Homeostasis and Response

• Homeostasis is the regulation of internal conditions of a cell or organism to maintain optimum conditions for function
• Negative Feedback is a system in the body that responds to a change in the environment by returning the system to its original state
• The Nervous System detects and reacts to stimuli and is made up of different parts
• The Central Nervous System (CNS) is made up of the brain and spinal cord.
• Sensory neurones carry information from receptors to the CNS
• Motor neurones carry impulses from the CNS to effectors
• Receptors are cells that detect stimuli
• Effectors are muscles or glands which respond to nerve impulses
• Information is received from receptors, passed through the CNS and then sent to the effectors to carry out the response
• Synapses connect neurones and are the point of communication between neurones
• Reflexes are automatic responses to stimuli that are triggered by the nervous system.
• When a stimulus is detected by a sensory neurone, impulses are sent to a relay neurone in the CNS by releasing chemicals at the synapse
• The Cerebral Cortex in the brain is responsible for higher mental functions such as language, memory, and intelligence.
• The Medulla controls unconscious activities such as breathing and heart rate.
• The Cerebellum is responsible for muscle coordination
• To study the brain, neuroscientists study patients with brain damage, electrically stimulate the brain, or use MRI scans
• The Sclera is the tough wall of the eye
• The Cornea is the transparent layer at the front of the eye that refracts light.
• The Iris is the colored part of the eye that controls the amount of light entering the eye.
• The Lens of the eye is a transparent structure that refracts light and focuses it on the retina
• Shape of the lens is controlled by ciliary muscles and suspensory ligaments
• The Optic Nerve carries impulses from the retina to the brain.
• When we look at nearer objects, the Ciliary Muscles contract and the Suspensory Ligaments slacken allowing the lens to become more rounded so that light rays can be focused onto the Retina
• When we look at distant objects, the Ciliary Muscles relax and the Suspensory Ligaments tighten causing the lens to flatten out so that light rays are not converged but diverge slightly as they pass through the lens
• Long-Sighted means you cannot focus on objects close to you
• Short-Sighted means you cannot see things far away
• Long-Sightedness is caused by the lens being the wrong shape so light isn't refracted enough or the eyeball is too short
• Short-Sightedness is caused when the eye is wrong shape and light is refracted too much or the eyeball is too long
• Vision defects can be treated with contact lenses, laser eye surgery or replacement lens surgery
• Long-Sighted people wear convex lens glasses
• Short-Sighted people wear concave lens glasses
• The Thermoregulatory System in the brain is responsible for maintaining a constant body temperature.
• Some effectors work antagonistically, where one will cool and one will warm
• When you're too hot, sweat is produced from sweat glands and blood vessels vasodilate (blood flows closer to the surface of the skin)
• When you are cold, shivering occurs, hairs stand up on end to create an insulation layer and blood vessels vasoconstrict (blood flow away from the surface of the skin)
• Hormones are chemical messengers sent in the blood
• Hormones are produced and secreted by endocrine glands
• The Pituitary Gland is located in the brain and secretes hormones that control other glands
• Ovaries secrete oestrogen and progesterone, which are involved in the menstrual cycle
• Testes produce testosterone which controls the development of male secondary sex characteristics and sperm production