Biology Revision: Human Biology

For inhalation:

• Intercostal muscles contract, forces ribcage upwards
• Diaphragm subsequently also contracts, flattening it
• The volume of the thorax increases
• The decrease in pressure to that of the air outside the body forces air into the lungs

For exhalation:

• Intercostal muscles relax, forces ribcage down
• Diaphragm relaxes and returns to a domed shape
• Volume of the thorax decreases
• Pressure increases, forcing air out of the lungs

Alveoli provide a large SA rich with capillaries so gases can diffuse in and out of the blood.

The use of mechanical ventilators can help with breathing difficulties, negative pressure ventilators causes air to be drawn into the lungs, and positive pressure ventilators forces air out of the lungs

Aerobic Respiration: Takes place continuously in both plants and animals in the mitochondria

glucose+oxygen->carbon dioxide + water (+ energy)

c6h12O6+6O2->6CO2+6H2O(+ energy)

The energy released can be used for things such as:

• Muscle contraction
• Formation of larger molecules from smaller ones
• Maintaining a steady body temperature
• In plants to build up nutrients/sugars into amino acids and then into proteins.

During exercise the human body reacts to the increased demand for energy by increasing the heart rate, converting glycogen to glucose, and the breathing rate and depth increases.

These changes increase the supply of glucose and oxygen to, and increase the rate of CO2 removal from the muscles.

If there isn't enough oxygen then energy is produced by anaerobic respiration.

Glucose->Lactic Acid (+ energy)

C6H12O6->2C3HO3 (+ energy)

This incomplete breakdown of glucose builds up an oxygen debt needed to oxidise the lactic acid into CO2 and H2O. This is why after exercise, the breathing rate stays high.

Anaerobic Respiration will produce only a small amount of the energy produced in aerobic respiration, and in plants it will produce ethanol and Carbon Dioxide.

Circulatory system consists of the blood, blood vessels and the heart.

Heart structure:

Right Atrium - recieves deoxygenated blood from the great veins (venae cavae)
Great Veins - return deoxygenated blood to the heart from the body.
Large valve (triculspid) - prevents backflow of blood into the atrium which the ventricle contracts.
Right ventricle - less muscular chamber which pumps deoxygenated blood to the lungs through the pulmonary artery.
Semilunar valve - prevents backflow of blood into the ventricle when the heart relaxes (also in the aorta)
Aorta - Great Artery carrying oxygenated blood to all parts of the body.
Left Atrium - Receives oxygenated blood prom the pulmonary veins.
Left Ventricle - Very muscular chamber which pumps oxygenated blood to the rest of the body.
Pulmonary veins - Carry oxygenated blood back from the lungs to the heart
Large Valve (Bicuspid) - prevents backflow of blood into Atrium when the ventricle contracts/

Blood content:

• Plasma: yellow liquid which transports dissolved food molecules, carbon dioxide and urea as well as blood cells. made up mainly of water.
• Red blood cells:  are made in the bone marrow, have no nucleus for maximum oxygen intake, main function is to carry oxygen as oxyhaemoglobin. Have a large surface area from bioncave shape.
• White blood cells: are made in the bone marrow. Phagocytes and Lymphocytes.
• Platelets: are cell fragents which help clot the blood.

PLATELETS

Made in the bone marrow. have no nucleus. 

• Nearby platelets stick together and to the sides of the tear to create a temporary plug.
• Re-inforces by clotting factors, activated and stick to the platelets.
• Fibrin form a web like glue. Stick all together, a network of fibrin.
• Other blood cells re-inforce, become stronger and help bring sides together and stay in untill tissue is repaired to stop bleeding and stop microbes entering. 

• Arteries: Have a thick muscular wall, small lumen and high blood pressure. Blood pumped from the heart to the body. ( Oxygenated )
• Veins: Have a thinner muscle layer, large lumen for blood to flow and low pressure. Blood pumped from the body to the heart. ( Deoxygenated )
• Capillaries: Have a one cell thick wall for diffusion. Have a very narrow lumen, and a high/low pressure. These carry blood through the organs. To The veins from the arteries. 

Antigens-Proteins on the surface of cells. These can determine blood groups-A,B,AB and O

Process of Digestion:

Mouth-Teeth use large SA to break down the food and tongue forms it into a ball
Oesophagus-The ball will travel down here to reach
Stomach-Through the use of HCl and the churning of food it is broken into liquid form
Small Intestine-Soluble food molecules absorb through here and into the blood (diffusion)
Large Intestine-Water is absorbed out of here and into the blood, leaving just the waste
Liver-Filters out harmful substances from the food and produces bile
Rectum-Storage of waste/faeces
Anus-Disposes of waste/faeces

Digestive Enzymes:Produced by specialist cells in glands/lining of the gut

Carbohydrases-E.g. Amylase, catalyse the breakdown of carbohydrates (e.g. starch) to sugars

Proteases-Catalyse the breakdown of proteins to amino acids

Lipases-Catalyse the breakdown of lipids into fatty acids and glycerol. 

