Physiology LabCon

8/6/2019 Physiology LabCon

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Aside from Epinephrine, onehormones released during stess

is Cortisol. Differentiate

Epinephrine from Cortisol withregards the following:a.control of secretion,

b. mechanism of actionc. effect on cells


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Epinephrine

Control of secretion Integral part of fight or flight response

-

-


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Epinephrine

Stimulus to sympathetic nervous system via splanchnic nerve

Stimulation of cholinergic preganglionic fibers

Acetylcholine

Nicotinic acetycholinereceptors


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Epinephrine

Depolarization of chromaffin cell membrane

Increased permeablity of membrane to sodium

Influx of calcium ions through voltage-gated calcium channel

Exocytosis of secretory granules

Epinephrine (bloodstream)


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Epinephrine


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Epinephrine

Simple feedback loop

Sensor Hormone Target 1 Other hormone

Target 2 or metabolite

exert negative feedback to down-regulate its own synthesis at the pre-synaptic alpha-2 adrenergic receptor

Epinephrine synthesis is under control of CRH-ACTH-Cortisol axis1. ACTH stimulates synthesis of Dopamine and Norepinephrine

2. Cortisol upregulates PNMT in chromaffin cells


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Epinephrine

Mechanism of ActionEpinephrines actions mediated through adrenergic receptors: 1, 2,

3 and 1, 2

Epinephrine does not cross cell membrane

binds to cell surface receptors adrenergic receptors

1. Binds to 1 receptors of liver cells

Activates inositol-phospholipid signaling pathway

Activates heterotrimeric Gq protein coupled to Phospholipase C

Second messenger: Calcium and/or Phosphoinositides (IP3,DAG)

Signaling phosphorylation by activation of Protein kinase C:

- Glycogen synthase inactivation

- Phosphorylase kinase activation

Activation of glycogen phosphorylase glycogenolysis


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Epinephrine

2. Binds to -adrenergic receptors of liver and muscle cells

Activates cAMP signaling pathway

Activates heterotrimeric Gs protein coupled to Adenylyl cyclase

Second messenger: cAMP

Signaling phosphorylation by activation of Protein kinase A:- Glycogen synthase inactivation

- Phosphorylase kinase activation

Activation of glycogen phosphorylase glycogenolysis


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Epinephrine


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Epinephrine

Effects on cells

Effects on metabolism

Gluconeogenesis and receptors on liver cells

Glycogenolysis receptors on liver and muscle cells Glucagon secretion receptors

Insulin secretion on cells

Lipase activity, Lipolysis plasma free fatty acids receptorson muscle and liver leading to oxidation


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Epinephrine

Effects on Cardiovascular system

Heart Rate 1 receptor

Cardiac Contractility 1 receptor

Conduction velocity 1 receptor

Systolic blood pressure Cardiac output

Arteriolar dilatation 2 receptor


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Epinephrine

Effects on other systems

muscle K+ uptake - receptors

muscle relaxation - receptors - Gastroinestinal

- Urinary - Bronchial

Dilatation of pupils

Modulate ADH release receptors stimulate -- receptors inhibit

Renin release - receptors


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EpinephrineRecept

or Type

Linked

Enzyme

Second

Messenger

Effects

1 PLC IP3andDAG

Binds to 1 receptors of liver

cellsGlycogenolysis

GluconeogenesisDilation of pupils

2 Adenylcyclase

cAMP Platelet aggregation1 Adenyl

cyclasecAMP Cardiac contractility

Heart rateGlycogenolysis

2 Adenyl

cyclase

cAMP Vasodilation in muscle and

liver cellsMuscle relaxationGluconeogenesisLipolysisGlycogenolysis

3 Adenylcyclase

cAMP LipolysisGlycogenolysis


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Cortisol

Control of Secretion Synthesis and secretion stimulated by ACTH (Corticotrophin)

Release of ACTH is stimulated by Corticotrophin-releasing hormone(CRH)

