Gcse aqa biology homeostasis exam 2025

What is homeostatis? - -the regulation of the conditions in our body maintaining stable internal environment What does it do? - -responds to any change in internal or external conditions What are the 3 main components in automatic control systems? - -receptors, coordination centres and effectors What is a stimulus? - -a change in your environment than requires a response Give some examples of stimuli? - -light, sound, touch, pressure, pain, chemical or temperature What do the receptors do? - -detect the stimulus when either temp or water is high or low What happens after the receptors? - -receptors send messages to the cns which organise a response to the effector Give examples of the central nervous system? - -the brain or spinal cord How is the cns connected to the rest of the body? - -through sensory and motor neurones What is an effector? - -muscles or glands that bring about a response What do the muscles and glands do in response? - -muscles contract and glands secrete chemical substances(hormones) What is a sensory neurone? - -neurones that carry information from the receptors to the cns What is a relay neurone? - -neurones that carry impulses from the sensory to the motor neurones What is a motor neurone? - -neurones that carry information from the cns to the effectors What is the nervous system? - -it is what allows you to react to your surroundings Homeostasis Homeostasis What is a synapse? - -it is the nerve signal being transferred by chemicals which move across the gap, sending a electrical signal to the next neurone What is a reflex arc? - -the passage of the information, that brings around a response Responses that reduce body temp- - -hairs lie flat, sweat and blood vessels get wider(vasodilation) Responses that increase body temp- - -hairs stand up, no sweat, shivering and blood vessels constrict(vasoconstriction) What is the body's core temp? - -37 degrees c What is the sclera? - -the tough supporting wall of the eye What is the cornea? - -outer layer, bends light into the eye What is the pupil? - -the hole in the centre where light enters What is the iris? - -controls the diameter of the pupil and how much light enters What is the retina? - -contains receptor cells- one sensitive to light intensity and the other is colour What is the lens? - -focuses the light into the retina What is the ciliary muscles and suspensory ligaments? - -control shape of the lens What is the optic nerve? - -carries impulses from the receptors on the retina to the brain What happens when bright light enters? - -the circular muscles contract and the radial muscles relax, reducing the amount of light that enters What happens in dim light? - -the radial muscles contact and the circular muscles relax What is long sightedness? - -lens or muscles not powerful enough to bring light to focus on retina. Light vocal point is behind retina (convex lens) Bottom diagram is with corrective lenses What is short sightedness? - -naturally too powerful lens, unable to focus on distant objects, refracts light too much(concave lens) Bottom diagram is with corrective lenses Homeostasis Eye lenses when looking into distance - -for distant objects the light does not have to be refracted by a big angle Correct diagram is first one Eye lenses for near objects - -for near objects the light has to be refracted through a big angle. Ciliary muscles contract making the lens thicker Looks like a diamond on its side What is the brain made from? - -millions of interconnected neurones What is the brain in charge of? - -it is in