CVS 5 Heart Rate Regulation

Summary

This video explores the anatomy and physiology of the cardiovascular system, focusing on how the heart's natural rhythm is regulated by neural and chemical impulses. It discusses the sinoatrial node as the pacemaker, the electrical activity captured in an ECG, and the role of the autonomic nervous system in adjusting heart rate and blood flow. The video also covers heart rate abnormalities like arrhythmias and their detection methods.

Takeaways

• 💓 The human heart has an innate rhythm, beating about 100 times per minute without external influence, but can be adjusted by nerves and chemical regulators in the blood.
• 🏃‍♂️ During exercise in a hot and humid environment, up to 20% of the heart's total output is directed to the skin to help cool the body down.
• 🔄 The sinoatrial (SA) node acts as the heart's pacemaker, naturally depolarizing and repolarizing to set the pace for heartbeats.
• 🛤️ The pathway of the cardiac impulse travels from the SA node through the atria, the atrioventricular (AV) node, the bundle of His, and the Purkinje fibers to the ventricles.
• 📊 An ECG records the heart's electrical activity, showing patterns like P-waves, QRS complex, and T-waves, which correspond to atrial and ventricular depolarization and repolarization.
• 🧠 The brain, particularly the medulla, is the cardiovascular control center, receiving information and sending signals to regulate heart rate and blood vessel diameter.
• 🚀 Sympathetic stimulation releases hormones like epinephrine and norepphrine, increasing heart rate and force of contraction, while parasympathetic stimulation via acetylcholine slows the heart rate.
• 🏋️‍♀️ Physical activity and emotional states can influence heart rate, with the 'anticipatory heart rate' increasing before intense physical effort due to sympathetic activation.
• 🔍 An ECG can detect heart function abnormalities such as cardiac rhythm, electrical conduction, myocardial oxygen supply, and tissue damage.
• 🩺 Heart rate irregularities, known as arrhythmias, can be monitored and detected through an ECG, with treatments ranging from lifestyle changes to medical interventions like beta blockers.
• 🆘 Ventricular fibrillation is a dangerous arrhythmia that can be treated with CPR or defibrillation to restore a normal heart rhythm.

Q & A

What percentage of blood does the skin receive when you are just relaxing in a comfortable environment?

When you are just relaxing in a comfortable environment, your skin receives about 250 ml of blood, which is roughly 5% of the 5 liters your heart pumps out each minute.

How does the body's blood distribution change when exercising in a hot and humid place?

When exercising in a hot and humid place, about 20% of the heart's total output goes to the skin to help cool the body down.

What is the role of the sinoatrial node in the heart's function?

The sinoatrial node is a specialized mass of muscle tissue in the right atrium's posterior wall that naturally depolarizes and repolarizes, providing an innate stimulus to the heart. It sets the pace for your heartbeat and is often referred to as the pacemaker.

What is the normal pathway for myocardial impulse transmission in the heart?

The normal pathway for myocardial impulse transmission starts at the sinoatrial node, goes through the atria, then heads through the atrioventricular node, through the atrioventricular bundle into the Purkinje fibers, and finally causes the ventricles to contract.

How does the heart's electrical activity generate an electrical field throughout the body?

The heart's electrical activity generates an electrical field throughout the body because the salty fluids in the body are great conductors. Electrodes placed on the skin can detect the voltage changes from the sequence of electrical events that happen before and during each heartbeat.

What are the key patterns seen on an ECG?

The key patterns seen on an ECG are the P wave, the QRS complex, and the T wave, along with the PR and QT intervals and the ST segment.

How does the atrial pressure affect the flow of blood between the atria and ventricles?

When the atrial pressure is higher than the ventricular pressure, blood flows from the atria into the ventricles. However, as soon as the ventricle starts to contract and the ventricular pressure becomes higher than the atrial pressure, the mitral valve closes to prevent backflow.

What is the effect of sympathetic stimulation on the heart?

Sympathetic stimulation of the heart causes the release of hormones like epinephrine and norepinephrine, which make the heart muscle contract more forcefully and speed up the heart rate.

