Chapter 2 Flashcards
components that make up the synapse
- threshold of excitation reached.
- ion channels open and AP initiated at axon hillock.
- signal moves down axon.
- signal reaches terminal buttons.
Sherrington’s 3 properties of reflexes
- ) reflexes are slower than conduction along an axon.
- ) several weak stimuli presented a slightly different times/locations produce a stronger reflex than a single stimulus does.
- ) when one set of muscles become excited, a different set becomes relaxed.
Synaptic Delay
- speed of conduction along an axon is 40 m/s.
- speed of conduction through a reflex arc is slower and more variable (15 m/s or less).
reflexes
automatic muscular responses to stimuli.
synapse
a specialized gap between neurons.
reflex arc
the circuit from sensory neuron to muscle response.
temporal summation
the combined effect of quickly repeated stimulation at a single synapse.
presynaptic neuron
neuron that delivers transmission.
postsynaptic neuron
neuron that receives transmission.
spatial summation
the combined effect of several nearly simultaneous stimulations at several synapses onto one neuron.
excitatory postsynaptic potential (EPSP)
graded depolarization that results from a flow of sodium ions into the neuron.
leg flexion reflex
a sensory neuron excites a second neuron, which in turn excites a motor neuron, which excites a muscle.
law of reciprocal innervation
explains how a muscle will relax when its opposite muscle is activated.
inhibitory postsynaptic potential (IPSP)
- temporary hyperpolarization
- opens the gates for K+ to leave the cell or for Cl- to enter the cell.
synaptic cleft
the space between the presynaptic and postsynaptic membrane.
synaptic vesicle
a small sphere found in the terminal buttons, contain molecules of a neurotransmitter.
release zone
interiour of the presynaptic membrane to which vesicles attach and release their neurotransmitter into the synaptic cleft.
postsynaptic density
portion of postsynaptic membrane where receptors are located for binding.
synapses can occur at 3 places
- ) axodendritic (on dendrites).
- ) axosomatic (on the soma).
- ) axoaxonic (on other axons, between two terminal buttons).
axoaxonic synapses do not contribute to __________, they control ______________ with presynpastic _________ and _________.
- neural integration
- amount of chemical released by axon terminals.
- inhibition and facilitation.
presynaptic inhibition
reduces the amount of neurotransmitter released by the postsynaptic terminal button.
presynaptic faciliation
increases the amount of neurotransmitter released by the postsynaptic terminal button.
steps for synaptic neural communication
- ) synthesis and release of neurotransmitter from presynaptic terminals.
- ) activation of postsynaptic receptors.
- ) postsynaptic potential (EPSP/IPSP).
- ) termination of postsynaptic potential.
Explain the synthesis and release of neurotransmitter
- synthesis in some/terminal buttons.
- Ca+ channels open.
- synaptic vesicle fuses with membrane.
- vesicles break open and release neurotransmitters into synaptic cleft.
Explain the activation of postsynaptic receptors
a receptor in the postsynaptic membrane of a synapse that contains a binding site for a neurotransmitter.
neurotransmitter dependent ion channel
an ion channel that opens when a molecule of a neurotransmitter binds with post synaptic receptor.
ionotropic receptor
- fast acting.
- receptor with binding and ion channel.
metabotropic receptor
- has binding site for NT which activates an enzyme hat begins a series of events that opens an ion channel in the membrane.
- slow.
catecholamines
- NE & E –> fight or flight response, attention.
- DA –> movement, learning, perseveration, motivation, compulsion, emotion.
ligand gated ion channels
when the neurotransmitter attaches, it opens a channel.
g protein
a protein coupled with a metabotropic receptor, conveys messages to other molecules when a ligand binds with and activates the receptor.
second messenger
chemical produced when a G protein activates an enzyme; carries a signal that results in the opening of the ion channel or causes other events to occur in the cell.
- ex: cAMP
whether postsynaptic potential is excitatory or inhibitory depends on _____________.
the ion channels that the receptors open.
3 major types of neurotransmitter dependent ion channels:
- Na+
- K+
- Cl-
neural integration
process by which IPSP and EPSP summate and control the rate of firing of a neuron.
Reuptake
the reentry of a neurotransmitter just liberated by a terminal button back through its membrane, thus terminating the postsynaptic potential.
- astrocytes, DA/5HT transporter,
Enzymatic deactivation
the destruction of a neurotransmitter by an enzyme after its release.
- aCH, COMT, MAO
Reuptake + deactivation = __________________
postsynaptic cell is no longer stimulated.
autoreceptors
receptors that respond to the released transmitter by inhibiting further synthesis and release.
- metabotropic
- commonly inhibitory
neurotransmitter
chemicals produced within a neuron
- released into terminal button.
neuromodulator/neuropeptide
- not restricted to the synaptic cleft and diffuses through the extracellular fluid, traveling further and more widely dispersed.
- eg: dopamine, serotinin, ACh
hormone
chemical substance that is released by an endocrine gland into the blood that has effects on target cells in other organs.
ex: Cortisol, Insulin, Leptin
amino acids
- glutamate –> exctitatory, learning & memory
- GABA –> inhibitory
- glycine –> inhibitory, spinal cord, brain stem, retina.
Monoamines
- includes indolamine and catecholamines.
- ex: serotonin, DA, NE, E
Neuropeptides
endorphins, neuropeptide Y
Gases
nitric oxide
- released by many stimulated neurons which dilates blood vessels.
trytophan
- precursor to serotonin.
Phenylketonuria
a neurological disorder with the prescence of high levels of phenylpyruvic acid in the urine and is characterized by mental retardation.
- ex: mood
AcH
- primary neurotransmitter secreted by the efferent axons of the CNS
- facilitates all muscular movement
- involved in regulating REM sleep, perceptual learning and memory
Alzheimers
90% drop in Ach; use of anti-cholinesterase drugs.
3 main dopaminergic systems
Mesolimbic, Nigrostriatal, Mesocortical
Indolamine
- 5HT
- mood, eating, sleep, arousal, pain, dreaming.
Drugs that disturb 5HT
NDMA, LSD, SSRIs
gap junction
At an electrical synapse, the membrane of one neuron comes into direct contact with the membrane of another,
Electrical synapse
- ion channel always open and aligned.
- faster transmission than chemicals.
- cardiac muscles.
