Homeostasis

• Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
• Homeostasis involves keeping the blood glucose concentration, body temperature, and water levels constant in the human body.
• Homeostasis consists of automatic control systems making sure that the internal conditions of the body stay as constant as possible.
• The automatic control systems in the human body can involve the nervous system or hormones.
• Receptor cells detect changes in the environment, which could mean the body's internal conditions such as the concentration of glucose in the blood, or the body's external conditions like the temperature of the skin.
• The receptor cells pass information to a Coordination Center, which could be the brain, the spinal cord, or the pancreas.
• The Coordination Center receives and processes the information from the receptor cells and sends instructions to the effector, which is a muscle or a gland.
• The job of the effector is to carry out the response, which is to store the optimum level.
• The structure of the nervous system is related to its functions.
• The reflex arc is a common concept in the nervous system.
• Reflex actions are important in the nervous system.
• Homeostasis involves automatic control systems and the nervous system is a part of this.
• The nervous system consists of two parts: the Central Nervous System (CNS) which includes the brain and the spinal cord, and other nerves running to and from the central nervous system.
• Receptors detect a stimulus and electrical impulses are sent down new loans to the central nervous system.
• The central nervous system acts as the Coordination Center and sends electrical impulses down other neurons to affect us.
• Effectors are usually a muscle which contracts or a gland which secretes a hormone.
• The nervous system enables humans to react to their surroundings and coordinate their behavior.
• The method for the practical requires people to work together, with person 1 and person 2 measuring the reaction time of person 1 first.
• Person 1 sits on a stool with a good upright posture and places the form of their dominant arm across the table with their hand overhanging the edge.
• Person 2 holds a ruler vertically, with the zero centimeter mark between person one's thumb and first finger.
• Person 2 then tells person one to prepare to catch the ruler.
• Person 2 drops the ruler at a random time, and person one has to catch the ruler with the thumb and first finger as quickly as possible.
• The reaction time is recorded on the ruler that's level with the top of person one's thumb.
• The test is repeated several times and a mean is calculated from these experiments.
• The two people switch places, with person one testing the reaction time of person 2.
• The independent variable in the experiment is the person having the reaction time tested, and the dependent variable is the one that's measured for each change in the independent variable.
• Control variables are ones that we don't allow to change, such as the stool working distance between the thumb and the first finger, measuring the ruler at the top of the thumb, and keeping the conditions in the room the same.
• Other independent variables that could be investigated include practice, where one person catches the ruler a large number of times to see if the reaction time changes depending on the number of tries, and whether the reaction time depends on the hand catching the ruler, with the dominant hand being the hand used most often.
• Chemicals such as caffeine could also be investigated, with the test subject running a measured amount of Cola half an hour before the experiment and comparing this reaction time with their normal reaction time.
• It's important to ensure that the test subject has no medical issue which might be affected by caffeine, such as an allergy or a heart condition.
• The test should be carried out in a lab where hazardous chemicals are not normally used.
• The eye is a sense organ that contains receptors sensitive to both light intensity and color of light.
• The cornea is the transparent front of the eye that starts the focusing of light rays.
• The pupil is the space in the center of the iris which light passes through.
• The iris is the colored part of the eye that controls the size of the pupil.
• The lens focuses the light rays onto the back of the eye.
• The lens can change its shape to allow focus on distant or near objects, a process called accommodation.
• The retina contains receptor cells for light that allow us to detect light intensity and color.
• The receptor cells in the retina send electrical impulses down the optic nerve to the brain.
• The white part of the eye is called the sclera which protects the eye.