BIO305 Final Notes PDF

Reproduction: Reproduction is NOT necessary for an individual - It IS necessary for the species **only body system not regulated by homeostasis ** Primary reproductive organs: 1. Gonads (testes and ovaries) a. Produce reproductive cells = gametes(sperm, ova) b. Secrete sex...

Reproduction: Reproduction is NOT necessary for an individual - It IS necessary for the species **only body system not regulated by homeostasis ** Primary reproductive organs: 1. Gonads (testes and ovaries) a. Produce reproductive cells = gametes(sperm, ova) b. Secrete sex hormones(testosterone, estrogens, progesterone) Accessory reproductive organs: 1. Duct system that sperm and ova travel through 2. Glands lining the ducts How is reproduction controlled? A 3-hormone chain 1. GnRH (hypothalamus -> hypothalamo-pituitary portal vessels) 2. FSH and LH (anterior pituitary) 3. Sex hormones (gonads) 4. Then the reproductive tract and other organs Male reproductive system: Primary structures = paired testes Accessory structures: epididymis, vas deferens, prostate gland, seminal vesicles, bulbourethral glands *sperm is composed of spermatozoa and fluids from the testes, epididymis, seminal vesicles, bulbourethral and prostate glands Spermatozoa release is stimulated by FSH Prostate gland: convergence of During ejaculation: testis->epididymis->vas deferens->ejaculatory duct->urethra Where do sperm come from? spermatogenesis-> sperm formation - Sites of spermatogenesis are Seminiferous tubules - Seminiferous tubules form the rete testis - Lumen contains mature sperm - In response to follicle stimulating hormone(FSH) and testosterone, the sertoli cells support spermatogenesis Spermatogenesis: along sertoli cells Sertoli cells: stimulated by FSH to increase Spermatogenesis **in the seminiferous tubules, the site of sperm production - From basement membrane to lumen - tight junctions- 2 compartments - Ring forms the blood-testis barrier, which prevents the movement of chemicals and antibodies from the blood into the lumen of seminiferous tubule and helps retain luminal fluid - Primary spermatocytes in basal compartment - Central compartment: rest of divisions and differentiation - Nutrients, chemical messenger -> stimulate proliferation, differentiation How is male reproductive function regulated? 1. GnRH secreted pulses 2. FSH and LH secreted from same cell type, stimulate distinct targets 3. Testosterone from Leydig cells necessary for spermatogenesis **negative feedback maintains sperm generation at a constant rate ** - Little change day to day Leydig cells: synthesis and release of testosterone - Also produce androgens - secretion is stimulated by LH What else does testosterone do? 1. Required for initiation and maintenance of spermatogenesis(acts via sertoli cells) 2. Decreases GnRH secretion via an action on the hypothalamus 3. Inhibits LH secretion via a direct action on the anterior pituitary gland Female reproductive system: Primary reproductive organ: Ovary Accessory: fallopian tubes, uterus, cervix, vagina Ovaries are responsible for: 1. Production of gametes 2. Development of mature gametes 3. Expulsion of mature eggs  4. Hormone secretion Where do eggs come from? Females are born with all of the eggs they will ever have! - Granulosa cells - Zona pellucida - Theca - Antrum - Several primordial follicles begin to mature each month, one becomes dominant - Probably due to local estrogen; may explain multiple births in fertility treatments - Non-dominant follicles undergo apoptosis (atresia) - These follicles did not fully mature - 99.99% of follicles undergo atresia - Cumulus oophorus - oocyte/cumulus float free What happens to the follicle? 1. Granulosa cells get big 2. Gland like structure 3. Secretes estrogen, progesterone and inhibin 4. If no fertilization -> corpus luteum -> apoptosis -> menstruation Phases of the menstrual cycle: in the ovaries** estrogen - granulosa cells estrogen corpus luteum Progesterone- granulosa progesterone-corpus luteum + Theca cells Progesterone and theca cells become the corpus luteum LH stimulates theca cells to produce androgen which is converted to estrogen in granulosa cells by the enzyme aromatase How is menstruation controlled? 