Nervous system
Transcript of Nervous system
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The Nervous System
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Facts:Facts:
Responsible for all behavior Every thought, action, and behavior controlled here Works together with the endocrine system to achieve
homeostasis Cells communicate by electrical signals
Responsible for all behavior Every thought, action, and behavior controlled here Works together with the endocrine system to achieve
homeostasis Cells communicate by electrical signals
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Three Main Functions:Three Main Functions:
Sensory input Integration Motor output
Sensory input Integration Motor output
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Sensory InputSensory Input
Our bodies have millions of sensory receptors
They detect changes Changes are called “stimulus” This is where all stimuli is collected Called the “afferent pathway”
Our bodies have millions of sensory receptors
They detect changes Changes are called “stimulus” This is where all stimuli is collected Called the “afferent pathway”
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IntegrationIntegration
Your brain makes decisions about what to do with the stimulus
It processes the info gathered It establishes a set point
Your brain makes decisions about what to do with the stimulus
It processes the info gathered It establishes a set point
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Motor OutputMotor Output
Causes a response to the stimulus Activates effector organs Sends signal down “efferent pathway”
Causes a response to the stimulus Activates effector organs Sends signal down “efferent pathway”
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Nervous System DivisionsNervous System Divisions
Central Nervous System (CNS) CNS includes brain & spinal cord Peripheral Nervous System (PNS)’ PNS broken down into afferent & efferent divisions Sensory division = Afferent division Motor division = efferent division Both CNS and PNS work together You can’t have one without the other
Central Nervous System (CNS) CNS includes brain & spinal cord Peripheral Nervous System (PNS)’ PNS broken down into afferent & efferent divisions Sensory division = Afferent division Motor division = efferent division Both CNS and PNS work together You can’t have one without the other
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Nervous System HistologyNervous System Histology
Nervous tissue is highly cellular Less than 20% of cns is extra-cellular space Cells densely packed together Tissue is made up of two principal types of cells (nerve
cells and supporting cells)
Nervous tissue is highly cellular Less than 20% of cns is extra-cellular space Cells densely packed together Tissue is made up of two principal types of cells (nerve
cells and supporting cells)
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Supporting Cells in CNSSupporting Cells in CNS
Glial cells (neuroglia) Glial cells have branching processes and central cell
body, like neurons Smaller than neurons Outnumber neurons in CNS 9 to 1 They make up half the mass of the brain
Glial cells (neuroglia) Glial cells have branching processes and central cell
body, like neurons Smaller than neurons Outnumber neurons in CNS 9 to 1 They make up half the mass of the brain
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Common Glial Cells in CNSCommon Glial Cells in CNS
Astrocytes Control chemical enironment around neurons “mop up” leaked potassium ions & recycle them Recapture/recycle neurotransmitters
Microglia Monitor health of neurons Protect against microorganisms Can turn into macrophages which destroy foreign intruders Fact: immune system cells are denied access to CNS
Oligodendrocytes Make up myelin sheaths
Astrocytes Control chemical enironment around neurons “mop up” leaked potassium ions & recycle them Recapture/recycle neurotransmitters
Microglia Monitor health of neurons Protect against microorganisms Can turn into macrophages which destroy foreign intruders Fact: immune system cells are denied access to CNS
Oligodendrocytes Make up myelin sheaths
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Supporting Cells in PNSSupporting Cells in PNS
Satellite Cells Surround neuron cell bodies Play a role in controlling the chemical environment of
the neurons
Schwann Cells Surrounds & forms myelin sheaths around larger nerve
fibers in PNS Functionally similar to oligodendrocytes
Satellite Cells Surround neuron cell bodies Play a role in controlling the chemical environment of
the neurons
Schwann Cells Surrounds & forms myelin sheaths around larger nerve
fibers in PNS Functionally similar to oligodendrocytes
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NeuronsNeurons
Structural units of the nervous system Highly specialized cells Have extreme longevity with good nutrition (100 years
plus) Neurons are amitotic - no ability for mitosis. Cannot be
replaced if destroyed Have a high metabolic rate - need high amounts of
