Endocrine+system

Hypothalamus- **section of brain that connects the nervous system with the endocrine system**. Pituitary gland- an endocrine gland which lies just below the hypothalamus in the brain. It consists of two lobes that both regulate hormones: Posterior Lobe: Produce protein hormones- transported through axon, and are released into the blood from the nerve endings. Anterior Lobe: hypothalamus produce hormones which are released in capillaries and carried through pituitary gland as a second filter.

 → Hormones- need to effect a change inside the cell two types: **Steroid Hormones: They are hydrophobic,** they move easily through the cell membrane, there they bind to receptors in the cytoplasm or nucleus. The hormone-receptor switches specific genes on or off directly. Protein Hormones: Poly peptide hormones also bind to receptors on cell surface membrane. The binding on the outside will cause change on the inside of the cell, this changes the concentration of the secondary messenger which will activate a specific enzyme.
 * Distinguish between the mode of action of steroid hormones and protein hormones. **

Kidneys maintain water potential in the mammal. Large amounts of water pass through the kidneys and are mostly reabsorbed into the blood. The amount reabsorbed is regulated by the hormone antidiuretic hormone, produced by the hypothalamus, and secreted from the posterior pituitary gland, because they are stored there.
 * Explain the control of ADH (vasopressin) secretion by negative feedback. **

 Hypothalamus contains osmoreceptors which detect concentration of dissolved particles in the blood plasma, when an increase is detected an impulse is sent down the axon and ADH will be released from its nerve end into the blood capillaries in the posterior lobe of the pituitary gland. ADH will travel to kidney in blood and make the walls and collecting ducts more permeable for reabsorption.


 * Compare the composition of saliva, gastric juice and pancreatic juice. **

 -saliva (from salivary glands) consists of: water, electrolytes, salivary amylase, mucus, lysozyme (which works as antibacterial fluid)  -gastric juice (from stomach) consists of: water, mucus, enzymes (pepsin, rennin), HCl  -pancreatic juice (from pancreas) consists of: water, bicarbonate, enzymes (amylase, lipase, carboxypeptidase, trypsinogen)

 -The initial release of gastric juice from the cells of duodenum as well in the part of stomach nearest to duodenum occurs under nerve stimulation after sight or smell of food.  -The sustained release occurs under the influence of gastrin secreted when food is in the stomach.W hen peptides are detected by stretch receptors, gastrin is released under stimulus from vagus nerve of parasympathetic nervous system, it stimulates acid production from parietal cells & pepsinogen from chief cells. When pH in stomach falls too low ,gastrin release is inhibited by hormones secretin & somatostatin.
 * Outline the control of digestive juice secretion by nerve and hormones, using the example of secretion of gastric juice. **

<span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> Some of the enzymes (like maltase, lactase and sucrase) are immobilized on the membranes of the intestinal epithelium cells. The active sites of the enzymes are oriented toward the lumen of the intestine. They remain functional even when epithelial cells have been sloughed off into the lumen
 * <span style="background-color: #ffffff; color: #444444; font-family: georgia,'times new roman',times,serif; font-size: 15px;">Outline the role of membrane-bound enzymes on the surface of epithelial cells in the small intestine in digestion. **

<span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> Human lack the digestive enzyme cellulase, the dietary cellulose remains undigested and is egested in the feces. In some animals the symbiotic relationship developed with cellulose-digesting bacteria.
 * <span style="background-color: #ffffff; color: #444444; font-family: georgia,'times new roman',times,serif; font-size: 15px;">Outline the reasons for cellulose not being digested in the alimentary canal. **

<span style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;"> → <span class="lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">-Pepsinogen and trypsinogen are inactive forms of enzymes. This is done to prevent self-digestion of the cells that produce those inactive enzymes (known as the zymogens). -Pepsinogen (in stomach) is converted into pepsin by the acidic conditions of the stomach. -Trypsinogen (in pancreas) is converted into trypsin by the action of enteropeptidase (the enzyme that is bound to the membranes of the small intestine).
 * <span class="qDef lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">Explain why pepsin and trypsin are initially synthesized as inactive precursors and how they are subsequently activated. **

<span style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">→ <span class="lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">Exocrine glands are responsible for the release of digestive fluids. Exocrine glands secrete into ducts. Exocrine gland has a duct portion and a glandular portion. At the end of each branch is an acinus formed at secretory cells of two types: serous cells (which secrete proteins such as enzymes), and mucous cells (which secrete mucus).
 * <span class="qDef lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">Explain the structural features of exocrine gland cells. **

<span style="background-color: #f4f0ea; color: #222222; display: block; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;"> → Villi - provide a huge surface area for absorption Epithelium cells - single layer of small cells, packed with mitochondria - the source of ATP (metabolic energy) for active uptake across the plasma membrane Mitochondria - these organelles are present in large numbers, suggesting a significant demand for ATP in these cells. Microvilli - these tiny, finger-like infoldings of the cell surface facing the lumen of the gut greatly increase the surface area in contact with material to be absorbed. Pump proteins in the plasma membrane of epithelium cells - actively transport nutrients across the plasma membrane into the villi Mucus from goblet cells in epithelium - lubricates movement of digested food among the villi and protects plasma membrane of epithelial cells Tight junctions - these bind together the individual epithelial cells, so that the only way into the tissues of the body is through the epithelium. Network of capillaries - large surface area for uptake of amino acids, monosaccharides, and fatty acids and glycerol into blood circulation Lacteal - branch of the lymphatic system into which triglycerides (combined with protein) pass for transport to body cells Pinocytotic vesicles - these are the site of pinocytosis by which fluid is taken up or released in tiny vesicles, across the plasma membrane of a cell.
 * Explain the structural features of an epithelial cell of a villus as seen in electron micrographs, including microvilli, mitochondria, pinocytotic vesicles, and tight junctions. **


