Flashcards in The synapse Deck (31)
What is the function of the dendrites?
Receive inputs from other neurones and convey graded electrical signals passively to the soma
What is the function of the soma (cell body)?
Synthetic and metabolic centre. Contains the nucleus , ribosomes, mitochondria and endoplasmic reticulum. Intergrates incoming signals that are conducted passively to the axon hillock
What is the function of axon hillock and initial segment?
Site of initation of the 'all or none' action potential
What is the function of the axon?
Conducts output signals as action potentials to other neuroes (or other cells). Mediates transport of materials between the soma and presynaptic terminal and vice versa
What is the function of the synapse?
A point of chemical communication between neurones
What holds the pre- and post- synaptic membranes together?
A matrix of fibrous extracellular protein within the cleft
What does vesicles in the presynaptic terminal store ?
What is the gray's type 1 synapse?
Asymmetrical synapses in which the membrane differentiation on the postsynaptic side is thicker than the presynaptic side (usually excitatory in function)
What is the gray's type 2 synapse?
Symmetrical synapses in which the membrane differentiations are of similar thickness (usually inhibitory in function)
What is a axodendritic synapse?
Axons joins at post synaptic dendrite
What is a axosomatic synapse?
Axon joins at the soma
What is a axoaxonic synapse?
Axon meets at axon
what two categories of synapses are there?
What causes the excitatory postsynaptic potential?
Glutamate activates postsynaptic , cation selective, ionotropic, glutamate receptors generating a local, graded , excitatory (depolarising) response
What causes the inhibitory postsynaptic potential?
GABA, or glycine, activates postsynaptic, anion selective, ionotropic, GABAA, or glycine, receptors generating a local, graded, inhibitory (hyperpolarizing) response
What is spatial summation?
Many inputs converge upon a neurone to determine its output
What is temporal summation ?
A single input may modulate output by variation in action potential frequency of that input
What are released from synaptic vesicles ?
Amino acids and amines
What are released from secretory vesicles?
What can activate ionotropic ligand-gated ion channels (LGiCs)?
What is the 9 steps of neurochemical transmission?
1)Upatke of precursor
2)Synthesis of transmitter
3)Storage of transmitter
4)Depolarization by action potential
5)Ca2+ influx through voltage-activated Ca2+ channels
6)Ca2+ induced release of transmitter (exocytosis)
8)Enzyme-mediated inactivation of transmitter OR
9)Reuptake of transmitter
How are GABA and amines synthesised?
Must be synthesised by the neurones that release them,requiring specific enzymes
How are the enzymes synthesised in the cell body transported to the presynaptic terminal?
How are synaptic vesicles made?
-synpatic vesicle made
How are neurotransmitters synthesised?
1)Synthesis of precursor peptide by ribosomes associated with the rough endoplasmic reticulum (ER)
2)Cleavage of precursor peptide in Golgi apparatus yielding active neurotransmitter
3)Secretory granules bud off from the Golgi apparatus
4)Secretory granules are transported to the presynaptic terminal by fast axoplasmic transport
What are the key features of exocytosis : transmitter release?
-Synaptic vesicles ready for rapid release are held in apposition to the presynaptic membrane in a docking complex (SNARE complex)
-Depolarization of the presynaptic membrane (arrival of the action potential) opens voltage-activated Ca2+ channels, causing a rise in the concentration of Ca2+ in the vicinity of the docked vesicles
-Ca2+ binds to synaptotagmin-1 in the vesicle membrane causing the vesicle to fuse with the presynaptic membrane
-Neurotransmitter diffuses from vesicles into the synaptic cleft
-Membrane added to the presynaptic terminal is retrieved by endocytosis
What are neurotransmitter dependant on?
What do ligand-gated channels consist of?
Consist of separate glycoprotein subunits that form a central , ion conducting channel
What are the 3 states of ligand-gated channels?
1) Unoccupied and close
2)Occupied and close
3)Occupied and open