How Neurons Generate Signals - PowerPoint PPT Presentation

1 / 9
About This Presentation
Title:

How Neurons Generate Signals

Description:

Nernst equation calculates the equilibrium potential for a single ion, given ... Goldman equation calculates the resting potential of a neuron, given knowledge ... – PowerPoint PPT presentation

Number of Views:25
Avg rating:3.0/5.0
Slides: 10
Provided by: NAlva6
Category:

less

Transcript and Presenter's Notes

Title: How Neurons Generate Signals


1
How Neurons Generate Signals
  • The Neuron at Rest

2
Stepping on a Thumbtack
  • Reflexive withdrawal of the foot a simple
    behavior controlled by a circuit with direct
    connections between
  • Sensory neurons (responding to environment)
  • Motor neurons (controlling muscles)
  • Interneurons (to inhibit opposing muscles)
  • Projection neurons (carrying sensation to the
    brain)
  • Messages are carried via action potentials.

3
Biochemical Reactions
  • Ion an electrically charged atom.
  • Polar covalent bonds a molecule held together
    by sharing electrons (H2O).
  • Ionic bond a molecule held together by the
    attraction of atoms with opposite charges (NaCl
    table salt).
  • Cation ion with a net positive charge.
  • Anion ion with a net negative charge.

4
The Neuron at Rest
  • Neurons have potassium (K) inside and sodium
    (Na) outside in the extracellular fluid.
  • Ion channels in the cell wall (membrane) are
    selectively permeable to potassium, sodium or
    calcium.
  • Ion pumps maintain the cells inner environment.

5
How Ions Cross the Membrane
  • Diffusion an ionic concentration gradient
    exists
  • Differences in electrical membrane potential and
    equilibrium potential
  • Ionic driving force
  • Ion pumps
  • Sodium/potassium, calcium

6
Electricity
  • Opposite charges attract, like charges repel.
  • Current (I) movement of electrical charge,
    measured in amps.
  • Potential (voltage, V) force exerted on a
    particle, difference between terminals, measured
    in volts.
  • Conductance (g) relative ability of a charge to
    migrate, measured in Siemens.

7
Resting Potential
  • Membrane potential is voltage across the neuronal
    membrane.
  • Resting potential is the point at which all of
    the forces acting upon ions are in balance
    (equilibrium).
  • Diffusional and electrical forces are equal.
  • Vm -65 mV

8
Two Important Equations
  • Nernst equation calculates the equilibrium
    potential for a single ion, given knowledge of
    its concentration inside outside the neuron.
  • Varies with body temperature.
  • Goldman equation calculates the resting
    potential of a neuron, given knowledge of its
    permeability to various ions.
  • Varies with ion concentrations.

9
Regulation of Potassium
  • The neuron at rest is mostly permeable to
    potassium (K) so the resting potential is close
    to EK.
  • Increasing potassium outside the cell leads to
    depolarization (an increase in the resting
    potential making it less negative).
  • To prevent this, potassium is tightly regulated
    by the body via glia blood-brain barrier.
Write a Comment
User Comments (0)
About PowerShow.com