Physiology Flashcards
How does altitude sickness present/what is the time course?
Immediately decreased O2 will cause hyperventilation in an effort to increase O2 delivery. This will cause CO2 to be blown off and thus pH to rise/become alkalotic.
Within 48 hours renal bicarbonate excretion compensates for the alkalosis to stabilize the pH and bring it within normal or near normal.
What is PSVT and how is it treated?
PSVT causes palpitations and rapid regular tachycardia most often due to a reentrant impulse traveling circularly between the slowly and rapidly conducting segments of the AV node.
Vagal maneuvers such as carotid massage, Valsalva, and cold water immersion can acutely terminate PSVT.
How does carotid massage work?
An afferent limb of the carotid sinus reflex travels with CN IX and arises from the baroreceptors in the carotid sinuses to the vagal nucleus and medullary centers. An efferent limb carries parasympathetic impulses to the SA and AV nodes via vagus (CN X). Carotid sinus massage leads to increased afferent firing from the carotid sinus, which in turn increases vagal parasympathetic tone, slowing conduction through the AV node and prolonging the AV node refractory period.
What are the fastest to slowest conduction tissues of the heart (with mnemonic)?
“Park AT VENTure AVenue”
Fastest: Purkinje Atrial Ventricular AV node Slowest^
What part of the kidney reabsorbs the majority (>60%) of water regardless of hydration status?
Proximal tubule
Absorption is isosmotic with absorption of solutes (Na, Cl, glucose) and no concentration or dilution occurs
Prolonged untreated OSA can lead to:
Pulmonary vasoconstriction -> Pulmonary hypertension -> Right heart failure
Systemic hypertension due to chronic sympathetic stimulation and elevated plasma Norepi
Loss of diurnal variation in BP
Increased risk of sudden cardiac death
Women with PCOS have an elevated ____:____ ratio.
LH:FSH
What adrenergic receptors are on the uterus? in the pupil?
Uterus = beta 2 Pupil = alpha 1
What is Neuroleptic Malignant Syndrome?
A potentially life-threatening adverse reaction to neuroleptics (antipsychotics).
4 primary features:
- Hyperthermia
- Severe generalized “lead-pipe” rigidity
- Autonomic instability
- Altered mental status
Failed fusion of the edges of the neural plate/closure of the rostral neuropore leads to:
What elevated markers will you find?
Anencephaly
Elevated AFP and AchE because they leak out
Curiously, ___ dietary calcium and ___ dietary oxalate and sodium are risk factors for calcium oxalate stones.
low calcium
high oxalate
high sodium
SERUM calcium is usually normal though.
Alkaline urine leads to formation of calcium _____ stones.
PHOSPHATE!!
What is reverse T3 (rT3)?
An inactive form of thyroid hormone that is generated almost entirely from the peripheral conversion of T4.
What is a glucagonoma?
A rare tumor arising from the alpha cells of the pancreatic islets of Langerhans. They secrete tons of glucagon leading to hyperglycemia/DM.
Characteristics:
Necrolytic migratory erythema
Erythematous papules/plaques with central clearing on face, groin, and extremities
GI symptoms (diarrhea, anorexia, abdominal pain)
What are the non-polar, hydrophobic amino acids?
GAVLIPPTM
Glycine Alanine Valine Leucine Isoleucine Phenylalanine Proline Tryptophan Methionine
Symptoms of thyroiditis (e.g. acute supperative, subacute, post-partum) are typically _______, while symptoms of a pheochromocytoma are more often _______.
Thyroiditis = constant Pheochromocytoma = (most often) episodic
What different histologies/types can craniopharyngiomas take?
Solid, cystic, calcified
Often all types seen together
Inhibin is made by the _____ cells and is stimulated by ____.
Sertoli
FSH
Inhibin works as a negative feedback on FSH production
Sertoli cells produce androgen-binding protein locally to do what?
Generate local high levels of testosterone in the seminiferous tubules of the testicles. High local levels of testosterone (and FSH) are necessary for spermatogenesis.
Note, this is in contrast to the sex hormone-binding globulin which circulates in the blood.
Proptosis/ophthalmopathy seen in Grave’s is due to ?