1. GnRH secreted pulses 2. FSH and LH secreted from same cell type, stimulate distinct targets 3. Gonads secrete estrogen and progesterone a. Gametogenesis b. Both provide negative feedback to hypothalamus and anterior pituitary Hormonal control of menstrual cycle: Small increases in secretion of LH and FSH lead to follicular maturation, including an increase in the synthesis and secretion of ovarian estrogen Ovulation is produced by a surge in LH and marks the transition to the luteal phase of the cycle(ovulation) Plasma gonadotropin concentrations: 1. FSH and LH secretion increase because plasma estrogen concentrations is low and exerting little negative feedback 2. FSH secretion and plasma FSH decrease, causing atresia of non dominant follicles 3. LH surge is triggered 4. FSH and LH secretion are inhibited and their plasma concentrations decrease 2 stage model of estrogen synthesis: androgen precursors are synthesized in the outer layer(theca cells) and diffuse to the inner layer(granulosa cells) for conversion to estrogens LH drives the former and FSH drives the latter Week 2 of the menstrual cycle: decreasing FSH-> follicles degenerate What keeps dominant follicles going? Its granulosa cells have more FSH receptors - Also gains LH receptors Dominant follicle secretes estrogen estrogen(low) -> negative feedback on LSH and FH - FSH decreases more than LH ** compare this to the sertoli and leydig cells in males ** Hormonal control: early/mid follicular phase - Granulosa cells producing estrogen with help of theca cells - Estrogen feedback inhibition (low estrogen) - Inhibin mainly provides negative feedback to FSH on the pituitary gland The ovarian cycle of steroid production drives changes that characterize the menstrual cycle - Follicular phase is marked by increasing levels of estrogens whereas the luteal phase is marked by increased progesterone plus estrogen Late follicular phase: The “LH surge” - Feedback relationship between ovarian steroid hormones and secretion from the hypothalamus/anterior pituitary gland reverses in mid-cycle, eliciting the large ovulatory surge in LH Luteal phase: LH remains sufficient to support corpus luteum for ~ weeks - High levels of progesterone prevent LH surge even when estrogen is high - A decrease in LH leads to death of the corpus luteum, then estrogen and progesterone levels fall-> inhibits release of gonadotropins - Releases inhibition of anterior pituitary and FSH & LH increase, beginning a new cycle Switch in feedback regulation: switch from negative to positive feedback necessary for ovulation - Increases GnRH and LH - FSH is increased also but has no known physiological effect LH causes sudden increase in antrum fluid; stimulates enzymes to break down membranes of follicle and ovary What is ovulation? The walls of the ovarian follicle rupture and the secondary oocyte surrounded by the zona pellucida and cumulus is carried out of the antrum - The remnant of the ruptured follicle is transformed into the corpus luteum All eggs are born at once: - At birth the ovaries contain all of the eggs they will ever have (2-4 mil)  - Eggs are contained in follicles in the ovary - Only ~400 will be ovulated - Eggs ovulated at 40-50 are 30-40 years older than eggs ovulated at puberty: increased chromosomal abnormalities might be due to aging of eggs Uterus: Proliferative phase: increasing estrogen -> growth of endometrium plus underlying uterine smooth muscle(myometrium) - Increase in blood vessels - Increased synthesis of progesterone receptors in endometrial cells Secretory phase: progesterone acts on estrogen primed endometrium to convert it to endocrine tissue - Endometrial glands become coiled, filled with glycogen, more blood vessels and enzymes - Necessary for embryo to implant and for nourishment - Progesterone needs to stay high throughout pregnancy to prevent uterine contractions Menstrual phase: decrease in progesterone and estrogen(due to degeneration of corpus luteum)-> degeneration of endometrium - Constriction of blood vessels - Contractions of uterine smooth muscle - Mediated by prostaglandins produced by endometrium when progesterone and estrogen decrease - After vasoconstriction, vasodilation occurs -> hemorrhage What if the egg is fertilized? The human gonadotropin hormone(hCG) hormone rescues the corpus luteum - hCG is what shows a positive pregnancy test Hormone regulation: - Chorionic gonadotropin from trophoblasts (zygote) - Maintains the corpus luteum and high levels of estrogen and - When CG falls, placental secretion(trophoblast cells) takes over from the degenerating corpus luteum - Corpus luteum gone after 3 months Parturition: stretch receptors -> hypothalamus - Oxytocin- stim myometrium to contact and release prostaglandins - Local feedback!! Corpus luteum secretes: estrogen, progesterone and inhibin Renal system: Intake and excretion from kidneys must be equal Urinary system: Paired kidneys filter blood and produce urine The bladder receives urine to excrete via the bladder Urine eliminated via urethra Kidney: Main functions: regulation of H2O, inorganic ions, acid-base balance, removal of waste from blood and excretion in urine, gluconeogenesis, production of hormones/enzymes Renal cortex- outer layer with nephron(repeating units) Renal medulla- inner layer with loops where filtration/secretion/absorption occurs Renal pelvis- collection of urine Nephrons: 1 mil in each kidney **functional unit of kidney 1. renal corpuscle- knot of capillaries, fluid from blood enter into tube, travel through all parts and is collected at end a. blood plasma->filtrate(fluid inside) b. Proximal convoluted tubule-> loop of henle(has ascending and descending end)-> distal convoluted tubule -> collecting ducts c. Glomerular capillaries d. Bowman's capsule- space between capsule and capillaries e. Collecting duct- collecting urine/filtrate from multiple nephrons Juxtamedullary nephrons: 15% - Long loops of henle that penetrate deep into the medulla and are responsible for generating an osmotic gradient in the medulla - reabsorption of water in medulla - The efferent arterioles of these nephrons give rise to long looping capillaries called vasa recta - Renal corpuscle lies in the part of the cortex closest to the cortical-medullary junction Cortical nephrons: 85% - Short or no loops of henle - reabsorption and secretion in cortex - The efferent arterioles of these nephrons give rise to peritubular capillarie Nephron-renal corpuscle: 3 layers filter plasma: 1. Endothelial cells (fenestrae) 2. Basement membrane 3. Podocytes (foot processes) - Substances in blood are filtered through capillary pores between endothelial cells(single layer). Filtrate then  passes across the basement membrane and through a filtration slit between the foot process(pedicels) and enters the capsular space. From here the filtrate is transported to the lumen of the proximal convoluted tubule Two arterioles! Afferent arterioles: how blood enters the glomerular capillaries Efferent arterioles: blood leaving the glomerular capillaries after filtration has occurred Bowman's space: fluid passes through between glomerular capillaries and proximal tubules Basolateral vs apical membrane: Peritubular capillaries: - The part of each tubule in the cortex surrounded by capillaries - Supply tubules with blood and then join to form veins by which blood leaves the kidney - Are efferent arterioles that left the glomerulus and branched - Receive substances reabsorbed from the renal tubules - The 2nd set of capillaries encountered by blood flowing through the kidney Filtration, secretion, and reabsorption: 1. Glomerular filtration: fluid and solutes from capillaries into bowman's space 2. Tubular secretion: solutes from peritubular capillaries into tubular lumen 3. Tubular reabsorption: solutes from tubular lumen into peritubular capillary plasma 4. Metabolism by the tubular cells: renal tubular cells remove substances from the blood or filtrate and metabolize them a. exL NH4+, H+ and HCO- Filtration of materials from the blood into bowmans is favored by the high hydrostatic pressure of the glomerular capillaries - High PGC-> favors fluid movement out of glomerular capillaries and into bowman's space - Bowman's space exerts a hydrostatic pressure that opposes filtration - Osmotic force in bowman's space is 0  - H2O of plasma is less than bowmans -> favors fluid movement by osmosis into bowmans (*opposes glomerular filtration) **homeostatic regulation** Amount excreted = amount filtered + amount secreted - amount reabsorbed Refresher on forces driving bulk flow: Bulk flow in renal corpuscle: Formation of glomerular filtrate is the outcome of opposing pressures: - hydrostatic pressure favors filtration (Pgc) - Osmotic pressure of the