Homeostasis and metabolism Flashcards
What is autocrine communication? What is paracrine communication?
A chemical is released from a cell into the extracellular fluid and then acts upon the very cell that secreted it.
Chemical messengers involved in the communication between cells, released into extracellular fluid travels short distances. e.g. ACh at neuromuscular junction
What is endocrine communication? What is exocrine communication?
Hormones produced and secreted, communication between cells travel further long distance, systemic effects.
Secretion into ducts then into organ
Organs involved in endocrine communication and hormones produced by each ?
Hypothalamus e.g. dopamine
Pituitary- anterior pituitary hormones= FSH, LH and TSH, posterior pituitary hormones= oxytocin, ADH/ vasopressin
Thyroid, parathyroid, adrenals, pancreas, ovaries and testes.
Key differences between endocrine and paracrine communication?
Hormones travel in blood in endocrine- only in extracellular fluid in paracrine messengers. Endocrine= affects more things and travels further than paracrine.
E.g.s of positive feedback loop? E.g.s of negative feedback loop?
Clotting cascade and oxytocin release during childbirth.
Blood sugar regulation, temperature regulation, blood pressure regulation, thyroid regulation
If too much thyroxine in blood, stimulates pituitary gland to stop producing TSH
Problems with feedback?
Can get primary hypothyroidism- thyroid produces too little thyroxine- TSH levels in blood keep increasing.
Can get primary hyperthyroidism- too much thyroxine, TSH falls but thyroxine rises.
What does primary and secondary mean in relation to feedback issues?
Primary= issues with endocrine gland, secondary= issue with pituitary or hypothalamus
Three hormone types? Classified according to what?
Peptide, steroid and amino- acid derivative
Structure
What is the structure of peptide hormones? How are they made and what do they bind to? Receptor binding induces what? E.g.s?
From short chain amino acids– small proteins, some have carb portions. Are large hydrophilic charged molecules that cannot diffuse across a membrane
To receptors on membranes- are pre-made and stored in cell then released and dissolved in blood
Signal transduction cascade
Insulin, TSH and ADH
Steroid hormones made from what? Solubility? Targets what? How made and transported? Response speed? E.g.s?
From cholesterol. Lipid soluble. Requires transport proteins in blood and targets intracellular receptor. Made by cell and diffuses out- binds to receptor inside cell.
Slow response as directly affects DNA e.g. testosterone, oestrogen and cortisol
Amino acid hormones made from what? Acts in same way as what other hormone type? Examples?
Tyrosine. Peptide hormone.
Adrenaline, thyroid hormones thyroxine (T4) and triiodothyronine (T3)
Predominant electrolyte in intracellular fluid? Predominant in extracellular fluid?
Potassium
Sodium, chloride, bicarbonate and Ca2+ ions- especially in heart and muscle
Where is interstitial fluid found? What is plasma?
Surrounding the cells but does not circulate. Circulates as the extracellular component of blood- interstitial= also extracellular component.
What is transcellular fluid? % of body weight is made of water? % of extracellular and intracellular fluid?
Makes up the CSF, digestive juices and mucus etc.
42L (60%)
Intra= 40% and extra= 20%
What are insensible water loss examples? What is osmolality? What is osmolarity?
Sweat, breath, vomiting and faeces.
Measure of number of dissolved particles per kg of fluid
Measure of number of dissolved per L of fluid
What is osmotic pressure? What is oncotic pressure?
Pressure applied to a solution by a pure solvent required to prevent inward osmosis through a semipermeable membrane.
Form of osmotic pressure exerted by protein that tends to pull fluid into its solution- water from interstitial fluid into plasma
What is hydrostatic pressure?
Pressure difference between capillary blood plasma and interstitial fluid- water and solutes move from plasma into interstitial fluid.
What happens when water is lost from ECF? Change detected by what? What is released?
Increase in solutes/ increase in osmolality
Osmoreceptors in hypothalamus
ADH from posterior pituitary to increase absorption in collecting ducts- more aquaporins in cell membrane
What else does ADH do?
Constricts the arterioles in the peripheral circulation which reduces the flow of blood to the extremities and this increases blood supply to core of body.
What happens when there is a decrease in water in ECF? Decreased renal blood flow leads to release of what?
Decrease in effective circulating volume– decrease in renal blood flow.
Renin from juxtaglomerular kidney cells in kidneys.
Renin converts angiotensinogen into what? Angiotensin I turned into what using what enzyme?
Angiotensin I
Angiotensin II using ACE enzyme- found on luminal surface of capillary of capillary endothelial cells of lungs
Angiotensin II stimulates the secretion of what hormone? This is produced where and does what? What does blood pressure do?
Aldosterone and ADH
From adrenal cortex- more aquaporins so more Na+ and H2O reabsorption.
Increases because arterioles constrict.
What cells in walls of ascending loop of Henle are stimulated by high osmolarity? They stimulate what? How is sensation of thirst created?
Macula densa cells
Juxtaglomerular apparatus to release renin into bloodstream
Angiotensin II acts on hypothalamus to cause sensation of thirst.
3 types of dehydration? Causes?
Hypotonic- electrolyte loss, hypertonic- water loss and isotonic- equal loss of water and electrolytes.
Water deprivation, diarrhoea, vomiting, burns, heavy sweating, diabetes insipidus, diabetes mellitus and drugs
Consequences of dehydration? Consequences of water excess?
