ch 13: blood, heart, and circulation

circulatory system

organ system that transports molecules and other substances rapidly over long distances, between tissues, organs, and cells

divisions of circulatory system

cardiovascular system

lymphatic system

cardiovascular system includes...

heart

vessels/vascular system

blood

heart

pump of variable rate and strength

vessels/vascular system

pipes of variable diameter

interconnected system

blood

fluid (connective tissue) of variable volume and viscosity

contains water, solutes, and cells

averages 5.5 L

composition of blood

hematocrit

hemoglobin

plasma

white blood cells

platelets

hematocrit

a rapid assessment of blood composition

the percent of blood volume that is composed of RBCs/erythrocytes

hemoglobin

in RBCs

carries O2 to tissues and CO2 away from tissues

plasma

the fluid portion of blood, includes water, ions, proteins, nutrients, hormones, wastes, etc.

white blood cells

leukocytes

for immunity

platelets

cell fragments for clotting

the heart is the muscular pump that...

propels the blood through the pulmonary (lung) circulation and systemic (other organs and tissues) circulation

muscular organs includes

cardiac muscle + endothelial cells

myocardium

muscular tissue of heart

each cardiac muscle cell contracts with a...

heart beat

what does pumping action of the heart create

[due to muscle contraction]

pressure to move blood quickly throughout the body

what separates the right and left sides of the heart

muscular septum

ventricle

lower chamber of the heart

pumps blood into arteries

what does RV pump

blood to the lungs via pulmonary arteries, pulmonary circulaion

what does LV pump

oxygenated blood to the other tissues via aorta, systemic circulation

aorta

artery by which blood exits LV for systemic circulation

interventricular septum

separates the two ventricles

atrium

upper chamber of the heart

receives venous blood

RA receives...

blood from systemic circulation via venae cavae

LA receives...

blood from pulmonary circulation via pulmonary veins

what separates atrium and ventricle

fibrous skeleton

pulmonary circulation

circuit through which partially oxygenated blood travels from the RV of the heart via pulmonary arteries to the lungs.

then, the blood picks up O2 from inspiration and releases CO2 for expiration

this oxygenated blood travels back to the LA of the heart and enters via pulmonary veins

systemic circulation

circuit through which oxygenated blood travels from the LV of the heart via aorta through the organ systems.

then, the blood delivers O2 from inspiration and picks up CO2 for expiration

this partially oxygenated blood travels back to the RA of the heart and enters via the superior vena cava and inferior vena cava

atrioventricular (AV) valves

tricuspid valve

bicuspid valve

papillary muscles

between atria and ventricles

tricuspid valve

3 flaps

between RA and ventricle

bicuspid (mitral) valve

2 flaps

between LA and ventricle

valve opens and closes due to pressure difference across it

i.e. pressure can push a valve open or force it closed

papillary muscles

limit valve movement to prevent backflow of blood intro atria

semilunar valves

pulmonary valve

aortic valve

pulmonary valve

between RV and pulmonary trunk (right and left pulmonary arteries)

aortic valve

between LV and aorta

the alternating contractions and relaxations of atria and ventricles last approx...

8 secs

systole

period of ventricular contraction and blood ejection from ventricles

approx 0.3 s

diastole

period of ventricular relaxation and blood filling ventricles from atria

approx 0.5 s

pressure

force exerted by blood due to heart contraction

mm Hg

blood flow

from region of higher pressure to region of lower pressure

volume/unit time such as L/min

systole sound

soft, low-pitched lub

AV valve closure

diastole sound

louder dub

SL valve closure

systole process

1. isovolumetric pressure: pressure in ventricles increase as ventricles begin contraction -> AV valves closed ('lub')

2. ejection of blood into aorta and pulmonary trunk occurs when ventricular pressure (120 mm Hg, systolic bp) exceeds aortic pressure so that semilunar valves open

stroke volume

amount of blood ejected into aorta and pulmonary trunk

around 2'3 of the blood in the ventricles

diastole process

3. isovolumetric relaxation: pressure in ventricles decreases, causing SL valves to close ('dub')

aortic pressure is 80 mm Hg (diastolic bp)

4. when pressure in ventricles falls below atrial pressure, AV valves open and there is a rapid filling of the ventricles (blood in atria -> ventricles)

5. atrial contraction delivers final amount of blood into ventricles just prior to 1st step occurring again

end-diastolic volume (EDV)

volume of blood in ventricles at end of diastole

pressure and volume changes where during the cardiac cycle

left ventricle

similar changes occur in the RV, but pressures are lower

depolarization in SA node causes

initiation of AP that depolarizes the rest of the cardiac cells

sinoatrial (SA) node

small group of cardiac muscle cells in RA

heart's pacemaker

cells depolarize spontaneously and quickly

excitation causes contraction

AP spreads through cells of atria via gap junctions, electrical synapses

atrioventricular (AV) node

carries APs from right atrium

APs -> ventricles via bundle of His

- slow conduction is AV node so ventricular contraction occurs after atrial contraction has ended

electrocardiogram (ECG, EKG)

detects electrical activity in the heart via electrodes on the surface of the skin

electrodes record current conducted through fluid around heart, due to simultaneous APs in myocardial cells

three distinct ECG waves are

P

QRS

T

P wave

results from spread of atrial depolarization

QRS wave

results from spread of depolarization into the ventricles

T wave

results from repolarization of ventricles

relationship between the electrocardiogram and APs

difference between currents at the left and right wrists AND

and action potential of a typical ventricular myocardial cell

closed loop

blood pumped from heart in arteries returns to the heart in veins

distribute blood to tissues to...

regulate blood pressure

blood vessels exists in

connective tissue, smooth muscle, and epithelial tissue

[capillaries have only epithelial]

arteries branch into...

arterioles, vessels between arteries and capillaries

capillaries are the...

smallest blood vessels

mediate exchange of substances with ISF

in every tissue except cornea

single layer of epithelium allows rapid exchange of substances

- gas exchange (O2, CO2)

- nutrient and waste exchange

- cell secretions

in capillaries, there is...

exchange of substances, such as nutrients and waste, between cells and vessels

capillaries merge to form...

venules, vessels between capillaries and veins

arteries

have strong, thick, elastic walls that resist flow

high pressure/low volume

veins

have weaker walls and wider lumen and fill more easily

low pressure/high volume

act as volume reservoirs (54% of total volume)

arterioles

blood vessels between arteries and capillaries

the greatest pressure drop is in...

the arterioles

arterioles serve as...

controllers of flow into capillary beds

vasoconstriction of arterioles

contraction of their smooth muscle layer to decrease vessel diameter

decreases blood flow

vasodilation of arterioles

relaxation of smooth muscle layer to increase vessel diameter

increases blood flow

veins travel process

capillaries -> venules -> veins -> heart

veins have the greatest...

total blood volume

can expand with greater blood volume

has low pressure but blood flows back to heart due to skeletal muscle pump (contraction) and the direction of flow is one-way due to venous valves in peripheral veins

venous flow is assisted by the

skeletal muscle pump mechanism working in combination with one-way venous valves

when muscles contract, veins are....

partially compressed -> diameter reduction, venous pressure increase, and increased volume of blood returning to the heart

coronary artery disease

insufficient blood flow (ischemia) to heart due to change in coronary arteries

can cause heart attack

primary cause: atherosclerosis in coronary arteries

risk factors: hypertension, stress, smoking, obesity, sedentary lifestyle, diabetes, high cholesterol

myocardial infarction

heart attack

atherosclerosis

thickening of arterial wall with plaques that include cholesterol and fat deposits

coronary arteries are...

arteries that nourish the heart