Heart physiology Flashcards
Diastolic volume (DV), telediastolic volume (TDV) or end-diastolic volume (EDV)
it is the volume of blood within the ventricles at the end of the diastole (120 – 130 ml)
Stroke volume (SV) or ejection volume:
total volume of blood ejected during a ventricular systole (70 – 85 ml/beat).
End systolic volume (ESV)
volume of blood that remains in the ventricle at the end of the ventricular systole.
ESV = EDV – SV = 130 – 70 = 60 ml
Ejection fraction
represents the percentage of EDV (End diastolic volume) blood that is pumped with each heart beat:
EF = (SV/EDV) · 100
This value is around 55% in normal conditions and rises up to 75% during exercise.
Heart rate (HR)-Pulse
it is the number of heart beats or contractions per minute (At rest: 70 beats/min, although it may vary between 55 and 100).
Heart minute volume (Vm)
it is the volume of blood pumped by the heart in one minute. In a normal adult nearly 6 litres (5600 ml):
Vm = SV · HR
What happens during rest with the cardiac output?
At rest the cardiac output is about 5 l/min, but when the metabolic demand increases, the heart is able to increase the heart minute volume between 4 – 7 times.
How can we modulate the cardiac output?
The cardiac output can be modulated by intrinsic and/or extrinsic mechanisms that affect the SV or the HR.
How can we change the stroke volume?
Due to:
Intrinsic factors
- EDV (End diastolic factors)
- ESV (End systolic factors)
What are EDV (End diastolic factors)
• Venous return (Preload)
• Atrial contraction
• Time for ventricular filling
(duration of the diastole)
What are ESV (End systolic factors) ?
Force of ventricular contraction (Contractility)
• Degree of stretch on the heart (Frank-Starling law of the heart)
• Afterload
• State of the semilunar valves
Changes in stroke volume?
- preload
- contractility
- afterload
Frank Starling law of the heart
The more the heart fills with blood during diastole, the greater force of contraction during systole.
This positive relationship is known as the Frank–Starling Law of the heart.
What are extrinsic factors?
- hormonal changes
- control by the ANS
To what can a hormonal and ANS change lead?
- Contractility of the heart
- Afterload/ peripheral resistance
By which receptors is contractility and peripheral resistance mediated?
- Baroreceptors
- Mechanoreceptors
- Chemoreceptors
Which factors can lead to changes in the heart?
- metabolic factors
- physical activity
- nervous mechanisms
- humoral mechanisms
What are metabolic factors?
- Temperature
- pH
- Metabolic activity
What do you understand by nervous mechanisms?
- ANS
- Baroreceptors
- Mechanoreceptors
- Chemoreceptors
What are humoral mechanisms?
Catecholamines
Afferent/ sensory
INPUT to cardiovascular center
- from higher brain center
- from propioreceptor
- from baroreceptor
- from chemoreceptor
Efferent/ motor
OUTPUT to effectors
- Heart (Parasympathetic and Sympathetic)
- Blood vessels
What do proprioreceptors do?
monitor joint movements
What do baroreceptors do?
Monitor blood pressure (p-b)
What do chemoreceptors do?
Monitor blood activity CO2, O2, H+
What does the Parasympathetic system do?
decrease heart rate
What does the sympathetic system do on the heart?
increase heart rate and contractility
What does the sympathetic system do on the blood vessels?
vasocontriction
Higher brain structures produce the changes of:
cerebral cortex, limbic system, hypotalamus
- Anticipation of competition
- Increase in body temperature
The peripheral autonomic sensory signals reserve the signals from:
- Mechanoreceptors
- Baroreceptors
- Chemoreceptors
- Proprioreceptors
The receptors (Baroreceptor etc.) send afferent signals to….
The cardiovascular center
Mechanoreceptors
In ATRIA AND LARGE VEINS
Detect increases in blood volume.
• Information travels through VAGUS nerve (X) toward medulla oblongata.
