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

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

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

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

4. conducting system of the heart

4.1. Direction of impulse

4.1.1. Superior Vena Cava

4.1.2. Sinoatrial (SA) Node

4.1.3. Atrioventricular (AV) Node

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

4.1.5. Left Atrioventricular (LAV) bundle

4.1.6. network of Purkinje Fibres

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

4.2.1. Heart rate

4.2.1.1. supplied with both sympathetic and parasympathetic nerve fibres

4.2.1.1.1. sympathetic increases heart rate

4.2.1.1.2. parasympathetic decreases heart rate

4.2.1.1.3. other factors affecting heart rate are

4.2.1.2. Heart responds to circulation hormones eg Adrenaline and thyroxine

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

4.3.1. causes coordinated and synchronised contraction of the heart muscle

4.4. Sino atrial (SA) node

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

4.4.2. these cells generate these regular impulses because they are electrically unstable

4.4.2.1. this instability leads them to discharge (depolarise) regularly

4.4.2.1.1. around 60 to 80 times a minute

4.4.2.1.2. this dispoloarisation is followed by recovery (repolarisation)

4.4.2.1.3. 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

4.5. Atrioventricular (AV) node

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

4.5.2. normally merely transmits electrical signals from the atria to the ventricles

4.5.2.1. there is a 0.1 second delay here to pass through the ventricles

4.5.2.1.1. allows atria to finish contracting before ventricles start

4.5.3. has a secondary pacemaker function

4.5.3.1. takes over this role if there is a problem with the SA node or with transmission of impulses from the atria

4.5.3.1.1. discharges around 40-60 times a minute

4.5.4. atrioventricular bundle bundle (AV bundle / bundle of HIS)

4.5.4.1. this is a mass of specialised fibres that originate from the AV node

4.5.4.2. it divides into the right and left bundle branches

4.5.4.3. withing the ventricular myocardium the branches break up into fine fibres called the purkinje fibres

4.5.4.4. these fibres transmit electrical impulses from the AV node to the apex of the myocardium where the wave of ventricular begins

4.5.4.4.1. pumping blood into the pulmonary artery and the aorta

5. Direction of blood flow

5.1. Inferior vena cava

5.1.1. largest veins of the body

5.2. Superior vena cava

5.2.1. largest veins of the body

5.3. Right Atrium

5.3.1. and left atrium both contract at the same time

5.3.2. walls are thinner

5.3.2.1. assisted by gravity to pump blood to ventricles

5.4. Right Ventricle

5.4.1. and left ventricle simultaneously contract after the artias

5.4.2. walls are thicker

5.4.2.1. work against gravity to pump blood into pulmonary artery and to the lungs

