Synapses & Neural Integration pt 1 Flashcards
what are synapses
how neurons communicate with other neurons or with effector organs
what are the types of synapses
electrical and chemical
how are electrical signals transmitted in electrical synapses, chemical synapses?
through gap junctions; thru neurotransmitter
what are the cells involved in electrical synapses
neuron to neuron; neuron to glial cell
where are electrical synapses found in the body
retina, brain: cortex, brainstem, hypothalamus, smooth and cardiac muscle, between neuroglial cells
what is the speed of communication for electrical synapses, is it uni or bidirectional
faster; mainly bidirectional
what is the type of communication for an electrical synapse
excitatory or inhibitory at same synapse due to bidirectionality of gap junction
what are the cells involved in chemical synapses
neuron to neuron or neuron to effector (e.g. muscle)
what is the speed of communication in chemical synapses, is it uni or bidirectional
slower but fast overall; always unidirectional
what is the type of communication for chemical synapses
excitatory or inhibitory since unidirectional
where are chemical synapses found in the body
almost everywhere (muscles, glands, tastebuds)
what are gap junctions, what are they made from
areas made of connexin proteins that join cells for a passageway for ions and molecules (connect with gap junctions of another cell)
what neural structures do chemical synapses involve
axons, dendrites, soma
what is a presynaptic neuron
one that sends a signal
what is a post synaptic neuron
one that receives a signal
describe a axosomatic synapse
axon on soma
describe a axoaxonic synapse
axon to axon
describe a axodendritic synapse
axon to dendrite
what is another name for an axon terminal
terminal/synapse bouton
describe the synaptic cleft
a small space between cells that makes a synapse
what is a neurotransmitter; where can it be found
a chemical that is released from the axon’s terminal boutons this happens in most synapses; vesicles have NTs
how are presynaptic and postsynaptic cells held close together
thru cell adhesion molecules (CAMs)
label a chemical synapse
….
label the anatomy of a synapse
….
describe chemical synaptic communication
- action potential depolarizes axon terminal and voltage-gated Ca+2 channels open
- Ca flows down electrochemical gradient into terminal of bouton
- synaptic vesicles fuse
- neurotransmitter is released to the post synaptic side
- response in postsynaptic neuron
- neurotransmitter binding is temporary for response until action potentials finish, the NT needs to be cleared thru: enzyme degradation, reuptake/recycle, whole diffusion
how much neurotransmitter is released and what does it depend on
based on concentration of calcium in axon terminal which depends on frequency of action potentials in presynaptic neuron
what happens if second (or many) action potentials arrive before neurotransmitter clears
action potentials keep bringing in calcium, you won’t have enough time for the neurotransmitter clearing which will keep creating a response
what is synaptic delay
time between arrival of an action potential and response in postsynaptic cell
what is synaptic delay caused by
changes in calcium ion entry, vesicle docking, release of neurotransmitter
describe post synaptic potential
change in membrane potential in response to receptor-neurotransmitter binding (graded potential)
what happens to the neurotransmitter after it diffuses across the synapse
binds to a specific receptor protein on the postsynaptic membrane; then NT is called ligand which results in opening of chemically regulated ion channels (aka ligand gates)
what is EPSP; what is the most common neurotransmitter
excitatory postsynaptic potential; graded depolarization from opening of Na+ or Ca+2 channels; glutamate
what is ipsp; what is the most common neurotransmitter
inhibitory postsynaptic potential; graded hyperpolarization from opening of K+ or Cl- channels; GABA
summarize excitatory NT action
presynaptic neuron: ap made by axon; ca+ voltage gated channels open; excitatory NT releases
postsynaptic neuron: densdrites and cell bodies open ligand gated channels; inward diffusion of na+ causes epsp; localized, decremental conduction of epsp; axon intiial segment opens voltage gated na+ and then k+ channels; axon conducts action potential
how do responses in post-synaptic cell occur
thru signal transduction pathways
what are the 2 types of signal transduction pathways; are they fast or slow
-channel-linked receptors (ionotropic receptors) are fast
-g-protein coupled receptors (metabotropic receptors) are slow
describe channel-linked receptors (ionotropic receptors)
NT binds and ions can move bidirectionally but not simultaneously
describe direct coupling of g-protein coupled receptors (metabotropic receptors)
NT binds to receptor; G protein activates which opens or closes ion channel
describe g-protein coupled receptors via second messenger
NT (first messenger) binds to receptor; G protein activates which activates or inhibits enzyme; a second messenger is produced; 2nd mes. opens/closes ion channels or produces other cell responses (slower acting process)
describe the main difference between excitatory and inhibitory synapses
excitatory more likely to produce an action potential (Vm closer to threshold) whereas inhibitory decreases chance of making action potential (Vm away from threshold)
