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Ch. 34.1-34.4: Animal Circulation (Cardiac cycle (Atrial and ventricular…
Ch. 34.1-34.4: Animal Circulation
Circulatory systems
Open circulatory system
Heart contraction pumps hemolymph through circulatory vessels into sinuses in which nutrient exchange occurs
Body movements squeeze sinuses to help circulate hemolymph
present in arthropods and some molluscs
Heart relaxation draws hemolymph back in
The circulatory fluid is called hemolymph which is also interstitial fluid
Advantage
lower hydrostatic pressures make them less energetically costly
Closed circulatory sysetem
Present in annelids, many cephalopod molluscs, and all vertebrates
One or more hearts pumps blood into large vessels, this branches into smaller lines that infiltrate the organs and tissues
Circulatory fluid is blood
Circulatory fluid is confined and distinct from interstitial fluid
Chemical exchange occurs between blood and interstitial fluid and between interstitial fluid and body cells
Advantage
high blood pressure enables effective oxygen and nutrients in large, active animals
3 components
Heart (muscular pump), a set of interconnecting vessels, circulatory fluid
Route of blood flow through mammalian heart and body
Right ventricle pumps the blood to the lungs through the pulmonary arteries
Blood in capillary beds loads oxygen and unloads carbon dioxide (in lungs)
(Oxygen-rich) blood returns to left atrium through the pulmonary veins
(Oxygen-rich) blood flows into left ventricle
Left ventricle pups (oxygen-rich) blood to body through aorta
In capillaries there is a net diffusion of oxygen into tissues and carbon dioxide into blood
Oxygen-poor blood returns to heart through vena cava
Vena cava empty (oxygen-poor) blood into right atrium
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Cardiac cycle
Atrial and ventricular diastole
Relaxation phase: blood returns from large veins flows into atria and then into ventricles through AV valves
Relaxed, relaxed: blood flows in
Atrial systole and ventricular diastole
Short period of atrial contraction then forces all blood left into atria into ventricles
Atria contract, ventricle relaxed: blood forced from atria to ventricle
one complete sequence of pumping and filling of the heart
Ventricular and atrial diastole
Within the remainder of the cycle, ventricular contraction pumps blood into large arteries through the semilunar valves
Atria relax, ventricle contract: blood forced from ventricle into arteries
Generation and maintenance of heart beats
Terms
Atrioventricular node
signals are delayed at this point in the cardiac cycle
Apex
tip of the heart found at the left ventricle
Purkinje fibers
carry the contraction impulse from both the left and right bundle to myocardium of ventricles
Ventricles
chambers that pump blood out of the heart
Pacemaker cells
set rate and timing of contraction for all cardiac cells
creates electrical impulses that spread repidly within heart tissue
auto-rhythmic (repeatedly contract and relax without signal fro nervous system
regulated by physiological cues and also influenced by hormones and temperature (fight or flight response)
Electrocardiogram (ECG/EKG)
displays a graph of current against time showing the stages in the cardiac cycle
Electrical impulse spreads to walls of atria which causes it to contract in unison. During atrial contraction, the electrical impulses reach the AV node, that causes a delay in electrical impulse for 0.1 seconds. The delay allows atria to empty completely before ventricles contract. After the delay ends, the electrical impulse spreads to heart apex, then spreads to ventricles which causes them to contract in unison
Structures of arteries, capillaries, and veins
Capillaries
miscroscopic vessels that form networks (capillary beds)
thin walls allow diffusion of chemicals between blood and interstitial fluid
Endothelim (1 layer) and basal lamiina; very thin walls that are best for diffusion
infiltarted tissues passing within a few cell diameters of every cell in the body
substantial resistance to blood flow
Veins
carry blood toward the heart
Endothelium and thick layer of smooth muscle and thin layer of connective tissue
Contains valves to maintain unidirectional blood flow (can occur with low blood pressure)
Arteries
Endothelium and thick layer of smooth muscle and thick layer of connective tissue
Hormones and nervous system signals act on arteries to dilate or constrict arteries to control blood flow to different body parts
carry blood away from heart to organs throughout body
Movement of molecules and fluids between blood and cells in the body's tissues
Purpose
to transport needed/essential nutrients throughout the body
It occurs in one direction
Lymphatic system
maintains proper fluid distribution in body
lymph nodes filter lymph and house immune system cells that protect against bacteria and viruses
Terms
Hydrostatic pressure/blood pressure
drives fluid out of capillaries into tissues
Osmotic pressure/blood proteins
proteins that pull fluid back into capillaries. The fluid moves from tissues into capillaries
Interstitial fluid
Solution that surrounds and fills the tissue cells in multicellular organisms
composed of water, sugars, salts, fatty acids, amino acids, coenzymes, hormones, neurotransmitters, cellular
waste products
Capillaries
microscopic vessels that form networks (capillary beds). Permit diffusion of chemicals between blood and interstitial fluid
Diffusion
random thermal motion of particles of liquids, gases, or solids (type of passive transport)
High to low concentration