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Physiology Exam 3

Active Hyperemia the increase in blood flow occurring in response to an increase in metabolic activity
Reactive Hyperemia Increase in blood flow in response to a previous reduction in blood flow
Myogenic response Change in vascular resistance in response to stretch of blood vessels in the absence of external factors
Compliance Measure of how the pressure of a vessel will change with a change in volume
Calmodulin Cytosolic calcium-binding protein; modulates the activity of intra-cellular proteins
MLCK (Myosin light chain kinase) enzyme involved in excitation-contraction coupling in smooth muscle; phosphorylates myosin crossbridges
5 events that provide excitatory input to smooth muscle *Spontaneous excitation via pacemaker regions *Neurotransmitters (Ach) on Muscarinic receptors *Hormones *Changes in local chemicals (O2, CO2, ions, acids) *Mechanical stretch (gut after eating)
Types of smooth muscle Single unit- Connected via gap junctions, innervated by very few autonomic neurons, mostly found in GI tract, Uterus Multi unit - not connected to adjacent smooth muscle cells, innervated by more neurons, found in Respiratory airways, large arteries
Latch Bridge Mechanism When contraction is initiated, myosin cross bridge moves and locks into position without energy requirement, significantly reducing the energy requirement in tissues that utilize smooth muscle
Major difference between Systemic vessels and Pulmonary vessels Systemic - High pressure (120/80mmHg), very low influence of surrounding tissues on blood flow except "secondary" muscle pump Pulmonary - Low pressure (25/15mmHg), High alveolar pressures my actually collapse capillaries
Common vasodilators of blood vessels *Nitric oxide (NO) powerful vasodilator *Bradykinin stimulates NO release *Histamine released during inflammation and allergic reactions stimulates bradykinin, stimulating NO release *Heat *Cold
Capillary characteristics *One cell thick *slow blood velocity, allows for optimal nutrient, gas, and waste exchange *ONLY site for exchange of these materials
Characteristics of Venules and veins *Not as elastic as arterioles *low resistance conduit back to heart *2/3 of blood volume is here at any given time act as resovoir *Have 1 way valves back to heart *Increased venous return to heart- increase in sympathetic drive,& skeletal muscle pump
MAP (Mean Arterial Pressure) Average aortic pressure occurring during cardiac cycle
Created by: claritamaria