unit 4

homeostasis

physiological state of the body in which internal physical and chemical conditions are kept within a range thats suitable for life processes

• done through a series of monitored adjustments

• dynamic equilibirum, the body state can change within a certain range

homestatic control

• three components:

  • sensor (monitor)

  • integrator (control center)

  • effector (regulator)

• once an organ begins to operate outside its normal limits, special sensors in the organs send a signal to an integrator.The coordinating center relays the information to the appropriate effector, which helps restore the normal balance.

example of homeostatic control center

• Ex. carbon dioxide levels increase during exercise

• Chemical receptors in the brain are stimulated because of the high level of CO2 (sensor)

• The brain sends impulses through nerve cells to the muscles (integrator)

• The muscles work such that they increase the depth and rate of breathing (effector)

• The increased breathing movements help flush excess carbon dioxide from the body

negative feedback

process by which a mechanism is activated to restore conditions to their original state (resistant to change)

positive feedback

process by which a small effect is amplified, less common

birth process in humans (positive feedback)

• A decrease in progesterone (a hormone associated with pregnancy), is believed to initiate small contractions of the uterus

• The contractions bring about the release of another hormone, oxytocin, which causes much stronger contractions of the uterus

• As contractions build, the baby moves toward the opening of the uterus, the cervix

• This causes even greater release of oxytocin and stronger contractions until the baby is expelled from the uterus

• Once the baby is expelled, the uterine contractions stop, which in turn stops the release of oxytocin

thermoregulation

maintainence of body temperature within a range that enables cells function efficiently

ectotherms

• depend on air temperature to regulate metabolic rates

• invertebrates, most fish, amphibians, reptiles

  • some reptiles have behaviour adaptations to regulate body temperature, they lay on rocks to get sun and then retreat to shady areas

endotherms

• able to maintain constant body temperature regardless of their surroundings

  • ex: shiver to generate heat

• mammals (including humans) and birds

• hypothalamus is a region of a vetebrates brain responsible for coordinating many nerve and hormone functions (integrator)

• thermoreceptors in hypothalamus (sensor)

hypothermia

• condition in which the body core temperature falls below normal range

• drop of only a few degrees can cause coma or death

  • some endotherms can change their interal environment and go into hibernation

diving reflex

• mammals have this

• body’s physiological response to submersion in cold water

  • includes selectively shutting down parts of the body in order to conserve energy for survival

importance of excreting waste

• byproducts of many reactions are small but harmful, so they must be eliminated

  • lungs eliminate CO2 from cellular respiration

  • large intestines remove toxic waste from digestive system

  • liver transforms ingested toxins (alcohol, heavy metals) into soluble compounds that can be eliminated by the kidneys

  • liver transforms hazardous products of protein metabolism into metabolites, which are eliminated by the kidneys

deamination

removal of the amino group in an amino acid, byproduct is ammonia which is every toxic

• occurs when we convert excess protein into carbohydrates and when breaking down nucleic acids

• unicellular organism: wastes are released directly from the cell (diffuses out)

• multicellular organism: not every cell is in direct contact with the external environment so waste must be temporarily stored and transported to cells that can excrete it (nerphrons)

deamination - fish

release ammonia through their gills to prevent buildup

deamination - mammals/land animals

must store waste using the liver, ammonia undergoes a reaction to form urea (less toxic)

deamination - bird

make uric acid, excreted as crystals with next to no water loss

urinary system

• 2 kidneys

  • filters wastes from blood in the renal arteries

  • blood enters from the renal arteries which branch off the aorta

• ureters

• urinary bladder

• urinary sphincters

• urethra

ureters

tubes that conduct urine form the kidneys to the bladder

urinary sphincters

muscle located at the base of the bladder that acts as a valve permitting storage of urine

urethra

the tube that carries urine out of the body

kidneys

• humans have two

• in abdominal cavity, below the ribcage at either side of the spine

• embedded in fatty tissue for protection

• blood filters

  • blood is brought by the renal artery and after its filtered, its taken away from the renal vein

functions of kidney

• regulation of blood water levels

• reabsorption of useful substances into the blood

• Adjustments of the levels of salts and ions in the blood

• Excretion of urea and other metabolic wastes

• Homeostatic regulation of pH

• help convert vitamin D3 into a hormone that regulates Ca+ balance

• Production of hormones:

