The NervousThe NervousSystemSystem

The human nervous system….The human nervous system….1. Receives - 1. Receives - stimulus from inter/exter. environ.stimulus from inter/exter. environ.

2. Processes - 2. Processes - message sentmessage sent

3. Stores - 3. Stores - brain remembers stimulusbrain remembers stimulus

4. Transmits - 4. Transmits - brain sends reactive messagebrain sends reactive message

…….information that comes from the various.information that comes from the various

parts of the body (internal) and the externalparts of the body (internal) and the external

world.world.

The Nervous System has 2 main partsThe Nervous System has 2 main parts

The Peripheral The Peripheral Nervous System Nervous System ((PNSPNS))__________________________________

Which is made up ofWhich is made up of

Sensory Motor Sensory Motor NervesNerves

(All over your body)(All over your body)

The Central Nervous The Central Nervous System (System (CNSCNS))________________________________

Which is made up of:Which is made up of:

The Brain andThe Brain and The Spinal CordThe Spinal Cord

What is the Nervous System made of?What is the Nervous System made of?

Neurons! (Nerve Cells)Neurons! (Nerve Cells)– – All of the organs and nerves of the nervous system All of the organs and nerves of the nervous system are made of approximately are made of approximately 100 billion Neurons.100 billion Neurons.

Neurons are special cells that canNeurons are special cells that cansend, receive and transmit electrical send, receive and transmit electrical Messages called nerve impulsesMessages called nerve impulses

Each neuron is made of:Each neuron is made of:

– – DendritesDendrites– – A Cell BodyA Cell Body– – An AxonAn Axon– – Axon TerminalsAxon Terminals

NeuronsNeurons

Real Neuron ImagesReal Neuron Images

Anatomy of a NeuronAnatomy of a Neuron Dendrites:Dendrites: these are “branched” processes these are “branched” processes are specialized to are specialized to receive input receive input and carry information and carry information toward toward the cell body.the cell body.

The Cell Body:The Cell Body:

- - is the metabolic center of the is the metabolic center of the neuron (where energy is made).neuron (where energy is made).- contains the nucleus (center) of the cell- contains the nucleus (center) of the cell- - most proteins needed for functioning are made most proteins needed for functioning are made

herehere- incoming signals from dendrites meet here.- incoming signals from dendrites meet here.

Anatomy of a NeuronAnatomy of a Neuron Axon:Axon:

• is larger in diameter than dendrites.is larger in diameter than dendrites.• is specialized to carry information is specialized to carry information away away from from

the cell body.the cell body.• may be very long, up to 1 meter!may be very long, up to 1 meter!

Axon TerminalsAxon Terminals

• the end of the axon.the end of the axon.• Sends the signal on to other Sends the signal on to other

neurons.neurons.

Draw your own picture of a neuronDraw your own picture of a neuronhere and label the 4 partshere and label the 4 parts

Characteristics of NeuronsCharacteristics of Neurons1) Neurons can be stimulated: they react to1) Neurons can be stimulated: they react to chemical signals by transforming them chemical signals by transforming them

into electrical signals.into electrical signals.

2) Neurons are conductive: they transmit 2) Neurons are conductive: they transmit nerve impulses to other cells.nerve impulses to other cells.

3) Neurons are needy: 3) Neurons are needy: they require greatthey require great amounts of glucose and oxygen toamounts of glucose and oxygen to functionfunction (20% of body’s energy goes to (20% of body’s energy goes to

cells. Neurons will die within minutes cells. Neurons will die within minutes without oxygen).without oxygen).

NeurotransmissionNeurotransmission

How do neurons communicate?How do neurons communicate?• Neurons interact with other neurons through Neurons interact with other neurons through synapses.synapses.

• The axon terminals of one neuron will end near (The axon terminals of one neuron will end near (but but do not touchdo not touch) the dendrites of another neuron.) the dendrites of another neuron.

• • Presynaptic neuronPresynaptic neuron: : sends out informationsends out information

• • Postsynaptic neuronPostsynaptic neuron: : receives informationreceives information

Note:Note: There is no There is no physical connectionphysical connection between the two neurons!between the two neurons!

Synapse and Synapse and Neurotransmitter Intro Video

Nerve ImpulsesNerve ImpulsesWhen a neuron registers an When a neuron registers an internal stimulus internal stimulus (from (from another neuron or a another neuron or a hormone)hormone) or an external or an external stimulus stimulus (such as a sound, (such as a sound, touch, heat, electrical shock, touch, heat, electrical shock, pain, odour)pain, odour) it will produce it will produce an electric current known as an electric current known as a nerve impulse or an action a nerve impulse or an action potential potential (AP).(AP).

