Cardiovascular System Flashcards
What are myocytes?
Individual cardiac muscle cells
What are the contractile proteins?
- Actin
* Myosin
What two things are cells deprived of during cardiac arrest?
- Oxygen
* Glucose
What organs are the key components of the cardiovascular system?
- Lungs
- Heart
- Liver
- Gut
- Kidneys
What is the pericardium?
The fluid-filled sac around the heart that separates it from surrounding structures
Which circuit does the blood that enters the right side of the heart come from?
The systemic circuit
Which circuit does the blood that enters the left side of the heart come from?
The pulmonary circuit
What are the structures in each of the pumps in the heart?
Two chambers - an upper atrium and a lower ventricle
What do papillary muscles do?
They prevent inward movement of the tricuspid valve
Which valve prevents back flow of blood into the right ventricle?
The pulmonary semilunar valve
What attaches papillary muscles to both tricuspid and bicuspid valves?
Chordate tendinae
Which valve prevents back flow of blood into the aorta?
The aortic semilunar valve
What is the myocardium?
The muscular tissue of the heart
What is diastole?
The period between two contractions of the heart, when the heart muscle relaxes and the chambers fill with blood
What is atrial systole?
The period when the atria are contracted, forcing blood into the ventricles
What is ventricular systole?
The period when the ventricles are contracting
How long is an average cardiac cycle?
0.8 seconds
How many times a minute does the average heart beat?
75
What is systolic pressure?
The maximum pressure in the system
What is diastolic pressure?
The lowest pressure in the system
What is isovolumetric contraction?
The period during ventricular systole when both the atrioventricular valve and the semilunar valve are both closed and blood is trapped in the ventricles
During the peak period of isometric contraction, what is the pressure in the left ventricle?
Approximately 125 mmHg
During the peak period of isometric contraction, what is the pressure in the right ventricle?
25 mmHg
What is cardiac output?
The volume of blood pumped out of both ventricles per minute
On average, what is the cardiac output when a person is at rest?
5 litres min^-1
What is the highest that cardiac output can be?
About 25 litres min^-1
What is stroke volume?
The amount of blood pumped out of the heart during one beat
What is the formula to calculate cardiac output?
Cardiac output = stroke volume x heart rate
What is diastole?
Ventricular relaxation
What is systole?
Ventricular contraction
What is a distinctive characteristic of myocytes?
They can contract and relax independently of being within the heart itself
What is autorhythmicity?
The ability of the heart muscle to contract without input from a nerve stimulus
What is the sinoatrial node?
The group of cells in the wall of the right atrium which initiate the action potential responsible for the heartbeat
What is the atrioventricular node?
A group of specialised heart muscle fibres at the junction between the atria and ventricles which control contraction of the ventricles
What are Purkinje fibres?
Modified cardiac muscle fibres which are part of the atrioventricular bundle
What is normal sinus rhythm?
Resting heart rate
Which area of the brain regulates heart function?
The medulla
Where do the sympathetic nerves that innervate the heart originate and how do they reach the heart?
- In the cardioacceleratory centre of the brain
* Via the spinal cord
Which neurotransmitter is responsible for excitation of the heart?
Noradrenaline
Where do the parasympathetic nerves which innervate the heart originate and how do they travel to the heart?
- In the cardioinhibitory centre
* Via the vagus nerve
Which neurotransmitter do the parasympathetic fibres of the heart use?
Acetylcholine
Name some of the hormones which can increase heart rate?
- Noradrenalin
- Thyroxin
- Glucagon
What are the 3 components of blood?
- Erythrocytes
- Leukocytes
- Plasma
What is the haematocrit?
The ratio of red blood cells to the total volume of blood
What is serum?
The the remaining fluid in a blood sample after a clot has formed
What is serum comprised of?
- Plasma
* Clotting factors
What are the precursor cells to leukocytes, erythrocytes and platelets?
Haematopoetic stem cells
What is erythropoesis?
The production of erythrocytes
Which hormone is responsible for the production of platelets and where is that hormone produced?
- Thrombopoeitin
* The liver
Which hormone is responsible for the production of erythrocytes and where is that hormone produced?
- Erythropoietin
* Kidneys and liver
What are the 4 blood groups?
- A
- B
- AB
- O
What are agglutinogens?
The antigens expressed by erythrocytes
Are most people Rh-positive or Rh-negative?
