110 Questions
What is the primary trigger for the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling?
Stimulation of ryanodine receptors by Ca2+
In excitation-contraction coupling, what event allows actin-myosin binding leading to muscle contraction?
Binding of Ca2+ to troponin C
Which mechanism is responsible for pumping back released Ca2+ into the sarcoplasmic reticulum during muscle relaxation?
Ca2+ ATPase
According to Frank Starling’s Law, what happens to stroke volume as end-diastolic volume (EDV) increases?
Stroke volume increases up to a certain limit
What effect does heart failure have on the relationship between end-diastolic volume (EDV) and stroke volume (SV)?
Shifts the relationship to the right
Which of the following statements best explains why the V/Q ratio at the top of the lung is infinity?
Blood flow is least but ventilation is most.
In the context of the text, what factor determines the stroke volume (SV)?
End-diastolic volume (EDV)
According to Frank Starling's Law, what happens to stroke volume as end-diastolic volume (EDV) increases?
SV increases up to a certain limit.
Which condition shifts the curve in heart failure according to the text?
Pulmonary capillary congestion
What causes Ventilation Perfusion Matching at the bottom of the lung according to the text?
Accumulation of CO2 in blood causes pulmonary constriction.
What is the volume of air that remains in the lungs even after a maximal expiration?
1000 ml
Which lung volume measurement represents the maximum volume of air that can be inspired at the end of a normal quiet expiration?
Inspiratory capacity (IC)
Which lung volume measurement represents the total volume of air that the lungs can hold?
Total lung capacity (TLC)
What effect does stimulation of sympathetic nerves have on the heart muscle?
Increases the force of contraction
What is the purpose of bronchodilators like B2 agonists and anticholinergics in managing shortness of breath?
Relieve airway constriction
In spirometry, what does FEV1/FVC ratio greater than 75% indicate?
Normal or increased in restrictive disease
What is the impact of vagal stimulation on the heart?
Primarily affects heart rate rather than contractility
Which arrhythmia involves chaotic and disorganized atrial activity resulting in an irregular heartbeat?
Atrial Fibrillation
What does the absence of a P wave and presence of an abnormal F wave on an ECG indicate?
Atrial Fibrillation
When ventricular rates are found to be less than 60 bpm, what condition should be considered due to potential AV conduction disease?
Sinus Bradycardia
What is the main function of desmosomes within intercalated discs?
Allowing transmission of tension between adjacent cardiac cells
What is the contractile unit of muscles known as?
Myofibrils
What triggers muscle tension production in sarcomeres?
Sliding of myosin filaments on actin filaments
During which phase of the cardiac action potential does the cell become positive?
Phase 0 - Depolarization
What happens during the absolute refractory period in cardiac myocytes?
Generation of action potential is impossible
In atrial fibrillation, which management approach focuses on restoring sinus rhythm with pharmacologic conversion or electrical cardioversion?
Rhythm control
Which condition associated with atrial fibrillation requires long-term oral anticoagulation for stroke prevention?
Valvular disease
Among the listed antiarrhythmic drugs, which one primarily works by reducing the Na+ channel current?
Flecainide
What is the primary approach in atrial flutter management when the focus is on accepting AF but controlling the ventricular rate?
Digoxin administration
Which of the following conditions contributes to an increased risk of thromboembolic stroke in atrial fibrillation based on the CHA2DS2VASc score?
Hypertension
What is the primary function of the ventilatory pump in maintaining normal respiration?
Assisting in breathing
Which receptors are responsible for guarding against hyperinflation during respiration?
Stretch receptors on bronchi walls
What stimulates Juxtapulmonary J receptors to cause rapid, shallow breathing?
Capillary congestion
Which brain center is primarily responsible for generating the respiratory rhythm?
Medulla
In spirometry, which lung volume represents the maximum amount of air that can be forcefully exhaled after a maximum inhalation?
Vital capacity
What is the term for the increased ventilatory rate caused by decreased blood pressure?
Hyperpnea
How do the accessory muscles of inspiration differ from major inspiratory muscles like the diaphragm?
They contract mainly during forceful inspiration.
What condition may lead to an increased importance of juxtapulmonary J receptors?
Pulmonary embolism
How do baroreceptors influence respiration rate?
Increase ventilatory rate with decreased BP.
What is the primary neurotransmitter released from sympathetic nerves to the ventricular muscle?
Noradrenaline
What effect does vagal stimulation have on the heart?
