Neurons, action potentials, synapses, neurotransmitters, synaptic plasticity, CNS/PNS organization.
Nervous System Physiology
Neuron
Excitable cell transmitting information via electrical (action potentials) + chemical (neurotransmitter) signals. Compartmentalised:…
Resting membrane potential
Steady-state voltage across plasma membrane (~-70 mV in neurons) set by differential ion permeability + Na+/K+ ATPase gradients.…
Action potential
All-or-none (~100 mV) voltage spike propagating along axon: Na+ influx (depolarisation) → K+ efflux (repolarisation) → hyperpolarisation →…
Hodgkin-Huxley model
Hodgkin-Huxley 1952: quantitative model of squid axon action potential using voltage-dependent Na+ and K+ conductances with gating…
Synapse
Specialised junction for signal transmission between neurons. Chemical (neurotransmitter-mediated, most common) or electrical…
Neurotransmitter
Chemical messenger released from presynaptic terminal, diffuses across cleft, binds postsynaptic receptors. Classes: amino-acid (glutamate,…
Synaptic plasticity
Activity-dependent changes in synaptic strength — biological substrate of learning + memory. Hebbian: 'neurons that fire together wire…
Long-term potentiation (LTP)
Persistent (hours-days) enhancement of synaptic strength after high-frequency stimulation. NMDA-receptor Ca²+ influx → CaMKII →…
Excitatory/inhibitory balance
Glutamate (excit.) + GABA (inhib.) dominate fast synaptic transmission. E/I balance required for normal cortical function; imbalance…
Neurovascular coupling & BOLD
Active neurons trigger local vasodilation (astrocyte + interneuron signalling). Basis of fMRI BOLD signal. Coupling can break down in…