Nervous SystemNervous System

1. Function – Receives and sends out info 1. Function – Receives and sends out info from and to the outside and inside your from and to the outside and inside your bodybody

2. Two parts of the Nervous System2. Two parts of the Nervous System

A. Central (CNS) – Brain and Spinal CordA. Central (CNS) – Brain and Spinal Cord

B. Peripheral (PNS) – All of the other B. Peripheral (PNS) – All of the other nerve nerve

cellscells

3.3. Neurons (Nerve Cells)Neurons (Nerve Cells)

A. Cell Body – Contains the nucleusA. Cell Body – Contains the nucleus B. Dendrite – Receives nerve impulseB. Dendrite – Receives nerve impulse C. Axon – Sends the nerve impulse awayC. Axon – Sends the nerve impulse away

D. Myelin – Protects the axon. Allows the D. Myelin – Protects the axon. Allows the nerve impulse to move very fastnerve impulse to move very fast

D. Node of Ranveir – places between the D. Node of Ranveir – places between the myelinated Schwann cells where action myelinated Schwann cells where action potential takes placepotential takes place

Action Potential: https://www.youtube.com/results?search_query=action+potential+in+neurons

4. Synapse – Gap in between to neurons4. Synapse – Gap in between to neurons

5. Nerve Impulse – Signal that moves 5. Nerve Impulse – Signal that moves through the Nervous System.through the Nervous System.

A. Travels in 2 WaysA. Travels in 2 Ways 1. Electrical – As it moves through the 1. Electrical – As it moves through the

neuron. neuron. 2. Chemical – As it moves across a 2. Chemical – As it moves across a

synapse synapse

6. The Pathway6. The Pathway

A. Receptor Cells – Special cells that A. Receptor Cells – Special cells that detect the stimulus from inside or detect the stimulus from inside or

outside your bodyoutside your body 1. Found everywhere in your body.1. Found everywhere in your body. 2. Some are connected to your 2. Some are connected to your

5 senses5 senses

B. Sensory Neurons – Receive the B. Sensory Neurons – Receive the impulse from the receptor cells and pass it impulse from the receptor cells and pass it on to the inter-neuronson to the inter-neurons

C. Interneurons – Neurons found in the C. Interneurons – Neurons found in the spinal cord and brain spinal cord and brain

D. Motor Neurons – Carry the response D. Motor Neurons – Carry the response impulse away from spinal cord to an impulse away from spinal cord to an effectoreffector

E. Effector – A E. Effector – A musclemuscle or a or a glandgland that that receives the response impulsereceives the response impulse

7.7. Reflex ArcReflex Arc Response to a stimulus that does not Response to a stimulus that does not

come from the brain. It comes from the come from the brain. It comes from the Spinal CordSpinal Cord

http://search.live.com/images/results.aspx?q=nervehttp://search.live.com/images/results.aspx?q=nerve%20impulse&FORM=BIRE#focal=efa67884cff46ad340d0c811ff7fcdee&furl=http%3A%2F%20impulse&FORM=BIRE#focal=efa67884cff46ad340d0c811ff7fcdee&furl=http%3A%2F

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You can see in the magnified box that the axon is a bundle of little fibers and the myelin is actually wrapped around it several times liked a rolled up carpet.  Myelin serves some incredibly important functions.  It protects the axon.  It allows an impulse to get from one neuron to another, and it allows that impulse to move very, very fast

1. Sensory Receptors -             structures that detect changes in external & internal environment                modified neurons or epithelial cells that have evolved                              to respond to stimuli  (eye, ear, nose, muscles)

Motor NeuronMotor Neuron

Action Potential

InterneuronInterneuron

    Classes of Sensory ReceptorsClasses of Sensory Receptors chemo-receptorschemo-receptors:  chemicals sense solutes in solvents, taste, smell:  chemicals sense solutes in solvents, taste, smell osmo-receptorsosmo-receptors:  of hypothalmus which monitors blood osmotic :  of hypothalmus which monitors blood osmotic

pressure pressure photo-receptorsphoto-receptors:  light - eye, eyespots, infrared receptors of snakes, :  light - eye, eyespots, infrared receptors of snakes,

etc... etc... thermo-receptorsthermo-receptors:  radiant (heat) energ:  radiant (heat) energ phono-receptorsphono-receptors:  sound waves:  sound waves

     electro-receptors:  detect electric currents... electric eels, etc..     electro-receptors:  detect electric currents... electric eels, etc..     noci-receptors:  pain receptors... naked dendrites of skin      noci-receptors:  pain receptors... naked dendrites of skin (epidermis)(epidermis)     mechano-receptors:  mechanical forces - stretching alters      mechano-receptors:  mechanical forces - stretching alters membrane permeabilitymembrane permeability

Link: parts of the neuronLink: parts of the neuron

In turn, these pathways can be divided according to the direction in which they conduct stimuli:

Afferent system by sensory neurons, which carry impulses from a receptor to the CNS

Efferent system by motor neurons, which carry impulses from the CNS to an effector

Relay system by relay neurons (also called interneurons), which transmit impulses between the sensory and motor neurones.