Synapses Flashcards
Synapse
junction between two cells where they communicate with each other
Presynaptic cell
The cell that transmits a signal toward the synapse
Postsynaptic cells
The cell that receives the signal from the synapse
Types of synapses (2)
Electrical
Chemical
Electrical synapses
Occur between gap junctions, where local currents flow directly form one cell to a neighboring cell
Important in cardiac muscle cells and many types of smooth muscle
Connexons
Structures that separate adjacent cell membranes in gap junctions.
They are 6 tubular proteins
Chemical synapses
Occurs where a neurotransmitter (chemical messenger) communicates a message to an effector
3 components of a chemical synapse
Presynaptic terminal - end of an axon
Synaptic cleft - space between the end of the axon and the cell with which is synapses
Postsynaptic membrane - membrane of the postsynaptic cell
What causes the neurotransmitter release?
Action potentials in the presynaptic terminal
Synaptic vesicles
an organelle in the cytoplasm that contains neurotransmitters
Neuromodulators
Substances released from neurons that influence the likelihood of an action potential being produced in the post-synaptic cell
Excitatory postsynaptic potentials (EPSP)
the graded potential that results from the depolarization of the postsynaptic cell.
Might produce an action potential
Occurs because the membrane becomes more permeable to Na+
How do local anesthetics work?
The block voltage-gated Na+ channels, which prevent action potentials from propagating along sensory neurons, which means neurotransmitters are not released and EPSPs can’t be produced.
Inhibitory postsynaptic potential IPSP
when neurotransmitter and receptor results in hyperpolarization of the postsynaptic membrane
Move the membrane further from threshold, decreasing the likelihood of an action potential
Acetylocholine // effect and clinical examples
Effect: excitatory in CNS; inhibitory or excitatory in ANS
Myasthenia Gravis - weakness & even paralysis
Serotonin // effect and clinical examples
Inhibitory and excitatory
Antidepressant (Depression
Anxiety (OCD)
Halucinogens (LSD)
Dopamine
Excitatory or inhibitory
Drug Addiction
Parkinson Disease (results from destruction of dopamine producing neurons)
Norepinephrine
Excitatory
AHDH
Amphetamines
Gamma-Amino Butyric Acid
Inhibitory
Barbiturates - sedatives, treatmnet for epilepsy
Benzodiazepines - antianxiety drugs
Alcholo Dependence
Glycine
inhibitory
Strychnine poisoning > powerful muscle contractions and convulsions, may cause death
Glutamate
Excitatory
Stroke and Excitotoxicity
Cognition
Adensoine
Inhibitory
Neutoprotective agent
Caffein
Substance P
Excitatory
Pain therapy
Endorphins
Inhibitory
Opiates // produce feeling of euphoria and reduce pain
Nitric oxide
Excitatory
Stroke damage
Treatment of ED
Types of summation (2)
Spatial summation
Temportal summation
Spatial summation
multiple action potentials from separate neurons arrive simultaneously at the same postsynaptic neuron
Temporal summation
two or more action potentials arrive very close together at the postsynaptic cell
First AP > depolarizing graded potenta=ial
2) a second graded depolarization returns membrane to resting value
4 types of neuronal pathways
Convergent pathways
Divergent pathways
Reverberating circuits
Parallel after-discharge circuits
Convergent pathway
Multiple neurons converge upon and synapse with a smaller number of neurons
EG-
Divergent pathway
info from one neuronal pathways diverges into two or more pathways
EG - sensory input can go to both the spinal cord and the brain
Reverberating circuits
A positive feedback loop that causes an after-discharge, which prolongs the response to a stimulus
EG - respiration
Parallel after-discharge circuits
Neurons that stimulate several neurons in a parallel organization, converging upon a common output cell.
Involved in complex neuronal processes - mathematics,
