Breathing, circulation and blood

Question 1

What is spontaneous respiration controlled by?

Answer 1

Medulla, however can be overridden for periods of time, eg holding breath

Question 2

What leads to a higher breathing rate?

And what are chemoreceptors?

Answer 2

The central and peripheral chemoreceptors are effected by blood pH, level of acid and amount of co2 (known as partial pressure or PaCO2) , When there is more CO2, this leads to a higher breathing rate.

Chemoreceptors are specialized cell groups responsible for acquiring information about the chemical environment and subsequently conveying the information to neurons.

Question 3

What do we need to ensure that respiration occurs?

Answer 3

we need adequate ventilation, air coming in and adequate perfusion, air coming out. we also need haemoglobin in red blood cells and adaquate uptake of oxygen at the lungs and the body’s cells.

Question 4

What conditions help haemoglobin to release oxygen?

Answer 4

An increace in CO2, temperature and 2,3 DGP

2,3-diphosphoglyceric acid’s function is to bind to haemoglobin and facilitate oxygen transport.

Question 5

How is CO2 transported around the body?

Answer 5

Carbon dioxide is transported in the blood from the tissue to the lungs in three ways:1 (i) dissolved in solution; (ii) buffered with water as carbonic acid; (iii) bound to proteins, particularly haemoglobin.
Approximately 75% of carbon dioxide is transport in the red blood cells (bound to haemoglobin) and 25% in the plasma.

Question 6

How can oxygen levels be measured?

Answer 6

• Haemoglobin saturation assumes you have normal Hb levels, but is very easy to do. Uses adsorption spectroscopy to work out the concentration of Hb by placing a device on a finger
• Arterial blood gas analysis is more complicated and invasive. It measures the level of oxygen and CO2, which is helpful as it is dissolved and so cannot use a colour spectroscopy to measure it. Blood needs to be taken from patient.

Question 7

What are some medical conditions that effect the rate of respiration?

Answer 7

Asthma= the airway membrane thickens

Cystic fibrosis= genetic disease that causes mucus build up and inflammation of airways.

Pneumonia= an infection which causes inflammation and damage in the small airways and alveoli

Pulmonary embolism= clots move into the lungs and stop blood from getting to the lungs. Can be seen in a CT scan, or a tracer

Question 8

What are the main functions of the circulation system?

Answer 8

Transporting oxygen, CO2, hormones, nutrients, waste products, regulating temperature and the clotting system.

Question 9

How much blood does a 60kg human have on average?

Answer 9

In a 60kg human they have 36L of fluid, so 24L of that is intra, 12 is extra and 3L is plasma and 2.4 is red blood cells, so blood makes up around 5.4L.

Question 10

What is Poiseuille’s law?

Answer 10

Liquid in the middle of a tube moves faster than liquid on the edge of a tube- not perfect for predicting blood flow but useful.

Question 11

How does blood speed and pressure vary in arteries, veins and capillaries?

How does vessel diameter and cross sectional area of the vessels change?

Answer 11

• The pressure decreases as the blood moves from the heart
• The blood is fastest in the arteries, then slows down in capillaries then speeds up again slightly in the veins.
• The vessel diameter is large in arteries, drops and then rises again
• The cross sectional area of the vessels is greatest in capillaries.

Question 12

How do walls of smaller arteries regulate blood flow?

Answer 12

They have more smooth muscle and less elastin than the aorta, helps to regulate blood flow.

Question 13

What do veins have that arteries don’t and why?

Answer 13

Due to their low pressure system veins have valves. veins do not need a large increace in pressure to increace their volume, whilst arteries do.

Question 14

What do some/ all capillaries have? (2 answers)

Answer 14

ALL have an endothelial layer (a thin layer of single flat (squamous) cells that line the interior surface), which is relatively permeable

SOME have specialisations such as fenestrations (small openings or pores) or larger holes such as sinusoids in the liver, which allow much freer exchange.

Question 15

How does exit/entrance work in capillaries?

Answer 15

At the start of the bed there is favourable conditions for materials to enter the cells, and towards the end for materials to exit into the blood.
Hydrostatic pressure and osmotic pressure helps to make these favourable conditions. At start there is a larger hydrostatic pressure and smaller osmotic pressure, and vice versa at the end of the bed.

Question 16

What happens when there is a build up of fluid in the capalliries?

Answer 16

Oedema, a build up fluids caused by a greater hydrostatic pressure which can happen in heart failure, or when vein valves are not working great or when someone stands still for a long time

Detected by listening to the lungs, pressing on the tissue or collection of fluid around ankles.

Question 17

What is the yellow dot on the heart diagram?

Answer 17

The pacemaker of the heart- called cardiac conduction system. Gives off electric signals.

Question 18

What are the steps of the cardiac cycle?