How does the parasympathetic nervous system affect the heart rate?

The parasympathetic nervous system releases a hormone called acetylcholine, which slows down the heart rate by reducing the sinus node discharge rate. This slowing down is called bradycardia and is controlled by the vagus nerve.

What is the role of the brain in regulating heart rate and how does it interact with the cardiovascular system?

The brain, specifically the cardiovascular control center located in the medulla, receives information from various reflex arcs within the body and sends signals to the heart and blood vessels. It ensures the heart and blood vessels work together to optimize blood flow and maintain blood pressure during activity.

What are the potential consequences of ventricular fibrillation and how can it be treated?

Ventricular fibrillation is a dangerous type of arrhythmia where multiple points of the ventricles are continuously stimulated, disrupting the normal coordinated contraction. This can lead to repetitive PVCs, preventing the ventricles from pumping blood effectively, reducing cardiac output and blood pressure, and causing rapid loss of consciousness. Cardiopulmonary resuscitation (CPR) can simulate the heart's pumping action and may reverse fibrillation. If CPR isn't effective, an automated or semi-automated defibrillator can deliver a strong electrical shock across the heart to polarize it and allow the SA node to restart a normal rhythm.

Outlines

00:00

🫀 Introduction to Cardiovascular System Dynamics

This paragraph introduces the video series on the cardiovascular system, highlighting how blood distribution changes during relaxation and exercise. It explains the importance of the circulatory system's regulation in maintaining blood pressure and meeting the body's metabolic needs. The paragraph also touches on the heart's natural rhythm and how external factors can adjust heart rate.

05:00

💓 Heart's Electrical Activity and ECG

This section details the heart's electrical activity, focusing on the sinoatrial (SA) node, which acts as the pacemaker. It explains how electrical impulses travel through the heart, leading to contraction and relaxation. The paragraph describes the electrocardiogram (ECG) and the key patterns (P-wave, QRS complex, and T-wave) that indicate different phases of the heart's electrical cycle.

10:02

⚡️ Sympathetic and Parasympathetic Regulation of Heart Rate

This paragraph explains the role of the autonomic nervous system in heart rate regulation. It discusses how the sympathetic nervous system accelerates the heart rate through epinephrine and norepinephrine, while the parasympathetic system slows it down via acetylcholine. It also covers the involvement of the cardiovascular control center in the brain and how it integrates sensory input to regulate cardiovascular responses during physical activity.

15:04

📉 Heart Rhythm Abnormalities and ECG Monitoring

This section covers heart rhythm irregularities, such as premature atrial and ventricular contractions, and their potential causes. It explains the importance of ECG monitoring in detecting these abnormalities and the implications for heart health. The paragraph also discusses more serious conditions like atrial fibrillation and ventricular fibrillation, their effects on the heart's pumping ability, and the interventions like CPR and defibrillation to restore normal rhythm.

Keywords

💡Cardiovascular System

The cardiovascular system is the body's 'transport' system, responsible for circulating blood throughout the body. It includes the heart, blood vessels, and blood. In the video, it is emphasized that the cardiovascular system plays a critical role in adjusting blood flow to meet the body's metabolic and physiological needs, especially during exercise and in hot, humid conditions.

💡Sinoatrial Node

The sinoatrial node, often referred to as the heart's 'pacemaker,' is a group of specialized cells in the right atrium that generates electrical impulses to regulate the heartbeat. The video explains that this node naturally depolarizes and repolarizes, setting the rhythm for the heart's contractions without external influences.

💡Heart Rate

Heart rate refers to the number of times the heart beats per minute. The video discusses how the heart rate can vary significantly, from a resting rate influenced by factors like athletic training to rates that increase during physical activity. It also mentions how external factors and the body's own regulatory mechanisms can adjust heart rate.

💡Depolarization

Depolarization is the process where the electrical charge across a cell membrane becomes less polarized, often leading to an action potential in excitable cells like those in the heart. The script describes how the sinoatrial node depolarizes to initiate the heartbeat and how this process is part of the normal electrical cycle of the heart.

