Nervous system gcse O levels

• Nervous system is divided into the Central Nervous system (CNS) and the peripheral Nervous system (PNS)
• The CNS consists of the brain and spinal cord
• The PNS consists of nerves that connect to the CNS, sensory neurons which carry information from receptors to the CNS, motor neurons which carry impulses away from the CNS to effector organs such as muscles or glands.
• Messages pass along neurons in form of electrical impulses, called action potentials
• Neurone - individual nerve cells
• Sensory neurones - carry messages towards the central nervous system
• Motor neurones - carry messages away from the central nervous system
• Reflex arc - pathway by which stimulus causes an automatic response without conscious thought
• Receptor - detects change in environment
• Reflex arc - pathway by which stimulus is transmitted through the nervous system without conscious thought
• Axon - long thin part that carries message to next cell
• Dendrite - short branching parts that receive signals from other neurones
• Cell body - contains nucleus and cytoplasm
• Synapse - gap between two cells where chemical messenger crosses
• Synapse - junction between two nerve cells where impulse passes across gap
• Neurotransmitter - chemical released at synapses, binds with receptors on postsynaptic membrane
• Action potential - electrical signal sent along axons
• Myelin sheath - insulating layer around axon
• Sensory neurones - carry messages towards the central nervous system
• Dendrite - short branching parts that receive signals from other neurones
• Neurotransmitter - chemical released at synapses, binds with receptors on target cell
• Threshold level - minimum strength required for an action potential to be generated
• Voluntary actions require a conscious decision by the brain– the organism has a choice in the selection of the response
• The autonomic nervous system controls involuntary actions such as heart rate, breathing rate, digestion etc.
• Involuntary actions are not under our control – they happen automatically without us having any say over them.
• Sympathetic division increases activity (fight or flight)
• Reflex arc is a simple neural pathway which allows rapid responses without involving higher centres of the CNS
• Parasympathetic division decreases activity (rest and digest)
• Effector include muscles (which are made to contract) and glands (which are made to secrete)
• A receptor is part of nervous system that is adapted to receive stimuli
• Photoreceptors, respond to light and are found in rod cells in retina of eye
• Chemoreceptors, respond to chemicals and are found in taste buds
• Thermoreceptors, respond to changes in temperature and are found in skin, muscles and blood vessles
• Mechanoreceptors, respond to mechanical changes such as changes in length and are found in Hair cells near ear (hearing and balance), touch receptors in skin
• Receptors are transducers that convert a stimuli into nerve impulse
• Transducers convert one form of energy into another