Ques med physilogy Flashcards
What is the state of the atrioventricular (AV) valves and semi-lunar valves during the inflow phase of the cardiac cycle?
AV valves open, semi-lunar valves closed
Binding of adrenaline/noradrenaline to α1-adrenoceptors leads to [Blank] of blood vessels and [Blank] force of myocardial contraction.
Vasoconstriction
Increased
What is the cause of a dicrotic notch at the end of systole in aortic pressure tracings?
The closure of the aortic valve
What is the “funny current” ?
The “funny” current is so called because at the time of its discovery, its properties as a current were unusual compared to those of other known ion channels – it is a mixed sodium/potassium inward current that is activated upon hyperpolarisation. Activation of the “funny” current increases the gradient of the pre-potential slope
Vagus nerve fibres primarily secrete which hormone to decrease the activity of the sinoatrial node?
Acetylcholine
What is the equation for Poiseuille’s law of flow?
F = ΔPπr^4/8η
Where:
F = Flow rate
ΔP = Pressure gradient (difference in pressure from start of blood vessel to end)
R = Resistance to blood flow
η = Viscosity of blood
r = Radius
What can the mean arterial pressure (MAP) be used to indicate?
Indicates how well the vital organs of the body are being perfused.
What type of muscle controls pupil diameter?
Smooth muscle
What are the two types of action potential in the heart?
The ventricular (non-pacemaker) action potential and the sino-atrial (pacemaker) potential
What happens during the depolarisation phase of the cardiac action potential (phase 0)?
Rapid influx of Na+ ions into the cell, causing a sharp rise in membrane potential.
What are the 4 main phases of the cardiac cycle?
Inflow
Isovolumetric contraction
Outflow (ejection)
Isovolumetric relaxation
What type of ion transfer occurs at Stage 4 of ventricular myocyte action potentials?
Potassium channels remain open but there is no net flow of ions
The PR interval reflects the functioning of which node?
Atrioventricular node
During myocardial relaxation, calcium ions are removed from the cardiomyocyte cytoplasm via which 2 main mechanisms?
Sodium-calcium exchanger (NCX)
Sarcoplasmic reticulum calcium-ATPase pump (SERCA)
What is the definition for the PR interval?
Time between the onset of atrial depolarisation to the start of ventricular depolarisation
What is the tunica externa/adventitia primarily formed of?
(Mainly) connective tissue
What are the 5 phases of the cardiac action potential?
Phase 0 - Depolarisation
Phase 1 - Early repolarisation
Phase 2 - Plateau
Phase 3 - Rapid repolarisation
Phase 4 - Resting potential
What is meant by the vicious cycle of heart failure?
Decreased cardiac output leads to excessive sympathetic stimulation. This works to increase cardiac output, but at the expense of overworking the heart and increasing cardiac ischaemia (leading to progressively decreased output).
The “funny” current has very [blank] kinetics compared with other types of currents.
Slow
Which blood vessel is not typically characterized by a thick tunica media composed of elastic fibers?”
Capillaries are not typically characterized by a thick tunica media composed of elastic fibers.
Which receptors does noradrenaline primarily bind to on blood vessels to trigger smooth muscle contraction?
Alpha-1 adrenoceptors
Muscle contraction [Blank] venous return while muscle relaxation [Blank] venous return.
Increases
Decreases
For sympathetic control of blood vessels, what is the main neurotransmitter?
Noradrenaline
Which types of muscle cells have many mitochondria and possess a sarcoplasmic reticulum and T-tubule?
Cardiac and skeletal muscle cells.
What effect does increased heart rate have on coronary blood flow?
I
t decreases blood flow as it reduces time in diastole. Most coronary perfusion takes place during diastole.
Where in arteries is specialized elastic tissue found?
Internal and external elastic lamina
What is the normal heart rate in bpm?
60-100bpm
What are the key differences between sympathetic and parasympathetic neural pathways?
Length of axon: Parasympathetic = long pre-ganglionic and short post-ganglionic axons; sympathetic = short pre-ganglionic and long post-ganglionic axonsActions: Parasympathetic = rest and digest; sympathetic = fight or flightNeurostransmitter: Parasympathetic = Acetylcholine only; sympathetic = acetylcholine or noradrenalineDiscretion: Parasympathetic = more discrete (1 pre-ganglionic axon to 1 post-ganglionic axon; sympathetic = less discrete (1 pre-ganglionic to 20 post-ganglionic)
How can the left ventricular ejection fraction be calculated?