Rh-positive
Is the production of antibodies to the Rh antigen an example of adaptive or innate immune system?
Adaptive
What is haemostasis?
The cascade of biomechanical reactions that lead to the cessation of bleeding
What are the three stages of haemostasis?
- Vascular spasm
- Platelet plug formation
- Blood clotting
What is vascular spasm?
Constriction of blood vessels at a wound site to slow bleeding
How is a platelet plug formed?
When platelets stick to the exposed collagen of a damaged blood vessel
What is thromboxane A2?
The hormone released by clumping platelets to further increase vasoconstriction
What is produced as a result of the blood clotting step of wound healing?
An insoluble fibrin mesh
Define the term haemorrhage
To lose a large amount of blood
What is elastic recoil?
The return (recoil) of the arterial wall during diastole
What is the formula for calculating resistance to blood flow?
Resistance = pressure gradient/blood flow
What is the thoroughfare channel?
A direct channel through a capillary bed
What are the components of plasma?
- Water
- Plasma proteins
- Nutrients
- Hormones
- Waste products
- Gases
What are the gases found in plasma?
- Oxygen
- Nitrogen
- Carbon dioxide
What nutrients are found in plasma?
- Glucose
- Amino acids
- Lipids
What proteins are found in plasma?
- Albumin
- Fibrinogen
- Globulins
What waste products are found in plasma?
- Lactic acid
* Nitrogenous waste from protein metabolism (urea) and nucleus acids (uric acid)
What is pulse pressure?
The difference between systolic and diastolic pressures
What are also known as capacitance vessels?
Veins
What is the purpose of veins being in skeletal muscles?
The contraction of the muscle compresses the veins which forces blood along them
What is peripheral resistance?
Resistance of the systemic circulation to blood flow
If the diameter of the blood vessel is reduced, will the flow rate be reduced?
Yes
Which nervous system is responsible for the contraction of smooth muscle?
Sympathetic
Which nervous system is responsible for the relaxation of smooth muscle?
Parasympathetic
What is auto regulation?
The local control of blood flow
What problems can occur when blood pressure is too high?
Vessels can be damaged and fluid can leak from capillaries
What can happen if blood pressure is too low?
Tissues and organs will be insufficiently per fused and there may be damage or organ failure
When does the highest value of blood pressure occur?
During systole (ventricular contraction)
When does the lowest value of blood pressure occur?
During diastole (ventricular relaxation)
How is mean arterial pressure calculated?
Diastolic pressure + (systolic pressure - diastolic pressure) / 3
How is blood pressure calculated?
Cardiac output x peripheral resistance
What are the two factors which determine cardiac output?
- Stroke volume
* Heart rate
Increasing cardiac output has what outcome?
Systolic and diastolic blood pressures are raised
Increasing stroke volume has what effect?
Systolic blood pressure is increased, rather than diastolic pressure
Peripheral resistance is largely determined by what?
The diameter of arterioles
What is the outcome of vasoconstriction?
Peripheral resistance increases, which causes an increase in blood pressure
What are baroreceptors?
Nerve endings which sense arterial blood pressure
Where are baroreceptors located?
In the aortic arch and the walls of the carotid arteries of the neck
How are baroreceptors activated?
When the arterial walls are stretched
What do baroreceptors do?
Detect changes in blood pressure, which is relayed to the cardioacceleratory and cardioinhibitory centres of the brain in order to influence the ANS
What are chemoreceptors?
Nerve endings which are sensitive to chemicals
What do chemoreceptors do?
Monitor levels of carbon dioxide and oxygen in the blood and are sensitive to acidity
What is the primary function of chemoreceptors? What else do they do?
- To regulate breathing
* During periods of severe cardiovascular disturbance they can influence cardiac output of the cardiovascular centres
What is hypertension?
Elevated levels of blood pressure
In 2015, how many deaths, globally, were due to high blood pressure?
10.4 million
What are the risk factors for high blood pressure?
- Alcohol intake
- Obesity
- Diabetes mellitus
- Family history
- African/Caribbean
- Smoking
- Sedentary lifestyle
- High salt intake
- Increasing age
What are the complications of high blood pressure?
- Blindness
- Stroke
- Heart attack/failure
- Atherosclerosis (blood vessel damage)
- Kidney failure
What causes atherosclerosis?