CRH

G protein receptor ( G alpha-s) cAMP Corticotrophs

Active PKA


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Cortisol

Activated Ca

+2

channels

Influx of Calcium Corticotrophs

Exocytosis of ACTH

Melanocortin-2 receptor coupled to G protein adrenal

medulla Adenylyl cyclase


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Cortisol

cAMP active PKA

adrenal medulla

Enzymes converting cholesterol to pregnenolone synthesis of Cortisol

Subsequent release of Cortisol from zona fasculata

Secretion of cortisol exhibits diurnal variation

Peaks early morning hours

Dimnishes late in afternon and early evening


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Cortisol


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Cortisol

Mechanism of Action Cortisol(lipid soluble) diffuses to cell membrane intracellular

receptor Glucocorticocoid receptors (GR)

GR (unbound form) is complexed to Heat Shock protein (HS

protein) HS protein dissociates from Cortisol-GR complex

Cortisol-GR complex translocate to nucleus

Cortisol-GR complex associates with Glucocorticoid responseelements (GRE)

GRE induces or represses transcription genes Cortisol or transcription alter mRNA synthesis


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Cortisol


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Cortisol

Effects on cells

Effects on metabolism

Gluconeogenesis glucose utilization

Deamination of AA by hepatocytes glucose transport to fat cells Conversion of AA to glucose protein stores in all cells

Plasma and liver proteins except liver cells

Fatty acid mobilization from fat cells

FFA plasma concentration

Ketogenesis

Fatty acid oxidation


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CortisolTissue/ Organ/

Organ System

Effect of Cortisol

Muscle maintains contractility and work performance of cardiacand skeletal muscle mass

Bone increases bone resorption

ConnectiveTissue inhibits collagen synthesis

Vascular System required for maintenance of normal blood pressure

Kidneys increase GFR

CNS modulates excitability, behavior and mood of individuals

Fetus Facilitate maturation of fetus

Inflammation andImmune response

Inhibit inflammatory and immune response


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Discuss the role ofepinephrine in the utilization of

glucose during exercise


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Role of Epinephrine in Exercise

During exercise, net effect of epinephrine shunt blood toward theactive muscles while maintaining coronary and cerebral bloodflow

Delivery of substrate for energy production to the critical organs

Increase circulating blood glucose through:

Gluconeogenesis on liver cells Glycogenolysis on liver and muscle cells Glucagon secretion

Insulin secretion Lipase activity, Lipolysis plasma free fatty acids on muscle and

liver leading to oxidation Calorigenesis Glucose utiization


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Role of Epinephrine in Exercise


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Give the expected results and

its physiologic basis of theexperiment. Interpret the

actual results and explain anydiscrepancy with the expectedresults. Give the conclusion of

the experiment


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Expected Results

Blood sugar level before and after 10minutes after injection of epinephrine

Increase in blood sugar level

Blood sugar level before and after 10minutes after injection of saline

Increase in blood sugar level

Blood sugar level first and second sampleof rat C (no injection given)

No change in blood sugar level


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Expected Results

Liver Glycogen of Rats A,B,C

Decrease glycogen in Rat A

No change in glycogen for Rats B & C

Muscle Glycogen of Rats A, B, C Decrease glycogen in Rat A

No change in glycogen for Rats B & C


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Actual Results

Mean blood sugar levels between 0, 10 min and 20 min were equalamong the 3 groups.

ANOVA

Sum ofSquares df MeanSquare F Sig.0min Between

Groups300.536 2 150.268 .049 .953

WithinGroups

102213.687 33 3097.384

Total 102514.222 35

10min BetweenGroups

4020.169 2 2010.084 .725 .492

WithinGroups

91532.270 33 2773.705

Total 95552.439 35

20min Between

Groups

7382.682 2 3691.341 .965 .391

WithinGroups

126177.660 33 3823.565

Total 133560.342 35


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Actual Results

T-test

Epinephrine Group

Paired Samples StatisticsMean N Std.

