Pancreas
- Gland which produces pancreatic juice containing protease, carbohydrase and lipase
- These enzymes require alkaline conditions to work (with the help of bile neutralising acids)
Small intestine
- Long tube
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Millions of villi on walls of small intestine to increase surface area and assist with absorption of molecules and nutrients into the cell wall and the surrounding capillaries *diffusion is the passive movement of particles
- Digested food is absorbed into the blood here
- Contains intestinal juice, which has protease, carbohydrase and lipase. These enzymes complete the digestion of food
- The completion of digestion
- Where most absorption is taken place
Large Intestine
- Tube which absorbs water into blood
- Colon absorbs a lot of water
- Forms undigested food into a nearly solid waste called faeces (mainly fibre)
- The faeces are stored inside the rectum
- Faeces is passed out through the anus
Villi ~ The small intestine is very good for absorption and allows time for absorption because it has a thin lining, a good blood supply, a very large surface are and its blood supply is close to gut wall. The surface area is about 9m. The small intestine is very long (six meters) and it has a folded inner lining and it has tiny, finger like projections called villi.(singular of villus)
-The villus wall is only one cell thick
-Amino acids, sugars and some fatty acids are absorbed through the thin villus wall into the blood capillaries
*most of the fatty acids pass into the lacteal and are carried in the lymph vessel
*then the rest of food that is not absorbed into the capillaries carry on towards the liver
Blood
There is about 5 litres of blood in our body.
>> The blood is made of
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A yellow liquid call plasma (Mainly water with chemicals dissolved in it)
* It carries red, white blood cells and platelets around the body
* Carries vitamins and minerals from the small intestine
* Carries hormones, chemical waste and antibodies
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Red blood cells / Erythrocyte (Bi-concave disc shaped, Large surface area, no nucleus, has haemoglobin (protein that contains iron) haemoglobin – 1. oxygen diffuses into red blood cell 2. oxygen reacts with haemoglobin inside red blood cells to get oxyhaemoglobin (what out bodies need) 3.When red blood cell reaches an area of low oxygen concentration, it transports oxygen to that certain area and the oxygen ‘unsticks’ from the oxyhaemoglobin and oxygen diffuses out of red blood cell. Now the oxyhaemoglobin is just haemoglobin 4. The empty red blood cell returns to the lungs to pick up transport more oxygen around the body
* Carries oxygen around the body
* Made in bone marrow
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Platelets (Small fragments of cells)
* Made in bone marrow
* Help in the clotting of blood – 1. The skin is cut and blood start to leak out of the body 2. There is a soluble protein in the blood call fribrinogen. When platelets come into contact with air, they turn the fribrinogen into threads of fribrin. The threads make a net over the cut 3. Red blood cells get caught in the net and make a blood clot that seals the cut 4. The clot dries to make a scab ((Haemophilia’s a disease - your blood doesnt clot easily))
* Blood clotting prevents a big loss in blood and prevents body from getting infected with viruses in the air
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White blood cells (Not disc-shaped, irregularly shaped, bigger than a red blood cell, has a nucleus, no haemoglobin, made up of lymphocytes and phagocytes)
* Protects body from germs
* Immune system – protects and fights from diseases (virus, bacteria, fungi)
* Made in bone marrow
*Lymphocytes and Phagocytes
>>Antigens recognize foreign cells that don’t belong in the body
>>All cells belonging to the body have antigens or markers on the surface of the cells. This means the immune system recognizes the ‘body’s’ own cells and doesn’t attack them.
>>Lymphocytes recognize foreign cells because they have different antigens. The lymphocyte then release antibodies, which stick to bacteria, and become a lump
>>Phagocytes recognize the lump and gradually engulfs (swallows) the lump. It releases digestive enzymes to destroys the bacteria. It also produces antitoxins to neutralize toxins that microbes produce ((phagocytes can squeeze through thin-walled capillaries to reach bacteria))
The Eye
The eye is an organ adapted to sense light. Each eye lies in a socket of the skull. It is moved by actions of 3 pairs of eye muscles
At the front of the eye is the transparent cornea. Light enters your pupil through here. It then passes through the pupil and the colored iris surrounds the pupil. At the front of the cornea is the conjunctiva. This is a delicate, transparent layer. It is kept moist by tear glands. These make the tears that wash your eye clean every time you blink.