oxygen & glucose. Cannot survive more than a few minutes without
oxygen
Structural units of the nervous system Highly specialized cells Have extreme longevity with good nutrition (100 years
plus) Neurons are amitotic - no ability for mitosis. Cannot be
replaced if destroyed Have a high metabolic rate - need high amounts of
oxygen & glucose. Cannot survive more than a few minutes without
oxygen
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Neuron AnatomyNeuron Anatomy
The most common neuron is multipolar They are made up of four basic parts: Dendrites - receive signals from previous neurons Cell body - controls/sustains neuron Axon - allows nerve signals to travel along neuron Terminal bodies - release neurotransmitters at tips Myelin sheaths cover axon in many neurons. Protects,
insulates, and speeds up conduction. Myelinated neurons include “nodes of Ranvier” Function … speeds up signal transmission Myelinated neurons faster conductors than
unmyelinated
The most common neuron is multipolar They are made up of four basic parts: Dendrites - receive signals from previous neurons Cell body - controls/sustains neuron Axon - allows nerve signals to travel along neuron Terminal bodies - release neurotransmitters at tips Myelin sheaths cover axon in many neurons. Protects,
insulates, and speeds up conduction. Myelinated neurons include “nodes of Ranvier” Function … speeds up signal transmission Myelinated neurons faster conductors than
unmyelinated
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Multipolar NeuronMultipolar Neuron
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Drugs & NeurotransmittersDrugs & Neurotransmitters
Inside of hypothalamus is our “pleasure center”
Motivates much of human behavior Responsible for anything that gives us
pleasure/joy Our ability to feel good involves
neurotransmitters Drug use re-programs how these
neurotransmitters work
Inside of hypothalamus is our “pleasure center”
Motivates much of human behavior Responsible for anything that gives us
pleasure/joy Our ability to feel good involves
neurotransmitters Drug use re-programs how these
neurotransmitters work
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Speed (Methamphetamine)Speed (Methamphetamine)
Artificially stimulates brain to provide pleasure flush
When outside chemicals are introduced, brain produces less neurotransmitters
“why bother?!?!?”
Artificially stimulates brain to provide pleasure flush
When outside chemicals are introduced, brain produces less neurotransmitters
“why bother?!?!?”
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CocaineCocaine
Comes in snorted form (white powder) Stimulates pleasure center then squeezes it
dry Hooks to dopamine transporter protein So, it blocks reabsorption of dopamine …..the neurotransmitter remains in synapse
and stimulates receptor cells over and over again
Increased heart rate, blood pressure, sexual appetite
Comes in snorted form (white powder) Stimulates pleasure center then squeezes it
dry Hooks to dopamine transporter protein So, it blocks reabsorption of dopamine …..the neurotransmitter remains in synapse
and stimulates receptor cells over and over again
Increased heart rate, blood pressure, sexual appetite
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As dopamine is blocked, it accumulates in synapse It’s washed away Brain dopamine supply becomes inadequate to maintain
normal moods The sending cells cannot make dopamine fast enough to
make up for the loss and pleasure circuits go dry Cannot experience pleasure without the drug Catch-22: cocaine needed to experience pleasure, but
more use = more depletion of neurotransmitter supply Weight loss, trouble sleeping, mood swings, death Incredibly difficult to treat
As dopamine is blocked, it accumulates in synapse It’s washed away Brain dopamine supply becomes inadequate to maintain
normal moods The sending cells cannot make dopamine fast enough to
make up for the loss and pleasure circuits go dry Cannot experience pleasure without the drug Catch-22: cocaine needed to experience pleasure, but
more use = more depletion of neurotransmitter supply Weight loss, trouble sleeping, mood swings, death Incredibly difficult to treat
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CrackCrack
Cheaper than cocaine More potent Smokable form of cocaine Produces higher high and a deeper
crash!! Intensely addictive
Cheaper than cocaine More potent Smokable form of cocaine Produces higher high and a deeper
crash!! Intensely addictive
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HeroinHeroin
Is a depressant Far more expensive than cocaine Demands higher doses to achieve the same
effect When addicted and going without, body goes
into incapacitated nausea and convulsions With an overdose, lungs fill with fluid and user
drowns.
Is a depressant Far more expensive than cocaine Demands higher doses to achieve the same
effect When addicted and going without, body goes
into incapacitated nausea and convulsions With an overdose, lungs fill with fluid and user
drowns.