glomerulus(Pigc) and hydrostatic pressure(Pbs) of the filtrate that oppose it Glomerular filtration rate: volume of fluid filtered from the glomerulus into bowman's space per unit of time depends on: 1. Net filtration pressure 2. Permeability of capillaries 3. Surface area 180L per day Systemic circulation -> 4-5L(ALL blood filtered 36-45 times per day) Tubular reabsorption: - Simple diffusion (lipid soluble) or facilitated diffusion - Active transport - Coupled to Na+ Secretion has a higher energy cost Mediated transport: 1. Solute binds to specific site 2. Conformational change 3. Dissociation on other side Micturition: Major function of kidneys is to rid of waste -> excreted in urine Micturition: release of urine from the bladder that is coordinated by a mix of smooth and skeletal muscle contraction/relaxation - Voluntary control - Sacral region of the spinal cord The bladder is a balloonlike chamber with walls of smooth muscle called the detrusor muscle - Contraction produces urination - Urethra begins function at the internal urethral sphincter - External urethral sphincter: below internal, ring of skeletal muscle that surrounds the urethra - Contraction can prevent urination even when the detrusor contracts strongly Spinal reflex component of Micturition: 1. As bladder fills the pressure increases which stimulates stretch receptors in the bladder wall 2. The afferent neurons from these receptors enter the spinal cord and stimulate parasympathetic neurons, which cause the detrusor muscles to contract  3. The contraction of the detrusor muscle causes the bladder to change shape and pull open the internal urethral sphincter. At the same time afferent input from the stretch receptors inhibits the sympathetic neurons to the internal urethral sphincter, opening it even further 4. Afferent input also inhibits somatic motor neurons to the external urethral sphincter, causing it to relax 5. Both sphincters are now open and the contraction of the detrusor muscles can produce urination Water and ion balance: Na and H2O balance is maintained by urine *need aquaporins(channels) to move H2O w osmotic pressure - Urine must be either hypoosmotic or hyperosmotic for H2O movement to occur Regulation of absorption/secretion: - To get rid of waste GFR very high - Need to reabsorb lots of water and solutes, they end up in filtrate - Mostly in proximal tubule - Most secretion here too - Also loop of henle(abs and secr) - Homeostasis regulation in collecting duct AND distal convoluted tubule - Distal segments: fine tuning Reabsorption of sodium and water: WATER FOLLOWS SALT - Sodium reabsorption energy intensive - Water reabsorption through passive diffusion - Depends on sodium movement - Sodium reabsorption in the proximal tubule: The membrane leading to blood: always sodium ATPase High water permeability, lots of aquaporins  - Sodium reabsorption in the collecting duct: Na/K flow is consistent Coupling of water and sodium reabsorption: - Osmotic gradient due to Na - Water permeability: Osmolarity decreases because loss of non-penetrating solutes -> Concentration of H2O increases Regulation of H2O permeability: 2 hormones: 1. Oxytocin 2. vasopressin/ADH(get rid less water) + high water permeability a. **adds aquaporins to membranes(which increases permeability for H2O) b. End results: the vesicles with the aquaporin channels fuse w luminal membrane and aquaporins are inserted into tube c. Vasopressin is metabotropic-> ligand gated - Ridding of less water in urine-> Water permeability in the collecting duct is high -> decrease the water being eliminated from body - body reabsorbs more water - Moe concentrated urine Varying urine concentration: 1. By blocking water exit from tubule(reducing permeability to H2O) urine will be more dilute a. Water stays in filtrate and is excreted 2. High H2O permeability needed for concentrating urine, but the osmotic equilibrium will only allow H2O mvmt out of filtrate in prop to Na mvmt Urine concentration must be higher osmotic than blood  - Only way H2O will flow out Renal countercurrent multiplier system: 1. Filtrate flow in ascending and descending sections of loop are in opposite directions(counter-current) a. Interstitial fluid is hyperosmotic (higher solute concentration than blood)-> important so we can create concentrated urine b. Na/H2O 