Conjunctiva→ a thin layer that covers the front of the eye, in front of cornea
Cornea→ a clear layer in front of the iris and aqueous humour, which lets light into eye; it helps focus the light
Sclerotic→ tough, white, protective outside layer of the eye
Aqueous Humour→ a clear watery fluid filling the front eye (in front of the iris & lens), behind cornea
Iris→ coloured part that controls the amount of light entering the eye
Pupil→ front (tip) of the lens
Lens→ responsible for fine focus of light onto retina; it is clear and can change shape
Ciliary Muscles→ changes the shape and thickness of the lens during focusing
Suspensory Ligaments→ threads which hold the lens in place
Vitreous Humour→ a clear jelly-like fluid behind iris and around lens and supports the back of the eye
Choroid→ black layer surrounding vitreous humour & contains lot of blood vessels, between retina and sclerotic
Yellow Spot (fovea)→ most sensitive part of retina
Retina→ a layer of cells, which are sensitive to light, between choroids and vitreous humour, change light image into nerve impulses
Blind Spot→ point where the optic nerve attached to the eye, no light sensitive cells here
Optic Nerve→ bundle of nerve fibres, which carry impulses from the retina to the brain
- Dim Light >> Circular muscles relax, radial muscles contract
- Bright Light >> Circular muscles contract, radial muscles relax
- Light rays falling on an object are reflected and some of these reflected rays fall on the eye
- The light rays are refracted (bent) as they pass through the cornea, the aqueous and the lens in the eye
- An upside down (inverted) image is formed onto the retina
* In the retina, rod cells respond to dim light (light intensity) and cone cells detect color and details
- Impulses from the retina pass along the optic nerve and enter the brain. The brain decodes the information and gives you a picture of the object with color and is the right way up.
→Near Objects
Light rays from near objects have to be refracted strongly. A fat lens is needed. When the ciliary body contracts, the ring of ciliary muscles gets smaller, causing the suspensory ligament to relax. This allows the lens to shrink and become fatter.
→Far Objects
Light rays from far objects do not have to be refracted so much. A thin lens is needed. When the ciliary body relaxes, the ring of ciliary muscles gets larger, pulling the suspensory ligament to stretch. This makes the lens thinner.
→Short Sightedness
* Eye ball too long, Fat and short lens (bends light rays too much, it is too fat even when ciliary muscles are relaxing), Image is focused in front of the retina (not touching retina) and image becomes blurred
- causes – tiring muscles in the eyes, reading in the dark, too close to tv
- correction – wearing glasses with a concave (caves inwards) and diverging ( rays spread out) lens
→ Long Sightedness
* Eye ball too short, Long and thin lens (doesn’t bend light rays enough, is too thin even when ciliary muscles are contracting), Image is focuse behind the retina (passed retina) and image becomes blurred
- causes – old age
- correction – wearing glasses with a convex (curves outwards) and converging lens (rays focused) lens
Nervous System
Your nervous system controls your actions and coordinates different parts of your body so that they work together and bring out the right responses.Your nervous system send electrical messgaes along nerves to and from different parts of your body * nerve impulses are messages that nerves carry
Sense Organs (receptors) >> *A reflex is an involuntary, immediate, automatic & fast reaction/response
- Skin – Touch, Temperature
- Ears – Sound (hearing), Balance
- Tongue – Taste (chemicals)
- Eyes – Light
- Nose – Smell (chemicals)
Stimuli / (Stimulus – only one of the changes) – are changes that can be detected e.g. hot temperature from fire
Receptors – detect the changes e.g. hot temperature on skin
Effectors – bring about responses e.g. taking hand away from fire
Central Nervous System (CNS) - Brian, Spinal Cord which are both made of delicate nervous tissue
Neurons – are different from other cells, they do have a cell membrane, cytoplasm and nucleus but they are a different shape, the relay neuron is the connecting neuron, in the CNS, that is between the sensory neuron and the motor neuron *(below spinal cord is the cyactic nerve)
THE REFLEX ARC (CNS, relay neuron –connecting neuron)
Stimulus→→→→Receptor→→→→→→→ Coordinator →→→→→→→Effector Organ→→→→Response
(sensory neuron) (motor neuron)
<<Sensory Neuron>> the direction of the nerve impulse for a sensory neuron is ‘to the right’ →→→
1. A sensory neuron receives nerve impulses from other connecting nerve cells then…………………………
Nerve Ending in a sense organ (receptor) → Nerve Fibre (axon) with Myelin (fatty) Sheath around it as an insulator → Sensory Neuron Cell Body → Nerve Ending (Dendrite) in the central nervous system
* the myelin / fatty sheath insulates the nerve fibre / axon to allow nerve impulses to travel faster through axon
<<Motor Neuron>> the direction of the nerve impulse for a motor neuron is ‘to the right’ →→→
Cell Body in the central nervous system → Nerve Fibre (axon) with Myelin (fatty) Sheath around it as an insulator → Nerve Ending (Dendrite) in a muscle or gland
* the motor neuron connects to receptive organs and muscles
The ends of neurons are not connected. There is a small gap in between them. The end of neurons and the gaps put together are called Synapses. The reason for synapses is because electrical impulses (nerve impulses) can’t “jump” the gap and synapses keep impulses going in the right direction (only one direction)
- When an impulse reaches the end of an axon, a chemical is produced. Mitochondria and chemical transmitters turn nerve impulses into chemicals (neuron transmitter) and diffuse the chemicals across synaptic gap. Then receptors detect neuron transmitter and start off another impulse across next neuron.