💡Atrioventricular Node

The atrioventricular node (AV node) is a cluster of cells located in the heart that acts as a 'gatekeeper' for electrical impulses, delaying them to allow the atria to contract before the ventricles. The video script explains the role of the AV node in the pathway of the cardiac impulse.

💡Bundle of His

The bundle of His is a specialized group of fibers that rapidly transmit electrical impulses from the AV node to the ventricles, ensuring synchronized contraction. The script uses the bundle of His to illustrate the efficient conduction system of the heart.

💡ECG (Electrocardiogram)

An ECG is a graphical representation of the electrical activity of the heart, which can be used to monitor and diagnose various heart conditions. The video script describes the key patterns seen on an ECG, such as P-waves, QRS complex, and T-waves, and how they relate to the heart's electrical cycle.

💡Ventricular Contraction

Ventricular contraction is the process where the ventricles of the heart squeeze to pump blood out into the circulatory system. The video script describes how this contraction is coordinated with the opening and closing of heart valves and the changes in pressure within the heart chambers.

💡Sympathetic Nervous System

The sympathetic nervous system is part of the autonomic nervous system that prepares the body for 'fight or flight' situations by increasing heart rate and blood pressure. The video explains how the sympathetic system can override the heart's natural rhythm during physical activity or stress.

💡Parasympathetic Nervous System

The parasympathetic nervous system is another branch of the autonomic nervous system that promotes 'rest and digest' by decreasing heart rate and promoting relaxation. The script contrasts this system with the sympathetic system, explaining how it slows the heart rate through the release of acetylcholine.

💡Arrhythmia

Arrhythmia refers to any abnormality in the heart's rhythm, which can manifest as extra or skipped heartbeats. The video script discusses various types of arrhythmias, such as premature atrial contractions and ventricular fibrillation, and the potential consequences and treatments for these conditions.

Highlights

The skin receives about 250 ml of blood, or 5% of the heart's total output, when at rest in a comfortable environment.

During exercise in hot conditions, up to 20% of the heart's total output is redirected to the skin for cooling.

The cardiovascular system uses a closed circulatory approach to meet metabolic needs and maintain blood pressure.

The sinoatrial node, located in the right atrium, acts as the heart's natural pacemaker, setting the rhythm of heartbeats.

The normal heart rate can vary significantly, from 35-40 beats per minute in endurance athletes to 220 beats per minute during intense exercise.

The pathway of the cardiac impulse is detailed, starting from the sinoatrial node and ending with the contraction of the ventricles.

ECG records the heart's electrical activity, showing patterns like P-waves, QRS complex, and T-waves, which are crucial for diagnosing heart conditions.

The heart's electrical cycle and its corresponding phases can be monitored in real-time using an ECG for various physical activities.

Heart sounds and their corresponding ECG signals help in understanding the phases of the heart's contraction and relaxation.

Pressure changes within the heart chambers are crucial for the opening and closing of valves, ensuring efficient blood flow.

Neural and chemical impulses can override the heart's natural rhythm, adjusting heart rate and blood vessel diameter for optimal blood flow.

The medulla is the cardiovascular regulatory center, sending signals through the sympathetic and parasympathetic nervous systems.

Sympathetic activation releases epinephrine and norepinephrine, increasing heart contractility and rate, while parasympathetic activation slows the heart rate.

The brain's Central Command influences heart rate调节, especially during physical activity and emotional states.

Reflex neural input from muscle receptors and higher brain centers helps regulate blood flow and pressure during dynamic activity.

Heart rate irregularities or arrhythmias can be detected through ECG monitoring, indicating potential heart disease.

Ventricular fibrillation is a dangerous arrhythmia that disrupts normal heart contraction and can lead to rapid loss of consciousness.

CPR and defibrillation are critical interventions for treating severe arrhythmias, aiming to restore a normal heart rhythm.

