Week 8 CTL Notes
Chemical Communication: Endocrinology ctd.
Regulation of cell and body function
Purpose of intercellular signalling:
• To aid cells in coordinating their functions towards the common good of a multicellular organism.
• Cells must interpret the multitude of signals from other cells to help coordinate their functions.
• Effects of coordinated functions include:
o Movement
o Growth
o Reproduction
o Digestion
o Metabolism
o Circulation
o Respiration
o Senses
o Temperature
o Balance
o Immune system
o Differentiation
o Death (apoptosis)
• NB: different cells may respond to the same signal in
different ways.
Signal Transduction
• Communication frequently involves converting signals from one form to another.
o Signalling cell produces a signal molecule. (proteins /peptides /amino acids /nucleotides
/steroids /fatty-acid derivatives /gasses)
o Signal molecule is detected by target cell.
o Receptor protein receives the signal & transduces it to an intracellular signal.
o Intracellular signal relayed, amplified, & diverged along a signalling ‘cascade’
o Intracellular signals received by target proteins inside cell, altering cell behaviour.
www.MedStudentNotes.com
, Long or Short Range?
• Endocrine Signalling: Some signals are “broadcasted” throughout the entire body via bloodstream.
à Hormones (produced by endocrine cells) [TV]
• Autocrine: Signals that affect only cells of the same cell type as the emitting cell. [doctor conference]
• Paracrine: Signals (aka local mediators) that act on cells in the vicinity of the emitting cell but on
different cell types than the emitting cell. [Lecture]
• Neuronal: Specific messages are delivered across long distances to specific target cells. [phone call]
• Contact dependant: Does not require secretion of signal molecule. Instead, cells make direct contact
through signalling molecules and receptors lodged in their plasma membranes.
2 Main Receptor Types: (Intracellular & Membrane-bound Receptors)
-Determined by how the hormone receptor binding is relayed to the cytoplasm.
-Mechanism depends on chemical nature of the hormone & the cellular location of receptor.
• Intracellular Receptors:
o Lipid-soluble hormones (steroid/thyroid hormones) & even gasses (nitric oxide-blood
vessel dilation)
§ Can diffuse straight through the membrane.
• Steroid hormones bind to receptor proteins in the cytosol or the nucleus
that regulate gene expression.
• Other signal molecules activate intracellular enzymes.
§ Once bound, the
receptor protein
undergoes a large
conformational
change and
‘activates’, allowing it
to promote/inhibit
transcription of a
select set of genes.
www.MedStudentNotes.com
Chemical Communication: Endocrinology ctd.
Regulation of cell and body function
Purpose of intercellular signalling:
• To aid cells in coordinating their functions towards the common good of a multicellular organism.
• Cells must interpret the multitude of signals from other cells to help coordinate their functions.
• Effects of coordinated functions include:
o Movement
o Growth
o Reproduction
o Digestion
o Metabolism
o Circulation
o Respiration
o Senses
o Temperature
o Balance
o Immune system
o Differentiation
o Death (apoptosis)
• NB: different cells may respond to the same signal in
different ways.
Signal Transduction
• Communication frequently involves converting signals from one form to another.
o Signalling cell produces a signal molecule. (proteins /peptides /amino acids /nucleotides
/steroids /fatty-acid derivatives /gasses)
o Signal molecule is detected by target cell.
o Receptor protein receives the signal & transduces it to an intracellular signal.
o Intracellular signal relayed, amplified, & diverged along a signalling ‘cascade’
o Intracellular signals received by target proteins inside cell, altering cell behaviour.
www.MedStudentNotes.com
, Long or Short Range?
• Endocrine Signalling: Some signals are “broadcasted” throughout the entire body via bloodstream.
à Hormones (produced by endocrine cells) [TV]
• Autocrine: Signals that affect only cells of the same cell type as the emitting cell. [doctor conference]
• Paracrine: Signals (aka local mediators) that act on cells in the vicinity of the emitting cell but on
different cell types than the emitting cell. [Lecture]
• Neuronal: Specific messages are delivered across long distances to specific target cells. [phone call]
• Contact dependant: Does not require secretion of signal molecule. Instead, cells make direct contact
through signalling molecules and receptors lodged in their plasma membranes.
2 Main Receptor Types: (Intracellular & Membrane-bound Receptors)
-Determined by how the hormone receptor binding is relayed to the cytoplasm.
-Mechanism depends on chemical nature of the hormone & the cellular location of receptor.
• Intracellular Receptors:
o Lipid-soluble hormones (steroid/thyroid hormones) & even gasses (nitric oxide-blood
vessel dilation)
§ Can diffuse straight through the membrane.
• Steroid hormones bind to receptor proteins in the cytosol or the nucleus
that regulate gene expression.
• Other signal molecules activate intracellular enzymes.
§ Once bound, the
receptor protein
undergoes a large
conformational
change and
‘activates’, allowing it
to promote/inhibit
transcription of a
select set of genes.
www.MedStudentNotes.com
