Mairead - ANS and the Heart

Question 1

What affects does sympathetic activity have on the heart?

Answer 1

Increases heart rate

Increases force of contraction of the ventricles

Question 2

What mediates increase of hr and force of contraction via sympathetic activity?
(3)

Answer 2

This is mediated by direct innervation of the heart and by the release of the hormones adrenaline and noradrenaline from the adrenal medulla

The sympathetic activation has a positive ionotrophic effect, acting on beta1 receptors of cardiac muscle

The hormones also stimulate ventricular muscle metabolism and perfusion of the myocardium

Question 3

What receptors are found in cardiac muscle?

Answer 3

Beta1 receptors

Question 4

What affect does adrenaline and noradrenaline have on the heart
(2)

Answer 4

They stimulate ventricular muscle metabolism and perfusion of the myocardium

They have a positive ionotrophic effect

Question 5

What is the net effect of sympathetic activity on the heart?
(4)

Answer 5

Increased force

Increased in SV

Decrease in ESV

Increase in heart rate

Question 6

What affect does the parasympathetic system have on the heart

Answer 6

Parasympathetic slows the heart rate and has a small decreasing effect on contractility

Question 7

What mediates the effect of the parasympathetic system on the heart

Answer 7

Mediated through the vagus nerve

Negative ionotrophic effect

Question 8

What does adrenaline and noradrenaline do to the heart?

Answer 8

Positive ionotrophic effect

Question 9

What does glucagon do to the heart?
(2)

Answer 9

It’s released by the pancreas to increase glucose levels in blood

It has a positive ionotrophic effect

Question 10

What affect do thyroid hormones have on the heart?

Answer 10

Thyroid hormones have a positive ionotrophic effect

Question 11

Comment on the adjustment of heart rate

Answer 11

Heart rate is continually adjusted as circulatory system demands changes

Question 12

What makes adjustments in heart rate?

Answer 12

ANS

Circulating hormones

Question 13

ANS and circulating hormones have a chronotrophic effect, what is meant by this?

Answer 13

They have the ability to alter the heart rate

Question 14

Where does the sympathetic and parasympathetic division innervate the heart?

Answer 14

The SA and AV nodes

Question 15

Describe the ANS activation in the heart at rest?

Answer 15

There is resting autonomic tone

Both divisions are active at rest

Question 16

At rest which division is slightly more dominant?

Answer 16

Parasympathetic

Question 17

How does the ANS adjust cardiovascular function

Answer 17

By adjusting both the sympathetic and parasympathetic divisions

Question 18

How exactly does ANS alter the HR?
(2)

Answer 18

Parasympathetic and sympathetic alter the HR by changing the permeability of the conducting system cells

This is done by altering SA node firing and altering the conduction time

Question 19

What affect does altering SA node firing have?

Answer 19

It changes the permeability of the conducting system cells

Question 20

What affect does increasing parasympathetic firing of SA node have on HR

Answer 20

Results in slower HR

Question 21

How does increasing parasympathetic firing result in slowing heart rate?

Answer 21

By increasing the K+ permeability and hyperpolarizing the membrane

This Ach/Muscarinic action is a negative chronotrophic effect

Question 22

What does increasing the sympathetic firing of the SA node do?
(4)

Answer 22

Releases noradrenaline at the B1 receptors

This increases the Na+ and Ca++ entry

This increases the rate of depolarisation and shortens repolarisation

This is a positive chronotrophic effect

Question 23

What does a release of noradrenaline at B1 receptors do?

Answer 23

Increases the Na+ and Ca++ entry

Question 24

What does increased Na+ and Ca++ entry do

Answer 24

This increases the rate of depolarisation and shortens repolarisation

Question 25

What is another name for the Bainbridge reflex?

Answer 25

Atrial reflex

Question 26

What activates the Bainbridge reflex

Answer 26

As the venous return increases, the walls of the right atrium are stretched

Question 27

What does the Bainbridge reflex do? (3)

Answer 27

It activates the ANS Results in increased sympathetic activation i.e. increases SA node firing The increase in HR matches the increase in venous return

Question 28

What hormones affect the heart rate and what do they do? (2)

Answer 28

Adrenaline, noradrenaline and thyroid hormones They increase the heart rate and contractility of the heart

Question 29

When is adrenaline or noradrenaline released (2)

Answer 29

Sympathetic activation in a flight or flight response Stimulates release of adrenaline and noradrenaline from the adrenal gland

Question 30

How does adrenaline and noradrenaline increase the heart rate?

Answer 30

They increase the rate of depolarisation of the SA node and decrease the duration of repolarisation

Question 31

What is the equation for cardiac reserve?

Answer 31

Max CO - resting CO

Question 32

What may cause an increase in demand on the heart?

Answer 32

May increase due to muscle damage, valve damage or hypertension

Question 33

What affects does increased demand on the heart have on the heart?

Answer 33

Cardiac output may be inadequate Pulmonary pressures increase

Question 34

What happens when CO may be inadequare

Answer 34

This may lead to poor perfusion, and therefore fatigue and poor exercise tolerance

Question 35

What happens when pulmonary pressures increase?

Answer 35

This may lead to oedema in the lung tissue and poor O2 exchange, which results in breathlessness

Question 36

What is it called if K+ is high?

Answer 36

Hyperkalemia

Question 37

What is it called if K+ is low?

Answer 37

Hypokalemia

Question 38

What happens if K+ is really high?

Answer 38

it's life threatening

Question 39

Write a note on high K+

Answer 39

Depolarisation normal K+ movement inhibited as K+ channel opens Therefore, repolarisation is inhibited Muscle becomes weak

Question 40

Write a note on low K+

Answer 40

Hyperpolarisation of muscle cells Muscle more difficult to excite Hyperpolarisation of nodal cells: hr down, blood pressure down

Question 41

What is high calcium called?

Answer 41

Hypercalcemia

Question 42

What is high Ca++? (4)

Answer 42

EC Ca++ increased, SR Ca++ increased Cells extremely excitable More powerful and prolonged contractions May be fatal

Question 43

Write about low Ca++

Answer 43

Contractions weak May stop

Question 44

Write about low temperature

Answer 44

Slows SA depolarisation Lowers HR Reduced strength of contraction

Question 45

Write about high temperature

Answer 45

Increased hr and force

Question 46

What effects does caffeine have on the heart?

Answer 46

Caffeine, increased rate of depolarisation of the SA node

Question 47

What effects does nicotine have on the heart?

Answer 47

Sympathetic neurons