physiology test 2 Flashcards by Dana Langridge

what are phospholipids made of

diglyceride + phosphoric acid. Found in egg yolk

How well did you know this?

Not at all

Perfectly

what is the structure of sterols

contain four C rings. Mostly in animal tissues and egg yolk.

How well did you know this?

Not at all

Perfectly

how are dietary lipids generally digestion

Esterases cleave ester bonds
o Lipase
o Phospholipase (pancreas)
o Cholesterol esterase (pancreas)

How well did you know this?

Not at all

Perfectly

what are the 3 ways that fat is emulsified

force
emulsion
hydrolysis

How well did you know this?

Not at all

Perfectly

how is fat emulsified by force

chyme passing through pyloric sphincter physically breaking down fat droplets

How well did you know this?

Not at all

Perfectly

how is fat emulsified by emulsion

Bile acids synthesised by cholesterol in liver

Sterol ring is retained and OH groups added

Hydrophobic side chains replaced by group containing carb. Acid

Bile acids ionised to bile salts

How well did you know this?

Not at all

Perfectly

how is fat emulsified by hydrolysis

In intestinal lumen

Lingual lipase & Gastric lipase

Hydrolyses at sn-3

Directly absorbed into portal vein

Pancreatic lipase: hydrolysesTAG –> 2 diacylglycerols –> 2 monoacylglycerol

Colipase: Hydrophobic regions associate with lipid droplet.

How well did you know this?

Not at all

Perfectly

how are phospholipids digested

Phospholipase A2 from pancreas

Hydrolyse phospholipids

Produces lysophosphatidylcholine + FFA

How well did you know this?

Not at all

Perfectly

how are sterols digested

Free cholesterol DOESN’T need to be digested

Cholesterol ester needs breakdown (cholesterol ester hydrolase)

How well did you know this?

Not at all

Perfectly

list all the possible products of lipid digestion

Lyso-phosphatidylcholine

2-monoacylglycerol

Free cholesterol

Fatty acids

Phytosterols

Fat soluble vitamins

How well did you know this?

Not at all

Perfectly

describe the structure of the large intestine mucosa

2 muscle layers (circular and longitudinal)

Incomplete longitudinal muscle layer – forms bands

Has ‘pouches’ called haustra

Simple columnar epithelium cells

No folds

Straight, tubular crypt glands in cell wall

How well did you know this?

Not at all

Perfectly

list the 3 motility processes of the large intestine

haustral contractions

mass movements

defecation reflex

How well did you know this?

Not at all

Perfectly

describe the motility of the large intestine through haustral contractions

Basoelectrical rhythm by pacemaker cells, lower frequency

Alternating contraction/relaxation (flattening) of haustra pouch

Mixing contents back and forth (non propulsive)

Absorption and storage

Local control – intrinsic nerve plexuses mediate contractions

How well did you know this?

Not at all

Perfectly

describe the motility of the large intestine through mass movements

Contraction of large colon segments

Coordinated by ENS reflexes:
 Gastrocolic (stomach distension). Clears contents in prep for new meal
 Duodenocolic (duodenum stimuli e.g. chyme)

How well did you know this?

Not at all

Perfectly

describe the motility of the large intestine through the defecation reflex

Internal anal sphincter (smooth muscle) and external anal sphincter (external0

Rectal distention initiated reflex

Relaxation of both sphincters

Controlled by local (intrinsic/extrinsic NS) and parasympathetic reflexes (vagal nerves)

Conscious control: afferent input into cerebrum

How well did you know this?

Not at all

Perfectly

briefly explain constipation

Longer retention of contents –> excess water absorbed from faeces

Appendicitis may occurs with faecal obstruction
o Abdominal pain
o Inflammation
o Bacterial infection

How well did you know this?

Not at all

Perfectly

what are some things absorbed in the large instines

Study These Flashcards

Salt, water and electrolytes, short chain FA, vitamins

Na+ active absorbed (pump)

Cl- passive absorbed

Water osmosis

what are chylomicrons

Study These Flashcards

Long chain fatty acids packaged into chylomicrons in SI enterocytes

Enter circulation vis lymphatics

Lipid composition modified in circulation

Concentration of chylomicrons decreases after time after fat dense meal – due to lipoprotein lipase action (LPL)

what are the products of lipoprotein lipase (LPL) action

Study These Flashcards

hydrolyses TAG

Products taken up by adipocytes, myocytes, mammary gland epithelial cells (lactation)

Chylomicrons lose phospholipids, free cholesterol and apolipoproteins due to circulating HDL (now becomes chylomicrons remnants)

explain VLDL and LDL metabolism

Study These Flashcards

Secretin of VLDL:
o Contains Apo B100, cholesterol, cholesterol ester
o TAG

Once release into circulation, VLDL acquires other apolipoproteins from HDL

Hydrolysis in capillaries: FAs released from LPL action

In circulation for days, exchanges lipid component with other lipoproteins

LDL taken up by endocytosis

describe HDL metabolism

Study These Flashcards

Synthesised in liver as Apo A1

Acquires lecithin cholesterol acyl transferase in circulation – allows HDL to continue collecting cholesterol as it moves through tissues

