Endocrine, Digestive , Urinary Flashcards
What is the endocrine system, and how does it differ from the exocrine system
Endocrine system consists of glands that secrete hormones directly into the bloodstream to regulate bodily functions like metabolism, growth, reproduction
Exocrine system releases substances (digestive juices, sweat) through ducts to specific target areas
What are the main types of signalling in cellular communication
Direct communication- via gap junctions (eg cardiac muscle cells)
Autocrine signalling- cells target themselves (immune)
Paracrine signalling- targets nearby cells (neurotransmitters)
Endocrine signalling- hormones travel through bloodstream to distant cells
What are the key types of hormones and how do they act ?
Peptides- water soluble bind to surface receptors eg insulin
Amines- derived from amino acids eg adrenaline
Steroids- lipid soluble, bind to intracellular receptors
How are hormones levels regulated
Hormone concentration are controlled via feedback loops
Negative feedback- inhibits further hormone secretion when levels are adequate eg thyroid hormone.
Positive feedback- amplifies hormone release
Describe the hypothalamic-pituitary axis and its role in hormone regulation
The hypothalamus releases hormones to stimulate or inhibit the anterior pituitary
Anterior pituitary hormones (TSH, ACTH) act oni peripheral glands
Posterior pituitary stores and releases hypothalamic hormones (eg oxytocin, ADH)
How are hormones transported in the blood
Water-soluble hormones - dissolve in plasma
Lipid-soluble hormones: bind to plasma proteins for transport (eg steroids)
What is the endocrine axis and how does it function?
Sequential activation of glands:
Hypothalamic-pituitary-adrenal (HPA) axis for stress:
Hypothalamus releases CRG
Pituitary releases ACTH.
Why do hormones produce different effects on various target cells
Target cells may express receptors or intracellular signalling pathways
Example- Epinephrine causes vasodilation in skeletal muscle and vasoconstriction in gut.
What are main components of digestive system, and what are their functions?
Mouth- mechanical breakdown and saliva secretion
Stomach- protein digestion, mixing food into chyme.
Small intestines-digestion and nutrient absorption
Large intestines-water and electrolytes absorption
Pancreases (enzymes), liver (bile), gallbladder (bile storage)
What are the key exocrine secretions of the stomach and what are their roles
Mucus- protects stomach lining
HCl- activates pepsinogen, denatures proteins, antimicrobial
Intrinsic factor- aids
How is gastric secretion regulated
Stimulated by vagal nerve (ACh), gastrin (G cells) and histamine (ECL cells )
Inhibited by somatostatin (D cells) in response to pH.
How does the stomach produce HCl
Carbonic anyhydrase converts CO2 and H2O into H2CO3
H2CO3 dissociates into H+ and HCO3-
H+ is pumped into the stomach lumen via H+/K+ ATPase
Cl- follows passively to form HCl
What enzymes are involved in small intestine digestion
Pancreatic enzyme: amylase (carbohydrates), lipase (fats), trypsin (proteins)
Brush border enzymes : lactase, maltose, sucrase (carbohydrates) aminopeptidase (proteins)
What role does the gut microbiome play in digestion
Ferments indigestible carbohydrates
Produces short chain fatty acids
Synthesises vitamins
How do enteriemdocrine cells regulate digestion in the stomach
G cells: secrete gastrin, stimulating parietal and chief cells
EGL cells: secrete histamine to increase HCl
D cells: release somatosin providing negative feedback to inhibit HCl production
What are the main comments of the urinary system
Kidney- filter blood and form urine
Ureterus-transports urine to bladder
Bladder-stores urine
Urethra- excretes urine from body
What are the key structures of the nephron and what are their functions?
Glomerulus and bowman’s capsule: filtration
Proximal tubule: reabsorbs nutrients, electrolytes and water
Loop of henle: creates osmotic gradient
Distal convoluted tubule and collecting duct: water reabsorption regulated
How does the loop of henle establish a concentration gradient?
Countercurrent multiplication
Descending limb: permeable to water not solutes
Ascending limb: pump out NaCl, impermeable to water
Allows water reabsorbption in the collecting duct
What is the role of vasa recta in maintaining the osmotic gradient
Straight blood vessels that parallel the loop of henle
Countercurrent exchange prevents washing out of the gradient
Descending : gains salt and loses water
Ascending: gains water and loses salt
How does the RAAS regulate filteration and blood pressure
Low blood pressure triggers renin release from the kidney
Renin converts angiotensinogen (liver) to angiotensin I
ACE converts angiotensin I to angiotensin II
Vasoconstriction increases blood pressure
Stimulates aldosterone release, promoting Na+ and water reabsorption
Angiotensin II enhances ADH release, increasing water retention
What factors influence the glomerular filtration rate (GFR)
Hydrostatic pressure: drives filteration from globular capillaries
Oncotic pressure: opresses filterstion due to plasma proteins
Capsular pressure: resists filteration due to fluid in Gowan’s capsule
Auto regulation: maintains stable GFR through afferent arteriole
