Cardiovascular System

Coronary Heart Disease

Arteries supplying oxygenated blood to heart blocked / narrowed (Artherosclerosis) by fatty deposits (Atheroma).

Symptoms - pain / discomfort from lack of oxygen (angina).

Detached atheroma -> blocks artery -> heart attack.

Cholesterol levels - 2 types?

(Regular physical activity lowers bad LDL cholesterol levels and increases good HDL cholesterol levels.)

LDL (low density lipoproteins) = 'bad' cholesterol in blood transported to tissues, linked to heart disease.

HDL (high density lipoproteins) = 'good' cholesterol in blood transported to liver for break down, less risk of heart disease.

Stroke = occurs when blood supply to part of the brain is cut off, causing damage to brain cells, leads to disabilities and death.

2 main types of strokes are?

Ischaemic strokes - (common) occur when blood clot stops blood supply.

Haemorrhagic strokes - occur when weakened blood vessel supplying brain bursts.

What is Cardiac Output?

Hint : Q = SV x HR

Cardiac Output (Q) = volume of blood ejected from the heart per minute.

Q ranges from 4-5 L at rest to 20-30 L during exercise.

Training may increase 'exercising Q' to 35-40 L.

What is the Anticipatory rise?

Thoughts / nerves prior to exercise releases adrenaline (hormone). This in turn increases heart rate / breathing rate which is controlled by the medulla oblongata.

How does the redistribution of blood during exercise work?

The arterioles supplying muscle fibres are able to dilate and constrict.

• Increase in volume of flowing blood during exercise.

• Increased acidity in blood.

• detected by chemoreceptors, information to Medulla.

• Sympathetic nerve impulses to rings of muscle around arterioles, pre-capillary sphincters.

Why does the acidity of blood increase during exercise?

CO2 is produced as a waste product of exercising muscles. The CO2 produced dissolves in the blood, producing a weak acid - Carbonic Acid.

Why does Vasodilation occur?

• Vasodilation to exercising muscles and heart = deliver more oxygen.

• Vasodilation to skin arterioles = cooling mechanism.

• Vasoconstriction to kidneys, liver, digestive system = they have reduced importance.

• No change in supply to Brain = still working and needs oxygen.

The Heart = two sided pump.

What do the two sides do?

Right side = pumps blood to our lungs to collect oxygen.

Left side (BIGGER) = pumps blood to muscles to deliver oxygen to body.

Structure of the Heart

Left and right halves - separated by a septum.

The pumping parts are the ventricles.

Blood collects into the atria.

Heart beat - the chambers of the heart can contract and relax. What is this called?

Contraction = systole

Relaxation = diastole

The atria and ventricles contract at different times during a single beat - a cardiac cycle.

The Cardiac Cycle - 3 steps.

Diastole -> Atrial Systole -> Ventricular Systole (Repeats)

Parasympathetic nervous system VS sympathetic nervous system

Sympathetic nervous system (SNS) mobilises the body for action. For example by increasing Cardiac output, accelerating respiratory rate etc.

Parasympathetic nervous system (PSNS) conserves and restores - slows heartbeat, decreases respiratory rate, stimulates digestion etc.

SO... SNS = 'fight or flight' response.

PSNS = 'rest and digest' state.

How does increased acidity in the blood lead to an increase in heart rate?

The increased levels of (Carbonic) acid in the blood is detected by Chemoreceptors which send impulses to the medulla. This signals the medulla of the need for an increased heart rate, so more nerve impulses are sent along the Sympathetic nerve to the heart, and less impulses are set along the Parasympathetic Vagus nerve to the heart. The cardiac cycle is then started by the Sino-atrial node (SA node) / pacemaker in the right atrium. The electrical stimulus from the SA node spreads along the wall of the atria causing atrial systole. Next, the atria-ventricular node (AV node) in the right atrium picks up the impulse. It is then transferred to the ventricles via the bundle of His. The bundle of His divides into left and right branches and the branches spread into the heart muscle by a network of Purkinje fibres. Impulses from the Purkinje fibres cause the walls of the ventricles to contract.