The nervous system gathers and interprets The nervous system gathers and interprets information about the body’s internal and information about the body’s internal and external environments and response to that external environments and response to that informationinformation

The nervous system keeps your organs working properly and allows you to speak, smell, taste, hear, see, move, think, and experience emotions.

SHHHH, SHHHH, don’t tell him don’t tell him

it smellsit smells

Your nervous system controls and Your nervous system controls and coordinates many things that happen coordinates many things that happen in your body. It acts as a central in your body. It acts as a central command post, collecting and process command post, collecting and process information and making sure information and making sure appropriate information gets sent to all appropriate information gets sent to all parts of the body.parts of the body.

The nervous system is divided into two subdivisions:

The central The central nervous system nervous system (CNS)(CNS)

Peripheral Peripheral nervous system nervous system (PNS(PNS))

The Central The Central Nervous Nervous system (CNS) system (CNS) includes your includes your brain and brain and spinal cord. spinal cord.

It processes It processes all incoming all incoming and outgoing and outgoing messagesmessages

The peripheral nervous system (PNS) consists of communication pathways, or nerves, that connect all areas of your body to your CNS.

A. Central nervous system B. Peripheral nervous systemB1. Somatic nervous systemB2. Autonomic nervous system

Neurons transfer messages throughout your body in the form of fast-moving electrical energy

Electrical Electrical messages messages that pass that pass along the along the neurons neurons are called are called impulses.impulses.

Impulses Impulses may travel may travel as fast as as fast as 150 m/s or 150 m/s or as slow as as slow as 0.2 m/s0.2 m/s

The neuron is the functional unit of the nervous system. Humans have about 100 billion neurons in their brain alone! While variable in size and shape, all neurons have three parts. Dendrites receive information from another cell and transmit the message to the cell body. The cell body contains the nucleus. The axon conducts messages away from the cell body.

Dendrites are short, branched extensions that Dendrites are short, branched extensions that receive information from other cells.receive information from other cells.

A neuron may have many dendrites, allowing it A neuron may have many dendrites, allowing it to receive impulses from thousands of other cellsto receive impulses from thousands of other cells

From the cell body, information is transmitted to other cells by a fiber called an axon. Axons can be very short or quite long.

You have some really long axons that extend almost 1 meter from your lower back to your toes

The end of an The end of an axon often has axon often has branches that branches that allow allow information to information to pass to yet pass to yet more cells.more cells.

The tip of The tip of each branch is each branch is called an axon called an axon terminalterminal

Sensory neurons Sensory neurons typically have a long typically have a long dendrite and short dendrite and short axon, and carry axon, and carry messages from messages from sensory sensory

receptors to the receptors to the

CNSCNS

Sensory neurons have Sensory neurons have specialized dendrites specialized dendrites called receptors that called receptors that detect changes detect changes inside and outside inside and outside the body.the body.

Examples of Sensory Examples of Sensory NeuronsNeurons

Receptors in your eyes Receptors in your eyes

detect the light around youdetect the light around you

Receptors in your Receptors in your stomach stomach let your brain let your brain know when know when your stomach your stomach is full or is full or emptyempty

Motor neurons Motor neurons have have

a long axon and a long axon and

short dendrites short dendrites and and

transmit transmit messages messages

from the central from the central nervous nervous

system to the system to the muscles muscles

(or to glands). (or to glands).

Motor neurons cause the muscles Motor neurons cause the muscles

around your eyes to move when around your eyes to move when

the sensory neurons in your eyes the sensory neurons in your eyes

detect bright light. This movement detect bright light. This movement

makes you squint, which reduces makes you squint, which reduces

the amount of light entering the eyethe amount of light entering the eye

Motor neurons also send Motor neurons also send messages to your gland, messages to your gland, such as sweat glands. such as sweat glands.

These messages tell the These messages tell the sweat sweat glands to release glands to release sweatsweat

The CNS is connected to The CNS is connected to the rest of your body by the rest of your body by nerves. nerves.

A nerve is a bundle of A nerve is a bundle of axonsaxons

Most nerves contain the Most nerves contain the axons of both sensory axons of both sensory and motor neurons.and motor neurons.