[BIO] Chapter 11 - Nervous System

© Hee Xin Wei (Copyrighted) Topic 11: Nervous System

Chapter Analysis FOCUS EXAM WEIGHTAGE •Constitute to 0% in Paper 2 in the past 5 years •commonly tested in MCQ •haven't been tested in structured in the past 5 years (MAYBE this year it will be) •one of the three chapters under umbrella topic of Co-ordination and Response in Humans •together with eyes and hormones

brain, spinal cord and nerves neurones reflex action Key Concept

human nervous system Human Nervous System consists of i.Central Nervous System (CNS) consists of the brain and the spinal cord ii.Peripheral nervous system (PNS) consists of the nerves connecting the central nervous system and the rest of the body The role of nervous system: -Help the body to adjust rapidly to any changes in the environment -Enable the various parts of the body to coordinate with one another quickly -Control involuntary actions, actions that cannot be consciously controlled, such as heartbeat, peristalsis, vasoconstriction and reflex actions -Control voluntary actions, actions that are consciously controlled, such as picking up the cookie on the table

human nervous system Stimulus is a change in environment which is detected by receptors CNS then transmits nerve impulses to effector to react to the changes in surroundings) Receptor will produce electrical messages called nerve impulses to send to the central nervous system by neurones Effectorresponse CNS Receptor Stimulus

Nerves •Nerve is a bundle of neurones or nerve cells that transmit nerve impulses •All neurones have (a)A large cell body containing the nucleus and organelles. (b)Dendrons are nerve fibre that conduct nerve impulse towards the cell body of the neurone (c)Axons are nerve fibre that conduct nerve impulses away from the cell body. (d)At the terminal ends of axons and dendrons, the nerve fibre branches. These branches are known as dendrites. Where the axon is connected to muscles, these branches are also known as motor end plates. Three types of neurones 1.Sensory neurones - Transmits nerve impulses from receptors / sense organs to CNS 2.Relay neurones - Transmit nerve impulses from the sensory neurones to the motor neurones; found within the CNS 3.Motor neurones - Transmit nerve impulses from the CNS to the effector muscle cells or gland cells dendrites dendron cell body axon axon terminal

structure of neurones Sensory Neurones Motor Neurones Cell body smooth and roundedRelatively large and irregular shape Dendron Long Short Axon Short Long Axon terminalsTransmit nerve impulses to relay neurones Transmit nerve impulses to the effector Direc&on of signal Sense organs (receptors) Axon terminal Direc&on of signal Effector eg muscles cells Sensory Neurones Motor Neurones

brain and spinal cord Grey matter consists mainly of the cell bodies of neurons. •It forms the outer layers of the brain and the central parts of the spinal cord. White matter co