5.5. Pulmonary Valve

5.5.1. Tricuspid Valve / Right atrioventricular valve

5.5.2. formed by 3 semilunar cusps

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

5.6. Pulmonary Arteries

5.6.1. left

5.6.1.1. carry venous blood to the lungs

5.6.1.1.1. CO2 excreted

5.6.1.1.2. O2 absorbed

5.6.2. right

5.6.2.1. carry venous blood the the lungs

5.6.2.1.1. CO2 excreted

5.6.2.1.2. O2 absorbed

5.7. Lungs

5.8. Pulmonary Veins

5.8.1. two pulmonary veins from each lung

5.8.2. carr oxygenated blood back to theheart

5.9. Left Atrium

5.9.1. and right atrium both contract at the same time

5.9.2. walls are thinner

5.9.2.1. assisted by gravity to pump blood to ventricles

5.10. Mitral Valve / Left atrioventricular valve

5.11. Left Ventricle

5.11.1. and right ventricle simultaneously contract after the artias

5.11.2. walls are thicker

5.11.2.1. work against gravity to pump blood into aorta and round the body

5.12. Aortic valve

5.12.1. formed by 3 semilunar cusps

5.13. Aorta

5.13.1. first artery of general circulation

6. Arteries, Veins and Capillaries

6.1. Arteries

6.1.1. Have 3 layers

6.1.1.1. Tunica intima / Inner layer; Endothelium

6.1.1.2. Tunica media / Middle layer; Smooth muscle and Elastic tissue

6.1.1.2.1. More Elastic tissue than smooth muscle

6.1.1.3. Tunica adventitia / Outer layer; Fibrous tissue

6.1.2. Have thick walls

6.1.2.1. needed to withstand the the high pressure blood flow

6.1.2.1.1. means when cut blood spurts out

6.1.3. Arteries = Away from the heart

6.1.4. Types of artery

6.1.4.1. Arterioles

6.1.4.1.1. Small arteries

6.1.4.1.2. 3 Layers

6.1.4.1.3. also know as resistance vessles

6.1.4.2. Anastomoses

6.1.4.2.1. Form a link between main arteries supplying an area eg palm of the hand, soles of the feet or brain

6.1.4.2.2. can provide collateral circulation

6.1.4.2.3. provide adequate blood supply when artery is occluded

6.1.4.3. End arteries

6.1.4.3.1. Sole source of blood supply to tissues eg central artery to the retina of the eye

6.1.4.4. when occluded tissue it supply dies as no alternative blood supply

6.1.5. Main arteries

6.1.5.1. Renal

6.1.5.1.1. kidney

6.1.5.2. Hepatic

6.1.5.2.1. liver and gall bladder

6.1.5.3. Gastric

6.1.5.3.1. Stomach

6.1.5.4. Splenic

6.1.5.4.1. spleen and pancreas

6.1.5.5. Carotid

6.1.5.5.1. neck and brain

6.1.5.6. Coronary

6.1.5.6.1. heart

6.1.5.7. Peripheral

6.1.5.7.1. limbs

6.2. Veins

6.2.1. 3 layers

6.2.1.1. Tunica intima / Inner layer; Endothelium

6.2.1.2. Tunica media / Middle layer; Smooth muscle and Elastic tissue

6.2.1.2.1. not as much as in arteries as they don't need to stretch

6.2.1.3. Tunica adventitia / Outer layer; Fibrous tissue

6.2.2. Have thin walls

6.2.2.1. withstand the low pressure blood

6.2.2.1.1. when cut slow, steady blood flow escapes

6.2.3. Veins = Carry blood towards the heart

6.2.4. also know as capacitance vessels

6.2.4.1. distensible

6.2.4.2. have capacity to hold a large proportion of the bodies blood

6.2.4.2.1. 2/3 of the body's blood is in the venous system

6.2.4.2.2. allows vascular system to absorb sudden changes in blood volume

6.2.5. Have valves

6.2.5.1. prevent backflow

6.2.5.1.1. ensuring blood flows to the heart

6.2.5.1.2. assisted by skeletal muscles surrounding the veins

6.2.5.2. formed by fold of endothelium and strengthened by connective tissue

6.2.5.3. semilunar in shape

6.2.5.3.1. concave toward the heart

6.2.5.4. abundant in veins of the limbs

6.2.5.4.1. especially lower limbs where blood has to travel a considerable distance against gravity

6.2.5.5. absent in very small and very large veins in the thorax and abdomen

6.2.6. types of vein

6.2.6.1. venules

6.2.6.1.1. small veins

6.3. Capillaries

6.3.1. Wall consists of one single layer of endothelial cells

6.3.1.1. allows water and other small molecules pass through it

6.3.1.2. blood cells and plasma proteins are usually too big to pass through the capillary wall

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

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

6.3.4. Entry capillary beds are guarded by precapillary sphincters (rings of smooth muscle)

6.3.4.1. they direct blood flow

6.3.4.2. Hypoxia (low oxygen levels in the tissue) and high levels of tissue waste dilate the sphincters

6.3.4.2.1. this increases blood flow through affected beds

6.3.5. types of capilllary

6.3.5.1. Sinusoids

6.3.5.1.1. significantly wider and leakier capillaries

6.3.5.1.2. found in the liver and bone marrow

6.3.5.1.3. walls are incomplete and have larger lumens than normal

6.3.5.1.4. can come directly into contact with cells outside sinusoid walls

6.3.6. capillary refill time

6.3.6.1. when area of skin is pressed it turn white

6.3.6.1.1. because blood has been squeezed out the capillary

6.3.6.2. should take less than 2 seconds for capaillary to refill (skin to turn pink again)

6.3.6.2.1. if takes longer can suggest poor perfusions or dehydration

7. Control of blood vessel diameter

7.1. Baseline, Vasoldilation and vasoconstriction

7.1.1. vasodilation

7.1.1.1. caused by decrease nerve stimulation

7.1.1.1.1. relaxes the smooth muscle thinning the vessel wall and enlarging the lumen

7.1.1.2. increase blood flow at low pressure

7.1.2. Baseline (resting)

7.1.3. sympathetic activity / Vasoconstriction

7.1.3.1. diameter of vessel lumen and tone of the smooth muscle are determined by the degree of sympathetic activity

7.1.3.2. generally constricts vessels

7.1.3.2.1. vasoconstriction

7.1.3.2.2. this increases pressure inside the vessel

7.1.4. Relationship between sympathetic stimulation and blood vessel diameter

7.1.4.1. baseline ( Resting)

