Chapter 12 Vocabulary Flashcards
The membrane potential at which an action potential begins
Threshold (-60 to -55 mV)
A graded hyperpolarization of the postsynaptic membrane
Inhibitory Postsynaptic Potentials
In communication between two cells, the axon terminal of the presynaptic cell most commonly releases these chemicals into the synaptic cleft
Neurotransmitters
All the voltage-gated sodium channels either are already open or are inactivated, and another action potential cannot be propagated
Absolute refractory period
The addition of stimuli occurring in rapid succession at a single synapse that is active repeatedly
Temporal summation (tempus = time)
The sodium channels have regained their normal resting condition, but the membrane potential has not yet stabilized
Relative refractory period
Cause depolarization and promote the generation of action potentials
Excitatory neurotransmitters
Consists of the brain and spinal cord
Central nervous system
Synapses that release norepinephrine
Adrenergic synapses
Changes in the membrane potential that cannot spread far from the site of stimulation
Graded potentials
A graded depolarization caused by the arrival of a neurotransmitter at the postsynaptic membrane
Excitatory Postsynaptic Potentials
This is how an action potential travels along unmyelinated axons
Continuous propagation
Occurs when simultaneous stimuli applied at different locations have a cumulative effect on the membrane potential
Spatial summation
This division of the PNS brings sensory information from the PNS to the CNS
Afferent division
Typical resting membrane potential
-70 mV
Controls skeletal muscle contractions
Somatic nervous system
How an action potential travels over a myelinated axon
Saltatory propagation
Neurons which form the efferent division of the PNS
Motor neurons
States that the properties of an action potential are independent of the relative strength of the depolarizing stimulus, as long as that stimulus exceeds the threshold
All-or-none principle
Propagated changes in the membrane potential that, once initiated, affect an entire excitable membrane. These electrical events are also known as nerve impulses.
Action potential
Activity at an axoaxonic synapse increases the amount of neurotransmitter released when an action potential arrives at the axon terminal
Presynaptic facilitation
A compound, released by the axon terminal, which alters the rate of neurotransmitter release by the presynaptic neuron or changes the postsynaptic cell’s response to neurotransmitters
Neuromodulators
The release of GABA inhibits the opening of voltage-gated calcium channels in the axon terminal
Presynaptic inhibition
The process of restoring the resting membrane potential after depolarization
Repolarization
Synapses that release ACh
Cholinergic synapses
Bundles of axons which carry sensory information and motor commands, along with their associated blood vessels and connective tissues
Nerves
Cause hyperpolarization and suppress the generation of action potentials
Inhibitory neurotransmitters
Any shift from the resting membrane potential towards a more positive potential
Depolarization
Open or close when they bind specific chemicals
Chemically gated channels
Open or close in response to the membrane potential
Voltage gated channels
During repolarization, the inside of the cell becomes more negative than the resting membrane potential
Hyperpolarization
Automatically regulates smooth muscle, cardiac muscle, glandular secretions, and adipose tissue at the subconscious level
Autonomic nervous system
Neurons which form the afferent division of the PNS
Sensory neurons
This division of the PNS brings motor commands from the CNS to muscles, glands, and adipose tissue
Efferent division
These are always open, however, their permeability can vary from moment to moment as the proteins that make up the channel change shape in response to local conditions
Leak channels
Consists of all neural tissue outside of the brain and spinal cord
Peripheral nervous system
