Cells Communicate Using Signalling Chemicals That Regulate Physiological Processes
- In multicellular organisms, these signalling chemicals are diverse and can be grouped into several functional categories.
- These include:
- Hormones
- Neurotransmitters
- Cytokines
- Calcium ions.
- In a bustling city, traffic lights control the flow of cars, walkie-talkies keep police officers connected, and emergency sirens alert everyone to urgent situations.
- Each of these signals serves a unique purpose, ensuring the city runs smoothly.
- Similarly, your body relies on a variety of signalling chemicals to coordinate its activities.
Hormones Are The Long-Distance Messengers
Hormone
Hormones are chemical messengers secreted by endocrine glands into the bloodstream.
- Hormones are like the postal service of your body, delivering messages over long distances.
- They are produced by endocrine glands and travel through the bloodstream to reach target cells.
Insulin, produced by the pancreas, regulates blood sugar levels by signaling cells to absorb glucose.
Key Features of Hormones
- Wide Reach: Hormones can affect cells far from their origin.
- Specificity: Only target cells with the right receptors respond to a hormone.
- Long-Lasting Effects: Hormones can remain active for hours or even days.
- Slow Action: Hormonal responses are slower compared to other signals, as they rely on blood circulation.
Hormones are classified based on their chemical structure, such as peptides (e.g., insulin), steroids (e.g., testosterone), or amines (e.g., thyroxin).
TipRemember: Endocrine glands release hormones into the bloodstream, while exocrine glands use ducts to secrete substances like sweat or saliva.
Neurotransmitters Are The Rapid Communicators
- Neurotransmitters are the body’s instant messaging system, transmitting signals across synapses,the tiny gaps between neurons.
- They enable rapid communication within the nervous system.
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.
Acetylcholine is a neurotransmitter that triggers muscle contractions by transmitting signals from motor neurons to muscle fibers.
Key Features of Neurotransmitters
- Short Distance: Neurotransmitters act across synapses, typically just 20–40 nanometers wide.
- Fast Action: Signals are transmitted in milliseconds, enabling quick responses.
- Short-Lived Effects: Neurotransmitters are quickly broken down or reabsorbed, ensuring precise control.
- Localized Impact: They affect only the postsynaptic neuron or muscle fiber they bind to.
- Don’t confuse neurotransmitters with hormones!
- While both are signalling molecules, neurotransmitters act over short distances and have rapid, short-lived effects.
