3/21 - UWorlds Flashcards
What substance activates the adrenal medulla and what does the adrenal medulla produce?
ACh stimulates the chromaffin cells (neuroendocrine cells) of the adrenal medulla to produce catecholamines (80% epinephrin, 20% norepinephrine)
Describe a crossover study including pros and cons to this study type
Subjects are randomly allocated to a sequence of 2 or more treatments given consecutively (e.g. receive drug for 2 weeks and rate experience then receive placebo for 2 weeks and assess vs. other group which will do placebo and then drug) Pro: This allows patients to serve as their own controls Con: Effects of one treatment may “carry over” and alter response of subsequent To limit this effect there should be a “washout” (no treatment) period between consecutive treatments
Describe a case-control study
Select patients with a disease (cases) and without that disease (control) and determine previous exposure status Compares disease vs. non-diseased
Describe a case series study
Descriptive study that tracks patients with a known condition (e.g. exposure, risk factor, or disease) to document natural history or response to treatment
Describe a cross-sectional study
Simultaneous measurement of exposure and outcome (ask people about current disease and risk factor at the same time) Measures prevalence
Describe a prospective cohort study
Selecting individuals (cohort), determining their exposure status, and then following them over time for development of disease
What is the function of telomerase and what cells is it commonly found in
Reverse transcriptase (makes DNA from RNA) that adds TTAGGG repeats to the 3’ end of chromosomes (telomere region) Commonly found in stem cells - have high telomerase activity so they can proliferate indefinitely
Describe inulin travel through the nephron
Inulin is freely filtered but not secreted or absorbed (filtered amount = secreted amount) Inulin clearance can be used to estimate GFR
Describe PAH (paraaminohippuric acid) travel through the nephron
PAH is freely filtered and also secreted into urine in the proximal tubule So PAH excreted > PAH filtered Very high clearance level PAH clearance can be used to calculate renal plasma flow
Mechanism of action of progesterone-only contraception
Thickens cervical mucus, impairing sperm penetration
Mechanism of action of combined hormonal contraception (estrogen + progesterone)
Suppresses GnRH and pituitary gonadotropin secretion, inhibiting ovulation
Location of macula densa cells and juxtglomerular cells
Macula densa cells are tall, narrow cells located in the distal tubule that monitor salt content and tubular flow rate
They transmit info to juxtaglomerular cells, modified smooth muscle cells, located mainly in the wall of the afferent arteriole with renin-containing granules
JG cells will undergo hyperplasia with chronic stimulation (e.g. renal hypoperfusion)
Mechanism of action of opioids
Pre-synaptic neuron: closure of voltage-gated calcium channels, leading to reduced Ca2+ influx and decreased NT release Post-synaptic neurons: bind and open potassium channels leading to increase K+ efflux, hyperpolarization, and inhibition of signal transduction
What is Asherman syndrome
Secondary amenorrhea due to loss of the basalis (stem cells of endometrium) and scarring Often due to overaggressive D&C
What is Kallmann syndrome
Defective migration of GnRH cells and formation of the olfactory bulb Presents with primary amenorrhea, absent secondary sexual characteristics, and olfactory sensory defect (anosmia)