HDL can counteract some atherosclerotic plaque through reverse cholesterol transport

HDL delivers cholesterol to liver – binds to SR-B1 on hepatocyte surface

Liver can maintain cholesterol homeostasis, and put cholesterol into bile (for elimination)

what are some interventions for high cholesterol levels

Study These Flashcards

Statins – make less cholesterol in liver

Cholestyramine – medication binds bile acids and prevents reabsorption

Ezetimibe – medication interferes with dietary cholesterol uptake from NPC1l1 transporter

Plant sterols – replaces cholesterols in mixed micelles and interferes with intestinal absorption

why does the liver need cholesterol

Study These Flashcards

Liver needs most cholesterol for bile production

Regulates intracellular cholesterol homeostasis in hepatocytes

what happens if cholesterol levels in the liver is too low

Study These Flashcards

LDL receptors on cell membrane can bring in cholesterol from circulation

Can make cholesterol from acetyl CoA

what happens if cholesterol levels in the liver is too high

Liver acts to decrease cholesterol

explain water movement

Transcellular mechanism – across cells via aquaporins Paracellular path – between cells via solute driven diffusion Water movement dependant on osmotic gradients Maintained by active solute transport. Standing gradient: o Sodium moves through enterocyte into lateral space (space between cells) o Creates high osmotic pressure in lateral space o Water then enters driven by high osmotic pressure o Osmotic pressure decreases, hydrostatic pressure increases o Water is flushed into capillaries

where is calcium stored

99% skeleton

list some dietary sources of calcium

* Nuts * Dairy * Broccoli * spinach * Baked beans and legumes * Dried figs

list some functions of calcium

o Muscle contraction o Nerve conductivity o Enzyme activation o Blood clotting o neurotransmitter secretion

how is calcium absorbed

Alimentary absorption (gut) or renal absorption (more effective) Obligatory loss of calcium through skin, sweat, faeces Insoluble calcium salts are solubilised in low pH – stomach SI has 2 transport mechanisms: o Transcellular. Carrier mediated active transport. 60% absorption. saturable o Paracellular absorption: passive diffusion. Non saturable. Jejunum and ileum

what are the transporters involved in calcium absorption

Calcium transporter 1 (CaT1). Moves Ca across brush border Calbindin. Systolic binding protein. Moves Ca through enterocyte Calcium ATP-ase pump

what are some factors affecting calcium absorption

1 – 24 dihydroxy vitamin D o Upregulates CaT1 and calbindin o Improved calcium absorption Rate of transit through intestine Life stages: o Infants, children, adolescences pregnant and lactation increases absorption o Decreased with age and lower oestrogen levels Diet o Protein and sugars, and vitamin D increase o Free fatty acids and fibre decrease

list some functions of iron

Haemoglobin synthesis and oxygen transport DNA synthesis Electron transport

how is iron absorbed

Transporters across luminal membrane from 2 active transporters: Haem via HAEM CARRIER PROTEIN 1(hydrolysed prior from proteases) Hydrolysed in cell to ferrous iron Non haem via DIVALENT METAL TRANSPORTER 1 Ferric iron concerted to ferrous iron at brush border from duodenal cytochrome b 2 fates after absorption: used immediately or absorbed

what is the fate of iron if it's needed for immediate use

ferroportin transports Fe2+ across basolateral membrane Fe2+ oxidised to Fe3+ Binds to transferrin for transport in blood

what is the fate of iron if it's needed for storage

Stored in epithelial cells as ferritin (short term) Excreted in faeces with epithelial turnover (3 days)

list some factors affecting iron absorption

Ascorbic acid (promotes) – converts ferric iron to ferrous iron and chelated iron in gut lumen Organic acids – citric acid enhances absorption Inhibited by polyphenols (vegetables, some grains, tannin in tea phytates

list some dietary sources of iodine

marine food eggs variety of meats grains and legumes Iodine: organic form, amino acid bound Iodide: free form. Mostly in thyroid gland, some circulating

list some functions of iodine

Key constituant of thyroid hormones Involved with thyroxine Essential for normal growth and development

what is the process of iodine absorption

Iodine releases and reduce to iodide before absorption Rapidly absorbed din stomach and duodenum Absorbed active transport at enterocyte apical surface by sodium-iodide transporter Exit across basolateral surface into bloodstream by chloride channel (CLC-2) Exit across basolateral surface into bloodstream by chloride channel (CLC-2) Thyroid follicular cells actively take up free iodide immediately from blood

what are the 3 states of energy balance

1. Constant body weight 2. Unused energy stored. 3. Body must use stored energy to supply needs

what are the 3 key nuclei involved in hypothalamic control of energy balance

o Arcuate nucleus o Lateral hypothalamic area o Paraventricular nucleus

physiology test 2 Flashcards

(42 cards)