6.2 & H5 The Transport System

Presenting your T-Test results You want to tell your reader whether or not there was a significant difference between condition means. You can report data from your own experiments by using the template below.  An independent t-test was compare with IV 1 and IV 2. “There was a significant (not a significant) difference in the scores for IV level 1 (M=___, SD=___) and IV level 2 (M=___, SD=___) conditions; t(__)=___, p = ____”

6.2.1  Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of the blood through the heart

Valves and Direction of Blood Flow                Heart Chambers and Vessels

6.2.2  State that coronary arteries supply heart muscle with oxygen and nutrients The heart is a muscle that must continually contract in order to pump blood around the body Coronary arteries form a network of vessels around the heart and supply the cardiac tissue with oxygen and nutrients (i.e. glucose) These are required to produce the necessary energy via aerobic respiration - if a coronary artery is blocked, a heart attack may occur

6.2.3  Explain the action of the heart in terms of collecting blood, pumping blood and opening and closing valves Blood returning from all parts of the body (except lungs) enter the right atrium via the vena cava - this blood is relatively deoxygenated The blood passes from the right atrium to the right ventricle and then via the pulmonary artery to the lungs (where blood is reoxygenated) The blood returns to the left atrium via the pulmonary vein and passes through the left ventricle to the aorta, where it is pumped around the body

6.2.3 Cont., The heart valves maintain the one-way flow of blood: When the atria contract, atrioventricular (AV) valves open Blood flows from the atria and into the ventricles When the ventricles contract, the AV valves close and semilunar valves open This forces blood out of the ventricles and into the arteries

Flow of Blood Blood Flow through Lungs And Heart

IP Physiology: Anatomy Review: Blood vessel structure and function Question 1-7; 10-12, 16, 18, 24, 26, 27, 29

6.2.5  Explain the relationship between the structure and function of arteries, capillaries and veins Arteries carry blood at high pressure (80 - 120 mm Hg) The tunica intima is the innermost tunic. It is in intimate contact with the blood in the lumen. Arteries have a narrower lumen (to maintain high pressure) surround by a thick wall made of two layers The middle layer (tunica media) contains muscle and elastin to help maintain pulse flow (it can contract and stretch) The outer layer (tunica adventitia) contains collagen prevents the artery rupturing due to the high pressure blood flow

Structure of Blood Vessels

Veins Veins carry blood under low pressure (<10 mm Hg) They have a very wide lumen (keeps pressure low and allows greater flow of blood) The walls of tissue surrounding the vein are thin (blood is not travelling in rhythmic pulses) They have valves to prevent blood pooling at extremities (arteries do not have valves)

Capillaries Capillaries are involved with material and gas exchange with the surrounding body tissue Blood pressure in the capillaries is relatively low (~15 mm Hg) and they have a very small diameter (~5 micrometers wide) Their wall is made up a a single layer of cells to allow for ease of diffusion Capillaries may contain pores to aid the transport of material

Capilarry

H.5.4 Outline atherosclerosis and the cause of coronary thrombosis Atherosclerosis is the hardening and narrowing of the arteries, due to the deposition of material commonly known as plaque Damage to the artery walls (e.g. due to high blood pressure) causes chronic inflammation, leading to the accumulation of lipids, cholesterol, cell debris and calcium Atheromas (fatty deposits) develop in the arteries and significantly reduce the diameter of the lumen (stenosis) and reduces the elasticity of the artery wall needed for pulse flow This may lead to the formation of clots and blockages in the artery, and if this occurs in the coronary arteries (coronary thrombosis), it may lead to a heart attack (acute myocardial infarction)

Atherosclerosis

H.5.5  Discuss factors that affect the incidence of coronary heart disease Risk factors for coronary heart disease (CHD) include: Exercise – sedentary life style or excessive exercise can both place a strain on normal heart activity Genetics – having hypertension (high blood pressure) or a family history of heart attacks increases the risk Gender – males are more at risk than females due to low estrogen levels (risk increases in women post-menopause as levels fall) Smoking – smoking raises blood pressure because nicotine causes vasoconstriction Obesity – being overweight places additional strain on the heart Diet – too much saturated fats and cholesterol promotes atherosclerosis, high salt levels and excessive alcohol intake are also risk factors Age – old age leads to less flexible blood vessels

H.5.1  Explain the events of the cardiac cycle, including atrial and ventricular systole and diastole, and heart sounds The cardiac cycle describes the series of events that take place in the heart over the duration of one heart beat It is comprised of a period of contraction (systole) and relaxation (diastole)

H.5.1 Cont., Systole Blood returning to the heart will freely flow from the atria to the ventricles as the AV valves kept open by the pressure in the atria The sinoatrial node (pacemaker) receives signals to fire when the ventricles are almost full (~70%) The contraction of the atria (atrial systole) causes blood to fill the ventricles to the maximum The signal from the SA node is transferred to the AV node and then via Purkinje fibres to cause the delayed contraction of the ventricles As the ventricles contract, the increase of pressure in the ventricles closes the AV valves, causing the first heart sound ('lub')