Ex: When urine production increases… TRIGGER sympathetic response
Baroreceptor
In arch of the aorta and carotid sinus
- Detect changes in blood pressure.
- VAGUS and GLOSOPHARYNGEAL nerves conduct information to medulla oblongata.
Ex: When BP increases, it is produced… INCREASE of parasympathetic activity DECREASE of sympathetic activity
Chemoreceptors
In carotid bodies and aorta
Detect changes in PO2, PCO2, and pH.
Ex: When PCO2 increases and pH decreases, the medulla is informed and it is produced…
INCREASE of sympathetic activity DECREASE of parasympathetic activity
Proprioreceptors
Monitor the position of muscles, joints, ligaments, tendons…
• As physical activity begins, proprioceptors send nerve impulses at an
increased frequency to the cardiovascular center.
• Proprioceptor input is a major stimulus for the quick rise in heart rate that occurs at the onset of physical activity.
Ex: When physical activity begins, it is produced… INCREASE of sympathetic activity
In which nerve can we find the Parasympathetic?
Vagus nerve X
Causes decrease in heart rate
In which nerve can we find the Sympathetic? Regarding to the heart
In cardiac accelerator nerves,
Causes increase in contractility and heart rate
In which nerve can we find the Sympathetic? Regarding to the blood vessels
vasomotor nerve
The sympathetic division also continually sends impulses to smooth muscle in blood vessel walls via vasomotor nerves. The result is a moderate state of tonic contraction or vasoconstriction, called vasomotor
How can we increase the heart rate? (syntifical)
Increased rate of spontaneous depolarisation in SA node and AV node
How can we increase the stroke volume?
by increased contractility of atria and ventricles
How can we decrease the heart rate?
By decreased rate of spontaneous depolarisation in SA node and AV node
What does postive chronotropic effect mean?
The pacemaker cells increase the heart rate
What does positive dromotropic effect mean?
The conductive cells increase the conduction speed of the electrical impulse (dromo- Trommel)
what does positive entropic effect mean?
The contractile cells increase the contractile strength
The Sympathetic system acts on:
Noradrenaline, ß- receptor and as a positive effect
The parasympathetic system acts on:
Aceticholine, muscarinic M2 receptor in heart and negative effect
What does negative chronotropic effect mean?
The pacemaker cells decrease the heart rate
What does negative dromotropic effect mean?
The conduction cells decrease the conduction speed of the electrical impulse
Substances released in blood that act on the smooth muscle of arterioles.
They influence:
Atrial pressure: afterload
- Vasoconstriction
- Vasodilation
What happens after blood pressure falls below normal?
Regarding:
- Vessels
- Heart
And how does it happen?
Vessels: Vasoconstriction
Heart: increase HR and force of contraction
In Adrenaline and Noradrenaline (Adrenal medulla)
Angiotensin (Kidneys)
Antidiuretic hormone (ADH or vasopressin; hypothalamus). Very potent.
Endothelin (Endothelium)
What happens after BP increases above normal?
regarding: vessels
And how does it happen?
Vessels: Vasodilation
Nitric oxide (Endothelium) Bradykinin
Histamine
Prostaglandins
Atrial Natriuretic peptide (Atrial myocytes)
What happens by sympathetic stimulation?
Regarding:
- Heart rate
- Stroke volume
- cardiac output
↑ HR; ↑ SV; ↑ CO
What happens by parasympathetic stimulation?
Regarding:
- Heart rate
- Stroke volume
- cardiac output
normalizes CO
What happens by increase in venous return
Regarding:
- Heart rate
- Stroke volume
- cardiac output
normal HR; ↑ SV; ↑ CO
What happens by reduction of Heart rate?
Regarding:
- Heart rate
- Stroke volume
- cardiac output
↑ EDV; ↑ or ↓ CO
What happens by increase of Heart rate?
Regarding:
- Heart rate
- Stroke volume
- cardiac output
↓ venous return ↓ SV ↓ CO
What happens by exercise?
Regarding:
- Heart rate
- Stroke volume
- cardiac output
↑HR↑SV↑CO
