cardiovascular system Flashcards
What is necessary for all living cells regarding materials?
Delivery of raw materials (nutrients, oxygen) and removal of waste products (e.g. carbon dioxide)
This exchange is crucial for maintaining cellular function and homeostasis.
What are the two transport systems in humans?
Circulatory system and lymphatic system
These systems work together to facilitate the exchange of materials throughout the body.
What are the components of the circulatory system?
Heart, blood, and blood vessels
The heart acts as a pump, while blood carries nutrients and oxygen.
Where is the heart located?
In the thoracic cavity
This central position allows for effective circulation to the rest of the body.
What type of muscle is the heart made of?
Cardiac muscle
This involuntary muscle contracts to pump blood throughout the body.
What are the three layers of the heart?
Epicardium, myocardium, endocardium
Each layer has distinct roles in protecting and facilitating the heart’s function.
What is the function of the epicardium?
Protects and lubricates the outer section of the heart
It is the outermost layer of the heart.
What is the myocardium responsible for?
Pumping action of the heart
This thick muscular layer is crucial for effective blood circulation.
What is the role of the endocardium?
Protects valves and chambers, prevents blood sticking
It is the innermost layer of the heart.
What surrounds and protects the heart?
Pericardium
It holds the heart in position and provides space for it to expand and contract.
What are the four chambers of the heart?
Right atrium, right ventricle, left atrium, left ventricle
These chambers play critical roles in the heart’s pumping action.
Describe the dual pump function of the heart.
Blood passes through the heart twice in one cycle
The right side pumps blood to the lungs, and the left side pumps blood to the rest of the body.
What is the difference between pulmonary and systemic circulation?
Pulmonary circulation is low pressure, low resistance; systemic circulation is high pressure, high resistance
This difference is crucial for the distribution of blood throughout the body.
Where does deoxygenated blood enter the heart?
Right atrium via the inferior and superior vena cava
This marks the beginning of the pulmonary circuit.
What happens to oxygenated blood from the lungs?
It enters the left atrium via the pulmonary vein
This blood is then pumped to the rest of the body through the aorta.
What are the major blood vessels involved in the circulatory system?
- Pulmonary artery (heart>lungs)
- Pulmonary vein (lungs>heart)
- Aorta (heart>body)
- Vena cava (body>heart)
- Hepatic artery (heart>liver)
- Hepatic vein (liver>heart)
- Mesenteric artery (heart>GI tract)
- Mesenteric vein (GI tract>heart)
- Renal artery (heart>kidneys)
- Renal vein (kidneys>heart)
- Carotid artery (heart>head)
- Jugular vein (head>heart)
- Coronary arteries (aorta>heart)
- Coronary vein (heart>right atrium via coronary sinus)
These vessels facilitate the movement of blood throughout the body.
What is coronary circulation?
It supplies blood to the heart muscle
Coronary arteries branch off the aorta and form a network of capillaries across the heart.
What causes coronary heart disease?
Fatty deposits building up in coronary artery walls
This condition narrows the passageway for blood movement (atherosclerosis) and can lead to heart attacks.
What is a myocardial infarction?
Occurs when blood flow to the heart muscle is reduced or stopped
This can cause heart muscle tissue to die due to lack of oxygen.
What is the function of heart valves?
Ensure that blood flows in the proper direction through the heart
They operate passively based on pressure differences.
What are the four main heart valves?
- Right atrioventricular (AV) (tricuspid)
- Left atrioventricular (mitral/bicuspid)
- Pulmonary valve
- Aortic valve
Each valve serves a specific function in blood flow regulation.
What are atrioventricular (AV) valves?
Valves located between the atria and ventricles
They prevent backflow into the atrium during ventricular emptying.
How do semilunar valves function?
They prevent blood from flowing back into the ventricles
These valves open when ventricular pressure exceeds that in the arteries.
What characterizes arteries?
Thick muscular walls to carry blood at great pressure
They also allow for vasodilation and vasoconstriction.
What are the features of veins?
Thin muscular walls, wide lumen, valves to prevent backflow
They carry deoxygenated blood back to the heart.
What is the structure of capillaries?
Very thin walls, often one cell thick
This structure allows for efficient gas exchange and nutrient transfer.
What is the approximate volume of blood in an adult human?
~5L of blood
Blood is a complex mixture of cells suspended in plasma.
What are the main components of blood?
- Plasma
- White blood cells (leukocytes)
- Platelets (thrombocytes)
- Red blood cells (erythrocytes)
Each component has a specific function in the circulatory system.
What is the composition of plasma?
- Water (91.5%)
- Proteins (7%)
- Solutes (1.5%)
Plasma serves as the liquid medium for blood and carries various substances.
How is oxygen delivered to cells?
Carried inside red blood cells attached to haemoglobin
This method is crucial because oxygen is only slightly soluble in water.
What is the structure of red blood cells (erythrocytes)?