Decreases heart rate
What is the term that describes the extra volume of air that can be maximally inspired over and above the typical resting tidal volume?
Inspiratory reserve volume (IRV)
Which condition may require a pacemaker due to a coinciding period of fast ventricular rate?
Atrial fibrillation
Which lung volume measurement represents the volume of air in the lungs at the end of normal passive expiration?
Residual volume (RV)
What abnormality can be observed on an ECG in atrial fibrillation?
Absence of P wave
What condition usually benefits from diuretics in terms of managing shortness of breath?
Pulmonary oedema
What is the effect of too fast heart rate on systole and diastole?
Shortens both systole and diastole
What term refers to the maximum volume of air that can be moved out during a single breath following a maximal inspiration?
Vital capacity (VC)
Which lung volume measurement represents the maximum volume of air that the lungs can hold?
Total lung capacity (TLC)
What is the formula for pulmonary ventilation?
Tidal Volume x Respiratory Rate
How does accumulation of CO2 in blood affect the lungs?
Leads to pulmonary constriction
What determines the Stroke Volume (SV) in the heart?
End-Diastolic Volume (EDV)
How does Frank Starling's Law relate EDV and SV in the heart?
Greater EDV leads to greater SV up to a certain limit
How does cardiac output affect respiration?
Affects oxygen and carbon dioxide exchange in the lungs
What stimulates the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling?
Stimulation of ryanodine receptors by Ca2+ from the extracellular fluid
What contributes to an increased risk of thromboembolic stroke in atrial fibrillation according to the CHA2DS2VASc score?
Co-morbidities like hypertension and heart failure
What is the effect of vagal stimulation on the heart muscle?
Decreased force of contraction
How does heart failure affect the relationship between end-diastolic volume (EDV) and stroke volume (SV)?
Reduces SV at all levels of EDV
What triggers muscle tension production in sarcomeres?
Binding of Ca2+ to troponin C
Which type of atrial fibrillation lasts greater than 48 hours but can still be converted to normal sinus rhythm?
Persistent
In atrial fibrillation, what effect does decreased filling times have on cardiac output?
Reduced CO
Which pharmacologic agent is primarily used for rhythm control in managing atrial fibrillation?
Amiodarone
Which class of antiarrhythmic drugs prolongs the action potential and can be used in atrial fibrillation management?
Class 3: Action potential prolongation
In atrial flutter, where is the macro reentrant circuit typically confined?
Right atrium
What is the primary purpose of desmosomes within intercalated discs in cardiac cells?
Provide mechanical adhesion between adjacent cardiac cells
During muscle contraction, what is the main factor responsible for producing muscle tension?
Sliding of actin filaments on myosin filaments
What ions are involved in the depolarization phase (Phase 0) of cardiac myocytes?
Na+ influx and Na+ efflux
What event marks the beginning of early repolarization (Phase 1) in cardiac myocytes?
Opening of K+ channels for efflux
What effect does an increase in intracellular Na+ levels have on the excitability of cardiac myocytes?
Decreases the ability to generate action potentials
What is the primary role of the ventilatory pump in maintaining normal respiration?
Contraction of respiratory muscles to facilitate breathing
Which receptors are responsible for causing rapid, shallow breathing when stimulated by capillary congestion or pulmonary emboli?
Juxtapulmonary J receptors
What is the major muscle responsible for active inspiration during normal respiration?
Diaphragm
Which of the following influences the respiratory rhythm but does not generate it directly?
Higher brain centres
Which condition may lead to increased significance of juxtapulmonary J receptors in respiration?
Pulmonary edema
What happens when baroreceptors detect decreased blood pressure concerning respiratory rate?
They stimulate rapid breathing
Which muscles serve as accessory muscles of inspiration, particularly during forceful breathing?
Sternocleidomastoid, scalene, pectoral muscles
What is the primary effect of stimulating sympathetic nerves on the heart?
Positive inotropic effect
In atrial fibrillation, what ECG abnormality is typically observed?
Irregularly irregular rhythm
What is the primary impact of vagal stimulation on the heart?
Rate regulation
How does excessive heart rate affect systole and diastole?
Shortens both systole and diastole
Which neurotransmitter is primarily released from sympathetic nerves to the ventricular muscle?
Noradrenaline
What is the primary function of desmosomes within intercalated discs in cardiac cells?
Provide mechanical adhesion between adjacent cardiac cells
What initiates the process of muscle tension production in sarcomeres?
ATP interaction with actin and myosin filaments
During which phase of the cardiac action potential does the cell become positive?
