B4 Flashcards
Explain the structure of the lungs?
They are surrounded by pleural membranes,
The air you breathe in goes through the trachea and splits into two tubes called bronchi (each one is a bronchus)
The bronchi split into progressively smaller tubes called bronchioles.
The bronchioles finally end at small bags called alveoli, where gas exchange happens.
Explain gas exchange?
The lungs contain millions of little air sacs called alveoli, surrounded by a network of blood capillaries.
The blood passing next to the alveoli has just returned from the rest of the body, so it contains lots of carbon dioxide and very little oxygen. Oxygen diffuses out of the alveolus and into the blood. Carbon dioxide diffuses out of the blood and into the alveolus to be breathed out.
Oxygen in red blood cells is diffused into the body cells, and carbon dioxide diffuses out of the body cells into the blood. It is then carried back to the lungs.
Explain the double circulatory system?
In the first one, the right ventricle pumps deoxygenated blood to the lungs. The blood then returns to the heart.
In the second one the left ventricle pumps oxygenated blood around all the other organs of the body. The blood gives up its oxygen at the body cells and the deoxygenated blood returns to the heart to be pumped out to the lungs again.
Features of the heart?
Walls mostly made of muscle tissue.
Has valves to make sure the blood flows in the right direction.
It has four chambers.
Coronary arteries branch off the aorta and surround the heart, making sure that it gets all the oxygenated blood it needs.
How does the heart use its four chambers to pump blood around?
- Blood flows into the two atria from the vena cava and the pulmonary vein.
- The atria contract, pushing the blood into the ventricles.
- The ventricles contract forcing the blood into the pulmonary artery and the aorta, and out of the heart.
- The blood then flows to the organs through arteries, and returns through veins.
- The atria then fill again and the whole cycle starts over.
What is a pacemaker?
A group of cells in the right atrium wall that act as a pacemaker.
These cells produce a small electric impulse which spreads to the surrounding muscle cells, causing them to contract.
An artificial pacemaker is often used to control heartbeat if the natural pacemaker cells don’t work properly. It’s a little device that implanted under the skin and has a wire going to the heart. It produces an electric current to keep the heart beating regularly.
What are the three types of blood vessel?
Arteries: these carry the blood away from the heart.
Capillaries: these are involved in the exchange of materials at the tissues.
Veins: these carry blood to the heart.
Features of arteries?
Strong and elastic walls
Thick walls compared to the lumen
Contain thick layers of muscle to make them strong, and elastic fibres to allow them to stretch and spring back
Features of capillaries?
Arteries branch into capillaries
Really tiny
Carry blood really close to every cell in the body to exchange substances with them
Permeable walls so substance can diffuse in and out
One cell thick walls, increase rate of diffusion
Features of veins?
Capillaries join up to form veins
Less thick walls because of low blood pressure
Bigger lumen to help blood flow
Valves to help keep the blood flowing in the right direction
Features of red blood cells?
They carry oxygen
Biconcave disc - large surface area for absorbing oxygen
No nucleus - more space
Red pigment called haemoglobin
Haemoglobin binds to oxygen to become oxyhaemoglobin. In body tissues, the reverse happens - oxyhaemoglobin splits up into haemoglobin and oxygen, to release oxygen to the cells.
White blood cell features?
Some can change shape to gobble up unwelcome microorganisms, in a process called phagocytosis.
Others produce antibodies to fight microorganisms, as well as antitoxins to neutralise any toxins produced by the mo.
They have a nucleus.
Features of platelets?
Small fragments of cells
No nucleus
Help blood to clot at a wound - to stop your blood pouring out and to stop MO getting in
Lack of platelets can cause excessive bleeding and bruising
What are the features of plasma?
Pale straw-coloured liquid which carries just about everything:
Red and white blood cells and platelets
Nutrients like glucose and amino acids
Carbon dioxide
Urea
Hormones
Proteins
Antibodies and antitoxins
What is coronary heart disease?
