Communications in the Nervous System

Blueprint was general ideaNow the details

Objectives- THE STUDENT WILL:

• Analyze Parts of the Neuron • create an illustration of a Neuron • Summarize the importance of nerves for the

PERIFRIAL NERVOUS SYSTEM• Explain how neurons communicate

Nervous system components

• Neurons (nerve cells) make up part of N.S• Neurons brain’s communication specialist• 100 billion or more in brain• Held in place by Glia (GLEE-uh)• Glial cells- Greek for glue• 90% of brain is Glia cells

Glia cells cont.

• Neurons with nutrients• Insulate them • Provide protections from toxins• Remove debris when neurons die• Give go ahead to tell neurons to start talking

Diagram of Neuron

Glia=Glue

Structure of the Neuron

• 3 main parts: Dendrites, Cell body, Axon• Dendrites- Greek for Little tree; antennas with

communication with nerve cells• Cell body- shaped like a pyramid or sphere, decides

if neuron FIRES OR NOT, biochemical machinery• Axon- Greek for axel, transmits messages away from

the cell body to other neurons, muscles and glands. Can split and divide into branches= axon terminals

Structure of a neuronDendritesReceive information from other neurons and transmit toward the cell bodyCell bodyKeeps the neuron alive and determines whether it will fireAxonExtending fiber that conducts impulses away from the cell body and transmits to other cells.

chapter 4

Another neuron

More Neuron Structure

• Myelin sheath- Cover for the axons, fatty• Constrictions in the M.S. called nodes• Divide into segments so look like sausage• M.S. also keep signals from adjacent cells out

Myelin sheath

• Also CAN SPEED UP Conduction of Neural impulses

• OR like in multiple sclerosis, loss of Myelin causes erratic nerve signals, leading to loss of sensation, weakening, paralysis, lack of communication, vision weak

Myelin Sheath

Peripheral Nervous System OB #3

• Fibers of individual neurons (axons, dendrites)• Collect and bundle together called Nerves• Like lines in a telephone cable• Human body has 43 pairs of Peripheral nerves

Nerves Cont.

• Left/right side of body• Most enter or leave spinal cord• However; 12 pairs in the head, Cranial

nerves, connect to the brain. • SO Senses : Smell, taste

Stem Cell Controversy

• 1990 Mammals can produce CNS cells after infancy

• Human brain and body organs have such cells• Called stem cells• In animal studies, Can reproduce if exercise,

die if stress or nicotine• Controversy; Scientist use aborted fetuses and

test tube embryos

Neurons in the news

Neural regenerationThe ability of neurons to grow back after injury or damageStem cellsImmature cells that renew themselves and have the potential to develop into mature cells

chapter 4

How Neurons Communicate

• Separated by synaptic cleft, neurons don’t touch

• Axon terminal and one neuron almost touch• Synaptic cleft + axon terminal+ covering

membrane= synapse

How neurons communicate

Axon terminals release neurotransmitter.

Neurotransmitter enters synapse.

Neurotransmitter binds to receptors that it fits.

chapter 4

Synapse

This is how NEURONS TALK

• Action potential- When a nerve cell is stimulated, creates electrical voltage.

• Like fuse on firecracker• Neurotransmitter- neural impulse reaches

axon terminal, must reach across synaptic cleft, synaptic vessels, reach axon terminal= release a few thousand neurotransmitters

• Excitatory (good) inhibitory (neg)

Action potentialA brief change in electrical voltage that occurs between the inside and outside of an axon when a neuron is stimulated.

chapter 4

NeurotransmitterChemical released by a transmitting neuron at the synapse and capable of affecting the activity of a receiving neuron

chapter 4

Neurotransmitter crossing a synapse

Summary

• Parts of Neuron• How do they communicate?