BIO 251 exam 4

what are the major functions of the urinary system?

to regulate plasma: ionic composition, volume, osmolarity, pH and hormone secretion.

what are the major functional regions of uriniferous tubule?

1. nehprons- 2 parts

a. renal corpuscle (glomerulus and glomerular)

b. renal tubule

2. collecting ducts

what are glomeruli (glomerulus)?

twisted balls of blood capillaries, where plasma is filtered from blood and enters into tubule

what process (steps) occur in the glomeruli?

1. glomerular filtration- filtration of plasma from glomerulus into glomerular capsule

2. reabsorption- movement of substances from tubules back into blood (particular capillaries)

3. secretion- movement of substances from particular capillaries directly into tubules

4. excretion- from tubules out of body

how does the composition of glomerular filtrate differ from plasma?

filtrate has similar composition to plasma minus the plasma proteins 

what is meant by glomerular filtrate rate (GFR)?

the rate of filtration (125 mL/min or 180 L/day)

what two factors determine GFR?

1. BP in glomerular capillaries

2. osmotic force of plasma (bc of proteins)

does vasodilating afferent arterioles increase or decrease GFR?

dilating afferent arterioles increases BP in glomerulus and increases GFR (more fluid filtered)

How is GFR regulated?

tubuloglomerular feedback mechanism (local control)

What happens to GFR when there is a decrease in fluid in the kidney tubules?

vasodilating molecules released by tubule cells → dilate afferent arterioles → increase BP in arterioles and glomerulus and increase GFR (more fluid filtered)

what happens to GFR when there is an increase in fluid in the kidney tubules?

vascoconstricting molecules are released → constrict afferent arterioles → decrease BP in arterioles and glomerulus and decrease GFR (less filtered)

what are the primary substances absorbed in proximal convoluted tubule?

glucose, amino acids, sodium, calcium, urea, and water (65% water due to osmotic gradient produced by reabsorption of other substances)

what are the mechanisms of glucose and amino acid reabsorption in renal tubles?

1. glucose and amino acids are cotransported with sodium (secondary active transport) into PCT cells

2. these transporters can be saturated so that above a certain filtrate concentration, no further reabsorption occurs → remainder lost in urine

3. rate of transport when carrier proteins are saturated → transport max

what is Tmax?

rate of transport when carrier proteins are saturated

what happens when Tmax for glucose is exceeded?

during diabetes mellitus, plasma glucose exceeds Tmax, the extra amount will remain in PCT and excerted in Urine (makes urine sweet)

what are the primary substances absorbed by the descending loop of hence of the nephron?

water reabsorption, 15%

what are the primary substances absorbed by the thin ascending loop of hence of the nephron?

Na and Cl absorption, no water, passive sodium channels on tubule cells

what are the primary substances absorbed by the thick ascending loop of hence of nephron?

secondary active transport for Na, K and Cl → NK2C transporter → 1 Na, 1 K, 2 Cl

how does aldosterone increase the absorption of Na in distal convoluted tubule?

it increases the number of sodium channels and Na/K ATPase transporter pumps

where is aldosterone produced?

secreted by cells in adrenal gland cortex

list the conditions that lead to increased aldosterone secretion:

low BP → juxtaglomerular cells release Renin and activates RAAS and low sodium in DCT

how does anti-diuretic hormone (ADH/vasopressin) influence water reabsorption in collecting duct?

ADH inserts water channels (aquaporins) into membrane of collecting ducts. Without ADH, water can’t pass through cell membranes.

does ADH increase or decrease if there’s an increase in plasma volume?

ADH decreases when there is an increase in plasma volume, prevents body from retaining too much water.

does urine out put increase or decrease when ADH is secreted?

urine output decreases when ADH is secreted, ADH makes collecting ducts more permeable to water so more water is reabsorbed into blood

does blood volume increase or decrease after ADH secretion?

ADH makes the kidneys absorb more water from collecting ducts back into blood stream, more water returned means blood volume increase

what are the 4 major processes that occur in the digestive system?

motility, secretion, digestion, and absorption

what is the motility processes in digestive system?

contractions of smooth muscle in walls of digestive tract, mixing movements

what is the secretion processes in digestive system?

movement of substances into digestive tract lumen

what is the digestion processes in digestive system?

biochemically breakdown nutrients (carbs, fats and proteins) into smaller absorbable units (monosaccharides, fatty acids, amino acids)

what is the absorption processes in digestive system?

small absorbable units are transferred from digestive tract into blood or lymph

which stomach cells secrete hydrochloric acid (HCl)?

secreted by parietal cells. breaks down connective tissue and kill bacteria, doens’t biochemically break down nutrients. 

what is the mechanism (steps) of gastric (HCl) secretion?

1. starts with CO2

2. parietal cells produce acid

3. contains carbonic amydrase

4. active transport H into lumen of stomach in exchange for K

5. bicarbonate transported into inter intestinal fluid in exchange for Cl

6. Cl diffuses into lumen through channels

7. form HCl

what are the signals for HCl secretion in cephalic phase?

parasympathetic system (Ach), also stimulates gastrin (hormone) release

what are the signals for HCl secretion in gastric phase?

physical dissension, reflex pathway from proteins, peptides and amino acids trigger gastrin, HCl

what are the signals for HCl secretion in the intestinal phase?

entry of chyme increases acidity and signal release of cholecystokinin (CCK)

how is cholecystokinin (CCK) involved in regulating gastric acid secretion?

entry of chyme in small intestine increases acidity and fat content → signals CCK hormone secretion which inhibits gastric acid secretion in stomach

what cells secret pepsinogen?

parietal and chief cells

how is pepsinogen activated?

