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Lecture 4

BIO270H1 Lecture Notes - Lecture 4: Endocrine Gland, Paracrine Signalling, Cell Surface Receptor

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Chris Garside

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Lecture 4
Cell signaling
o Communication between cells
o Produce messenger -> releases messenger -> activates response
Types of cell signaling
o Direct signaling: cytoplasm connecting: used for small molecules
Gap junctions
Aqueous pore between cells
Moves ions
Chemical messengers
Ex. cAMP
Moves through a hemi channel: 6 connexins
Dynamic can open or close
Increase in Ca2+
o Autocrine and paracrine signaling: (Indirect) short, rapid distance:
involves receptors
o Endocrine signaling: (Indirect) gland releases directly to circulatory
o Neural signaling: (Indirect) long distance across the cell, through the
synapse then is passed to a receptor
Indirect Signaling
o Signaling cell releases chemical messenger
o Messenger is carried through ECF
o Communication of signal to target cell
Messenger binds to receptor
Activates signal transduction pathway
Response in target cell
Indirect signaling: short and long distance
o Short
Chemical messenger diffuses in cell
Soluble messenger
Chemical messenger diffuses back to the signalling
Soluble messenger
Cell surface: signaling between juxtaposed cells
Membrane attached
o Long
Endocrine system
Chemical messenger (hormone) transported by
circulatory system
Nervous system
Electrical signal travels along a neuro and chemical
messenger (neurotransmitter) is released
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Across a synapse
o Exocrine: released to external environment (digestive tract); secreted
through acinus
o Endocrine: released to internal environment; ductless gland
Chemical messengers
o Peptide
o Steroids
o Amines
o Lipids
o Purines
o Gases
o Bold KNOWN hormones
o Structure of chemical messenger (hydrophilic vs. hydrophobic)
Peptide/ Protein hormones
o 2-200 a.a long
o Hydrophilic can travel in ECF
o Bind to receptors
o Rapid effects on cells
o Protein-protein phosphorylation
Protein hormone: synthesis and secretion
o Synthesis on RER (usually prprohormones)
o Stured in vesicls (often as prohormone
o Secreted by exocytosis
o Hydrophilic
o Travel to target cell and dissolved in ECF
Secretory pathways
o Regulated by signals stored in vesicles: released
Synthesis of AVP
o Posterior pituitary:
o Maturation of peptide
Peptides/Proteins bind transmembrane receptor
o Hydrophilic, soluble travel to target cell
o Bind to transmembrane receptors
Steroid hormones
o Derived from cholesterol
o Synthesisized by sER and mitochondria
o Mineralocorticoids
Electrolyte balance
o Glucocortoids
Stress hormone
o Reproductive hormone
Sex specific characteristics
Sites of steroid hormone biosynthesis
o Liver: cholesterol (from diet); modified steroids
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