Cardiovascular System

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Cardiovascular System by Mind Map: Cardiovascular System

1. conducting system of the heart

1.1. Direction of impulse

1.1.1. Superior Vena Cava

1.1.2. Sinoatrial (SA) Node

1.1.3. Atrioventricular (AV) Node

1.1.4. Atrioventricular bundle (AV) bundle / bundle of His

1.1.5. Left Atrioventricular (LAV) bundle

1.1.6. network of Purkinje Fibres

1.2. posses the property of autorhythmicity (generates its own electrical impulses and beats independently of nervous or hormonal control)

1.2.1. Heart rate supplied with both sympathetic and parasympathetic nerve fibres sympathetic increases heart rate parasympathetic decreases heart rate other factors affecting heart rate are Heart responds to circulation hormones eg Adrenaline and thyroxine

1.3. small groups of specialised neuromuscular cells in the myocardium initiate and conduct impulses

1.3.1. causes coordinated and synchronised contraction of the heart muscle

1.4. Sino atrial (SA) node

1.4.1. is a small mass of specialised cells that lies in the wall of the right atrium

1.4.2. these cells generate these regular impulses because they are electrically unstable this instability leads them to discharge (depolarise) regularly around 60 to 80 times a minute this dispoloarisation is followed by recovery (repolarisation) because this node discharges quicker than any other part of the heart it normally sets the heart rate and is often referred to as the pacemaker

1.5. Atrioventricular (AV) node

1.5.1. is a small mass of neuromuscular tissue situated in the wall of the atria septum near the atrioventricular valves

1.5.2. normally merely transmits electrical signals from the atria to the ventricles there is a 0.1 second delay here to pass through the ventricles allows atria to finish contracting before ventricles start

1.5.3. has a secondary pacemaker function takes over this role if there is a problem with the SA node or with transmission of impulses from the atria discharges around 40-60 times a minute

1.5.4. atrioventricular bundle bundle (AV bundle / bundle of HIS) this is a mass of specialised fibres that originate from the AV node it divides into the right and left bundle branches withing the ventricular myocardium the branches break up into fine fibres called the purkinje fibres these fibres transmit electrical impulses from the AV node to the apex of the myocardium where the wave of ventricular begins pumping blood into the pulmonary artery and the aorta

2. Direction of blood flow

2.1. Inferior vena cava

2.1.1. largest veins of the body

2.2. Superior vena cava

2.2.1. largest veins of the body

2.3. Right Atrium

2.3.1. and left atrium both contract at the same time

2.3.2. walls are thinner assisted by gravity to pump blood to ventricles

2.4. Tricuspid Valve / Right atrioventricular valve

2.5. Right Ventricle

2.5.1. and left ventricle simultaneously contract after the artias

2.5.2. walls are thicker work against gravity to pump blood into pulmonary artery and to the lungs

2.6. Pulmonary Valve

2.6.1. formed by 3 semilunar cusps

2.6.2. prevents backflow of blood to the right ventricle when it relaxes

2.7. Pulmonary Arteries

2.7.1. left carry venous blood to the lungs CO2 excreted O2 absorbed

2.7.2. right carry venous blood the the lungs CO2 excreted O2 absorbed

2.8. Lungs

2.9. Pulmonary Veins

2.9.1. two pulmonary veins from each lung

2.9.2. carr oxygenated blood back to theheart

2.10. Left Atrium

2.10.1. and right atrium both contract at the same time

2.10.2. walls are thinner assisted by gravity to pump blood to ventricles

2.11. Mitral Valve / Left atrioventricular valve

2.12. Left Ventricle

2.12.1. and right ventricle simultaneously contract after the artias

2.12.2. walls are thicker work against gravity to pump blood into aorta and round the body

2.13. Aortic valve

2.13.1. formed by 3 semilunar cusps

2.14. Aorta

2.14.1. first artery of general circulation

3. Arteries, Veins and Capillaries

3.1. Arteries

3.1.1. Have 3 layers Tunica intima / Inner layer; Endothelium Tunica media / Middle layer; Smooth muscle and Elastic tissue More Elastic tissue than smooth muscle Tunica adventitia / Outer layer; Fibrous tissue

3.1.2. Have thick walls needed to withstand the the high pressure blood flow means when cut blood spurts out

3.1.3. Arteries = Away from the heart

3.1.4. Types of artery Arterioles Small arteries 3 Layers also know as resistance vessles Anastomoses Form a link between main arteries supplying an area eg palm of the hand, soles of the feet or brain can provide collateral circulation provide adequate blood supply when artery is occluded End arteries Sole source of blood supply to tissues eg central artery to the retina of the eye when occluded tissue it supply dies as no alternative blood supply

3.1.5. Main arteries Renal kidney Hepatic liver and gall bladder Gastric Stomach Splenic spleen and pancreas Carotid neck and brain Coronary heart Peripheral limbs

3.2. Veins

3.2.1. 3 layers Tunica intima / Inner layer; Endothelium Tunica media / Middle layer; Smooth muscle and Elastic tissue not as much as in arteries as they don't need to stretch Tunica adventitia / Outer layer; Fibrous tissue