GAG and inflammatory infiltration -> expansion of extra-ocular muscles and tissue
Thyroidectomy can damage the _________ nerve which innervates the _____ muscle. Ultimately causing a hoarse voice.
External branch of the superior laryngeal nerve. Innervates the cricothyroid muscle
How is congenital adrenal hyperplasia (usually due to 21 alpha hydroxylase deficiency) treated?
ACTH suppression. Since little to no cortisol is made, there is no feedback inhibition of ACTH. ACTH keeps getting pumped out and thus stimulating the adrenal cortex which results overproduction of androgens.
In the pancreatic beta cell, stimulation of ____ 2 receptors promotes insulin secretion while stimulation of ____ 2 receptors inhibits insulin release.
beta 2 = pro insulin
alpha 2 = anti insulin
however, alpha 2 overrides so overall sympathetic stimulation causes inhibition of insulin.
What effect does estrogen have on the thyroid?
Increased estrogen (e.g. pregnancy, OCPs, HRT) raises circulating thyroxine-binding globulin which binds T3 and T4.
As a result, free T4 and free T3 levels decrease. This leads to an increase in TSH until new extra TBG is saturated and free levels return to normal, i.e. euthyroid. Note that overall this still leaves an increased TOTAL (i.e. bound + unbound) T4 and T3.
What is the single most common cause of acute hypocalcemia?
Injury to parathyroid glands during thyroid surgery.
Albumin releases calcium in ______osis to bind to posphate ions and buffer the blood. Ultimately this causes hypercalcemia.
Acidosis
Acidosis = ______calcemia
hyper
Why do blood transfusions sometimes cause hypocalcemia?
Transfused blood contains albumin, phosphate, and citrate, all of which bind calcium -> reduced ionized calcium = hypocalcemia
Propylthiouracil and Methimazole are used in the tx of hyperparathyroidism because they inhibit the enzyme _________ which is responsible for iodine organification/movement into the colloid.
Thyroid peroxidase
What type of myopathies cause increased CK and which don’t?
Increased CK:
Inflammatory (e.g. polymyositis, dermatomyositis)
Statin-induced myopathy
Hypothyroid myopathy
Normal CK:
Glucocorticoid-induced myopathy
Polymyalgia rheumatica
Which myopathy curiously does not cause muscle pain?
Glucocorticoid-induced myopathy
Weakness and atrophy but NO pain
Beta blockers block ______ which is helpful in treating hyperthyroidism until a more definitive treatment is initiated.
Conversion of T4 to T3.
they also treat the symptoms such as tachycardia
Which drugs block the peripheral conversion of T4 to T3?
Propylthiouracil
Beta blockes
Ipodate (contrast agent)
The medullary thyroid cancer associated with MEN2 leads to what deposits on histology?
Amylin/amyloidosis
Can be dx with Congo red stain
What is the mechanism by which hyperthyroidism increases metabolism?
Increases Na/K ATPase activity
A dexamethasone suppression test will suppress:
Entire HPA (i.e. CRH, ACTH, and cortisol levels will all be decreased)
Dex acts on ACTH in the anterior pituitary
Which 2 drugs can cause hypothyroidism?
Amiodarone
Lithium
Basic features of DeQuervain (subacute) thyroiditis?
Marked by granulomatous infiltration -> hypothyroidism
Painful
Gets better
Exogenous corticosteroids lead to _____ cortisol levels on labs.
LOW! HPA totally shut down and the exogenous glucocorticoids do NOT show up as cortisol.
GH binds to the nonreceptor tyrosine kinase ______ leading to dimerization and increased gene transcription of IGF-1.
JAK/STAT
Which lipid lowering drug (and class) leads to hypertriglyceridemia?
Cholestyarime (bile acid-resin binders)
How does Hashimoto’s appear on histology?
aka chronic lymphocytic thyroiditis:
Intense mononuclear infiltrates consisting of lymphocytes and plasma cells -> hence GERMINAL centers will be seen. Residual follicles are surrounded by Hurthle cells.
Glyburide and Glipizide are both sulfonylureas that put patients at risk for hypoglycemia, but which is worse? why?
Glyburide is longer-acting and thus has an increased risk of hypoglycemic events
