Physical Education (Section A) 1.1 Cardiovascular System

Chemoreceptors

Tiny structures that detect changes in the blood acidity caused by an increase or decrease in carbon dioxide levels

Baroreceptors

Respond to changes in the blood pressure to either increase or decrease heart rate

Proprireceptors

Sensory nerve endings in the muscles, tendons and joints that detect changes in muscle movement

Sympathetic nervous system

Increases the heart rate

Parasympathetic nervous system

Decreases the heart rate

Venous return

The volume of blood returning to the heart via the veins

Ejection fraction

The percentage of blood pumped out by the left ventricle per beat

Starlings law

Greater the venous return, increase in diastolic pressure, cardiac muscle stretches, greater strength of contraction, increased ejection fraction

Skeletal muscle pump

When muscles contract and relax they change shape, this change in shape means that the muscles press on the nearby veins and causes a pumping effect that pushes the blood toward the heart

Respiratory pump

When the muscles contract or relax during respiration pressure changes occur in the thorax (chest), these pressure changes compress the nearby veins and push blood back into the heart

Pockets valves

Prevent back-flow of blood, but allow blood through in the direction of the heart

Smooth muscle

Contract and push blood back towards the heart

Gravity

Aids venous return of blood areas above the heart

Suction pump action

The suction of blood to the atrium naturally draws blood in

Bohr shift graph

During exercise the oxyhemoglobin dissociation curve shifts to the right, this is because the muscles require more oxygen the dissociation of oxygen from haemoglobin in the blood capillaries to the muscle tissues occlusion ore readily

Oxyhemoglobin dissociation curve

S-shaped curve, lungs is almost full saturation (concentration) of haemoglobin but at the tissues partial pressure of oxygen is lower

Bohr shift

When an increase in blood carbon dioxide and a decrease in pH results in a reduction of the affinity of haemoglobin for oxygen

Bohr affect

• reduction in blood pH (increased acidity)

• Increased partial pressure of carbon dioxide

• Increased blood pressure

Stroke volume

The amount of blood ejected by the heart per beat (ml)

Heart rate

The number of times the heart beats per minute (BPM)

Cardiac output

The amount of blood ejected from the heart per minute (L/min or ml/min)

Cardiac output equation

Heart rate x stroke volume = cardiac output

Diastole stage

Atrium and ventricles relax, allows blood to flow through the tricuspid and bicuspid valves, no blood leaves the heart due to the semilunar valves being closed, around 80% of blood is already in the ventricles at this point

Systole stage

Atrium and ventricles contract pushing blood out the heart, semilunar valves opened therefore force the blood out through the pulmonary artery and aorta, tricuspid and bicuspid valves are shut to ensure no back-flow occurs

Blood pressure

The force exerted by the blood against the blood vessel wall

Systolic stage

Heart contracts, forcing blood out at a higher pressure

Diastolic stage

Heart relaxes, blood flows at a lower pressure

Myogenic

The heart has the capacity to start its own electrical impulse

Sino-atrial node

Sends an impulse through the walls of the atria causing the muscular walls to contract

Atrioventricular node

Delays the impulse (around 0.1 second), enabling the ventricle to fill with blood

Bundle of His

Passes impulse from AVN to the perkinje fibres

Purkinje fibres

Impulse stimulates the ventricle to contact and blood is pumped out the ventricles

Vascular shunting

The redistribution of cardiac output to where oxygen is needed most

Vasodiation

The widening of the blood vessels to increase the flow of blood to the capillaries

Medulla oblongata, decrease SNI

Causes both vasodilation to the blood vessels and the opening of the pre-capillary sphincters surrounding the working muscles

Vasoconstriction

The narrowing of the blood vessels to reduce blood flow into the capillaries

Medulla oblongata, increased SNI

Both vasoconstriction to the blood vessels and the closing of the pre-capillary sphincters surrounding the non-essenical organs

Veins

Transport deoxygenated blood from the heart to the lungs and oxygenated blood back to the heart, thy have thinner muscle/elastic tissue layers, contain blood at low pressure, have valves and a wider lumen

Arteries

Transport oxygenated blood around the body, have the highest pressure, thick elastic outer walls, and have thick layers of muscle, a smaller lumen and smooth inner layer

Capillaries

Tiny lumen, are only wide enough to let one red blood cell to pass at a given time, slowing the blood flow and allows exchange of nutrients with the tissues to take place by diffusion, one cell thick for quick diffusion

Transport of oxygen

3% dissolves in the plasma

97% combines with haemoglobin to form oxyhaemoglobin

Haemoglobin

Protein responsible for transporting oxygen into the blood

Saturation

Percentage of the haemoglobin that is filled with oxygen

Myoglobin

Protein responsible for storming oxygen into the muscle tissue

Dissociation

The process where oxygen is released from the haemoglobin

Partial pressure

The number of oxygen molecules within a given space

Affinity

The degree to which oxygen binds to the protein

Cardiovascular drift

Characterised by a progressive decrease in stroke volume and arterial blood pressure, together with a progressive rise in heart rate

Hormonal control mechanism

Hormone adrenaline released form adrenal glands when stressed, when nervous before an event adrenaline is released cashing a rise in heart rate (this is the anticipatory rise)

Adrenaline activates

Adrenaline goes to the sino-atrial node and activates the SNS