- Biconcave shape
- Contains haemoglobin
- No organelles
- Miniature size
These features enhance their ability to transport oxygen.
How long is the lifespan of red blood cells?
~120 days
They are continually formed in red bone marrow and destroyed by macrophages.
What determines blood type?
Presence of antibodies and antigenic substances on the cell surface
The ABO blood group system is one of the most important classifications.
What happens during blood transfusions if there is a mismatch?
Agglutination occurs, causing clotting
Plasma compatibility is the inverse of red blood cell compatibility.
What is the role of white blood cells (leukocytes)?
Regulate the immune system and protect the body from disease
They play a crucial role in both specific and non-specific immune responses.
What are the main types of white blood cells?
- Granulocytes (neutrophils, eosinophils, basophils)
- Monocytes
- Lymphocytes (T & B cells)
Each type has specific functions in immune response.
What is the function of platelets (thrombocytes)?
Involved in clotting (haemostasis)
They help prevent blood loss from damaged vessels.
What are the steps involved in haemostasis?
- Blood vessels contract (vasoconstriction)
- Platelets aggregate to form a plug
- Thromboplastin is released
- Coagulation cascade is triggered
This process ultimately seals off the injured area.
What initiates the heartbeat?
Sinoatrial (SA) node
It acts as the primary pacemaker of the heart.
What is the function of the atrioventricular (AV) node?
Receives impulses from the SA node and delays conduction
This delay allows the atria to contract before the ventricles.
What is the impulse travel time from the SA node to the AV node?
0.08s
What are non-SA autorhythmic tissues referred to as?
Latent pacemakers
What happens if the SA node is damaged?
The slower AV node assumes pacemaker activity
Where is the Atrioventricular (AV) node located?
At the base of right atrium near septum and just above junction of atria ventricles
What is one function of the AV node?
Delays the conduction of signals to give atria time to contract
What is the potential discharge rate of the AV node?
40-60 action potentials/min
What occurs if the AV node is damaged?
Complete heart block
What does the Bundle of His do?
Passes impulse from AV node to the bundle branches
What do the bundle branches of the Bundle of His do?
Travel down septum, around tip of ventricles
What is the potential discharge rate of the Purkinje fibres?
20-40 action potentials/min
What happens when Purkinje fibres become overly excitable?
They can become ‘lead engine’ and fire premature action potentials
What are common causes of ectopic focus in Purkinje fibres?
- Anxiety
- Lack of sleep
- Excess caffeine
- Nicotine
- Alcohol consumption
What is the resting membrane potential of atrial cells?
-80mV
What is the resting membrane potential of ventricular cells?
-90mV
What initiates depolarization in contractile cardiac cells?
Opening of voltage-gated Na+ channels
What occurs during the plateau phase of action potential in contractile cells?
K+ exits cell while Ca2+ slowly enters
What is the purpose of the plateau phase in cardiac action potentials?
Prevents tetany and allows full contraction
What happens during repolarization in cardiac action potentials?
Ca2+ channels close and K+ channels open
What is the cardiac cycle?
Pattern of contraction (systole) and relaxation (diastole) during one complete heartbeat
What occurs during atrial systole?
Both atria contract simultaneously and send blood into the ventricles
What happens during ventricular systole?
Blood is ejected from both ventricles simultaneously
What is the duration of atrial systole?
0.1s (100ms)
What closes the SL valves during ventricular diastole?
Pressure of blood in the arteries
What causes the ‘lub dub’ sound of the heartbeat?
Closing of the AV during ventricular systole and SL valves during diastole
What modifies the heart rate?
SNS and PSNS
What does the cardioaccelerator region stimulate?
Increases heart rate during stress
What neurotransmitter is released by sympathetic nerve fibers?
Noradrenaline (NE)
What does the cardioinhibitory region do?
Slows depolarizations and decreases heart rate
What is cardiac output (CO)?
Volume of blood pumped out by the heart in a given time period
How is cardiac output calculated?
CO = HR X SV
What happens to the heart during regular exercise?
- Heart gets larger
- Muscular wall becomes thicker and stronger
- Stroke volume at rest increases
What affects cardiac output?
- Blood pressure
- Peripheral resistance
What is the formula for blood pressure?
BP = CO X TPR
What is blood pressure?
Force of blood against a vessel wall
What is the mean arterial pressure (MAP)?
Average arterial pressure throughout one cardiac cycle
What is the formula to calculate MAP?
MAP = DP + 1/3 (SP-DP)
What does peripheral resistance affect?
Blood pressure
How does blood viscosity affect blood pressure?
Higher viscosity increases resistance and BP
What is the relationship between blood vessel length and blood pressure?
Longer vessels lead to greater resistance and greater BP
How does blood vessel radius affect resistance?
Smaller radius increases resistance
What is the role of the vasomotor centre?
Regulates blood pressure
What is a consequence of prolonged high blood pressure?
More prone to atherosclerosis and damage to blood vessels
What happens to blood pressure during exercise?
Increases due to higher cardiac output
