Physio Exam 5 Ch 17 18 19 20
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Describe the following five lung volumes: dead space, RV, IRV, ERV and VT. (ch17)
-Residual volume (RV) The amount of volume in the lung after maximal exhalation.
-Inspiratory reserve volume (IRV) The additional volume you can take in above the TV.
-Expiratory reserve volume (ERV) The amount of air that is forcefully exhaled below TV.
-Title volume (VT) The amount of air moved during nomad breathing, inspiration and expiration.
-Dead Space the volume of air that is inhaled but does not take part in gas exchange, either because 1 remains in conducting airways or 2 reaches the alveoli that are not perfused or poorly perfused.
Explain what happens with inspiration and expiration in terms of alveolar pressure, intrapleural pressure and air volume. (ch 17)
During inspiration the alveolar pressure decreases, pressure in the lungs is lower than atmospheric pressure, intrapleural pressure decreases, and air volume increases.
During expiration, the alveolar pressure increases(pressure in the lungs is greater an atmospheric, intrapleural pressure increases, and air volume deceases.
Explain the factors that influence alveolar gas exchange. (ch 18)
- Composition of inspired air-higher the altitude, the less oxygen.
- Alveolar ventilation
- -rate and depth
- -airway resistance
- -lung compliance
- Gas diffusion between alveoli and blood
- -surface area
- -diffusion distance
- a. barrier thickness
- b. amount of fluid
- Adequate perfusion of alveoli
Explain how carbon dioxide is carried in the blood. Be specific! (18)
CO2 diffuses out of cells into systemic capillaries-->7% of CO2 remains dissolved in the plasma-->about 1/4 of the CO2 binds to hemoglobin, forming carbaminohemoglobin--> 70% of the CO2 load is converted to bicarbonate and H+. Hemoglobin buffers to H+--> HCO3 enters the plasma in exchange for Cl- (chloride shift)-->at the lungs, dissolved CO2 diffuses out of the plasma-->by law of mass action, CO2 unbinds from hemoglobin and diffuses out of the RBC--> carbonic acid retain reverses, pulling HCO3 back into the RBC and converting it back to CO2.
How do chemoreceptors in the central nervous system respond to changes in carbon dioxide levels in cerebrospinal fluid? Be specific! (18)
peripheral and central chemoreceptors located in the medulla set the pace of ventilation. When arterial PCO2 increases-->CO2 crosses the BBB into the CSF, converts it to carbonic acid which dissociates to bicarbonate and H+, changing pH balance-->activates central chemoreceptors. -->receptors signal the control network (in medulla oblongata) to breathe faster
Explain and give examples of the four major functions of the nephron. Be specific about what part of the nephron performs each function. (19)
Filtration occurs in Bowman's capsule where blood turns into filtrate
Reabsorption occurs in the proximal tubule, Loop of Henle, distal tubule, and collecting duct. when substances of filtrate move from the lumen to the peritubular capillaries, like H2O being reabsorb in the Loop of Henle.
Secretion occurs in PCT, DCT, and CD. Removal of molecules from the blood to the lumen, like organic anions from blood to lumen in the PCT
Excretion is the removal of urine from the CD to the bladder.
How is the GFR autoregulated through tubuloglomerular feedback? (19)
GFR ↑-->flow through tubule ↑-->flow past macula densa ↑--> paracrine from macula densa to afferent arteriole constrict arteriole-->resistance ↑-->hydrostatic pressure ↓--> GFR↓
Explain the process or organic anion secretion. Be specific! (19)
Direct active transport, Na-K ATPase is used to maintain low intracellular Na-->Secondary active indirect active transport, dicarboxylate is brought in the tubule using the Na gradient + dicarboxylate cotransporter-->Tertiary indirect active transport, OAT is brought in the tubule from the basolateral membrane via dicarboxylate gradient-->Organic ions enter the lumen by facilitated diffusion.
Explain the role of vasopressin in regulating water reabsorption in the nephrons. How does it affect water pores? Be specific! (20)
Vasopressin binds to membrane receptor of the collecting duct-->receptor activates second messenger cAMP-->phosphorylation of intracellular proteins move AQP2 vesicles to apical surface-->Exocytosis of AQP2 into apical membrane-->now the cell is permeable to water via osmosis
Explain the role of aldosterone in regulating salt levels. How does it act on principal cells? Be specific! (20)
Aldosterone enters P cells by simple diffusion--> aldosterone binds to cytoplasmic receptor-->hormone -receptor complex initiates transcription in nucleus-->translation and protein synthesis makes new protein channels and pumps(ATP)-->aldosterone-induced proteins modulate existing channels and pumps-->result is increased Na+ reabsorption and K+ secretion
Explain the RAS pathway, the relationship between renin and angiotensin. Start with what triggers the release of renin and how that works and end with the production of Angiotensin II and its general affects on the body. (20)
Granular cell of afferent arteriole produce renin(enzyme) by 3 ways:
- 1. granular cells are directly sinsitiv to low BP, they respond by releasing renin.
- 2. sympathetic neurons, renin is released when cardiovascular control center senses low BP.
- 3. Paracrine feedback, when the macula densa senses a decrease in GFR and NaCl transport.
Renin converts inactive angiotensinogen
, into angiotensin I (ANG I)
When ANG I encounters angiotensin-converting enzyme (ACE)
in the blood, ANG I-->ANG II
- Remember the affects of low BP on body (5)
- -Cardiovascular CC in medulla- ↑ cardio response
- -hypothalamus-↑ vasopressin and thirst-->↑
- volume and maintain osmolarity
- -adrenel cortex-↑ aldosterone-->↑ Na reabsorption-->↑ volume to maintain osmolarity
- -proximal tubule-->↑ Na reabsorption-->↑ volume and maintain osmolarity
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