Module Transport in Animals Heart and Circulation By Ms Cullen

What are the features of a good transport system? a fluid to carry nutrients and gases around the body – the blood. a pump to create pressure and cause the fluid (blood) to flow around the body- the heart. exchange surfaces which allow nutrients and gases to enter and leave the blood where needed. tubes or vessels to carry the blood. 2 circuits, one to pick up oxygen and nutrients, the other to deliver them to tissues.

Open or Closed Circulatory Systems? Vertebrates have closed circulatory systems – all the blood is enclosed in the blood vessels. Insects have an open circulatory system. In insects blood is pumped by a heart and flows out of the heart in arteries into a body cavity which is called the haemocoel (‘blood space’). In insects blood does not transport oxygen, instead they have tubes, trachea, which carry air directly from the atmosphere deep into the tissues.

Insect

Fish have a two- chambered heart in which a single-loop circulatory pattern takes blood from the heart to the gills and then to the body. Humans, birds, and mammals have a four- chambered heart that completely separates oxygen-rich and oxygen-depleted blood. Single and Double Circulatory Systems

Amphibians have a three-chambered heart with two atria and one ventricle. A loop from the heart goes to the pulmonary capillary beds, where gas exchange occurs. Blood then is returned to the heart. Blood exiting the ventricle is diverted, some to the pulmonary circuit, some to systemic circuit. The disadvantage of the three-chambered heart is the mixing of oxygenated and deoxygenated blood. Amphibians

Reptiles Some reptiles have partial separation of the ventricle. Other reptiles, plus, all birds and mammals, have a four-chambered heart, with complete separation of both systemic and pulmonary circuits.

Single and Double Circulatory Systems Humans and mammals have a double circulatory system. The pulmonary circulation is the part of the circulatory system connected to the lungs. The systemic circulation serves the rest of the body. As there are two circuits, it is known as a double circulatory system, however, it is more like a figure of ‘8’.

Evolution of the circulatory system

Single and Double Circulatory Systems Task: Using P in Kerboodle Explain the differences between the single circulatory system of fish and the double circulatory system of mammals. Explain the advantages of the double circulatory system to humans.

The Mammalian Heart

The internal structure of the heart Week 8

The heart is made of CARDIAC MUSCLE. Cardiac muscle fibres have INTERCALATED DISCS holding the muscle cells together tight and sheet like. This speeds up nervous stimulation of the whole tissue. The heart

The muscle is STRIATED as voluntary muscle is. Mitochondria are numerous. It is MYOGENIC – able to contract and relax of it’s own accord. Cardiac muscle

PAG Heart Dissection Be careful with scalpels! Wear goggles and gloves. Wash hands after dissection. When you have finished complete the Qs at the bottom of the page.

Describe the function of the atrioventricular valves Describe the roles of the tendinous cords Explain why the wall of the left ventricle needs to be much thicker than the right Why might it be harmful if the right ventricle creates too much pressure Questions:

Single circulatory system. Double circulatory system. Diffusion. Respiration. Pulmonary circulation. Systemic circulation. Deoxygenated. Oxygenated. Atrium. Ventricle. Coronary artery. Constrict. Vena cava. Pulmonary vein. Atrioventricular valve. Tendinous cords. Septum. Semilunar valve. Alveoli. circulatory system, erythrocyte, facillitated diffusion, pulmonary circulation, systemic circulation, Keywords you need to know: make a card match activity!

Sequence of Contraction Cardiac Cycle 1. Atrial Systole= Atrial contraction 2. Ventricular Systole = Ventricular contraction 3. Ventricular Diastole= Filling phase Normal cardiac cycles (at rest) take 0.8 seconds The Cardiac Cycle

Ventricular diastole is the filling of the ventricles with blood. Atria and ventricles relax. Blood from the body flows into the vena cava, which empties into the right atrium. At the same time, oxygenated blood from the lungs flows from the pulmonary vein into the left atrium. Ventricular systole opens the SL valves, forcing blood out of the ventricles through the pulmonary artery or aorta. The muscles of both atria contract, forcing blood downward through each AV valve into each ventricle. The Cardiac Cycle

The sound of the heart contracting and the valves opening and closing produces a characteristic "lub-dub" sound. Lub is associated with closure of the AV valves, dub is the closing of the SL valves. Feel the beat...

The Cardiac Cycle uA uA A single heart cell beating!

Cells contract rhythmically – Intrinsic rhythmicity 60 beats per minute Rhythm maintained by a wave of electrical excitation similar to a nerve impulse that spreads through special heart tissue. Hearts’ own rhythm means your body doesn't waste resources on this continuous activity. Control of heart rate

You do also have nerves and hormones to speed up or slow down heart rate which are controlled by cardiovasular centre in your brain. -sympathetic nerves to heart accelerate heart rate - vagus nerve decelerates heart rate

The rhythmic sequence of contractions is coordinated by the sinoatrial (SA) {pacemaker} and atrioventricular (AV) nodes. Human heartbeats originate from SA node near the right atrium. SA gives electrical stimulation that initiates atrial contraction by creating an action potential. Modified muscle cells contract, sending a signal to other muscle cells in the heart to contract. The signal spreads to the atrioventricular node (AV node). Small delay at the AV node Signals carried from the AV node, slightly delayed, (allows blood to fill ventricles) through bundle of His fibers and Purkinjie fibers cause the ventricles to contract simultaneously

Electrical impulses in the heart originate in the sinoatrial node and travel through the intrinsic conducting system to the heart muscle.

The impulses stimulate the myocardial muscle fibres to contract and thus induce systole.

The heart in action

Electrocardiograms The electrical impulses controlling the heart can be detected and measured using an electrocardiogram (ECG). Electrodes are placed on the skin at opposite sides of the heart and electrical potentials are recorded. A graph of voltage against time is produced. An echocardiogram allows Drs to look at the heart working using ultrasound.

One full heartbeat- 0.8s P wave is caused by contraction (depolarisation) of the atrium. QRS complex is caused by contraction (depolarisation) of the ventricles. T wave is the relaxation (repolarisation) of the ventricles. Electrocardiograms

Depolarise = loses electrical charge – contracts Repolarise = regains charge – relaxes Remember!

A normal ECG trace compared with others indicating an unhealthy heart Week 8

Electrocardiograms

Pressures changes in the aorta, left ventricle and left atrium during one heartbeat Using this diagram in your handbook and P.188 in your textbook annotate the graph to explain what is happening to -aortic pressure -ventricular pressure -atrial pressure -ventricular volume Q Why is atrial pressure always lower than ventricular?