The Circulatory System Chapter 33.1 & 33.2

Functions of the Circulatory System The human body is made up of million of cells. Most are not in direct contact with the external environment This is why we need a circulatory system The circulatory system transports oxygen, nutrients, and other substances thought out the body and removes waste from tissues

The Heart Hollow About the size of a fist All muscle

The Heart The walls of the heart are two thin layers of epithelial and connective tissue that sandwich around the muscle Myocardium Powerful contractions of the myocardium pump blood through the circulatory system.

The adult heart contract 72 times per minute The Heart The adult heart contract 72 times per minute

The Heart Heart is divided into four chambers:

The Heart Valves – Located between the atria and the ventricles When blood flows from the atria to ventricles valves open When ventricles contract, the valves close Prevents blood from flowing back to the atria also located at the exits of each ventricle System of valves keep blood flowing in one direction

The Hearts Blood Supply The heart needs a constant blood supply of oxygen and nutrients Coronary Arteries – branch from the aorta and run through heart tissue These arteries are relatively narrow despite the fact that the heart requires so much Blocked arteries = muscle cells begin to die Moments after oxygen is cut off Leads to heart attack

The Hearts Blood Supply

Circulation

Circulation Pulmonary Circulation – the right side of the heart pumps oxygen poor blood from the heart to the lungs

Circulation Systemic Circulation – the left side of the heart pumps oxygen rich blood to the rest of the body

EKG (Electrocardiography) Heartbeat Two networks of muscle fibers coordinate the heart’s pumping action When a single muscle fiber in either network is stimulated the entire network contracts. EKG (Electrocardiography) a test that records the electrical activity of the heart.

Heartbeat First: Atria Contract Each contraction begins in a small group of cardiac muscle fibers called the SA Node SA Node – sinoatrial node Located in the Right Atrium Sets the pace for the heart called the Pacemaker SA Node fires An electrical impulse spreads through the entire network of muscle fibers in the atria Atria Contract

Second: Ventricles Contract Heartbeat Second: Ventricles Contract The impulse from the SA Node is picked up by the AV (atrioventricular node) just like the SA Node The impulse is delayed for a fraction of a second while the atria contract and pump blood into ventricles Then the AV Node produces impulses that spred through the ventricles Ventricles Contract – Pump blood Out

Heartbeat

Heartbeat Lub Dub Heart beat sound Sound is the opening and closing of valves between atria and ventricle

Control of Heart Rate Heart rate varies depending on your body’s need to take in oxygen and release carbon dioxide Heat beat is not directly controlled by the nervous system Autonomic nervous system does influence the activity of the SA node Neurotransmitters released by the nervous system increase heart rate Parasympathetic nervous system decrease heart rate

Blood Vessels Arteries Carry blood from the heart to the tissues of the body Carry oxygen rich blood (except for pulmonary artery) Thick elastic walls Withstand pressure produced by the heart 3 Layers: Connective Tissue Smooth Muscle Endothelium

Blood Vessels Capillaries Extremely, thin walls allow for gases (O2 & CO2), nutrients and waste products to diffuse in and out

Blood Vessels Veins Returns blood back to the heart Blood flow is usually against gravity skeletal muscle aid in circulation Vein also contain valves that prevent backflow

Blood Pressure When the heart contracts it produces a wave of fluid pressure in the arteries known as blood pressure Blood pressure is required to allow blood to move through the body Sphygmomanometer – an inflatable cuff with a pump and a meter used to measure blood pressure

Blood Pressure Systolic Pressure – (High #) The force in the arteries when the ventricle contracts Diastolic Pressure – (Low #) The last pulse heard, the force in the arteries when the ventricles relax. A typical blood pressure is 120/80

Regulating Blood Pressure Sensory receptors in blood vessels detect blood pressure and send impulses to the brain High Blood Pressure – neurotransmitters that relax the smooth muscles in the blood vessel walls are released Low Blood Pressure – neurotransmitters are released that cause the smooth muscles in vessel walls to contract.

