paper 2 biology

• the main function of the nervous system is to control and coordinate all activities within an organism
• nervous tissue consists of neurones which are specialised cells that transmit electrical impulses along their length, allowing them to communicate with other nerve cells or muscle cells.
• dendrites receive messages from other neurons
• neurons have three parts - dendrites, cell body (soma) and axon
• myelin sheath insulates axons so they can conduct faster
• synapses are gaps between two neurons where neurotransmitters pass across
• synapses allow communication between neurons
• the cornea refracts light rays to focus on retina
• retina contains photoreceptor cells that detect light
• cone cells detect colour
• rods detect black and white vision
• optic nerve carries impulses from the eye to brain
• rods are sensitive to dim light but not colour
• light sensitive pigments called opsins are found in rod and cone cells
• What is mitosis? A type of cell division which produces 2 identical daughter cells
• Diagram of mitosis
• What is a chromosome? Chromosomes are thin strands of DNA located in the nucleus
• What is homeostasis? Homeostasis is the maintenance of a constant internal environment to maintain optimum conditions for function
• Why is homeostasis important? Homeostasis is important because certain conditions are required for the body to function correctly and if they aren't met, the body could fail
• Examples of homeostasis in the human body - Body temperature - Water levels - Blood glucose levels
• What are receptors? Cells that detect changes in the internal or external environment
• What is a stimuli? A stimuli is a change in the environment
• 3 components of the body's automatic control system - Receptors - Effectors - Coordination centres
• Examples of coordination centres Brain, spinal cord or pancreas
• What is an effector? Muscles or glands that bring about a response to the stimulus that has been received
• What is a coordination centre? Areas that receive and process from the receptors, sending out signals to coordinate a response
• What is a negative feedback loop? A negative feedback control system responds when conditions change from the ideal or set point and returns conditions to this set point. There is a continuous cycle of events in negative feedback.
• Diagram of a negative feedback loop
• Example of negative feedback loop in the body Body temperature is controlled by the hypothalamus in your brain, and if your body gets too hot, your body begins to sweat to try and reduce it. However if the body gets too cold, it begins to shiver to try and raise the temperature.
• Diagram of a nerve cell (neurone)
• Which type of neurone transmits a signal from a sense organ to the central nervous system? Sensory neurones
• What is a synapse? A synapse is the gap at the junction of two neurones.
• What is the nervous system? The nervous system is a system that allows all the parts of the body to communicate with each other, enabling humans to react to their surroundings and to coordinate their behaviour.
• What does the nervous system use to help body parts communicate? Electrical impulses
• What is the CNS (Central Nervous System) made up of? Brain and spinal cord
• What is a motor neurone? A neurone that carries electrical imuplses from the CNS to effectors
• Stimulus response diagram
• Stages of a reflex arc
• What are relay neruones? A relay neuron allows sensory and motor neurons to communicate with each other. They are found in the CNS.
• What is a reflex? A reflex is a rapid automatic response to a stimulus