last updated:

Feb 20, 2021


[Brain Image]    

PSY 340 Brain and Behavior

Class 07: The Concept of the Synapse & Chemical Events at the Synapse (pt. 1)  OUTLINE


[Types of Transmission]

The Puzzle of How Neurons Are Connected

Ramon y Cajal

                  as connected

Sir Charles Scott Sherrington (1857-1952) & the Discovery of the Synapse

Reflexes: automatic muscle responses to stimuli

  • Sensory neuron --> interneuron ("intrinsic") neuron --> motor neuron at level of the spinal cord = reflex arc

[Reflex Arc Leg Flexion]

  • reflexes are slower than simple conduction along an axon would suggest.
  • weak stimuli presented at different times or in different locations elicit a stronger response than a single strong stimulus does.
  • excitation of one muscle set leads to relaxation in its opposing muscle set.   

Speed of Reflex & Delayed Transmission at the Synapse

[Gaps in neural signal]

Summation: The effects of different kinds of stimulation on a neuron's tendency to fire

Two types: temporal and spatial

[Summation Diagram]

Temporal summation: multiple firings at the same time

Spatial summation: multiple firings in different places

EPSPs and IPSPs: Effects at the Synapse

[EPSPs and IPSPs]

 Chemical Events at the Synapse (pt. 1)

Otto Loewi (1873-1961) & Chemical Transmission at Synapses (1920)

[Otto Loewi] adrenaline (epinephrine) causes the heart to beat faster, relaxes the stomach muscles, dilates the pupils.
sympathetic nervous system (SNS)
Otto Loewi in 1920
Stimulated the vagus nerve
Vagusstoff which was actually....Acetylcholine (ACh)


Chemical Activity at the Synapse

              Activity at the Synapse


This page was first posted January 30, 2005