Cardiovascular system - medsci
Terms
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- Cardiac Output
-
The volume of blood ejected by the left ventricle into the aorta (or the right ventricle into the pulmonary trunk) PER MINUTE
- Stroke Volume
- The volume of blood ejected by the ventricle during each contraction (systole)
- Cardiac Reserve
- The difference between a persons maximum cardiac output and their cardiac output at rest
- Preload
- The amount of stretch on the heart before it contracts
- Contractility
- The forcefulness by which the heart contracts
- Afterload
- The pressure that must be exceeded before ventricular ejection can begin
- Frank-Starlings Law of the Heart
- A greater preload (end diastolic volume)stretching cardiac muscle fibres just before they contract increases their force of contraction in systole
- At rest Stroke Volume
- 70mL/Beat
- At rest Cardiac Reserve
- 15L/min
- At rest Heart Rate
- 75Beats/min
- Venous Return
- The volume of blood returning to the heart from the vasculature every minute
- Ejection Fraction
- The fraction of the end diastolic volume that is ejected during an average heartbeat. Equal to stroke volume divided by end diastolic volume
- What percentage of the blood remains in the ventricles after each contraction?
- 40-50%
- What percentage of the EDV is the stroke volume at rest?
- 50-60%
- Which factors determine EDV?
-
1)Ventricular Diastole duration
2)Venous return - Heart Rate
- The number of heart beats per minute
- Positive inotropic agents
- Increase contractility, promoting Ca2+ inflow and strengthens force of the next contraction
- Negative inotropic agents
- Decrease contractility
- Where is the nervous system regulation of the heart centered in the brain?
- Cardiovascular centre, Medulla oblongata
- Proprioceptors
- Monitor limbic & muscle movements (stimulates quick rise in HR by sending nerve impulses)
- Chemoreceptors
- Monitor chemical changes in the blood
- Baroreceptors
- Monitor the stretching of major arteries and veins due to the blood flowing through them (blood pressure)
- 2 Important baroreceptors
-
1)Arch of aorta
2)Carotid arteries - Autorhythmicity
- The heart is able to continue beating rhythmically following removal from the body
- Impulses on cardiac accelerator nerves from the medulla oblongata trigger norepinephrine release which bind to?
- Beta-1 receptors on cardiac muscle fibres
- What does release of norepinephrine do in SA node fibres
- Increases rate of spontaneous depolarisation so SA & AV nodes fire impulses more rapidly, then heart rate increases
- What does release of norepinephrine do in contractile fibres in atria and ventricles?
- enhances Ca2+ entry through voltage gated channels, increasing contractility, greated volume of blood is ejected during systole
- Sympathetic neurons used for output to heart
- Cardiac Accelerator Nerves
- Parasympathetic neurons used for output to heart
- Vagus Nerves
- What does release of acetylcholine do in SA node fibres?
- Decreases rate of spontaneous depolarisation in autorhythmic fibres, then heart rate decreases
- Do vagal fibres innervate or have an effect on the contractility of ventricular muscle?
- No, changes in parasympathetic activity have little effect on the contractility of the ventricles
- Which neurotransmitter is the parasympathetic system associated with?
- Acetylcholine
- Which neurotransmitter is the sympathetic system associated with?
- Norepinephrine
- Increased sympathetic stimulation, catecholamines, glucagon or thyroid hormones in the blood and increased Ca2+ are what kind of agents?
- Positive inotropic agents
- Tachycardia
- Elevated resting heart rate
- Adrenal Medullae releases which hormones that enhance heart pumping effectiveness?
- Epinephrine and Norepinephrine
- Bradycardia
- A resting heart rate under 50 beats/min
- Increased body temperature INCREASES or DECREASES heart rate?
- INCREASES heart rate
- Instrinsic regulation of Stroke volume
- FOrce of contraction, governed by degree of stretch at the end of diastole
- End Diastolic Volume (EDV)
- The volume of blood in the ventricle at the end of diastole (relaxation)
- Extrinsic regulation of Stroke volume
- Activity of the autonomic nervous system and the levels of various hormones
- Stroke work
-
Change in volume x change in pressure
[The AREA of the pressure-volume curve for ventricular contraction] - In embryonic development, only __% of cardiac muscle fibres become autorhythmic fibres
- 1%
- Pacemaker potential
- Spontaneous depolarization of the SA node
- Nerve impulse from ANS and blood-borne epinephrine do what to the heart?
