Circulatory system

What is hypovolaemic shock?

Low volume of blood

Reduced by 15-20%

What are three causes of hypovolemic shock?

Haemorrhage

Vomiting and diarrhoea

Severe burns

What is the most common cause of cardiogenic shock?

Myocardial infarction

What are the two effects of neurogenic shock on the cardiovascular system?

Vasodilation

Bradycardia

What is bradycardia?

Slow heart beat

What is the function of myocardial cells?

Generates electrical impulses for heart contraction

What are the five structures of the heart involved in cardiac conduction?

Sinoatrial node

Atrioventricular node

Atrioventricular bundle

Left and right bundle branches

Purkinje fibres

What is the source of cardiac contraction?

sinoatrial node

What causes the sinoatrial node to be self stimulating?

Electrically unstable causing it to depolarise

What is repolarisation?

Period of recovery of the Sinoatrial node

What is the function of the atrioventricular node?

Transmits signals from atria to ventricles

What is the function of the atrioventricular node delay?

Ensure atria are fully empty and ventricles start to fill

What is the atrioventricular bundle?

Mass of specialised conducting fibres dividing into left and right branches

How do electrical impulses through the ventricles?

Left and right AV bundles branch into Purkinje fibres directly supplying myocardial cells

What is cardiac diastole?

Atria fill with blood from superior vena cava and pulmonary veins

What is atrial systole?

Blood pressure forces AV valves open causes atrioventricular valves to open

Sinoatrial node depolarises

What is ventricular systole?

AV node carries impulses causing ventricles to contract

Blood pressure increases in ventricles forcing valves open and emptying blood

What does ECG stand for?

Electrocardiography

What does the ECG measure?

Electrical activity of the heart caused by polarisation

What are the five waves of a normal ECG trace?

P, Q, R, S, T

What does the p-wave represent?

Atrial depolarisation

What does the pr interval represent?

Atrioventricular node delay

What does the qrs complex represent?

Ventricular depolarisation causing ventricular contraction

What does the st segment represent?

Early ventricular repolarisation

What abnormalities can be detected in the st segment?

Ischemia

Infarction

What does the t wave represent?

Ventricular repolarisation

What does the qt interval represent?

Total ventricular activity

What could qt interval elongation indicate?

Increased risk of arrhythmias

What is ECG paper output speed?

Rate at which the machine produces a trace

How are blood pressure readings expressed?

Systolic pressure/diastolic pressure

What is the normal blood pressure reading?

120/80

Why are systolic and diastolic readings used?

Shows the highest rise and lowest point in arterial pressure

What is pulse pressure?

The difference between systolic and diastolic pressure

What are the three factors determining resistance to flow of fluids in vessels?

Diameter

Length

Viscosity of fluid

What is the main factor controlling blood flow?

Diameter of resistance vessels controlled by smooth muscle in tunica media and sympathetic nerves

What are the two factors determining blood pressure?

Cardiac output x peripheral resistance

How is cardiac output determined?

Stroke volume x heart rate

What is stroke volume?

Amount of blood ejected from ventricles with each beat

What is heart rate?

Rate of cardiac cycle measured in beats per minute

What is peripheral resistance?

Blood pumped into closed circulatory system against blood pressure already there

What is auto regulation?

Ability of an organ to control its own blood flow through local vasolidation or vasoconstriction

What three organs have higher blood flow?

Brain

Kidney

Liver

What are the four mechanisms causing local vasodilation?

Increased metabolic waste production

Increased tissue temperature

Hypoxia

Local vasodilator chemical release

What are the two methods of blood pressure control?

Short term

Long term

What is the cardiovascular centre?

Collection of interconnected neurons responsible for cardiac output and blood pressure

What are three sources of impulses to the cvc?

Baroreceptor and chemoreceptors

Higher centres in the brain

What are baroreceptor?

Receptors in sinuses which sense stretch of blood vessels

What are the two ways the CVC lowers blood pressure?

Increases parasympathetic activity

Reduces sympathetic tone, causing vasodilation

What are the two main systems of long term blood pressure regulation?

Renin Angiostensin Aldosterone system and antiduretic hormone to increase water absorption