1.1 The Cardiovascular system Flashcards
Define myogenic
the capacity of the heart to generate its own impulses
What is the cardiac conduction system
A group of specialised cells located in the walls of the heart which send electrical impulses to the cardiac muscle causing it to contract
What is the order of the cardiac conduction system
Sinoatrial node, atrioventricular node, bundle of his, bundle branches, purkinje fibres
What is the function of the sinoatrial node
Generates the electrical signal that causes the heart to beat
What is the function of the atrioventricular node
Delays the impulse for approximately 0.1 seconds to allow for the atria to fully contract
What is the function of the bundle of his
Transmits impulses from the atrioventricular node to the ventricles via the bundle branches
What is the function of the purkinje fibres
Fibres that conduct impulses in the walls of the ventricles
What is diastole
The phase of the heartbeat where the heart relaxes and allows the atria to fill with blood
What is systole
The phase of the heartbeat where the heart contracts
What two parts is the neural control mechanism made up of
The sympathetic and parasympathetic nervous systems
Where is the cardiac control centre located
The medulla oblongata
What is the sympathetic nervous system
The part of the autonomic nervous system that speeds up heart rate
What is the parasympathetic nervous system
The part of the autonomic nervous system that decreases heart rate
What is the medulla oblongata
The most important part of the brain that regulates vital processes such as breathing rate and heart rate
What are the two parts of the nervous system
The central nervous system (CNS) and the peripheral nervous system
What does the central nervous system consist of
The brain and the spinal chord
What does the peripheral nervous system consist of
Nerve cells that transmit information to the CNS
What 3 receptors stimulate the cardiac control centre
Chemoreceptors, baroreceptors and proprioceptors
What do chemoreceptors detect
Chemicals changes / changes in blood acidity caused by an increase or decrease in carbon dioxide. During exercise they detect an increase in carbon dioxide
Where are chemoreceptors found
In the carotid arteries and the aortic arch
What does an increased concentration of carbon dioxide in the blood cause
It cause the sympathetic nervous system to be stimulated so the heart will beat faster
What does an decreased concentration of carbon dioxide in the blood cause
It cause the parasympathetic nervous system to be stimulated so the heart will beat slower
What do baroreceptors detect
Changes in blood pressure
What are baroreceptors
Special senors in tissues in the aortic arch, carotid sinus, heart and pulmonary vessels that respond to changes in blood pressure.
What does an increase in blood pressure cause to happen
It causes the parasympathetic nervous system to be stimulated so heart rate will decrease
What does a decrease in blood pressure cause to happen
It causes the sympathetic nervous system to be stimulated so heart rate will decrease
What are proprioceptors
Sensory nerve ending in the muscles, tendons and joints that detect muscles movement
What do proprioceptors detect
Muscle movement
During exercise how will proprioceptors respond
They will detect an increase in muscles movement. These receptors then send an impulse to the medulla which then send a message to the sympathetic nervous system which causes heart rate to increase.
What is a hormonal control mechanism
Hormones such as adrenaline can also affect heart rate. Adrenaline is a stress hormone and when released it stimulates the sinoatrial node which causes an increase in the speed and force of the contractions therefore increasing cardiac output
What is the impact of physical activity on stroke volume
A slight increase due
What is the impact of physical activity on heart rate
A large increase
What is the impact of physical activity on cardiac output
A large increase
What is stroke volume
The volume of blood pumped out by the heart in each contraction
What 3 factors can alter stroke volume
Venous return, the elasticity of cardiac fibers and the contractility of cardiac tissue
What is ejection fraction (%)
amount of blood pumped out of the ventricle / total amount of blood in the ventricle
What is heart rate
the number of times the heart beats per minute
What is cardiac output
The volume of blood pumped out of the heart per minute
Q = SV x HR
What is cardiac hypertrophy
When the heart gains cardiac muscle and therefore becomes bigger and stronger so can pump more blood per contraction
What is bradycardia
A decrease in resting heart rate to below 60 bpm
What is anticipatory rise
A rise in heart rate prior to exercise caused by adrenaline stimulating the sinoatrial node
How do you calculate maximal heart rate
220 - age
What is atherosclerosis
When arteries harden and narrow as they become clogged by fatty deposits
What is atheroma
A fatty deposit found in the inner lining of an artery
What is angina
Chest pain that occurs when the blood supply through the coronary arteries to the muscles of the heart is restricted
Define blood pressure
The force exerted by the blood on the wall of a blood vessel
What can be the consequences of high blood pressure
Increased risk of heart attack, heart failure, kidney disease, stroke or dementia
How can you reduce blood pressure
Regular aerobic exercise
What are the two types of cholesterol
- LDL (low density lipoprotiens) that transport cholesterol in the blood back to the heart. Classed as the bad cholesterol.
