Principles of cell communication Flashcards
What are the 3 principles of cell communication?
- Cell communication 2. Receptors 3. Hormones
What does cell communication involve?
The receiving and sending of information (signals) between cells. Signals can be from other cells or from environmental sources and trigger a response by the cell
True or false: Signals cannot be received across the cell membrane in order for the cell to respond?
False - signals that cells receive MUST be transmitted across the cell membrane so that the cell can respond.
Can all signalling molecules cross a cell membrane by themselves?
Some can - but others require a signal to interact with a specific receptor on the cell membranes and transmit that signal to the interior of the cell.
How do signals most often move through the cell?
By passing from protein to protein in a signalling pathway or cascade. At each step - proteins are modified in some way and the signal is often amplified to form a much larger response (amplification) often resulting in multiple effector functions being stimulated.
How many signals can a cell receive at any given time?
multiple simultaneously - extremely complex, that in turn activate different signalling pathways - cross talk helps regulate and control the signalling pathways so that an appropriate response is initiated
What do these combinations of signalling molecules regulate in the cell?
cell survival cell differentiation cell division cell death (apoptosis)
What are the 7 different signalling molecules?
- Hormonal 2. Electrical 3. External 4. Mechanical 5. Immunological 6. Metabolic 7. Dissolved gases
What is the essential component of chemical communication?
Intracellular signalling proteins
What are the main types of cell signalling?
- Gap junctions 2. Cell-to-cell (direct) signalling 3. Cell-to-cell signalling via secreted molecules 4. External environmental factors 5. Mechanical
What is the simplest type of cell signalling?
Gap Junctions: aqueous pores or channels - link to interior of adjacent cells -allow direct electrical and chemical communication between cells - Quick signalling - permeability regulated by changes in cytosolic concentrations (Ca2+, cAMP, pH)
What is contact-dependent signalling?
Direct cell-to-cell signalling: cells in close contact - but not always adjacent -signalling molecules is membrane-bound to cell surface = not secreted -complementary receptor on surface of other cell -allows site specific binding and communication to occur i.e: antigen presenting - Diapedesis rolling through blood vessels
What is Secreted molecule signalling?
Cell-to-cell signalling via secreted molecules: -Molecule produced by one cell that acts on itself or on other cells -signalling molecules are small and structurally very diverse
What are molecules that are released locally and act upon itself?
Autocrine Cell-to-cell signalling - self inducing - only self cells NOT other cells of the same type
What are molecules that are released locally and act upon another cell close by?
Paracrine cell-to-cell signalling - neighbouring cells - often results in a signalling concentration gradient (acetyl choline)
What are molecules that are released locally and act upon a distant cell or tissue?
Endocrine cell-to-cell signalling - Hormones -Distributed in blood - need the correct receptor on other cell to work
What are the 4 types of endocrine molecules?
Hormones: - peptides and proteins: A.A - steroids: Cholesterol derived - amines: Tyrosine derivatives - eicosanoids: arachidonic acid derived (autocrine/paracrine)
What does the endocrine system normally control the activity for?
Activities that require duration rather than speed
What are Tropic or endocrine axis driven hormones?
A hormone that as its primary function regulates the hormone secretion of other endocrine glands - hypothalamus-pituitary axis and peripheral endocrine gland i.e: Thyroid
What are non-tropic or physiological response driven hormones?
A hormone that affects non-endocrine target tissues i.e: pancreatic islet cells that control blood glucose
What are classical hormones?
Insulin
Adrenalin
Thyroxine
What are neurohormones?
Oxytocin Antidiuretic hormone hyopthalamic releasing inhibiting hormones = released into blood from neurones but act like classical hormones
What are the three-tired response of the endocrine axis driven hormones?
- Hypothalamic releasing & inhibiting hormones 2. Production of tropic hormones in anterior pituitary 3. Production & secretion of hormones from peripheral glands
Where is the hypothalamus located?
- Functionally diverse region of the brain - located in the diencephalon below the thalamus and above the pituitary - composed of anatomically distinct nuclei = regulates autonomic nervous system -secretes hypothalamic hormones
What does the pituitary gland do?
- complex endocrine & neuroendocrine organ -located in the sella turcica at the base of the brain and inferior to the hypothalamus
What does the Anterior pituitary gland secrete?
Endocrine hormones
What does the posterior pituitary secrete?
Neuroendocrine hormones
What does the hypothalamus do?
Acts as integrating centre - key role in regulating pituitary function
how is the hypothalamus connected to the pituitary?
The infundibulum (pituitary stalk) = contains vascular and neural connections
How does the hypothalamus control the anterior pituitary?
Through inhibiting and releasing hormones - released into the hypothalamo-hypophyseal portal system
What is the posterior pituitary structure?
Long processes - made up of neural tissue - collection of axons with cell bodies lying in the hypothalamus = get into blood
What is the structure of the anterior pituitary?
Small body neurons from hypothalamus - need the hypothalamic-hypophysial portal vessel to connect to lobe - collection of endocrine cells
What does the Posterior pituitary gland synthesize?
Oxytocin (OCT) Anti-diuretic hormone (ADH)
Where are the neurohormones of the posterior pituitary stored?
In the nerve axon terminals - nerve impulse causes release into a plexus of blood capillaries
What controls the anterior pituitary?
The hypothalamus - direct vascular connection allows delivery of regulatory hormones directly to anterior pituitary without dilution in the systemic circulation
How many types of hormones do the 5 endocrine cells of the anterior pituitary secrete?
6: Thyroid stimulating hormone (TSH) Adrenocoticotropic hormone (ACTH) Prolactin (PRL) Luteinizing hormone (LH) Follicle stimulating hormone (FSH) Growth Hormone (GH)
What are the two classes of function hormones?
1: lipid soluble = transduction - steroids -thyroid hormones -nitric oxide 2: Water soluble = non-steroid hormone action - amines (other than thyroid hormone) - peptides & proteins - Eicosanoids
How does lipid soluble hormones enter the cell?
- diffuse through plasma membrane (except thyroid hormones) 2. bind to specific receptors in cytoplasms or nucleus 3. Hormone & receptor bind to DNA 4. Gene is transcribed or deactivated
How do water soluble hormones enter the cell?
- First messenger hormone binds to membrane receptor 2. activated receptor sets off cascade that activates an enzyme 3. enzyme reaction produces a second messenger (ie cAMP) 4. Second messenger produces a response in cell
What is the main take-away from this lecture?