Dividing the stroke volume (SV) by the end-diastolic volume (EDV) (LVEF = SV/EDV * 100%)
The “funny” current is activated by [blank] rather than depolarisation.
Hyperpolarisation
What is the name of the circuit that is formed between the embryo and the placenta?
Umbilical circuit
Why is heart failure associated with increased Ca2+ efflux from the cardiomyocyte?
The sarcolemmal Na+/Ca2+ exchanger is upregulated
What is meant by the term stroke work?
The work done by the ventricles to eject the stroke volume into the aorta.
What happens during the ejection phase of the cardiac cycle?
Deoxygenated blood is ejected from the right ventricle into the pulmonary artery (to supply the lungs) and oxygenated blood is ejected from the left ventricle into the aorta (to supply the rest of the body).
What effect does acetylcholine have on the heart ventricles?
None - the ventricles have no parasympathetic supply, and therefore acetylcholine has no effect on the ventricles.
Binding of adrenaline/noradrenaline to β1-adrenoceptors in the cardiovascular system leads to which 4 effects?
Positive inotropy
Positive chronotropy
Positive lusitropy
Positive dromotropy
What is the afterload?
The pressure which the heart must work against to eject blood during ventricular systole
What happens during isovolumetric relaxation?
The ventricles relax and the pressure in the aorta/pulmonary artery once again exceeds the ventricular pressure, triggering the semi-lunar valves to close.
How can the stroke volume be measured?
Doppler ultrasound/echocardiography
What happens during isovolumetric contraction?
Both ventricles contract simultaneously but the atrioventricular (AV) valves and semi-lunar valves remain closed, causing the ventricular pressure to increase.
If the arterial blood pressure increases too quickly, the stretch on the arterial walls [Blank] and the baroreceptors fire action potentials [Blank] frequently.
Increases
More
Oxygenated blood enters the left atrium via which blood vessel?
Pulmonary vein
Give examples of clinical scenarios in which reactive hyperaemia may occur
Reactive hyperaemia occurs in response to tissue ischaemia. Therefore, examples include: tourniquet removal, coronary artery reperfusion (e.g. CABG, angioplasty, thrombolysis), unclamping an artery following surgery, Raynaud’s phenomenon (vasospasm of peripheral arteries)
What is the definition for the QT interval?
Time between the start of the QRS complex and the end of the T wave
What is Poiseuille’s law of resistance?
The resistance to blood flow is directly proportional to the length of the blood vessel and the viscosity of the blood, and inversely proportional to the blood vessel radius to the 4th power.
Where does calcium bind, within the troponin complex, to exert an effect on actin and myosin?
Troponin C
At which point of the cardiac conduction pathway is there a short delay (120ms) before the action potential continues?
Atrioventricular node (AVN)
Where are discontinuous capillaries found in the body?
Bone marrow, lymph nodes, adrenal glands, liver and spleen.
What happens during diastole?
Both atria and ventricles are relaxed. Blood flows passively from the atria to the ventricles.
Excessive activation of which system is associated with Raynauds syndrome?
Sympathetic system
What effect does reduced transient concentration of Ca2+ have on heart muscle action in heart fialure?
Results in a reduced contractile force
During a wave of depolarisation, calcium ions enter cardiomyocytes via which types of channels found in the membrane?
L-type calcium channels
What does positive inotropy refer to?
Increased force of myocardial contraction
What is blood vessel autoregulation?
The intrinsic ability of blood vessels to maintain a constant flow of blood up to a specific point, regardless of changes to perfusion pressure
What are Purkinje fibres?
Network of specialised conductance cells which carry the cardiac action potential back up through both ventricles
The concentration of which type of ion is primarily responsible for the force of myocardial contraction?
Calcium ions
What happens during atrial systole?
Both atria contract simultaneously to force any remaining blood into the ventricles.
What two types of adrenoceptor are found in blood vessels?
Alpha-1 adrenoceptors and Beta-2 adrenoceptors.
What effect does an increase in carbon dioxide partial pressure of blood in the cerebral circulation have on pH?
It decreases the pH. This causes direct vasodilatation and also enhances the release of nitric oxide, a vasodilator
What are the roles of the different troponin complex components?
)
Troponin C (calcium ion binding site), Troponin I (inhibition of ATP hydrolysis), Troponin T (structural connection to tropomyosin)
What does the T wave indicate on an ECG?
Ventricular repolarisation
What happens to venous return when changing from a lying to a standing position?
