Module 6: Cardiovascular Flashcards Preview

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Flashcards in Module 6: Cardiovascular Deck (237)
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181

ADH secretion is inhibited by:

A stretch in atrial wall caused by increased Venous Return due to increased blood volume

182

Target organs of VASOPRESSION (ADH)

- Smooth muscles of arterioles
- Kidneys (Distal Convoluted Tubule and Collecting Duct)

183

Effects of VASOPRESSION (ADH)

- Vasoconstriction --- increased TPR
- Increased permeability of DCT and CD to water
* ↑ Water reabsorption
* ↑ Plasma volume
* ↑ CO

184

CHEMORECEPTORS in the CAROTID and AORTIC BODIES

• Located along aortic arch and near the bifurcation of common carotid arteries
• Important at BP below 80 mmHg
• Have very high rates of oxygen consumption
• Sensitive to oxygen lack, carbon dioxide and hydrogen excess

185

- an enzyme that catalyzes the conversion of Angiotensinogen (liver) to Angiotensin I
- secretion increased when ABP falls or ECF volume reduced

RENIN

186

- catalyzes conversion of Angiotensin I to II primarily in the lungs

ACE (Angiotensin Converting Enzyme)

187

- block conversion of Angiotensin I to II, thus lowers ABP
- act on β2 receptors to produce the cough that is an annoying side effect in 20% of patients treated with ACE inhibitors

ACE INHIBITORS (Ex. Captopril)

188

- vasoconstrictor, increase SP or DP
- 4 to 8 times as active as NE
- its pressor activity is decreased in SODIUM depleted individual and in patients with Cirrhosis
- acts directly on adrenal cortex (ZONA Glomerulosa) to increase secretion of aldosterone
- acts on the brain to decrease the sensitivity of he baroreceptor reflex
- acts on the brain to increase water intake and increase secretion of vasopressin and ACTH

ANGIOTENSIN II (Hypertensin or Angiotonin)

189

- has about 40% of the pressor activity of Angiotensin II, but 100% of the aldosterone stimulating activity
- is the natural aldosterone – stimulating peptide while Angiotensin II is the natural BP – regulating Peptide

ANGIOTENSIN III

190

- increases SODIUM reabsorption by the Renal distal convoluted tubule
- increases water reabsorption
*Thus, increasing ECF volume (plasma volume)
*Increase total blood volume
*Increase cardiac output
- Without the RAAS, the effect of excessive salt intake on arterial pressure is 10 times as great

ALDOSTERONE

191

- Recording electrical activity of the heart using electrodes placed on skin surface
*Physiologic basis  Human ECF is NaCl-based, making it a good conductor of electricity
- Provides indirect information about cardiovascular function

Electrocardiography

192

- Deflection produced by atrial depolarization
- Does not include atrial repolarization, which is “buried” in the QRS complex

P Wave

193

- Interval from the start of the P wave to the beginning of the QRS complex
- Represents the time required for SA node impulse to travel through the conduction system
- Normal value of 0.12 - 0.20 sec

PR Interval

194

Changes in PR Interval

- Varies with conduction velocity through the atrioventricular (AV) node
–if AV nodal conduction decreases (as in heart block), the PR interval increases

- Decreased (i.e., increased conduction velocity through AV node) by stimulation of the sympathetic nervous system

- Increased (i.e., decreased conduction velocity through AV node) by stimulation of the parasympathetic nervous system

195

Represents the time from the end of atrial depolarization to the start of ventricular depolarization

PR Segment

196

- Represents ventricular depolarization
- Atrial repolarization is buried in the QRS complex

QRS Complex

197

QRS Complex

Q – first negative wave
R – first positive wave
S – first negative wave after an R wave

198

- Interval from the beginning of the Q wave to the end of the T wave
- Represents the entire period of ventricular depolarization and repolarization
- Normal value of 0.44 second

QT Interval

199

- Segment from the end of the S wave to the beginning of the T wave
*represents time from end of ventricular depolarization to the start of ventricular repolarization

- Considered an isoelectric segment

ST Segment

200

- Deflection produced by ventricular repolarization
- Most variable waveform

T Wave

201

Waveform: What It Represents

P WAVE - Atrial depolarization
QRS COMPLEX - Ventricular depolarization
T WAVE - Ventricular repolarization

202

Leads

- The ECG examines the electrical activity of the heart at various perspectives using 12 different leads.
- Lead – an electrical picture of the heart that makes use of 2 electrodes.

203

Types of ECG Leads

1. 3 Bipolar Limb Leads
2. 3 Augmented Unipolar Leads
3. 6 Precordial or Chest Leads

204

- Bipolar means that the ECG is recorded from two electrodes on the body

Bipolar Limb Leads

205

Lead I

Negative Terminal: Right Arm
Positive Terminal: Left Arm

206

Lead II

Negative Terminal: Right Arm
Positive Terminal: Left Leg

207

Lead III

Negative Terminal: Left Arm
Postitive Terminal: Left Leg

208

- States that: The electrical potential of any limb equals the sum of the other two
- Positive and negative signs of leads must be observed

EXAMPLE:
–If lead I = 1.0 mV, Lead III = 0.5 mV, then Lead II = 1.0 + 0.5 = 1.5 mV

Einthoven’s Law

209

- Designated as V1 to V6
- Very sensitive to electrical potential changes underneath the electrode

Chest or Precordial Leads

210

Placement of Precordial Leads

V1- 4th Intercostal Space (ICS) Right parasternal border
V2 - 4th ICS Left parasternal border
V3 - between V2 and V4
V4 - 5th ICS Left Mid Clavicular Line
V5 - 5th ICS Left Anterior Axillary Line
V6 - 5th ICS left Mid Axillary Line