Circulatory system

Question 1

Describe the Structure of an artery

Answer 1

• The artery is made of smooth inner lining(endothelium), to prevent turbulence in flow of blood.
• Small lumen to maintain pressure
• High ratio of elastin fibers to allow walls to stretch and recoils as blood is pumped in the artery, to maintain pressure.
• High amounts of collegen which prevents rupturing of wall and provides strength

Question 2

Describe the Structure of an Vein

Answer 2

• Semi Lunar valves present to prevent back flow of blood
• Endothelium(Smooth inner lining) to prevent turbulence flow
• Thin walls as blood flows at low pressure, hence only few elastin and collagen is needed
• Large lumen

Question 3

Describe the Structure of Capillary

Answer 3

-Only endothelium is present. One cell thick for short diffusion surface.
Semi permeable walls to allow to exchange of oxygen,CO2 and glusoce.

Question 4

Differentiate between arterioles and venules

Answer 4

Arterioles carry oxygenated blood from arteries to capillaries. The consist of only endothelium and some muscle fibres. Serves to regulate the quantity of blood that enters capillaries.
The venules carries deoxygenated blood from the capillaries to the veins. They are consist of collagen and are thick and non elastic. Allows blood to drain into veins

Question 5

Why is the heart described as closed and double?

Answer 5

The heart is a closed system because at no point is blood outside the blood vessel unless there is a cut.
Double circulation means blood travels through the heart twice through the pulmonary and systematic circulation.

Question 6

Differentiate between pulmonary and systematic circulation

Answer 6

Pulmonary Circulation: Deoxygenated blood travels from the heart to the lungs via the pulmonary artery and returns via the pulmonary vein.
Systematic Circulation: Blood from the heart is pumped into the aorta to be carried to all the organs in the artery, except the lungs. Deoxygentaed blood is then carried to the vena cava through the veins.

Question 7

Differentiate between the right and left side of the heart

Answer 7

The right heart pumps deoxygenated blood through the pulmonary circuit (to the lungs) while the left side pumps oxygenated blood through the systematic circuit (to the rest of the body)

Question 8

Describe the inner structure of the heart

Answer 8

The heart is divided into 4 chambers. The two top thin walls are called the atria. The collect blood from veins and pump the blood into the lower ventricles. The right atrium collects blood form the vena cava (the body) and the left atrium collects blood from the pulmonary vein (from the lungs).
The lower chambers are called the ventricles. The are surrounded by thick muscles. They collect blood from the atria to be pump blood into the arteries. The right ventricle pumps deoxygenated blood to the pulmonary artery. The left ventricle pumps blood to the aorta.
The muscular wall of the left ventricle is greater than that of the right ventricle because the left ventricle has to pump blood to the entire body while the right atrium has to pump to the lungs which are nearby.

Question 9

State the valves in the heart and their function

Answer 9

Valves prevent the back flow of blood. The values called atrioventricular values, separate atrium from ventricles. The values that separate the right atrium and right ventricle is call the tricuspid valve. The valve that separate the left atrium from the left ventricle is called the bicuspid valves.
The semi-lunar valves separate the ventricles from the arteries.

Question 10

Describe the two phases of the cardiac cycle?

Answer 10

Systole and Diastole. Systole refers to the contraction of the atrium or ventricles. Diastole refers to the relaxation of the atrium or ventricles; blood enters. It begins with the contraction of the atria. It causes blood to rush into the ventricles and the AV valves to open. This is atrial systole. When the ventricles are full, ventricles systole begins. Contaction begins in the base of the ventricles and pressure becomes greater than that of the atrium, hence the AV valves close and the SL valves to open

Question 11

Explain the cardiac cycle from the P wave to the QR complex

Answer 11

The SAN nodes fires off to causes the atrium to contract and begin atrial systole. This makes the pressure in the atrium to increase and causes the AV valves to open and blood flows into the ventricles. As atrial systole comes to an end and diastole begins, the pressure gradient reverses and causes the AV valves to close, producing the first heart sound, S1.
Ventricular Systole begins when the van begins to contract. Contraction begins at the base of the van and this is shown by the QR complex.

Question 12

Explain the cardiac cycle from the RS complex to the T wave

Answer 12

As the vans start to contract, pressure builds up in the van and this is shown by the RS complex. When the pressure builds up to a point that is greater than the aorta and pulmonary artery, the semi-lunar valves open and rapid blood ejection begins. This is shown by the T wave. As ventricular systole comes to an end, pressure in the vans fall and this cause the SL valves to close, producing the second heart sound, S2. this starts ventricular diastole.

Question 13

Why is the heart myogenic?

Answer 13

The heart is myogenic as it gives rise to its own contractions without interference of the nervous system. Specialized cells called cardiac cells initiate signals across the heart that makes it contract in a specific way. It ensure the ventricles contract after the atrium.

Question 14

What are the names of the fibers that control the contraction of the heart

Answer 14

SAN ( Sino atrial node)
AVN (atrio ventricular nose)
Purkyne fibers

Question 15

Role of the SAN

Answer 15

The SAN starts the cardiac cycles and is referred to the pacemaker of the heart. Every time it contracts, it sets up a wave of electricity impulse that spreads across the atrial walls, allowing it to contract with the SAN node

Question 16

Roles of the AVN and purkyne fibres

Answer 16

The fibers in between the atria and ventricles cannot conduct the excitement wave released by the SAN. Instead, electric waves travel to the AVN. The AVN creates a delay in the contraction of the vans. The AVN carries the impulse down the septum along the purkyne fibers to the base of the heart. The impulse then travels up the walls of the ventricles, cause the ventricles to contract.

