A and P 181 191
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Transcript of A and P 181 191
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Module#7 The Nervous System
Functions:CommunicationCoordinationControlGathering information
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Differences between human and animal NS:1. Language2. Judgment3. Problem solving4. Creativeness5. Passing along
heritage
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Two Divisions of the NS
1.Central nervous system (CNS)
•the brain and spinal cord
•is encased in bone (skull and vertebral column)
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Central Nervous System
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Two Divisions of the NS
2. Peripheral nervous system (PNS)
•nerves and ganglia that branch from the CNS and go to body.
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Peripheral Nervous System
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Nerves – bundles of axons and their sheaths which extend from the CNS
Ganglia – collections of neuron cell bodies which are outside of the CNS
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CNS1. Brain •protected by cranium•high level thought•major organ of the NS•Message center•Uses info to formulate ideas•Makes decisions•Communicates with body
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CNS1. Brain
2. Spinal CordThick bundle nerve fibers
within spinal cavityHow brain communicates
with most of bodyEnds at first lumbar
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Peripheral NS
1. Cranial nervesNerves that come from brain12 pairsBranch from brain stemTransmit from/to eyes, ears,
mouth, face and scalp
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Peripheral NS
1. Cranial nerves
2. Spinal NervesNerves that come from spinal
cord31 pairsTransmit signals to and from the
rest of the body
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Spinal nerves
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Two divisions of Peripheral NS:1. Afferent sensory pathways - involves the sensory organs like eyes, ears..Neurons carry action potential from sense organs to CNSAlso called sensory division
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Two divisions of Peripheral NS:
1. Afferent
2. Efferent
Motor pathways - system that innervates muscles, effector organs, and glands.Also called motor division
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Action potential – electrical signal that
travels along a neuron.
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Divisions of the Efferent Nervous System:1. Somatic Motor Nervous
System (SMNS)
transmits action potential from CNS to skeletal muscles
conscious, voluntary control
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Divisions of the Efferent Nervous System:1. Somatic Motor Nervous System (SMNS)
2. Autonomic NS carries stimulus from the CNS to the smooth muscles, cardiac muscles, and glandsInvoluntary, unconscious control
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Divisions of the autonomic system:1. Sympathetic system
•prepares body for physical activity•increases heart rate, blood pressure, blood glucose levels•Prepares for “flight or fight”
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Divisions of the autonomic system:
1. Sympathetic system
2. Parasympathetic:Regulates resting and nutritionally related functionsIncludes digestion, urination, defecationSlows down heart, etc. after “Fight or Flight” response
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NS at a Cellular level:
2 types of cells:1. Neurons = functioning cell
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Three parts of neurons (nerve cells):
A. cell body contains the nucleus of cell
B. dendrites – short, branched extensions of cell body receive nerve impulses and conduct them toward the cell body
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Three parts of neurons (nerve cells):
A. cell body B. dendrites
C. axon one long extension which carries impulses away from cell body to other cellshillock where the cell body ends and axon begins
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Axon continued:
Is wrapped in a substance called myelin produced by neuroglial cellsmyelin speeds up impulsed
Myelin is called Schwann in PNSand oligodendrocyte in CNS
Gaps in myelin called nodes of Ranvier
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Axon continued :
Axons vary in length
Axon splits into collateral axons and then end in presynaptic terminals
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Collateral Axons
Nerve impulses travel from the dendrite to body to axon.
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Mature neurons can not undergo mitosis.
They are parenchyma permanent cells!!
TAKE CARE of them!!
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But, Mrs. Crawford how can I take care of them?
Get plenty of sleep, avoid lots of TV, avoid caffeine, alcohol, drugs, and smoking!
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Well, how many neurons do I have?
It is believed you have around 100 billion, some will die just due to natural causes (about 7,000/day)
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NS at a Cellular level continued
Can classify neurons based on their structure - how many
processes they have (dendrites and axons):
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1.Unipolar –one process with a cell body that hangs off to the side
2.Bipolar – two processes an axon and a single dendrite with the cell body in middle
3. Multipolar –only one axon with many dentrites.
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unipolar
Bipolar
multipolar
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NS at a Cellular level continued
oWhat in the world is a association neuron Mrs. Crawford?
A neuron that conducts action potentials for one
neuron to another. (interneurons)
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NS at a Cellular level:2 types of cells:
1. Neurons = functioning cell
2. NeurogliaBinds, protects and insulates neuronsIs the majority of cells in the NS.They do carry on mitosis!!
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Types of Neuroglia :
1.Schwann cells – insulate axons of PNS
2. Oligodendrocytes – insulate axons of CNS3. Microglia – white blood cells of brain
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Types of Neuroglia :
4. Astrocytes – form blood-brain barrier regulating what can enter the brain and what cannot. (Some toxins pass through such as alcohol toxins)
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Types of Neuroglia :
5. Ependymal cells – two typesa. non – ciliated – secrete
cerebrospinal fluidb. ciliated – move cerebrospinal
fluid around
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Wrappings of the Nerve:Epineurium – wraps the nerve – white, shinyPerineurium – wraps the fasciclesEndoneurium – wraps the Schwann cells of axonsFascicles are bundles of axons
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eb47dc914c9e8ff7b6da26a6ba718099.avi
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Nerve anatomy:
Run along with veins and arteriesMedium sized = shoe stringSciatic nerve – largest, thickness of index finger
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3 Types of Nerves:
1. Sensory – carries sensory messages only (optic nerve)
2. Motor – carries messages to the muscles (eye muscles)
3. Mixed – carries both sensory and motor messages (most nerves)
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Healing in Nervous System:
•Neurons cannot undergo mitosis.
•Nerve healing occurs under certain conditions.
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Conditions of nerve healing:•Axon is wrapped in Schwann cells which means only in PNS
•Axon ends are close and pointed in right direction
• Cell body remains intact
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Conditions of nerve healing
No healing in CNS, spinal cord or brain
Can be surgically aided
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Why are Schwann cells able to aide in healing and oligodendrocytes not?
There are many Schwann cells per axon in PNS, but many axons per oligodendrocyte in the CNS.