The Nervous System. The Haitian Zombie .
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Transcript of The Nervous System. The Haitian Zombie .
The Nervous System
The Haitian Zombie
http://www.youtube.com/watch?v=cXcjioLLvRQ
The Function of the Nervous System
Major control and communication system of the body
What other body systems communicate with the nervous system?
• Works with the muscular system
• Works with the endocrine system
•Works with the circulatory system
•Works with the integumentary system
•Works with the digestive system
There’s more…
Urinary systemSkeletal systemRespiratory systemReproductive systemImmune system
Functions of the Nervous SystemSensory Input
◦Gathering information by sensing stimuli
Integration◦Processes and interprets that
information
Motor Output◦Response to the stimulus◦May activate muscles or glands
Organization of the Nervous SystemCentral Nervous System
◦Brain◦Spinal Cord
Peripheral Nervous System◦Nerves that connect the brain and
spinal cord to the rest of the body
Breakdown of the PNSSensory Division
◦AKA: Afferent Division◦Carry information to the CNS
Motor Division◦AKA: Efferent Division◦Carry impulses away from the CNS
Breakdown of the Motor (efferent) Division of the PNSSomatic Nervous System
◦Voluntary◦Skeletal muslces
Autonomic Nervous System◦Involuntary◦Cardiac & smooth muscles; glands;
hormones
Breakdown of the Autonomic Nervous System
Sympathetic Division ◦Fight or Flight
Parasympathetic Division◦Rest and Digest
DRAW IT OUT!
Let’s make a flow chart to organize the complicated nervous system.
The Cells of the Nervous SystemsSupporting cells called neuroglia
◦Support, insulate, & protect neurons ◦CNS & PNS have different “glia” or
supporting cells◦CANNOT transmit nerve impulses
Nerve cells called neurons◦Same for the CNS and PNS
Neuroglia of the CNSAstrocytes
◦ Form a barrier between neurons and the blood capillaries
◦ Brace the neurons to the blood supply
◦ Control the chemical environment of the brain
Microglia◦ Spiderlike
phagocytes◦ Dispose of
bacteria, dead cells, and other debris
Neuroglia of the CNSEpendymal cells
◦ Ciliated cells◦ Line the cavities
of the brain and spinal cord
◦ Circulate the cerebrospinal fluid
Oligodendrocytes◦ Wrap their
extensions tightly around nerve fibers
◦ Form insulation around neurons called myelin sheaths
Neuroglia of the PNSSatellite Cells
◦ Protect the neuron cell bodies
◦ Provide cushion
Schwann Cells◦ Form insulation
around the neurons (myelin sheaths)
◦ Increases the speed of nerve impulses!
Neurons = Nerve CellsHighly specialized cells that
transmit messages in the form of electrical impulses
Every neuron has:1. Cell Body2. Dendrites3. Axon
NeuronsCell Body
◦ Metabolic center of the cell
◦ Contains cell organelles, except centrioles
◦ Neurofibrils (cellular filaments) and the rough endoplasmic reticulum called Nissl Substance give the cell its shape
Processes (Extensions)◦ Dendrites
Can have hundreds of branching dendrites
◦ Axons Only ONE axon
protruding from the cell body,
BUT axon can branch Can have many axon
terminals
NeuronDendrites
◦ Conduct impulses toward the cell body
Axon◦ Conduct impulses
away from the cell body
◦ Axon terminals contain hundreds of tiny vesicles containing neurotransmitters
SynapseJunction where the axon terminal
of the PRESYNAPTIC neuron meets the dendrites of the POSTSYNAPTIC neuron
The two neurons don’t actually touch◦Synaptic Cleft- gap between
adjacent neurons
Schwann CellsEnvelopes and rotates around an axonMost of the cell cytoplasm is toward the
outside of the cell◦ Neurilemma
Tight coil of plasma membrane closest to the axon◦ Myelin Sheath
Nodes of Ranvier◦ Gaps in the myelin
sheath along the
axon
Neuron Cell Body LocationMost are found in the CNS
◦Nuclei- clusters of cell bodies in the CNS
◦Tracts- bundles of nerve fibers running through the CNS
Ganglia- collections of cell bodies in the PNS◦Nerves- bundles of nerve fibers
running through the PNS
Neuron ClassificationSensory Neurons
◦Carry impulses from sensory receptors TO the CNS
◦AKA Afferent Neurons◦Cell body is found in ganglion outside
the CNS◦What are Sensory Receptors?