H.5.1 Cont., Diastole The increased pressure causes the semilunar valves to open and blood to flow away from the heart As the blood flows into the arteries, the pressure falls in the ventricles This causes some arterial back flow, which closes the semilunar valves and causes the second heart sound ('dub') When the pressure in the ventricle drops below the pressure in the atria the AV valves open and the cardiac cycle can repeat 

Blood Pressure

H.5.2  Analyze data showing pressure and volume changes in the left atrium, left ventricle and the aorta, during the cardiac cycle

IP Physiology: Intrinsic Conductive System

6.2.4  Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline) The contraction of the heart tissue (myocardium) is myogenic, meaning the signal for cardiac contraction arises within the heart muscle itself Within the wall of the right atrium are a specialized plexus of nerves called the sinoatrial node (SAN) The sinoatrial node initiates contraction of the cardiac muscle and acts as a pacemaker, regulating normal sinus rhythm

6.2.4 Cont., SA node stimulates atria to contract and, when excitation reaches the junction between atria and ventricles, stimulates another node (atrioventricular node) The atrioventricular node (AVN) sends signals via the Bundle of His to Purkinje fibres, which cause ventricular contraction This sequence always ensures their is a delay between atrial and ventricular contractions, resulting in two heart sounds ('lub dub')

EKG Tracing P = Artial depolarization QRS = Ventricular depolarization T = ventricular repolarization

Different Rhythms

Fibrillation = erratic, rapid heart beat Defibrillation =

Myogenic Control of the Heart Beat The pacemaker is under autonomic control from the brain, specifically the medulla oblongata (brain stem) Sympathetic nerves speed up heart rate by releasing a neurotransmitter (noradrenaline) to increase the rate of myocardial contraction Parasympathetic nerves slows down heart rate by releasing a neurotransmitter (acetylcholine) to decrease the rate of myocardial contraction Additionally, the heart rate may be increased by the chemical release of the hormone adrenaline into the blood (from the adrenal gland)

H.5.3  Outline the mechanism that controls the heartbeat, including the roles of the SA node, AV node and conducting fibres in the ventricular walls The contraction of the heart tissue (myocardium) is myogenic, meaning the signal for cardiac contraction arises within the heart muscle itself Within the wall of the right atrium are a specialized plexus of nerves called the sinoatrial node (SAN) The sinoatrial node initiates contraction of the cardiac muscle and acts as a pacemaker, regulating normal sinus rhythm It stimulates atria to contract and, when excitation reaches the junction between atria and ventricles, stimulates another node (atrioventricular node)

H.5.3 Cont., The atrioventricular node (AVN) sends signals via the Bundle of His to Purkinje fibres, which cause ventricular contraction This sequence always ensures their is a delay between atrial and ventricular contractions, resulting in maximum blood flow By having ventricular contractions start at the apex (bottom), it ensures blood is pushed up towards the arteries

Myogenic control of the heart beat

H.5.3 Cont., The pacemaker is under autonomic control from the brain, specifically the medulla oblongata (brain stem) Sympathetic nerves speed up heart rate by releasing a neurotransmitter (noradrenaline) to increase the rate of myocardial contraction Parasympathetic nerves slow down heart rate by releasing a neurotransmitter (acetylcholine) to decrease the rate of myocardial contraction Additionally, the heart rate may be increased by the chemical release of the hormone adrenaline into the blood (from the adrenal gland)

6.2.6  State that blood is composed of plasma, erythrocytes, leukocytes (phagocytes and lymphocytes) and platelets There are four main components to blood: Plasma - the fluid medium of the blood Erythrocytes - red blood cells (involved in oxygen transport) Leukocytes - white blood cells, such as phagocytes (non-specific immunity) and lymphocytes (specific immunity) Platelets - responsible for blood clotting (haemostasis)

6.2.7  State that the following are transported by blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat The following things are transported by blood: Nutrients (e.g. glucose) Antibodies Carbon dioxide Hormones Oxygen Urea Heat (not a molecules, unlike all the others

Muscles Structure: Cardiac vs Skeletal Similarities between cardiac and skeletal muscle: Both are composed of actin and myosin fibrils arranged in the same way giving a stripped appearance.

Differences between cardiac and skeletal muscle Cardiac cells are: shorter and wider The cytoplasm is not multinucleated Cells are Y-shaped They are not under voluntary control They are myogenic, i.e. they do not need nervous stimulation. Contraction arises from within the hearts SAN.

Two features which promotes rapid propagation of the electrical stimulus through cardiac muscle Y-shape promotes greater conductivity Intercalated discs are the junctions between the cells and have gap junctions The gap junctions (pores) produce low electrical resistance due to transfer of ions from cell to cell

Hypertension – a fancy name for high blood pressure Chronic hypertension result in blood vessels in the brain bursting. Causes of vessels bursting: The rise in pressure the rough surface of the atheroma (fatty deposits that weaken the arterial walls) can trigger a blood clot the clot restricts flow or block arteries weakening of the arteriole walls leads to bulging and aneurisms weaken blood vessels in the brain leading to stroke.

Blood Pressure Ranges Normal range for systolic pressure? 100 - 120 mm Hg Normal range for diastolic pressure. 60 – 90 mm Hg