  • erythropoietin

  • renin

erythropoietin

regulator of red blood cell synthesis (hormone)

renin

hormone linked to salt and water balance

cross section of kidney

• cortex

  • outer layer of connective tissue all around the kidney

• medulla

  • inner layer beneath the cortex

• renal pelvis

  • hollow chamber in the middle of the kidney that joins it with the ureter

formation of urine and osmoregulation

• filtration (blood to nephron)

  • blood/bodily fluids pass through a selectively permeable membrane (bowman’s capsule), makes filtrate

• reabsorption (nephron to blood)

  • transfer of essential solutes and water from the nephron back into the blood. forms urine

• secretion (blood to nephron)

  • movement of materials from the blood back into the nephron

  • maintains blood pH, K+ concentration in the blood, and nitrogen waste concentration in the filtrate

nephrons blood movement

• slender tubules, functional unit of kidneys

• afferent arterioles

  • small branches from the renal artery that supply the nephrons with bood

  • branch into a capillary bed (glomerulus)

• glomerulus

  • high pressure cappilary bed that is the site of filteration

• efferent arterioles

  • blood leaves the glomerulus through these

  • blood is carried from the efferent arterioles to a net of capillaries (peritubular capillaries)

• peritubular capillaries (vasa recta)

  • wrap around the kidney tubules

  • lead to venules that lead the blood out of the kidney through the renal vein

parts of nephron

• bowman’s capsule

  • funnel structure that surrounds the glomerulus

  • located at the cortex

  • fluids processed into urine enter bowman’s capsule from the blood

  • tapers into a thin tubule called..

• proximal tubule

  • carries urine to..

• loop of henle

  • thin tube that descends into the medulla of the kidney and the starts ascending back up and leading the urine into the..

• distal tubule

  • carries urine to..

• collecting ducts

  • collects urine from many nephrons that, in turn, merge into the pelvis of the kidney

filtration

• each nephron has an independent blood supply

• blood moves through the afferent arteriole into the glomerulus

• dissolved solutes pass through into bowman’s capsule

  • move from area of high pressure to low pressure

what enters bowmans capsule

• water

• Na+ and Cl- ions

• glucose

• amino acids

• H+

• vitamins

• minerals

• urea

• uric acid

what doesn’t enter bowmans capsule

• plasma proteins

  • albumins - osmotic balance

  • globulins - antibodies, immunity

  • fibrinogens - blood clotting

• erythrocytes (RBCs)

• platelets

these are all too large to move through the glomerulus

fluid flow through the kidney

• 600 ml of fluid flows through the kidneys every minute. 120ml is filtered into the nephrons

  • if none of this filtrate was reabsorbed then you would make 120ml of urine

  • would need 1L of fluids every 10 minutes to maintain homeostasis

• reabsorption ensures that only 1ml of urine is made

reabsorption

• active transport

• passive transport

• carrier molecules move Na+ across the cell membranes of cells that line the nephron and into the intercellular spaces

  • Negative ions, such as Cl- and HCO3- follow the positive Na+ ions by charge attraction

  • mitochondria supply the energy necessary for active transport (energy supply is limited though)

• Reabsorption occurs until the threshold level of a substance is reached

• Excess NaCl remains in the nephron and is excreted with the urine

• Other molecules are actively transported from the proximal tubule

  • Glucose and amino acids need specific carrier molecules to shuttle them back into the blood

  • If there is excess glucose, it will not be shuttled out, will be lost in the urine

osmotic gradient

• Solutes that are actively transported out of the nephron create an osmotic gradient that draws water from the nephron, into interstitial fluid surrounding the nephron cells (hypertonic environment)

• A second osmotic force is created by the proteins that are in the blood (in the peritubular capillaries) that could not get filtered into the nephron

  • The proteins remain in the bloodstream and draw water from the interstitial fluid, aiding reabsorption