Found in cutaneous sense organs Sense touch, pressure, pain, temperature
Proprioceptors detect stretch or tension in skeletal muscles, their tendons, and joints
Neuron ClassificationMotor Neuron
◦Carries impulses from the CNS to the body
◦AKA Efferent Neuron◦Cell body of the neuron is found in
the CNS
Neuron ClassificationInterneurons or Association
Neurons◦Small neuron that is always located
in the CNS whose job is to connect the sensory and motor neurons to complete the pathway
Structural Classification of NeuronsBased on the number of
processes extending from the cell body of the neuron
3 Types:◦Multipolar neuron- many extensions
from the cell body◦Bipolar neuron- one axon and one
dedrite◦Unipolar neuron- one short single
process leaving the cell body
Structural Classification of Neurons
What do neurons do?Irritability- ability
to respond to a stimuli and convert it into a nerve impulse
Conductivity- ability to transmit an impulse to other neurons, muscles, or glands
Nerve Impulse Videohttp://highered.mcgraw-hill.com/s
ites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
Nerve ImpulseMembrane of a
resting (inactive) neuron is polarized◦ Fewer positive
ions inside the cell than outside
◦ Major + ions that are in the cell are K+
◦ Major + ions outside the cell are Na+
Voltmeter = -70 mV
Nerve ImpulseWhen stimuli (light,
sound, touch, or neurotransmitters released from another neuron) excite a neuron, sodium channels open in the membrane allowing an inward rush of Na+
Depolarization- change in polarity of the membrane◦ Locally, the inside is more
+ and the outside is less + All or none response: Only if
the stimulus is strong enough and the Na+ influx is great enough, will the neuron transmit an impulse (message)
Nerve Impulse If signal is strong enough,
an action potential (nerve impulse) is generated
Action potential propagates over the entire axon
K+ ions rush out of the neuron after Na+ rush in, repolarizing the membrane◦ Restores electrical conditions
to the resting state (more - on the inside)
Sodium-Potassium pump then restore the neuron to the initial concentrations of Na+ and K+
5 Step Nerve Impulse1. Resting membrane potential is more – inside
the cell than outside with more K+ inside the cell and more Na+ outside the cell
2. Stimulus opens Na+ channels, allowing influx of Na+ in cell initiating local depolarization
3. Generates action potential which travels down the axon
4. Repolarization by K+ channels allowing K+ to leave the cell, making the inside of the cell more - than the outside
5. Na+/K+ pump restores ion concentrations to more K+ in cell and more Na+ outside of the cell
Nerve Impulse
What happens when the action potential reaches the axon terminals?
Ca2+ ions rush into the axon terminal of the presynaptic neuron, causing tiny vesicles containing neurotransmitters to be released into the synaptic cleft
Neurotransmitters then bind to the receptors on the dendrites of the postsynaptic neuron
If enough neurotransmitters bind to the dendrites, an action potential will result
Electrochemical Event
ACT IT OUT!http://highered.mcgraw-hill.com/s
ites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html
Represent the membrane, Na+ and K+ ions, Na+ and K+ channels, Na/K pump
Why doesn’t the sodium channel let K ions pass through?Sodium Channel
◦ Negatively charged amino acids block anions from passing through
◦ Na+ is smaller than K+
◦ Only allows 1Na+ and 1 H20 molecule to pass at a time; K+ is too large
Potassium Channel◦ Negatively charged
amino acids block anions from passing through
◦ K+ is larger than Na+
◦ K channel is deeper and wider
◦ Na+ is too small and not electronegative enough to activate the channel
How does myelin sheath increase the speed of a nerve impulse?
Saltutory conduction
http://www.youtube.com/watch?v=mOgHC5G8LuI
Multiple Sclerosis (MS)Antibodies
specific for protein in myelin sheath
Damaged myelin forms scar tissue forming hard plaque or sclerosis
Neurons are short-circuited and damaged
Myelin Repair
Sodium Channel BlockersIf you block a
sodium channel and the sodium cannot get into the neuron cell… what will happen?
Does not allow neurons to transmit nerve impulses
Paralysis due to loss of nerve function
TTX (tetrodotoxin)Anesthetics Treat cardiac
arythmiasAnti-epileptic drugs
NeurotoxinsTTX (tetrodotoxin)Too large to pass through the
blood brain barrier so often does not affect mental function
Binds to Na+ channels, preventing Na+ from generating an action potential
Paralysis, slowed heart rate, slowed respiration
Potassium Channel BlockersProlong
depolarizationUse for heart
problems