Phase 0 (Depolarization)
What is the primary trigger for the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling?
Long acting type Ca2+ channel opening
What plays a crucial role in preventing heart spasm through refractory periods?
Intracellular Na+ levels
What is the main difference between paroxysmal and persistent atrial fibrillation?
Duration of episodes
Which factor is NOT associated with an increased risk of thromboembolic stroke in atrial fibrillation?
Pulmonary embolism
What is the primary purpose of rate control management in atrial fibrillation?
Control ventricular rate
Which antiarrhythmic drug class primarily works by reducing the Na+ channel current?
Class 1
What differentiates atrial flutter from atrial fibrillation?
Location of reentrant circuit
What is the term for the volume of air in the lungs at the end of normal passive expiration?
Functional residual capacity
Which lung volume measurement represents the maximum air that can be inspired at the end of a normal quiet expiration?
Inspiratory capacity
What does Forced Expiratory Volume in one second (FEV1) measure?
Volume of air that can be expired during the first second of expiration
Which lung volume is calculated by adding Inspiratory reserve volume, Tidal volume, and Expiratory reserve volume?
Vital capacity
What is the maximum volume of air that can be moved out during a single breath following a maximal inspiration?
Vital capacity
What stimulates the release of Ca2+ from the sarcoplasmic reticulum during excitation-contraction coupling?
Activation of ryanodine receptors
What is the primary neurotransmitter released from parasympathetic nerves to the ventricular muscle?
Acetylcholine
Which ion is primarily involved in the depolarization phase (Phase 0) of cardiac myocytes?
Ca2+
How does heart failure affect the relationship between end-diastolic volume (EDV) and stroke volume (SV)?
It increases EDV and decreases SV
What is responsible for pumping back released Ca2+ into the sarcoplasmic reticulum during muscle relaxation?
Ca2+ ATPase pump
What happens at the top of the lung in terms of ventilation and blood flow?
Ventilation exceeds blood flow
How does accumulation of oxygen affect pulmonary vasculature?
Results in pulmonary vasodilation
What effect does accumulation of CO2 in blood have on the lungs?
Results in pulmonary constriction
How does stroke volume change with increased end-diastolic volume (EDV) according to Frank Starling's Law?
Increase up to a certain limit
What effect does heart failure have on the relationship between end-diastolic volume (EDV) and stroke volume (SV)?
Shifts the curve to the right
What is the primary factor responsible for dynamic airway compression during expiration?
Contraction of abdominal muscles
Which muscle group primarily lifts the ribs and sternum outwards during inspiration?
External intercostal muscles
Intrapleural pressure plays a crucial role in lung expansion. What effect does a loss of transmural pressure gradient have on the lungs?
Decreases lung compliance
What is a common consequence of decreased chest wall compliance such as in individuals with kyphoscoliosis?
Impaired gas exchange in the lungs
Study Notes
Respiratory System
- Average tidal volume is 500 ml
- Inspiratory reserve volume (IRV) is 3000 ml
- Inspiratory capacity (IC) is 3500 ml
- Expiratory reserve volume (ERV) is 1000 ml
- Residual volume (RV) is 1200 ml
- Functional residual capacity (FRC) is 2200 ml
- Vital capacity (VC) is 4500 ml
- Total lung capacity (TLC) is 5700 ml
- Forced expiratory volume in one second (FEV1) is the volume of air that can be expired during the first second of expiration
Management of Shortness of Breath
- Correctly position patient
- O2 therapy
- Bronchodilators (B2 agonists and anticholinergics) for those with obstructive lung disease like asthma/COPD
- Patients with pulmonary oedema usually benefit from diuretics
- Treat the underlying cause of SOB
- Lifestyle modifications/palliative care
Cardiac System
- Cardiac muscle is striated due to regular arrangement of contractile proteins
- Cardiac myocytes are electrically coupled by gap junctions
- Heart failure is a syndrome that can result from structural or functional cardiac disorders that impair the pumping ability of the heart
- Left heart failure (LHF) is caused by pulmonary capillary congestion/pulmonary oedema
Force Generation by the Heart
- Cardiac myocytes have excitability
- Conduction in cardiac myocytes involves:
- Phase 0: depolarization
- Phase 1: early repolarization
- Phase 2: plateau phase
- Phase 3: repolarization
- Phase 4: resting phase
Cardiac Arrhythmias
- Atrial fibrillation: chaotic and disorganized atrial activity resulting in an irregular heartbeat
- ECG: P wave absent, abnormal F wave present, irregularly irregular rhythm
- May be symptomatic (palpitations, chest pain, dyspnoea, sweaty, fatigue, syncope) or asymptomatic
- Ventricular rates <60 bpm suggest AV conduction disease thus caution with anti-arrhythmic drugs and rate controlling drugs + may require permanent pacing!
