Flashcards in Circulation and respiration - Part 2 - 2 Deck (67)
What determines cardiac output?
What is heart rate?
How fast the heart beats
What is stroke volume?
How much blood leaved the heart with every beat
How can heart rate be changed?
Through autonomic or hormonal input
Describe the autonomic inputs to heart rate.
Adrenergic increases heart rate - epineprhine
Cholinergic decreases heart rate - acetylcholine
_______ events upregulate the adrenergic response
__________ works on the cholinergic system.
Describe how temperature affects cholinergic stimulation of heart rate.
In cold temperatures, initially, heart rate decreases due to increased cholinergic stimulation until acclimation occurs, whereby the HR gets more constant.
What are the daily regulators of heart rate?
adrenergic and cholinergic response
________ control is more a seasonal control of heart rate.
What are the three factors that control stroke volume?
1 - Afterload or arterial pressure
2 - Preload
3 - Ventricular strength
Which of the three factors that control stroke volume is the most important?
What is afterload? How does it affect SV?
Afterload or arterial pressure is the amount of blood in the bulbus (if sticking with teleosts) when the ventricle contracts.
If there is backlog, or blood remaining in the bulbus, this will decrease the amount of blood that can leave the ventricle.
When would afterload be an issue?
Doesnt happen that often in fish.
In a diseased state, bulbus is less elastic and reduces stroke volume
What is preload and how does it affect SV?
How much blood is in the heart at the start of contraction.
If there is more blood in the heart before the next beat, more of it can be put out
What can affect preload?
heart rate; if HR is too fast, not enough time to fill up and thus reduced SV
What is ventricular strength?
How strongly the ventricle contracts.
Describe Starling's law of the heart.
Cardiac myotomes have increased force of contraction as fiber length increases
Contractility of the heart is affected by what?
cholinergic and adrenergic stimulation
The ventrcile wall is full of muscle fibres called __________.
When the ventricles contract, the fibres pull against each other the generate _________.
What pulls the fibres apart in the heart?
What is the relationship between filling pressure and stroke volume?
As filling pressure increases, the fibres get pulled apart generating a larger stroke volume
Which fish doesnt really follow the Starling's law of the heart?
Essentially, their heart is always pumping as hard as possible, always at max SV
How does calcium affect ventricular strength?
More calcium to the muslces makes them contract more powerfully.
How does adrenergic stimulation affect ventricular strength?
Adrenergic --> increase ventricular strength
cholinergic --> decrease ventricular strength
How does acidosis affect ventricular strength?
Acidosis or acid buildup decreases contractility.
If the heart is working too hard, get buildup of acid; or
pH of water can affect fish heart ability to deliver blood to the tissues
What does the RAS react to?
Low blood pressure of hypotension
Describe the RAS.
Series of cells located at the glomerular junction that function to detect blood pressure going into the tubules.
When blood pressure is low, causes them to secrete renin.
Renin then converts angiotensin 1 to angiotensin 2.
Angiotensin 2 will act on arteries and capillaries throughout the body to constrict them and increase blood pressure.
Angiotensin 2 will also induce drinking behaviour (if saltwater fish)