Transcripts

welcome to the next video in the series

comprising the anatomy and physiology

for the cardiovascular

system when you're just relaxing in a

comfortable environment your skin gets

about 250 Ms of blood which is roughly

5% of the 5 L your heart pumps out each

minute but when you're exercising in a

hot humid place around 20% of your

heart's total output goes to your skin

to help cool you down your body quickly

redirects blood to meetus metabolic and

physiological needs while keeping your

blood pressure in check this precise

adjustment relies on a closed

circulatory system both Central and

local control of how much blood the

heart pumps and where your body sends

that blood the first piece of this

regulation puzzle is what dictates how

fast and hard our heart is pumping the

blood this video will provide you with

the information you require to be able

to address the following learning

objectives

your heart muscle has a natural Rhythm

even without any outside influences an

adult heart would beat steadily at about

100 times per minute however within your

body cardiac nerves that directly

connect to your heart and specific

chemical Regulators in your blood can

quickly adjust your heart rate external

factors can make your heart speed up in

anticipation even before you start

physical

activity this regulation can slow

endurance athletes h resting heart rate

to as low as 35 to 40 beats per minute

and during intense physical effort it

can increase up to 100 sorry 220 beats

per minute inside your right atrium's

posterior wall is a specialized mass of

muscle tissue called the sinoatrial

node the sinoatrial node naturally

depolarizes and repolarizes providing an

innate stimulus to the heart which is

why it's often referred to as the

pacemaker this node sets the pace for

your

heartbeat the normal pathway for

myocardial impulse transmission is

Illustrated in this figure the pathway

of the cardiac impulse is starting at

the sinoatrial node going through the

Atria then heading through the atrio

ventricular node through the atrio

ventricular bundled into the pingi

fibers and then finally having the

ventricles to contract

your heart's electrical activity

generates an electrical field throughout

your body the salty fluids in your body

are great conductors so electrodes

placed on your skin can detect the

voltage changes from the sequence of

electrical events that happened before

and during each

heartbeat in the figure on the right you

can see the timing sequence of how the

electrical impulse travels from the

sinoatrial node Through The

myocardium it all starts at the SA node

which send sends out rhythms that spread

across the Atria and then is focused on

the Atria ventricular node a small knot

of tissue the AV node acts as a

gatekeeper delaying the impulse by about

0.1 of a second this gives the Atria

enough time to contract and push blood

into the

ventricles from The Av node the impulse

travels down the AV bundle also known as

the bundle of hiss this bundle quickly

sends the impulse through the ventricles

via specialized conducting fibers called

the peni system the peni fibers Branch

out into the right and left ventricles

and within 06 of a second every cell in

The ventricle gets the signal causing

both ventricles to contract at the same

time the heart's electrical activity

creates an electric field that can

easily be detected on your skin during

each heartbeat the figure shows how

electrical impulse travels through the

heart muscle causing it to contract and

relax in a rhythmic

pattern the heart's normal electrical

cycle is recorded as an ECG and the key

patterns you can see on an ECG called

the P QRS and t- waves along with the pr

and QT intervals and the ST segment now

let's explore these in a little bit more

detail the panel figure illustrates the

hearts normal electrical cycle as

recorded by the

ECG the key patterns you see on an

ECG are called the p-wave the QRS

complex and the t- waves along with the

pr and QT intervals and the ST

segment the P wve represents atrial

depolarization which lasts about .15

seconds and leads to the Atria

Contracting the QRS complex follows the

p-wave and indicates ventricular

depolarization which makes the

ventricles

contract atrial repolarization happens

at this time too but it's usually hidden

by the much larger QRS

complex the t-wave represents

ventricular

repolarization occurring during the

ventricular diast phase the heart's

relatively long depolarization period

somewhere between between. 2 and3

seconds prevents a new impulse from

starting immediately giving the

ventricles enough time to fill up with

blood between

beads an ECG is a handy tool for

monitoring heart rate during various

physical activities with radio telemetry

the ECG can trit transmit data while

you're going about your normal daily

activities an ECG can reveal four main

types of heart function

abnormalities cardiac rhythm

electrical conduction myocardial oxygen

supply and also myocardial tissue

damage okay I acknowledge there is a lot

