ca2+
How does G protein coupled receptors work to release Ca2+?
Trans-membrane receptor binds agonist (Norepinephrine or Epinephrine) portion of G protein causes PHOSPHOLIPASE C to act on PIP2PIP2 splits into IP3 and DAGSecond messenger IP3 cause Ca2+ is released from SR
How is calcium removed from the SR (4 ways)?
Cell membrane Ca2+ ATPaseSR membrane Ca2+ ATPaseNa+/Ca2+ exchanger 3 sodium in, 1 calcium outNa+/K+ ATPase pump 3 sodium out, 2 potassium in
What is CALMODULIN?
Protein that binds to calcium in order to activate MLCK
What is MYOSIN LIGHT CHAIN KINASE (MLCK)?
Protein that phosphorylate myosin light chain in order to prep myosin for contraction
What is MYOSIN LIGHT CHAIN Phosphatase (MLCP)?
Protein that dephosphorylate myosin light chain in order to relax myosin light chain
Describe how smooth muscle contract.
Ca2+ enters the cell (any of the 4 modes)Ca2+ binds to CALMODULIN (CAM)Ca2+-CALMODULIN complex binds to MLCK (myosin light chain kinase) on myosinActivation of MLCK takes phosphate from ATP, and phosphorylates of myosin light chain.Once phosphorylation is done cross bridge is formedATP on myosin head is hydrolyzed to ADP+PiMyosin cross bridgesADP+Pi is removed from the ATP binding sitePower Stoke (Shift Occurs)ATP binds to ATP binding site on myosinActin and Myosin detached
When does the smooth muscle stop to contract?
When intracellular Ca2+ levels drop
What is Latch State?
Slow contraction of myosin without the phosphorylation of the myosin light chain or intracellular Ca2+.
What are cross bridges called in Latch State?
Latch Bridges
How is the force-velocity curve for smooth muscle compared to skeletal muscle?
Same isometric point, but lower Vmax (y intercept) since smooth muscle have very low myosin ATPase activity.
The following questions are a comparison between Skeletal and Smooth muscle.
Do they have striations?
Skeletal: Yes Smooth: No
Nucleus?
Skeletal: Multinucleated Smooth: Mononucleated
PNS Branch?
Skeletal: Somatic NS Smooth: Autonomic NS
Type of Control?
Skeletal: Voluntary Smooth: Involuntary
Thick or thin filament?
Skeletal: Yes Smooth: Yes
Sarcomere?
Skeletal: Yes Smooth: No
Sarcomere Reticulum?
Skeletal: Depends on it for release of Ca2+ Smooth: Somewhat depended
Gap junction between cells?
Skeletal: No Smooth: Yes (single unit); No (multiunit)
Source of calcium?
Skeletal: Sarcoplasmic Reticulum Smooth: Sarcoplasmic Reticulum & extracellular
Site of calcium regulation?
Skeletal: Troponin Smooth: myosin
Speed of contraction?Skeletal: Fast or slow Smooth: very slow
Spontaneous production of action potential by pacemaker?
Skeletal: No Smooth: Yes (single unit); No (multiunit)
Effect of nerve stimulation?
Skeletal: Excitatory Smooth: Excitatory or Inhibition
Tone (low levels of maintained tension in absence of stimuli)?
Skeletal: No Smooth: Yes (single unit); No (multiunit)
Physiological effects of hormones on excitability and contraction?
Skeletal: No Smooth: Yes
Transverse tubules?
Skeletal: Yes Smooth: No
Stretch of cell produces contraction?
Skeletal: No Smooth: Yes (single unit); No (multiunit)
MEP (motor end plate) or Varicosities?
Skeletal: Motor end Plate Smooth: Varicosities
Myosin end-polarized or side-polarized?
Skeletal: end-polarized Smooth: side-polarized
