Principles of cell communication

Question 1

What are the 3 principles of cell communication?

Answer 1

1. Cell communication 2. Receptors 3. Hormones

Question 2

What does cell communication involve?

Answer 2

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

Question 3

True or false: Signals cannot be received across the cell membrane in order for the cell to respond?

Answer 3

False - signals that cells receive MUST be transmitted across the cell membrane so that the cell can respond.

Question 4

Can all signalling molecules cross a cell membrane by themselves?

Answer 4

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.

Question 5

How do signals most often move through the cell?

Answer 5

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.

Question 6

How many signals can a cell receive at any given time?

Answer 6

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

Question 7

What do these combinations of signalling molecules regulate in the cell?

Answer 7

cell survival cell differentiation cell division cell death (apoptosis)

Question 8

What are the 7 different signalling molecules?

Answer 8

1. Hormonal 2. Electrical 3. External 4. Mechanical 5. Immunological 6. Metabolic 7. Dissolved gases

Question 9

What is the essential component of chemical communication?

Answer 9

Intracellular signalling proteins

Question 10

What are the main types of cell signalling?

Answer 10

1. Gap junctions 2. Cell-to-cell (direct) signalling 3. Cell-to-cell signalling via secreted molecules 4. External environmental factors 5. Mechanical

Question 11

What is the simplest type of cell signalling?

Answer 11

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)

Question 12

What is contact-dependent signalling?

Answer 12

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

Question 13

What is Secreted molecule signalling?

Answer 13

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

Question 14

What are molecules that are released locally and act upon itself?

Answer 14

Autocrine Cell-to-cell signalling - self inducing - only self cells NOT other cells of the same type

Question 15

What are molecules that are released locally and act upon another cell close by?

Answer 15

Paracrine cell-to-cell signalling - neighbouring cells - often results in a signalling concentration gradient (acetyl choline)

Question 16

What are molecules that are released locally and act upon a distant cell or tissue?

Answer 16

Endocrine cell-to-cell signalling - Hormones -Distributed in blood - need the correct receptor on other cell to work

Question 17

What are the 4 types of endocrine molecules?

Answer 17

Hormones: - peptides and proteins: A.A - steroids: Cholesterol derived - amines: Tyrosine derivatives - eicosanoids: arachidonic acid derived (autocrine/paracrine)

Question 18

What does the endocrine system normally control the activity for?

Answer 18

Activities that require duration rather than speed

Question 19

What are Tropic or endocrine axis driven hormones?

Answer 19

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

Question 20

What are non-tropic or physiological response driven hormones?

Answer 20

A hormone that affects non-endocrine target tissues i.e: pancreatic islet cells that control blood glucose

Question 21

What are classical hormones?

Answer 21

Insulin

Adrenalin

Thyroxine

Question 22

What are neurohormones?

Answer 22

Oxytocin Antidiuretic hormone hyopthalamic releasing inhibiting hormones = released into blood from neurones but act like classical hormones

Question 23

What are the three-tired response of the endocrine axis driven hormones?

Answer 23

1. Hypothalamic releasing & inhibiting hormones 2. Production of tropic hormones in anterior pituitary 3. Production & secretion of hormones from peripheral glands

Question 24

Where is the hypothalamus located?

Answer 24

• 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

Question 25

What does the pituitary gland do?

Answer 25

• complex endocrine & neuroendocrine organ -located in the sella turcica at the base of the brain and inferior to the hypothalamus

Question 26

What does the Anterior pituitary gland secrete?

Answer 26

Endocrine hormones

Question 27

What does the posterior pituitary secrete?

Answer 27

Neuroendocrine hormones

Question 28

What does the hypothalamus do?

Answer 28

Acts as integrating centre - key role in regulating pituitary function

Question 29

how is the hypothalamus connected to the pituitary?

Answer 29

The infundibulum (pituitary stalk) = contains vascular and neural connections

Question 30

How does the hypothalamus control the anterior pituitary?

Answer 30

Through inhibiting and releasing hormones - released into the hypothalamo-hypophyseal portal system

Question 31

What is the posterior pituitary structure?

Answer 31

Long processes - made up of neural tissue - collection of axons with cell bodies lying in the hypothalamus = get into blood

Question 32

What is the structure of the anterior pituitary?

Answer 32

Small body neurons from hypothalamus - need the hypothalamic-hypophysial portal vessel to connect to lobe - collection of endocrine cells

Question 33

What does the Posterior pituitary gland synthesize?

Answer 33

Oxytocin (OCT) Anti-diuretic hormone (ADH)

Question 34

Where are the neurohormones of the posterior pituitary stored?

Answer 34

In the nerve axon terminals - nerve impulse causes release into a plexus of blood capillaries

Question 35

What controls the anterior pituitary?

Answer 35

The hypothalamus - direct vascular connection allows delivery of regulatory hormones directly to anterior pituitary without dilution in the systemic circulation

Question 36

How many types of hormones do the 5 endocrine cells of the anterior pituitary secrete?

Answer 36

6: Thyroid stimulating hormone (TSH) Adrenocoticotropic hormone (ACTH) Prolactin (PRL) Luteinizing hormone (LH) Follicle stimulating hormone (FSH) Growth Hormone (GH)

Question 37

What are the two classes of function hormones?

Answer 37

1: lipid soluble = transduction - steroids -thyroid hormones -nitric oxide 2: Water soluble = non-steroid hormone action - amines (other than thyroid hormone) - peptides & proteins - Eicosanoids

Question 38

How does lipid soluble hormones enter the cell?

Answer 38

1. 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

Question 39

How do water soluble hormones enter the cell?

Answer 39

1. 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

Question 40

What is the main take-away from this lecture?

Answer 40