THE NERVOUS THE NERVOUS SYSTEMSYSTEM

HOW DOES IT WORK?HOW DOES IT WORK?

Video: http://www.brainpop.com/health/bodysystems/nervoussystem/

Purpose: Purpose: •Controls and coordinates the body’s Controls and coordinates the body’s response to changes in the environmentresponse to changes in the environment

Why? Why? •Failure to respond may result in disease or Failure to respond may result in disease or deathdeath

How? How? •Uses neurons to send electrical messages (impulses)

A. Stimulus and Response

i. stimuli is a change in the internal or external environment of the body

– Receptors are used to detect stimuli (sensory organs) (ie. Ears, skin, nose, mouth)

ii. response is the way you react to a certain stimuli

•Effectors are organs that produce the response (ie. muscles or glands)

Stimuli Response

Bright light Blink, squint

hunger Salivate, stomach growls

Wasp or bee Swat, move away

Neurons: (nerve cells)

• nerve cells specialized for receiving and transmitting impulses/signals

• functioning units of the nervous system

http://www.brainpop.com/health/bodysystems/neurons/

Axon terminals

Myelin sheath

Nodes

Cell body

Axon

Nucleus

Dendrites

Section 35-2

A Neuron

1. Nerve cell (neuron) “DCATS” – order of impulse

1 = dendrite • Detects stimulus• Starts impulse

2 = cyton (cell body)

Has nucleus

3 = axon (covered by myelin sheath)

• Carries nerve impulses• sheath insulates axon

4 = endbrushes • Terminal branches• Release

neurotransmitters across synapse to another neuron

5 = synapse • The space between neurons where impulses “jump” from one neuron to the next

5

DD

CC

AA

TT

SS

Neurotransmitter

–Chemicals used Chemicals used to help transfer to help transfer the impulse the impulse across the across the synapsesynapse

–Found in tiny Found in tiny sacs (vesicles) sacs (vesicles) at the axon at the axon terminalsterminals

Sensory From sense organs (eyes, nose, skin, ears,

tongue) to brain/spinal cord Interneurons

Interconnect other two types Found in brain and spinal cord

Motor From brain/spinal cord to muscles/glands

http://www.brainpop.com/health/bodysystems/neurons/

3. Nerves – – bundle of neurons that transmits impulses

4. Types of neurons

http://www.dnatube.com/video/2116/Nervous-System-how-it-works

Reflex Arc (Loop)Reflex Arc (Loop)• Quick involuntary Quick involuntary

action that doesn’t action that doesn’t involve the braininvolve the brain

• Neurons may release chemicals to stimulate each other, or these chemicals may be released to stimulate a muscle or gland. 

• An example of a muscle being stimulated by a neuron appears after the reflex path pictured in number four in the diagram.

Receptor

Effector

“RSIME”- order of stimulus

• R- RECEPTOR (DETECTS STIMULUS)- SENSORY ORGAN

• S- SENSORY• I- INTERNEURON

• M- MOTOR NEURON

• E- EFFECTOR (RESPONDS TO STIMULI)- MUSCLE OR GLAND

The Nervous SystemThe Nervous System

How is it made up?How is it made up?http://www.dnatube.com/video/2116/Nervous-System-how-it-works

Divisions of the Nervous SystemDivisions of the Nervous System

• The nervous The nervous system is divided system is divided into into 22 main parts: main parts:– The Central The Central

Nervous Nervous System (CNS)System (CNS)

– The Peripheral The Peripheral Nervous Nervous System (PNS)System (PNS)

http://www.morphonix.com/software/education/science/brain/game/specimens/nervous_system.html

CNSCNS• cerebrum: center for voluntary

activity interprets sensory impulses, initiates some motor activities, and responsible for memory, thinking and reasoning

• cerebellum: coordinates motor activities and aids in maintaining balance

• medulla: controls involuntary activities such as breathing, heartbeat, blood pressure and peristalsis (is part of the brain stem)

• Brain stemBrain stem– Connects brain to spinal Connects brain to spinal

cordcord– Consists ofConsists of

• Medulla oblongataMedulla oblongata (heart (heart rate, etc)rate, etc)

SPINAL CORD

1. Central Nervous System (CNS)

• Consists of the brain Consists of the brain

& spinal cord& spinal cord

2. Peripheral Nervous System (PNS)•Includes all the spinal nerves TWO FUNCTIONS

a) TRANSFER IMPULSES FROM SENSE ORGANS CNS

b) TRANSFER IMPULSES FROM CNS MUSCLES OR GLANDS

D. Nervous System Disorders

• Very serious: the nervous system Very serious: the nervous system CANNOT repair itselfCANNOT repair itself

1. Stroke – cerebral bleeding or clot

2. Parkinson’s disease – missing dopamine (neurotransmitter); movement related problems (ie. Shaky)

3. Alzheimer’s – interference w/ brain neurons causing cognitive problems (memory loss, recognition, etc)

4. Meningitis – bacterial or viral

Pons

Pituitary gland

Hypothalamus

Cerebrum

Medulla oblongata Spinal cord

Cerebellum

Pineal gland

Thalamus

Section 35-3

The Brain

Disorders Stroke

Results from a cerebral hemorrhage or blood clot in a cerebral BV blocking blood flow to brain

Parkinson’s Disease Loss of the functioning of a particular group of

nerve cells in brain May be due to a shortage of dopamine Scientific American Frontiers - Season 3 Prescription

poison

Parkinson’s Disease Symptoms

Shaking Poor balance Lack of coordination Stiffening of Muscles

Cause Triggered by by

environmental factors Genetic tendency

Disorders Alzheimer’s Progressive

degenerative disease that advances over time

Symptoms Memory loss Inability to think,

speak or care for oneself

Multiple Sclerosis Cells in the brain and

spinal cord do not function properly due to destruction of myelin sheath

Symptoms Shaking of hands Blurred vision Slurred speech Muscle weakness Loss of bladder control