Nervous and Hormonal Communication

Nervous Communication

Neurons are specialised cells that transmit electrical impulses, forming the basis of all neural communication. There are different types including sensory, relay, and motor neurons.
Each neuron has a cell body, axon, and dendrites. The cell body contains the nucleus, the axon is a long fibre that carries impulses, and the dendrites pick up impulses from other neurons.
Myelin sheaths, composed of schwann cells, wrap around the axon of some neurons. This insulation speeds up nerve impulse transmission through a mechanism called saltatory conduction.
Synapses are junctions between two neurons that allow them to communicate. Neurotransmitters are released from the presynaptic neuron and bind to receptors on the postsynaptic neuron.
Action potentials are the electrical impulses that travel along the axon. They are caused by changes in permeability of the neuron’s cell membrane to sodium and potassium ions.
Resting potential keeps the inside of the neuron negatively charged relative to the outside. The opening of sodium channels and influx of Na+ ions cause depolarisation, which creates an action potential.
Refractory period prevents backward conduction of action potentials and ensures they are propagated in one direction only.

Hormones are chemical messengers secreted from endocrine glands that are transported in the bloodstream and bind to specific receptor proteins on target cells.
Hormones can be classified as steroid hormones (like cortisol), which are lipid-soluble and pass directly through the plasma membrane into the cell, and protein or peptide hormones (like insulin), which are water-soluble and bind to cell surface receptors.
Endocrine glands such as the pituitary, thyroid, and adrenal glands, secrete hormones directly into the bloodstream.
The hypothalamus in the brain is a key controller of hormonal communication, releasing hormones that control other endocrine glands.
Hormone action is characterised by time delay and lasting effect, in contrast to the immediate but short-lived response of nervous system.
The amount of hormones released is regulated by a mechanism called negative feedback, where a rise in hormone levels leads to decreased production.
Some hormone functions: glucagon and insulin regulate blood glucose levels, thyroxin controls metabolic rate, adrenaline prepares the body for stress response.