Download Central Nervous System (CNS)

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
• 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
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Corpus callosum
Midbrain
Thalamus
Pons
Hypothalamus
Medulla
oblongata
Figure 48.28x1 Brain MRI
Mapping Language Areas of the Cerebral
Cortex
Max
Min
Figure 48.27 The limbic system
Structure and Function
• Brain stem--Consists of the medulla oblongata,
pons, and midbrain.
Functions in homeostasis, coordination of
movement, conduction of impulses to higher
brain centers
• 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
• Midbrain-integration of sensory
information, in the regulation of visual
and auditory reflexes, and relays as
well
• Cerebellum
Functions to error-check and coordinate
motor activities, and 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
Diencephalon:
•
Thalamus- gateway for sensory
impulses heading to cerebral cortex,
receives all sensory impulses (except
smell), and channels 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
• 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.
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
Figure 48.3 The knee-jerk reflex
The nervous system of a vertebrate
Diversity in Nervous Systems
Figure 48.1 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
The main roles of the parasympathetic and
sympathetic nerves in regulating internal
body functions
Structure of a Vertebrate Neuron
Structural Diversity of Neurons
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
Schwann Cells
Synaptic
Transmission
• An AP reaches the
axon terminal of the
presynaptic cell and
causes V-gated Ca2+
channels to open.
• Ca2+ rushes in, binds
to regulatory proteins
& 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.
A Chemical Synapse
The Major Known Neurotransmitters
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
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
Propagation of the Action Potential
Graded potentials and the action potential in
a neuron
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.
The two hemispheres of the brain
are connected by the:
What was the substrate in
yesterday’s lab? What was the
product?
Last Review Questions for the Week:
What are the two components of the
CNS?
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?
What is the purpose of the myelin
sheath?
What is the minimum level of a
stimulus required to activate a
neuron called?
What is meant by the term, “all-ornone principle” with regards to the
conduction of nerve impulses?