Transport MechanismsTransport Mechanisms

Chapter 20Chapter 20

Cardiac CycleCardiac Cycle Pattern of contraction Pattern of contraction

(systole) & relaxation (systole) & relaxation (diastole) in 1 heartbeat(diastole) in 1 heartbeat

Average = 0.8 secs (75/min)Average = 0.8 secs (75/min) Atrial SystoleAtrial Systole – – blood sent into ventricles blood sent into ventricles

through AV valvesthrough AV valves Ventricular Systole Ventricular Systole – – ventricles contractventricles contract - AV valves close- AV valves close - high pressure opens SL - high pressure opens SL

valvesvalves - blood into arteries- blood into arteries DiastoleDiastole – – Blood from veins enters & Blood from veins enters &

fills atriafills atria - pressure differences open - pressure differences open

AV valveAV valve

Valves & Heart SoundsValves & Heart Sounds AV (mitral) valve closure AV (mitral) valve closure = heart sound (‘lubb’)= heart sound (‘lubb’) SL (aortic) valve closure SL (aortic) valve closure = second heart sound (‘dubb’)= second heart sound (‘dubb’) Irregular sounds = heart murmurIrregular sounds = heart murmur Due to valve problemsDue to valve problems Measured by phonocardiogramMeasured by phonocardiogram Heard using a stethoscopeHeard using a stethoscope

Heart Conducting SystemHeart Conducting System Pacemaker (Sino-atrial node – SAN): (1)Pacemaker (Sino-atrial node – SAN): (1) Found in the right atrium wallFound in the right atrium wall Exhibits Exhibits spontaneous excitationspontaneous excitation Starts electric impulses Starts electric impulses - heart muscle cells contract- heart muscle cells contract Wave of excitation makes atria contract Wave of excitation makes atria contract

– (2)– (2) Impulse picked up by atrio-ventricular Impulse picked up by atrio-ventricular

node (AVN) – (3)node (AVN) – (3) Impulse passed to conducting fibres – Impulse passed to conducting fibres –

(4) (4) Ventricles stimulated Ventricles stimulated – – ventricular systole – (5)ventricular systole – (5)

Measuring Electrical ActivityMeasuring Electrical Activity Electrocardiogram (ECG) shows electrical Electrocardiogram (ECG) shows electrical

activity of the heartactivity of the heart Abnormal ECG’s - caused by rapid Abnormal ECG’s - caused by rapid

electrical excitationelectrical excitation Atrial Flutter: Atrial Flutter: Co-ordinated, but very rapid contractionsCo-ordinated, but very rapid contractions Fibrillation:Fibrillation: Heart muscle contraction irregular & Heart muscle contraction irregular &

uncoordinateduncoordinated Ventricular Tachycardia:Ventricular Tachycardia: Abnormal ventricular cells act like Abnormal ventricular cells act like

pacemakerspacemakers Ventricle contracts independently of the Ventricle contracts independently of the

atriumatrium All 3 can be relieved by artificial All 3 can be relieved by artificial

pacemakerspacemakers

Blood PressureBlood Pressure Ventricular SystoleVentricular Systole – – aorta pressure rises to a max aorta pressure rises to a max

(avg.120mmHg)(avg.120mmHg) Ventricular DiastoleVentricular Diastole – pressure is – pressure is

at a min (avg. 80 mm Hg)at a min (avg. 80 mm Hg) Measured using a Measured using a

sphygmomanometersphygmomanometer Aorta elastic walls maintain blood Aorta elastic walls maintain blood

pressurepressure As blood circulates round the body As blood circulates round the body

the pressure gradually decreasesthe pressure gradually decreases Blood flowing through blood vessels Blood flowing through blood vessels

= = peripheral resistanceperipheral resistance

High Blood PressureHigh Blood Pressure Increased heart contraction Increased heart contraction

rate/force = higher blood rate/force = higher blood pressurepressure

Common causes: stress or Common causes: stress or high salt intakehigh salt intake

Dangers:Dangers: Ventricles work much harderVentricles work much harder Arterial walls more prone to Arterial walls more prone to

atherosclerosisatherosclerosis Damage to blood vessels - Damage to blood vessels -

strokestroke

Lymphatic SystemLymphatic System

Lymphatic vessels absorb Lymphatic vessels absorb excess tissue fluid (lymph)excess tissue fluid (lymph)

Lymph moved by vessel Lymph moved by vessel compression (body compression (body movements)movements)

Backflow prevented by valvesBackflow prevented by valves Lymph re-enters bloodstream Lymph re-enters bloodstream

via lymphatic ducts in the via lymphatic ducts in the armsarms

Lymph also contains lipids Lymph also contains lipids absorbed by lacteals in the absorbed by lacteals in the intestineintestine

Lymph NodesLymph Nodes Occur in glands around the Occur in glands around the

body e.g armpit, neck, groinbody e.g armpit, neck, groin Consist of lymph nodules, Consist of lymph nodules,

central medulla, & germinal central medulla, & germinal centrecentre

Fibres in between the nodules Fibres in between the nodules lined with macrophage cellslined with macrophage cells

As lymph passes, As lymph passes, macrophage remove macrophage remove unwanted material by unwanted material by phagocytosis phagocytosis

Lymph drains into medulla & Lymph drains into medulla & exits by lymphatic vesselexits by lymphatic vessel

Illness = too many bacteria = Illness = too many bacteria = nodes swell upnodes swell up

OedemaOedema Accumulation of tissue fluid in Accumulation of tissue fluid in

between cells & capillariesbetween cells & capillaries Causes swellingCauses swelling Caused byCaused by:: High blood pressureHigh blood pressure Malnutrition Malnutrition – – low plasma protein in bloodlow plasma protein in blood - blood and tissue fluid equal - blood and tissue fluid equal

conc.conc. - fluid doesn’t return osmotically- fluid doesn’t return osmotically - causes kwashiorkor - causes kwashiorkor ParasitesParasites – – invade lymphatic system & block invade lymphatic system & block

vessels (e.g legs)vessels (e.g legs) - causes elephantiasis- causes elephantiasis