2. Established by the juxtamedullary nephrons 3. Permeability to sodium and water differs 4. Generates an osmotic gradient in renal medulla-> increases from the cortex into the renal medulla Renal countercurrent multiplier system: **difference- the descending limb is permeable to H2O while the ascending is permeable to sodium and chloride(reabsorbs NaCl) Ascending limb: active transport of sodium and chloride into the interstitial fluid - Low permeability -> little water follows - Fluid becomes hypoosmotic Descending limb: - Loses water because it is very permeable to H2O and H2O follows the gradient - H2O is leaving the loop - Becomes more hyperosmotic as it moves down, but then becomes hypo as it enters the ascending loop Where does water go when it leaves the descending limb? The release of Na and Cl by ascending equal out the H2O released by the descending Consequences: - As fluid moves down descending limb its losing water, fluid inside is becoming concentrated-> turns at loop of henle and is now only pumping out Na and Cl, fluid then becomes hypoosmotic  - Cortical collecting duct: permeable to NaCl and water (in the cortex) - Osmolarity of IF in cortex is the same as blood - 300 - Medullary collecting duct: high water permeability-> urine back to hyperosmotic Vasa Recta and the hairpin turn: The vasa recta parallels the renal counter-current multiplier system - Ensures that the blood doesn't wash out the osmotic gradient Long capillaries that loop deeply into the medulla and then return to the cortical-medullary junction - Run next to loop of Henle - Similar to juxtamedullary nephrons Regulation of total Na+: Primary modes of regulation: 1. Altering volume filtered (GFR) a. GFR is regulated by cardiovascular baroreceptors that respond to change in pressure or plasma volume 2. Altering quantity reabsorbed a. Reabsorption is Increased by aldosterone, inhibited by atrial natriuretic factor (ANF) b. Aldosterone acts on distal tubules and cortical collecting ducts c. Aldosterone levels determined by renin-angiotensin system Rate limiting factor = renin concentration d. Renin converts precursor to angiotensin II which triggers the release of aldosterone from adrenal gland Renin secretion increases in response to: decreased NaCl delivery to macula densa and total body Na depletion Juxtaglomerular apparatus: Intersection of the macula densa in the distal tubule with the afferent and efferent arterioles - Secretes renin into the blood in the afferent arteriole in response to low sodium or GFR, low MAP and sympathetic NS activity How is pH altered? CO2 + H2O H2CO3- HCO3- + H+ Hypoventilation: - CO2 not eliminated, H+ accumulates - Termed respiratory acidosis Hyperventilation:  - Excess CO2 is eliminated, H+ drops - Termed respiratory alkalosis Most H+ is generated by body and comes from CO2 production The body also generates nonvolatile acids which are acids that cannot be removed by the lungs - In crisis ( vomiting or diarrhea) the pH changes rapidly - Lungs respond quickly via altered minute volumes - The kidneys respond slowly - Kidneys alter the number of bicarbonate ions, not H+ ions Bicarbonate reabsorption: filtered bicarbonate ions combine with secreted H+ forming CO2 and H2O which are then reabsorbed Bicarbonate generated in the tubule epithelia diffuses into the capillaries *** bicarbonate reabsorption is actually H+ secretion** Not enough bicarbonate -> H+ ions can bind to other anions Tubular reabsorption of bicarbonate occurs in the: ascending loop of Henle, proximal convoluted tubule, and cortical collecting duct Homeostasis: 1. Rate of H+ secretion 2. Rate of glutamine production (bicarbonate synthesis) ** adding additional HCO3- to plasma buffers more H+ and therefore raises pH Excess HCO3 secreted into the collecting duct Digestion: Major function of the digestive system: get ingested food into a form that can get into circulation and to cells - Under control of the enteric NS and CNS(parasympathetic and sympathetic) **The overall function of the digestive system is to process ingested food into molecular forms that are then transferred, along with small molecules, ions, and water, to the body's internal environment. Mouth(salivary glands) -> esophagus-> stomach -> small intestines -> large intestine GI anatomy: 4 processes that occur in the GI tract 