7.1.4.1.1. Sympathetic stimulation

7.1.4.1.2. smooth muscle

7.1.4.1.3. thickness of vessel wall

7.1.4.1.4. diameter of lumen

7.1.4.1.5. peripheral resistance in arterioles

7.1.4.2. Vasodilation

7.1.4.2.1. Sympathetic stimulation

7.1.4.2.2. smooth muscle

7.1.4.2.3. thickness of vessel wall

7.1.4.2.4. diameter of lumen

7.1.4.2.5. peripheral resistance in arterioles

7.1.4.3. Vasoconstriction

7.1.4.3.1. Sympathetic stimulation

7.1.4.3.2. smooth muscle

7.1.4.3.3. thickness of vessel wall

7.1.4.3.4. diameter of lumen

7.1.4.3.5. peripheral resistance in arterioles

7.2. What vessels does it effect?

7.2.1. Mainly arterioles as their walls contain more smooth muscle

7.2.1.1. responds to sympathetic stimulation

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

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

7.3. Blood flow

7.3.1. resistance to flow fluids along a tube is determined by three factors

7.3.1.1. the diameter of the tube

7.3.1.2. the length of the tube

7.3.1.3. the viscosity of the fluid

7.3.2. the diameter of the resistance vessel is known as the peripheral resistnace

7.3.2.1. major factor in blood pressure regulation

7.3.2.2. Constant adjustment of blood vessel diameter helps regulate peripheral resistance and systemic blood pressure

8. Heart

8.1. Postion

8.1.1. lies in the thoracic cavity

8.1.2. in the mediastinum (space between the lungs)

8.1.3. lies slightly more on the left than the right

8.2. organs associated with the heart

8.2.1. Inferiorly

8.2.1.1. apex rests on the central tendon of the diaphram

8.2.2. superiorly

8.2.2.1. the great blood vessels

8.2.2.1.1. aorta

8.2.2.1.2. superior vena cave

8.2.2.1.3. pulmonary artery

8.2.2.1.4. pulmonary veins

8.2.3. posteriorly

8.2.3.1. oesophagus

8.2.3.2. trachea

8.2.3.3. left and right bronchus

8.2.3.4. descending aorta

8.2.3.5. inferior vena cava

8.2.3.6. thoracic vertibrae

8.2.4. laterally

8.2.4.1. the lungs

8.2.4.1.1. left lung overlaps the left side of the heart

8.2.5. anteriorly

8.2.5.1. the sternum

8.2.5.2. ribs

8.2.5.3. intercostal muscle

8.3. roughly cone shaped, hollow muscular organ

8.4. about 10cm long

8.4.1. about the size of a fist

8.5. Structure

8.5.1. the heart wall

8.5.1.1. composed of three layers of tissue

8.5.1.1.1. Pericardium

8.5.1.1.2. myocardium

8.5.1.1.3. endocardium

8.6. Blood supply to the heart

8.6.1. Arterial Supply

8.6.1.1. heart is supplied with arterial blood from fight and left coronary arteries

8.6.1.1.1. branches from the aorta

8.6.1.1.2. they recieve 5% of the blood pumped from the heart

8.6.1.1.3. traverse the heart eventually forming a vast network of capillaries

8.6.2. Venous drainage

8.6.2.1. most venous blood is collected into a number of cardiac veins

8.6.2.1.1. these join together forming coronary sinus which opens into the right atrium

8.6.2.1.2. the remainder passes directly into the heart chambers through venus channels

9. The cardiac cycle

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

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

9.3. stages of the cardiac cycle

9.3.1. each cycle lasts about 0.8 of a second

9.3.2. consists of 3 components

9.3.2.1. Atrial Systole

9.3.2.1.1. contraction of the artia

9.3.2.1.2. last rougly 0.1 seconds

9.3.2.2. Ventricular Systole

9.3.2.2.1. contraction of the ventricles

9.3.2.2.2. lasts roughly 0.3 seconds

9.3.2.3. Complete cardiac diastole

9.3.2.3.1. relaxation of the atria and ventricles

9.3.2.3.2. lasts roughly 0.4 seconds

9.3.3. Direction of blood flow

9.3.3.1. Atrial systole

9.3.3.1.1. Atria contract

9.3.3.1.2. AV valves open

9.3.3.1.3. Ventricles relaxed

9.3.3.1.4. Aortic/ pulmonary valves closed

9.3.3.2. Ventricular systole

9.3.3.2.1. Atria relaxed

9.3.3.2.2. AV valves closed

9.3.3.2.3. Ventricles contract

9.3.3.3. Atria and ventricles relaxed

9.3.3.4. Aortic / pulmonary valves open

9.3.3.5. Complete cardiac diastole

9.3.3.5.1. AV valves open

9.3.3.5.2. Aortic / pulmonary valves closed

9.4. Heart sounds

9.4.1. 'Lub'

