3.1.1.2 Cardiovascular system

Right atrium

Receives deoxygenated blood from vena cava

Right ventricle

Pumps blood to lungs via pulmonary artery

Left atrium

Receives oxygenated blood via pulmonary vein

Left ventricle

Thick muscled chamber that pumps blood to the rest of the body via the aorta

Cardiac control system

Network of specialised cells that generate impulses to form a heartbeat

Myogenic

The capacity of the heart to generate its own impulse

SA node

Mass of cardiac muscles in the atrium that generates a heartbeat by causing atrial systole

AVN node

Relays impulse but delays for 0.1 seconds to allow for the atrium to empty before ventricular systole

Bundle of His

Specialised fibres that transmit signals by branching to the ventricles

Purkinje fibres

Muscle fibres conduct impulses to ventricular walls to cause contraction

Medulla oblongata

The cardiac control centre that regulates heart rate

Adrenaline

Stress hormone from sympathetic nerves that stimulates SAN

Cardiac output

Volume of blood pumped per minute HR X SV

Starlings law

Increase in venous return means greater diastolic filling. This stretches cardiac muscles which generates a stronger force of contraction and increased ejection faction

Ejection faction

Percentage of blood pumped by left ventricle

Features of arteries

Thick muscular walls to withstand pressure

Elastic tissue to allow stretching

Narrow lumen to maintain pressure

Features of veins

Thin walls for low pressure

Wide lumen to allow large volumes of blood

Valves to prevent back flow

Features of cappalries

One cell thick to allow diffusion

Very narrow lumen to allow one RBC at a time to diffuse

Many capillaries means large surface area

Redistribution of blood methods

Vasoconstriction and Vasodilation

Vasodilation

Arteries supplying muscles increase in diameter to deliver oxygen/glucose

Venous return mechanisms

Skeletal pump, Valves, Respiratory pump

Skeletal pump

Muscles contract to compress the veins and increase the pressure to move blood towards the heart, relaxation and contraction creates pumping action

Respiratory pump

Diaphragm contracts and moves down to increase abdominal pressure and suck venous blood into right atrium during inspiration, Diaphragm relaxes and rises to decrease abdominal pressure and push bloop upwards towards heart during expiration. Causes a pumping effect

Oxyhaemoglobin

4 oxygen molecules bind to haemoglobin to saturate it. Occurs in lungs due to high partial pressure

Oxyhemoglobin dissociation

Oxygen released at muscles due to low partial pressure

Myoglobin

High affinity for O2 so stores in muscles and transports O2 to mitochondria for aerobic respiration

Bohr shift

Oxyhemoglobin curve shifts right due to increased CO2 content of blood

A-V O2 difference

Difference in oxygen content of arterial and venous blood which increases during exercise due to muscles extracting all available oxygen

Variation between trained and untrained athletes for A-V O2 difference

Much higher difference at all intensities of exercise for trained athletes due to more capillaries, mitochondria and myoglobin from training to extract oxygen out of the blood

How does each training adaption improve A-V O2 difference

Increased capillarisation increase diffusion (shorter distance, greater surface area), Increased mitochondrial density allows more sites for aerobic respiration/utilisation, Increased myoglobin content improves transportation of oxygen to the mitochondria

Acute responses to exercise

Anticipatory rise, Increased stroke volume, Systolic blood pressure increases

Long term impacts of training

Cardiac hypertrophy, Bradycardia, Increased vasodilation capacity, Increased RBC content

Cardiovascular drift

Occurs 10-20 mins after exercise. Stroke volume decreases but fluid lost from sweat reduces blood plasma and makes it more viscous. This decreases the venous return and requires an increased cardiac output to cool the body

Atherosclerosis

Arteries harden and narrow when clogged by fatty deposits

Atheroma

Fatty deposit found in inner lining of artery

Angina

Chest pain when blood supply through arteries is restricted