Structure of a Synapses
Synapse: Is a junction
where a axon interacts with
another neuron
Presynaptic Terminal: End
of the axon
Postsynaptic Membrane:
Membrane of the dendrite
Synaptic Cleft: Space
between the presynaptic
membrane and postsynaptic
membrane
Synaptic vesicles: Stores
chemical neurotransmitters
 Excitatory - increase membrane permeability,
increases chance for threshold to be achieved to trigger
an action potential
 Inhibitory - decrease membrane permeability,
decrease chance for threshold to be achieved to trigger
an action potential
 Acetylcholine ACh - stimulates muscle contraction
 Norepinephrine & Dopamine (sense of feeling
good, low levels = probable cause to depression)
 Serotonin (sleepiness)
 Endorphins (reduce pain, inhibit receptors)
 Reflex: An involuntary reaction in response to a
stimulus
 Reflex Arch: Pathway in which a reflex occurs.
 Sensory Nerves - conduct impulses into the brain or
spinal cord
 Motor Nerves - carry impulses to muscles of glands
from the brain and spinal cord
 Mixed Nerves - contain both sensory and motor
nerves
 5 steps of Reflex Arch
1.
2.
3.
4.
5.
Sensory Receptor
Afferent neuron
interneuron
Motor neuron
Effector organ
 Reflex arc - only includes a few neurons
 Reflex Behavior – automatic and subconscious
responses
 Stretch or Knee-jerk reflex – Muscles contract when
applied force it put on them (patellar reflex)
 Withdrawal reflex - avoidance of painful stimuli
 Converging Pathways: More than one neuron
synapses converge on the same neuron. (more than
one neuronal pathway)
 Diverging Pathways: The axon from one neuron
divides or diverges with one or more neurons. (one
neuronal pathways can diverge into multiple
pathways)