stimuli (food, smell, taste, chewing), parasympathetic stimulation, physical dissension of stomach, gastrin secretion

what is the function of pepsinogen?

activated into pepsin by HCl

what is the function of pepsin?

breaks proteins into smaller peptides, first step of protein digestion before small intestine

the majority of carb, fat and protein digestion occurs in what organ?

small intestine, absorption completed within first 20% of intestine

what are the primary digestive enzymes of the pancreas?

pancreatic amylase, trypsin, pancreatic lipase

what is the digestive enzyme pancreatic amylase?

salivary amylase, starch → maltose (disaccharide) → biochem digestion

what is the digestive enzyme trypsin?

proteins → amino acids and small peptides → biochem digestion

what is the digestive enzyme pancreatic lipase?

fat → monoglycerides and fatty acids → biochem digestion

what is the mechanism for absorption of polysaccharides (glucose specific)?

broken into monosaccharides → secondary active transport → uses Na gradient → enter cell with sodium

what is the mechanism for absorption of polysaccharides (fructose specific)?

facilitated diffusion across both membranes

what is the mechanism for absorption of amino acids?

secondary active transport with Na or H → could also be facilitated

what are the steps in digestion of triglycerides?

broken into monoglycerides and 2 fatty acids (the absorbable units)

what are the steps in absorption of monoglyccerides and fatty acids (from the broken triglyceride)?

simple diffusion into epithelial cell → enter smooth ER and reform triglycerides → enter Golgi and pack into chylomicrons

what are micelles?

some fatty acids and monoglycerides form small structures called micelles (polar region facing out).

how are omicrons formed in intestinal absorptive cells?

triglycerides enter Golgi to be packed into chlymicrons (triglycerides, proteins and cholesterol)

what are the major processes that occur in the large intestine?

concentrates waste into feces, absorption of most remaining water not absorbed by small intestine, stores feces until deification 

what stimulates testosterone secretion in males?

negative feedback loop: leydig cells stimulated by luteinizing hormone (LH) from anterior pituitary gland → secrete testosterone

what is the function of testosterone (before birth)?

development of male reproductive system

what is the function of testosterone (puberty)?

ensure maturation of male reproductive system and the development of secondary sex characteristics 

what are the 3 phases of male sex response?

erection, emission and ejaculation

what is the erection phase of the male sex response?

parasympathetic system, vasodilation by cyclic GMP, by mechanical stimulation of receptors in penis or activity in descending neural pathways from brain 

what is the emission phase of the male sex response?

mechanical stimulation, neural activity shifts from parasympathetic to sympathetic control, contractions of epididymis and vas defers move semen into urethra

what is the ejaculation phase of the male sex response?

movement of semen in urethra triggers reflexes in sympathetic and skeletal muscle, stimulates contractions of smooth muscle in urethra, produces propulsive movement of semen through urethra and out of body.

what are the two phases of ovarian cycle?

follicular phase and luteal phase

what is the follicular phase of the ovarian cycle?

a few dormant follicles begin to develop under influence of follicle stimulating hormone (FSH) from anterior pituitary. Oocyte grows, follicle supporting cells proliferate and become granuloma cells which form several layers around oocyte, luteinizing hormone (LH) also stimulates growth of follicles. (mensuration to ovulation, 14 days).

what is the luteal phase of ovarian cycle?

ruptured follicle becomes the gland corpus luteum, secretes estrogen and progesterone, both maintain the thickens highly vascularized endometrium of uterus. no fertilization means corpus luteum degenerates. (ovulation to menstruation, 14 days) 

what are the functions of FSH during follicular phase of ovarian cycle?

help donate follicles develop, stimulate granulose cells and thecal cells to secrete estrogen.

what are the functions of LH during follicular phase of ovarian cycle?

stimulates growth of follicle, stimulates secretion of estrogen, LH surge triggers ovulation

what is the function of estrogen during the proliferative phase of the uterine cycle?

rebuilds and prepares the uterine lining (endometrium) so its ready for fertilized egg or gets shed

what is the function of progesterone during the proliferative phase of the uterine cycle?

prepares and maintains the endometrium, prevents another ovulation, supports pregnancy 

in the ovary, what cells secrete estrogen?

granulose cells and thecal cells which are stimulated by LH and FSH from anterior pituitary 

what is the corpus luteum?

after ovulation, ruptured follicle becomes a gland. if fertilization doesn’t occur, then it degernates after 14 days, ends the luteal phase

what phase is the corpus luteum present?

luteal phase of the ovarian cycle

what does the corpus luteum secrete?

the hormone progesterone and estrogen to prepare endometrium for fertilized ovum

what are the two phases of the uterine cycle?

proliferative phase and secretory phase

what is the profliertaive phase of the uterine cycle?

endometrium rebuilds and thickens under the influence of estrogen

what is the secretory phase of the uterine cycle?

endometrium is thick, vascular and glandular for implantation (gland secretion of glycogen)

what is the endometrium?

inner lining of uterus that undergoes monthly cycle

what hormone influences the endometrium during during proliferative phase of uterine cycle?

estrogen leads to development of highly vascularized endometrium

what is the function of progesterone during pregnancy?

maintains highly vascularized endometrium and then maintain pregnancy 

what is the function of human chronic gonadotropinin?

HCG maintains function of corpus luteum in ovary, maintains secretion of progesterone and estrogen, secreted by the placenta

what is the function of oxytocin?

powerful stimulant for uterine contraction, at first by high estrogen blood levels, stretch receptors in cervix then signal hypothalamus and posterior pituitary to secret more oxytocin 

what is the mechanism (steps) of oxytocin secretion?

positive feedback loop: cervical stretching → more oxytocin → stronger contraction → more stretching and pressure on cervix → more oxytocin