• As water is reabsorbed from the nephron, the remaining solutes in the nephron become more concentrated

• Molecules such as urea and uric acid will diffuse from the nephron back into the blood, but less is reabsorbed than was originally filtered (so there should be more in the urine at the end)

secretion

• movement of wastes from blood into the nephron

  • nitrogen containing wastes

  • excess H+

  • minerals like K+

  • drugs like penicillin

proxmial tubule

• pH is controlled by:

  • secretion of H+

  • reabsorption of bicarbonate ions (HCO3-)

distal tubule

• fine tuning occurs here

• Selective reabsorption of nutrients from the blood by active transport

• helps regulate potassium and salt levels

• pH is also controlled here by secretion of hydrogen and bicarbonate ions

• The distal tubule is lined with cells with a lot of mitochondria so energy can be produced for active transport

filteration

• Blood pressure forces 20% of the blood plasma entering the glomerulus into the surrounding Bowman’s capsule

• The fluid and small solutes entering the nephron are called the filtrate

• The filtrate is isotonic with blood plasma

• Molecules too large to filter through the glomerulus, such as blood cells and albumin, remain in the circulatory system

  • if these are found in urine, there is a problem

flow of filtrate

• enters bowman’s capsule and flows into the proximal convoluted tubule

  • almost all glucose, amino acids, and other organic molecules are reabsorbed via active transport

• 60-70% of Na+ in the filtrate is reabsorbed (active and passive transport)

• water and Cl- passively flow

• filtrate then flows down the descending limb into the renal medulla, where theres an increasing ionic concentration in the interstitial fluid, causing more water to diffuse out of the nephron

• filtrate flows through the ascending limb, which is impermeable to water, and then into the distal convoluted tubule

• filtrate continues through the collecting duct, where water reabsorption is under hormonal control

• remaining filtrate, urine, is hypertonic to the blood and highly concentrated in urea and other solutes

selective permeability

• walls of the proximal tubule and descending limb of the loop of henle are permeable to water

• walls of the lower ascending limb are permeable only to salt

osmolarity gradient

• The selective permeability of the tubules establishes an osmolarity gradient in the surrounding interstitial fluid

• By exiting and then reentering at different segments of the nephron, solutes create an osmolarity gradient, with tissue osmolarity increasing from cortex to medulla

• The solutes that contribute to the maintenance of the gradient are urea, and salt (Na⁺ and Cl^-)

• Salt is cycled between the two limbs of the loop of Henle

• Na⁺ and Cl^- diffuse of out the lower half of the ascending limb, while the upper half actively pumps out Na⁺ (and Cl^- passively follows)

• This combination of passive diffusion and active transport of solutes maximizes water conservation and the excretion of urine hypertonic to the blood

kidney and regulation

• the body must adjust to maintain homeostasis

  • increased water intake = increased urine output

  • increase in excersize/decreased water input = reduced urine output

• invovles interaction between two communication systems: nervous and endocrine

osmolarity

• number of partiles per litre of solution

• water moves down its concentration gradient across membranes

  • high water/low solute → low water/high solute

kidneys and blood pressure

• adjust blood volume

• When increase fluid loss = decrease blood pressure = decrease delivery of oxygen and nutrients to tissues

• Juxtaglomerular apparatus (in glomerulus) detects low blood pressure

  • release an enzyme called RENIN

• Renin converts angiotensinogen (inactive form) into angiotensin, it can do two things:

  • Constriction of blood vessels → increase in blood pressure

  • Stimulates release of ALDOSTERONE from adrenal glands → carried via blood to kidney → acts on nephrons to increase Na+ reabsorption → causes water to follow Na+ so water moves from nephron into blood → increase fluid levels (volume) and increase blood pressure

regulation of water levels in blood by ADH (too little water)

Too little water in blood → detected by hypothalamus → more ADH secreted into blood by pituitary gland → kidneys absorb less water from blood → less urine produced → blood water level back to normal

regulation of water levels in blood by ADH (too much water)

