Localized and Distant Effects of Signalling Molecules
- Imagine you’re in a crowded room.
- To communicate with someone nearby, you whisper.
- But to reach someone across the room, you shout or use a microphone.
- Cells face similar challenges when sending signals.
- They rely on signalling molecules to communicate, whether the target is right next door or far away.
Definition
Signalling molecules
Signalling molecules are chemicals that transmit information between cells, triggering specific responses in target cells.
Localized Signalling: Neurotransmitters
Definition
Neurotransmitter
Neurotransmitters are chemical signals used by neurons to communicate across synapses, the tiny gaps between nerve cells or between nerve cells and other target cells.
How Neurotransmitters Work
- Release: When a nerve impulse reaches the end of a presynaptic neuron, neurotransmitters are released into the synaptic gap.
- Diffusion: They travel a short distance (20–40 nm) across the gap.
- Binding: Neurotransmitters bind to receptors on the postsynaptic neuron, triggering a response.
Acetylcholine is a neurotransmitter that binds to receptors on muscle cells, causing them to contract.
Key Characteristics of Neurotransmitters
- Short Distance: They act over extremely short distances, ensuring precise communication between neurons.
- Rapid Action: Signals are transmitted in milliseconds, allowing for quick responses.
- Short-Lived Effects: Neurotransmitters are quickly broken down or reabsorbed, preventing prolonged effects.
- Don’t confuse neurotransmitters with hormones.
- Neurotransmitters act locally and quickly, while hormones have broader and longer-lasting effects.
Definition
Hormones
Hormones are chemical messengers that travel through the bloodstream to regulate various physiological processes.
Distant Signalling: Hormones
How Hormones Work
- Secretion: Hormones are released into the bloodstream by endocrine glands.
- Transport: They travel throughout the body, reaching distant target cells.
- Binding: Hormones bind to specific receptors on target cells, triggering a response.