Deposits of lipids, cellular debris and calcium salts on the inside of artery walls
What are the two main possible complications due to atherosclerosis?
- Infarcation
* Ischaemia
What is infarction?
Death of tissue as a result of lack of blood supply
What is ischaemia?
Tissue damage as a result of lack of blood supply
What is atherosclerosis?
The degeneration of arteries through the gradual restriction of blood flow, caused by build-up of fatty material and plaque on arterial walls
What major blood vessels does atherosclerosis affect?
Coronary, cerebral and peripheral arteries
What are the types of material which atherosclerosis deposits on arterial walls?
- Lipids
- Cellular debris
- Calcium salts
What is the purpose of high-density lipoprotein?
To transport cholesterol from tissues to the liver
What is the purpose of low-density lipoprotein?
To transport cholesterol to the tissues
What are chylomicrons?
Droplets of fat present in blood or lymph which transport cholesterol and lipids from the lumen of the gut to the liver
What are statins?
Drugs to help lower cholesterol
How do statins work?
They inhibit production of cholesterol in the liver. This produces a gradient for low density lipoproteins to the liver, which removes their concentration in the blood
What is angina pectoris?
Pain caused by ischaemia in the heart muscle
What is myocardial infarction?
A disease state when blood flow to part of the heart is cut off. It is the main cause of heart failure
How do nitrovasodilators work?
- They produce nitric oxide, which is a vasodilator.
* They reduce venous return, which reduces ventricular end-diastolic volume and active distension of the heart wall
How do beta blockers work?
They reduce blood pressure and peripheral resistance by blocking effects of the sympathetic nervous system
How do calcium antagonists work?
They reduce blood pressure and peripheral resistance by relaxation of smooth muscle in blood vessels
What is angioplasty?
The widening of narrowed coronary arteries by using a balloon
What is a stent?
A metal tube used to widen a narrowed coronary artery
What is one of the hormones released into the blood by necrotic tissue after a myocardial infarction?
Troponin
Which has more significant consequences for heart function, ventricular or atrial fibrillation?
Ventricular fibrillation
Define fibrillation.
It is when the heart beats in a spontaneously chaotic manner
Via what does blood return from the systemic circuit to the heart?
The superior and inferior vena cava
Via what does blood return to the heart from the systemic circuit?
The superior vena cava and inferior vena cava
Where does the blood pass to after the right ventricle contracts?
The pulmonary artery
What is the pulmonary semilunar valve?
The valve which closes when the right ventricle relaxes, preventing blood flowing back into the right ventricle
Via the pulmonary vein, where does blood return to?
The left atrium
What separates the left and right sides of the heart?
The intraventricular septum
What are the steps in the cardiac circuit?
Heart > Arteries > Arterioles > Capillaries > Venules > Veins > Heart
What are the three stages of the cardiac cycle?
- Diastole
- Arterial Systole
- Ventricular Systole
Which part of the nervous system controls the heart and blood vessels?
The ANS
Which circuit does the blood which is ejected from the left ventricle supply?
The systemic circuit
Which circuit does the blood which is ejected from the right ventricle supply?
The pulmonary circuit
What processes happen as a result of blood flow through the pulmonary circuit?
Blood taking up oxygen and releasing carbon dioxide
What processes happen as a result of blood flow through the systemic circuit?
Oxygen is delivered to cells and carbon dioxide is taken up
In an ECG, what is represented by the P waves?
Atrial depolarisation
In an ECG, what is represented by the PR interval?
The time taken for electrical activity to move between atria and ventricles
In an ECG, what is represented by the QRS complex?
The depolarisation of the ventricles
In an ECG, what is represented by the ST segment?
Ventricular contraction
In an ECG, what is represented by the QT interval?
The time taken for the ventricles to depolarise, then repolarise
In an ECG, what is represented by the R wave?
Ventricular depolarisation
In an ECG, what is represented by the T wave?
Ventricular depolarisation
In an ECG, what is represented by the ST segment?
If it is not a flat line, any myocardial infarction
What is the sinoatrial node?
A group of cells embedded in the wall of the right atrium which initiate the wave of depolarisation that causes the heart to contract
What is the atrioventricular node?
A group of specialised heart muscle fibres which control the contraction of the ventricles
Which areas of the heart are innervated by the sympathetic nervous system?
The sinoatrial and atrioventricular nodes