DeviationStd. ErrorMean

Pair 1 0min 97.950 12 51.4254 14.845210min 122.117 12 47.7836 13.7939

Pair 2 10min 122.117 12 47.7836 13.793920min 127.767 12 63.7821 18.4123

Paired Samples CorrelationsN Correlatio

nSig.

Pair 1 0min &10min

12 .748 .005

Pair 2 10min &20min

12 .787 .002


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Actual resultsPaired Samples Test

Paired Differences t df Sig. (2-tailed)

95% Confidence Interval of theDifference

Mean Std.Deviation

Std.ErrorMean

Lower Upper

Pair1

0min -10min

-24.1667

35.409310.2218-46.6646

-1.6687 -2.364

11 .038

Pair2

10min -20min

-5.6500

39.441011.3856-30.7096

19.4096-.496 11 .629

There was a significant difference between the mean blood glucose levelsbefore and 10 minutes after epinephrine injection but none between 10

and 20 minutes after epinephrine injection.


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Actual Results

Descriptive Statistics

N Minimum Maximum Mean Std.Deviation0min 12 38.0 314.0 97.367 73.9668

10min 12 51.0 293.0 100.617 63.7832

20min 12 71.0 371.0 120.717 83.3079

Valid N

(listwise)

12

Paired Samples Correlations

N Correlation

Sig.

Pair

1

0min &

10min

12 .918 .000

Pair2

10min &20min

12 .955 .000

T-test

Saline Group


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Actual Results

Paired Samples TestPaired Differences t df Sig. (2-

tailed)95% Confidence Interval of theDifference

Mean Std.Deviation

Std.ErrorMean

Lower Upper

Pair1

0min -10min

-3.2500

29.5433 8.5284 -22.0209 15.5209 -.381 11 .710

Pair2

10min -20min

-20.1000

29.3512 8.4730 -38.7489 -1.4511 -2.37211 .037

There was no significant difference between the mean blood glucoselevels before and 10 minutes after saline injection, however, asignificant difference was noted between 10 and 20 minutes after

saline injection.


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Actual Results

Paired Samples Statistics

Mean N Std.Deviation

Std. ErrorMean

Pair 1 0min 91.550 12 34.3000 9.9015

10min 98.883 12 44.3796 12.8113

Pair 2 10min 98.883 12 44.3796 12.8113

20min 94.483 12 21.5020 6.2071

Paired Samples Correlations

N CorrelationSig.

Pair 1 0min & 10min 12 .826 .001

Pair 2 10min &20min

12 .741 .006

T-test

Control Group


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Actual Results

There was no significant difference in the mean bloodglucose level before and 10 minutes later and between 10 and20 min later in the control group.

Paired Samples Test

Paired Differences t df Sig. (2-tailed)95% Confidence Interval of the

Difference

Mean Std.

Deviation

Std.

ErrorMean

Lower Upper

Pair1

0min -10min

-7.3333

25.1125 7.2493 -23.28908.6224 -1.012

11 .333

Pair2

10min -20min

4.4000

31.9025 9.2094 -15.869924.6699 .478 11 .642


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Discrepancies

Results may be affected by the following:

Subject mice might be agitated too much causingincrease release of epinephrine

Clerical errors e.g.: miscalculation, errors in weighing

Isolated glycogen was not completely dried causingdiscrepancy in weighing


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Conclusion

Epinephrine (Adrenaline) Stimulates glucose production and inhibits glucose use

Stimulates lipolysis and ketogenesis

Inhibits secretion of insulin

Stimulates glycogenolysis on liver and muscle cells shunt blood toward the active muscles while maintaining coronary

and cerebral blood flow

Provide energy substrates to critical organs e.g. Brain, heart.

Net effect: plasma glucose, FFA and ketoacids

Adrenaline Rush

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Physiology LabCon