The circulatory system

Question 1

Impact issues: the breath of life

Answer 1

during cardiac arrest the heart stops its regular beating. CPR( cardiopulmonary resuscitation) is a life saving technique. A defibrillator should be used ASAP to shock a heart back to its regular rhythm. Automated external defibrillators are available at many public places. The heart and its vessels is a complex life sustaining system

Question 2

The cardiovascular system-moving blood through the body

Answer 2

Heart and blood vessels make up the cardiovascular system.

Question 3

Heart

Answer 3

muscular pump that generates the pressure required to move the blood through the body

Question 4

Blood vessels

Answer 4

distribution tubes of varying diameters

Question 5

route of circulation

Answer 5

heart–>arteries–>arterioles–>capillaries—>venules–>veins and back to the heart

Question 6

Circulation blood is…

Answer 6

vital to mantain homeostasis. The cardiovascular system is the bodys internal rapid transport system for oxygen, nutrients, secretions, and wastes via blood. Homeostasis depends on the reliable supply of blood to all of the body.

Question 7

The cardiovascular system is..

Answer 7

linked to the lymphatic system. The lymphatic system vessels pick up the fluid and return it to the general circulation. b/c of the pressure in the cardiovascular system, water and other proteins leak out to become part of the interstitial fluid

Question 8

The heart : A double pump

Answer 8

The heart is a durable pump made mostly of cardiac muscle (myocardium) and is surrounded by a tough fibrous sac(pericardium). The inner lining of the heart is the endocardium; it is composed of connective tissue and epithelial cells (endothelium)

Question 9

The heart has..

Answer 9

two valves and 4 chambers.

Question 10

Septum

Answer 10

divides the heart into two halves right and left. Each half has an atrium(recieving chamber) and a ventricle(pumping chamber) seperated by an atrioventricular valve ( av valve) The av valve on the right is a tricuspid valve and the one on the left is the mitral valve or biscuspid valve. Chordae tendinae (heartstrings) connect the av valve flaps to the ventricular wall. Blood exits each ventricle through a semi lunar valve. Heart muscles are serviced by the coronary circulation; coronary arteries branch off the aorta froming a capillary bed around the heart.

Question 11

In a heartbeat…

Answer 11

the hearts chamber contract(systole) then relax(diastole). As the atria fills ventricles are relaxed. Pressure of the blood in the atria forces the AV valves open and the ventricles fill as the atria contracts. When the ventricles contract the AV valves close and blood flows out through the semilunar valves. The cardiac output is the amount of blood each ventricle can pump in a minute; on average the output from each ventricle is about 5 liters. The heart sound “lub” is made by closing of the AV valves; the “dup” sound is the closure of the semilunar valves.

Question 12

The two circuits of blood flow

Answer 12

The pulmonary circuit and systemic circuit

Question 13

Pulmonary circuit

Answer 13

blood picks up oxygen in the lungs. recieves blood from the tissues taking it through the lungs for gas exchange. Path of blood flow: blood from tissues enters right atrium–>tricuspid valve—>right ventricle—>right semilunar valve—->pulmonary arteries—>lungs—>pulmonary veins—>left atrium. Blood returning from the body tissues is high in CO2 and low in oxygen these concentrations are reversed after passage through the lung capillaries

Question 14

Systemic circuit

Answer 14

oxygenated blood is pumped through the body. Blood moves from the left atrium—>bicuspid valve–>left ventricle—>left semilunar valve—>aorta—->body tissues. Blood from the upper body travels through the superior vena cava. Blood from the digestive tract is shunted through the liver for processing. After a meal blood laden with nutrients is carried from the digestive tract in the hepatic portal vein to the liver capillaries. There it passes through the liver capillary beds before leaving via the hepatic vein to return to the general circulation; oxygenated blood reaches the liver through the hepatic artery.

Question 15

How cardiac muscles contract

Answer 15

Electrical signals from “pacemaker” cells drive the hearts contractions. Cardiac muscle cells are linked by intercalated discs, which rapidly pass signals to contract throughout the heart. The cardiac conduction system consists of noncontractile cells that are self excitatory(pacemaker cells). Excitation for a heartbeat is initiated in the sinotrial (SA) node it is then passed to the atrioventricular (AV) node and on to the purkinje fibers which make contact with the muscle cells that result in ventricular contraction. It is the action of the cardiac pacemaker (SA node) that produces our normal heartbeat.

Question 16

The nervous system adjusts heart activity

Answer 16

the nervous system can adjust heart rate and strength of cardiac muscle contraction; stimulation by one set of nerves increases the rate and strength while stimulation by other nerves decreases heart rate. Centers for nervous control of the heart lie in the spinal cord of the brain.