Temporarily decreases due to gravity
Most vascular beds are innervated by which branch of the autonomic nervous system?
Sympathetic
Which types of muscle cells have many mitochondria and possess a sarcoplasmic reticulum and T-tubule?
both cardiac and skeletal muscle
Which blood vessel controls perfusion through capillary beds?
Arterio-venous anastomoses
What is the “funny” current?
A mixture of sodium (Na+) and potassium (K+) current which is activated by hyperpolarisation at low voltages (usually around -60/-70mV).
What happens to venous return during sympathetic activation of the venous system?
Increases
What happens to venous return during sympathetic activation of the venous system?
Increases
What is the definition for mean arterial pressure?
The average pressure of the arteries during one cardiac cycle
Why does blood entering via the IVC pass from the right to the left atrium through the foramen ovale, whereas blood entering via the SVC passes from the right atrium to ventricle?
This is due to the orientation of the tricuspid valve facing the SVC, which force blood through the tricuspid valve from the right atrium to ventricle
On the Frank-Starling curve, which variables are usually placed on the X-axis and Y-axis?
X-axis: end-diastolic volume
Y-axis: stroke volume
Where are nuclei located in the skeletal muscle cells?
They are located peripherally
Most vascular beds are innervated by which type of nerve?
Sympathetic nerves
In which blood vessels is there the largest fall in blood pressure and velocity?
Arterioles
What is the normal heart rate bpm?
60-100bpm
What type of ion transfer occurs at Stage 4 of ventricular myocyte action potentials?
Potassium channels remain open but there is no net flow of ions
During the Valsalva manoeuvre, what happens to the venous return?
Decreases due to compression of thoracic veins
What causes reactive hyperaemia?
Reactive hyperaemia describes the vasodilatation and transient increase in blood flow that occurs in response to tissue ischaemia. During the period of ischaemia there is tissue hypoxia and a build-up of metabolic waste products. The hypoxia and waste products (e.g. adenosine) directly act upon vascular smooth muscle to cause vasodilation.
Why is heart failure associated with increased Ca2+ efflux from the cardiomyocyte?
The Na+/Ca2+ exchanger in the sarcolemma is upregulated
What is venous return?
The flow of blood back to the heart via the venous system
Parasympathetic activation of the sinoatrial node/atrioventricular node leads to which 2 main effects on the heart?
Decreased heart rate (negative chronotropy) and decreased force of myocardial contraction (decreased inotropy)
If the blood pressure drops too quickly, the baroreceptor reflex [Blank] the activity of the sympathetic nervous system (SNS) and [Blank] the activity of the parasympathetic nervous system (PNS).
Increases
Decreases
What type of ion transfer occurs at Stage 2 of ventricular myocyte action potentials?
Outflow of potassium and inflow of calcium ions
At birth, what happens to the foramen ovale?
The foramen ovale closes at birth when the pressure in the atrium increases as the baby takes its first breath. This causes the flexible septum primum to push up against the septum secundum, sealing off the foramen ovale and forcing blood into the pulmonary circulation.
What are the End-Diastolic Volume and End-Systolic Volume?
The volume of blood in the left ventricle at the end of diastole and systole respectively
What is the purpose of the short delay (120ms) at the atrioventricular node during normal cardiac conduction?
Allows the atria to fully empty before the ventricles contract
Which phenomenon is responsible for opening ryanodine receptors during contraction in cardiac myocytes, causing a release of calcium ions from sarcoplasmic reticulum stores?
Calcium entry
What does positive lusitropy refer to?
Increased myocardial relaxation
What is the equation for blood flow through a blood vessel?
Flow = Change in pressure/Resistance (F = ΔP/R)
What does positive chronotropy refer to?
Increase in heart rate
Cardiac myocytes have a high concentration of which organelle to generate large amounts of ATP for cardiac contraction?
Mitochondria
During a sudden decrease in blood pressure, activation of the sympathetic nervous system and deactivation of the parasympathetic nervous system leads to which 3 key changes?
Vasoconstriction of arteries/arterioles
Increased heart rate
Increased force of myocardial contraction
What affect does increased heart rate have on coronary blood flow?
It decreases blood flow as it reduces time in diastole
Deoxygenated blood enters the right atrium via which blood vessel?
Vena cava
What do the terms End-diastolic volume and End-Systolic Volume mean?
End-diastolic volume = The volume of blood in the left ventricle at the end of diastole End-systolic volume = The volume of blood in the left ventricle at the end of systole
What is the stroke volume (SV)?
