Infections And Responses

• 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.
• The automatic control systems in the human body can involve the nervous system or hormones.
• Patients have to take anti-rejection drugs for the rest of their lives after a kidney transplant.
• Kidney transplant allows patients to lead a normal life.
• Kidney transplant is expensive initially.
• All control systems include receptors, coordination centres and effectors.
• Homeostasis consists of automatic control systems making sure that the internal conditions of the body stay as constant as possible.
• Homeostasis is important for maintaining optimal conditions for enzyme action and all cell functions.
• In the human body homeostasis includes control of blood glucose concentration, body temperature, water levels and mineral ions.
• Receptors are cells that detect stimuli in the internal or external environment.
• Coordination centres are areas that recieve and process the information from receptors and then send out signals to coordinate the response of the body.
• Effectors are muscles or glands that bring about the responses to the stimulus that has been received.
• These responses restore conditions in the body to the optimum level.
• The body detects changes to the internal environment through receptors.
• This information is sent to a coordination centre such as brain which is able to coordinate a response by using chemical substance called hormones.
• The nervous system uses electrical impulses to control our responses to changes in the environment.
• The nervous system consists of two parts: the central nervous system which includes the brain and the spinal cord, and the other nerves running to and from the central nervous system.
• Receptors detect a stimulus and send electrical impulses through neurons to the central nervous system.
• The central nervous system is the coordination centre and it sends electrical impulses down other neurons to effectors and the effector brings about a response.
• Sensory neurons carry impulses from a receptor or sense organ to a coordination centre.
• Motor neurons carry impulses to effectors such as muscles or glands.
• The central nervous system consists of the spinal cord and brain which coordinates responses to stimuli.
• Nerves are bundles of neurons that connect receptors and effectors to the central nervous system.
• Neurons are individual nerve cells that send and receive electrical signals and impulses over long distances within the body.
• When a stimulus is detected by a receptor, electrical impulses pass from the receptor along a sensory neurone to the central nervous system.
• At the end of a sensory neurone there is a junction called a synapse.
• At a synapse the electrical impulse causes the movement of a chemical neurotransmitter, which is released into the gap and diffuses quickly across to the other side.
• Once across, the impulse restarts and enzymes break down the chemical transmitter, ensuring that a nerve impulse can only pass in one direction.
• Stimulus => Receptor => Sensory Neurone => Relay Neurone => Motor Neurone => Effector => Response.
• Relay neurones are situated in the spinal cord and the brain.
• In a spinal reflex the impulse passes from the sensory neurone to the motor neurone through the relay neurone.
• The less neurones involved in a reflex arc, the quicker the reaction.
• The endocrine system consists of glands that secrete chemicals called hormones directly into the blood stream.
• The nervous system uses electrical impulses which travel down neurons.
• The pancreas releases hormones and is involved in controlling the concentration of glucose in the blood.
• The endocrine system tends to produce a much slower effect but the is long lasting.
• Hormones provide chemical coordination and control from the body and are produced by the endocrine gland.
• The blood glucose concentration is monitored and controlled by the pancreas.
• The pancreas produces the hormone insulin, which allows the glucose to move from the blood and into the cells and to be stored as glycogen in the liver and muscles.
• The concentration of glucose in the blood now returns to its normal level.