Ch 09 Nervous System (a)

7/28/2019 Ch 09 Nervous System (a)

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The Nervous System : communication

A. Neurons = masses of nervecells that transmit information

1. Cell Body - contains the nucleus

and two extensions

2. Dendrites shorter, morenumerous, receive information

3. Axons single, long fiber whichconducts impulse away from the cellbody, sends information


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Nervous System

Central Nervous System (CNS): brain andspinal cord.

Peripheral Nervous System (PNS): nerves of

the body

-- Includes 31 pairs of spinal nerves

-- And 12 pairs of cranial nerves


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Basic Divisions of the Nervous System

Figure 12.2


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THREE BASIC FUNCTIONS OF THE NERVOUS SYSTEM

Sensory - gathers info

Integrative - information is brought togetherMotor - responds to signals, homeostasis


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Motor Functions

Somatic NervousSystem - skeletal(voluntary)

Autonomic NervousSystem - smoothmuscles, glands

(involuntary)


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Neuroglial Cells (p 208)

- support cellsfor the neurons

1. MicroglialCells: scatteredthroughout,digest debris or

bacteria

Microglial cells respond to

immunological alarms


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2. Oligodendrocytes:

provide insulationaround the axons


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3.

Astrocytes: connectblood vessels toneurons

I connect toblood

vessels


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4. Ependymal Cells: form a membrane thatcovers brain-like parts


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5. Schwann cells: form the insulating myelinsheath around the neurons

Practice with neuroglia coloring!
http://www.biologycorner.com/anatomy/nervous/nerve_cells_coloring.htmlhttp://www.biologycorner.com/anatomy/nervous/nerve_cells_coloring.htmlhttp://www.biologycorner.com/anatomy/nervous/nerve_cells_coloring.html


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Supporting Cells - NEUROGLIA


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Supporting Cells- NEUROGLIA


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Neurons


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Axon - long section,transmits impulses

Dendrite - smallextensions from thecell body; receive

information

Neurofibrils - fiberswithin the axon


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Chromatophilic substance (rough ER) - transport

system

Myelin -insulation surrounding axons

Nodes of Ranvier - gaps in the insulation


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White vs Grey Matter

Myelinated (white matter) myelinated axons

Unmyelinated (grey matter) - unmyelinated


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Label


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Interesting Facts about the Neuron

Longevity can live and function for a lifetime

Do not divide fetal neurons lose their ability to undergomitosis; neural stem cells are an exception

High metabolic rate require abundant oxygen and glucose

The nerve fibers of newbornsare unmyelinated - thiscauses their responses to

stimuli to be course andsometimes involve the wholebody. Try surprising a baby!


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Types of Neurons

Functional:Sensory, Motor,

Interneurons

Structural:

(A) Bipolar

(B) Unipolar

(C) Multipolar


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Cell Membrane Potential


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9.5 Cell Membrane Potential

At rest, the inside of a neuron's membrane

has a negative charge. As the figure shows,

a Na+ / K+ pump in the cell membrane

pumps sodium out of the cell and

potassium into it. However, more

potassium ions leak out of the cell. As a

result, the inside of the membrane builds

up a net negative charge relative to the

outside.

Animations of Nerve Impulses

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html


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9.6 Nerve Impulse

Speed of an impulse is proportionate to the DIAMETER of the

AXON.

Greater diameter = faster speed

**Myelinated Axons conduct faster than unmyelinated ones"


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The Synapse

Synapse - junction between two

communicating neurons

Nerve pathway - nerve impulse

travels from neuron to neuron

Synaptic Transmission

Dendrite ->cell body -> along axon

-> synapse (gap)

To complete the signal, a

NEUROTRANSMITTER is

released at the gap to signal the


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http://www.youtube.com/watch?v=A0EyX4lRL2I


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Structure of a Synapses


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Neurotransmitters

Excitatory - increase membrane permeability,

increases chance for threshold to be achieved

Inhibitory - decrease membrane permeability,

decrease chance for threshold to be achieved


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Types of Neurotransmitters

Acetylcholine - stimulates muscle contraction

Monoamines - Norepinephrine & Dopamine

(sense of feeling good, low levels = depression)

Serotonin (sleepiness) and mood

Endorphins (reduce pain, inhibit receptors)


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Drugs that Affect Synapses and Neurotransmitters

Curare - poison made from frog skinand causes paralysis by blocking

Ach receptors at the neuromuscularjunction.


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Strychnine poisoning can be fatal tohumans and animals and can occur byinhalation, swallowing or absorptionthrough eyes or mouth

Strychnine is a neurotoxin which acts as anantagonist of acetylcholine receptors. Itprimarily affects the motor nerves in thespinal cord which control musclecontraction. An impulse is triggered at one

end of a nerve by the binding ofneurotransmitters to the receptors.

Strychnine use by athletes?
http://en.wikipedia.org/wiki/Strychninehttp://en.wikipedia.org/wiki/Strychninehttp://en.wikipedia.org/wiki/Strychnine


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Cocaine, morphine, alcohol, ether and chloroform

Ecstasy

LSD (hallucinogen)


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LSD (hallucinogen)


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Dangers of Ecstasy (MDMA) The most common cause ofEcstasy-related death isoverheating (hyperthermia).MDMA interferes with thebody's ability to regulate its

own body temperature andto see other warning signsallowing the body tooverheat without discomfortespecially when dancing forhours in hot clubs.

The neurotransmitterserotonin isvital in regulating many of our basic

functions. Serotonin is, among otherthings, the feel good neurotransmitterand helps to regulate body temp.

Our brain cells are constantly trying

to bring some amount of serotoninback into the cells and out of thesynapse using serotonin reuptaketransporters.

Ecstasy essentially takes theseupkeep transporters and reversestheir roles. This causes a massiveflood of serotonin from the brain cellsinto the synapse.
http://www.drugs.1emallway.com/mind-works/serotonin.htmhttp://www.drugs.1emallway.com/mind-works/serotonin.htm


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LSD; lysergic acid diethylamide

Actions/Effects: LSD alters the action of the neurotransmitters serotonin,

norepinephrine, and dopamine, triggering extreme changes in brainfunction. Physical effects include increased body temperature, heart rate,and blood pressure. Psychological effects include perceptual and thoughdistortions, hallucinations, delusions, and rapid mood swings.

Cocaine blocks reuptakeof dopamine


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Antidepressants

Zoloft is part of a class of drugs called selective

serotonin reuptake inhibitors, or SSRIs for short. SSRIs act on a specific chemical

within the brain known as serotonin. This is one of

several chemicals used to send messages from onenerve cell to another.
http://depression.emedtv.com/ssris/ssris.html


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http://www.youtube.com/watch?v=6vfSFXKlnO0


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9.8 Impulse Processing

Neuronal pool - groups of neurons that make

hundreds of synaptic connections and worktogether to perform a common function

These "pools" help us

remember sequential tasks,like tying a shoe or riding abike.


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9.9 Types of Nerves

Sensory Nerves - conduct impulses into the brain or

spinal cord

Motor Nerves - carry impulses to muscles of glands

Mixed Nerves - contain both sensory and motor nerves


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Neurons Classified by Function: Sensory vs. Motor Neurons

Figure 12.11


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9.10 Nerve Pathways

Reflex arc - only includes a few neurons

Reflex Behavior - automatic, subconscious responses

Knee-jerk reflex - maintains uprightedness

Withdrawal reflex - avoidance of painful stimuli

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Ch 09 Nervous System (a)