Chapter 8 Flashcards
What occurs during enhanced transmission at the presynaptic neuron?
Enhanced depolarization in the postsynaptic neuron.
Mechanisms include facilitation, augmentation, and post-tetanic potentiation.
What is facilitation?
A slight increase in depolarization occurs for the next few milliseconds after rapid stimuli.
Mechanism involves Ca2+ that entered through voltage-gated calcium channels.
What is augmentation?
Multiple stimuli with short interstimulus intervals lead to greater degrees of enhancement compared to facilitation.
Lasts for seconds (5-10) and involves elevated Ca2+ altering munc13.
What is post-tetanic potentiation (PTP)?
Rapid stimuli lasting 10-20 seconds that result in increased Ca2+ activating PKC, modifying proteins in vesicle release.
Lasts for minutes.
What occurs during depressed transmission?
Reduced depolarization in the postsynaptic neuron due to sustained stimulation.
Mechanism is hypothesized to involve reduced vesicles available.
What is habituation in Aplysia?
Repeatedly touching the siphon leads to less responsiveness to stimuli, causing the gill to cease contracting.
Sensory neuron releases less glutamate.
What is sensitization in Aplysia?
Touching the siphon and giving a noxious stimulus to the tail causes the gill to contract again.
Involves serotonin release onto metabotropic receptors.
What is short-term sensitization?
A single tail shock leads to a heightened response lasting around 1 hour.
Serotonin binds to Gs-coupled receptors, activating PKA.
What is long-term sensitization?
Multiple tail shocks lead to a heightened response lasting days.
Involves CREB activation and synthesis of proteins that promote new synapses.
What is long-term potentiation (LTP) in the hippocampus?
Changes occur in the postsynaptic neuron without recruiting additional neurons.
Mechanism also observed in cerebral cortex, amygdala, cerebellum, and some inhibitory synapses.
What is the role of NMDA receptors in LTP?
NMDAR allows Ca2+ influx if both pre- and postsynaptic neurons are active.
Hebb’s principle: ‘fire together, wire together’.
What characterizes the early phase of LTP?
Lasts several hours and is not dependent on protein synthesis.
Mechanism involves phosphorylation of AMPA stored receptors.
What characterizes the late phase of LTP?
Lasts for years and is dependent on protein synthesis.
Mechanisms include activation of CREB leading to synaptic growth.
What is long-term depression (LTD) in the hippocampus?
Occurs with very low frequency stimulation for an extended time, leading to depressed EPSPs.
Mechanism involves low levels of calcium activating phosphatases.
What is spike timing dependent plasticity?
Depression or potentiation can occur in response to synaptic input based on timing relative to action potentials.
If postsynaptic cell fires AP before EPSP, response is depressed; if after, response is potentiated.