-
Modify the TIMING & STRENGTH of the heart beat
[NB: They DO NOT establish the RHYTHM] - SA nodes initiate a action potential every ____?
- 0.6 seconds (100 times per minute)
- P wave
- Atrial Depolarization
- QRS Complex
- Rapid Ventricular Depolarization
- T wave
- Ventricular Repolarization
- Auscultation
- Listening to sounds within the body
- Blood Hydrostatic pressure is due to?
- Pressure that the water in blood plasma exerts on the capillary walls
- Blood Colloid Osmotic Pressure is due to?
- Colloidal suspension of blood plasma proteins
- BHP pushes fluid ___ capillaries and ____ interstitial fluid
-
"out of" capillaries
"into" interstitial fluid - IFHP pushes fluid ___ capillaries and ___ interstitial fluid
-
"into" capillaries
"out of" interstitial fluid - BCOP pulls fluid ___ interstitial fluid and ___ capillaries
-
"from" interstitial fluid
"into" capillaries - IFOP pulls fluid ___ interstitial fluid and ___ capillaries
-
"into" interstitial fluid
"from" capillaries - 20 Litres of blood filter out of capillaries. How any litres are reabsorbed and how many go to the lymphatic capillaries?
-
17 L are reabsorbed
3 L go to lymphatic capillaries - Systolic Blood Pressure
- Highest pressure in ARTERIES during systole
- Diastolic Blood Pressure
- Lowest pressure in ARTERIES during diastole
- Mean Arterial Pressure (MAP)
-
The average blood pressure in arteries
MAP= Diastolic BP + 1/3 (Systolic BP-Diastolic BP) - What is the normal volume of blood in an adult?
- 5L
-
The Sympathetic response includes:
Vasoconstriction/Dilation
Diameter increase/decrease
Blood Pressure increase/decrease -
Vasoconstriction
Diameter decrease
Blood Pressure Increase -
The Parasympathetic response includes:
Vasoconstriction/Dilation
Diameter increase/decrease
Blood Pressure increase/decrease -
Vasodilation
Diameter Increase
Blood Pressure Decrease - Total Peripheral Resistance (TPR) or Systemic Vascular Resistance (SVR)
- All Vascular resistances offereb by systemic blood vessels
- Vasomotor tone
- Tonic contraction setting the resting level of systemic vascular resistance. (For the smooth muscle in blood vessel walls)
- Carotid Sinus Reflex
- Regulates blood pressure in the brain
- Aortic Reflex
- Regulates systemic blood pressure
- Sensory neurons are
- Afferent - To the Brain
- Motor Neurons are
- Efferent - Away from the Brain
- Blood Pressure is due to three things:
-
-Cardiac Output
-Blood Volume
-Total Peripheral Resistance (Or SVR) - When blood Volume falls or Blood pressure decreases, kidneys secrete RENIN which, in conjunction with angiotensin converting ACE enzyme produces the hormone ANGIOTENSIN II. How does this restore (inc.) blood pressure? (2)
-
1)Angiotensin is a vasoconstrictor - This increases systemic vascular resistance
2)Stimulates kidney adrenal cortex secretion of aldosterone - increases Na+ and water reabsorption and thus blood volume - Antidiuretic hormone (ADH) produced by the hypothalamus and the posterior pituitary,has two functions
-
1)Increases blood volume and water reabsorption
2)Causes Vasoconstriction - Atrial Natriuretic Peptide (ANP) prodiced by the atrial cells of the heart has two functions
-
1)Decreases blood volume by promoting the loss of salt and water in the urine
2)Causes Vasodilation - Autoregulation
- The ability of a tissue to automatically adjust its blood flow to match its metabolic demands.
-
In systemic cicuits, the autoregulation response causes dilation of blood vessels in response to low O2, while in pulmonary, the blood vessels constrict.
Why does the pulmonary system do this? - Ensuring that blood bypasses aveoli that are poorly ventilated and rather flow to better ventilated areas of the lung.