The Nervous System
The Nervous system receives, processes, stores, and transmits information that comes from various parts of the body and the external world
Neuron and Nerve Impulses The Neuron- a specialized nerve cell in the nervous system that receives and transmits messages Nerve Impulse- an electrical signal transmitted by a neuron Stimulus is anything that can be perceived by a living organism and can trigger a reaction. Ex. Sound, light, heat, odours, electrical shock, hormones
Parts of Neuron Nerve cell with 4 parts: dendrites, a cell body, an axon, axon terminals
Characteristics Can be stimulated, changed into an electrical impulse Conductive: transmits a nerve impulse from neuron to neuron Consumes a great deal of oxygen and glucose
4. People keep same neurons their whole life. 5. Cannot reproduce: Amitotic (not able to divide by mitosis)
Transmission of Nerve Impulses Impulse travels from neuron to neuron until it reaches the target: 1. Dendrites receive stimuli and transform them into nerve impulses. Nerve impulses transmitted along axons to axon terminals Neurotransmitters (chemical substances) secreted by axon terminals across the synapse between two neurons
Synapse Synapse is the transition zone between two neurons that allows a nerve impulse to be transmitted Myelin: Insulating sheath which covers the axon like rubber and plastic on an electrical wire (insulates the impulse)
Synapse
Nerve Axons of neurons can combine to form nerves Nerve: a structure that helps transmit information between the central nervous system and various regions of the body
The Peripheral Nervous System Connects different parts of the body to the central nervous system Made up of all the nerves that run throughout the body
Distribution of Information Stimulus → Sensory receptor→ Sensory Nerve → Central Nervous System (Brain & Spinal) → Motor Nerves→ MUSCLES
Sensory Receptors Specialized nerve cells, that pick up stimuli and turn them into nerve impulses Ex. Smell, sound, muscles stretching etc.
Sensory Nerves Receive and transmit info. from the sense receptors to the central nervous system (CNS) Ex. Sight (optic nerve connected to eye)
Optic Nerve
Motor Nerves Transmit impulses from the CNS to the muscles in order to produce voluntary and involuntary movements (Transmit commands to the muscles to contract) Ex. Light is bright, pupils in eyes contract
Main Parts CNS can be divided into three main parts 1. Brain 2. The Spinal cord
The Brain
Cranial Nerves Brain communicates with the body through pairs of cranial nerves.
Parts of the Brain Cerebrum: control centre of voluntary movement, sensory interpretations and intelligence, centre of emotion
Cerebrum contiued Cerebral cortex- outer layer of grey matter that directs higher functions Ex. Planning, reasoning, logic White Matter- inner layer, made of axons
Cerebrum Functions -Different areas for different sensations and commands Ex. Taste, visual, language etc.
Cerebellum Centre of balance and coordination Regulates the contraction of the proper muscles for specific movements - collects data from parts of body (eyes etc.) - determines force and speed
Brain Stem Controls internal stimuli as well as of involuntary movement Ex. Respiratory, digestive, circulatory etc.
Spinal Cord The spinal cord is a nervous system organ that carries information from the various parts of the body to the brain
Reflexes & Reflex Arc Reflexes - automatic and involuntary reactions - let body perform rapid gestures
Reflex Arc Involve voluntary muscles, which react without the person having to think Spinal reflexes - triggered by the action of the spinal cord - protect body in dangerous situations - reaction quicker than if it had to travel to the brain
Ex. Hand touches hot stove Doctor taps patient’s knee during exam