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?
- blot test
- in situ hydridization
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?
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?
Which anterior pituitary subgroups are acidophiles?
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
- 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?
- Testing procedures
- Natural occurence
- Pre-existing medical condition
What are beta-blockers use in doping?
- reduce blood pressure
- 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?
- reduced sperm count
- enlarged prostate
- shrinkage of testicles
- mood swings
- strokes and blood clots
- reduced breast size
- enlarged clitoris
- increase in facial and body hair
- menstrual problems
How can athletes beat the system?
- 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?
What is the hypothalamic-hypophysiotropic nuclei refering to?
What are some of the side effects of melatonin?
- daytime sleepiness
- 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
- extremely potent anabolic steroid