Eduqas AS Biology; Component 3 "Adaptations for Transport in Animals"

What type of organisms have an open circulatory system?

Insects

What is the 'heart' in an insect?

A dorsal tube that runs the length of the body

Name and describe the transport medium in open circulatory systems.

The haemolymph, which is yellow

What is the cavity/area that haemolymph enters for gas exchange?

Haemocoel

In what part of the cardiac cycle does repolarisation happen?

Ventricular diastole

What is the direction of circulation in insects?

There is no or little direction of circulation. Fluid is pumped into the haemocoel before being sucked back in when the heart relaxes.

What is the pressure of haemolymph in open circulatory systems and why is this so?

Low pressure since there are no contractions directing the flow somewhere, haemolymph is free to enter haemocoel

Describe a closed circulatory system

The heart is a muscular pump which directs blood out in arteries to capillaries in organs, delivering oxygen, and then blood returns to the heart in veins.

Does blood have contact with organs in closed systems?

No, the organs are bathed in tissue fluid

What is pressure of blood like in a closed system?

High pressure due to being enclosed in vessels with a rapid flow rate

Describe the circulatory system of earthworms.

dorsal and ventral vessels connected by 5 pseduohearts in a single closed circulatory system

What is the respiratory pigment in fish, mammals and earthworms?

Haemoglobin

Define single circulatory system.

Blood passes through the heart once in one complete circulation e.g fish

Define double circulatory system.

Blood passes through the heart twice in one complete circulation e.g. mammals

What is pulmonary circulation?

The blood vessels involved in transporting blood between the heart and the lungs.

What is systemic circulation?

the blood vessels involved in transporting blood in between the heart and respiring tissues

Describe the pressure in single circulatory systems.

It is constant throughout both the pulmonary and systemic systems

Explain the advantages of double circulatory system.

1. maintains High blood pressure in systemic circulation so increased rate of flow to the tissues which increases the rate of oxygen supply to tissues

2.allows for a lower pressure in pulmonary circulation which prevents build up of tissue fluid in lungs

3. Rapid Circulation in systemic than pulmonary ensures rapid delivery of O2 to respiring tissues and rapid removal of co2/waste

What is the role of the endothelium?

Reduces friction and reduces resistance to blood flow due to smooth lining

Describe the structure of a vein.

Really wide lumen to reduce resistance to flow

Every other layer relatively thin:

muscle layer easily compressed to let skeletal muscle squeeze the vein for blood flow

What is role of collagen fibres in tunica externa?

Resistant to overstretching

Describe the structure of the artery.

Thicker smooth muscle layers to withstand high blood pressure

thick elastic fibre layers for elastic recoil to maintain high blood pressure

Whats the role of smooth muscle in the artery?

Contracts and relaxes to direct blood to tissues

Allows arteries to withstand high pressure

Whats the role of elastic fibres in the artery?

RECOIL: maintain high pressure and prevent overstretching

STRETCH: accomodate blood flow

List the functions of the blood vessels in humans.

vein: transport blood to the heart

artery: transport blood from the heart

capillary: allow substances to be exchanged with body cells

Describe the structure of a capillary and how it relates to its function.

One cell thick (endothelium); A short diffusion path for exchange

Narrow lumen; restricts blood flow to slow the blood down

What is backflow in veins?

The movement of blood away from the heart due to gravity

Explain the role of valves in veins and how it works.

The blood above tries to flow back and fills the pockets in the veins, forcing the valves shut.

What veins dont need valves and why?

Veins from the head to the heart since blood has to flow downwards with gravity.

Name the structures found in a heart.

Pulmonary artery, pulmonary vein, left and right atria, left and right ventricles, atrioventricular valves, semi lunar valves, tendious chords .septum, apex, coronary artery

What role does the coronary artery have?

supply heart cells with oxygenated blood and glucose

Describe the role of chordinae tendinae.

.When ventricles contract, blood pressure increases. The AV valves close to prevent backflow into atria, increasing the pressure in the atria compared to the ventricle. The AV valves try to invert and the chordae tendinae tense to prevent that.

List the steps in blood circulation.

1. Oxygenated blood from the lungs enters heart in the pulmonary vein

2. Blood leaves the pulmonary vein and enters LEFT atrium

3. Left atrium contracts so blood is forced into ventricle through the bicuspid atrioventricular valves

4. Valves close, ventricle contracts and forces blood up the aorta through the semilunar valves

5. Oxygenated blood leaves the heart via the aorta and travels to body tissue

6. Deoxygenated blood from the body tissues enters the heart through the vena cava 7.Deoxygenated blood moves from superior and inferior vena cava to right atrium

8. The process repeats but blood leaves through the pulmonary artery to the lungs

What is the cardiac cycle?

