PE AQA PHED 1 CARDIOVASCULAR SYSTEM

MYOGENIC - The heart produces its own electrical impulses involuntary.

PATHWAY OF CARDIAC IMPULSES

• SA NODE (Sinoatrial node)
• AV NODE (Atrioventricular node)
• HIS FIBRES
• PURKINJE FIBRES
• THEN AROUND THE HARD TO CONTRACT.

CARDIAC CYCLE

DIASTOLE

• AV and SA valves are both closed.
• The atriums begin to fill with blood coming from the pulmonary vein.
• Increase filling of blood increases the pressure placed against the AV valves.

ATRIAL SYSTOLE

• AV valves open due to an increase pressure in the atriums.
• Blood begins to enter the ventricles.
• Increase filling of blood increases pressure paced against the SA valves.

VENTRICULAR SYSTOLE

• The AV valves cloe whilst the SA valves open
• Blood begins to leave from the left ventricle via the pulmonary artery
• Blood is then taken away to the rest of the body.

CONTROL OF THE HEART RATE

• Cardiac control centre located in the medulla oblongata
• Consists of the sympathetic nerve, which increases heart rate and the parasymathetic nerve, which decreases heart rate.

HORMONAL CONTROLS

• Adrenaline and Noradrenaline which are released by the adrenal gland, this increases heart rate and helps to vasoconstrict blood vessels.
• Acetylcholine, released by parasympathetic nerves, reduces heart rate.

NEURAL CONTROLS

• PROPRIOCEPTORS: Detects movement in the muscles and the joints, which increases the heart rate.
• CHEMORECEPTORS: Detects an increase in blood pH levels, for example, an increase in lactic acid or carbon dioxide.
• BARORECPTORS: Detects a change in blood pressure, increase blood pressure increases the heart rate.

STROKE VOLUME

• The volume of blood that is ejected from the left ventricle per beat.
• linearly increases as intentsity of exercise increases.
• Plateaus…