- Synapses have two other functions. A resistor and a junction box.
- some drugs block synapses, others can make them work too quickly
- alcohol affects synapses in the brain (slow down people’s reactions)
*motor neuron disease – neuron starts to break down and cannot carry impulses anymore, muscles cannot contract and person is paralysed
There is a synapse between neurons to neurons as well as motor neurons to muscle fibres. For neurons to neurons, it’s a nerve impulse but for motor neurons to muscle fibers, it’s a contraction
Homeostasis * Metabolism is the name for chemical processes that take place in cells in the body
- Keeping a steady or constant rate or maintaining constant internal environment
- Constant temperature – 37 degrees, human enzymes work best then
- Breathing – Oxygen intake and carbon dioxide, concentration of the blood
- Blood Sugar – If go too low or too high brain gets damaged, controlled by liver and pancreas. Insulin (pancreas) is a hormone that controls blood sugar
- Levels of waste disposal
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Water content, water balance – “Osmosis” diffusion of water molecules, from a level of highly concentrated molecule to an area of less concentrated molecules across a semi permeable membrane until there is an equal amount of concentrated water molecules
- PH of blood – Kidney controls this by getting rid of excess ions
>>Water Balance
Solutions In Out
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High in water molecules = dilute Drink Sweat
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Low in water molecule = concentrated Eat Urination, Faeces Exhaling
Water molecules move from a dilute to a concentrated solution. When you eat too much salt or you lose too much water, you’re blood becomes more concentrated and you feel thirsty
- ADH (Antidiuretic Hormone) is a hormone, made in a gland in the brain, that controls water balance.
Receptors detect concentration of blood and send message back to the brain. Brain then releases ADH
- Kidney helps in water balance as well
* No drink for a while – blood becomes more concentrated, ADH is produce, kidney doesn’t absorb much water from blood into nephrons, very little urine is produced, and urine is concentrated
* Drink a lot – blood becomes dilute, ADH is not produced, kidney absorbs more water from blood into nephrons, more urine is produced and urine is dilute
Kidney/Excretion *Kidneys and lungs are the two organs responsible for excreting waste products
Chemicals in your body cells produce waste. This waste includes carbon dioxide and urea. Removing this waste is called Excretion.
Your body cannot store excess amino acids, so they are broken down in the liver to make a waste chemical called Urea. Urea (soluble waste) is made in the liver from access amino acids, which are broken down
The kidney cleans your blood. It filtrates urea, glucose, salts and water. By the end of kidney cycle (remaining chemicals) – concentrated urine which contains urea, water and salts
Renal Artery → Brings waste from blood into kidneys Ureters→ Carry urine down to bladders
Kidneys → Remove urea and other chemicals from the blood Bladder → Stores urine
Renal Vein → Takes ‘cleaned’ blood away from kidneys Ring of muscles → Keep bladder closed
Urethra → Carries urine out of body
Inside each kidney there are thousands of tiny tubes called nephrons. These filter your blood and remove waste chemicals. High-pressured filtration and Re-absorption take place in the nephrons.
>> Nephrons *the Loop of Henle is the loop connecting the first and second coiled tube
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Blood flows through the Glomerulus
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Blood filtered at high pressure (ultra filtration) into the cavity of Bowman’s Capsule (small molecules from the glomerulus filters through the bowman’s capsule)
- Water, urea, salts and glucose enter the capsule; blood cells and proteins stay in the blood (they are big molecules and don’t filter through)
- Filtered blood flows into the capillary network (the renal artery, second coiled tube)
- Useful substances such as glucose are taken back into the blood from the second coiled nephron tube
- Either a small amount or a large amount of water is reabsorbed into the blood in the second coiled tube and the collecting duct depending on the water balance. * ADH is in the second coiled tube to help
- Clean blood flows to the renal vein and out of the kidney * After filtration in the nephrons, the capillaries then carry the ‘clean’ blood away from each nephron and join up to form in the renal vein, where all the glucose, some water and salts are absorbed back into the blood
- Urine containing water, urea and salts are collected in the collecting duct and flow down to the ureters to the bladder. * a function of the urinary system is water regulation
* fine control of water content of the blood takes place in the kidneys due to the action of ADH
* in Renal Dialysis urea and water are removed from the patient’s blood
Skin
The skin is an important sense organ. They protect your body from damage, stop germs from getting into body, stops too much water loss, lets you feel touch/pain/temperature/pressure, helps keep body temperature constant
In the living layers of the skin there are touch and pain receptors. When these receptors are stimulated, they send impulses along the sensory neurons to the central nervous system.
