Cell Signalling Overview

Cell Signalling Overview

• Cell signalling is how cells communicate with each other.
• There are three main types: endocrine, paracrine, and synaptic.

Endocrine Signalling

• Hormones are released by glands.
• Hormones travel through the bloodstream.
• Hormones exert effects on distant cells.
• This type of signalling is slow but has a long-lasting effect.

Paracrine Signalling

• Chemicals are released by cells.
• They act on nearby cells.
• This type of signalling involves localized effects.
• Chemicals don't enter the bloodstream.

Synaptic Signalling

• Nerve cells communicate quickly.
• Messages are sent electrically down the nerve cell.
• When the message reaches the end of the nerve cell, it causes release of a chemical.
• This chemical travels across a small gap.
• The chemical binds to receptors on the target cell.
• This is a very localized process.

Other Key Concepts

• Autocrine signalling: Special case where cells signal themselves.
• Ligands: Molecules that bind to receptors.
• Receptors: Proteins that bind to ligands and trigger a response.
• Signal transduction: Converting one signal into another.
• Response: The effect of the signalling molecule on the target cell.
• Speed of response: Different types of signalling have different speeds, ranging from very fast (synaptic) to relatively slow (endocrine).
• Duration of response: Effect can be short-lived (synaptic) or long-lasting (endocrine).
• Specificity: Different cells react differently to the same signal based on having the appropriate receptors.
• Local effects versus long-range effects: Paracrine and endocrine signalling differ in their reach.
• Methods of signal transmission: Some signals are electrical, others are chemical.

Receptor Types and Function

• Ion channels: Ligand binding opens the channel, allowing ions to flow.
• Membrane bound enzymes: Ligand binding causes the enzyme to activate, leading to a cellular response.
• G protein-coupled receptors: Ligand binding triggers a cascade inside the cell via G-proteins.
• Intracellular receptors: Lipophilic ligands can pass through the membrane and bind to receptors inside the cell.

Moodle Recap Quiz Summary (Questions and Answers)

• Synaptic transmission details: Action potential, neurotransmitter, synaptic cleft, postsynaptic receptor.
• Second messenger signalling features: Different pathways, sustained response, signal amplification.
• Response determination factors: Receptor type, signal level, pathway availability.
• Autocrine signalling definition: Acts on the cell that produces it.
• Paracrine signalling definition: Local effects on neighboring cells.
• Endocrine signalling definition: Long-distance effects via the bloodstream from glands.
• Neurotransmitter packaging: Membrane-bound vesicles.
• Exception: Non-vesicle packaging (e.g., nitric oxide) due to their lipophilic nature.

This quiz covers the fundamentals of cell signalling, detailing the three primary types: endocrine, paracrine, and synaptic signalling. Explore how these mechanisms allow cells to communicate and respond to their environment, as well as the unique characteristics of each signalling type.