Effect of exercise on the heart

Question 1

Summarise the exercise reflex

Answer 1

Reflexive CVS changes in response to contracting skeletal muscle that increase BP

Question 2

The 3 changes induced by the exercise reflex

Answer 2

Increased respiration (increased motor activity to diaphragm & intercostals)

Increased HR and contractility (increased CO)

Increased sympathetic activity (NA) to GIT, kidneys, skin, all skeletal muscle causing vasoconstriction

Question 3

What triggers the exercise reflex

Answer 3

metabolites (K+, Pi, adenosine) stimulating metaboreceptors in exercising muscle (+ joint receptors in dynamic exercise)

Question 4

Which part of the brain is the “exercise integrating area” stimulated on the exercise reflex

Answer 4

subthalamic locomotor region (SLR) in the hypothalamus

Question 5

Exercise hyperaemia =

Answer 5

local vasodilation in vessels triggered by metabolites

Question 6

functional sympatholysis =

Answer 6

sympathetic vasoconstriction in exercising muscle is overcome by local vasodilation (exercise hyperaemia)

Question 7

Overall, what happens to TPR and ABP in static exercise

Answer 7

TPR increases

large increase in ABP

Question 8

Overall, what happens to TPR and ABP in dynamic exercise

Answer 8

TPR changes little

small increase ABP

Question 9

how is the vasoconstriction of skin, caused by the exercise reflex, overcome when body temperature increases?

Answer 9

by the thermoregulatory reflex - decreases sympathetic activity causing vasodilation

Question 10

What metabolites are released from exercising muscles

Answer 10

K+

Pi and adenosine (from ATP hydrolysis)

Question 11

The mechanical compression of vessels by contracting muscles causes a rhythmic increase in blood flow during dynamic exercise. What does this do to TPR?

Answer 11

overall decreases it

Question 12

The mechanical compression of vessels by contracting muscles means blood flow may not increase during static exercise, hyperaemia occurs after contraction. What does this do to TPR?

Answer 12

TPR increases during contraction (so ABP does)

Question 13

Which type of exercise is recommended for people with coronary artery disease and why

Answer 13

Dynamic exercise

Avoid static because it is a greater cardiovascular risk. High ABP during contraction–> aneurysm or stroke. Possibly low ABP after contraction –> postural hypotension

• greater cardiac work so greater coronary vasodilatation required
• O2 delivery to contracting muscle is limited, metabolites accumulate which enhances the exercise reflex causing pain (coronaries limited in how much O2 they can give the heart and an enhanced reflex means the SNS is asking the heart to work harder –>pain)

Question 14

Characteristics of the alerting/defence response

Answer 14

More SNS/less PSNS activity to heart > higher CO
Increased respiration
Vasoconstriction to GIT, skin, kidneys
Vasodilatation of vessels in skeletal muscle via less SNS activity (less NA binding a1) and more circulating adrenline (binds B2)

Overall: higher ABP, higher HR, increased blood flow to muscle

Question 15

Habituation

Answer 15

alerting/defence response gets smaller and smaller if the stimulus is repeated several times

Question 16

Sensitisation

Answer 16

alerting/defence response gets bigger and bigger if the stimulus is repeated several times

Question 17

What can trigger vasovagal syncope

Answer 17

after the alerting/defence response (occurs in extreme emotional stress)
after strenuous exercise (if you remain standing) or haemorrhage

(these all cause increased contractility of the ventricle on a low EDV - ventricular torsion)

Question 18

What can trigger the alerting/defence response

Answer 18

emotional/environmental stress

new situations, sound, pain, emotion etc

Question 19

The effects of vasovagal syncope which lead to fainting

Answer 19

reflexive increase in vagal activity to the heart to decrease HR, and decrease in sympathetic activity to vessels all over -> vasodilatation

ABP drops and faint when brain BP falls

Question 20

CO at rest does not change with training. What is CO at rest approx?

Answer 20

5L/min-

Question 21

Training releases growth factors which cause eccentric hypertrophy of the heart. What is the effect of this?

Answer 21

An increased EDV and so an increased SV and CVP

Question 22

Training increases SV at rest but does not increase CO at rest - how is this?
(CO = SV x HR)

Answer 22

It decreases HR at rest (bradycardia)

Question 23

How does training cause bradycardia (lower HR) at rest

Answer 23

increased tonic vagal activity
increased local Ach release
decreased pacemaker activity

causes decreased HR so decreased ABP

Question 24

VO2 max is

Answer 24

the rate of maximum O2 uptake from the air and/or the rate of maximum O2 use by the mitochondria

Question 25

What vascular changes occur in the heart as a result of training

Answer 25

increase in capillary number​ > increase in capillary:fibre ratio​ >decreased diffusion distance (9µm)

increased number of arterioles​

increased coronary artery diameter​ > decreased resistance > increased blood flow

Question 26

What vascular changes occur in muscle as a result of training

Answer 26

increased blood flow > increased shear stress > growth factor release which causes

arterialization of capillaries
angiogenesis > increased no. & density of capillaries & arterioles
increased muscle mitochondria and myoglobin

also increased NO synthesis, less ROS production

Question 27

What endogenous hormone do athletes use in doping?

Answer 27

EPO

stimulates erythropoesis and alters haematocrit