The nerve impulseThe nerve impulse travels travels down the axon to thedown the axon to theaxon terminals at speeds up axon terminals at speeds up to to 430 km/h.430 km/h.

Delay reaction Ruler Test:Delay reaction Ruler Test: Delay from sight to brain to finger muscles. Delay from sight to brain to finger muscles.

Fill in the blanks with the following Fill in the blanks with the following words:words:

Relayed, Received, Transmitted, or Relayed, Received, Transmitted, or ProcessedProcessed,,

Nerve impulses are:Nerve impulses are:

1) 1) ___Received ______Received ___by the dendrites;by the dendrites;2) 2) __Processed______Processed____ by the cell body; by the cell body;3) 3) __Transmitted____Transmitted__ through the axon; through the axon;4) 4) ___Relayed______Relayed___ by the axon terminals. by the axon terminals.

Review QuestionsReview Questions

1) What is the main function of the nervous 1) What is the main function of the nervous system?system?

2) What are the 2 main parts of the nervous2) What are the 2 main parts of the nervous

system and how do they differ?system and how do they differ?

3) What is the nervous system made up of?3) What is the nervous system made up of?

4) What are the 4 main parts of the neuron4) What are the 4 main parts of the neuron

and what are their specialized functions?and what are their specialized functions?

5) What is a synapse?5) What is a synapse?

6) Draw a picture of a synapse including pre 6) Draw a picture of a synapse including pre and postsynaptic neurons. Make sure to and postsynaptic neurons. Make sure to label all structures in your diagram.label all structures in your diagram.

7) What are two names for the electric 7) What are two names for the electric current that travels down a neuron?current that travels down a neuron?

8) What is the name of the chemical 8) What is the name of the chemical messengers found at inside the axon messengers found at inside the axon terminal?terminal?

9) What part of the neuron receives the 9) What part of the neuron receives the nerve impulse?nerve impulse?

Question AnswersQuestion Answers

Answers to HW Review QuestionsAnswers to HW Review Questions

1) What is the main function of the nervous1) What is the main function of the nervoussystem?system? The nervous system receives, processes, stores The nervous system receives, processes, stores

and transmits information that comes from and transmits information that comes from parts of the body and the external world.parts of the body and the external world.

2) What are the 2 main parts of the nervous2) What are the 2 main parts of the nervoussystem and how do they differ?system and how do they differ? The central nervous system is composed of the The central nervous system is composed of the

brain and the spinal cord.brain and the spinal cord. The peripheral nervous system is composed ofThe peripheral nervous system is composed of the nerves (motor and sensory) all over yourthe nerves (motor and sensory) all over your body.body.

3) What is the nervous system made up of?3) What is the nervous system made up of?

The nervous system is composed of more than aThe nervous system is composed of more than a billion nerve cells or neurons.billion nerve cells or neurons.

4) What are the 4 main parts of the neuron and4) What are the 4 main parts of the neuron andwhat are their specialized functions?what are their specialized functions? DendritesDendrites: receive inputs from other neurons: receive inputs from other neurons and carry messages to towards the cell and carry messages to towards the cell

body. body. Cell BodyCell Body: Makes energy and proteins for the: Makes energy and proteins for the neuron, processes the inputs from the neuron, processes the inputs from the

dendrites.dendrites. AxonAxon:: transmits the nerve impulse away from transmits the nerve impulse away from the cell body.the cell body. Axon TerminalsAxon Terminals: relays (passes on) the nerve: relays (passes on) the nerve impulse to another neuron.impulse to another neuron.

5) What is a synapse?5) What is a synapse?

The connection between 2 neurons rough which they The connection between 2 neurons rough which they interact.interact.

6) Draw a picture of a synapse including pre and 6) Draw a picture of a synapse including pre and postsynaptic neurons. Make sure to label all structures postsynaptic neurons. Make sure to label all structures in your diagram.in your diagram.

7) What are two names for the electric current 7) What are two names for the electric current that travels down a neuron?that travels down a neuron?-Nerve impulse, action potential (AP)Nerve impulse, action potential (AP)

8) What is the name of the chemical 8) What is the name of the chemical messengers found at inside the axon terminal?messengers found at inside the axon terminal?-NeurotransmittersNeurotransmitters

9) What part of the neuron receives the nerve9) What part of the neuron receives the nerveimpulse?impulse?- the dendrite- the dendrite

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