Because the stomach produces hydrochloric acid to help with the breakdown of food, this shows that the protease enzymes in the stomach will work best in acidic conditions at the low pH of the HCl.

The enzymes made in the pancreas and small intestine however, will work best in alkaline conditions.

The liver's production of bile-Bile is stored in the gall bladder and released through the bile duct.When food comes into the small intestine, bile neutralises the acid added to it in the stomach to allow the enzymes to work most efficiently, and also emulsifies the fats (breaks them down from large droplets to small: bigger SA to help lipase break them down quicker)

The CNS uses electrical impulses to enable coordination of the body.

The process:

1.There is a stimulus (change in the environment) detected by sensory neurones.
2.The neurone passes an electrical impulse onto the CNS (brain and spinal cord)
3.The brain will then co-ordinate a response by sending an impulse along the spinal cord to the motor neurone, where it will reach the effector organ and the organ will react to the stimulus.

With some stimulus, there are responses which do not pass through the CNS

.NOTE: The gaps between neurones means the impulse must chemically diffuse over the synapses

The process for these reflex actions is:

Stimulus>Receptor>Sensory Neurone>Relay Neurone>Motor Neurone>Effector>Response

Structure of the brain:

Cerebral Cortex-Handles intelligence,memory,conciousness,language
Cerebellum- Coordination of muscular activity
Medulla- Unconcious activities like breathing/heartbeat

The kidney removes water from the body tissues

In the liver, excess amino acids from the diet are converted into urea through 'deanimation'

This urea then passes into the kidney, which then converts it into urine and it is excreted.

Kidney Function:

1.Capillaries around the kidney tubule filter all soluble substances out of the blood and into the kidney tubule
2.Then,active transport moves some of the ions back into the blood (selective reabsorption)
3i.If there is too much water in the blood, then the tubule will not reabsorb the water back into the blood just before the ureter and it will be dispersed in the urine
3ii.If there is too little water,more of the water from the kidney tubule osmoses back into the blood.

The amount of water in the blood is also maintained by the hormone ADH.

WHEN WATER CONC.=TOO LOW

• More of the ADH hormone is secreted from the pitituary gland in the brain.
• This hormone will cause the kidney tubule to reabsorb more water back into the blood, until the normal water conc. is restored.
  
  

WHEN WATER CONC.=TOO HIGH

• Less of the hormone ADH is secreted
• The kidney tubules will reabsorb less water 

KIDNEY PROBLEMS:

CAN BE TREATED THROUGH KIDNEY TRANSPLANTS OR DIALYSIS

DIALYSIS- THE USE OF A MACHINE TO REPLACE THE KIDNEY

ADVANTAGES:                                       DISADVANTAGES:
NO RISK OF OPERATION FAILURE        TIME-CONSUMING
FREELY AVAILABLE                              LOWER QUAL. OF LIFE E.G. NO HOLIDAYS

KIDNEY TRANSPLANT

ADVANTAGES:                                     DISADVANTAGES:
QUICKER/CHEAPER                              RISK OF OPERATION FAILURE
CAN LIVE A NORMAL LIFE                  NOT AS AVAILABLE AS DIALYSIS

TOO HIGH:

If not dealt with there will be significant osmotic damage to the brain cells and they will suffer HYPERGLYCAEMIA

The pancreas cells detect this, and insulin is secreted into the blood.
Insulin will cause the blood glucose to moved into cells, especially the liver and muscle cells. It also causes the conversion of the glucose into glycogen for later use.

TOO LOW:

If not dealt with there will not be enough glucose for the brain cells to respire, fall into a coma, HYPOGLYCAEMIA.

Pancreas cells detect this, and secrete Glycogen into the blood.
The glycogen will release needed glucose into the blood by breaking down into glucose 

TYPE 1 Diabetes:

• USUALLY GENETIC-WHEN THE PANCREAS IS UNABLE TO PRODUCE ENOUGH INSULIN AND SO BLOOD GLUCOSE IS TOO HIGH
• CAN BE TREATED THROUGH CAREFUL DIET,EXERCISE, AND INJECTING INSULIN

TYPE 2 Diabetes:

• WHEN THE BODY DOES NOT RESPOND TO ITS OWN INSULIN
• OBESITY CAN BE A SIGNIFICANT FACTOR IN THE DEVELOPMENT OF TYPE 2 DIABETES
• CAN BE TREATED THROUGH DIET,EXERCISE,AND DRUGS TO HELP THE CELLS RESPOND TO INSULIN

WHEN IT IS TOO COLD:

• THE SWEAT GLAND PRODUCES NEXT TO NO SWEAT
• HAIRS RAISE IN ORDER TO TRAP AN INSULATING LAYER OF AIR
• BLOOD FLOW THROUGH THE CAPILLARIES IS REDUCED
• MUSCLES 'SHIVER' THROUGH RESPIRATION, RELEASING SOME ENERGY TO WARM THE BODY

WHEN IT IS TOO COLD:

• MORE SWEAT PRODUCED TO ABSORB HEAT ENERGY AND EVAPORATE
• HAIR FLATTENS
• CAPILLARY HAS A HIGHER RATE OF BLOOD FLOW