Cell signalling and hormones Flashcards
How can diurnal rhythms change?
Can gradually change in response to a change in lifestyle, such as when entering a different timezone or having night shifts
What are hormones?
Chemicals released by glands to elicit a response, enhancing or inhibiting cellular reactions
How is the endocrine and nervous systems related?
Operate in synchrony. Hormones act more slowly and have longer lasting effects (exception of adrenaline)
What is information processing?
Half of the largest families of proteins deal with information processing. Process from nervous stimulation to muscular contraction
What happens to a lipid insoluble molecule acting as a cell signal?
Forms a ligand-receptor complex and enters cell
What are intracellular receptors?
Lipid soluble hormones; intracellular receptor binding; steroid hormones; thyroid hormones; vitamin D3; vitamin A; oestrogens; androgens; e.g. glucocorticoids
What does the thyroid gland do?
Converts iodine to thyroid hormones, which are major metabolic hormones which all cells are dependent on
What are thyroid hormones?
Thyroxine (T4), and triiodothyronine (T3)
What are increased T3 and T4 associated with?
Increased oxidative substrate metabolism (mitochondrial enzyme activity)
What physiological changes occur with hyperthyroidism (opposite changes to hypothyroidism)?
Increased metabolic rate = heat intolerance, protein catabolism (= muscle breakdown). Increased heart rate
What do glucocorticoids do?
Affect mobilisation of GLUT-4 to cell membrane, increasing glucose uptake from blood; affect breakdown of proteins, producing free amino acids, to enable gluconeogenesis; block process of glycolysis when glycogen storage is too low
How does glucocorticoids initiate responses?
Diffuses through phospholipid membrane (as is lipid soluble); bind with receptor; cause cascade of enzymatic event or bind to DNA and cause gene transcription
What can cell signals be?
Hormones, chemical elements, light, heat, water
What can the purposes of cell signalling be?
Warn off pathogens and/or infections; alter/regulate metabolic processes; switch genes on/off; cell division, differentiation, adaptation
What are types of cell signalling?
Autocrine, paracrine, and endocrine
What are the differences between auto-, para-, and endocrine?
Autocrine signal same cell as released from (by cytokines); paracrine signal nearby cells (by cytokines); endocrine signal far away cells in a multi-cellular organism (by hormones)
What is signal transduction?
Cascade of events that mediates sensing and processing of signal (detect, reception, amplify, respond)
What are different responses created by cell signals?
Change metabolism of cell (enzymatic activity changed); change electrical charge across membrane (ion channel activity); change gene expression
What is universal to all receptors?
All are integral membrane proteins
What are secondary messengers, and examples?
Relay signal from receptor-ligand complexes; cAMP, cGMP, Ca, IP3, DAG
What are catecholamines?
Chemicals released from adrenal medulla and sympathetic nerve endings; augment sympathetic neural effects; PA directly governs the quantity of secretion
What are two catecholamines?
Adrenaline and noradrenaline
How does adrenaline affect CV system?
Increases CO; redistributes CO to muscular and hepatic circulation with only a small change in MAP
How does adrenaline affect substrate metabolism during exercise?
Increases liver glycogenolysis; stimulates gluconeogenesis in prolonged exercise
Where is cortisol released from?
Adrenal cortex
What is cortisol released in response to?
Physical or emotional stress
What are effects of cortisol?
Increases effectiveness of catecholamines; promotes carb, protein and fat catabolism (muscle pp breakdown = stimulation of aa’s for synth of glucose for gluconeogenesis); stimulated release of FAs from adipose
What are growth factors?
Developmental regulatory factors; regulate cell growth, division, differentiation, and apoptosis
What are DHEAs?
Precursors for sex hormones, so decrease with age; are released from adrenal gland
How are DHEAs affected by PA?
Increase with increased intensity of PA
How do kinases activate/inactivate proteins?
Transfer Pi to protein; Pi has -ve charge; changes conformation of protein; changes function of protein
What do tyrosine kinases do?
Phosphorylate tyrosine amino acid
How many genes code for tyrosine kinases?
> 200
How many tyrosine kinases are there?
> 90
What are responses/ receptors to tyrosine kinases?
Ras signal transduction pathway; PI3 kinase pathway; JAK/STAT protein receptors
Why is the PI3 kinase pathway important?
Important in insulin response; insulin attaches to receptor; receptor autophosphorylated on tyrosine; IRS attaches to receptor and is phosphorylated - GLUT4 via Ras; produces secondary messenger; glycogen synthase is activated