Thirst, dry mouth, inelastic skin, sunken eyes, raised haematocrit, weight loss, confusion, hypotension
Hyponatraemia, cerebral over-perfusion– headaches, confusion and convulsions
What is serous effusion? What is oedema?
Excess water in a body cavity
Excess water in the intercellular tissue space
Types of oedema?
Inflammatory- proteins leak out, venous- increased venous pressure/ obstruction due to thrombus, lymphatic- obstructions and hypoalbuminaemic- lower oncotic pressure.
Why does pleural effusion happen and consist of?
Disruption of balance between hydrostatic and oncotic forces in visceral and parietal pleural vessels
Different fluids can enter pleural cavity
What is transudate? What is exudate?
Fluid pushed through capillary due to high pressure within capillary
Fluid that leaks around the cells of the capillaries caused by inflammation and increased permeability of pleural capillaries to proteins.
Capillaries= within visceral and parietal pleurae.
Protein level in exudates compared to transudates?
Exudates= high protein level compared to transudates.
Consequences of hypernatraemia?
Cerebral intracellular dehydration- dehydrates brain as H2) leaves ICF to become ECF
Consequences of hyponatraemia? Potassium excretion controlled by what hormone?
Intracellular over hydration- hypotension since H2O goes intracellular
Aldosterone as it controls the Na/K pump
Consequences of hyperkalaemia?
Risk of MI- messes with resting potential generated in heart for heart contraction
Consequences of hypokalaemia?
Weakness and cardiac dysrhythmia- abnormal heart beat
Causes of hypercalcaemia? Can lead to?
Primary hyperparathyroidism (too much parathyroid hormone so calcium leached from bones), skeletal metastases, vitamin D toxicity and TB Metastatic calcification and kidney stones
Causes of hypocalcaemia? Can lead to what?
Vitamin D deficiency, magnesium deficiency, renal disease, parathyroidectomy, intestinal malabsorption.
Tetany- spasms of voice box, hands and feet
All lipids in cell membranes have what feature? Functions of cell membrane? What hormone type binds to receptors?
They are amphipathic
Selective barrier, barrier to outside environment and compartmentalise cells
Peptide hormones
Cell membranes have molecules on them for what? Types of junctions between cells?
Intercellular adhesion and acts as an insulator i.e. myelin sheath
Occluding, anchoring and communicating
Features of occluding junctions? What filament type is involved in anchoring junctions?
Helps seal cells together in epithelial sheet to prevent leakage of molecules between them
Actin filaments- adherent junction joins actin bundle in one cell to a similar bundle in another cell= helps keep cells together.
What filament type enables cell to cell adhesion through desmosomes? What 2 things resist shearing forces and join intermediate filaments in one cell to those in a neighbour?
Intermediate filaments
Cell surface adhesion proteins and intracellular keratin cytoskeletal filaments
What junction type enables cell to matrix adhesion? What do hemidesmosomes do? What do communicating gap junctions allow the passage of?
Focal adherent junctions
They anchor intermediate filaments in a cell to the basal lamina.
Small water-soluble ions and molecules.
What is endocytosis? Occurs in what cell types?
Energetic process to engulf molecules into a cell- portion of membrane is invaginated to form a membrane bound vesicle= endosome.
Neutrophils and macrophages
What is pinocytosis? Where does receptor mediated endocytosis occur? How does this work?
Bringing in dissolved solutes.
Specific, found in depressed areas (coated pits)- allows cell to get molecules it needs.
Ligands bind to receptor- ligand released into cytosol
What is exocytosis?
Vesicle from Golgi apparatus, fuse with plasma cell membrane- waste expulsion/ enzyme/ hormone is secreted.
What is facilitated diffusion? What things do receptors do?
Solutes move from region of high concentration to region of low concentration through protein channels without carrier proteins. e.g. glucose.
Open a channel, activate an intracellular enzyme, induce second messenger (peptide hormone binds to receptor) and migrate nucleus to receptor-ligand complex.
Example of an enzyme linked receptor? What are ion channel linked receptor involved in?
Tyrosine kinase- transfers a phosphate group from ATP to a protein in a cell thus acting like an on/ off switch
In rapid signalling events found in electrically active cells like neurons i.e. ligand gated ion channels
What do G-protein coupled receptors do?
Sense molecules outside the cell and activate inside signal transduction pathways to ultimately illicit a cellular response.
Energy giving most energy per gram? What is the basal metabolic rate?
Lipid- 9kcal/g
Amount of energy needed to keep the body alive in the rest state= 1kcal/kg body mass/hr (24kcal/kg/day), an adult requires approx 0.8g/kg ideal body weight protein per day
Factors that increase BMR? Factors that decrease BMR?
High BMI, hyperthyroidism, low ambient temperature, fever/ infection, pregnancy and exercise
Age, gender(female have lower,) starvation and hypothyroidism
What is the daily energy expenditure(DEE)?
Energy needed to support our BMR and our physical activity and energy required to process food we eat.
Mass of excess energy stored as triglycerides? Mass of excess energy stored as glycogen? Stored as protein? Carbs account for what % of ATP production at rest? Lipids account for what %? When are proteins often used for?
15kg 200g in liver and 150g in muscle 6kg 30% 70% Longer periods of starvation
