The Nervous System

The Nervous System

the electrochemical (chemical reactions brought about by electricity) communication system of the body

Neuron

cells of the nervous system

(brain, spinal cord, nerves)

Neurons perform three basic tasks:receive informationcarry informationpass information to the next neuron

Neuron Development

birth 3 months 2 years

Parts of the Neuron

Dendrites DETECT

Parts of the Neuron

Parts of the Neuron

Parts of the Neuron

Parts of the Neuron

Dendrites DETECT

Axons ANNOUNCE

Neurons

Neural Communication:

The Neural Impulse

Action Potential

brief electrical charge that travels down the axon

All-or-None Principle

if a neuron fires it will always fire at the same intensity

doesn’t matter if there is a strong or weak stimulation

Refractory Period

“recharging phase” when a neuron, after firing, cannot generate another action potential

once complete the neuron can fire again

Resting Potential

neuron is at rest & capable of generating an action potential

neuron is set and ready to fire

How are the 3 phases of neuron

communication like a toilet?

Action potential – when you flush an “impulse” is sent down the sewer

pipe

Refractory period – delay after flushing when the toilet can

not be flushed again

Resting Potential – toilet “charged” when there is water in the tank and is capable

of being flushed again

All-or-none-principle – always flushes with the

same intensity no matter how much force you apply to the handle

Review Questions(think! don’t say the answer out loud…yet)

1. What are the three phases of communication within a neuron?

2. What is the all-or-none principle?

Communication Between Neurons

“How do messages travel from one neuron to the next?”

Synapse

neurons do not come into contact with each other

Synapse - tiny, fluid filled gap between the axon terminal of one neuron and the dendrite of another neuron

Neurotransmitters

chemical messengers

travel across the synapse

fit into receptor sites on the dendrite of the next neuron

Neurotransmitters

can stay only in receptor sites designed to fit their shape

serve two functions:1. Excitatory Effect

2. Inhibitory Effect

Excitatory Effect

makes it MORE likely that the receiving neuron will generate an action potential

Inhibitory Effect

makes it LESS likely that the receiving neuron will generate an action potential

Neurotransmitters

Review Questions(think! don’t say the answer out loud…yet)

1. How do messages travel from one neuron to the next?

2. How do neurotransmitters that have an excitatory effect impact neurotransmission? What about an inhibitory effect?

Neurotransmission Simulation

http://www.brainexplorer.org/neurological_control/Neurological_Neurotransmission.shtml#

The Central & Peripheral Nervous Systems

The Nervous System

Central Nervous System (CNS)

brain & spinal cord

brain: where most information processing takes place

spinal cord: main pathway information follows as it enters & leaves the brain

Spinal Cord

Divisions of the Nervous System

Peripheral Nervous System (PNS)

all the nerves that feed into & branch out from the brain & spinal cord

Divisions of the Nervous System

Somatic Nervous System

contains: motor nerves

controls: voluntary movements of skeletal muscles

Divisions of the Nervous System

Autonomic Nervous System

Controls: glands & muscles of the internal organs

monitors the automatic functions (breathing, blood pressure, and digestive processes)

Divisions of the Nervous System

Sympathetic Nervous System

controls: arousal

fight-or-flight response prepares the body to deal with threats or challenges

Divisions of the Nervous System

Parasympathetic Nervous System

controls: calming

brings the body back to a relaxed state

Divisions of the Nervous System