Lecture 4 - neuron

Endocrine system

Coordinates cell activities slowly and globally by secreting hormones into the bloodstream.

Nervous system

Transmits rapid, precise electrical impulses across cells to coordinate and adjust ongoing activity.

Metabolic vulnerability

Neuron’s lack energy storage capacity and require continuous supplies of glucose and oxygen; activity ceases within seconds cells die within minutes if supply is interrupted

Developmental lifespan

Neuron’s originate from neural stem cells and do not divide. Neurogenesis

Astrocytes - Glia cell

Star-shaped cells providing physical structure, Waste clearance, nutritional via the blood-brain barrier and modulation of neural signalling

Microglia - glica cell

Small, mobile cells providing defensive immune functions, phagocytosis of dead neuronal material and secretion of repair-promoting chemicals.

Oligodendroglia - glica cells

Cells extending fatty membranes that wrap around axons to form an insulating myelin sheath in the central nervous system

Resting potential

Maintained across the semipermeable neuronal membrane at 70mV through unequal distributions of ions

Electronic transmission

Passive, graded movement of ions along dendrites and soma; signal magnitude is variable and decays of a distance.

Action potential generation and dynamics

• Hodgkin-Huxley cycle

• Threshold

• Depolarisation and depolarisation

• Hyper-polarisation

• All or nothing law

Hodgkin-Huxley cycle

Membrane depolarisation opens voltage-fated (Na+) channels, causing (Na+) influx that triggers further depolarisation

Threshold

An action potential is triggered to the axon hillock when local depolarisation reaches approximately (50mV); sub threshold changes revert to resting potential

Depolarisation and repolarisation

Na+ influx peaks the membrane potential at (+50mV) closing (Na+) channels and opening (K+) channels to drive rapid (K+) efflux

Hyper-polarisation

Transient (K+) excess outflow drops potential below (-70mV), establishing a refractory period of (2-5ms) that prevents backward propagation

All or nothing law

Action potentials maintain constant amplitude without decay regardless of stimulus strength

Membrane potentials and gradients

• resting potential

• Sodium-potassium pump

• Electronic transmission

Glia cell types and functions

• astrocytes

• Microglia

• Oligodendroglia

Coordination systems and neuronal properties

• endocrine system

• Nervous system

• Metabolic vulnerability

• Developmental lifespan

depolarisation

Membrane - becomes more positive (less negative) - creating action potential.
This occurs when sodium ions flow into the cell, altering the electrical charge across the membrane.

Hyperpolarisation

Membrane becomes more negative than the resting potential, often due to the influx of chloride ions or efflux of potassium ions.

saltatory conduction

The process by which action potentials jump from node to node along a myelinated axon, speeding up signal transmission.

agonist

A substance that activates a receptor to produce a biological response, mimicking the action of a naturally occurring substance.

antagonist

A substance that binds to a receptor and inhibits or blocks its action, opposing the effects of an agonist.