- HDL (high density lipoprotiens) that transport excess cholesterol to the liver where it is broken down. Classed as the good cholesterol.
What are the two main types of stroke
- Ischaemic (occur when a blood colt stops the blood supply)
- Haemorrhagic (occur when a weakened blood vessel supplying blood to the brain bursts)
What is cardiovascular drift
During steady state exercise heart rate does not remain the same but instead steadily climbs.
Describe cardiovascular drift
- CV drift is characterised by a progressive decrease in stroke volume and arterial blood pressure counteracted by a progressive rise in heart rate.
- It occurs during prolonged exercise (more than 10 mins) in a warm environment
Why does cardiovascular drift occur
When we sweat a portion of this lost fluid come from blood plasma. This decrease in plasma will reduce venous return and stroke volume. Therefore heart rate increases to compensate and to allow the performer to maintain a high cardiac output
What is a typical reading for blood pressure
120 mmHg /80
What is systolic pressure
The pressure in the arteries when the ventricles are contracting
What is diastolic pressure
The pressure in the arteries when the ventricles are relaxing
What is venous return
The return of blood to the right side of the heart via the vena cava
How much of the blood is contained in the veins at rest (%)
Up to 70%
What are the 3 venous return mechanisms
- The skeletal muscle pump
- The respiratory pump
- Pocket valves
Why are venous return mechanisms needed
The pressure in the veins is very low sue to the large lumen so it can be difficult to return blood to the heart
How does the skeletal muscle pump work
When muscles contract they change shape. This causes the muscles to push down on the walls of the veins, causing a pumping effect, squeezing the blood back towards the heart.
How does the respiratory pump work
When muscles contract and relax during inspiration and expiration the pressure in the thoracic and abdominal cavities changes. These changes in pressure compress the nearby veins assisting blood return to the heart.
How do pocket valves aid venous return
They prevent the back flow of blood when there is the low pressure, and therefore keep blood moving in one direction, back to the heart.
What are the 3 additional factors that aid venous return
- A thin layer of smooth muscle in the walls of the veins helps to squeeze blood back to the heart
- Gravity helps blood to return from the upper body
- the suction pump action of the heart
What are the impacts of blood pressure on venous return
- When systolic pressure increases there is an increase in venous return
- When diastolic pressure increases and systolic pressure decreases there is a decrease in venous return
What is the equation for the impact of a pressure gradient between the right atrium and the vena cava
Venous pressure (Pv) - right atrial pressure (Pra)
_____________________________________
Venous vascular resistance (Rv)
What is the role of haemoglobin in the transportation of oxygen
During exercise, when oxygen diffuses into the capillaries, supplying the skeletal muscle. 3% dissolves into plasma and 97% combines with haemoglobin to form oxyhaemoglobin. When fully saturated haemoglobin will carry 4 oxygen molecules. This occurs when the partial pressure of oxygen is high.
What is oxyhaemoglobin dissociation
At the tissues oxygen is released from the oxyhaemoglobin due to the lower pressure of oxygen that exists there. This is called oxyhaemoglobin dissociation.
What is the role of myoglobin in the transportation of oxygen
In the muscle oxygen is stored by myoglobin. This has a higher affinity for oxygen and will store oxygen for the mitochondria until it is used by the muscles.
