Cardiovascular System

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Cardiovascular System by Mind Map: Cardiovascular System

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

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

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

2. The cardiac cycle

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

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

2.3. stages of the cardiac cycle

2.3.1. each cycle lasts about 0.8 of a second

2.3.2. 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

2.3.3. 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 Atria and ventricles relaxed Aortic / pulmonary valves open Complete cardiac diastole AV valves open Aortic / pulmonary valves closed

3. Control of blood vessel diameter

3.1. Baseline, Vasoldilation and vasoconstriction

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

3.1.2. Baseline (resting)

3.1.3. 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

3.1.4. 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

3.2. What vessels does it effect?

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

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

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

3.3. Blood flow

3.3.1. 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

3.3.2. 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

4. Blood Pressure (bp)

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

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

4.3. can vary according to

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

4.3.2. posture

4.3.3. gender usually higher in women

4.3.4. age increases with age

4.4. if bp gets too high it can

4.4.1. damage blood vessels

4.4.2. cause clots

4.4.3. bleed from sites of blood vessel rupture

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

4.5. if bp gets too low

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

4.6. Systolic

4.6.1. Arterial blood pressure written as systolic pressure written above the diastolic pressure measured using a sphygmomanometer

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

4.6.3. in adults this can be about 120 mmHg

4.7. diastolic

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

4.7.2. in adults this can be about 80 mmHg

4.8. Control of blood pressure

4.8.1. Short term regulation on a moment to moment basis

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

5. CVC send autonomic nerves both sympathetic and parasympathetic to the heart and blood vessels

6. Due to closure of the atrioventricular valves

7. Heart sounds

7.1. 'Lub'

7.1.1. Fairly loud corresponds with start of ventricular systole

7.2. conducting system of the heart

7.2.1. Direction of impulse Superior Vena Cava Sinoatrial (SA) Node Atrioventricular (AV) Node Atrioventricular bundle (AV) bundle / bundle of His Left Atrioventricular (LAV) bundle network of Purkinje Fibres

7.2.2. posses the property of autorhythmicity (generates its own electrical impulses and beats independently of nervous or hormonal control) Heart rate supplied with both sympathetic and parasympathetic nerve fibres Heart responds to circulation hormones eg Adrenaline and thyroxine

7.2.3. small groups of specialised neuromuscular cells in the myocardium initiate and conduct impulses causes coordinated and synchronised contraction of the heart muscle

7.2.4. Sino atrial (SA) node is a small mass of specialised cells that lies in the wall of the right atrium these cells generate these regular impulses because they are electrically unstable this instability leads them to discharge (depolarise) regularly

7.2.5. Atrioventricular (AV) node is a small mass of neuromuscular tissue situated in the wall of the atria septum near the atrioventricular valves normally merely transmits electrical signals from the atria to the ventricles there is a 0.1 second delay here to pass through the ventricles 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 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

7.2.6. Direction of blood flow Inferior vena cava largest veins of the body Superior vena cava largest veins of the body Right Atrium and left atrium both contract at the same time walls are thinner Right Ventricle and left ventricle simultaneously contract after the artias walls are thicker Pulmonary Valve Tricuspid Valve / Right atrioventricular valve formed by 3 semilunar cusps prevents backflow of blood to the right ventricle when it relaxes Pulmonary Arteries left right Lungs Pulmonary Veins two pulmonary veins from each lung carr oxygenated blood back to theheart Left Atrium and right atrium both contract at the same time walls are thinner Mitral Valve / Left atrioventricular valve Left Ventricle and right ventricle simultaneously contract after the artias walls are thicker Aortic valve formed by 3 semilunar cusps Aorta first artery of general circulation

7.3. 'Dup'

7.3.1. softer sound

7.3.2. due to closure of aortic and pulmonary valves

7.3.3. corresponds with ventricular diastole

8. it controls BP by slowing down or speeding up heart rate and by constricting and dilating blood vessels

9. cardiovascular centre is a collection of interconnected neurones in the medulla and pons of the brain stem

9.1. the CVC receives integrates and coordinates input from Baroreceptors (pressure receptors), chemoreceptors and higher centres in the brain

10. Arteries, Veins and Capillaries

10.1. Arteries

10.1.1. 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

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

10.1.3. Arteries = Away from the heart

10.1.4. 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

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

10.2. Veins

10.2.1. 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

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

10.2.3. Veins = Carry blood towards the heart

10.2.4. 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

10.2.5. 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

10.2.6. types of vein venules small veins

10.3. Capillaries

10.3.1. 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

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

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

10.3.4. 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

10.3.5. 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

10.3.6. 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

11. Heart

11.1. Postion

11.1.1. lies in the thoracic cavity

11.1.2. in the mediastinum (space between the lungs)

11.1.3. lies slightly more on the left than the right

11.2. organs associated with the heart

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

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

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

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

11.2.5. anteriorly the sternum ribs intercostal muscle

11.3. roughly cone shaped, hollow muscular organ

11.4. about 10cm long

11.4.1. about the size of a fist

11.5. Structure

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

11.6. Blood supply to the heart

11.6.1. 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

11.6.2. 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

12. Electrical changes in the heart

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

12.1.1. this recording is called and Electrocardiagram (ECG)

12.2. ECG

12.2.1. recording of electrical activity in the heart

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

12.2.3. 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

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

13. Pulse

13.1. normally represents the heart rate

13.2. measured in bpm

13.3. info obtained by pulse

13.3.1. rate at which the heart is beating

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

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

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

13.4. averaging 60-80 bpm at rest

13.5. factors affecting pulse

13.5.1. when arteries supplying peripheral tissues are blocked or narrowed

13.5.2. cardiac contraction disorders atrial fibrillation

13.6. main pulse points

13.6.1. Temporal artery by the eye

13.6.2. Facial artery by the jaw

13.6.3. Common carotid artery on the neck

13.6.4. Brachial artery about halfway up on the inside arm

13.6.5. Radial artery on inside of the wrist

13.6.6. Femoral artery around the hip

13.6.7. popliteal artery behind the knee

13.6.8. posterior artery by the ankle

13.6.9. dorsalis pedis artery by the toes

14. Cardiac Output

14.1. amount of blood ejected from each ventricle every minute

14.1.1. 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

14.2. Stroke volume

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

14.2.2. 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

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

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