Coronary arteries get blocked by layers of fatty materials. Causes the arteries to get narrow, so blood flow is restricted and there’s a lack of oxygen to the heart muscle - this can result in a heart attack.
What are stents? Effective time? Recovery speed? Risks?
Tubes inserted inside arteries, keeping them open.
Effective for a long time and the recovery time from the surgery is relatively quick.
Risk of:
Complications during the operation
Infection from surgery
Blood clot developing near the stent (thrombosis)
What are statins?
Drugs that reduce the amount of ‘bad’ cholesterol in the bloodstream. This slows down the rate of fatty deposits forming.
Advantages:
Reduce risk of strokes, heart attacks…
Increase the amount of good cholesterol in your bloodstream, this can remove bad cholesterol from the blood.
May also help prevent other diseases.
Disadvantages:
Could forget to take them.
Negative side effects, some serious (kidney failure, liver damage and memory loss).
Takes time for their effect to kick in.
What is an artificial heart?
Less likely to be rejected by the immune system
Surgery lead to bleeding and infection
Don’t work as well as healthy natural ones do
What is an artificial valve?
Problems with blood clots
What is artifical blood?
Blood substitute (e.g salt solution)
This may give people enough time to produce new blood cells.
State the 5 tissues found in plants?
Epidermal tissue - this covers the whole plant
Palisade mesophyll tissue - this is the part of the leaf where most photosynthesis happens
Spongy mesophyll tissue - this is also in the leaf, and contains big air spaces to allow gases to diffuse in and out of cells
Xylem and phloem - they transport things like water, mineral ions and food around the plant
Meristem tissue - this is found at the growing tips of shoots and roots and is able to differentiate into lots of different types of plant cell, allowing the plant to grow
Features of leaf structure? (5)
Epidermal tissue covered with a waxy cuticle, which helps to reduce water loss by evaporation.
The upper epidermis is transparent so that light can pass through it to the palisade layer.
Palisade layer, lots of chloroplasts at top of leaf, get most light.
Xylem and phloem take away glucose produced by photosynthesis. They help support the structure.
The tissues of leaves are also adapted for efficient gas exchange (e.g. lower epidermis full of little holes called stomata, which let CO2 diffuse directly into the leaf. Controlled by guard cells).
Features of phloem?
Made of columns of elongated living cells with small pores in the end walls to allow cell sap to flow through.
They transport food substances (mainly dissolved sugars) made in the leaves to the rest of the plant for immediate use or for storage.
They transport in both directions
This process is called translocation.
Features of xylem?
1) Made of dead cells joined end to end with no end walls between them and a hole down the middle.
They’re strengthened with a material called lignin
2) They carry water and mineral ions from the roots to the stem and leaves.
3) The movement of water from the roots, through the xylem and out of the leaves is called the transpiration stream.
What is transpiration?
Caused by the evaporation and diffusion of water from a plant’s surface.
Mostly happens at leaves.
This evaporation creates a slight shortage of water in the leaf, and so more water is drawn up from the rest of the plant through the xylem vessels to replace it.
This in turn means more water is drawn up from the roots, and so there’s a constant transpiration stream of water through the plant.
Four main things that affect transpiration rate?
Light intensity (stomata close when it is dark)
Temperature
Air Flow
Humidity
How do you estimate the rate of diffusion?
By measuring the uptake of water by a plant.
Record the starting position of the air bubble. Start a stopwatch and record the distance moved by the bubble per unit time. Keep the conditions constant throughout the experiment.
Features of guard cells?
They have a kidney shape which opens and closes the stomata
When the plant has lots of water the guard cells fill with it and go plump and turgid. This makes the stomata open so gases can be exchanged for photosynthesis.
When the plant is short of water the guard cells lose water and become flaccid making the stomata close. This helps stop too much water vapour escaping.
Thin outer walls and thickened inner walls make the opening and closing work.
You usually find more stomata on the underside of leaves than on the top. The lower surface is shaded and cooler - so less water is lost through the stomata that if they were on the upper surface.
