Circulation (Chapters 24)
I.
The circulatory system's functions: TRANSPORT, REGULATE, AND PROTECT
A. Moves body fluids- 5 liters of blood
per minute in man
B. Helps maintain homeostasis
1.
1.
By
delivering oxygen, nutrient, and other materials to each
body cell
2. Remove metabolic wastes
3. White blood cells protect the body from
diseases
4.
45% of total blood vol. is formed elements (rbcs, wbcs,
and
platelets)
C. Closed circ.
system - blood completely contained in a system of vessels- arteries, veins,
capillaries
1. Blood can be shunted to specific areas where
needed
2. Blood pressure - high, arterial system-
pressure reservoir
3. More efficient, each tissue has many capillaries
II. Heart 612
A. 2-loop system -
Blood is first pumped to the lungs, then back to the heart where it is
pump again
B.
2 atria, 2 ventricles
1.
Pulmonary circ (right). - transports deoxygenated blood through the
right half of the heart-to the lungs,
then back to left side of the heart- pumps blood at lower pressure
2. Systemic circ.- moves oxygenated blood through the left half of the heart and to the body,
then returned to the right side of the heart
3. Two pairs of one-way valves:
a.
Atrioventricular valves:
right-- tricuspid
and
left-- mitral (bicuspid)
b.
Semilunar valves allow blood to leave the ventricles and enter the
pulmonary artery
and
systemic circulation (the aorta)
4. Cardiac cycle- diastole-relaxation;
systole-contraction
At
rest, each cardiac cycle lasts - 0.8 sec of which systole lasts 0.3 sec. and
diastole 0.5 sec
C.
The electrical activity of the heart -
1.
Long action potential and long refractory period of myocardial
cells-
prevents
the myocardium from being stimulated again until after it relaxes.
2.
All of the cells in the vent. are normally in
a refractory period at the same time.
3.
The electrical
impulse begins in the AS node, with
spontaneous electrical activities
a.
The SA cells have the
fastest rate of spontaneous
diastolic
depolarization. The impulse spreads
through both atria by electrical conduction.
b. AS node depolarizes
to threshold before other regions
c. AS node has calcium
diffusing through slow and
fast calcium channels
d.
EKG: p, qrs, t waves;
measure the voltage between 2 points
on
the surface of the body caused by the electrical activity of the heart
i. p wave - caused by depolarization of the
atria
Between p and q = a nonconductive phase
of
AV node, atrial systole completion occurs
ii.
qrs wave - caused
by depolarization of the
ventricle;
occur at the beginning of systole, increase
intraventricular pressure- causes AV valves
to close
-
1st heart sound produced immediately after the qrs wave
iii.
t wave - produced by polarization of the
ventricles;
ventricles relax at the beginning of
diastole,
decrease in intraventricular pressure
causes semilunar valves
to
close, after t wave - 2nd heart sound
Between s & t = refractory state of vent. myocardium.
D.
Intrinsic control-- Franks
Starling Law
E. Extrinsic control- Hormonal and neuronal control
II. Pressure, resistance, and flow in
vascular systems
A. Blood pressure regulated by C.O., blood
vol., P.R. 617
B.
Neural and renal mechanisms of blood volumes/pressure
C.
Poiseuille equation 619
and the exit vessels/ resistance to flow
D.
Blood flow in the systemic vasculature 624
velocity, surface area, and pressure
E.
Fluid exchange across
mammalian systemic capillaries- 625
hydrostatic and osmotic
pressure
III. Open vs. closed circulation
A. Circulation in mammals, birds, and fish 622-627
Pulmonary vs. systemic circulation
Cardiac output and vascular resistance during exercise
B. Invertebrates with open
circulatory system