physiology lab

Question 1

What e the events that occur during each phase of the action potential in the SA node

Answer 1

1. Na+ coming in, also ca++ in through leaky channels
2. Fast depolarization Ca++ influx through voltage gated channels
3. Fast repolarization K+ influx via voltage gated channel

Question 2

What are the events that occur during each paste of plateau action potential

Answer 2

1. Slow depolarization - Na+ in via leaky channels
2. Rapid depolarization Na + in via voltage gated channels
3. Plateau Phase- Ca++ influx , K+ bleak channels (n ligand)
4. Rapid depolarization- K+ efflux via voltage gated channels
5. Slow depolarization – Na+ influx leaky

Question 3

Compare and contrast the major physiological characteristics of the Sa node and av nodes and the specialized conductive fibers

Answer 3

SA node – resting potential is closer to threshold
Resting potential= -60 to -50mV
HR= 60- 100
AV node — slower in conduction -fewer gap junctions – smaller in diameter size(greater resistance)
Resting potential = -85 to -75mV
HR= 40-60
Ventricle - resting potential= -105 to -95 mV
HR= 20-40

Question 4

What are the effects of hyperkalemia, Hypercalcemia and hypocalcemia on cardiovascular function? What are the molecular events that cause these problems

Answer 4

Hypercalcemia— excess ca++ in blood= stronger contractions = it will block opening of voltage gated Na+ channels ( blocks neurons)
Hypocalcemia- Less ca in blood = weaker contractions=causes spontaneous opening of Na+ channels (muscle tetany)
Hyperkalemia- increase K= outside the cell= more K+ inside the cell= making the cell less negative= weaker contraction

Question 5

Hyperkalemia

Answer 5

More K+ outside the cell= less force inside the cell= less negative
Less Ca+ entry inside cell
Weaker contractions= slow contractions = irregular rhythm =AV block
Less negative resting potential= weaker contraction

Question 6

The roles of the sympathetic and parasympathetic nervous system in regulating the heart. Describe in detail how Ach and Norep alter cardiac functions

Answer 6

Parasympathetic effects only rate
- Ach binds to ligand gated channels - increases K+ permeability = decreases heart rate

Sympathetic - effects strength and rate

 - norep= hyperpolarizes membrane potential closer to threshold 
- increases Na+ permeability - increaseHR 
 - more Ca++ channels available -increases strength

Question 7

Define Right (RAD) and left axis deviations (LAD) detected with ECG’s . What are the normal body variations that may cause their appearances and what pathological conditions might be responsible?

Answer 7

RAD- picking up more electrical activity on right ( 90- 180)
- right vent. hypertrophy
- increase resistance to blood flow in pulmonary circuit
- People who have adapted to living at high altitude
LAD- 0 to -90 (-270)
- occurs in obesity, pregnancy
- can occur lying down
- enlarged left ventricle
- loss of right ventricle muscle cells depolarizing

Question 8

Extreme RAD

Answer 8

180-270

• most serious not good for physical activity
• muscle left decreased at same time when right muscle increases
• result from congested heart failure
• leads to pulmonary edema

Question 9

Ohm’s law How pressure differences and resistance affect fluid flow

Answer 9

the pressure differential between the pressure at the origin of the vessel and the pressure at the other end of the vessel . the difference creates a resistance as a result of friction between the flowing blood and the intravascular endothelium along the inside of vessel

Question 10

Poissseuille’s law how radius, resistance, length, viscosity turbulence and hematocrit affect blood flow

Answer 10

Turbulence: when rate of blood flow becomes too great, passes by an obstruction in a vessel
Radius:

Question 11

Factors that affect cardiac output and total peripheral resistance

Answer 11

Cardiac output= arterial pressure / TPR
when total peripheral resistance decreases, the cardiac output increases
when total peripheral resistance increases the cardiac output decreases

Question 12

Define Mean arterial pressure (MAP)

Answer 12

average pressure pushing blood through systemic circulatory system

Question 13

the equations for estimating MAP at rest and during activity

Answer 13

At rest: MAP= 1/3(SP-DP)+DP

Activity: MAP= SP+DP/2

Question 14

Blood pressure = Cardiac output X ….
Blood pressure= ___ X__ X___
Blood pressure=__X ______X ___

Answer 14

TPR
HR X SV X TPR
HR X (EDV- ESV) X TPR

Question 15

Resistance = 8nL/ ?

Answer 15

r ^4

Question 16

Blood Flow= P1-P2/ ?

Answer 16

R

Question 17

Cardiac Output

Answer 17

SV X HR

Question 18

Stroke Volume=

Answer 18

EDV-ESV

Question 19

Intrinsic control

Answer 19

Sa node/ AV node ectopic focus 
increase stretch of right atrium 
increase leakiness SA node 
increase HR
increase venous return 
increase peripheral tissues 
increase vasodilators

Question 20

Extrinsic Control

Answer 20

Bainbridge reflex
increase pressure in R atrium
increase sympathetic
baroreceptors

Question 21

what is the Baroreceptor reflex:
- variable measured
- sensory receptors
- intergrating center
- efferent pathway 
response of the effectors

Answer 21

• initiated by stretch receptors - increased BP
• Carotid sinus and aortic arch
• signals to CNS
• feedback ANS
• reduce arterial pressure and decrease HR
• Blood volume decreased

Question 22

Bainbridge reflex

Answer 22

Stretch receptor of right atria
transmits back through vagus nerves and sympathetic to increase HR
Bood volume increased
venous return is increased- increase pressure on right atrium - decreased atrial pressure - brings more blood in from vena cava

Question 23

Action of ADH

Answer 23

-vasoconstriction
- increase HR
-
- increase BP
- reabsorb water
decrease osmotic pressure

Question 24

Aldosterone Action

Answer 24

• increase Na+
• excrete K+
• increase BP

Question 25

Angiotensin II

Answer 25

• vasoconstriction

- increase BP

Question 26

Atrial Natriuretic Hormone

Answer 26

• decrease BP
• Vasodilation
• decrease Na+