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Flashcards in Midterm 1 Review Deck (79):

How do endocrine cells function?

Secretes hormones into blood vessels, target cells may be distant


How do paracrine cells function?

Secretes hormones which act locally on neighbouring cells


How do autocrine cells function?

Secretes hormones which act on themselves or on identical neighbouring cells


How do neuroendocrine cells function?

Secretes molecules from axon terminals into the bloodstream


How do neurotransmitter cells function?

Secretes molecules from axon terminals to actiate adjacent neurons


What do all cholesterol derivatives contain?

A sterol ring


Where are peptide hormones stored?

Secretory vesicles in the cytoplasm


How are hormones transported in the blood?

- Hydrophilic molecules can circulate in a free state
- Hydrophobic hormones will require a carrier protein specific to the hormone
- Binding proteins acts as a buffer: transports hormone and protect it from degradation


What are some common techniques used in endocrinology?

- Ablation
- bioassays
- immunoassays
- blot test
- in situ hydridization
- autoradiography


Compare bioassays and enzymoimmunoassays

- Bioassays measures the response of an animal or cell to a hormone (E.g rabbit test, human urine is injected into rabbit to detect levels of hCG, if present rabbit ovaries would ovulate)
- Bioassays are time consuming and does not accurately measure hormone levels
- Enzymoimmunoassay competitively binds an antibody to its antigen
- EIAs do not require radioactive tags, it is tagged with a compound that changes colours
- EIAs can be usde on blood and urine samples depending on the hormone


When does phosphorylation of tyrosine occur? What are they used for?

Typically at the beginning of a signal cascade, they serve as a docking site for down stream signal proteins


What type of cell surface receptor does insulin use?

Intrinsic tyrosine kinase activity


What are the sequences of events after insulin binding?

- autophosphorylation of intracellular domain of receptors
- docking and phosphorylation of IRS-1 and IRS-2
- activation of two major signal pathways


What is the P13 kinase pathway required for?

- Maintainence of active dephosphorylated glycogen synthase: increase glycogen synthesis
- Movement of glucose transporter GLUT4 to the outer cell membrane: increase glucose uptake


What are the steps of the P13 kinase pathway?

- IRS-1 is phosphorylated by the insulin receptor: P13K converts PIP2 to PIP3
- PKB bound to PIP3 is phosphorylated by PDK1
- GSK3 inactivated by phosphorylation cannot convert glycogen synthase to its active form: glycogen synthase remains active
- PKB stimulates movement of glucose transporter GLUT4 from internal membrane vesicles to the plasma membrane: increase glucose uptake


What does the MAPK pathyway do?

- Changes gene expression
- Increase cell dividision
- Activated by GH


How many times does the transmembrane domain cross through the membrane?

7 times


What are the functions of the G alpha subunits?

- Gs alpha: activates adenylate cyclase
- Gi alpha: inhibits adenylate cyclase
- Gq alpha: activates phospholipase C
- G0 alpha: activates ion channels


What are the three domains of the intracellular receptor?

- DNA hormone specific binding domain
- Conserved DNA binding domain
- Hypervariable domain


What are the target cells of the anterior pituitary?

- Somatotrophs (GH): 40 - 50%, all tissues
- Corticotrophs (ACTH): 15 - 20%, adrenal glands, adipocytes, melanocytes
- Mammotrophs (PRL): 10 - 15%, breasts and gonads
- Gonadotrophs (LH, FSH): 10 - 15%, gonads
- Thyrotrophs (TSH): 3 - 5%, thyroid glands


Which anterior pituitary subgroups are basophiles?

- thyrotrophs
- corticotrophs
- gonadotrophs


Which anterior pituitary subgroups are acidophiles?

- somatotrophs
- lactotrophs


What are the features of the pineal organ?

- pine cone shaped
- size of a rice grain
- interprets visual signals


What does the pineal gland secrete?



What is melatonin used for?

- Adjustment of jet lag
- Sleeping aid in the elderly


What are the main functions of oxytocin?

- Contraction of smooth muscles
- Lactation: through stimulation of muscles


Where are osmoreceptors located? What is its main function?

Detects changes in blood plasma and tries to maintain a set point


What happens during pregnancy in regards to the osmostat?

- osmostat will reset
- total body water increases 7 - 8L due to vasodilation
- placenta prouces enzyme to degrade vsaopressin


What are IGF-I and IGF-II dependent on? What are they important for?

- GH dependent
- important for growth and development


What is an older name for IGFs?



What does GH and IGF promote?

Promotes the growth of long bones at the epiphyseal plates by depositing calcium matrix which increase bone growth


How do GH receptors work?

Acts through the recruitment of tyrosine kinase and activation of STATs, MAPK or IP3K


Why do people use exogenous GH treatment?

Elderly use exogenous GH to decrease body fat, increase lean muscle tissue and bone tissue, improve some cognitive functions


What is the main function of prolactin?

Post partem activation of lactation
Development of mammary gland


What inhibits prolactin?



Where does prolactin stimulate milk secretion?

Alveolar epithelial cells


What is the tanning process?

- caused by UV lights
- uv lights cause DNA damage
- p53 levels are too high
- melanin will be deposited into the skin
- acts through paracrine function


What does ACTH stimulate?

Stimulates the adrenal cortex to release cortisol


Who usually has a GH deficiency?

Elders, usually take alternative GH to improve quality of life
they will have a decrease in muscle strength, lowered exercise tolerance, diminished libido


What are the side effects of gonadotrophin deficiency?

Oligoamenorrhea, dimished libido, infertility, hot flashes


What are the side effects of ACTH deficiency?

Malaise, fatigue, anorexia, hypoglycemia


What are the side effects of TSH deficiency?