Answer 18

Question 19

In what vessels does the blood enter and exit the heart?

Answer 19

Blood returns from the inferior and superior vena cava, then travels through the right atrium and then ventricle. The pulmonary artery takes the blood to the lung, then through the pulmonary vein and through the left atrium and ventricle, and out into the aorta.

Question 20

What are the two formulae for cardiac output?

Answer 20

• Cardiac output = heart rate x stroke volume*
• Cardiac output = arterial blood pressure/ total peripheral resistance*

(TPR= It is the resistance offered by vessel wall for flow of blood.)

Question 21

What does the venous return determine?

Answer 21

Preload and cardiac output

Question 22

What can cause heart failure?

Answer 22

when the pre load rises and if the heart isn’t working properly there might be venous back pressure

Question 23

What is peripheral resistance?

Answer 23

It is the resistance offered by vessel wall for flow of blood.

Is largely due to damage in resistance arterioles and determines afterload.

Question 24

What is P02?

Answer 24

PO2 (partial pressure of oxygen) reflects the amount of oxygen gas dissolved in the blood.

Question 25

Where are red blood cells made?

Answer 25

From 7 months onwards, made in bone marrow.

In the bone marrow, the cells have a nucleus however it is expelled before the red blood cell is circulating.

Question 26

How does the red blood cell structure transport oxygen efficenctly?

Answer 26

It is shaped like a biconcave disk, which means it has increased surface area to increase gas exchange, also means its flexible and deformable to allow movement through small blood vessels.

RBC’s membrane has a lipid bilayer, with the hydrophilic heads facing outwards (40%) of membrane. 50% of the membrane are proteins used to bind the cell together and maintain its shape, some used for transport, glycolysis, and signal transduction

There is NO nucleus or organelles, instead has 270 million haemoglobin molecules

Question 27

How does haemoglobin bind to oxygen?

Answer 27

Can bind to 4 oxygen (O2) molecules, When a Hb binds to its first O2 molecule, its shape changes making is easier to bind to other molecules and become saturated.

Question 28

What is the structure of haemoglobin?

Answer 28

HAEM is made in erythrocytes (red blood cells), oxygen binds to this. There is an iron atom. Bound to a perforin ring.

GLOBIN are protein chains made in red blood cells, bind to haem to form Hb. Normal Hb has 2 alpha globin chains and 2 beta globin chains.

Question 29

What is the Bohr curve (pO2 vs haemoglobin saturation)?

Answer 29

Question 30

What causes the Bohr curve to shift to the left and the right?

Answer 30

The Bohr curve shifts to the right (need higher levels of oxygen to saturate molecules) when pH decreases, CO2 increases, temperature increases and 2,3 DPG increases.
The Bohr curves shifts to the left when there is an increase in CO, when HbF (foetal Hb) increases, when pH increases, or temperature and 2,3 DPG decreases.

Question 31

What is the hormone that influences red blood cell production?

Answer 31

ERYTHROPOIETIN

made in the kidney and liver. Signals bone marrow to make more RBC (only if have raw materials to make them)

Question 32

What is needed to make RBC?

Answer 32

The Haem ring requires iron (recycled from old blood cells and faeces)

Vitamin B12 and folate availability is also required for cell division.

We also need globin chains, the production is inherited, alpha coded on chromosome 16 and beta coded on 11.

Question 33

What causes a high or low heart rate?

Answer 33

Heart rate, 60-100 BPM, feel for rate rhythm and regularity. Feel neck or carotid, elbow or brachial, wrist or radial and groin or femoral. Fit people have lower HR’s

Lower HR’s can be caused by abnormal heart rhythms, myocardial infarction, heart failure, side effects of medication, stroke or electrolyte imbalance.

High HR or tachycardia, above 100 BPM caused by exercise, infection, high blood pressure, thyroid, heart failure, emotional stress, drugs, caffeine and alcohol

Question 34

What causes a lower or higher respiratory rate?

Answer 34

Respiratory rate should be 12-20 breaths per min.

Exercise, stress, infection, drugs can cause abnormal respiratory rate. Sleeping slows rate down as well

Question 35

What is a normal oxygen saturation?

Answer 35

Oxygen saturations 96-100%. Take the warmest finger and shine a light through the nail bed. Can be effected by nail varnish

Abnormality causes are infection, sepsis, or underlying respiratory condition

Question 36

What is a normal temperature?

Answer 36

→ Normal temp is 35.8-37.2 low=hypothermia, high temp=pyrexia. Measured from ear, or infra red forehead check

Question 37

What is a normal blood pressure?

Answer 37

120/80

Systolic blood pressure, the top number, measures the force your heart exerts on the walls of your arteries each time it beats. Diastolic blood pressure, the bottom number, measures the force your heart exerts on the walls of your arteries in between beats.