ORTCITIAEE: Control of heart rate Flashcards
What happens in the diastole stage of the cardiac cycle?
Atria relaxed
Ventricles relaxed
(the heart is resting at this stage)
What happens in the atrial systole stage of the cardiac cycle?
Atria contract
Ventricles relaxed
What happens in the ventricular systole stage of the cardiac cycle?
Atria relaxed
Ventricles contract
Give the 3 stages of the cardiac CYCLE:
1) Diastole
2) Atrial systole
3) Ventricular systole
cycle then repeats!!!
The cardiac cycle begins with the heart at rest. This stage is called ______.
Diastole
When we want to move a muscle, our body generates a small amount of electricity called an _______ _______.
electrical impulse
electrical impulses are sent from our brain down a sequence of _____.
Neurones
Cardiac muscles are stimulated by an electrical impulse from where?
The cardiac muscle itself.
When a muscle contracts due to impulses from the nervous system is is initiated by an ______ stimulus.
External
When a muscle initiates its own contraction, it is initiated by a _____ stimulus.
myogenic
Cardiac muscle is myogenic. What does this mean?
It stimulates its own contraction.
Where is the sinoatrial node (SAN) found?
Right atrium
What does the sinoatrial node (SAN) do?
Creates electrical impulses
How is the atrial systole stage stimulated?
- The sinoatrial node stimulates electrical impulses which travel across the atria causing them to contract (both the left and right atria even though the SAN is only found in the right).
- This contraction forces blood out of the atria into the ventricles.
What is another name given to the electrical impulses created by the SAN?
Wave of depolarisation
Where do the electrical impulses produced by the sinoatrial node travel to ?
The atrioventricular node (AVN)
Electrical impulses generated in the sinoatrial node travel to the atrioventricular node. Where do they travel next?
Bundle of His
What is the Bundle of His made from?
Purkyne tissue
What does the Bundle of His do?
- The structure of it travels down the middle of the heart (between the two halves) and around the ventricles
- Electrical impulses that travel down the ventricles to the bottom base of the heart, and up towards the ventricles.
- This stimulates ventricular systole, causing the ventricles to contract
In which stage of the cardiac cycle are both the atria and ventricles relaxed?
Diastole
The sinoatrial node triggers the ____ to contract.
Atria
Why is the transmission of electrical impulses from the sinoatrial node to the atrioventricular node slightly delayed (1/10th of a second)?
Allows for blood in the atria to fully empty into the ventricles.
Purkyne tissues conducts electrical impulses that cause the _______ to contract.
ventricles
Why don’t the electrical impulses produced in the atria enter the ventricles?
- There is a layer of non-conductive tissue between the atria and ventricles.
- Ensures that the ventricles do not contract at the same time as the atria.
The electrical impulse travels from the sinoatrial node to the atrioventricular node with a _____ of 1/10th of a second.
delay
(this delay ensures that all the blood has left the atria and goes into the ventricle)
What are the two branches of the autonomic nervous system?
- Sympathetic
- Parasympathetic
During rest our ________ branch within the autonomic nervous system is activated.
parasympathetic
During distress our ________ branch within the autonomic nervous system is activated.
sympathetic
Is the parasympathetic or sympathetic nervous system responsible for a stress response?
sympathetic
What are the two types of receptors that send impulses to the medulla?
- Chemoreceptors
- Pressure receptors
Where are chemoreceptors located?
In the walls of blood vessels
What do chemoreceptors do?
Detect changes in blood pH
Where are pressure receptors located?
Neck and heart
What do pressure receptors do?
Detect changes in blood pressure.
Which part of the nervous system regulates involuntary processes such as heart rate?
Autonomic nervous system
The sympathetic nervous system _______ effectors and increases processes such as heart rate.
stimulates
The parasympathetic nervous system ______ effectors and slows processes such as heart rate.
inhibits
What is the body’s cardiac control centre?
Medulla oblongata
How does the body correct low blood pH?
- Low blood pH is detected by chemoreceptors.
- These receptors send impulses along the sympathetic pathway.
- These impulses arrive at the medulla oblongata which sends further impulses to the SAN to increase heart rate.
How does the body correct high blood pressure?
- High blood pressure is detected by pressure receptors.
- These receptors send impulses along the parasympathetic pathway
- These impulses arrive at the medulla oblongata which sends further impulses to the SAN to decrease heart rate.