Volume of blood pumped by the left ventricle per beat
What is meant by the term ‘capacitance vessel’?
Vein
What is the Valsalva manoeuvre?
A breathing method which involves moderately forceful exhalation against a closed airway (i.e. by closing your mouth or pinching your nose shut).
In ventricular myocyte action potentials, at which stage is there a simultaneous outflow of potassium ions and inflow of calcium ions?
Stage 2 (Plateau stage)
What condition can phentolamine be used to treat, and why?
Phaeochromocytoma, a tumour of the adrenal medulla. Patients present with high circulating levels of catecholamines (noradrenaline and adrenaline) and are extremely hypertensive. Phentolamine inhibits the vasoconstriction actions of noradrenaline by inhibiting the Alpha1-receptors.
What are the three layers of the vessel wall, from the outer to inner layer?
Tunica adventitia (outermost layer)
Tunica media
Tunica intima (innermost layer)
What effect does Stimulation of alpha-1 adrenoceptors have on vascular smoothmuscle?
Contraction of smooth muscle
What type of ion transfer occurs at Stage 1 of ventricular myocyte action potentials?
Outflow of potassium ions
Which muscle types have a striated appearance?
Cardiac muscle, skeletal muscle
Where are the main baroreceptors of the body located?
Carotid sinus and aortic arch
What is the main neurotransmitter of vasodilation in cerebral circulation and penile erectile tissue?
Nitric oxide.
What happens during the rapid repolarisation phase of the cardiac action potential (phase 3)?
Ca2+ channels close while K+ channels remain open. The rapid efflux of K+ ions out of the cell causes a sharp decrease in membrane potential.
Which blood vessels has the largest total cross-sectional area and contains blood that travels at the lowest mean velocity?
Capillaries
What is the “funny current” ?
The funny current is the name given to the slow and continuous flow of sodium ions into resting cardiomyocytes located in the pacemaker regions of the heart. This funny sodium current entering the cells allows the cells to depolarise spontaneously and, upon reaching threshold depolarisation, an action potential will be generated.
Which hormone stimulates Alpha1-adrenoceptors to cause smooth muscle contraction?
Noradrenaline
What is the definition for stroke volume?
The volume of blood pumped by each ventricle per beat
What is the end-diastolic volume (EDV)?
Volume of blood in the ventricles following diastole (heart relaxation)
Sympathetic activation of the sinoatrial node/atrioventricular node leads to which 2 main effects on the heart?
Increased heart rate (positive chronotropy) and increased force of myocardial contraction (increased inotropy)
What type of ion transfer occurs at Stage 2 of ventricular myocyte action potentials?
Eflux of potassium ions and influx of calcium ions
Which valves are responsible for producing the second heart sound (S2)?
Semi-lunar valves closing
What is the name of the valve formed by the septum primum and septum secundum?
the foramen ovale.
What type of ion transfer occurs at Stage 0 of ventricular myocyte action potentials?
Inflow of sodium ions
What does the Frank-Starling curve show?
As the end-diastolic volume (EDV) increases, the stroke volume also increases
Provided that other factors remain constant, what does the Frank-Starling Law ensure?
Ensures that the volume of blood pumped by the heart per cycle (stroke volume) can change depending on the volume of blood in the heart after diastole (EDV).
Roughly how long does each cardiac action potential last?
200-400ms
What is the state of the atrioventricular (AV) valves and semi-lunar valves during the isovolumetric contraction phase?
AV valves closed, semi-lunar valves closed
What is the main neurotransmitter of vasodilation in cerebral circulation and penile erectile tissue?
Nitric oxide
What are the key components of a normal ECG trace?
P wave
PR interval
QRS segment
ST segment
T wave
QT interval
The first stage of the cardiac conduction pathway involves an action potential being generated by which node?
Sinoatrial node (SAN)
Postganglionic fibres from the sympathetic trunk primarily release which hormone to increase sinoatrial node activity?
Noradrenaline
What is the baroreceptor reflex?
A reflex which involves pressure receptors (baroreceptors) which detect changes in arterial pressure and initiate a corresponding response.
What two types of adrenoceptor are found in blood vessels,?
alpha-1 adrenoceptors and beta-2 adrenoceptors.
What does the QRS complex indicate on an ECG?
Ventricular depolarisation
What effect does PaO2 have upon the cerebral circulation?
