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Copy of COORDINATION IGCSE Biology
Transcript of Copy of COORDINATION IGCSE Biology
stimuli: or rather the response to stimulus.....
To response to any sort of sensation you must have...... Receptor:
Sense organs which have groups of receptor cells responding to specific stimuli: light, sound,
touch, temperature and chemicals Glands can be receptors also! If they get a chemical signal [eg a hormone released from another gland]..they might respond and produce their own hormone leading to the production of something...eg. insulin To achieve co-ordination within the body we use two systems:
Nervous system: sends electrical impulses along nerves. Responses are rapid and precise.
Endocrine system: endocrines glands release chemicals called hormones that are carried by the bloodstream until they reach the target organ. They are later inactivated and excreted. Responses are slower. 2. Types of neurons: Neurons, like other cells, have
a cell membrane, nucleus, and cytoplasm. The look very different than regular body cells though. They are adapted to carry signal messages quickly. What is a reflex? *it is when a stimulus causes you to activate a motor response.
eg: pulling hand away from a hot pan. You don't actually have to think about it as it is a reflex...
It is the pathway from the sensory neurone to the relay neurone and back to the motor neurone (the motor neurone will tell the muscle to contract=response) A reflex action = an involuntary response.
Can you think of some other involuntary actions? Do you need to think about your heart beating?
Do you need to make yourself breathe?
Does your pupil contract and dilate on its own?
Do you need to get telling the food to move along the digestive system?
Do you need to tell your pancreas to make insulin?
How about blinking? What are some examples of a voluntary response???
What are the senses? TERMS TO KNOW:
Aqueous humor (has salts to nourish the lens)
Vitreous humor (fluid is very thick and support shape of eye)
Fovea (part of retina where light is focus when looking straight on an object)
Retina (screen at back of eye)
Sclera (very tough-outside of back of eyeball)
The conjunctiva gets tears from the tear gland to stay moist. The tears have lysozymes (enzymes that kill bacteria) The retina has specialized cells of rods and cones to see black and white shades and color. Rods are B/w and easier to stimulate. You need much more light energy to stimulate the cones to see color. Cones are found tightly bunched together in the center areas of the retina. This area is called the Fovea (yellow spot).
Cones allow sharp vision and more details because they have more pixels(spots).
The Fovea offers the maximum sharpness in bright light
Rods on the other hand, are loosely packed and more around the other areas. So peripheral vision is B/w! Light intensity conrtorl:
IRIS: Adjusts the amount of light by makin the pupil smaller or larger (The hole which light travels through).
This is accomplished by circular muscles in the iris.
These round muscles are called radial muscles.
This is an example of a reflecx action. pupil reflex:
When the radial muscle of the iris contract quickly causing the pupils to contract(small).
Both cornea and (especially) the lens (which changes shape) bends the light rays to a focus on the eye. This is called REFRACTION.
Ciliary muscle change the shape of the lens, while the suspensory muscle hole the edges of the lens. There are two ways the eye can focus light:
The process of the focusing of light coming from different distances on the retina.
All muscles need to get a good blood supply to bring glucose and oxygen. Remember the by products of respiration but also anaerobic muscle respiration. 5. ENDOCRINE SYSTEM Endocrine glands release chemicals called hormones that go directly into the bloodstream.
Hormones pass a massages onto target (specific) organs. They alter the activity within the target organ(s).
Once hormones are no longer needed they are destroyed by the liver.
Hormones can produce long-term changes such as puberty and pregnancy and can affect many organs at once. Hormone: a chemical substance produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver. One example of a hormone is Adrenaline.
Adrenaline is produces in the adrenal glands.
It is one of the "fight or flight" hormones Adrenal glands are found above each kidney.
The adrenal medulla (inner zone) produces adrenaline in responses to a stressful situation.
Adrenaline allows a quick response in dangerous situations when you have to run away or put up struggle:
Increases the pulse rate: so the heart provides more oxygen to your brain and muscles.