Regulating Blood Pressure Kidneys regulate Blood Pressure by affecting the volume of blood. Triggered by hormones produced by the heart and other organs High Blood Pressure causes kidneys to remove water and eliminate it as urine Low Blood Pressure water is conserved

Blood Blood is a tissue Plasma 55% of total blood volume Straw colored 90% water & 10 % dissolved gases, salts, nutrients, proteins, cholesterol, and important compounds Water helps control body temperature Proteins – one type is Fibrinogen is necessary for blood to clot

Red Blood Cells (Erythrocytes) Most numerous cells in blood Main function is to transport oxygen Hemoglobin – A protein binds with oxygen Crimson color comes from the iron in hemoglobin Also transports some carbon dioxide Shape is important allows oxygen to bind easier

White Blood Cells (Leukocytes) White Blood Cells guard against infection, fight parasites, and attack bacteria White Blood Cells can increase in number dramatically during an infection

Blood Platelets Cell fragments Aid in clotting

Circulatory System Disease 3 Common Diseases Heart Disease Atherosclerosis – a condition which fatty deposits called plaque build up in artery walls and eventually cause arteries to stiffen Angina – Chest pain, can be a sign of restricted blood flow Eventually heart can be weakened or damaged by oxygen deprivation, leading to heart failure

Circulatory System Disease Heart Attack – occurs as heart muscle cells become damaged and possibly die Can also damage SA and/or AV Nodes Cocaine and cigarette smoking can lead to a heart attack Symptoms: Nausea Shortness of breath Chest pain Pain in the neck, jaw, or left arm

Circulatory System Disease Stroke The sudden death of brain cells when their blood supply is interrupted Some are caused bu blood clots in the brain Also by the breaking of weak blood vessels Symptoms: Severe Headache Numbness Confusion Trouble speaking

Circulatory System Disease Stroke Results of a stroke depend on where in the brain they occur Some cause death Some paralysis or loss of speech High Blood Pressure AKA Hypertension – 140/90 or higher Heart damage can occur because the heart struggles to push blood through vessels

Circulatory System Disease High Blood Pressure Also tears small blood vessels Stiffened arteries from atherosclerosis can contribute to high blood pressure Uncontrolled High Blood Pressure can lead to : Heart attack Stroke Kidney damage Also known as the silent killer – you can have it for years till one of the above happens

Circulatory System Disease Cholesterol A lipid Part of animal cell membrane Also used in the synthesis of some hormones Bile Vitamin D

Circulatory System Disease Cholesterol It is transported around the body by two types of lipoproteins Low – Density Lipoprotein (LDL) High Density Lipoprotein (HDL) LDL – Bad Protein carrier HDL – generally transports excess cholesterol from body to the liver for removal

Circulatory System Disease Cholesterol Measuring cholesterol is actually measuring lipoproteins Normal cholesterol levels range from 100 – 200 milligrams per deciliter LDL should be below 100 HDL for males < 40 and for females < 50

Circulatory System Disease Cholesterol Source The liver manufactures cholesterol Consumed in:

Circulatory System Disease Cholesterol Research indicates that high cholesterol, along with other risk factors, lead to atherosclerosis and high risk of a heart attack

Circulatory System Disease Cholesterol LDL Receptors In the Liver Control the removal and determine the rate the liver will produce cholesterol

Circulatory System Disease Cholesterol Some people carry genes that produce defective LDL receptors This creates two problems: Liver can’t remove cholesterol from the blood Liver does not get signal to stop making cholesterol

Circulatory System Disease Cholesterol A high cholesterol diet cause excess cholesterol to be stored in the liver Liver then stops making LDL receptors Defect mimics genetic disorder Treatment: Statins – Block the synthesis of cholesterol in liver - cells Cause liver to produce LDL receptors thus remove cholesterol

Factures Affecting Blood Flow Pressure Blood Volume Resistance Viscosity Disease Exercise