Coconote
AI notes
AI voice & video notes
Export note
Try for free
Overview of Heart Rate Control Mechanisms
Oct 10, 2024
🤓
Take quiz
Learn A-Level Biology: Control of Heart Rate
Introduction
Control of heart rate links to the stages in the cardiac cycle.
Cardiac Muscle
: Myogenic - contracts and relaxes independently but the rate is controlled by the nervous system.
Key Structures in the Heart
Sinoatrial Node (SAN)
:
Located in the right atrium.
Known as the pacemaker.
Releases waves of depolarization causing muscle contractions.
Atrioventricular Node (AVN)
:
Located between the atria and ventricles.
Releases wave of depolarization with a slight delay.
Bundle of His
:
Conductive tissues running down the heart's septum.
Purkinje Fibres
:
Conductive tissues that branch through the ventricle walls.
Control of the Cardiac Cycle
SAN Activity
:
Releases wave of depolarization causing atrial systole.
Atria contract.
AVN Activity
:
Releases second wave of depolarization.
Depolarization travels through Bundle of His due to non-conductive tissue separating atria and ventricles.
Travels through Purkinje fibres leading to contraction starting from the apex of the ventricle.
Importance of Non-Conductive Tissue
Causes delay for atria to fully contract and ventricles to fill before contraction.
Ensures efficient blood ejection from the heart.
Nervous System Control
Part of the Autonomic Nervous System (ANS), controlled subconsciously by the medulla oblongata.
Sympathetic Nervous System
: Increases heart rate.
Parasympathetic Nervous System
: Decreases heart rate.
Homeostasis and Heart Rate
Key Stimuli
Blood pH
: Affects the heart's response during high respiration (exercise).
Low pH during high CO2 or lactic acid.
Detected by chemoreceptors.
Blood Pressure
: Detected by pressure receptors (baroreceptors).
High pressure can damage artery walls.
Low pressure affects oxygen delivery and waste removal.
Response to Stimuli
Increase in Pressure
:
Detected by baroreceptors.
More impulses to medulla oblongata.
Activates parasympathetic nerves reducing heart rate.
Decrease in Pressure
:
Detected by baroreceptors.
More impulses activate sympathetic nerves increasing heart rate.
Decrease in pH
:
Detected by chemoreceptors.
More impulses to sympathetic nerves increase heart rate.
Key Points for Exam Questions
Importance of specifying "more" electrical impulses.
Distinction between sympathetic and parasympathetic responses.
Conclusion
Understanding the mechanics and control of the heart rate is crucial for explaining cardiovascular responses to various physiological conditions.
📄
Full transcript