Transcript Slide 1

Organization of the
Nervous System
1. Central Nervous System
• The brain + the spinal cord
– The center of integration
and control
2. Peripheral Nervous System
• The nervous system
outside of the brain and
spinal cord
• Consists of:
– 31 Spinal nerves
– 12 Cranial nerves
The Nervous System of a Vertebrate
• Central Nervous System (CNS)
• contains fluid-filled spaces
which contain cerebrospinal
fluid (CSF).
–White matter is composed of
bundles of myelinated axons
–Gray matter consists of
unmyelinated axons, nuclei, and
dendrites.
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White Matter
Gray Matter
Spinal Cord
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• Cerebrum is the most highly evolved
structure in the mammalian brain.
Functions: interpretation, initiating
voluntary movements, storing memory,
retrieving memory, reasoning, center
for intelligence and personality
• Corpus Callosum is the major
connection between the two
hemispheres.
Corpus callosum
Midbrain
Thalamus
Pons
Hypothalamus
Medulla
oblongata
•
Thalamus- leads to cerebral
cortex, channeling impulses to
appropriate part of cerebral cortex
for interpretation
• Hypothalamus- Regulates autonomic
activity involved in thermoregulation,
hunger, thirst, sexual and mating
behavior, etc… part of the limbic
system (emotions)
• The pituitary gland is attached to the
hypothalamus
Structure and Function
• Brain stem--Consists of the medulla
oblongata, pons, and midbrain.
• Medulla Oblongata- Breathing, heart
and blood vessel activity, swallowing,
vomiting, digestion, and relays
information to and from higher brain
centers
• Pons- involved in the regulation of
visceral activities such as breathing
and relays info. to higher brain
Figure 48.28x1 Brain MRI
Mapping Language Areas of the Cerebral
Cortex
Max
Min
The Limbic System: Amygdala, Hippocampus,
Olfactory Bulb
• Midbrain-integration of sensory
information, in the regulation of visual
and auditory reflexes, and relays as
well
• Cerebellum
error-checks and coordinates motor
activities, perceptual and cognitive
factors. Relays sensory information
about joints, muscles, sight, and sound
to the cerebrum. Coordinates motor
commands issued by the cerebrum;
maintains posture
Peripheral Nervous System
• Responsible for communication btwn
the CNS and the rest of the body.
• Can be divided into:
–Sensory Division
• Afferent division
–Conducts impulses from
receptors to the CNS
–Motor Division
• Efferent division
–Conducts impulses from CNS to
effectors (muscles/glands)
Simple Nerve Path
The Knee-Jerk Reflex
Diversity in Nervous Systems
Overview of a Vertebrate Nervous System
Motor Efferent Division
• Can be divided further:
–Somatic Nervous System
• VOLUNTARY (generally)
• Somatic nerve fibers that
conduct impulses from the
CNS to skeletal muscles
–Autonomic Nervous System
• INVOLUNTARY (generally)
• Conducts impulses from the
CNS to smooth muscle, cardiac
muscle, and glands.
Autonomic Nervous System
Parasympathetic and Sympathetic Nervous
Systems
Structure of a Vertebrate Neuron
Neuron Shape is Dependent on
Numbers of Synapses
Axon
Neurons
Types of Neurons
• Sensory Neurons afferent; carry impulses to
CNS
• Interneurons link neurons in the CNS
• Motor Neurons carry impulses away from CNS
to effectors such as muscles and glands
• SUPPORT CELLS Of Nervous System
• Schwann Cells: peripheral nervous system—
produce myelin sheath
• Oligodendrocytes: CNS; myelinating cell
• Astrocytes: CNS; form scar tissue, mop up
excess ions, etc, induce synapse formation,
connect neurons to blood vessels
Synaptic
Transmission
• An AP reaches the
axon terminal and
causes V-gated Ca2+
channels to open.
• Ca2+ rushes in &
initiates NT
exocytosis.
• NTs diffuse across
the synaptic cleft and
then bind to
receptors on the
postsynaptic
membrane and
initiate some sort of
response on the
postsynaptic cell.
