Circulatory System: Cardiac Centers and Nervous Regulation

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Questions and Answers

Where are the depressor receptors located that are part of the intrinsic reflexes?

Aortic arch & carotid sinus (correct)

Ventricles of the heart

Coronary sinus

Pulmonary arteries

What is the role of intrinsic reflexes from the left side of the heart affecting the medullary cardiac center?

To increase the heart rate

To decrease the blood pressure

To send depressor impulses to inhibit the cardiac centers (correct)

To stimulate the medullary cardiac centers

What happens to the activities of the depressor receptors if arterial blood pressure is gradually lowered?

Their activities increase

Their activities remain unchanged

They stop functioning

Their activities decrease (correct)

What is the effect of stimulation from the depressor receptors on the medullary centers?

Inhibition of CAC & stimulation of CIC Signup and view all the answers

Which nerves supply the aortic arch and carotid sinus with afferents related to the reflex mechanism?

Aortic nerve and sinus nerve Signup and view all the answers

What is the main stimulus for the arterial baroreceptors located in the aortic arch and carotid sinus?

$60$ mmHg blood pressure Signup and view all the answers

What is the role of the Cardio inhibitory center (CIC) in the heart?

Inhibits the heart's activity Signup and view all the answers

Which nerve exerts a continuous inhibitory effect on the heart during rest?

Vagus nerve Signup and view all the answers

What is a characteristic of Vagal escape in the cardiac system?

Results from prolonged strong vagal stimulation Signup and view all the answers

What is the normal heart rate range under basal conditions?

75-100 beats/minute Signup and view all the answers

Where are the Cardio acceleratory center (CAC) and Cardio inhibitory center (CIC) located?

Medulla oblongata Signup and view all the answers

What is Vagal Tone responsible for?

Decreasing SAN rhythm Signup and view all the answers

What is the main stimulus for the carotid and aortic bodies' arterial chemoreceptors?

Hypoxia Signup and view all the answers

What effect does the Bainbridge reflex have on heart rate?

Accelerates the heart rate Signup and view all the answers

What is the mechanism behind the inhibition of the cardiac inhibitory center (CIC) according to Mary’s Law?

Stimulation of arterial baroreceptors Signup and view all the answers

Which nerve transmits afferent depressor impulses to inhibit the cardiac acceleratory center (CAC)?

Aortic nerve Signup and view all the answers

What happens to heart rate when pressure rises in the right auricle and big veins due to the Bainbridge reflex?

It accelerates Signup and view all the answers

What is the main effect of hyperpnoea according to the text?

Increased respiratory rate & depth Signup and view all the answers

What is the Bainbridge effect?

An increase in heart rate caused by local stretch of the SA node Signup and view all the answers

What is the Extrinsic reflex related to an increase in heart rate?

Voluntary muscle contraction Signup and view all the answers

What characterizes Respiratory sinus arrhythmia?

Heart rate increases during inspiration and decreases during expiration Signup and view all the answers

What contributes to the increase in heart rate during inspiration related to Respiratory sinus arrhythmia?

Distention of lungs and pressor afferent impulses along pulmonary vagi Signup and view all the answers

How does asphyxia affect heart rate?

Reflex bradycardia due to rise in arterial blood pressure Signup and view all the answers

How does the active inspiratory center affect heart rate?

It irradiates impulses to stimulate CAC Signup and view all the answers

Study Notes

Cardiac Regulation

The heart rate is regulated by the medullary cardiac center, which consists of the cardioinhibitory center (CIC) and the cardioacceleratory center (CAC).

Intrinsic Reflexes

Intrinsic reflexes come from the cardiovascular system and affect the medullary cardiac center.
Examples include:
- Left side of the heart:
  - Carotid sinus and aortic arch (depressor receptors)
  - Stimulus: Arterial blood pressure above 60 mmHg
  - Effect: Sends depressor impulses to the medullary centers, leading to inhibition of CAC and stimulation of CIC, decreasing heart rate
- Right side of the heart:
  - Bainbridge reflex: Reflex acceleration of the heart due to a rise in pressure in the right atrium and big veins as a result of sudden increase in venous return
  - Mechanism: Stimulation of mechanoreceptors in the right atrium and big veins, sending pressor impulses to the medullary centers, inhibiting CIC and stimulating CAC

Extrinsic Reflexes

Extrinsic reflexes come from outside the cardiovascular system and affect the medullary cardiac center.
Example: Skeletal muscles (Alam Smirk reflex)

Respiratory Sinus Arrhythmia

Definition: Heart rate increases during inspiration and decreases during expiration
Mechanisms:
- Distention of lungs during inspiration, leading to pressor afferent impulses and inhibition of CIC and stimulation of CAC
- Bainbridge reflex: Increased venous return during inspiration, leading to stimulation of CAC
- Active inspiratory center irradiates impulses to stimulate CAC

Metabolites and Asphyxia

Asphyxia: A state of hypoxia, hypercapnia, and acidosis
Effects on heart rate:
- Initial slowing: Due to stimulation of CIC and inhibition of CAC
- Regulation of heart rate: Involves afferent impulses affecting the medullary cardiac center, including intrinsic and extrinsic reflexes and changes in the chemical composition of the blood

Vagal Tone and Vagal Escape

Vagal tone: Continuous inhibitory effect of the vagi nerves on the heart during rest, reducing the inherent rhythm of the SAN from 120 to 70 impulses/minute
Vagal escape: Prolonged strong vagal stimulation, leading to marked inhibition of SAN and subsequent escape of ventricles from inhibitory effect of vagi, resulting in an idioventricular rhythm

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Description

Explore the functions of cardiac nerves, regulation of heart rate, and cardiac innervation in the circulatory system. Learn about the Cardio Inhibitory Center (CIC), Cardio Acceleratory Center (CAC), and Vagal Tone.