Too much water in blood → detected by hypothalamus → less ADH secreted into blood by pituitary gland → kidneys absorb more water from blood → lots of dilute urine produced → blood water level back to normal

ADH

anti-diuretic hormone/vasopressin

kidneys and pH balance

• The pH of the body remains relatively normal between the ranges of 7.3-7.5

• Buffer systems within body control pH using bicarbonate ion that are present in the blood 

• Carbonic acid, which is weak, is produced and breaks down into carbon dioxide and water 

• The carbon dioxide is transported to lungs and exhaled 

• Carbonic acid will break down and the bicarbonate ion will absorb excess H+ preventing a change in pH

• The buffer is restored so that it can be used as needed later on 

• The kidney restores the buffer by reversing reaction at times 

• H₂O + CO₂ ⇌ H₂CO₃ ⇌ HCO₃^- + H+

how does it get started? Carbon dioxide is actively transpired from the peritubular capillaries into the cells of nephron where it combines with water to start the reaction

urinalysis

• kidney disorders can be detected by urinalysis

• malfunctional kidneys are affected when other systems break down, and dysfunctional kidneys affect other systems

diabetes mellitus

• caused by inadequate secretion of insluin from islet cells in the pancreases

  • without insulin, blood sugar levels rise. cells can’t take up as much glucose without insulin

• cells of the proximal tubule have enough ATP to reabsorb 0.1% of blood sugar

• excress sugar reamins in the nephron, provides osmotic pressure

  • opposes osmotic pressure created by other solutes that have been actively transported out of the nephron

  • water stays in the nephron and is lost as urine (hypertonic)

  • people with diabetes are thirsty because of this

• type 1: autoimmune disease

• type 2: body becomes resistant to insluin or doesn’t produce

diabetes mellitus side effects

• polyuria

• polydipsia

• weight loss

• hunger

• blurred vision

• slow healing from sores/infection

• numbness/tingling

diabetes melitus treatment

• life style changes

• medication

• monitoring

• no cure completely

diabetes insipidus

• caused by destruction of ADH producing cells of the hypothalmus or by the destruction of the nerve tract leading from the hypothalmus to the pituitary gland

• without ADH to regulate water reabsorption, urine output increases (as does thirst)

• symptoms: excessive urination, fatigue, dizziness

• treatment: Desmopressin to replace ADH, diuretics, low salt diet

bright’s disease (nephritis)

• not a single disease, but a broad description of many dieases that have inflammed nephrons

• one type affects the blood vessels of the glomerulus

  • toxins produced by invading microbes destory the vessels, altering permeability of nephrons

  • proteins and other large molecules are able to pass into the nephron

  • since theres no method to reabsorb protein, they create an osmotic pressure that draws water into the nephron

  • the movement of water increases urine output

• symptoms: hypertension, fatigue, fluid retention, albumin in urine

• treatment: reduce inflammation, blood pressure meds, diuretics, dialysis or transplant

kidney stones

• caused by preciptation of mineral solutes from the blood

  • urine becomes too concentrated and substances in it crystalize to form stones

• two groups:

  • alkaline (basic) stones

  • acid stones

• sharp stones can lodge in the renal pelvis or move into the narrow ureter, delicate tissues are torn as it moves towards the bladder

  • can move farther down the excretory passage and lodge in the urethra, causing pain as it moves

kidney stones causes

• related to decreased urine volume or increased excretion of stone forming compoents like calcium, oxalate, urate, cystine

• stones form in the urine collecting area (the pelvis) of the kidney

• factors predisposing to kidney stones:

  • recent reduction in fluid intake

  • increased excerisze with dehydration

  • medication that cause hyperuriemia (high uri acid)

  • history of gout

blasting kidney stones

• traditional treatment is surgical removal followed by rest

• extracorporeal shock wave lithotrispsy (ESWL)

  • greatly improved prospects for kidney stone patients with stones less than 2cm in size

  • nonsurgical technique that uses high-energy shock waves to break the stones into small fragments which can be voided through the excretory system

• not all stones can be eliminated this way, consider the size, location, and composition of the stone

• outpatient procedure

percutaneous nephrolithotripsy (PNL)