Question 17

Define stroke volume

Answer 17

Stroke volume is the amount of blood ejected by each ventricle by the contraction

Question 18

How does exercise affect cardiac output?

Answer 18

During exercise, there is a drop in oxygen amounts in the blood. The cells of the blood vessels react to this by creating nitric oxide. Nitric oxide relaxes the muscles of the arterioles and allows more blood the into the vein and hence the heart. The heart compensates by pumping more vigorously. The stretching of the heart muscles makes the SAN fire off more rapidly

Question 19

What is cardiac output?

Answer 19

Cardiac output = stroke volume * heart rate

The amount of blood that leaves the heart over a given time.

Question 20

Differentiate between sympathetic and parasympathetic nerves running to the heart?

Answer 20

The sympathetic nerve carries nerve impulses to the wall of heart muscles while parasympathetic nerves (vagus) nerves sends impulses to the SAN and AVN. If an action potential travels through the sympathetic nerves, to increases the heart rate and stroke volume, while if it run along the vagus nerve, it does the opposite.

Question 21

State the role of baroreceptors

Answer 21

Baroreceptors are stretch receptors in the aorta and carotid arteries. If blood pressure rises in the heart, the aorta walls stretches to activate the baroreceptors to send a signal to the brain. the brain then sends an impulse via the vagus nerve to slow the heart rate. Low pressure has the opposite effect. The lack of stretching will make the brain send a signal along the sympathetic nerve to increase heart rate

Question 22

Define blood pressure

Answer 22

blood pressure is the pressure of the circulating blood exerts on the walls of the blood vessels. It is divided in two types: systole and diastole blood pressure. Systole pressure is the highest of the two and is caused by the contraction of the left ventricle while diastole is the pressure of the relaxation of the ventricular muscles. Its is the most important number

Question 23

what is atherosclerosis?

Answer 23

Atherosclerosis is the thickening of the blood vessels caused by high build up of cholesterol in the artery walls forming plagues

Question 24

what is hypertension?

Answer 24

Hypertension is a persistently high diastole pressure (high blood pressure)

Question 25

What is the role of chemo-receptors?

Answer 25

Chemo receptors in the carotid artery detects the concentration of carbon dioxide in the body. If CO2 conc becomes too high or if O2 conc becomes too low, impulses from the brain is sent via the sympathetic nerves to increase heart rate.

Question 26

What are 3 factors that affect blood pressure

Answer 26

Volume of blood pumped by heart- Blood pressure increase if stroke volume increase
Volume of blood in blood vessels- Blood pressure is high if there is alot of blood in the blood vessels
Elasticity of blood vessels- Blood pressure rises if arteries become hardens.

Question 27

Describe the structure of an erythrocyte

Answer 27

• Very small, about 7um in diameter hence hemoglobin is found near the cell plasma membrane to facilitate gaseous exchange.
• Biconcave disc shape. It has a small dent in the middle to increase surface area: volume ratio. Allows for rapid O2 exchange
• No nucleus, mitochondria or endoplasmic reticulum. Provides more room for the hemoglobin

Question 28

Describe the role of hemoglobin

Answer 28

Hemoglobin is a tertiary protein that transport O2 around the body. It carries 4 oxygen molecules in the form of oxyhemoglobin. It binds with oxygen when oxygen is in high conc and releases it in low conc. The binding of one oxygen molecules makes it easier for the next molecule to be added.

Question 29

Describe the hemoglobin dissociation curve

Answer 29

At high partial pressure of oxygen (in the lungs), the hemoglobin is fully saturated. As the partial pressure falls (in the muscles), the saturation is low as hemoglobin unloads its oxygen to the muscles. The graph is a S shape to show the way hemoglobin combines with oxygen. It is quite difficult for the first oxygen to bind with HB but easier for the rest. HB has a low affinity for oxygen in the low oxygen con

Question 30

Describe hoe 5%, and 10% of carbon dioxide is transported to the lungs

Answer 30

5% of the CO2 is directly dissolves in the plasma membrane and transported to the lungs. 10% of the carbon dioxide diffuses directly into the erythrocytes and binds with the hemoglobin to form carbaminohaemoglobin to be transported to the lungs.

Question 31

Describe how 85% of CO2 is transported to the lungs

Answer 31

The enzyme carbonic anhydrase catalyze this reaction
CO2+H2O— H2CO3 (carbonic acid)
The acid dissociates quickly
H2CO3—- H* + HCO3^(hydrohencarbonate ion)
The H* ion binds with hemoglobin to form haemoglobinic acid which makes the the hemoglobin release the oxygen it was holding. The hydrogencarbonate ions diffuses into the plasma membrane where it is transport to the blood.

Question 32

What is mean by Bohr effect/shift?

Answer 32

Occurs during high levels for respiration. It is the observation that in high concentration of CO2 or low pH, hemoglobin has a lower affinity to oxygen. The graph is shifted to the right, meaning it unloads more easily at respiring cells due to the high levels of CO2 and low pH. Increase in acidity makes the HB lose its grip on O2.