3.2.2. Have thin walls withstand the low pressure blood when cut slow, steady blood flow escapes

3.2.3. Veins = Carry blood towards the heart

3.2.4. also know as capacitance vessels distensible have capacity to hold a large proportion of the bodies blood 2/3 of the body's blood is in the venous system allows vascular system to absorb sudden changes in blood volume

3.2.5. Have valves prevent backflow ensuring blood flows to the heart assisted by skeletal muscles surrounding the veins formed by fold of endothelium and strengthened by connective tissue semilunar in shape concave toward the heart abundant in veins of the limbs especially lower limbs where blood has to travel a considerable distance against gravity absent in very small and very large veins in the thorax and abdomen

3.2.6. types of vein venules small veins

3.3. Capillaries

3.3.1. Wall consists of one single layer of endothelial cells allows water and other small molecules pass through it blood cells and plasma proteins are usually too big to pass through the capillary wall

3.3.2. form a network that joins small arterioles to small venules

3.3.3. they are the site of exchange of substances between the blood and tissue fluid that bathes the body cell

3.3.4. Entry capillary beds are guarded by precapillary sphincters (rings of smooth muscle) they direct blood flow Hypoxia (low oxygen levels in the tissue) and high levels of tissue waste dilate the sphincters this increases blood flow through affected beds

3.3.5. types of capilllary Sinusoids significantly wider and leakier capillaries found in the liver and bone marrow walls are incomplete and have larger lumens than normal can come directly into contact with cells outside sinusoid walls

3.3.6. capillary refill time when area of skin is pressed it turn white because blood has been squeezed out the capillary should take less than 2 seconds for capaillary to refill (skin to turn pink again) if takes longer can suggest poor perfusions or dehydration

4. Control of blood vessel diameter

4.1. Baseline, Vasoldilation and vasoconstriction

4.1.1. vasodilation caused by decrease nerve stimulation relaxes the smooth muscle thinning the vessel wall and enlarging the lumen increase blood flow at low pressure

4.1.2. Baseline (resting)

4.1.3. sympathetic activity / Vasoconstriction diameter of vessel lumen and tone of the smooth muscle are determined by the degree of sympathetic activity generally constricts vessels vasoconstriction this increases pressure inside the vessel

4.1.4. Relationship between sympathetic stimulation and blood vessel diameter baseline ( Resting) Sympathetic stimulation smooth muscle thickness of vessel wall diameter of lumen peripheral resistance in arterioles Vasodilation Sympathetic stimulation smooth muscle thickness of vessel wall diameter of lumen peripheral resistance in arterioles Vasoconstriction Sympathetic stimulation smooth muscle thickness of vessel wall diameter of lumen peripheral resistance in arterioles

4.2. smooth muscle in the tunica media of both veins and arteries are supplied with nerves from the autonomic nervous system

4.2.1. they arise from the vasometer centre in the medulla oblongata

4.2.2. they change the diameter of the blood vessel controlling volume of blood they can contain

4.3. What vessels does it effect?

4.3.1. Mainly arterioles as their walls contain more smooth muscle responds to sympathetic stimulation

4.3.2. Large arteries such as the aorta contain more elastic tissue meaning they can expand and recoil depending on the volume of blood passing through

4.3.3. Veins also respond to nerve stimulation but only have little smooth muscle in their tunica media

4.4. Blood flow

4.4.1. resistance to flow fluids along a tube is determined by three factors the diameter of the tube the length of the tube the viscosity of the fluid

4.4.2. the diameter of the resistance vessel is known as the peripheral resistnace major factor in blood pressure regulation Constant adjustment of blood vessel diameter helps regulate peripheral resistance and systemic blood pressure

5. Heart

5.1. Postion

5.1.1. lies in the thoracic cavity

5.1.2. in the mediastinum (space between the lungs)

5.1.3. lies slightly more on the left than the right

5.2. organs associated with the heart

5.2.1. Inferiorly apex rests on the central tendon of the diaphram

5.2.2. superiorly the great blood vessels aorta superior vena cave pulmonary artery pulmonary veins

5.2.3. posteriorly oesophagus trachea left and right bronchus descending aorta inferior vena cava thoracic vertibrae

5.2.4. laterally the lungs left lung overlaps the left side of the heart

5.2.5. anteriorly the sternum ribs intercostal muscle

5.3. roughly cone shaped, hollow muscular organ

5.4. about 10cm long

5.4.1. about the size of a fist

5.5. Structure

5.5.1. the heart wall composed of three layers of tissue Pericardium myocardium endocardium

5.6. Blood supply to the heart

5.6.1. Arterial Supply heart is supplied with arterial blood from fight and left coronary arteries branches from the aorta they recieve 5% of the blood pumped from the heart traverse the heart eventually forming a vast network of capillaries

5.6.2. Venous drainage most venous blood is collected into a number of cardiac veins these join together forming coronary sinus which opens into the right atrium the remainder passes directly into the heart chambers through venus channels

6. The cardiac cycle

6.1. at rest healthy heart beat for an adult is roughly 60-80 beats per min

6.2. during each hear beat the heat contracts (Systole) and then relaxes (Diastole)