Schwann Cells
A Chemical Synapse
Nerve Impulses:
http://highered.mcgrawhill.com/sites/9834092339/student_view0/chapter44/the_nerve_impulse.ht
ml
Transmission Across a Synapse:
http://highered.mcgrawhill.com/sites/9834092339/student_view0/chapter44/transmission_across_a_sy
napse.html
Synaptic Transmission:
http://www.pol2e.com/at34.03.html
Neurons and Synapses
:
http://www.pol2e.com/at34.04.html
The Major Known Neurotransmitters
Put Some Ach Into It!
http://www.pol2e.com/mc34.01.html
Forces Behind Resting Potential
Selective Permeability- some
molecules pass through
membrane more freely than
others; ion channels
Sodium-Potassium Pumptransports 3 Na out of, 2 K into
cell
Result:
Concentration Gradient
Electrical Gradient
The Basis of the Membrane Potential
Resting Membrane Potential:
http://bcs.whfreeman.com/thelifewire/content/chp44/4402001.html
Resting Potential:
http://www.biologyalive.com/life/classes/apbiology/documents/Unit%204/48_Le
ctures_PPT/media/48_10RestingPotential_A.swf
The Sodium-Potassium Pump: a Specific
Case of Active Transport
Sodium-Potassium Exchange Pump:
http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter5/sodiumpotassium_exchange_pump.html
Resting Potential:
http://www.biologyalive.com/life/classes/apbiology/documents/Unit%204/48
_Lectures_PPT/media/48_10RestingPotential_A.swf
Resting Membrane Potential:
http://bcs.whfreeman.com/thelifewire/content/chp44/4402001.html
Voltage-Gated Channels and the Action Potential:
http://highered.mcgraw-hill.com/olc/dl/120107/anim0013.swf
Molecular Basis of Action Potential –
transmission of
a signal along an axon
Sodium channels open once
threshold is reached, influx of
sodium
Potassium channels open at AP
peak; potassium flows out
Generating an Impulse
• polarized membrane: inside is negative relative to
the outside under resting conditions due to distribution
of ions controlled by Na+/K+ pump that require ATP
• Nerve impulse starts when the membrane of the nerve
depolarizes due to some stimulus, chemical, temp.
changes, mechanical, etc….
• Depolarization is caused by the influx of Na+ which
causes the membrane to become more positive.
This starts an action potential, or nerve impulse. They
follow the all or none law!!!
• The membrane will repolarize when K+ leaves the
cell setting the membrane back to resting potential or
polarized
• This de and repolarization continues down the nerve
until it reaches another nerve to pass on the impulse
or until it reaches an effector.
Propagation of the Action Potential
The Action Potential
http://www.pol2e.com/at34.02.html
http://www.biologyalive.com/life/classes/apbiology/documents/Unit%204/48_Le
ctures_PPT/media/48_13ActionPotential_A.swf
Saltatory Conduction
Graded potentials and the action potential in
a neuron
What are the two components of
the Central Nervous System?
What are the two components of the
Peripheral Nervous System?
The two hemispheres of the brain
are connected by the:
Last Review Questions for the Week:
What are the two components of the
Peripheral Nervous System?
What type of response is processed
directly in the spinal cord with no
impulses traveling to the brain?
Which part of the neuron receives
impulses? carries them away?
Describe what occurs at the axon
terminal to cause the transmission
of a nerve impulse from one neuron
to the next.
What is the minimum level of a
stimulus required to cause an action
potential in a neuron called?
What is meant by the term, “all-ornone principle” with regards to the
conduction of nerve impulses?
What is the difference between a
reflex and a normal response?
Draw two neurons side by side and
label the cell bodies, myelin
sheaths, axon terminals, synapse,
nodes, and place of
neurotransmitter secretion.
Describe what happens during an
action potential including
movement of the appropriate ions
across the axon and the correct
charges inside and outside the cell.
Describe the path of a nerve impulse
that would occur when someone
you don’t like touches your hand and
you pull your hand away. Use the
following terms:
motor neurons, hand, interneurons,
sensory neurons, effector (muscle),
brain, spinal cord.