Within normal physiological limits, PaO2 has no effect on cerebral blood flow. Only if PaO2 is below a certain threshold (<55mmHg) does oxygen have a role in increasing cerebral blood flow.
What is the state of the atrioventricular (AV) valves and semi-lunar valves during the outflow/ejection phase of the cardiac cycle?
AV valves closed, semi-lunar valves open
What is the best approximation of the ejection fraction of a human under normal physiological circumstances?
60%
What is the equation for cardiac output?
Cardiac output = Heart rate * Stroke volume
What does negative inotropy refer to?
Decreased force of myocardial contraction
What is the bundle of His?
An extension of the specialised tissue of the AVN
What effect does the parasympathetic nervous system have upon the ventricles?
The ventricles are not innervated by the parasympathetic nervous system.
What effect does the parasympathetic nervous system have upon the ventricles?
The ventricles are not innervated by the parasympathetic nervous system.
What type of ion transfer occurs at Stage 3 of ventricular myocyte action potentials?
Closing of calcium channels but potassium channels remain open
Binding of noradrenaline to alpha-1 adrenoceptors on blood vessels leads to?
Smooth muscle contraction (vasoconstriction/venoconstriction)
Where is the sinoatrial node (SAN) usually found?
In the wall of the right atrium
What shape are cardiac myocytes?
Elongated and cylindrical
What is the definition for a normal ST segment?
A flat, isoelectric line between the end of the S wave and the beginning of the T wave
Which part of the gastro-intestinal tract consists of a mixture of both striated and smooth muscle?
Oesophagus
A sudden increase in perfusion pressure triggers autoregulatory [Blank] which decreases the diameter of blood vessels.
Vasoconstriction
If the arterial blood pressure drops too quickly, the stretch on the arterial walls [Blank] and the baroreceptors fire action potentials [Blank] frequently.
Decreases
Less
What does negative chronotropy refer to?
Decrease in heart rate
If the blood pressure increases too quickly, the baroreceptor reflex [Blank] the activity of the sympathetic nervous system (SNS) and [Blank] the activity of the parasympathetic nervous system (PNS).
Decreases
Increases
What does positive dromotropy refer to?
Increased conduction velocity
What does the P wave indicate on an ECG?
Atrial depolarisation
What are the two components of specialised elastic tissue?
Internal and external elastic lamina
Question 151
What is the normal range for cardiac output?
4.0-8.0L/min
Describe the path of blood circulation in the foetal heart, starting from the placenta?
IVC, Right Atrium, Left Atrium, Left Ventricle, Aorta
Which valves are responsible for producing the first heart sound (S1)?
AV valves closing
Which cell type is the tunica intima primarily formed of?
Simple squamous epithelial cells
What is the most abundant cell type of the heart?
Cardiac myocytes
During a sudden increase in blood pressure, deactivation of the sympathetic nervous system and activation of the parasympathetic nervous system leads to which 3 key changes?
Vasodilation of arteries/arterioles
Decreased heart rate
Decreased force of myocardial contraction
What is the mechanism of action of Phentolamine?
It is an antagonist of the Alpha-adrenergic receptor, which noradrenaline acts on to cause vascular constriction (in particular Alpha-1)
In which blood vessels is there the largest fall in blood pressure and velocity?
Arterioles
Which cell type is the tunica media primarily formed of?
Smooth muscle cells
The “funny” current involves a mixture of which two ions?
Sodium ions (Na+) and potassium ions (K+)
Binding of adrenaline/noradrenaline to β2-adrenoceptors leads to [Blank] of blood vessels and [Blank] force of myocardial contraction.
Vasodilation
Increased
In ventricular myocyte action potentials, at which stage is there a simultaneous outflow of potassium ions and inflow of calcium ions?
Stage 2 (Plateau stage)
Respiratory expiration [Blank] venous return while respiratory inspiration [Blank] venous return.
Decreases
Increases
What type of ion transfer occurs at Stage 0 of ventricular myocyte action potentials?
Inflow of sodium ions
What does the QT interval represent?
Total time from ventricular depolarisation to ventricular repolarisation
What is the state of the atrioventricular (AV) valves and semi-lunar valves during the isovolumetric relaxation phase?
AV valves closed, semi-lunar valves closed
What happens during the resting potential phase of the cardiac action potential (phase 4)?
The sodium-potassium pump restores resting membrane potential (-90mV) by pumping 3 Na+ ions out while 2 K+ ions move in, utilising energy from ATP.
What is the equation for mean arterial pressure?
