Modes of Communication
1
Q: Why is cellular communication essential in the body?
A: It is vital for coordination of bodily functions and maintenance of homeostasis.
2
Q: What are the four main modes of cellular communication?
A:
Autocrine signalling
Paracrine signalling
Endocrine signalling
Contact-dependent signalling
3
Q: Which forms of signalling are considered indirect?
A:
Autocrine
Paracrine
Endocrine
4
Q: Which form of signalling is considered direct?
A: Contact-dependent signalling.
5
Q: Why is contact-dependent signalling classified as direct?
A: Because cells are physically joined and communicate via gap junctions.
🔹 Contact-Dependent Signalling
6
Q: What structures enable contact-dependent signalling?
A: Gap junctions.
7
Q: What are gap junctions?
A: Porous protein tunnels that directly link the cytoplasm of adjacent cells.
8
Q: What can pass through gap junctions?
A: Small messenger molecules.
9
Q: Why is contact-dependent signalling important in cardiac muscle?
A: It allows cardiomyocytes to contract synchronously.
10
Q: Approximately how many times per minute do cardiomyocytes contract?
A: About 75 times per minute.
🔹 Autocrine Signalling
11
Q: Define autocrine signalling.
A: A cell releases a ligand that binds to receptors on the same cell.
12
Q: What does “auto” mean in autocrine?
A: Self.
13
Q: During what developmental process is autocrine signalling important?
A: Embryonic development and cell differentiation.
14
Q: How does autocrine signalling function during viral infection?
A: The infected cell releases signals that induce apoptosis.
15
Q: Is autocrine signalling short- or long-distance?
A: Very short distance (self-signalling).
🔹 Paracrine Signalling
16
Q: Define paracrine signalling.
A: Short-range communication between nearby cells.
17
Q: How do paracrine signals reach their target?
A: By diffusing across extracellular space.
18
Q: Are paracrine responses typically fast or slow?
A: Fast.
19
Q: Are paracrine responses long-lasting or short-lasting?
A: Short-lasting.
20
Q: Give an example of paracrine signalling.
A: Neurotransmitter release between neurons.
🔹 Endocrine Signalling
21
Q: Define endocrine signalling.
A: Long-distance communication via hormones transported in the bloodstream.
22
Q: What type of molecules are released in endocrine signalling?
A: Hormones.
23
Q: Where are endocrine signalling molecules secreted from?
A: Endocrine glands.
24
Q: How do endocrine signals travel to target cells?
A: Through the bloodstream.
25
Q: Are endocrine responses typically fast or slow?
A: Slow onset.
26
Q: Are endocrine responses short- or long-lasting?
A: Long-lasting.
27
Q: Give an example of an endocrine effect.
A: Hormonal regulation of growth and development.
🔹 Determinants of Target Cell Response
28
Q: What are three factors that determine a target cell’s response?
A:
Type of ligand
Type of receptor
Intracellular signalling molecules activated
29
Q: What ligand properties can influence cellular response?
A: Size, charge, hydrophobicity.
30
Q: Name four types of receptors discussed.
A:
Ion channel receptors
Enzyme-linked receptors
G-protein coupled receptors
Intracellular receptors
31
Q: Can one ligand produce different effects in different cell types?
A: Yes.
32
Q: Why can the same ligand cause different responses?
A: Different cells express different receptors and intracellular signalling pathways.
🔹 Extracellular Receptors
33
Q: Where are extracellular receptors located?
A: On the plasma membrane.
34
Q: What type of ligands bind extracellular receptors?
A: Hydrophilic ligands.
35
Q: What types of responses can extracellular receptor activation cause?
A:
Cell growth
Differentiation
Proliferation
Migration
Cell death
🔹 Intracellular Receptors
36
Q: Where are intracellular receptors located?
A: In the cytoplasm or nucleus.
37
Q: What type of ligands bind intracellular receptors?
A: Hydrophobic ligands.
38
Q: Why must intracellular ligands be hydrophobic?
A: So they can pass through the plasma membrane.
39
Q: What happens after a ligand binds an intracellular receptor?
A: The complex moves to the nucleus and binds DNA.
40
Q: What process is directly triggered by intracellular receptor activation?
A: Transcription and translation of new proteins.
41
Q: What is the key difference between extracellular and intracellular receptor signalling?
A:
Extracellular receptors activate signalling cascades;
Intracellular receptors directly regulate gene expression.