Flashcards in Chapter 12: Nervous Tissue (Part 2) Deck (61)
refractory period (2)
-the period of resistance to stimulation when an action potential can not be fired again
-only refers to a small patch of the neurons membrane
What are the 2 phases of the refractory period?
absolute & relative
absolute refractory period (2)
-no stimulate of any strength will trigger an action potential
-Na gates are open
relative refractory period (2)
-only especially strong stimulus will trigger an action potential
-K gates are open
For communication, the nerve signal must ______
travel to the end of the axon
Which fibers have voltage regulated ion gates along its entire length?
saltatory conduction in PNS
in myelinated fibers the signal seems to jump from node to node
What part of the myelinated fiber contains voltage gated ion channels?
Node of Ranvier
When a nerve signal reaches the end of the axon what happens?
triggers the release of neurotransmitters via exocytosis
Neurotransmitters stimulate what?
dendrites or directly onto a soma that triggers a local potential to the axon hillock
presynaptic neuron synapse with a dendrite
presynaptic neuron synapse with a soma
presynaptic neuron synapse with an axon of postsynaptic neuron
Where does typical synapse occur?
What type of junctions are in electrical synapse?advantages & disadvantages?
gap junctions that join adjacent cells
advantages:quick transmission no delay for release & binding
disadvantages:cannot integrate info & make decisions
Why is it possible to integrate info?
because of the transfer of electrical to chemical signals
What are the 4 categories of neurotransmitters?
2. amino acid neurotransmitters
Characteristics of neuropeptides? (5)
-chains of 2 to 40 amino acids
-act at lower concentrations
-longer lasting effects
-some function as hormones or neuromodulators
-stored in secretory granules
T/F Do neurotransmitters have the same effect everywhere in the body
What are the actions of neurotransmitters? (4)
-open ligand-regulated ion gates
-depend on receptor of post synaptic cell
3 Kinds of synapse
excitatory cholinergic synapse
employs ACh as its neurotransmitter (excites some postsynaptic cells & inhibits others)
inhibitory GABA-ergic synapse (3)
-employs gamma-aminobutyric acid as its neurotransmitter
-receptors are chloride channels
-postsynaptic neurons are inhibited
excitatory adrenergic synapse
-employs norepinephrine as its neurotransmitter
-act through second messenger system
-receptor is not an ion gate, but a transmembrane protein associated with a G protein
-slower to respond
What advantage does excitatory adrenergic synapse have over other synapses?
enzyme amplification:single molecule of NE can produce vast #s of product molecules in the cell
hormones, neuropeptides, and other messengers that modify synaptic transmission
How do neuromodulators modify synaptic transmission? (2)
-stimulate neuron to install more receptors in the postsynaptic membrane adjusting its sensitivity to the neurotransmitter
-alter the rate of the neurotransmitter synthesis
a neuromodulator family the inhibit spinal interneurons from transmitting pain signals to the brain
a neuromodulator (simple) gas released by postsynaptic neurons in some areas of the brain concerned with learning & memory