going on in this image but let's work

our way through it slowly the image

represents events occurring the left

side of the Heart during one cardiac

cycle and it is bringing together what

is occurring as the heart muscle

contracts creating an increase in

pressure of the chamber as it decreases

in size subsequently causing the valves

to open and blood to be ejected from the

chamber all right let's start at the

bottom and work our way

up what we can see is the phases of the

heart through syy by the contraction of

The ventricle into diast and then

another beginning of the next cycle in

syy we've got our heart sounds

occurring and these are corresponding to

our ECG signal that we've just learned

about

what we don't know much about is the

volume that's actually residing within

the ventricle

itself so as we can see at the beginning

of a ventricular contraction we see a

dramatic decrease in the volume which

makes sense we're expelling blood from

the heart itself we then have closing of

the aortic valve and then during this

time we start to see rapid refilling of

The ventricle as blood is flowing

through the Atria and then we'll finally

have our Atria Contracting which corres

responds to our p wve and a slight

topping up of that ventricular volume

and this is what we refer to as our end

diastolic volume we then have

contraction occurring again with the

subsequent decrease in volume of the

blood within the

ventricle now all of this corresponds to

changes in pressure within the different

chambers of the heart themselves so in

dark blue here we have our actual

ventricular pressure so the

pressure within the actual ventricle

itself and in this light gray we have

our atrial pressure so as you can see

when the atrial pressure is higher than

the ventricle pressure we have blood

flowing from the Atria Into The

ventricle however as soon as that

ventricle starts to contract we get to a

point where the ventricle pressure is

higher than the Atria pressure and we

don't want blood flowing back from our

ventricle into our Atrium so mital valve

closes at this point we then start to

steadily build the pressure up in The

ventricle till we get to a point when

that ventricular pressure is actually

higher than our aortic pressure and that

means our aortic valve will open and all

of a sudden we now start to see blood

being ejected out of The ventricle

itself as you can see by the drop in the

red volume line as that ventricle

continues to contract we see rises in

the pressure but the volume is falling

so that also means that we'll get to a

point where we start to see that

pressure drop off and it will reach

finally a point where the aortic

pressure is higher than the ventricular

pressure and our aortic valve

closes that ventricular pressure keeps

falling until we get to the point where

it's now lower than the atrial pressure

meaning our mitro valve open and blood

will start to flow back into the

ventricle

itself your heart's natural Rhythm can

be overridden by both neural and

chemical or hormonal

impulses these impulses have the

capability of adjusting your heart rate

and altering the diameter of your blood

vessels this enables more blood to get

to where it needs to go while also

maintaining the all important blood

pressure

this figure provides a complete overview

of how the brain and specifically the

cardiovascular control center located in

the ventrolateral medala receives

information back from various reflex

arcs within the body and sends signals

to the heart and blood

vessels in the next few slides we will

look more closely at each component of

this control

system your heart's n Rhythm can be

overridden by neural impulses these

signals come from the medala which is

the cardiovascular regulatory Center and

travel through the sympathetic and

parasympathetic nervous

systems when the sympathetic cardio

accelerator nerves are stimulated they

release hormones called epinephrine and

norepinephrine also called adrenaline

and

noradrenaline these hormones make the

heart muscle contract more forcefully

and speed up the heart rate response

known as

tardia epinephrine also released during

General sympathetic activation by the

adrenal glands located above the kidneys

has a similar but slower effect on the

heart's overall

function on the other hand the

parasympathetic nervous system releases

a hormone called acetol choline which

slows down the heart rate by reducing

the sinus discharge rate this slowing

down is called bra cardia and is

controlled by the vagus nerve whose

cells bodies are in the medala cardio

inhibitory region vagal stimulation

slows the heart but doesn't affect the

strength of the heart

contractions so in summary sympathetic

stimulation of the heart causes release

from the nerves of epinephrine and

norepinephrine and this causes faster

and stronger heart

beats the sympathetic nerve endings that

innovate different smooth muscle

surrounding arteries and arterial

have different responses depending upon

their specific

location sympathetic stimulation results