 * <span style="background-color: #ffffff; color: #444444; font-family: georgia,'times new roman',times,serif; font-size: 15px;">Discuss the roles of gastric acid and Helicobacter pylori in the development of stomach ulcers and stomach cancers. **

<span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> -A stomach ulcer is an open sore in the stomach wall, where digestive juices - mostly acid and the enzyme pepsin - have begun to eat away the stomach lining.

<span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> -It is now recognized that about 80 per cent of ulcers are caused by infection from a bacterium called Helicobacter pylori (the remaining 20 per cent is caused by over-use of anti inflammatory drugs such as aspirin and ibuprofen).

<span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> -The corkscrew-shaped bacterium survives in the stomach by producing an enzyme called urease, which neutralizes stomach acid and allows the bacterium to colonize the stomach's mucous lining, opening up the stomach wall to attack form digestive fluids.

<span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> -The theory that ulcers was the consequence of an infection was put forward in the early 1980's by Barry Marshall and Robin Warren


 * <span style="background-color: #fffbc3; color: #444444; font-family: georgia,'times new roman',times,serif; font-size: 15px;">Explain the problem of lipid digestion n a hydrophilic medium and the role of bile in overcoming this. **

<span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> -Lipids tend to coalesce (lump together) and are only accessible to lipase at the lipid-water interface. <span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> -Bile molecules have a hydrophobic end and a hydrophilic end which emulsifies (prevents from coalescing) the lipids <span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> -Lipase must be water-soluble and has a hydrophobic active site (for its substrate, lipids) <span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> -The increased surface area allows lipase greater access to its substrate


 * <span style="background-color: #ffffff; color: #444444; font-family: georgia,'times new roman',times,serif; font-size: 15px;">Explain the mechanisms used by the ileum to absorb and transport food, including facilitated diffusion, active transport and endocytosis. **

<span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> **Facilitated diffusion.** Some substances need a little assistance to enter and exit cells. The transmembrane protein helps out by changing shape. <span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> **Active transport.** Some substances need a lot of assistance to enter cells. Similar to swimming upstream, energy is needed for the substance to penetrate against an unfavorable concentration gradient. <span style="background-color: #ffffff; font-family: georgia,'times new roman',times,serif; font-size: 15px;"> **Endocytosis.** Cells can use their cell membranes to engulf a particle and bring it inside the cell. The engulfing portion of the membrane separates from the cell wall and encases the particle in a vesicle. monoglyceries+Bile salts+ FAMicelles Diffuse across plasma membrane. Inside epithelial cell, reassemble & become coated with protein & cholestrol to form chylomicrons which are also known as lippoproteins. this can enter in lacteal.

<span style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">→ <span class="lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">When certain nutrients are in excess in the blood, hepatocytes absorb and store them, releasing them when they are at too low a level. For example, when the blood glucose level is too high, insulin stimulates hepatocytes to absorb glucose and convert it to glycogen for storage. When the blood glucose is too low, glucagon stimulates hepatocytes to break down glycogen and release glucose into the blood. Iron, retinol (vitamin A) and calciferol (vitamin D) are also stored in the liver.
 * <span class="qDef lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">Outline the role of the liver in the storage of nutrients, including carbohydrate, iron, vitamin A and vitamin D. **

<span style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">→ <span class="lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">The SA node is stimulated by two nerves: a sympathetic nerve that accelerates the heart, and the vagus nerve that restores the heartbeat to a homeostatic level (parasympathetic). It is located towards the top of the right atrium, so that the atria beat from the top down. The AV node receives the signal from the SA node and retards it a tenth of a second before firing, to allow the atria to finish contracting before ventricular systole begins. The impulse from the AV node travels down the common bundle, then is carried up the walls of the ventricles by Purkinje fibers. This ensures that the ventricles contract from the bottom up.
 * <span class="qDef lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">Outline the mechanisms that control the heartbeat, including the roles of the SA (sinoatrial) node, AV (atrioventricular) node and conducting fibers in the ventricular walls. **

<span style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">→ <span class="lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">Partial pressure- the pressure exerted by each component in a mixture. The pressure of a gas in a mixture is the same as the pressure it would exert if it occupied the same volume alone at the same temperature
 * <span class="qDef lang-en" style="background-color: #ffffff; color: #222222; font-family: 'lucida grande','lucida sans unicode',arial,sans-serif;">Define partial pressure. **

[|i-biology] [|Hormones] [|Mechanism of action of steroid hormone]

[|Mechanism of action of thyroxine] [|Control of thyroid gland]

[|Mechanism of action of epinephrine/ adrenaline hormone]

[|Assessment through Quizlet]