The Nervous The Nervous SystemSystem

Part IPart I““Not to be confused with Anxiety!”Not to be confused with Anxiety!”

Physiology Standards 9 a-e“Coordinated structures and systems within the body help it to maintain homeostasis despite the changes in the outside environment (homeothermic)”

Physiology Standards 9 a-e

• a) Know how major body systems compliment each other to provide the body with Oxygen and nutrients while removing waste and Carbon Dioxide

• b) Know how the nervous system allows different parts of the body to communicate and receive information from the outside environment

• c) Know how the nervous and endocrine systems regulate conditions in the body using feedback loops

Physiology Standards 9 a-e• d) Know the functions of the nervous system

and the role of neurons in transmitting impulses

• e) Know the role of sensory neurons, interneurons, and motor neurons in sensation, thought, and response

• The The Nervous SystemNervous System controls controls and coordinates functions and coordinates functions throughout the body and throughout the body and “responds” to “responds” to internalinternal and and externalexternal stimulistimuli– ““Your nervous system is how Your nervous system is how

your body communicates within your body communicates within itself and with the outside world”itself and with the outside world”

• StimulusStimulus – (pl. – (pl. stimuli stimuli ) is a ) is a change in environment such as change in environment such as a smell or a noise that is a smell or a noise that is “detected” by an organism“detected” by an organism

Neurons• The nervous system is made up of

millions of cells called neurons

• Messages carried by the nervous system are chemical and electrical signals called impulses

• The cell that transmits impulses is called a neuron

Neurons• There are three types of neuronsthree types of neurons:

– Sensory neurons carry impulses from the sense organs to the spinal cord and the brain

– Motor neurons carry impulses from the brain and spinal cord to muscles and glands

– Interneurons connect sensory and motor neurons and carry impulses between them

Neurons• The largest part of a typical

neuron is called the cell body– Contains the nucleus– Where most metabolic activity takes

place

• Spreading out from the cell body are short, branched extensions called dendrites– Detect impulses from the

environment to the cell body

Neuron Structure

Neurons• The long fiber that carries

impulses away from the cell body is the axon– Ends in a series of small areas called

axon terminals– Some axons have an insulating

membrane called the myelin sheath• The sheath leaves exposed parts of the

axon called nodes where a nerve impulse can “jump” from one node to the next

Neuron Neuron StructureStructure

Axon terminals

Nodes

Myelin sheath

Cell body

Axon

Nucleus

Dendrites

The Synapse• At the end of an

axon the nerve impulse reaches the axon terminal

• The space between two neurons is called the synapse

• A vesicle releases a neurotransmitter that communicates the message to the next neuron

NeurotransmitterNeurotransmitter

Axon terminal

Axon

Direction of Impulse

Vesicle

The Synapse

Nervous System Divisions

• Central Nervous System: “CNS”– Composed of the Brain

and the Spinal Cord

• Peripheral Nervous System: “PNS”– Composed of all of the

nerves that run throughout the body

– Responsible for gathering stimuli to be sent to the CNS

Brain

Spinal cord

Peripheral Nerves