Function of the Nervous System

To conduct electrical impulses that allow cells, tissues and organs to detect and respond to stimuli.

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General Structure of Nervous System

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BrainAn organ that serves as the center of the nervous

system. It processes information received from

other parts of the NS.

VertebraOne of the small bones that link

together to form the backbone. It protects

the spinal cord

Spinal CordNerve tissue that relays information from the brain to the body’s nerves

and back.

Spinal NervesNerves that root from the spinal

cord and branch to various parts of the body

Sensory & Motor Neurons

What’s the difference?

NERVE NEURON

A bundle of neurons that transmit the same information

or impulse.

A cell that transmits impulses from cell

to another.

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Structure of the Neuron#5

•Axon transmits nerve impulses from the cell body to other neurons and muscles

•Cell Body contains the nucleus and other organelles of the neuron cell

•Dendrite(receptors) receives nerve impulses from other neurons and transmits them to the cell body

•Myelin Sheathfat substance that wraps around the axon, prevents the electrical impulse from leaving the axon (neurons can cross over each other)

•Axon TerminalReleases neurotransmitters to an

adjacent neuron

Myelin Sheath Coating

Simple Reflex Arc The brain is NOT involved in a simple reflex arc. Pathway description:

1. External stimulus occurs

2. Information is transmitted through a sensory neuron.

3. Information is relayed to an interneuron (found in spinal cord).

4. Information is relayed to a motor neuron.

5. A muscle or gland will respond (ex. muscle contracts or relaxes, sweat, tears, saliva, mucus).

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NEURON COMMUNICATION

Neurotransmitter: chemicals that diffuse across a synapse and binds to receptors on the dendrite of an adjacent neuron.

Synapse: a small gap that exists between the axon of one neuron and the dendrite of another neuron.

https://www.youtube.com/watch?v=p5zFgT4aofA

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Causes an increase in the amount of the NT that is released into a

synapse

NicotineIncreases the amount of dopamine (NT) into a synapse. Dopamine is involved with feelings of pleasure or reward.

Blocks a receptor on a dendrite, preventing a NT from binding to it

Caffeine Binds to adenosine dendrite receptors. Adenosine (NT) is supposed to cause drowsiness.

Prevents a NT from leaving a synapse

Cocaine Increases dopamine levels.

Imitates a NT Marijuana THC binds to receptors and produces the effect of intense pleasure.

How Drugs Affect Neurons

NT = neurotransmitter

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Tolerance & AddictionTolerance: when a person needs more and

more of the same drug to get the same effect, this is because the body becomes less responsive to the drug.

Addiction: physiological or psychological dependence on a drug

Example: A cocaine user’s body builds tolerance to the drug. The body is used to getting high levels of dopamine. As a result the person has to take more of the drug on a continual basis.

3 Major Parts of the Brain

Cerebrum

Brain Stem

Cerebellum

Left Hemisphere

Right Hemisphere

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Largest part of the brain; carries out higher thought

processes

Responsible for balance and muscle

coordination

Connects the brain to the spinal cord

The right side of the brain controls muscles on the left side of the body and vice versa…

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FRONTAL LOBE

Functions: • Decision making

• Concentration• Language processing

• Personality

PARIETAL LOBE

Functions: Processes sensory

input from muscles and skin

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OCCIPITAL LOBE

Function: • Receives visual

input •Image recognition

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TEMPORAL LOBE

Functions: • Short term

memory• Received auditory

input• Speech

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PONS (Top Part of Brain

Stem)

Functions: • Relays signals

between cerebrum and cerebellum

•Plays a role in sleep and dreaming

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MEDULLA OBLONGATA

(Bottom Part of Brain Stem)

Functions: • Relays information between the brain

and spinal cord

•Controls breathing rate, heart rate and

blood pressure

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HYPOTHALAMUS

Function:Regulates the

following: •Body temperature•Water balance•Sleep/wake cycle control•Appetite•Sexual Arousal

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1. Light from the image begins to travel through the pupil to the lens.

2. The iris tissue will change the pupil’s size to allow more or less light in.

3. The lens inverts the light into an upside down image and focuses it on the retina.

4. Rods & cone cells found along the surface of the retina tissue are stimulated by the light.

5. Rod & cone cells relay this sensory information to the optic nerve.

6. The optic nerve sends the sensory information to the occipital lobe.

7. The color and light sensory information is processed by the brain & the image is perceived right-side up.

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Rod & Cone Cell FunctionsRODS Both •CONES

• Adapted for vision in dim light

•Help you detect shape and movement

Light receptor cells in the eye

•Adapted for sharp vision in bright light

•Helps you detect color-Red-Green-Blue

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The auditory nerve transmits stimuli to the brain about SOUND & BALANCE. The following two ear structures

connect to the auditory nerve:

Cochlea: contains hair cell nerve endings essential for hearing.

Semicircular canals: helps determine the sense of equilibrium & balance.

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(EAR DRUM)

Damage Due To Loud Sounds

How Hearing Works

1. Sound waves enter the ear and travel down to the end of the ear canal.

2. Sound waves strike the eardrum and cause it to vibrate3. The sound waves pass to the 3 bones found in the middle ear. 4. The sound waves are changed to a mechanical vibration. 5. Mechanical vibrations cause the fluid in the cochlea to move,

causing the hair cells to bend. 6. The hairs cells stimulate sensory neurons to generate electric

impulses to the auditory nerve.7. The auditory nerve carries impulses from the cochlea to a

relay station in the mid-brain.8. These nerve impulses are then carried on to the temporal

lobe of the brain where the information will be processed.

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Stimuli & Skin Receptors

The skin has sensory receptors (neurons) that detect the following stimuli :

1. Light Touch2. Heavy

Pressure3. Pain4. Heat 5. Cold

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http://www.abpischools.org.uk/res/coResourceImport/modules/skin/en-flash/skinstructure.cfm

Parietal lobe

Parietal lobe

Cerebrum

Hypothalamus

Hypothalamus

Smelling & TastingThe sense of taste &

smell are stimulated by chemicals and often function together.

Structures in the mouth and nasal region involved in this are:Taste budsSensory neuronsOlfactory receptorsOlfactory nerve

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