Nervous System

NERVOUSNERVOUS

SYSTEMSYSTEM

Background and Development

• http://www.pennmedicine.org/encyclopedia/em_DisplayAnimation.aspx?gcid=000090&ptid=17

Neuron

• Cell of the nervous system

• Structural and functional unit of nervous system

• React to physical and chemical changes in surroundings

Nerve impulse

• Transmission of information by electrochemical changes

Nerve Fibers

• Highways for impulses to travel

Central Nervous system (CNS)

• Brain and spinal cord

Peripheral nervous system (PNS)

• Made of the nerves that connect the CNS to other body parts

Draw a neuron

• Draw and label a neuron in your notes

• Regular: p. 216

• Honors: p. 359

Parts of a neuron

• Cell Body- contains the nucleus, cytoplasm, cell membrane, mitochondria, and other organelles

Parts of a neuron

• Dendrite- type of branched nerve fiber

• The “fingers” of the neuron, or main receptor sites

Parts of a neuron

• Axon- nerve fiber that conducts impulses away from the cell body

Parts of a Neuron

• Axon Terminal-The “end” of one neuron, a connection is made with another neuron

Model it!- Neuron Dance

Parts of a neuron

• Myelin sheath (Schwann cells)- cells wrapped around the axon like a bandage

• Nodes of Ranvier- narrow gaps in the myelin sheath

Grey vs. White Matter

Grey matter- unmyelinated nerve tissue– Appears grey, slower transmission of nerve

impulses

White matter- Myelinated nerve tissue- Appears white, faster transmission of nerve

impulses

Lets Practice!

• The Myelin Race

Example Drawing

• Regular: p. 228 or p. 229

• Honors: p. 394 or p.395

• Draw and label with: stimulus, receptor, sensory neuron, interneuron, motor neuron, effector, and response

Reflex arc

Testing Reflexes

• Reflex investigationhttp://meded.ucsd.edu/clinicalmed/neuro3.htm

Create this data table in your notes:Reflex Test Receptor site Response

Knee-jerk

Middle finger

Babinski

Other tendon

Pupillary

Other Reflexes

Stimulus Response

The aroma of your favorite food

Salivation

A nasty odor Nausea

A bright light shining in your eye

Pupils get smaller

An insect flying towards your eye

Blinking

Types of Receptors

• Chemoreceptors- sensitive to chemical concentrations

• Pain Receptors- sensitive to tissue damage

• Thermoreceptors- sensitive to temperature

• Mechanoreceptors- changes in pressure or movement

• Photoreceptors- light energy

Testing Mechanoreceptors

• Homunculus Man

Key Chemical Players

• Potassium (K+): pass through cell membranes more easily than sodium

• Sodium (Na+)

• Calcium (Ca2+)

Cell membrane potential

• The surface of a cell (the cell membrane) is usually electrically charged

• Has pumps to keep chemicals in balance (sodium/potassium pumps)

Outside cell: Overall more +

Inside cell membrane: overall more -Cell membrane (bilayer)

Inside cell: overall more +

Resting potential

• When the cell membrane is undisturbed there is a difference in electrical charge

• More sodium is outside than potassium

• More potassium inside than out

Cell membrane

More Na+ = ( +)

More K+ = ( -)

Steps of action potential

• 1) threshold reached (stimulated)• 2) Channels open for sodium to rush in

(they are attracted to the negative inside)• 3) membrane becomes depolarized, or

looses its negative charge• 4) Channels open for potassium to flow

out of the membrane• 5) membrane becomes repolarized, or is

negative again

Parts of the brain

Exit Ticket

• With someone near you, discuss the importance of having reflexes in the body.

• Write a one paragraph summary of your conversation. Why are reflexes important?