- The skin has two sensory cells, one for pain and one for temperature. The temperature sensory cells are smaller and located nearer to the surface of the skin than the pain sensory cells. The pain sensory cells are a lot bigger than the temperature sensory cells and the pain sensory cells are further into (down) the skin than temperature sensory cells are.
- The upper half (surface) of the skin is called the ‘Epidermis’ and the lower half of skin is called the ‘Dermis”
- How the skin reduces heat loss (to warm body up)
- When it is cold, our skin acts to reduce heat loss.
- The hair erector muscles contract and make hairs stand more upright. This traps warm, still air close to the surface of the skin. Less heat is lost by radiation
- Sweat glands stop making sweat
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Blood vessels near the skin surface get constricted (closer together, narrower). This process is called vasoconstriction (carry less blood). As a result, less blood gets near to the surface. This prevents/reduces heat loss by radiation.
* Shivering helps prevent heat loss. When you shiver, muscles contract quickly and shivering generates heat energy.
- How skin loses heat (to cool body down)
- When it is hot, our skin acts to increase heat loss.
- The hair erector muscles relax and make hairs lie flat against the skin. Less air is trapped near the skin surface. More heat is lost by radiation
- Sweat glands make sweat. This evaporates on skin surface (and cools you)
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Blood vessels near the skin surface get dilated (widens out, bigger). This process is called vasodilation. As a result, more blood gets near to the surface and there is an increase in blood flow. This increases heat loss by radiation. You loss extra heat through your skin, which may appear reddish or flushed
- Vasoconstriction and vasodilation control the flow of blood through the skin and they act as total opposites but work together to help maintain constant body temperature (which helps maintain high level of enzyme activity)
- Temperature control is called thermoregulation. A small part in the brain called the hypothalamus controls thermoregulation. It controls the amount of blood flow near the surface and adjusts to sweat output and activates the shivering response. As a result, heat loss by radiation and convection maybe either increased or decreased
- People exposed to extremely cold conditions may not be able to stop their temperature from going dangerously low. Natural thermoregulation can no longer cope. This condition is known as hypothermia (when internal body temperature falls too low)
Drugs
A drug is a substance that alters the way living things work and a drug affects your nervous system
Some drugs are important to us
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Antibiotics → attacks bacteria
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Heroin (made from poppies) → Relieve pain in people with serious illnesses
Some drugs are addictive, someone can be dependent on it and taking the drug away from them causes withdrawal symptoms like vomiting, dizziness and hallucinations
<Solvents>
Solvents are liquids that dissolve things. Some solvents give off fumes. I the fumes are breathed in, they can affect the brain, causing a light-headed feeling and hallucinations. Solvents are sedatives, they slow down the body’s reactions. They can damage the brain, heart, kidneys, liver and lungs. Abusers may become unconscious, vomit and then suffocate.
<Alcohol>
Alcoholic drinks contain alcohol (ethanol), which affects the brain. A small amount may make the drinker feel more relaxed and confident. However, alcohol slows down reactions, lose the ability to judge things and lose the ability to concentrate. The body starts to lose control over coordination, causing dizziness, slurred speech and difficulty in walking. A drunk maybe argumentative and aggressive. Eventually, unconsciousness and even death can occur. Drinking alcohol affects the ability to drive. People who are addicted to alcohol are known as alcoholics. Alcohol abusers affect the brain, heart, liver and stomach * Alcohol poisons the liver resulting in a disease called cirrhosis.
<Tobacco>
Tobacco smoke contains over 4000 chemicals. Many of them are poisons
- Nicotine is an addictive stimulant. It damages the heart, blood vessels and nerves
- Carbon Monoxide lowers the ability of blood to carry oxygen
- Tar collects in the lungs. It causes cancer
Smoking causes heart disease and cancers of the mouth, throat, lungs and bladder. Smoking also causes other lung diseases, such as emphysema and bronchitis.
* Stimulants – drugs that speed up the nervous system and brain and make you feel more alert e.g. cocaine, ecstasy, amphetamines, caffeine (tea and coffee), nicotine
* Depressants (Sedatives) – are drugs that slow down the nervous system and brain and make you feel sleepy e.g. barbiturates (powerful sedatives which slow the heartbeat and breathing rate), solvents, alcohol
* Hallucinogens - are drugs that confuse (illusions) your nervous system and cause hallucinations such as hearing or seeing things that don’t exists e.g. LSD (Lysergic Acid Diethylamide)
* Painkillers – suppress the parts of the brain that give us the feeling of pain e.g. aspirin, paracetamol, morphine
→ paracetamol is useful for treating mild pain, but overdoses of it cause liver damage and death
→ morphine is given to ease pain in fatally ill patients, but overdoses of it cause heart failure and death
- An analgesic drug reduces pain (another form of painkillers)