3.1.1 - APPLIED ANATOMY AND PHYSIOLOGY

Anticipatory rise

An increase in heart rate prior to exercise, due to the release of adrenalin

Arterio-venous oxygen difference (A-VO2 diff)

The difference in the oxygen content of the blood between the arterial blood and the venous blood

Blood pressure

Blood pressure is a measure of the force that your blood exerts against blood vessel walls.

• Systolic blood pressure: Blood pressure while the heart is contracting.

• Diastolic blood pressure: Blood pressure while the heart is relaxing.

• High blood pressure can occur for many reasons including obesity; eating too much salt; stress; or smoking. It increases the risks of heart attack and stroke.

Bohr shift

The Bohr shift is when an oxyhaemoglobin dissociation curve moves to the right during

exercise. An oxyhaemoglobin dissociation curve correlates the oxygen saturation of

haemoglobin across a range of oxygen pressures.

The Bohr shift occurs as a result of increased CO2 in the blood; increased blood acidity;

decreased blood pH; and increased temperature. As a result, haemoglobin has a lower affinity for oxygen at working muscles, giving up oxygen more easily.

Bradycardia

A reduction in resting heart rate rate below 60 beats per minute

Cardiac conduction system

A group of specialised cardiac muscle cells in the walls of the heart that send signals to the heart

muscle, causing it to contract. The main components of the cardiac conduction system are:

• Sino-atrial node (SAN), the heart’s pacemaker, which sends an impulse through the atria causing them to contract.

• Atrio-ventricular node (AVN) which delays the impulse to allow ventricular filling.

• Bundle of His which conducts the impulse down the septum.

• Purkinje fibres spread the impulse through the ventricles causing them to contract.

Sino-atrial node

Sino-atrial node (SAN), the heart’s pacemaker, which sends an impulse through the atria causing them to contract.

Atrio-ventricular node

Atrio-ventricular node (AVN) which delays the impulse to allow ventricular filling.

Bundle of his

Bundle of His which conducts the impulse down the septum.

Purkinje fibres

Purkinje fibres spread the impulse through the ventricles causing them to contract.

Cardiac hypertrophy

Increase in thickness of the muscular heart wall, especially around the left ventricle. This increases the maximal strength of contraction. It may also make the size of the ventricular cavity bigger. These factors increase stroke volume.

Cardiac output

Cardiac output is the amount of blood which leaves the left ventricle per minute. It is calculated by multiplying heart rate and stroke volume.

Heart rate is the number of times the heart contracts per minute.

Stroke volume is the amount of blood which leaves the left ventricle per contraction.

Cardiovascular drift

A reduction in stroke volume when exercising in warm conditions for longer than 10 minutes.

Results in an increase in heart rate to maintain cardiac output.

Occurs due to sweating which reduces blood volume and increases viscosity. This decreases venous return which, in line with Starling’s law, decreases stroke volume.

Cholesterol - name the 2 types

Cholesterol is a type of fat which is transported in the blood. There are two types:

• High-density lipoproteins: ‘Good’ cholesterol which transports excess cholesterol to the

liver to be broken down. This lowers the risk of heart disease.

• Low-density lipoproteins: ‘Bad’ cholesterol as too much can result in fatty deposits developing in the arteries. This has a negative effect on heath increasing blood pressure, and the risk of heart disease.

Haemoglobin

Found in red blood cells. Haemoglobin combines with oxygen to form oxyhaemoglobin,transporting it around the body.

Heart disease

Also known as coronary heart disease. This occurs when coronary blood vessels become blocked by fatty deposits, called atheroma, limiting the supply of oxygenated blood to the heart. This process is known as atherosclerosis. The lack of oxygen results in discomfort, known as angina. If a compete blockage occurs, cutting off the blood supply, this can result in a heart attack.

Myoglobin

Found in muscle cells, myoglobin stores and transports oxygen. It has a higher affinity for oxygen than haemoglobin, so it aids transport into muscle cells

Receptors

Part of the nervous system that detects changes in the body. Types of receptors:

• Baroreceptors: Located in blood vessels, these detect changes in blood pressure.

• Chemoreceptors: Monitors and detects increases in blood acidity during exercise due to

increased carbon dioxide in the blood.

• Proprioceptors: Detect increases in muscle movement during exercise.

Redistribution of blood

The vascular shunt mechanism directs blood flow around the body. It does this using two

mechanisms:

• Vasodilation: Precapillary sphincters will relax, widening the internal diameter of blood vessels. During exercise this will happen in the vessels leading to working muscles allowing more oxygen and nutrient rich blood to reach them.

• Vasoconstriction: Precapillary sphincters will contract, decreasing the internal diameter of blood vessels. During exercise this will happen in the vessels leading to non-working muscles and non-essential organs eg digestive system. This allows more blood to be

available for the working muscles.

Starlings law of the heart

Increased venous return will result in a higher stroke volume. The is due to the cardiac muscle being stretched, resulting in a stronger force of contraction and greater ejection fraction.

Stroke

A stroke is a serious life-threatening medical condition that happens when the blood supply to part of the brain is cut off. There are two types of stroke:

• Ischaemic strokes occur when a blood clot stops the supply of blood reaching the brain.These are the most common type.

• Haemorrhagic strokes are the result of a weakened blood vessel to the brain bursting.

Sympathetic and parasympathetic nervous systems

The autonomic nervous system subconsciously controls heart rate, breathing rate and redistribution of blood, among other things.

Controlled by the Medulla Oblongata the sympathetic nervous system is the body’s ‘fight or flight’ system, speeding up heart rate; while the parasympathetic system is concerned with ‘rest and digest’, decreasing heart rate

Venous return mechanisms

The body has several mechanisms to return blood to the right side of the heart via the vena cava:

• Valves: Found in veins that prevent the backflow of blood.

• Skeletal muscle pump: Working muscles contract and compress veins to push blood back towards the heart.

• Respiratory pump: Increased respiration/changes in pressure in the thorax compress veins to push blood back towards the heart.

• Smooth muscle: Found in veins, smooth muscle contracts to push blood back towards the heart.

• Suction pump of the heart: As the heart relaxes it creates a vacuum which pulls blood back toward the heart.

Diffusion

The movement of gases from an area of high partial pressure to an area of low partial pressure.

Expiratory reserve volume

The volume of air which could be forcibly expired in addition to tidal volume.

Inspiratory reserve volume

The volume of air which could be forcibly expired in addition to tidal volume.

Minute ventilation

Volume of air inspired or expired per minute. Breathing rate x tidal volume.

Partial pressure

The pressure exerted by an individual gas in a mixture of gases.

Residual volume

The volume of air which must remain in the lungs after a maximal expiration. This is to prevent the lungs from collapsing.

Sympathetic and parasympathetic nervous systems

The autonomic nervous system subconsciously controls heart rate, breathing rate and redistribution of blood, among other things.

Controlled by the Medulla Oblongata the sympathetic nervous system is the body’s ‘fight or flight’ system, speeding up breathing rate; while the parasympathetic system is concerned with ‘rest and digest’, decreasing breathing rate.

Tidal volume

Volume of air breathed in or out per breath