T2: Heart Innervation

Question 1

What is an animals resting heart rate dependent on?

Answer 1

• body size
• metabolic rate
• autonomic balance
• species characteristics

Question 2

Why does data on heart rates differ?

Answer 2

due to the differing environmental conditions

Question 3

Where does the innervation of the heart primarily arise from?

Answer 3

AUTONOMIC NERVOUS SYSTEM:
- sympathetic nerves
- parasympathetic nerves (vagus nerve)

Question 4

What does the autonomic nervous system innervate? Why?

Answer 4

• atria and ventricles
• to modulate their function and coordination

Question 5

What sympathetic nerves positively impact heart actions?

Answer 5

• chronotropic (rate of contraction)
• inotropic (force of contraction)
• bathmotropic (increase in excitability)
• dromotropic (rate of conductivity)

Question 6

What do chronotropic nerves impact?

Answer 6

rate of contractions

Question 7

What do inotropic nerves impact?

Answer 7

force of contraction

Question 8

What do bathmotropic nerves impact?

Answer 8

increase in excitability

Question 9

What do dromotropic nerves impact?

Answer 9

rate of conductivity

Question 10

What is the function of sympathetic stimulation?

Answer 10

• increases the SA node discharge
• increases AV conduction
• increases atrial and ventricular contractility

Question 11

What does sympathetic stimulation do to: contractility, frequency, conduction velocity and irritability?

Answer 11

increases!!

Question 12

What cellular mechanisms exist for sympathetic (SNS) nervous system actions?

Answer 12

• catecholamine norepinephrine

Question 13

Explain the functioning of norepinephrine.

Answer 13

• catecholamine norepinephrin released
• norepinephrin binds to adrenergic receptors (alpha/beta(main))
• adenylyl cyclase is activated
• enhancement of SA node ion channels rhythmicity

Question 14

What are the major types of adrenergetic receptors in cardiac tissue?

Answer 14

• alpha
  alpha 1
  alpha 2
• beta (predominates):
  beta 1
  beta 2

Question 15

What is the function of beta 1 adrenergic receptors?

Answer 15

• inotropic responses
• chronotropic responses

Question 16

What is the function of beta 2 adrenergic receptors?

Answer 16

mediate:
- glycogenolysis
- vasodilation

Question 17

What is the function of alpha 1 adrenergic receptors?

Answer 17

minor role (small density)

Question 18

What is the function of alpha 2 adrenergic receptors?

Answer 18

• inotropic responses

Question 19

What ions, specifically, depolarize and hyperpolarize the SA node?

Answer 19

depolarization: Ca2+
hyperpolarization: K+

Question 20

Explain the parasympathetic NS control of the heart.

Answer 20

right and left vagus nerves differentially innervate the SA node!

Question 21

What happens when the right vagus nerve is stimulated?

Answer 21

• decreases firing rate of the SA node
• decreases heart rate!
• negative inotropic effects excerted in the atria

Question 22

What happens when the left vagus nerve is stimulated?

Answer 22

• inhibits AV conduction
• produces AV block

negative chronotropic, negative inotropic and negative dromotropic action

Question 23

What does vagal stimulation cause?

Answer 23

• slows discharge rate of the SA node
• slows/blocks AV conduction
• decreases atrial contractability
• decreases ventricular contractability

Question 24

What do vagus nerves do at rest?

Answer 24

exert a continuous/tonic restraint on the heart

Question 25

What happens to the heart rate when the vagus nerves are cut or cooled?

Answer 25

heart rate becomes greatly **accelerated**

Question 26

What alters vagal activity?

Answer 26

physiological and pathological conditions

Question 27

What nervous system controls the heart?

Answer 27

autonomic nervous system

Question 28

Do the sympathetic and parasympathetic nervous systens oppose each other or work together?

Answer 28

OPPOSE EACH OTHER!

Question 29

What is the overall action of the sympathetic vs parasympathetic activation?

Answer 29

sympathetic- *increases* heart rate parasympathetic- *decreases* heart rate

Question 30

What happens when you apply pressure on the eyeball? (oculocardiac reflex)

Answer 30

slows the heart rate

Question 31

What happens when you inhale irritating vapours (eg. anasthetics)?

Answer 31

reflex inhibition of the heart - extrasystole - bradycardia

Question 32

What is the function of baroreceptors?

Answer 32

detect changes in blood pressure at: - the aortic arch - the carotid sinus

Question 33

What is the relation of pulse with arterial blood pressure?

Answer 33

**INVERSELY PROPORTIONAL**! - a rise in pressure causes a decrease of heart rate - a fall in pressure causes an increase in heart rate

Question 34

What happens to heart rate when pressure is increased in the carotid sinus/aortic arch?

Answer 34

heart rate is **reduced** with an increase in pressure!

Question 35

What is the reflex called which explains the inverse relationship of heart rate with arterial blood pressure?

Answer 35

**baro**reflex

Question 36

Explain the movement of ions in the sodium potassium pump.

Answer 36

- 3 Na+ out - 2 K+ in

Question 37

What type of feedback response does the baroreflex have?

Answer 37

**negative** feedback response

Question 38

Where are chemoreceptors located?

Answer 38

next to **baroreceptors** in: - **carotid** bodies - **aortic** bodies

Question 39

When do chemoreceptors send signals to the cardiovascular center?

Answer 39

- low O2 *hypoxia* - high CO2 *hypercapnia* - high H+ *acidosis*

Question 40

What is the "chemoreflex"?

Answer 40

heart rate altering by arterial blood **gases**

Question 41

What does the chemoreflex activation do to respiratory rate and depth?

Answer 41

- elevate respiratory rate - elevate respiratory depth

Question 42

State examples of hormones affecting the heart.

Answer 42

- epinephrine - norepinephrin - glucagon - mineralocorticoids - ACTH - vasopressin - angiotensin I - angiotensin II - thyroxine

Question 43

What type of effect (direct or indirect) does oxygen, carbon dioxide and pH have on the cardiorespiratory system? How?

Answer 43

- **both**! (direct and indirect) - via actions on the **carotid body** and central **chemoreceptors**

Question 44

How does hypoxia and hypercapnia affect cardiac contractibility?

Answer 44

depresses cardiac contractability hypoxia- too little oxygen hypercapnia- too much carbon dioxide