Physiology Week 3

Question 1

List the 4 Components of Gastric Juice:

Answer 1

1. HCl
2. Pepsinogen
3. Intrinsic Factor
4. Mucous

Question 2

What is the only ESSENTIAL component of gastric juice and why?

Answer 2

Intrinsic Factor: Necessary for absorption of Vitamin B12 in the Ileum

Question 3

4 Types of cells in Oxyntic glands and their secretions:

Answer 3

1. Surface Epithelium: Alkaline, visible mucous
2. Mucous Neck Cell: Clear Mucous
3. Parietal (Oxyntic) Cell: HCl and Intrinsic Factor
4. Chief (Peptic) Cell: Pepsinogen

Question 4

Achlorhydria:

Answer 4

Decreased Parietal (Oxyntic) Cell mass and low HCl secretion due to lack of Intrinsic Factor, ultimately resulting in Pernicious Anemia.

Question 5

Describe G-Cell secretion:

Answer 5

G-Cells secrete Gastrin into the CIRCULATION, not into the ducts of the pyloric glands, and it travels to act on Parietal Cells to release HCl and Intrinsic Factor.

Question 6

Where in the stomach are each of the types of glands/cells located?

Answer 6

1. Gastric (Oxyntic) Glands: BODY of stomach
   
   • Parietal (oxyntic) Cells: HCl and Intrinsic Factor
   • Chief (peptic) Cells: Pepsinogen
2. Pyloric Glands: ANTRUM of stomach
   
   • G-Cells: Gastrin into CIRC.
   • Mucous Neck Cells: Mucous, HCO3-, Pepsinogen

Question 7

What are the 3 main functions of HCl in the stomach?

Answer 7

1. Activate Pepsinogen
2. Create optimal environment for Pepsin
3. Kill Bacteria

Question 8

The process of HCl secretion gives an overall net secretion of ______ across the _____ membrane, and an overall net absorption of ______ across the ______ membrane.

Answer 8

1. Secrete HCl –> Luminal Membrane

2. Absorb HCO3 –> Basolateral Membrane

Question 9

Describe the function of Omeprazole:

Answer 9

To treat GERD, this drug inhibits the H+-K+-ATPase at the luminal membrane of parietal cells to prevent HCl formation in the stomach.

Question 10

What cells release Histamine and how does it elicit its effect?

Answer 10

1. ECL cells adjacent to Parietal cells in stomach body.
2. Hist binds H-2 receptor which uses a G-alpha-S subunit to increase cAMP and ultimately activate the
   H+-K+-ATPase to release H+.

Question 11

How is the activity of ACh different in the stomach from that of Histamine?

Answer 11

ACh from the Vagus Nerve binds an M-3 receptor on parietal cells and activates a G-alpha-Q subunit to increase IP3 and ultimately activate the
H+-K+-ATPase to release H+.

Question 12

How is the activity of Gastrin different in the stomach from that of Histamine?

Answer 12

Gastrin from the G-Cells binds a CCK-B receptor on parietal cells and activates a G-alpha-Q subunit to increase IP3 and ultimately activate the
H+-K+-ATPase to release H+.

Question 13

Explain the function of the 3 blockers of HCl formation/secretion in the stomach:

Answer 13

1. Atropine = M-3 Antagonist
2. Tagamet/Zantac = H-2 Antagonist
3. Omeprazole = H+-K+-ATPase Pump Inhibitor

Question 14

Cephalic Phase ACh secretion:

1. Stimuli: ____
2. Both Mechanisms: ______

Answer 14

1. Smelling, chewing, tasting, etc.
2. Direct: (Vagus) ACh –> M-3 receptor
   Indirect: (Vagus) GRP –> G-Cell –> Gastrin

Question 15

Main Difference between Myocardial and SA Node Action Potentials:

Answer 15

SA Node Action Potentials have NO resting membrane potential, they are dynamically changing.

Question 16

How is the frequency of SA action potentials (and therefore HR) increased?

Answer 16

By increasing the rate of depolarization via the Funny Sodium Channels to reach threshold faster.

Question 17

Between which two conducting structures of the heart does the “inter-nodal” delay occur?

Answer 17

The AV Node and Bundle of His

Question 18

Explain Ca2+ induced-Ca2+ release:

Answer 18

Membrane depolarization in cardiomyocytes triggers the opening of voltage-gated L-type Ca2+ channels. That influx of Ca2+ triggers the opening of Ryanodine Receptors in the cell which release stored Ca2+ into the cytosol to allow contraction.

Question 19

What are the two mechanisms of removing intracellular Ca2+ to stop cardiomyocyte contraction?

Answer 19

1. Ca2+-ATPase: Pumps Ca2+ back into storage.

2. Na+/Ca2+-Exchanger: Pumps Ca2+ out of the cell.

Question 20

What receptor do Epi/NE bind in cardiomyocytes?

Answer 20

B-1 Receptors

Question 21

How is Mean Arterial Pressure calculated?

Answer 21

MAP = Diastolic + 1/3 Pulse Pressure

Question 22

Where are Baroreceptors found in the body?

Answer 22

On Arteries that supply the Brain and the Heart:

• Brain: At Carotid Sinus
• Heart: At Aortic Arch

Question 23

Equation for BP:

Answer 23

BP = SV x TPR

Question 24

Equation for CO:

Answer 24

CO = HR x SV

Question 25

What is the flow sensor of the kidney? How does it measure flow?

Answer 25

1. The Juxtaglomerular Apparatus

2. Detecting the amount of salts passing through the glomerulus.

Question 26

Describe the 5 Functions of Angiotensin 2:

Answer 26

1. Activates Thirst Center –> Inc. AVP secretion
2. Inc. Vasoconstriction –> Inc. TPR –> Inc. BP
3. Dec. GFR –> Dec. Urine Output
4. Inc. Reabs. of filtrate at Nephron
5. Inc. Aldosterone prod. at Adrenal glands

Question 27

Function of Renin:

Answer 27

Converts Angiotensinogen –> Angiotensin 1

Question 28

Function of ACE (in lungs):

Answer 28

Converts Angiotensin 1 –> Angiotensin 2

Question 29

The R.A.A.S. activity is a graded response that can be altered by ________.

Answer 29

The Sympathetic Nervous System output in response to baroreceptor stretch at the nephron.

Question 30

Stenosis:

Answer 30

Narrowing of a heart valve causes turbulence to the blood flow.

Question 31

Equation for Ejection Fraction:

Answer 31

SV/EDV

Question 32

The ______ is also known as the Total ventricular Volume.

Answer 32

EDV

Question 33

Equation for Flow:

Answer 33

Q = k(P1-P2) 
OR
Q = (P1-P2) / R
OR
CO = MAP/TPR