• technique for removing large/dense stones and staghorn stones

• done via a port created by puncturing the kidney through the skin and enlarging the access port to 1cm in diameter (no surgical incision)

  • a urologist inserts instruments via this port to break up the stone and remove debris

• done under anesthesis and flouroscopy

dialysis

• machine can restoire proper solute balance for people whose kidney can’t effectively process bodily wastes

  • exchange of substances across a semi-permeable membrane

  • operates like a kidney- principles of diffusion and blood pressure

  • can’t do active transport

hemodialysis

• machine connected to the patients circulatory system by a vein

• blood is pumped through a series of dialysis tubes that are submerged in a bath of various solutes

  • glucose and a mix of salts set up concentration gradients

• dialysis fluids have no urea so this moves from the blood into the fluid until equal concentrations are established

  • dialysis fluids will be continously flushed and replaced to remove urea

• body will also recieve the hormones the kidney can’t make

• dialyzer - mimics action of nephron

peritoneal dialysis

• done through the peritoneal membrane (lining of abdominal cavity)

  • 2L of dialysis fluid (dialysate) is pumped into the abdominal cavity and the membranes of the cavity selectively filter wastes from the blood

• urea and other wastes diffuse from the plasma into the peritoneum and into the dialysis fluid

  • waste accumulate and can be drained off and replaced serval times a day

• this allows for more independance because patients can perform the procedure by themselves

dialysis is not a kidney

• can remove toxic wastes and matain electrolyte balance

• can’t:

  • produce hormones like erythropoietin and renin

  • activate vitamin D

• a new technique is to transplant kidney cells from a pig into a dialysis machine, living cells not only produce renal hormons but seem to be much better at regulating electrolytes and responding to ingested foods with a wider range of pH

kidney transplant

• 85% successful

• transplanted kidney produces hormons and responds to homeostatic adjustment of other body systems

• place a new kidney and ureter in the lower abdormen, old kidney isn’t removed unless its large/infected

  • sometimes dialysis is needed until the new kidney can fully function

• disadvantage is the immune response of the recipient

  • donor kidney is often identified as a foregin invader and the immune system will try to destory it

  • immunosupressive drugs are given

endoctine system

• acts as a means of internal communication, coordinating other organ systems

• meant to maintain control over a longer duration than the nervous system

• glands synthesize and secrete hormones directly into the circulatory system

endocrine glands

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hormones

• chemical messengers

  • some are produced in one part of the body and sent through the blood stream to affect the cells somewhere else

  • only need a small amount, effects various tissues differently

• hormonal control:

  • regulation of internal environment (temperature, water balance, ions)

  • growth and development

  • metabolism

  • reproduction

hormonal action

act in three different ways

1. control rates of enzymatic reactions (ex: cortisol controls gluconeogensis)

1. control transport of molecules across cell membranes (ex: aldosterone adds sodium channels to the nephron)

2. control gene expression and the synthesis of proteins (ex: testosterone increases production of sperm)

receptors

• the variability in tissue response to hormones depnds on their recptors

  • different receptor = different response

  • ex: oxytocin causes cells of the mammary gland to start milk production while in the uterine lining it starts contractions

steroid hormones

• made from cholesterol

• insoluble in water, soluble in fat

• includes male and female sex hormones

• includes cortisol (stimulates the conversion of amino acids to glucose by the liver)

sterioid hormone transportation

• diffuse from the capillaries into the interstital fluid and then into the target cells, where they combine with receptor molecules in the cytoplasm

• the hormone-receptor complex then moves into the nucleus and attaches to a segment of chromatin that has a complementary shape

• hormone activates a gene

• transcription produces mRNA

• mRNA goes to the cytoplasm to be transcribed into protein

protein hormones

• contain chains of amino acids

• soluble in water

• includes insulin and growth hormone

• combine with recptors on the cell membrane (don’t enter the cell)

cascade effect

• protein hormones act as first messengers

  • their binding to specific receptors on the surface of their target cells triggers a series of enzmatic reactions within each cell

