Principles Flashcards
What is the nema of the mechanism that allows te heart to been rythmically in the absence of external stimuli?
Autorhythmicity
What does the sympathetic division do to heart rate?
It accelerates the heart rate
What receptors does noradrenaline act on?
B1 receptors
What does the paraympatheic division do to heart rate?
Stimulates the vagus nerve Xth cranial nerve and slows the heart rate
What receptors does acetylcholine act on?
Muscarinic Receptors
What is stroke volume modified by?
The autonomic nervous system
What law controls the stroke volume intrinsically?
The Frank starling Mechanism
What is metabolism?
All the chemical reactions that occur within the cells of the body
What is fuel metabolism (intermediary metabolism)
Reactions involving catabolism, anabolism and transformation of protein, carbohydrate (CHO) and fat
How is fuel metabolism regulated?
By hormones;
- insulin
- glucagon
- adrenaline
- growth hormone
Thyroid hormone regulates metabolic rate.
What hormones control plasma glucose?
- in the absorptive and post-absorptive states: insulin and glucagon (pancreas)
- in emergencies: adrenaline (adrenal gland)
- during starvation: cortisol (adrenal), growth hormone (pituitary)
what are the two kinds of glands in the pancreas?
- exocrine glands (Secrete digestive enzymes and 1.HCO3- into the intestinal lumen)
- Endocrine glands(Islets of Langerhans)
What kinds of secretory cells do islets contain?
- Alpha (a) cells (glucagon)
- Beta (b) cells (insulin, proinsulin, C peptide and amylin)
- Delta (d) cells (somatostatin)
- F cells (pancreatic polypetide – role, if any, in fuel metabolism is not clearly understood)
What is the function of insulin
Favours anabolism
Stimulates conversion of glucose into glycogen, fatty acids into triglycerides and amino acids into protein
Insulin is the hormone of the fed-state
what is the function of glucagon?
- favours catabolism
- stimulates conversion of glycogen into glucose and triglycerides into fatty acids
- glucagon is the hungry hormone
What is the role of insulin during feeding?
- beta cell secretes more insulin
- catabolism of endogenous fuel stores is inhibited
- CHO, lipid and AA uptake by specific insulin-sensitive tissues is stimulated
- insulin directs tissues to replenish fuel reserves
What is the role of insulin during fasting?
- beta cell secretes less insulin
- lipids are mobilised from adipose tissue
- amino acids (AAs) are mobilised from muscle and other tissues
- lipids and AAs provide fuel for oxidation and act as precursors for hepatic ketogenesis and gluconeogenesis respectively
What is the major regulator of insulin secretion?
Glucose
modest increases in plasma glucose promote marked increases in insulin secretion and marked increases in plasma insulin
What innervates an Islet?
both the sympathetic and parasympathetic divisions of the ANS
What does parasympathetic stimulation and sympathetic stimulation do to insulin secretion?
parasympathetic- stimulates insulin secretion during feeding
sympathetic- inhibits insulin secretion
What are the three identified peptides (incretins) which enhance insulin secretion?
- CCK (cholecystokinin)
- GLP-1 (glucagon-like intestinal peptide 1)
- GIP (gastric inhibitory peptide)
where are insulin incretins released from?
All 3 are released by cells in the GI tract in response to feeding and act in a feed-forward manner to prime the beta cells to secrete insulin