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
Top Related