Homeostasis Flashcards
Another name for vasopressin is …
Antideuretic Hormone (ADH)
What are the 3 kinds of vasopressin receptors?
V1A, V1B, V2
At which osmolality is vasopressin secretion inhibited?
285mOsm/kg
What’s the difference in signalling between V1A and V1B receptors and V2 receptors?
V1A and V1B use hydrolysis of phosphatidylinositol to increase Calcium levels
V2 receptors use G proteins to increase cAMP levels
State the different roles of V1A, V1B and V2 receptors in the mechanism of vasopressin.
V1A - cause vasoconstriction to raise blood pressure
V1B - found in anterior pituitary gland, stimulate release of adrenocorticoprotic hormone (ACTH)
V2 - initiate release of aquaporin 2 water channels into cell membrane to make it more permeable to water
Where is vasopressin stored?
posterior pituitary gland
Which factors influence vasopressin secretion?
- Tonicity of plasma (higher tonicity increases ADH secretion)
- ECF Volume (lower ECF increases ADH secretion)
- Stress (increase ADH)
- Pain (increase ADH)
- Nausea and Vomitting (increase ADH)
- Standing (increase ADH)
- Alcohol (decreases ADH)
Define homeostasis
The maintenance of a relatively constant internal environment within a narrow range
How is homeostasis different from homeodynamics?
In homeodynamics, as the body changes, the integration center sets new set points (‘normals’). Homeostasis assumes the body remains constant.
What is the integrating center?
evaluates sensory information and initiates a response designed to bring the deviation back to the set point
Which organelle is involved in Tay-Sach’s disease?
Lysosomes
In Tay-Sach’s disease why do gangliocides accumulate around axons and what are the consequences?
Because lysosomes have enzymes that break down lipids (lipases). The consequences include blindness, deafness, paralysis, and seizures.
Damage to which organelle is responsible for Achondrogenesis Type 1A?
The Golgi Apparatus
What happens in Achondrogenesis so that patients have small limbs and poorly formed spine?
The golgi apparatus is not packaging or transporting cell ‘secretions’ so body’s needs not adequately met.
Define osmosis
The net movement of water from areas of low to high concentration across a semi-permeable membrane.
How do V1B receptors affect secretion of vasopressin?
V1B receptors stimulate release of adrenocorticotropic hormone which then causes increase in secretion of cortisol. Cortisol acts as a dieuretic by making kidneys to absorb sodium. When excess sodium is absorbed, then vasopressin secretion increases.
What’s another name for V1B receptors?
V3 receptors
What are the causes of hyponatremia?
- Excess loss of Na+ without replacement (ex: diarrhea, sweating, vomitting) of Na+ but taking alot of water
- Addison’s disease in which aldosterone and cortisol decrease and kidneys unable to conserve Na+
- Excess secretion of antideuretic hormone (vasopressin) causes kidneys to absorb too much water
How are fluid balances assessed?
Via blood tests (sodium, potassium, chloride, bicarbonate, blood urea nitrogen), observation (ex: dry lips), and by taking vital signs.
What is hyponatremia?
Serum sodium levels of less than 135mEq/L
What is the half-life of vasopressin?
18 mins
Which heart chamber is affected in left-sided heart failure?
The left ventricle.
How does left-sided heart failure lead to edema?
Blood is not being pumped to the rest of the body because the left ventricle is not working (so the cells are lacking nutrients which can cause Na/K pumps to malfunction leading to intracellular edema), and blood backs into the lungs leading to fluid buildup and shortness of breath.
Which heart chamber malfunctions in right-sided heart failure?
The right ventricle.
How does the right ventricle direct blood?
Directs deoxygenated blood from heart to lungs
How does right-sided hear failure lead to edema?
Blood backs into the veins, increasing capillary pressure and leading to extracellular edema.
At which Na+ level is acute hyponatremia reached?
Na+ < 120 mEq/L
What is the maximum rate you can administer hypertonic fluids to an acute hyponatremic patient? Why?
no more than 10-12 mEq/L per day
Because it interferes with the brain’s ability to hold in solutes and can lead to permanent brain damage or death.
In which scenario should you think twice before administering hypertonic fluids to hypotonic patients?
- If they have increased risk of rising intracranial pressure.
- If they are hypovolemic (excess blood loss/from extracellular fluid compartment).
A 5% Dextrose in Lactated Ringer’s solution is…
Hypertonic
Why must patients given hypertonic solutions be very closely monitored?
Because it can easily cause pulmonary edema.
What is the homeostatic role of the renin-angiotensin system?
Regulation of blood pressure and fluid balance
What is the relationship between the renin-angiotensin system and aldosterone?
Renin released by kidneys stimulates synthesis of angiotensin in blood and body tissues. Angiotensin then stimulates release of aldosterone from adrenal cortex.
Aldosterone is released by…
the adrenal cortex
State 3 factors affecting the release of renin.
- sympathetic innervation (via Beta1-adrenoreceptors)
- Hypotension in renal arteries
- Low sodium levels in distal convoluted tubules
Where are the Beta1-adrenoreceptors located in the kidney? What is the their function?
In the Juxtoglomerular cells. They respond upon stimulation by causing release of renin.
