Chp 10

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10.1

Arteries and Arterioles:

- Arteries are the blood vessels that carry blood away from the heart. They have thick walls composed of distinct layers.

*Every time the heart contracts, blood surges from the heart and enters the arteries.

The arteries stretch to accommodate the inrush of blood.

-Pulse: Change in the diameter of the arteries following heart contractions.

-Heart contraction is followed by a relaxation phase. During this phase, pressure drops and elastic fibres in the walls of the artery recoil.

-Blood from the arteries passes into smaller arteries, called arterioles.

The Autonomic Nervous System:

- Controls the motor nerves that maintain equilibrium and regulates the diameter of the arterioles.

- Vasoconstriction: A nerve impulse that causes smooth muscle in the arterioles to contract, reducing the diameter of the blood vessel. (decreases blood flow to tissues)

- Vasodilation: Relaxation of the smooth muscle causes dilation of the arterioles, and blood flow increases

- Precapillary sphincter muscles regulate the movement of blood from the arterioles into the capillaries.

Atherosclerosis:

- A degeneration of blood vessels caused by the accumulation of fat deposits in the inner wall.

- Arteriosclerosis: A group of disorders that cause the blood vessels to thicken, harden, and lose their elasticity.

Aneurysm:

- A bulge that forms in the wall of a weakened blood vessel, usually an artery. The most common sites are the aorta of the heart, the abdominal aorta, and arteries in the brain.

Capillaries:

- The sites of fluid and gas exchange between blood and body cells. Many active cells, such as muscle cells, may be supplied by more than one capillary.

- Red blood cells must travel through capillaries in single file (small diameter)

- Oxygen diffuses from the blood into the surrounding tissues through the thin walls of the capillaries into the body cells.

- Oxygenated (oxygen-rich) blood appears red in colour, while deoxygenated (oxygen-poor) blood appears purple-blue as it leaves the capillary.

Veins and Venules:

- Venules: Capillaries merge and become progressively larger vessels. The walls of venules contain smooth muscle.

- Veins: Venules merge and have a greater diameter.

- Skeletal muscles also aid venous blood flow. Venous pressure increases when skeletal muscles contract and push against the vein. The muscles bulge when they contract, thereby reducing the vein's diameter. Pressure inside the vein increases and the valves open, allowing blood to flow toward the heart. Sequential contractions of skeletal muscle create massaging action that moves blood back toward the heart.

- As much as 65% of your total blood volume can be found in the veins.

10.1 Summary: Blood Vessels

- Arteries carry blood away from the heart.

- Vasoconstriction is a reduction in the diameter of the blood.

- Atherosclerosis is a narrowing of the arteries due to a buildup of plaque that contains fat.

- Capillaries are the site of fluid and gas exchange between the blood and cells.

10.2

The Heart:

- Pericardium: A fluid-filled membrane that surrounds the heart. The fluid bathes the heart, preventing friction between its outer wall and the covering membrane.

-Septum: A wall of muscle that separates the right and left sides of the heart.

- The heart consists of two parallel pumps. The pumping action is synchronized; muscle contractions on the right side mirror those on the left. The pump on the right receives oxygenated blood from the body tissues and pumps it to the lungs. The pump on the left receives oxygenated blood from the lungs and pumps it to the cells of the body.

- Pulmonary Circulatory System: The system of blood vessels that carry deoxygenated blood to the lungs and oxygenated blood back to the heart.

-Systematic Circulatory System: The system of blood vessels that carries oxygenated blood to the tissues of the body and deoxygenated blood back to the heart.

- Arium (plural: atria): A thin-walled chamber of the heart that receives blood m the veins.

- Ventricle: A muscular, thick-walled chamber of the heart that delivers blood to the arteries.

One- Way Blood Flow:

- The superior vena cava os a large vein that carries deoxygenated blood into the heart. It carries blood from the head, arms, and upper body.

- The inferior vena cava is a large vein that carries deoxygenated blood from the lower body (below the diaphragm) into the heart.

- Atrioventricular (AV) valves separate the atria from the ventricles. These valves prevent the backflow of blood from a ventricle into an atrium.

- Semilunar valves separate the ventricles from the arteries. These valves prevent the backflow of blood from an artery into a ventricle.

- Aorta: The largest artery in the body; carries oxygenated blood to the tissues.

- Coronary Arteries: Form a branch of the aorta and supply the cardiac muscle with oxygen and nutrients.

Cardiac Catheterization:

- A procedure used to diagnose and treat certain cardiovascular conditions.

- A thin tube called a catheter is inserted into an artery or vein and threaded through blood vessels to the heart.

The Heart's Tempo:

- The heart is a myogenic muscle, which means it contracts without external nerve stimulation.

- The heart's tempo is set by the sinoatrial (SA) node. This is a bundle of specialized nerves and muscles located in the upper right atrium. Nerve impulses are carried from the SA to other muscle cells by modified muscle tissue.

- The atrioventricular (AV) node serves as a conductor, passing nerve impulses via two large nerve fibres called Purkinje fibres. Purkinje fibres branch and carry electrical impulses throughout the ventricles.

- Sympathetic nervous system: Stimulated during times of stress and increases heart rate. This increases blood flow to tissues, enabling the body to meet increased energy demands.

- Parasympathetic nervous system: Stimulated during times of relaxation to slow the heart rate.

Heart Sounds:

-Systole: Contraction of the heart during which blood is pushed out of the heart

-Diastole: Relaxation of the heart during which the atria fill with blood.

- lubb is the first heart sound caused by turbulence from the closure of mitral and tricuspid valves at the start of systole.

- dubb is the second heart sound caused by the closure of aortic and pulmonic valves, marking the end of systole.

10.2 Summary: The Heart

- The pulmonary circulatory system is the system of blood vessels that carries blood to and from the lungs. The systematic circulatory system is the system of blood vessels that carries blood to and from the body.

- The heart consists of two parallel pumps separated by the septum.

*Blood enters the heart through the atria.

*Ventricles pump the blood to the body tissues.

*Atrioventricular valves prevent the flow of blood from the ventricles back into the atria.

*Semilunar valves prevent the flow of blood from arteries back into the ventricles.

*Coronary arteries supply the heart with oxygen and nutrients.

-The heart rate is set by the sinoatrial (SA) node. Contractions in the SA node travel to the atrioventricular (AV) node and then travel along the Purkinje fibres to the rest of the heart.

-Diastole is heart relaxation. Systole is heart contraction.

- The lubb-dubb sound is caused by the AV valves and the semilunar valves closing in turn as blood is pushed from the atria through the ventricles and out of the heart. If the valves do not close completely, the heart compensates by beating faster and pumping blood with more force.

10.3