Topic 6.2 Flashcards
Who discovered the circulation of the blood with the heart acting as the pump?
William Harvey
Arteries
- Vessels that carry blood from the heart to the tissues of the body
- Thick walls and elastic fibres
Ventricles
- Main pumpting chambers of the heart
- Left ventricle pumps to the entire body
- Right ventricle pumps to the lungs
What do ventricles have to pump blood
- Thick strong muscles (with elastic tissues)
- Small space in the middle to allow for passive recoil
Why do arteries have thick walls?
- Withstand the constanty changing and intermittently high blood presure without bulging outwards (aneurysm) or bursting
Annotate the diagram of artery
Refer to picture
Systolic pressure
- Peak pressure reached in an artery (when blood is pumped from the ventricle)
- Pushes the wall of the artery outwards, widening the lumen and stretching elastic fibres in the wall
Diastolic pressure
- Minimum pressure in the artery
What mechanism does the body use to prevent diastolic pressure from becoming too low?
- The stretched artery walls recoil and squeeze blood in the lumen
- Saves energy while maintaining relatively high pressure
- Ensure the steady and continuous blood flow
Vasoconstriction
- Wall of the artery contract
- Circumference is reduced and the lumen is narrowed
- Increases blood pressure
- Restricts bloodflow to part of the body
Capillaries
- Narrowest blood vessels
- Thin wall
- Small diameter
- Branch and rejoin repeatedly to form a capillary network
- Transport blood to almost all tissues in the body
Why is the capillary wall one layer thin
- Permeable
- Allows nutrient and waste exchange
Outline the process of nutrient and waste exchange at the capillary
- Permeable capillary walls allow part of the plasma to leak out and form tissue fluid (contins oxygen, glucose, monomer nutrients)
- The fluid flows between the cells in the tissue, allowing the cells to absorb useful substances
- Cells excrete waste products into the tissue fluid
- Tissue fluid reenters the capillary network with the waste products
Why does the permeability of capillary wall differ between tissues?
- Particular proteins and other large particles can reach certain tissues but not others
- Permeability also changes overtime in response to the needs of the tissues
Veins
- Collect blood at low pressure from the tissues of the body
- Carry blood back to the atria of the heart
- Veins do not require thick walls and contain fewer muscle and elastic fibres
- Have valves
Atrium
- Receives blood from veins
- Right atrium receives blood from the entire body
- Left atrium receives blood form the lung
Outline the function of the valves in veins
- Prevent backflow due to low pressure
- if blood starts to flow backwards, it gets caught in the flaps of the pocket valve, which blocks the lumen when filled with blood
- When blood flows towards the heart, it pushes the flaps to the sides of the vein, opening the valve
- One direction only
Label the diagram of the heart
Refer to picture
Outline the double circulation in the human body
- One circulation to and from all other organs (systemic ciruclation)
- One circulation to and from the lung (pulmonary circulation)
- Blood is oxygenated by the pulmonary circulation
Atherosclerosis
Development of fatty tissues called atheroma in the artery wall adjacent to the endothelium
Describe how atheroma is formed
- Low density lipoproteins (LDL) containing fats and cholesterol accumulate
- Phagocytes engulf the fats and cholesterol by endocytosis and grow very large
- Smooth muscle cells migrate to form a touch cap over the atheroma
- Artery wall bulges into the lumen, narrowing it and impeding blood flow
Coronary occlusion
- Narrowing of hte arteries that supply blood containing oxygen and nutrients to the heart muscle
- Lack of oxygen causes pain, known as angina, and impairs the muscle’s ability to contract
- The heart beats faster to maintain blood circulation
Describe what happens when the atheromas ruptures
- The fibrous capcovering atheromas sometimes ruptures
- Stimulates the formation of blood clots that can block arteris supplying blood to the heart and cause acute heart probems
Outline causes (increased risk) of atheroma
- High blood concentrations of LDL (low density lipoprotein)
- Chronic high blood glucose concentrations, due to overeating, obesity or diabetes
- Chronic high blood pressure due to smoking, stress, or any other cause
- Consumption of trans fats, which damage the endothelium of the artery
- Infection of the artery wall
Sinoatrial node
- Specialized muscle cells in the right atrium
- Initiate heartbeat
- Pacemaker of the heart
Describe the initiation of heartbeat
- Membrane of a heart muscle cell depolarizes when the cell contracts
- Activates adjacent cells to contract
- Sinoatrial nodes are the first to depolarize in each cardiac cycle
Outline treatment for defective sinoatrial node
- An artificial pacemaker can regulate the heartbeat
- An electronic device that is placed under the skin with electrodes implanted in the wlal of the heart
- Initiate each heartbeat in place of the sinoatrial node
Describe the propagation of electrical signal in each heartbeat
- SA node initiates the heartbeat while sending an electrical signal that spreads throughout the walls of the atria
- Electrical signals propagate across interconnections adjacent fibres
- The fibres are branched so the signal can be passed on to several places
- This propagation of the electrical signal causes the whole of both left and right atria to contract
- After a time delay, the electrical signal is conveyed to the ventricles (the atria pump blood to ventricles during the time delay)
- Ventricles contract and pump blood out into the arteries
With the help of a graph, describe how pressure changes in the atria and ventricles during the cardiac cycle
State the structure in the brain that regulate the heartbeat
Medulla
Describe how the cardiovascular centre regulate heartbeat
- Recieves inputs from receptors that monitor blood pressure, pH and oxygen concentration
- Low blood pressure/low oxygen concentration/low pH cause the medulla to send a message to increase the flow rate of blood to the tissues
Outline the effect of epinephrine on heart rate
Increases heart rate to prepare for vigorous physical activity
Fill in the following chart of the cardiac cycle events