Causes the liver to release glucose to the blood to obtain energy where needed. The use of hormones in animals we harvest. eg: bovine somatotrophin or BST. Leads to more milk production. You should read about the ramifications of using BST...i.e.: -Pro's and Con's 5.2 THE PANCREAS AND GLUCOSE CONTROL Auxins: plant hormones that cause growth. They regulate de geotropism and the phototropism in plants.
Geotropism: response in which a plant grows towards or
away from gravity.
Phototropism? Auxins are made in the plant cells. But made in the tip of the plant and diffuse downwards to rest of growing shoot.
---->Light shinning onto a plant from the side, makes the opposite side grown faster and bend toward the light... In the previous figure, auxins have collected in the shady part of the stem or shoot making the side grow faster and bending towards the light... Plants become etiolated in the dark.
i.e. grow abnormally tall and thin and yellowish. The chloroplasts can't develop properly in the dark. No matter how you orientate a seed when planting..., the radicle (the first growth out of the seed) will go downwards and form the root. Plant hormones are used in food production.
increased yield=more food
some weed killers actually make the week grow with auxins to a point they die. Ethene gas (is an odd type of hormone-like substance)------------------->used to rippen fruit. As fruit is rippening they give off natural ethene gas. So if you want an avocado or guava to rippen faster, put them in a bag to trap the gas. 1. PARTS OF THE NERVOUS SYSTEM 1. CENTRAL NERVOUS SYSTEM
3. SENSORY IMPULSES.
4. MOTOR IMPULSES.
5. PERIPHERAL NERVOUS SYSTEM. 1. CENTRAL NERVOUS SYSTEM: formed by the brain and the spinal cord. Nerves carry electrical impulses from it to all parts of the body.
Spinal cord: consists of thousands of nerve cells, cell bodies in the grey matter and nerve fibres in white matter.
Medulla: involved in reflex actions.
Cerebellum: involved in co-ordination.
Cerebrum: largest part with two hemispheres, involved in intelligence, memory, skills... 2. EFFECTORS: glands and muscles. They go into action when they receive hormones or nerve impulses 3. SENSORY IMPULSES: impulses from sense organs to the CNS, they detect changes in the environment 4. MOTOR IMPULSES: impulses from CNS to the effectors resulting in an action 5. PERIPHERAL NERVOUS SYSTEM: all of the nerves that connect the body to the central nervous system. You need to be able to distinguish between the three neuron types in diagrams of them. Sensory neurones:carry impulses from the sense organs to the CNS (respond to stimulus)
Motor neurones: carry impulses from CNS to muscles and glands (effectors)
Relay, multi-polar or interneurones: transfer impulses from neurone to neurone. Located in the CNS to skin receptor to CNS 3. PARTS OF NEURONES Dendrites: Collects information from other nerves
Cell body: Contains the nucleus and controls the cell metabolism.
Axon: long: A long fiber which carries information away from the cell body
Myelin sheath: insulates the nerve impulse
Synapse: the region where impulses cross from one neurone to the next.
End plate: Synapses with anther nerve cell, muscle or a gland. 4. Reflex Arc: Situations in which adrenaline secretion increases
Sports: competitions, extreme sports...
Stressful situations: taking examinations, giving a public performance... The hormone-producing cells of pancreas are arranged in Islets, they secrete glucagon or insulin. This is a good example of homeostasis (constant maintenance of the body environment) and negative feedback. Blood sugar levels Blood sugar levels Islets produce glucagon Liver cells convert glycogen into glucose Islets produce insulin Liver cells take up glucose and store it as glycogen If anything goes wrong with insulin production the person shows DIABETES Example of homeostasis and negative feedback 6. Plant hormones Islets produce insulin Liver cells break down glycogen to glucose Blood sugar levels How does the eye always produce a clear image? The eye must focus the optium amount of light on the retina (preference for the Fovea)