The Nervous System

Nervous System

• Nervous System: Collects information, processes, and responds to internal and external environment– Quick, short term

changes

Overview of Nervous System

• Stimulus: Something in environment causes a response

• Neuron: Cell that sends messages (neurotransmitters)

• Response: Reaction to environmental conditions

RESPONSE!

synapse

The Neuron• Neurons build into nerves!

Parts of the Neuron

• Dendrites– Receive messages from previous neurons– Send message to cell body

• Cell Body– Contains nucleus and cytoplasm

Parts of the Neuron: Cont’d

• Axon– Long fiber that carries

messages away from the cell body

• Myelin Sheath– Insulating membrane helps

send the signal down the axon

• Nodes of Ranvier– Gaps between Schwann

Cells– Impulse jumps from one

node to next• Schwann Cells

– Cells that make myelin

Parts of the Neuron: Cont’d

• Axon Terminals– Branches at the end of

an axon– Contain synapses

where neurotransmitters are released

Synapses

• Synapse– Space between

neurons– Carry messages or

impulses from one nerve to the next

• Neurotransmitters– Chemical

messages sent between neurons

How does a neuron work? Summary

1. Neurotransmitter received from another neuron goes through cell body

2. Impulse travels down the axon

3. Neurotransmitter released into synapse

4. Neurotransmitter received by protein receptors in dendrites of next neuron

A closer look how an impulse travels down the axon

• Polarization- differences in charge ( + or -)

Resting

• All channels are closed

• High K+ concentration inside, high Na+ outside of axon

• Negative inside (-70 mV)

How an impulse is carried down the axon

Action Potential• Impulse in progress

– Na+ channel opens – High Na+ and K+

concentration inside

– Positive inside (+30 mV)

How does a neuron work?

• http://outreach.mcb.harvard.edu/animations/actionpotential.swf

Types of Neurons

Receptor & Sensory (Afferent) Neurons

(Sensory Organs Spinal Cord and Brain)

Motor & Effector (Efferent) Neurons

(Spinal Cord and Brain Muscles

and Glands)

InterneuronsSends Messages between Nerves (Sensory, Receptor, Motor, and other Interneurons)

Reflex Arc

Receptor

Sensory Neuron

Interneuron

Motor Neuron

Effector(Muscle)

Afferent Neurons

Efferent Neurons

No brain involved!

Spinal Cord

Central Nervous System (CNS)

• Consists of the brain and spinal column

The Spinal Cord

• Gray Matter– Consists of cell bodies

• White Matter– Consists of axons

Parts of the Brain

CorpusCollasum

Meninges- protective covering of the brain/spinal cord

Occipital

Brain Area FunctionMeninges Protection of spinal cord and

brain

Cerebrum Memory center

Cerebellum Coordination and balance

Medulla Involuntary processes

Spinal Cord Nerves from brain

Thalamus Relay center between brain and spinal cord

Hypothalamus Homeostasis- hunger, thirst, hormones

Connects nervous and endocrine systems

Occipital Vision & Hearing

Corpus Collasum Connects left and right brain

Peripheral Nervous System

• Peripheral Nervous System- connects the central nervous system to the rest of the body

• Somatic- voluntary

• Autonomic- involuntary– Parasympathetic- at rest– Sympathetic- fight or flight

Malfunctions

• Meningitis- swelling of meninges

• Cerebral Palsy- birth defect, affects muscle coordination

• Stroke- blood clot to the brain

• Polio- viral illness

• Multiple sclerosis (MS)- break down of myelin sheath- impairs movement

Malfunctions

• Drug Addictions

• Stimulants– Increase the number of neurotransmitters

• Depressants– Decrease the number of neurotransmitters

HONORS EXTENSTION: Other Animals’ Nervous Systems

• Hydra– No brain– Nerve Net– Respond to stimuli

HONORS EXTENSION: Other Animals’ Nervous Systems

• Earthworm– Central Nervous System (CNS)

• Primitive brain – Ganglia- cluster of nerves

• Nerve cord

HONORS EXTENSION: Other Animals’ Nervous Systems

• Grasshopper• Central Nervous

System (CNS)• Sensory Organs

(Antannae, Tympana- ears, cilia, mouth, eyes