in vasodilation of the coronary arteries

increasing blood flow to the heart

muscle while it generally causes Vaso

constriction

elsewhere the branches of the autonomic

nervous system the sympathetic and

parasympathetic have numerous roles

throughout the body the sympathetic

nervous system has been turned the

Fright flight and fight branch while the

S par sorry while the parasympathetic is

the rest and digest we will focus

primarily on the actions of this

autonomic nervous system with its role

on the cardiovascular

system in comparison to the sympathetic

nervous system the parasympathetic

nervous system releases a hormone called

acline which slows down the heart rate

by reducing the sinus node discharge

rate this slowing down is called braad

cardia and is controlled by the the

vagus nerve whose cell bodies are in the

medal's cardioinhibitory region vagal

stimulation slows the heart but doesn't

affect the strength of the heart

contractions the brain also plays a role

in regulating heart rate through

impulses from the higher somatomotor

Central Command that go to the

Cardiovascular Center in the

Medela this ensures the heart and blood

vessels work together to optimize blood

flow and maintain blood pressure during

activity the Central Command has a

significant effect on heart rate during

physical activity and even at rest with

emotional states influencing

cardiovascular

responses when you're about to start

exercising your heart rate increases an

anticipation due to the increased

sympathetic activity and reduced

parasympathetic activity a phenomenon

known as the anticipatory heart rate

this increase is noticeable just before

intense physical effort the heart turns

on for physical activity due to the

increased sympathetic activity and the

decreased parasympathetic activity

combined with input from the brain

Central

Command feedback from joint and muscle

receptors occur as you begin to

move even in non-s Sprint activities

heart rate can reach 180 beats per

minute within 30 seconds of starting it

then increases gradually with plateaus

during the Run

itself all right not just higher centers

of the brain are involved in sending

information to the cardiovascular

centers the medala also receives sensory

input from a Cano receptors and chemo

receptors in blood vessels joints and

muscles these receptors monitor muscular

activity and adjust vagal or sympathetic

outflow to ensure an appropriate

cardiovascular response reflex neural

input from active muscle known as the

exercise pressure reflex and input from

the brain's motor areas which assess

movement type intensity and muscle

recruitment during Dynamic activity

feedback from meano receptors helps

regulate blood flow and blood pressure

Barrow receptors in the aortic Arch and

chotic sinus respond to changes in blood

pressure by slowing the heart rate and

dilating blood vessels when PR press

increases this mechanism is overridden

during physical activity to allow for

increased heart rate and blood pressure

but Barrow receptors still help prevent

excessively high blood pressure during

intense

activity as we have just discussed your

heart rate is well regulated by internal

and external mechanisms but these

control mechanisms can become faulty so

being able to Monitor and detect an ECG

and heart rate irregularities can be an

indicator of heart disease and these

irregularities are known as

arhythmia heart rhythm irregularities

often show up as extra beats or extra

cyles sometimes parts of the Atria can

become active prematurely and depolarize

before the SA node does causing a

premature atrial contraction or a

Pac premature ventricular contractions

or PVC can also happen between regular

beats these occasional extra cyes

usually go unnoticed during rest and can

be triggered by stress anxiety or

caffeine due to the effects of catacol

amines on the SA node removing these

triggers typically restores normal

Rhythm but if that doesn't work beta

blockers can help by blocking norpine

efference action on atrial

cells atrial arrhythmias don't usually

affect the heart's pumping ability mod

because the Atria contribute little to

ventricular

filling however if pac's occur in

succession they can cause atrial

fibrillation which is more

serious the most dangerous type of

arhythmia is ventricular fibrillation

when multiple points of the ventricles

are continuously stimulated disrupting

the normal coordinated contraction this

can lead to repetitive PVCs preventing

the ventricles from pumping blood

effectively reducing cardiac output and

blood pressure and causing rapid loss of

consciousness cardiopulmonary

resuscitation or CPR can simulate the

heart's pumping action and may reverse

fibrillation if CPR isn't effective an

automated or semi-automated

defibrillator can deliver a strong

electrical shock across the heart to

polarizing it and allowing the SA node

to restart a normal rhythm

I hope this video has provided you with

the information you require to be able

to address the following learning

objectives