Download The Nervous System Part I

The Nervous System Part I
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The Nervous System: Overview
Nervous System controls/regulates body functions (other organ systems)
using electrical signals for communication):
Sensory input – monitoring stimuli (feel)
Integration – interpretation of sensory input (think)
Motor output – response to stimuli (do)
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Nervous System – includes all neural tissue in the body
Neural tissue – includes 2 types of cells:
1) Neurons – cells that send and receive electrical signals
2) Neuroglia (glial cells) – cells that support and protect neurons
Organs of the Nervous System:
1) Brain and spinal cord
2) Sensory receptors of sense organs (eyes, ears, etc.)
3) Nerves connect nervous system with other systems
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Anatomical Divisions of the Nervous System
Central nervous system (CNS)
• Brain & spinal cord
• Integration and command center
CNS
Brain
Spinal Cord
Peripheral nervous system (PNS)
• Includes all neural tissue outside CNS
• Paired spinal and cranial nerves
• Carries messages to and from the spinal
cord and brain
PNS
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Peripheral Nervous System: Two Functional Divisions
Sensory Division - carries sensory information from senses → to CNS
Motor Division - carries motor commands from CNS → to muscles & organs
Central Nervous System
(brain & spinal cord)
carries info
from senses
Sensory
Division
carries info to
effector organs to
perform a function
Motor
Division
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Motor Division
Two Components:
Somatic nervous system - controls voluntary skeletal muscle contractions
Autonomic nervous system (ANS) – controls involuntary actions
(contractions of smooth & cardiac muscle, glandular secretions)
Central Nervous System
(brain & spinal cord)
carries info
from senses
Sensory
Division
carries info to
effector organs to
perform a function
Motor
Division
Autonomic
(Involuntary)
Somatic
(Voluntary)
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Autonomic nervous system (ANS)
Two Components:
Sympathetic nervous system (SNS) - stimulating effect
• fight or flight
Parasympathetic nervous system (PNS) - relaxing effect
• rest and digest
Motor
Autonomic
(Involuntary)
Parasympathetic NS
Somatic
(Voluntary)
Sympathetic NS
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Central Nervous
System
Brain
Spinal
Cord
Peripheral Nervous
System
Sensory
Motor
Autonomic
(Involuntary)
Parasympathetic NS
Somatic
(Voluntary)
Sympathetic NS
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Neuron Structure
• Structural units of the nervous system
• Plasma membrane functions in
electrical signaling
• Composed of:
• body - contains nucleus & other
organelles
• axon - conducts nerve signals
• dendrites - receive signals from
sensory receptors or other neurons
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Neuroglia (glial cells)
Oligodendrocytes – wrap around CNS axons to form “myelin sheath”
• myelin insulates axons to increase the speed of electrical signals
Schwann cells – surround fibers of the PNS to form “myelin sheath”
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Axon terminal – small swelling at tips of branched end of an axon
Synapse – region of close proximity between two neurons
Presynaptic membrane – membrane of first neuron
Postsynaptic membrane – membrane of next neuron
Synaptic cleft – small gap between presynaptic and postsynaptic neuron
Neurotransmitters – molecules that transmit nerve impulse across a
synapse
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