AQA GCSE Biology - Paper 2 Graded A+

AQA GCSE Biology - Paper 2 Graded A+ What is homeostasis? The regulation of the conditions inside your body and cells to maintain a stable internal environment, in response to changes in both internal and external conditions Name three coordination centres The brain, the spinal cord and the pancreas What is negative feedback? When your body brings the level of something (e.g. water or temperature) back to normal if it becomes too high or too low What detects a stimulus? A receptor, e.g. skin receptors detect if something's too hot What produces a response? An effector: Too hot - a gland - secretes hormones Too cold - a muscle - contracts to generate heat What makes up the nervous system? Receptors, sensory neurones, relay neurones, motor neurones, effectors and the central nervous system (CNS) What does the CNS do? In vertebrates, this consists of the brain and spinal cord only In mammals, this is connected to the body by sensory and motor neurones What do the sensory neurones do? They carry information as electrical impulses from the receptors to the CNS What do the motor neurones do? They carry electrical impulses from the CNS to effectors What are effectors? They are muscles/glands that respond to nervous impulses and bring about a change What are receptors? They are cells that detect stimuli There are many different types e.g. taste and sound receptors What are synapses? They are connections between two neurones The nerve signal is transferred by chemicals which diffuse across the gap - the chemicals then set off a new electrical signal to the next neurone What are reflexes? Rapid, automatic responses to certain stimuli that don't involve the conscious part of the brain They reduce your chance of being injured What is a reflex arc? The passage of information in a reflex - from receptor to effector What is the reaction time? The time it takes for you to respond to a stimulus What factors affect your reaction time? Gender, age and drugs What are the different areas of the brain? The cerebral cortex, the medulla & the cerebellum What does the cerebral cortex do? This is the outer wrinkly bit It's responsible for consciousness, memory, intelligence and language What does the medulla do? It controls your unconscious activities, like breathing and your heartbeat What does the cerebellum do? It's responsible for muscle coordination How do scientists study the brain? 1) Studying patients with brain damage 2) Electrically stimulating the brain 3) MRI scans Studying the brain - studying patients with brain damage The effect of brain damage on a certain area will reveal what this part of the brain does, and the impact it has on the patient's life E.g. if the patient struggled to move, you could identify that the cerebellum had been damaged Studying the brain - electrically stimulating the brain This happens when you push a tiny electrode into the tissue and give it a small zap of electricity Stimulating a certain part of the brain will reveal what it does E.g. if the motor area is stimulated, it will cause muscle contraction and movement