Chapter 3 Synapses. Synapse : gap between one neuron’s presynaptic terminal and another receiving neuron Discovered by Santiago Ramon y Cajal in the late 1800s. The Concept of the Synapse. In 1906, Charles Scott Sherrington:
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Discovered by Santiago Ramon y Cajal in the late 1800sThe Concept of the Synapse
Fig. 3-1, p. 52
2. Several weak stimuli presented at slightly different times or slightly different locations produces a stronger reflex than a single stimulus does.
3. As one set of muscles relaxes, another set becomes excited.
Temporal summation: repeated stimuli can have a cumulative effect and can produce a nerve impulse when a single stimuli is too weak.
Fig. 3-4, p. 54
is a graded (excitatory) potential that decays over time and space.
The cumulative effect of EPSPs are the basis for temporal and spatial summation.
Inhibitory postsynaptic potential (IPSP): hyperpolarizes membrane.
Serves as an active “brake”, that suppresses excitation.The Concept of the Synapse
Axon membrane (A)
Presynaptic membrane (A1)
Synaptic vesicles (B): tiny spherical packets located in the presynaptic terminal where neurotransmitters are held for release
Neurotransmitters (C): chemicals that travel across the synapse and allow communication between neurons
Neurotransmitter fragments (C1)Neuroanatomy Handout #2: The Synapse and Neurotransmitters
Neurons store neurotransmitters in axon terminals or transport them there (transportation from cell body can take hours or days).
An action potential triggers the release of neurotransmitters into the synaptic cleft.Major sequence of events for neurotransmitters:
The neurotransmitters separate from the receptors.
The neurotransmitters are taken back into the presynaptic neuron, diffuse away, or are inactivated by chemicals.Major sequence of events for neurotransmitters:
Endocrine glands are responsible for the production of hormones.
Hormones are important for triggering long-lasting changes in multiple parts of the body.Chemical Events at the Synapse
Anterior pituitary- composed of glandular tissue and synthesizes six hormones.
Posterior pituitary- composed of neural tissue and can be considered an extension of the hypothalamusPituitary Gland
small subcortical area rich in dopamine receptors
anarea responsible for feelings of pleasureDrugs and the Synapse