Vasculature, Smooth Muscle, Blood Flow and Pressure Flashcards
What do the arteries and veins carry in the systemic system vs the pulmonary system
Systemic circulation
-arteries and arterioles transport oxygenated blood
-venules and veins transport deoxygenated blood
Pulmonary Circulation
-Arteries and arterioles transport deoxygenated blood
-Venules and veins transport oxygenated blood
What are the layers of the blood vessels?
Tunica externa - outer layer of CT
Tunica media - middle layer of smooth muscle
Tunica interna - layer of elastin, basement membrane, innermost simple squamous endothelium
What does microcirculation refer to?
Arterioles, capillaries and venules
What are elastic arteries?
-Aorta and other large arteries
-Numerous layers of elastin fibers that expand when the pressure of the blood rises during ventricular systole and recoil when ventricles relax
What are muscular arteries?
-Arterioles
-Much less elastic and have a thick layer of smooth muscle which regulates the diameter of the lumen
What are capillaries?
-Smallest blood vessel 5-10µm in diameter
-Single layer of endothelium and a basement membrane
-Permits exchange of nutrients and wastes between blood and tissue fluid
What assists in blood flow to the heart?
-1 way valves in veins
-Skeletal muscle pump and contraction of diaphragm assist in vein return
Where is smooth muscle found and what are the types?
-Found in walls of hollow organs and tubes (arteries and veins)
-vascular. gastrointestinal, urinary, repiratory, reproductive, ocular
What is smooth muscle made of?
-Does not contain sarcomeres (not striated) -
-Contains greater content of actin than myosin (ratio of 16:1)
-Long thin (actin) filaments attach to cytoplasmic structures - dense bodies
How does smooth muscle contract?
-dependent mostly on inward diffusion of extracellular Ca2+ through voltage-gated Ca2+ channels
-opening of Ca2+ channels is graded by amount of depolarization
-force of smooth muscke contraction is graded according to conc of Ca2+ in cell
-degree of opening of Ca2+ channels determines the strength of contraction
Does smooth muscle have Troponin C?
No troponin C is not expressed in smooth muscle cells instead Ca2+ binds with calmodulin
What happens in smooth muscle contraction?
-Ca2+/ calmodulin complex joins with and activates myosin light chain kinase (MLCK)
-MLCK phosphorylates light chains in the myosin head - enhances myosin ATPase activity driving contraction
-entire surface of thick filament covered with myosin heads to allow actin to slide along myosin for greater distances, greater degree of contraction
When and how does muscle relaxation occur?
-Relaxation occurs when Ca2+ conc decreases. Ca2+ ATPases pumps Ca2+ out of cytoplasm
-Ca2+ dissociates from calmodulin and MLCK inactivates
-Myosin heads become dephosphorylated (myosin phosphatase), myosin ATPase activity decreases and slow relaxation occurs
Why is relaxation of smooth muscle slow?
Because dephosphorylated myosin remains attached to actin for a period of time, latch state
What is the generation of action potentials and opening of Ca2+ channels in vascular smooth muscle regulated by?
Autonomic nerves
-mainly sympathetic nerves
Look at comparisons between skeletal, smooth and cardiac muscle
Resistance to blood flow relationship?
-Rate of blood flow is inversely proportional to resistance - Ohms law
-The resistance to blood flow depends on the length and radius of blood vessels and viscosity of the blood
What are major regulators of blood flow?
-Mean arterial pressure
-Blood vessel diameter
-Blood viscosity (haematocrit)
What is the driving force for blood flow through the systemic circulation?
Pressure causes by left ventricular contraction
Where is stroke volume ejected and what happens?
Stroke volume is ejected into the aorta
-the elastic wall of aorta and downstream arteries expand
-pressure in aorta increases to almost that of the ventricle- 120mmHg (systolic bp)
What is the Mean arterial pressure?
-As arterial pressure is pulsatile, MAP is calculated to determine average arterial pressure
MAP = diastolic pressure + 1/3 (systolic-diastolic pressure)
Why is the value of MAP closer to diastolic pressure?
Because diastole lasts twice as long as systole
What is pulse pressure?
-Each left ventricular contraction creates a pulse of systolic pressure as blood is ejected into the arteries
-This pulse or pressure waves is transmitted through the elastic walls of large arteries
-Can be detected by palpitation of radial artery in wrist
Pulse pressure = systolic pressure - diastolic pressure
What increases systolic pressure
The greater the cardiac output, the greater the volume of blood ejected into the arteries (stroke volume), the greater the systolic pressure