1. Secretion (adding) 2. Digestion (breaking things down) 3. Absorption (things to blood) 4. Motility (movement) GI organs: GI tract- lumen is continuous w external world Accessory organs- secrete substances **secretions are important at every step along gut - Partly to add active components to gut - Partly to ensure motility Digestive secretions are mostly water - About 8L - Only 100mL are excreted in feces daily, indicating that GI mechanisms for H2O absorption are very efficient The GI Wall: - Convoluted -> increases surface area that the food can come in contact with - Multiple layers of muscle that helps maximize moving and mixing GI contents - Epithelial cells and tight junctions - Ducts: how secretions are delivered - Specialized cell types along lining: some secrete mucus, other hormones(endocrine) and exocrine cells(secrete locally-> only affect the area) The Villi: along the walls, contain capillaries - increase the surface area for absorption of nutrients Microvilli fringe the villi surface = increase surface area - Tiny projections off of the villi - The lacteal uptakes and breaks down absorbed fats - Carbs and proteins are entering the bloodstream inside of the villi It begins at the mouth: 1. Chewing: ensures that food is made able to pass through esophagus How is digestion started? 3 pairs of salivary glands that produce saliva Esophagus: - Upper part has skeletal muscle(voluntary), lower sphincter controlled by smooth muscle - Peristalsis moves food through lower esophagus - Secondary Peristalsis: If a large food bolus does not reach the stomach during a given swallowing sequence, stretch of the esophagus initiates reflexive motility - Stomach: specialized cells in the stomach synthesize and secrete mucus, fluid, enzyme precursors, hydrochloric acid and hormones - Smooth muscle responsible for gastric motility Regulation of GI processes: Acidic environment regulated via H+ transport 1. cephalic(head): sight, smell, taste, chewing a. Parasympathetic nerves to enteric NS -> increases HCl secretion 2. gastric(stomach): distension, acidity, amino acids, peptides a. Long and short neural reflexes, direct stimulation of gastrin secretion -> increases HCl secretion 3. intestinal(small intestinal tract): distension, acidity, osmolarity a. Long and short neural reflexes, secretin, CCK and duodenal hormones -> decreases HCl secretion **mostly intestinal triggers regulating pancreatic secretions, cephalic and gastric stimuli also regulate pancreatic secretions via parasympathetic NS What do we need to digest and absorb? - 50% carbs - 16% proteins - 33% fat - Vitamins, water and minerals Digestion: Mouth: salivary amylase- small amount of digestion - Most of digestion in small intestine(95%) with pancreatic amylase - salivary amylase digests starch Absorption: monosaccharides- facilitated diffusion across epithelial membranes(small intestine), diffuse into blood Secretion in stomach: Parietal cells secrete HCl(up to 2L per day) Chief cells secrete inactive pepsinogen - Low pH causes conversion to pepsin - Pepsin only active at low pH *not necessary for protein digestion but when its present it makes up 20% of protein digestion - Pepsin is also important for the digestion of collagen Proteins-> peptide fragments -Peptides -> amino acids via peptidases - Amino acids absorbed via cotransport with Na+ -Small peptides absorbed via H+ cotransport (then broken down) Digesting fats: Lipase begins the digestion of triglycerides - Upper portion of the stomach there is lipid droplets - Broken down into smaller droplets through emulsification Pancreas: Bicarbonate neutralizes acid from stomach - Lipase converts fat into fatty acids - Amylase converts polysaccharides to sugars  - Trypsin converts proteins to amino acids The liver: Receives absorbed nutrients via hepatic portal system Produces bile Small intestine: Micelles are in equilibrium with the dissolved fats Large intestine: Active transport of Na+ coupled w osmotic abs of H2O - Movement is slow Concentrates the material Control of GI function is regulated by amount and contents in the lumen NOT the nutritional state of the body The body is designed to absorb all of the nutrients that are ingested no matter if the body really needs them or not Only things from body that you can't digest are excreted- fiber, glycogen etc