Homeostasis & Response

• Homeostasis is the maintenance of a constant internal environment.
• Homeostasis involves mechanisms to keep optimum conditions despite internal and external changes, which are needed for enzyme action and all cell functions.
• Homeostasis controls blood glucose concentration, body temperature, water levels, and nervous and hormonal communication is involved in the automatic control systems.
• The nervous system allows us to react to our surroundings, and coordinate actions in response to stimuli.
• Receptor cells convert a stimulus into an electrical impulse.
• The electrical impulse travels along cells called sensory neurons to the central nervous system (CNS).
• In the CNS, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along motor neurons to effectors.
• The effectors carry out the response, which may be muscles contracting or glands secreting hormones.
• Automatic responses which take place before you have time to think are called reflexes.
• Reflexes are important as they prevent the individual from getting hurt because the information travels down a pathway called a reflex arc, allowing vital responses to take place quickly.
• Synapses are the gaps between two neurons.
• When the impulse reaches the end of the first neuron, a chemical is released into the synapse.
• The chemical diffuses across the synapse when the impulse reaches the second neuron, it triggers the impulse to begin again in the next neuron.
• Your reaction time is how long it takes you to respond to a stimulus.
• Cells from the plant are taken and placed in a growth medium containing lots of nutrients.
• Another way to clone a plant is to use tissue culture.
• Gibberellins can be used to increase fruit size, as the seeds in fruit produce gibberellins to increase fruit size.
• Fruit is picked when it is not ripe.
• Seedless fruit is generally smaller due to the presence of gibberellins.
• This reduces wastage as more fruit is suitable to be sold and it does not ripen too early.
• Fruit is firm, which means that during transport it gets less bruised and damaged.
• Hormones such as auxins are added to the growth medium.
• Gibberellins can be used to promote flowering, allowing the plant to flower in any conditions and with bigger flowers.
• When fruit is needed to be sold, it is exposed to ethene and warmer temperatures.
• Seedless fruit can be sprayed with gibberellins to increase their size.
• Gibberellins are used in the brewing industry to increase the germination rate of barley seeds, which is used to make malt.
• Ethene is involved in controlling cell division and stimulates enzymes that result in fruit ripening.
• Ethene controls ripening, it is used in the food industry.
• The cells begin to form roots and shoots.
• Reaction time can be measured with the ruler drop test.
• The brain is made up of many connected neurons and controls complex behaviour.
• The brain is a part of the central nervous system, along with the spinal cord.
• Different regions of the brain control different functions.
• Components of the brain include the cerebral cortex, which controls consciousness, intelligence, memory and language; the cerebellum, which controls fine movement of muscles; and the medulla, which controls unconscious actions such as breathing and heart rate, and is found in the brain stem in front of the cerebellum.
• Investigating brain function and treating brain damage and disease is difficult because the brain is complex and delicate, it can be easily damaged, drugs given to treat diseases cannot always reach the brain because of the membranes that surround it, and it is not fully understood which part of the brain does what.
• Neuroscientists can map out the regions of the brain using a number of methods.
• In dim light, the circular muscles relax and the radial muscles contract to make the pupil larger, so more light can enter to create a better image.
• Human body temperature is 37.5 degrees celsius.
• Electrically stimulating different parts of the brain can be done by pushing an electrode into the brain.
• The eye is a sense organ containing receptors sensitive to light intensity and colour, with many different structures within it.