The sequence of events in the heartbeat

Explain atrial systole.

Both atria contract so blood flows from atria into ventricles. The AV valves are open but the SL ones are closed

Explain ventricular systole

the ventricles contract, increasing pressure in the blood and closing the AV valves. The SL valves are pushed open and blood flows into the arteries.

Explain ventricular diastole

Atria and ventricles relax SL valves shut. Blood flows from the veins into the atria and ventricles since AV valves are shut.

Explain atrial systole in terms of pressure.

The AV valves are open so the pressure in the atrium is higher than in the ventricle. Blood goes from atrium to the ventricle.

Explain ventricular systole in terms of pressure.

The AV valves are closed due to pressurised blood. Pressure in atrium is closed, and pressure in artery increases to a level just underneath that of the ventricle.

Explain ventricular diastole in terms of pressure.

The AV valves open and the heart fills with blood. The ventricular pressure is lower than the arteriole and atrial pressure.

Why is arteriol pressure never as low as ventricular?

Elastic recoil prevents this.

Explain the fluctuations in pressure in the arteries close to the heart.

The fluctuations correspond to systole and diastole

Explain pressure changes in the arterioles

Friction with vessel walls causes drop in pressure. When they dilate, pressure decreases. When they are constricted, oressure increases.

Explain the pressure drop in capillaries

Small diameter and friction slows blood flow. A lot of capillaries results in a large cross sectional area so this reduces blood pressure.

What does myogenic mean?

muscle genrates its own contraction , it doesnt need to be stimulated by a nerve to make it contract

Explain the control of heartbeat in the heart.

1. Wave of excitation arises at SAN and a wave of depolarisation spreads over atria causing the atrias to contract simultaneously

2. wave is delayed from spreading to ventricles by layer of insulation in connective tissue

3.After a short delay the wave reaches the AVN

4. the wave goes down the Bundle of His to the apex of the heart from the AVN

5. The wave of depolarisation is carried up the purkinje fibres in the ventricular walls

6. Thus causes ventricular systole from the apex upwards

Why is there a delay between the SAN and AVN?

To allow atrial systole to finish before ventricular systole begins

Where is the SAN found?

in the right atrium

In what part of the cardiac cycle does depolarisation happen?

Atrial systole and ventricular systole

What does SAN stand for and what is its function?

Sino-atrial node

Initates systole and acts as a pacemaker

What does ECG stand for?

electrocardiogram

What does the P wave represent?

the depolarisation of the atria during atrial systole

What does the QRS wave represent?

ventricular systole

What does the T wave represent?

Diastole and the repolarisation of the ventricles

What does the distance between P and R represent?

time taken for excitation to spread from atria to the ventricles through the avn

What would a person with irregular heartbeat's ECG looklike?

Smaller/lack of P wave

Irregular or more rapis

fluctuations

What is the difference in the transport of oxygen in an open circulation compared to a closed?

OPEN: directly to respiring tissues by trachael systen

CLOSED: transported from gas exchange system to capillaries in body tissues

Why is it beneficial for oxygenated and deoxygenated blood to be kept seperate in a double circulation?

Maintains a steep concentration gradient for CO2 at the lungs and O2 at the tissue.

Describe how arterioles are adapted to their role.

Can adjust their diameter to vary the blood supply to a capillary bed

State the functions of the main vessels of the heart.

Aorta: transports blood from heart to the body

Vena Cava; carry deoxygenated blood from body to heart

Pulmonary artery; transport deoxygenated blood to lungs for gas exchange

Pulmonary vein; transport oxygenated blood from lungs to heart

Coronary artery: supply heart cells with oxygenated blood and glucose

Coronary vein; remove deoxygenated blood from vardiac muscle

What aids movement in an open circulatory system?

Waves of contraction of the muscle wall

Why is the muscle thicker on the left ventricle?

The left ventricle pumps blood to the body which has a large distance from the heart. The thicker muscle generates a higher pressure so the blood can circulate the whole body.

How can we tell how long a heartbeat is?

The length of time it takes for AV valves to close, open and close again.

Why is blood pressure low in the venules?

The return flow to the heart is non-rhythmic

Why does the blood pressure in veins never fall to 0?

Due to the massaging effect of skeletal muscles

What is ECG shown on?

a cathode ray oscilloscope

Why is the P wave snaller than the QRS wave?

Ventricles conteact with more force due to more muscle ans therefore theres a higher electrical charge

How would you calculate the heart rate from an ECG?

60/time taken between equivalence points

Describe the change in ECG of someone who has just had a heart attack.

The QRS wave is wider and decreases since dead tissue blocks wave of depolarisation