Chapter 6 (Midterm 1) Flashcards
What are neurotransmitters?
chemical messenger used by neurons to communicate with each other or with effectors
What are types of neurotransmitters?
Biogenic amines, Acetylcholine, Gases, Neuropeptides, Amino acids, Purines (BAG-NAP)
What is an excitatory neurotransmitter synapse?
increases the likelihood that postsynaptic neuron will undergo APs (increases frequency of existing APs)
What is an inhibitory neurotransmitter synapse?
decreases the likelihood that postsynaptic neuron will fire an AP ( decreases the frequency of exisiting APs) – hyperpolarization
Where are neurotransmitters released?
presynaptic cleft
What is acetylcholine?
major nuerotransmitter in the PNS at the neuromuscular junction
What are biogenic amines?
neurotransmitters that are small charged molecules made from amino acids containing an amino group
What are amino acids as neurotransmitters?
most prevalent neurotransmitters in the CNS
What are neuropeptides as neurotransmitters?
short chains of amino acids with peptide bonds can be prepackaged as precursor proteins and is activated when cleaved
What are gases as neurotransmitters?
can diffuse from original cell into the intracellular fluid of other neurons/effector cells and bind to proteins to activate them
What are purines as neurotransmitters?
act as neuromodulators
What is spatial summation?
simultaneous inputs to different places on neuron are added together
What is temporal summation?
two or more inputs occurring at different times are added together
What is a synapse?
junction between two neurons where electrical activity in one neuron influences the excitability of the second
Excitatory Postsynaptic Potentials
depolarizing graded potential in postsynaptic neuron due to activated excitatory synapse
Inhibitory Postsynaptic Potentials
hyperpolarizing graded potential in postsynaptic neuron due to activated inhibitory synapse
What are electrochemical gradients?
differences in charges and ion concentrations across the membrane
What is the threshold level? (mV)
-55mV
What is the resting membrane potential? (mV)
-70mV
What is the refractory period?
the period when the axon (during an AP) cannot respond to any/another stimulus
What is the purpose of the refractory period?
help prevent signals from traveling in both directions down the axon at once
What are electrochemical forces?
the two forces that drive the diffusion of ions across the plasma membrane
What is equilibrium potential?
when the chemical force and the electrical force become equal in magnitude (cancel each other out in a sense)
What is an action potential?
large alterations in membrane potential, generally very rapid
What is a graded potential?
changes to a membrane potential that is confined to a relatively small region of the plasma membrane
What consists or doesn’t consist in a graded potential?
a refractory period and a threshold, does not meet threshold, may include ligand-gated ion channels and leak channels
Examples of graded potentials
synaptic, receptor, pacemaker
What determines the magnitude of membrane depolarization in a graded potential?
intensity of the initial stimulus
What mechanism does the nervous system use to communicate over long distances?
action potential
Where are graded potentials found within the neuron?
generally in the dendrites/soma part of the neuron
Where are action potentials found within the neuron?
occur in parts of neuron where Na/K voltage gated channels are abundant on the membrane
What are electrical synapses (junctions)?
the presynaptic neuron is DIRECTLY connected to the post-synaptic neuron || gap junctions
What are chemical synapses?
use neurotransmitters to communicate = INDIRECTLY connected
What is the relative permeability of the membrane to Na and K at rest?
much more permeable to K
Under action potential conditions, how does the relative permeability of the membrane change?
It is more permeable to Na since a bunch of Na voltage-gated channels open due to the AP
How do changes in the stimulus be presented to the CNS
information to the CNS is transmitted by the changing frequency of the APs
What is an absolute refractory period?
during an AP, second stimulus does not produce a second AP, inactivated Na channel contributes to this
What is a relative refractory period?
after absolute refractory period, second AP potential can be produced if the stimulus strength is greater
What is the effect of myelination?
reduces the amount of current “leaking” through membrane = improves electrotonic conduction
What is the main role of calcium ions at chemical synapses?
cause fusion of synaptic vesicles with the plasma membrane of the axon terminal
How do graded potentials end?
diffusion of ions via leak channels
How do action potentials end?
closure of voltage-gated Na channels post-inactivation, opening of K+ vg channels and activation of Na/K ATPase – return membrane potential to rest