  • the first may be conversion of ATP to cAMP

  • this reaction is catalyzed by the enzyme adenylyl cylase

• cAMP acts as a second messenger, relaying messages from the extracellular protein hormones to cytoplasmic enzymes and intitating a series of successive reactions in the cell

• with each step, the hormones effects are amplified (cascade effect)

• the cytoplasmic enzyme phosphodiesterase stops cAMP

thyriod stimulating hormone (TSH) (cascade effect)

• attaches to the recptor sites in the thyroid gland and then cAMP is produced in thyroid cells

• cAMP in the thyroid cell activates enzymes which begin producing thyrozine (regulates metabolism)

• note: cells of the kidneys and muscles are not affects because they don’t have recptors for TSH

pituitary gland

• “master gland” - excersises control over many other endocrine glands

• small sac like structure connected by a stalk to the hypothalmus

  • anterior lobe

  • posterior lobe

• interaction betwee the nervous and endocrine system is the hypothalumus-pituitary complex

• pituitary gland produces and stores hormones

• hypothalumus tells the pituitary when to release the hormones

  • nerve ends of the cells of the hypothalmus secrete hormones that travel in the blood to the pituitary, causing the release of pituitary hormones, which are then carried by blood to target tissues

anterior pituitary

• synthesizes direct and tropic hormones

• direct hormones

  • directly stimulate their target organs

  • GH and PRL

• tropic hormones

  • stimulate other endocrine glands ro release hormones

  • FSH, LH, ACTH, TSH

• the hypothalmus regulates the release of hormones from the anterior pituitary

follicle stimulating hormone (FSH)

• in female ovaries:

  • causes maturation of ovarian follicles (these hold eggs)

• in male testes:

  • stimulates maturation of seminiferous tubules, promotes development of sperm cells in testes

luteinizing hormone (LH)

• in female ovaries:

  • stimulates the ovulation and formation of corpus luteum

  • corpus luteum - mass of cells that forms in the ovary and is responsible for the productuion of progesterone in pregnancy

• in male testes:

  • stimulates the interstitial cells of testes to synthesize testosterone

adrenocorticotropic hormone (ACTH)

• in response to stress, ACTH stimulates the adrenal cortex to synthesize and secrete the hormone corticosterioids

  • glucorticoids

  • mineralcorticoids

  • cortical sex hormones

glucocorticoids

• cotrisol and cortisone

• they raise blood glucose levels by promoting glucogenogensis and decrease protein synthesis

mineralcortioids

primarily aldosterone (increases blood volume/pressure)

cortical sex hormones

adrenal cortex secretes small amounts of androgens (male sex hormones) in both males and females

thyroid stimulating hormone (TSH)

stimulates thyroid gland to absorb iodine and synthesisze and release T3 and T4 which stimulate cell metabolism

prolactin (PRL)

• stimulates and maintains milk production in female mammary glands in lactating females

• dpomaine inhibits the secretion of prolaction

growth hormone (GH)

• promotes bone and muscle growth

• inhibits uptake of glucose by certain cells and stimulates the breakdwon of fatty acid, conversing glucose

• in kids:

  • GH deficency can lead to stunted growth (dawfism)

  • overproduction results in gigantism

• in adults:

  • overproduction causes acromegaly, disoder characterized by disproprotionate overgrwoth of bone, particularly in skull, jaw, feet, and hands

• somatostatin inhibits secretion of GH

posterior pituitary

• stores and releases hormones which have been produced in the hypothalamus

• ADH

  • increases permeability of the nephrons collecting duct to water, increasing water reabsorption and increasing blood volume

• oxytocin

  • secreted in childbirth

  • increases strength and frequnecy of uterine contractions

  • also stimulates milk secretion in mammary glands

metabolism

• chemical reactions involved in maintaining the living state of cells

  • catabolism - breakdown of molecules to obtain energy

  • anabolism - synthesis of compounds needed by cells

• effected by:

  • thryoid gland - produces T3, T4, calcitonin

  • parathyroid glands - produces PTH

  • anterior pituitary - produces GH

thyroid gland

• bilobed gland located at the base of the neck

• produces T3 and T4 hormones which regulate body metabolism and the growth and differentiation of tissues

