Nervous system
Upcoming SlideShare
Loading in...5

Nervous system






Total Views
Views on SlideShare
Embed Views



0 Embeds 0

No embeds



Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
Post Comment
Edit your comment

    Nervous system Nervous system Presentation Transcript

    • The Nervous System
    • 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
    • Three Main Functions:
      • Sensory input
      • Integration
      • Motor output
    • Sensory 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”
    • Integration
      • Your brain makes decisions about what to do with the stimulus
      • It processes the info gathered
      • It establishes a set point
    • Motor Output
      • Causes a response to the stimulus
      • Activates effector organs
      • Sends signal down “efferent pathway”
    • Nervous 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
    • Nervous 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)
    • Supporting 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
    • Common 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
    • Supporting 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
    • Neurons
      • 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
    • Neuron 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
    • Multipolar Neuron
    • Drugs & 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
    • Speed (Methamphetamine)
      • Artificially stimulates brain to provide pleasure flush
      • When outside chemicals are introduced, brain produces less neurotransmitters
      • “ why bother?!?!?”
    • Cocaine
      • 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
      • 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
    • Crack
      • Cheaper than cocaine
      • More potent
      • Smokable form of cocaine
      • Produces higher high and a deeper crash!!
      • Intensely addictive
    • Heroin
      • 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.