Question 17

Blood Pressure

Answer 17

Blood exerts pressure against the walls of blood vessels. Normal systolic pressure( peak pressure in the aorta)n is 120 mm of Hg; normal diastolic pressure( lowest pressure in the aorta) is 80mm. Blood pressure valves give important clues as to the condition of the vessels and flow of blood through them.

Question 18

Hypertension

Answer 18

blood pressure is too high can lead to stroke or heart attack

Question 19

Hypotension

Answer 19

blood pressure is too low loss of water or blood volume can lead to circulatory shock

Question 20

Structure and functions of Blood Vessels

Answer 20

arteries are large blood pipelines. b/c of their elastic walls arteries tend to “smooth” out the pressure changes associate with the discontinuous pumping cycle of the heart( felt as a pulse). b/c of their large diameters arteries present little resistance to flow; blood pressure does not decrease very much in them.

Question 21

Arterioles

Answer 21

are control points for blood flow. Arteries branch into smaller arterioles where the greatest pressure drop occurs. The wall of arteriole has rings of smooth muscle over a single layer of elastic fibers. They serve as control points where adjustments can be made in blood volume distribution.

Question 22

Capillaries

Answer 22

are specialized for diffusion. are the smallest and thinnest tube in the path of circulation and is specialized for exchange of substances with interstitial fluid. Total resistance is less than in arterioles so the drop in blood pressure is not as great.

Question 23

Venules and veins

Answer 23

return blood to the heart. Capillaries merge into venules. Venules merge into veins. Veins are blood volume reservoirs (50-60% of blood volume) because their walls can distend or contract. Skeletal muscles adjacent to veins squeeze the walls to move the blood along on its way back to the heart; valves prevent backflow. Varcose veins can form when the veins have become overstretched and the valves weakened

Question 24

Vessels

Answer 24

help control blood pressure. The brain monitors signals from various arteries to determine the rate of heartbeat and any other changes needed in vessel diameters. If the blood pressure decreases the diameter of the arteries decrease (vasoconstriction). If the blood pressure increases the arterioles are instructed to relax(vasodialation). In the baroreceptor reflex special receptors in the carotid arteries monitor changes in blood pressure and send the information to the brain for action.

Question 25

Capillaries:where blood exchanges substances with tissues

Answer 25

A vast network of capillaries weaves closely to all living body cells. Capillaries compromise most of the cardiovascular system. The velocity of blood flow slows at the diameter of the vessels decreases. It is slowest in the capillaries to provide for maximum exchange. Many substances enter and leave capillaries by diffusion. Diffusion is a slow process and isn’t efficient over long distances. Billions of capillaries ensures all cells are near enough to a capillary to receive nutrients and give up wastes; blood flow here is slow enough to allow diffusion. Some substances pass through “pores” in capillary walls. Water filled slitlike areas between the cells of capillary walls allow water soluble substances to exit the blood due to pressure(bulk flow). This movement of fluids and solutes is important to homeostasis and maintaining blood pressure. Blood in capillaries flow onward to venules. Precapillary sphincters regulate the flow of blood into capillaries. Capillaries are the turn around points for the cardiovascular system.

Question 26

Cardiovascular disorder

Answer 26

risk factors:family history,hypertension, obesity, smoking, and age. Inflammation which leads to the production of C-reactive proteins by the liver, may also play a role. Arteries can be clogged or weakened. Arteriosclerosis is a hardening of the arteries . When cholesterol and other lipids build up in these hardened arteries atherosclerosis occurs. Low density lipoproteins (LDL or “bad” cholesterol) carry cholesterol into the arterial walls; high density lipoproteins remove it. 200 mg cholesterol per mL of blood or less is considered acceptable for most people. Surgery may be needed to clear blocked arteries. Coronary bypass involves using a large vessel from elsewhere in the body to bypass a complete blocked artery in the heart. Large angioplasty uses a laser to vaporize plaques while balloon angioplasty uses small balloons to flatten the plaques to open room in the artery; a wire “stent” may be inserted to keep the ballooned area open. Statins are drugs designed to reduce the amount of cholesterol in the blood . Disease, injury, or defects can weaken artery walls so they bulge outward due to blood pressure, forming an aneurysm , they can be fatal if the artery bursts. Heart damage can lead to a heart attack and heart failure. A heart attack is damage to or death of heart muscle. In heart failure the heart is weak and doesn’t pump blood efficiently. Arrhythmia’s are irregular heart rhythms. Electrocardiograms(ECG) are recordings of the cardiac cycle and can be used to reveal irregular heart rhythms. bradycardia is below normal rhythm . tachycardia is above normal rhythm. Ventricular fibrillation happens when the ventricles contract haphazardly so that blood is not pumped correctly this can lead to cardiac arrest,

Question 27

A heart healthy life style

Answer 27

diets low in fat, exercise, and not smoking are life style changes that can reduce the risk of heart disease.