9.4.1.1. Fairly loud

9.4.1.2. Due to closure of the atrioventricular valves

9.4.1.3. corresponds with start of ventricular systole

9.4.2. 'Dup'

9.4.2.1. softer sound

9.4.2.2. due to closure of aortic and pulmonary valves

9.4.2.3. corresponds with ventricular diastole

10. Electrical changes in the heart

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

10.1.1. this recording is called and Electrocardiagram (ECG)

10.2. ECG

10.2.1. recording of electrical activity in the heart

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

10.2.3. normal ECG tracing

10.2.3.1. Shows five waves

10.2.3.1.1. P wave

10.2.3.1.2. QRS complex

10.2.3.1.3. T wave

10.2.3.2. originates from the SA node

10.2.3.2.1. called Sinus rhythm

10.2.3.2.2. the rate of sinus rhythm is usually 60-100 b.p.m

10.2.4. ECG abnormalities

10.2.4.1. Faster heart rate is called tachycardia

10.2.4.2. slower heart rate is called is called bradycardia

11. Cardiac Output

11.1. amount of blood ejected from each ventricle every minute

11.1.1. expressed in Litres per min (L/min)

11.1.1.1. Calculated by multiplying Stroke volume by the heart rate (b.p.m)

11.1.1.1.1. Cardiac Output = Stroke volume x Heart rate

11.1.1.1.2. This can increase during exercise this is called cardiac reserve

11.2. Stroke volume

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

11.2.2. is determined by the volume of blood in the ventricles immediately before they contract

11.2.2.1. ie the ventricular end-diastolic volume (VEDV)

11.2.2.1.1. Sometimes called the preload

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

11.2.4. Summary of affacting factors

11.2.4.1. VEDV

11.2.4.2. Venous return

11.2.4.2.1. Position of the body

11.2.4.2.2. skeletal muscle pump

11.2.4.2.3. respiratory pump

11.2.4.3. strength of myocardial contraction

11.2.4.4. blood volume

12. Blood Pressure (bp)

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

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

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

12.3. can vary according to

12.3.1. time of day

12.3.1.1. bp falls at rest and during sleep

12.3.2. posture

12.3.3. gender

12.3.3.1. usually higher in women

12.3.4. age

12.3.4.1. increases with age

12.4. if bp gets to high it can

12.4.1. damage blood vessels

12.4.2. cause clots

12.4.3. bleed from sites of blood vessel rupture

12.5. if bp gets too low

12.5.1. blood flow through tissue bed can be inadequate

12.5.1.1. dangerous for essential organs

12.5.1.1.1. heart

12.5.1.1.2. kidneys

12.5.1.1.3. brain

12.6. Systolic

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

12.6.2. in adults this can be about 120 mmHg

12.7. diastolic

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

12.7.2. in adults this can be about 80 mmHg

12.8. Arterial blood pressure

12.8.1. measured using a sphygmomanometer

12.8.2. written as systolic pressure written above the diastolic pressure

12.9. Control of blood pressure

12.9.1. Short term regulation

12.9.1.1. on a moment to moment basis

12.9.2. long term regulation

12.9.2.1. slower longer lasting changes in blood pressure

12.9.2.1.1. Cardiovascular centre

12.9.2.1.2. affected by renin-angiotensin-aldosterone system

12.9.2.1.3. also action antidiuretic hormone

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

13.3.2.1. intervals between beats should be equal

13.3.3. volume / strenght of the beat

13.3.3.1. should be possible to compress the artery with moderate pressure

13.3.4. the tension

13.3.4.1. 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

13.5.2.1. atrial fibrillation

13.6. main pulse points

13.6.1. Temporal artery

13.6.1.1. by the eye

13.6.2. Facial artery

13.6.2.1. by the jaw

13.6.3. Common carotid artery

13.6.3.1. on the neck

13.6.4. Brachial artery

13.6.4.1. about halfway up on the inside arm

13.6.5. Radial artery

13.6.5.1. on inside of the wrist

13.6.6. Femoral artery

13.6.6.1. around the hip

13.6.7. popliteal artery

13.6.7.1. behind the knee

13.6.8. posterior artery

13.6.8.1. by the ankle

13.6.9. dorsalis pedis artery

13.6.9.1. by the toes