6.3. stages of the cardiac cycle

6.3.1. each cycle lasts about 0.8 of a second

6.3.2. consists of 3 components Atrial Systole contraction of the artia last rougly 0.1 seconds Ventricular Systole contraction of the ventricles lasts roughly 0.3 seconds Complete cardiac diastole relaxation of the atria and ventricles lasts roughly 0.4 seconds

6.3.3. Direction of blood flow Atrial systole Atria contract AV valves open Ventricles relaxed Aortic/ pulmonary valves closed Ventricular systole Atria relaxed AV valves closed Ventricles contract Aortic / pulmonary valves open Complete cardiac diastole Atria and ventricles relaxed AV valves open Aortic / pulmonary valves closed

6.4. Heart sounds

6.4.1. 'Lub' Fairly loud Due to closure of the atrioventricular valves corresponds with start of ventricular systole

6.4.2. 'Dup' softer sound due to closure of aortic and pulmonary valves corresponds with ventricular diastole

7. Electrical changes in the heart

7.1. body tissues and fluid can conduct electricity well this allows electrical activity in the heart to be recorded on the skin surface using electrodes

7.1.1. this recording is called and Electrocardiagram (ECG)

7.2. ECG

7.2.1. recording of electrical activity in the heart

7.2.2. shows the spread of electrical signals produced by the pacemaker as it travels through the atria, the AV node and the ventricles

7.2.3. normal ECG tracing Shows five waves P wave QRS complex T wave originates from the SA node called Sinus rhythm the rate of sinus rhythm is usually 60-100 b.p.m

7.2.4. ECG abnormalities Faster heart rate is called tachycardia slower heart rate is called is called bradycardia

8. Cardiac Output

8.1. amount of blood ejected from each ventricle every minute

8.1.1. expressed in Litres per min (L/min) Calculated by multiplying Stroke volume by the heart rate (b.p.m) Cardiac Output = Stroke volume x Heart rate This can increase during exercise this is called cardiac reserve

8.2. Stroke volume

8.2.1. amount of blood expelled by each contraction of each ventricle

8.2.2. is determined by the volume of blood in the ventricles immediately before they contract ie the ventricular end-diastolic volume (VEDV) Sometimes called the preload

8.2.3. in healthy adult stroke volume is approx. 70 mL

8.2.4. Summary of affacting factors VEDV Venous return Position of the body skeletal muscle pump respiratory pump strength of myocardial contraction blood volume

9. Blood Pressure (bp)

9.1. Blood pressure is the force / pressure that blood exerts on the walls of blood vessels

9.2. systemic arterial bp maintains the essential flow of blood into and out of organs of the body

9.2.1. result of discharge of blood from left ventricle into the already full aorta

9.3. can vary according to

9.3.1. time of day bp falls at rest and during sleep

9.3.2. posture

9.3.3. gender usually higher in women

9.3.4. age increases with age

9.4. if bp gets to high it can

9.4.1. damage blood vessels

9.4.2. cause clots

9.4.3. bleed from sites of blood vessel rupture

9.5. if bp gets too low

9.5.1. blood flow through tissue bed can be inadequate dangerous for essential organs heart kidneys brain

9.6. Systolic

9.6.1. when the left ventricle contracts and pushes blood into the aorta

9.6.2. in adults this can be about 120 mmHg

9.7. diastolic

9.7.1. in complete cadiac diastole the pressure in the arteries is much lower

9.7.2. in adults this can be about 80 mmHg

9.8. Arterial blood pressure

9.8.1. measured using a sphygmomanometer

9.8.2. written as systolic pressure written above the diastolic pressure

9.9. Control of blood pressure

9.9.1. Short term regulation on a moment to moment basis Cardiovascular centre Baroreceptors Chemoreceptors higher centres in the brain cardiovascular centre is a collection of interconnected neurones in the medulla and pons of the brain stem

9.9.2. long term regulation slower longer lasting changes in blood pressure affected by renin-angiotensin-aldosterone system also action antidiuretic hormone

10. Pulse

10.1. normally represents the heart rate

10.2. measured in bpm

10.3. averaging 60-80 bpm at rest

10.4. info obtained by pulse

10.4.1. rate at which the heart is beating

10.4.2. regularity of the heart beats intervals between beats should be equal

10.4.3. volume / strenght of the beat should be possible to compress the artery with moderate pressure

10.4.4. the tension artery should feel soft and pliant under fingers

10.5. factors affecting pulse

10.5.1. when arteries supplying peripheral tissues are blocked or narrowed

10.5.2. cardiac contraction disorders atrial fibrillation

10.6. main pulse points

10.6.1. Temporal artery by the eye

10.6.2. Facial artery by the jaw

10.6.3. Common carotid artery on the neck

10.6.4. Brachial artery about halfway up on the inside arm

10.6.5. Radial artery on inside of the wrist

10.6.6. Femoral artery around the hip

10.6.7. popliteal artery behind the knee

10.6.8. posterior artery by the ankle

10.6.9. dorsalis pedis artery by the toes