Cardiovascular Control
- Intrinsic control:
- Stroke volume changed depending on diastolic length of myocardial fibres
- Frank Starling's Law states that the more the EDV, the higher the amount of blood ejected will be, hence the greater the SV will get (but only up to a certain limit!)
- Extrinsic control:
- Nerves and hormones
- Ventricular muscle is supplied by sympathetic nerve fibres, thus neurotransmitter is Noradrenaline
- Stimulation of sympathetic nerves increases the force of contraction = +ve inotropic effect
- Stimulation of sympathetic nerves to the heart also causes a positive chronotropic effect (HR)
Ventilation
- Pulmonary ventilation = Tidal Volume x Respiratory Rate = 6L/min
- Alveolar ventilation = Tidal volume - anatomical dead space x Respiratory rate 4.2L/min
- Ventilation Perfusion Ratio:
- At the top of the lung, blood flow is least but ventilation is most, hence VQ ratio is = infinity
- At the bottom, blood flow is most but ventilation is least, hence VQ ratio is almost 0### Shortness of Breath
- Anaemia is not usually a cause for shortness of breath because temporary increase in cardiac output acts as a compensatory mechanism, thus arterial PO2 sensed by chemoreceptors is normal.
Lung Volumes
- Tidal volume (TV): 500 ml (volume of air entering or leaving lungs during a single breath)
- Inspiratory reserve volume (IRV): 3000 ml (extra volume of air that can be maximally inspired over and above the typical resting tidal volume)
- Inspiratory capacity (IC): 3500 ml (maximum volume of air that can be inspired at the end of a normal quiet expiration)
- Expiratory reserve volume (ERV): 1000 ml (extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume)
- Residual volume (RV): 1200 ml (minimum volume of air remaining in the lungs even after a maximal expiration)
- Functional residual capacity (FRC): 2200 ml (volume of air in lungs at end of normal passive expiration)
- Vital capacity (VC): 4500 ml (maximum volume of air that can be moved out during a single breath following a maximal inspiration)
- Total lung capacity (TLC): 5700 ml (maximum volume of air that the lungs can hold)
- Forced expiratory volume in one second (FEV1): dynamic volume (volume of air that can be expired during the first second of expiration in an FVC determination)
- FEV1%: FEV1/FVC ratio (normal >75%)
Management of Shortness of Breath
- Correctly position patient
- O2 therapy
- Bronchodilators (B2 agonists and anticholinergics) for those with obstructive lung disease like asthma / COPD
- Patients with pulmonary oedema usually benefit from diuretics
- Treat the underlying cause of SOB
- Lifestyle modifications / palliative care
Force Generation by the Heart
- Cardiac muscle is striated due to regular arrangement of contractile proteins
- Cardiac myocytes are electrically coupled by gap junctions
- Action potential duration: 150ms
- Excitation Contraction Coupling: opening of long acting type Ca2+ channels in Phase 2 of the action potential allows the influx of Ca2+ from ECF
- Release of Ca2+ from sarcoplasmic reticulum, then diffusion of Ca2+ to myofilaments
- Binding of Ca2+ to troponin C exposes cross-bridge binding site, allowing actin-myosin binding and triggering sliding, thus contraction
Cardiac Output and Stroke Volume
- CO = SV * HR
- SV = EDV - ESV
- Stroke volume changed depending on diastolic length of myocardial fibres
- EDV determined by venous return to heart
- Frank Starling’s Law: the more the EDV, the higher the amount of blood ejected will be, hence the greater the SV will get (but only up to a certain limit!)
Cardiac Arrhythmias
- Atrial Fibrillation: most common arrhythmia, may be symptomatic (palpitations, chest pain, dyspnoea, sweaty, fatigue, syncope) or asymptomatic
- Chaotic and disorganised atrial activity resulting in an irregular heartbeat
- ECG: P wave absent, abnormal F wave present, irregularly irregular rhythm
Learn about the process of excitation-contraction coupling in muscle contraction, involving the opening of long-acting Ca2+ channels, stimulation of ryanodine receptors, release of Ca2+ from the sarcoplasmic reticulum, and binding to troponin C to enable actin-myosin interactions.
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