Mean arterial pressure (MAP) = [(diastolic blood pressure * 2) + systolic blood pressure]/3
What is the equation for mean arterial pressure?
Mean arterial pressure (MAP) = [(diastolic blood pressure * 2) + systolic blood pressure]/3
What happens during the early repolarisation phase of the cardiac action potential (phase 1)?
Sodium channels close and potassium channels open, leading to efflux of K+ ions out of the cell. These actions cause a slight decrease in membrane potential.
What are capillary walls formed of?
Endothelial cells - usually only one endothelial cell thick
What happens during the plateau phase of the cardiac action potential (phase 2)?
K+ channels remain open, leading to continued efflux of K+ ions. However, Ca2+ channels also open, leading to influx of Ca2+ ions. The influx of Ca2+ ions counteracts the efflux of K+ ions which causes a plateau in membrane potential.
Intracellular calcium ions bind to which type of receptors on the surface of the sarcoplasmic reticulum to trigger further calcium release in cardiomyocytes?
Ryanodine receptors
At the start of the Valsalva manoeuvre, there is an increase in [Blank] pressure which leads to a slight increase in [Blank] volume.
Intrathoracic
Stroke
Which structures join cardiac myocytes together?
Intercalated discs
What is meant by the ‘vicious cycle’ of heart failure?
Decreased cardiac output leads to excessive sympathetic stimulation which works to increase output but at the expense of overworking the heart and causing more cardiac ischaemia (leading to progressively decreased output)
How is Mean Arterial Pressure (MAP) calculated?
MAP = Cardiac Output x Total Peripheral Resistance OR MAP = Arterial Diastolic Pressure + 1/3 of the Pulse pressure. N.B. Pulse Pressure = Systolic pressure-Diastolic pressure
What effect does Stimulation of alpha-1 adrenoceptors have on vascular smooth muscle?
Contraction of smooth muscle
Name two locations of fenestrated capillaries
Gastrointestinal tract, Bowman’s capsule
The venous return should be roughly equal to the [Blank] in order to prevent pooling of blood in the systemic or pulmonary circulation.
Cardiac output
What type of ion transfer occurs at Stage 1 of ventricular myocyte action potentials?
Outflow of potassium ions
What is the normal range for mean arterial pressure (MAP)?
70-110mmHg
Which intracellular structure acts as a store of calcium ions for cardiac myocytes?
Sarcoplasmic reticulum
Which target organs are acted upon by acetylcholine projected from the ends of postganglionic sympathetic nerve fibres?
Sweat glands
A sudden decrease in perfusion pressure triggers autoregulatory [Blank] which increases the diameter of blood vessels.
Vasodilation
What is the state of the atrioventricular (AV) valves and semi-lunar valves during the inflow phase of the cardiac cycle?
AV valves open, semi-lunar valves closed
Binding of adrenaline/noradrenaline to α1-adrenoceptors leads to [Blank] of blood vessels and [Blank] force of myocardial contraction.
Vasoconstriction
Increased
What are the contractile units found in cardiac myocytes called?
Sarcomeres
What are the 3 main layers of the arterial wall?
Tunica intima
Tunica media
Tunica externa/adventitia
What type of ion transfer occurs at Stage 3 of ventricular myocyte action potentials?
Closing of calcium channels but potassium channels remain open
Which fibres provide sympathetic innervation to the sinoatrial node and atrioventricular node?
Postganglionic fibres from the sympathetic trunk
What is the end-systolic volume (ESV)?
Volume of blood in the ventricles following ventricular systole (simultaneous contraction of both ventricles)
What is the end-systolic volume (ESV)?
Volume of blood in the ventricles following ventricular systole (simultaneous contraction of both ventricles)
Which blood vessels contains the largest proportion of blood in the circulatory system?
Veins
What is the equation for Poiseuille’s law of resistance?
R=8η/πr^4
Where:
R = Resistance to blood flow
η = Viscosity of blood
r = Radius of blood vessel
Which type of muscle does not possess a T-tubule system or well developed sarcoplasmic reticulum?
Smooth muscle
What is calcium-induced calcium release?
Intracellular Ca2+ binds to ryanodine receptors on the surface of the sarcoplasmic reticulum which triggers Ca2+ to be released from the sarcoplasmic reticulum into the intracellular space.
Which areas in the heart can generate spontaneous electrical activity?
Primary site is the SA node. However, the AV node and other tertiary fibres (e.g. Bundle of His, Purkinje fibres) can also generate spontaneous electrical activity if the AV node fails.
