4 - Smooth Muscle Flashcards
All smooth muscles lack the […] banding pattern found in cardiac and skeletal fibers.
Striated
The nerves to all smooth muscle are derived from the […].
Autonomic nervous system (ANS)
General description of a smooth muscle cell.
Spindle-shaped, sinle nucleus, smaller/shorter than skeletal muscle
True/False: Unlike skeletal muscle smooth muscle can divide.
True
Smooth muscle does have tropomyosin but lacks […].
Troponin
Why is smooth muscle not striated?
Thick and thin filaments are not organized into myofibrils therefore there are no aligned sarcomeres.
Anchor the thin (actin) filaments to the cell’s plasma membrane or to structures in the cytoplasm.
Dense bodies (i.e. analogous to Z discs)
Smooth muscle type, an entire group of muscle fibers responds to stimulation as a single unit (i.e. electrical and contractile activity is synchronous in all cells)
Single-unit (i.e. unitary or visceral); occurs because all cells are connected to adjacent cells via gap junctions
A common method single-unit smooth muscle contraction can be induced.
Stretching (i.e. smooth muscles of the stomach and intestines)
Smooth muscle type, contain few or no gap junctions, and each cell thus responds independently
Multi-unit
Method of single-unit (i.e. smooth muscle type) regulation.
Regulated via frequency pacemaker fires
Method of multi-unit (i.e. smooth muscle) contraction.
Number of fibers activated and frequency of activation
The following are examples of what type of smooth muscle? Eyes, large airways, larger arteries, and attached to the hairs in the skin.
Multi-unit
Forms the head of a myosin molecule.
Two light chains plus one heavy chain
Smooth muscle cells lack […]. therefore tropomyosin never blocks myosin’s access to actin.
Troponin
How is cross bridge binding regulated in smooth muscle?
Regulation of calicum activation via myosin light chain kinase
Methods by which calcium ion concentration in the cell’s cytoplasm is increased.
Opening membrane channels (i.e. influx of extracellular calcium) or stimulation of the cell;s sarcoplasmic reticulum (i.e. released stored calcium)
Protein that calcium binds to within the cell to activate the myosin light chain kinase.
Calmodulin
Function of myosin light chain kinase.
Phosphorylates one of the light chains of each myosin head.
In order to relax smooth muscle myosin must be […] to remove it from actin.
Dephosphorylated
How is calcium removed from smooth muscle back to the ECF or sarcoplasmic reticulum?
Via ATP-requiring pump
Enzyme, always active in smooth muscle, dephosphorylates myosin light chain.
Myosin light chain phosphatase (i.e. when outpaces MLCK muscle relaxes)
The rate of ATP splitting and cross bridge cycling during contraction in smooth muscle are [>/=] skeletal muscle.
< (i.e. less than or slower)
The velocity of smooth muscle shortening is […] than skeletal muscle.
Slower
True/False: Smooth muscle and skeletal muscle both undergo fatigue during long periods of activity.
False; smooth muscle does not
State of a smooth muscle, can last for hours, occurs when a full contraction occurs and is maintained near full level despite declines in levels of energy consumption.
Latch state
Inputs to smooth muscle that increase the cell’s cytosolic calcium levels and therefore regulate contractions.
Transmitters via ANS, hormones, local factors (i.e. acidity, osmolarity, etc.), stretch of the fiber, spontaneous electrical activity in the fiber’s plasma membrane.
True/False: A membrane potential change is required for a smooth muscle cell to contract.
False
Due to some smooth muscle cells producing […] they are able to generate an AP in the absence of neural, hormonal, or local inputs.
Pacemaker potentials (i.e. resting membrane potential depolarizes slowly to threshold)
[…] are produced in smooth muscles with pacemakers that have a membrane potentail that drifts up and down (i.e. possibly due to regular variation in ion flux across the membrane)
Slow waves
Slow waves are typically found in […] smooth muscle therefore an AP causes the entire group of cells to contract.
Single-unit
Smooth muscles […] have a motor end-plate region.
Do not
Swollen regions found on the branches of postganglionic neurons, filled with transmitter contain vesicles.
Varicosity
True/False: A given transmitter can increase tension in one smooth muscle while decreasing tension in another.
True
Hormones that have receptors on smooth muscle.
Epinephrine, cholecytokini, angiotensin II, vasopressin
