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