  • affect the rate glucose is oxidized

  • both hormones appear to have the same function

T3 and T4

• derived from iodination of amino acid tyrosine

• necessary for growth and neurological development in children

• increase rate of cellular respiration

• increase rate of protein and fatty acid synthesis and degradation in many tissues

negative feedback - thyroid

• when metabolic rate decreases, receptors in the hypothalmus are activated

• nerve cells secrete thryoid releasing hormone (TRH)

• TRH stiumlates the anterior pituitary to release thryoid stimulating hormone (TSH)

• TSH is carried by the blood to the thyroid gland to cause the release of T3 and T4

• T3 and T4 raise the metabolism by stimulating increased sugar utilization by body cells

• higher plasma levels of thyroid hormones inhibit TRH and TSH secretion, returning plasma levels to normal

hypothroidism

• inflammation of the thyroid or iodine deficney causes this

• thyorid hormones are undersecreted/not secreted

• symptoms:

  • slowed heart and respiratory rate

  • fatigue

  • weight gain

  • cold intolerance

• in infants - cretinism. characterized by mental retardation and short stature

hyperthyroidism

• thryoid is overstimulated, hormones are over secreted

  • graves diease causes this. autoimmune dieases, antibodies attack the thyroid, causing more hormones to be secreted

• symptoms:

  • weight loss

  • increased metabolic rate

  • feelings of excessive warmth

  • profuse sweating

  • palpitations

goiter

• in hyper- + hypothyroidism

• thyroid enlarges, forming a bulge at the neck

• may be the result of insufficient iodine in diet

  • without it, thyroid production and secretion of thyroxine (T4) drops

  • causes more TSH to be produced, stimulating the thyroid more. thyroid cells develope and enlarge more

• goiter emphasizes the importance of negative feedback, nervous system should be able to inhibit overactivity

calcitonin

• decreases plasma Ca+ concentration by inhibiting the release of Ca+ from bone

• secretion is regulated by plasma Ca+ levels

parathyroid glands

• four small pea shaped structures embedded in the posterior surface of the thyroid

• glands synthesize and secrete parathyroid hormone (PTH)

  • with calcitonin and vitamin D, regulates plasma Ca+ concentration

• PTH acts on:

  • kidneys

  • intestines

  • bones

parathyroid hormone (PTH)

• stimulates bones to release Ca+

• stimulates kidneys to reabsorb more Ca+

• converts vitamin D to its active form, which stimulates intestinal calcium absorption

• once calcium levels rise, PTH release is inhibited

  • too high levels of PTH can cause break down of bone or stones to form in the kidneys or blood vessels

• low levels of vitamin D cause rickets. too little calcium and phosphorupuse are reabsorbed and bones don’t develope properly

calcium

• principle component of bone

• regulator of muscle contraction

• cofactor for normal blood clotting

• also plays a role in:

  • cell movement

  • exocytosis

  • neurotransmitter release

growth hormone - muscle growth

• stimulates uptake of amino acids and stimulates ribosomes to follow the instructions for protein synthesis

• as a person ages, GH production begins to decline and cellular repair and protein replacement is compromised

• as you age, protein is also replaced by fat, causing changes in body shape

growth hormone - bone growth

• stimulaates the production of insluin-like growth factor (produced by liver)

• in response to GH, insulin-like growth factors are secreted into the blood, where they stimulate cell division in the growth plates which cause elongation of the skeleton

  • promotes elongation of long bones

growth hormone - break down of fats

• increases fatty acid levels in the blood by promoting the breakdown of fats held in adipose tissues

• the muscles use fatty acids instead of glucose as a source of metabolic fuel

  • doing this increases blood glucose levels

  • this is important for glucose dependant tissues like the brain

  • this metabolic pathway is important in times of prolonged fasting where glucose supplies are limited

GH not just for growth

• GH is the most abundant hormone produced by the anterior pitutiary gland

• it helps adjust blood sugar

• enhances immune system

• slows aging

• builds muscle