The Nervous The Nervous SystemSystem

Chapter 35Chapter 35

What do you think of when What do you think of when you hear “nervous you hear “nervous

system”?system”?

MC Escher “eye”

Human Body SystemsHuman Body Systems

Our bodies are organized into certain Our bodies are organized into certain levels:levels: Cells Cells TissuesTissues OrgansOrgans Organ SystemsOrgan Systems OrganismOrganism

We have We have 1111 major organ major organ systemssystems

1.1. NervousNervous

2.2. Integumentary Integumentary (skin)(skin)

3.3. RespiratoryRespiratory

4.4. DigestiveDigestive

5.5. ExcretoryExcretory

6.6. SkeletalSkeletal

7.7. MuscularMuscular

8.8. CirculatoryCirculatory

9.9. EndocrineEndocrine

10.10. ReproductiveReproductive

11.11. ImmuneImmune

We have We have 1111 major organ major organ systemssystems

ALL these organs are working ALL these organs are working together to maintain together to maintain

HomeostasisHomeostasis..

The Nervous SystemThe Nervous System

Nervous SystemNervous System = Controls and = Controls and coordinates functions throughout the coordinates functions throughout the body and responds to internal and body and responds to internal and external stimuliexternal stimuli

Axon terminals

Myelin sheath

Nodes

Cell body

Axon

Nucleus

Dendrites

Parts of a NeuronParts of a Neuron NeuronsNeurons = Cells that transmit impulses = Cells that transmit impulses Three types:Three types:

1.1. Sensory NeuronsSensory Neurons = Carry impulses from = Carry impulses from sense organs to the brain and spinal cordsense organs to the brain and spinal cord

2.2. Motor NeuronsMotor Neurons = Carry impulses from the = Carry impulses from the brain and spinal cord to the muscles and brain and spinal cord to the muscles and glandsglands

3.3. Inter NeuronsInter Neurons = Connect sensory and motor = Connect sensory and motor neuronsneurons

Parts of a NeuronParts of a Neuron

DendritesDendrites = The short receptor end of a = The short receptor end of a Neuron. Receives the Neuron. Receives the

impulse.impulse. AxonAxon = The long end that carries the = The long end that carries the

impulse impulse away.away. Myelin sheathMyelin sheath = Surround the axon and = Surround the axon and

insulates it. insulates it.

Axon terminals

Myelin sheath

Nodes

Cell body

Axon

Nucleus

Dendrites

The Nerve ImpulseThe Nerve Impulse

o Our nervous system uses Our nervous system uses NaNa+ +

(sodium) and (sodium) and KK++ (Potassium) ions to (Potassium) ions to transmit an impulse across each transmit an impulse across each nerve cell. nerve cell.

o Also called Also called Na / K pumpNa / K pump..

o An An impulseimpulse begins when a neuron is begins when a neuron is stimulatedstimulated by another neuron or by by another neuron or by the environment.the environment.

The Nerve ImpulseThe Nerve Impulse Our systems Na and K act as a pump to Our systems Na and K act as a pump to

transmittransmit the nerve signal across each the nerve signal across each nerve cell.nerve cell.

Our nerve cells never actually “touch” Our nerve cells never actually “touch” each other. A gap exist between nerve each other. A gap exist between nerve cells called a cells called a synapsesynapse. The . The neurotransmitters must ‘jump’ the gap neurotransmitters must ‘jump’ the gap in order to transmit the impulse to other in order to transmit the impulse to other nerve cells.nerve cells.

*chain-link activity**chain-link activity*

Divisions of the Nervous Divisions of the Nervous SystemSystem

The Central Nervous SystemThe Central Nervous System = = Relays messages, processes and Relays messages, processes and

analyzes information. Includes your analyzes information. Includes your brain and spinal cord. brain and spinal cord.

Parts of the BrainParts of the Brain CerebrumCerebrum = The largest and most = The largest and most

prominent region of the brain.prominent region of the brain. CerebellumCerebellum = The second largest region = The second largest region

and located at the back of the skull.and located at the back of the skull. Brain StemBrain Stem = Connects the brain and the = Connects the brain and the

spinal cord.spinal cord. ThalamusThalamus = Receives messages from all = Receives messages from all

of the sensory receptors and relays them.of the sensory receptors and relays them. HypothalamusHypothalamus = The control center for = The control center for

recognition and analysis of hunger, thirst, recognition and analysis of hunger, thirst, fatigue, anger, and body temperature. fatigue, anger, and body temperature.

Pons

Pituitary gland

Hypothalamus

Cerebrum

Medulla oblongata Spinal cord

Cerebellum

Pineal gland

Thalamus

Parts of the brain Parts of the brain animationanimation

Central Nervous SystemCentral Nervous System Spinal CordSpinal Cord = The main = The main

communication link between the communication link between the brain and the rest of the body. brain and the rest of the body.

Peripheral Nervous SystemPeripheral Nervous System

Peripheral Nervous SystemPeripheral Nervous System = = Transmits impulses from sense Transmits impulses from sense organs to the central nervous system organs to the central nervous system OR to the muscles or glands.OR to the muscles or glands.

Peripheral Nervous SystemPeripheral Nervous System

Every impulse can either be controlled or Every impulse can either be controlled or it can be done automatically without any it can be done automatically without any effort on our part.effort on our part.

SomaticSomatic = Regulates activities that are under = Regulates activities that are under conscious control (like your skeletal muscles)conscious control (like your skeletal muscles)

AutonomicAutonomic = Regulates activities that are = Regulates activities that are automatic or involuntary (your heart beat and automatic or involuntary (your heart beat and breathing)breathing)

The Five Sense ReceptorsThe Five Sense Receptors

1.1. Pain ReceptorsPain Receptors2.2. Thermo receptors Thermo receptors (temperature)(temperature)

3.3. Mechano receptors Mechano receptors (touch, pressure, (touch, pressure, vibrations)vibrations)

4.4. Chemo receptors Chemo receptors (Taste and smell)(Taste and smell)

5.5. Photo receptors Photo receptors (light)(light)

Choroid

Retina

Blood vessels

Optic nerve

Fovea

Vitreous humor

Sclera

Ligaments

Iris

Pupil

Cornea

Aqueous humor

Lens

Muscle

VisionVision

Primary photoreceptors are found in the Primary photoreceptors are found in the eyeseyes. .

RodsRods = Extremely sensitive to light, but they = Extremely sensitive to light, but they do not distinguish different colors.do not distinguish different colors.

ConesCones = Less sensitive than rods, but they do = Less sensitive than rods, but they do respond to light of different colors, thus respond to light of different colors, thus producing color vision.producing color vision.

Choroid

Retina

Optic nerve

Fovea

Vitreous humor

Sclera

Ligaments

Iris

Pupil

Cornea

Aqueous humor

Lens

Muscle

Blood vessels

HearingHearing

Sound vibrations enter the Sound vibrations enter the auditory canalauditory canal. . The vibrations cause the The vibrations cause the TympanumTympanum (or (or eardrum) to vibrate three tiny bones.eardrum) to vibrate three tiny bones.

Those vibrations then lead to the Those vibrations then lead to the CochleaCochlea. It is lines with tiny hair cells that . It is lines with tiny hair cells that are pushed back and forth by these are pushed back and forth by these pressures. pressures.

Questions????Questions????

QUIZQUIZ next time over the next time over the nervous systemnervous system