Malaise, leg cramp, fatigue, dry skin, cold intolerance


What is doping?

The use and abuse of performance enhancing substances in elite sports


What are some of the motivations for the use of doping?

- Enhanced performance: increased strength, endurance, alertness, aggression
- Drive
- Relaxation
- Weight control
- Hide other drug uses
- Social support


What is the difference between elite and adolescent doping use?

Elite athletes use doping ecause it is the edge they feel they need to win
Adolescent athletes use doping typically due to peer/coach pressure


What are some excuses used for reason of doping?

- Spiking
- Testing procedures
- Natural occurence
- Pre-existing medical condition


What are beta-blockers use in doping?

- reduce blood pressure
- anti-anxiety
- used in sports that require a steady hand


What is erythropoeitin?

- released by the kidneys in response to low hematocrit
- stimulates RBC production from bone marrow
- manufactured by recominant DNA techniques


Why do people use blood doping?

- induced erythrocythemia: increase in Hb following reinfusion
- increase oxygen carrying capacity of Hb
- if there is more oxygen carrying capacity , more ATP production, more energy for muscles


What are the steps for blood doping?

- autologous reinfusion method: 2 units of blood is removed 4 - 8 weeks prior to competition
- Hb/Hct returns to pre-transfusion levels
- reinfusion 1 - 7 days prior to event
- typically used in treatment for anemia


How is blood doping detected?

- measure Hct> 50
- measure serum Fe and bilirubin
- urine test is not reliable


What are the negative side effects of doping?

- baldness
- reduced sperm count
- enlarged prostate
- shrinkage of testicles
- mood swings
- strokes and blood clots
(for women):
- reduced breast size
- enlarged clitoris
- increase in facial and body hair
- menstrual problems


How can athletes beat the system?

- catherization
- drink copious amounts of water
- take diuretics to dilute urine
- female athletes insert condoms with clean urine into vagina


What is cell to cell communication?

Cells can communicate with each other through:
- signals which are generated in special cells (hormone producing)
- cells are exposed to many signals at the same time
- other cells can recognise these signals and respond to them


What are some endocrine rhythms?

- Circadian rhythm: 24 hour cycle
- Infradian rhythm: 28 days


What is the basic structure of a cell surface receptor?

- Ectodomain: acts as a hormone binding protein
- Hydrophobic transmembrane domain: transport
- Cytoplasmic domain: induces a signaling cascade


What are the three major types of cell surface receptors?

- G coupled protein receptors
- Intrinsic tyrosine kinase
- Recruited tyrosine kinase


How many binding sites does GH have?

Two binding sites to bind to two receptors


What are the three branches of the signaling pathway of GH

Activation of JAK-2 phosphorylates itself, the cytoplasmic domain of the receptor and other proteins
- Branch 1: activation of the transcription regulatory proteins STATs
- Branch 2: activation of the MAPK pathway
- Branch 3: activation of the P13K pathway which is responsible for insulin like metabolic effects of GH


How do G protein coupled receptors relay signals?

- Bind and activate G proteins
- activation of G proteins will generate a response of second messengers (cAMP, DAG, IP3)
- activation of phospholipase C or adenylate cyclic will inhibit or stimulate second messengers


What are the two receptor classes?

Class 1: cytosolic - binds hormone then binds to DNA
Class 2: nuclear - already bound to DNA, then it binds to steroids


What is the DNA binding domain?

- two loops that form a zinc finger
- Class 1 receptors which form complexes with heat shock proteins
- zinc fingers are designed to recognise DNA spcifically in promoter regions


How is the pituitary controlled?

By the nervous system through hypothalamus


What is the supraoptic nuclei and paraventricular nuclei referring to?

Posterior pituitary


What is the hypothalamic-hypophysiotropic nuclei refering to?

Anterior pituitary


What are some of the side effects of melatonin?

- daytime sleepiness
- hypothermia
- desensitization of melatonin receptors
- possible interaction with those taking coumadin/warfarin


What is the primary regulator of osmolarity?



How is BP lowered by vasopressin?

- posterior pituitary releases vasopressin leading to vasoconstriction -> increasing arterial pressure
- renal fluid reabsorption will increase blood volume and also increase arterial pressure


What receptor does vasopressin bind to?

- G alpha S which will activate cAMP
- PKA will cause aquaporin 2 to be inserted into the membrane to uptake H20
- aquaporin is recycled and stored in the cytoplasm when it is not required
- produces more concentrated urine and decrease urine output


What is essential for the initation and maintainence of milk secretion?

Prolactin and cortisol


What inhibits prolactin?



Why do athletes inject themselves with GnRH?

To manipulate their body to produce higher levels of androgens
GnRH does not leave a trail in the body and have a shorter half life


What is cycling in terms of steroid use?

Taking multiple doses over a specific period then stopping for an equal or longer amount of time to decrease tolerance


What is stacking?

using a combination of anabolic steroids to avoid tolerance from developing


What is plateauing?

drugs will become ineffective after a certain level , reaches a threshold


What is tapering?

slowly decreasing steroid intake


What is pyramiding?

gradual increase then decrease in doses during a single cycle


What is tetrahydeogestinone?

A synthetic drug created by a nutritional supplemental company
- undetectable
- extremely potent anabolic steroid


What are the steps of the MAPK pathway?

- insulin receptor binds insulin and undergoes autophosphorylation
- insulin receptor phosphorylates IRS-1 on its tyrosine residue
- SH2 domain of Grb2 binds P-tyr of IRS-1: release of GDP
- activated Ras binds and activates Raf-1
- Raf-1 phosphorylates MEK on two ser residues: MEK phosphorylates MAPK on a Thr and Tyr residue