SYNAPSES - NEUR200

charles scott sherrington

nobel prize 1932

introduced the term synapse

action potentials along sensory or motor neurons are about

40 m/s

the speed fo conduction through the reflex arc is never more than

15 m/s

synaptic delay occurs where

one neuron communicates with another

graded potential

may be either depolarization (excitatory) or hyperpolarizations (inhibitory)

excitatory postsynaptic potential (EPSP)

• temporary graded depolarization of the postsynaptic membrane

  • caused by the entrance of sodium ions into the cell

  • makes the cell more likely to fire an AP

inhibitory postsynaptic potential (IPSP)

• temporary graded hyperpolarization of postsynaptic membrane

  • caused ny the exit of potassium ions outside the cell or chloride ions (negative charges) inside

    • increases the negative charge within the neuron

  • this will make the cell less likely to fire an action potential

• GABA

depolarization of the membrane DOES/DOESN’T always lead to an action potential

DOESN’T

spatial summation

• synaptic inputs from separate locations combine their effects on a neyron

  • summation over space

repeated stimuli within a brief time have a _____

cumulative effect

temporal summation

• even though the signal in the postsynaptic neuron decays over time, it can combine with a second excitation

  • when the combination exceeds the threshold → AP

can temporal and spatial summation occur together?

yes

spontaneous firing rate

• a periodic production of action potentials even without synaptic input

  • ongoing activity in the absence of a task or stimulation

    • ongoing brain activity may be important for perception

  • EPSPs increase above

  • IPSPs decrease

EPSPs ____ the frequency of APs above the spontaneous rate, whereas the IPSPs ____ it

increase, decrease

neural synchronization

• brain waves from different regions will synchronize (network communication)

• synchronized activity of neurons can give rise to oscillations