Nervous Tissue Pt. 2
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Postsynaptic Cell Responses:
- 1) Open/close membrane ion channels
- - depolarization
- - hyperpolarization
- 2) Variety of intracellular responses
- - Result depends on type of NT and the receptor type for each NT
- types? describe.
- 1. Graded potentials
- 2. EPSP = excitatory postsynpatic potential
- - opens Na+ and K+ chemical-gated channels simultaneously
- - Na+ influx> K+ efflux
- - Depolarization (closer to threshold)
- 3. IPSP= inhibitory postsynaptic potential
- - NT binding causes hyperpolarization
- - Opens K+ and/or Cl- chemical-gated channels
- -K+ efflux and/ or Cl- influx
- - Hyperpolarization- farther away from threshold.
- 2 methods, describe
- #1. Spatial summation 9 uses multiple neurons to cause a larger effect on the postsynaptic neuron)
- --> simultaneous graded potentials to enhance initiation of a potential at trigger zone.
- #2. Temporal Summation (over time you increase the frequency of stimulation)
- --> Graded potentials arrive at trigger zone very close together
Types of Summation: Processes
* postsynaptic neuron (at axon hillock) - integrator of excitatory inhibitory signals:
- - Excitatory >Inhibitory, but < Threshold = Facilitation
- - Excitatory> inhibitory, and Threshold = AP
- - Inhibitory> Excitatory= Inhibition
- -NT release froma axon terminals of presynaptic neuron is inhibited or stimulated
- - Change in postsynaptic membrane response
Synaptic Integration (5)
- - Different Patters of interactions between enurons
- 1. Divergence
- (EX) sensory info is distributed to various parts of the brain at the same time.
- 2. Convergence
- (EX) Multiple parts of the brain control the function of one neuron
- 3. Serial processing
- (EX) sensory info is relayed from one part of the brain to another in sequence.
- 4. Parallel processing
- (EX) Simultaneous processing; multiple responses at the same time
- 5. Reverberation
- (EX) positive feedback that continues until synaptic fatigue occurs or something breaks the cycle.
- 1. Uptake into presynaptic cell (or adjacent neuron or glial cells)
- 2. Enzymatic inactivation
- 3. Diffusion of NT away from synapse
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