Please enable JavaScript.
Coggle requires JavaScript to display documents.
Ion Channels and Ionotropic Receptors - Coggle Diagram
Ion Channels and Ionotropic Receptors
How is resting potential generated?
2 separate environemtns
Extracellualr
Intracellular
Sepaarted by semi-permeable cell membrane
Potential differece extablished bteween intra and extracellular evirnemtn (Vm or membrane potential)
Anionic macromolecules in cytoplasm
Intracellular environemtn
Canot pass through semi-permeable membrane
DNA, proteins, etc.
Number of positively charged ions to balance charge
e.g. potassium exists in high levels inside the cell
These can move down concentration gradient via ion chanels
Extracellular environemtn
Primarily sodium ions
Balanced by chloride ions
Ion levels maintained by sodium potassium pump
Sits across plasma membrane
Depolarisation
Addition of positive charge inside cell
Hyperpolarisation
Addition of negative charge inside cell
Types of voltage-gated ion channels
K\(^+\) channels
Largest, most diverse class
Function
Generation of resting membrane potential
Na\(^+\)
Function
Generation of action potential
Ca\(^{2+}\)
Function
Generation of action potential in some neurons
Affect on intracellular Ca\(^{2+}\) conc. regulates many biochemical signalling processes
Cl\(^-\)
Function
Control of neuronal excitability
Contribute to resting membrane potential
Regulate cell volume
Structure of channels
Inserted into membrane
Intra and extracellular regions
e.g. K\(^+\) channel
Extracellular region has -ve charge to attract cations
By -ve charged amino acids at opening
Water is stripped off during passage
After passage, the ion reassociates with water to become hydrated again
Conformational change in channel occurs to open it
Volatge needed
Structure on cytoplasmic side
Inavctivating particle
Stops ionic fluxes
Blocks channel for an amount of time
Refractory period
Important for unidirectional property of action potential
Firing signal
Excitatory post-synaptic potential (EPSP)
If of sufficient magnitude
Takes depolarisation past threshold potential
Past threshold, action potential
will
occur
Myelination
Electrical insulation
Myelin sheath
COncentric membrane wrapped around axon
Oligodendrocyte in CNS
Schwann cells in PNS
No ion channels where membrane lays
Creates nodes of electrical excitation
Action potential jumps from node to node
Increases speed of propagation
Demyelinatiin disorders
MS
Strippig away of myelin
Locomotion problems
Ligand-gated ion channels
Neurotransmitter channels
Acetylcholine (nicotinic) receptor
Excitatory
Dependent on dietary intake of glucose
Action potential causes exocytosis of acetylcholine vesicles from synapse into synaptic cleft
Quickly broken down by ACh esterase and choline is repackaged and transported back into cell
Serotonin receptor
Low levels of serotonin assoc. with depression
Acts on G-protein coupled receptors too
GABA\(_A\)
Ligand gated chloride channels
Promotes hyperpolarisation
Make cell less excitable
Glycine receptor
Promote hyper-polarised state
AMPA-kainate glutamate receptor channel
Ligand gated sodium channel
Quicker acting
NMDA glutamate receptor channel
Ligand gated calcium channel
Longer acting
Memory formation
via sensory info. processing in hippocampus
Ihibition of NMDA receptor
No memories formed
Ca\(^{2+}\)/CGMP/cAMP channels
Second messengers bind to intracellular surface pf channel
Convert intracellular signals into electrical info.
Sensory transduction e.g. conversion of odors and light