Download Central Nervous System Honors Biology Mr. Lee Room 320

Nervous System
Honors Biology
Facilitator: Mr. Lee
Room 320
Objectives
• Describe how the nervous system helps the
body maintain homeostasis
• Summarize the functions of the:
–
–
–
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Cerebrum
Brain stem
Cerebellum
Spinal Cord
• Describe the structure of a neuron
• Describe how a nerve impulse is
transmitted
Introduction
• The nervous system controls many
functions of the body needed for
homeostasis
• Neurons are the specialized cells that
make up the nervous system
– There are two major divisions of the
nervous system:
– Central nervous system
– Peripheral nervous system
Nervous system
Introduction…
• Central nervous system:
– Relays messages, processes information
& analyzes information
– Includes the brain and spinal cord
• Peripheral nervous system:
– Includes all the neurons besides ones in
the brain and spinal cord
– Sensory (afferent) neurons collect
information from the body and transmit
toward the CNS
– Motor (efferent) neurons transmit
information away from the CNS
Brain
• Contains about 100 billion neurons
• Has a mass of about 1.4 kilograms
• Cerebrum:
– Largest region of the brain
– Responsible for voluntary, or
conscious activities of the body
– Site of intelligence, learning,
and judgment
– A deep grove divides the
cerebrum into the right and left
hemispheres
Brain Stem
• Links the cerebrum with the spinal
cord
• Upper Brain stem-Diencephalon:
– Thalamus directs most incoming
sensory signals to the proper
region of the cerebral cortex
– Hypothalamus controls a lot of
hormone production
– Part of the limbic system:
• Also includes parts of the
cerebral cortex and temporal
lobes
• Important role in emotions,
memory, and motivation
Brain Stem…
• Lower Brain stem:
– Three main divisions:
• Midbrain-relay center for visual &
auditory information
• Pons- relay center between the neurons
of the cerebral hemispheres & cerebellum
• Medulla oblongata- both a relay center &
controls things like heart rate and
respiration
– Reticular formation:
• Network of neurons that goes throughout
the brain stem
• Helps controls respiration, circulation, and
filters incoming signals
Cerebellum
•
•
•
•
Located below the occipital lobes
Coordinates muscle actions
Processes information about body position
Works with brain stem motor centers and
cerebral cortex for motor responses
(stimulates or inhibits skeletal muscle
contractions)
The Spinal Cord
• Connects the brain with the rest of the
nervous system
• Starts in the medulla oblongata and runs
down the vertebral column
• Has an outer sheath of white matter made
mainly of axons of neurons
• There is a rigid inner core of gray matter
made mainly of the cell bodies of neurons
Reflex Arc
Neurons
• Messages carried by the nervous system
are electrical signals called impulses
• Neurons are the type of cell that transmits
these impulses
• Action potential- transmission of a signal
along the axon of a neuron
Neurons…
• There are three classification of neurons:
– Sensory neurons- carry impulses from
the sense organs to the spinal cord and
brain (CNS)
– Motor neurons- carries impulses from
the brain and the spinal cord (CNS) to
muscles and glands
– Interneurons- connects sensory and
motor neurons and carries impulses
between them
Neuron Structure
• Cell body- largest part of a typical neuron
– Has a nucleus and cytoplasm
– Most of the metabolic activity of the
cell takes place in the cell body
• Dendrites- short-branched extensions
spreading out from the cell body
– Receive action potential from other
neurons
Neuron Structure…
• Axon- long fiber that
carries impulses away from
the cell body
– The ends are called axon
terminals
Neuron Structure…
• Myelin sheath:
– Lipid layer that covers most
axons
– Insulates the axon
– Speeds up transmission of
action potential
– Produced by Schwann cells in
the peripheral nervous
system
– Nodes of Ranvier- gaps in the
myelin sheath
Neuron Structure…
• Synaptic cleft:
– Small gap between the end of
the axon or one neuron and the
dendrite or cell body of another
– Neurotransmitters:
• Chemicals that are released in
the synaptic cleft
• They cause electrical activity
in the second neuron
Review
• Describe how the nervous system helps the body
maintain homeostasis:
– The nervous system helps to control the bodies
functions.
• Summarize the functions of the:
– Cerebrum:
• Responsible for voluntary, or conscious activities
of the body
• Site of intelligence, learning, and judgment
– Brain stem:
• Links the cerebrum with the spinal cord
• Controls many basic body functions
– Cerebellum:
• Coordinates muscle actions
– Spinal Cord:
• Connects the brain with the rest of the nervous
system
Review…
• Describe the structure of a neuron:
– Cell body- largest part of a typical
neuron
– Dendrites- short-branched extensions
spreading out from the cell body
– Axon- long fiber that carries impulses
away from the cell body
– Myelin sheath- lipid layer that covers
most axons
Review…
• Describe how a nerve impulse is transmitted:
– Neurotransmitters:
• Chemicals that are released in the
synaptic cleft
• They cause electrical activity in the
second neuron
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