Response to Exercise and Stress

Question 1

Neural regulation - even anticipation of exercise elicits____. This will continue increasing as exercise begins and increases.

Answer 1

• Increased sympathetic activity –> increase blood flow
  
  • Increased HR
  • Increased contractility
  • Venoconstriction to increase resistance in the inactive regional vascular beds
• Decreased parasympathetic activity

Question 2

As you increase exercise, cardiac output, bp, and oxygen consumption also increase.

Total peripheral resistance _creases

Answer 2

Despite systemic vasoconstriction, total peripheral resistance decreases as local factors promote vasodilation in the active muscles and heart.

Question 3

During exercise, skeletal muscle beds that are active will see a dramatic vasodilation as what metabolic factors build up locally?

Answer 3

K+

adenosine

H+

Question 4

Mechanisms are in place to maintain proper supply to ___ during exercise. This occurs via a weak ___ and a strong ___.

Answer 4

Brain and other critical organs (like heart)

Weak sympathetic response

Strong myogenic response

Question 5

Exercise has what impact on the vascular function curve?

Answer 5

UPWARDS because of net vasodilation and net decrease in total peripehral resistance.

Ultimately, cardiac output is increased

Question 6

Describe what happens to blood flow to the skin during exercise.

Answer 6

1. Increased sympathetic activity reduces blood flow to the skin.
2. As body temp rises, cutaneous blood flow increases to perform heat exchange.
3. As you then approach max O₂ uptake, cutaneous blood flow is reduced again to shunt O₂ to the active muscles.

Question 7

bradykinin is associated with

Answer 7

mediating cutaneous circulation

Question 8

2 aspects of the venous system that enhance blood flow during exercise

Answer 8

Sympathetic activation –> venoconstriction of capacitance vessels increases preload

Skeletal muscle contraction & deeper respiration compresses veins to pump it forward

Question 9

What impact does exercise have on the baroreceptor reflex?

Answer 9

Exercise increases bp -> baroreceptor maintains blood pressure at the new “exercise induced” set-point

Ex) Increasing exercise will cause vasodilation –> drops total peripheral resistance –> baroreceptor reflex keeps the bp up despite this

Question 10

How does severe exercise cause acute distress?

Answer 10

• Heart rate maxes out (~180bpm) and stroke volume plateaus
• Sympathetic vasoconstriction dominates over temperature regulation –> reduced skin circulation --> you overheat

Question 11

Post exercise

Answer 11

Sympathetic drive drops, returning cardiac output to normal

Total peripheral resistance stays low as vasodilators take longer to wash out

Bp drops and the baroreceptor reflex stabilizes it.

Question 12

Two factors that limit exercise performance (training & conditioning)

Answer 12

O₂ utilization & O₂ supply*

Question 13

The skeletal muscles of athletes have better O₂ utlization because

Answer 13

• increased capillary density
• mitochondria
• ATPase activity

Question 14

Describe autonomci tone in highly trained athletes

Answer 14

High parasympathetic tone

Low sympathetic tone

–> lower resting heart rate & lower peripheral resistance

Question 15

What allows athletes to achieve greater O₂ delivery to tissues with smaller increases in heart rate?

Answer 15

Greater stroke volume –> better O₂ delivery

Question 16

Hemorrhagic Shock is the body’s response to rapid blood loss, which causes

Answer 16

decreased cardiac output and blood pressure

–> activates compensatory mechanisms to raise the bp

If prolonged (3-4hrs), decompensatory mechanisms cause further drops in bp and ultimately death

Question 17

Compensatory mechanisms of hemorrhagic shock include

Answer 17

• baroreceptor reflexes - 1st to activate
• chemoreceptor reflexes
• criculating vasoconstrictors
• reabsorption of tissue fluid
• renal salt & water conservation
• cerebral ischemia responses

Question 18

Hemorrhagic shock’s impact on baroreceptor reflex

Answer 18

• Drop in pressure causes a drop in baroreceptor activity
  
  • –> increased sympathetic tone
  • –> increase in HR, contractility (CO), vasoconstriction, and venoconstriction.
    
    • Kidneys override the vasoconstriction to maintain blood flow, but in severe hemorrhage, renal blood flow may be blocked –> kidney failure

Question 19

When does the baroreceptor mechanism stop working?

Answer 19

This mechanism will cease functioning below ~60mmHg

Question 20

Hemorrhage drops blood volume, which causes a __ward shift in the ascular function curve.

The baroreceptor responds by increasing sympathetic activity, causinga __ward shift in the cardiac function curve

Answer 20

downward shift in vascular fxn

upward shift in cardiac fxn

Question 21

Renal compensation / circulating vasoconstrictors as a reponse to hemorrhagic shock

Answer 21

• Epinephrine & norepinephrine from adrenal medulla
• Decreased renal perfusion –> renin secretion –> RAAS promotes water retention & vasocosntriction:
  
  • –> vasopressin/ADH from pituitary
  • –> aldosterone from adrenal gland

Question 22

Chemoreceptor reflex can operate below ~60mmHg.

Describe what it responds to and what it does

Answer 22

• Responds to hypoxia & acidic pH due to poor tissue perfusion
• Promotes increased CO & vasoconstriction:
  
  • Increased respiration
  • Incrased sympathetic activity

Question 23

Tissue fluid reabsorption/capillary fluid shift as a response to hemorragic shock

Answer 23

Arterial hypotension, vasoconstriction, and reduced venous pressure –> lower hydrostatic pressure in capillaries

–> increased fluid rebabsorption

–> increased blood volume

Question 24

Cerebral ischemia picks up around ~40mmHg after the chemoreceptor reflexbegins to decline

Answer 24

The brain is now experiencing ischemia –> increase sympathetics much higher than baroreceptor

Question 25

Decompensatory mechanisms occurs a result of ___

Answer 25

the compensatory mechanisms activated during hemorrhage fail –> decompensatory mechanisms exaggerate itse ffects in positive feedback.

DECREASES bp

Question 26

What are the decompensatory mechanisms?

• cardiogenic shock
• sympathetic escape
• CNS depression
• metabolic acidosis
• aberrations in clotting
• systemic inflammatory response

Answer 26

• Cardiogenic shock: myocardium becomes hypoxic & acidotic,
  
  • Reducing cardiac function
  • Promoting arrhythmias
• Sympathetic escape: without perfusion, there is no washout of vasodilators in the peripheral tissue –> vasodilation reduces TPR
  
  • –> bp drops & increases hydrostatic pressure
    
    • –> filtration and reducing blood volume
• CNS depression declines sympathetic activity
• Metabolic acidosis from lactic acid not being washed out –> depress CO and vascular smooth muscle contraction needed for vasoconstriction
• Clotting problems: blood viscosity increases without flow –> clotting factors create a hypercoagulability state
• Systemic inflammatory response: release endotoxins and cytokines
  
  • –> increased NO and ROS that promote vasodilation and decreased cardiac output