5 - Homeostasis and Response

• Abstinence: Deliberately refraining from having sexual intercourse
• Accommodation: The process of changing the shape of the lens to focus on near or distant objects
• Adrenaline: A hormone that is produced by the adrenal glands in response to fear or stress which increases the heart rate and boosts the delivery of blood to the brain and muscles as a part of the ‘fight or flight’ response
• Antidiuretic hormone (ADH): A hormone that increases the reabsorption of water in the kidney tubules
• Contraception: Methods used to prevent pregnancy
• Coordination centres: Areas of the body like the brain, spinal cord and pancreas that receive and process information from receptors
• Deamination: A process occurring in the liver that removes the amino group from an amino acid to produce ammonia
• Dialysis: A method of treating kidney failure or disease where the blood is artificially filtered to remove waste and toxins
• Effectors: Muscles or glands which bring about responses which restore optimum levels
• Ethene: A type of plant hormone which controls cell division and the ripening of fruits
• Follicle stimulating hormone (FSH): A female reproductive hormone that causes the maturation of an egg in the ovary
• Geotropism/Gravitropism: A plant’s directional growth response to gravity
• Gibberellins: A type of plant hormone which initiates seed germination
• Gland: A group of cells that secrete chemicals called hormones directly into the bloodstream
• Glucagon: A hormone produced by the pancreas that causes glycogen to be converted into glucose and released into the blood
• Homeostasis: The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
• Hyperopia: A defect of the eye where nearby objects appear out of focus (also called long sightedness)
• In Vitro Fertilisation (IVF): Fertilising a woman’s egg using sperm outside of the body
• Luteinising hormone (LH): A female reproductive hormone that stimulates the release of an egg
• Myopia: A defect of the eye where distant objects appear out of focus (also called short sightedness)
• Negative feedback cycle: A regulatory mechanism that reverses a change
• Oestrogen: The main female reproductive hormone which causes the uterus lining to grow and repair
• Phototropism: A plant’s directional growth response to light
• Receptors: Organs or cells that detect stimuli
• Reflex action: A rapid and automatic response to a stimulus
• Selective reabsorption: Reabsorbing certain useful molecules (like glucose, some ions and water) back into the blood after they have been filtered out
• Stimuli: Changes in the environment
• Target organ: The organ which a hormone acts on to produce an effect
• Testosterone: The main male reproductive hormone produced by the testes and it stimulates sperm production
• The brain: An organ made of billions of interconnected neurones which controls complex behaviour and has different regions that carry out different functions
• The central nervous system (CNS): The brain and spinal cord which coordinate the response of effectors
• 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.