Physiology bits Flashcards
Which kind of alveolar cell secretes surfactant?
Type 2 alveolar cell
What physiological parameter is most closely related to afterload?
.
a) Mean arterial pressure (MAP)
b) arterial elastance
c) central venous pressure
d) end-diastolic volume
e) end-systolic volume
Mean arterial pressure (MAP)
Does prescribing beta blockers to patients with ischaemic heart disease increase or decrease coronary perfusion time?
Beta-blockers reduce heart rate –> increasing coronary perfusion time
Does an elevated expiratory reserve volume describe an obstructive or restrictive spirometry pattern?
Obstructive
To increase respiratory rate, chemoreceptors in the medulla respond to what stimuli?
increased CO2 in the cerebral spinal fluid (CSF)
Which nerve is involved in blood pressure information being transferred from baroreceptors to the nervous system?
via the 9th cranial nerve (glossopharyngeal nerve)
What stimulates central chemoreceptors?
H+ ions
In response to muscarinic blockade, what do the bronchi do?
Bronchodilation –> muscarinic receptors receive parasympathetic innervation, which leads to bronchoconstriction –> therefore blockade of these receptors results in bronchodilation
Mean arterial pressure (MAP) equations (two equations)
MAP (mean arterial pressure) = CO (cardiac output) x TPR (total peripheral resistance)
- MAP = arterial diastolic pressure + 1/3 pulse pressure
Where does the fastest conduction of an impulse occur in the cardiac conducting system?
Purkinje fibres –> specialised conduction fibres
In chronic hypercapnia, the central chemoreceptors become less sensitive to CSF pH changes caused by the high levels of CO2 –> what is responsible for respiratory drive in chronic hypercapnia?
Arterial oxygen levels –> chemoreceptors become reliant on the hypoxic drive instead
Central chemoreceptors are involved in regulating breathing.
Where are the central chemoreceptors located?
Ventral medulla
Where are capillaries with open pores in the endothelium found?
Hepatocytes
The Frank-Starling curve of the heart shows one variable being proportional to another variable under normal physiological circumstances.
What are the two variables that are linked via this curve?
Stroke volume and preload
At which point of the cardiac cycle does the highest volume of blood flow through the coronary arteries?
Ventricular diastole
Alveolar ventilation equation linking tidal volume and physiological dead space
High altitude –> what ABG is likely (pt is short of breath and lightheaded)
Respiratory alkalosis
What is expiratory reserve volume (ERV)?
ERV is the additional volume of air that can be forcefully exhaled below tidal volume
On the Frank-Starling curve, which variables are usually placed on the X-axis and Y-axis?
Describe the baroreflex mechanism of the cardiovascular system and how it detects and stops a drop in blood pressure
- A decrease in MAP reduces the stretch on the baroreceptors
- As a result, baroreceptors send less signals to the glossopharyngeal and vagus nerve to the medulla
- The sympathetic NS is therefore activated to increase the blood pressure
In emphysema, is lung compliance increased or decreased?
Increased –> due to loss of elastic tissue so less recoil and therefore lungs expand too much (hyperinflation) –> results in barrel (hyperexpanded) chest
Valsalva manoeuvre
The patient is asked to breathe out forcefully while closing their mouth and pinching their nose shut
Vital capacity is what?
- the maximal volume of gas that can be expelled from the lungs after a maximal inhalation or a full breath
. - Tidal volume + Inspiratory reserve volume + Expiratory reserve volume
Infective exacerbation of COPD –> what acid-base balance disorder is most likely? (shallow breaths)
Respiratory acidosis
What is inspiratory reserve volume?
The volume of air that can be inhaled after a quiet inhalation
Does pulmonary fibrosis increase or decrease lung compliance?
Decreases lung compliance –> tissue is all fibrosed so doesn’t expand much
What is the main function of autoregulation?
Maintaining constant blood flow in organs such as the kidney and brain
(autoregulation is the process of maintaining constant arterial pressure)
Which ion channels are open during the plateau phase of the cardiac action potential?
Calcium channels and potassium channels
What is the main determinant of diastolic blood pressure?
Total peripheral resistance
- An increase in vascular resistance, such as scarring or hardening of the blood vessels, will cause an increase in diastolic blood pressure
Anatomical dead space + alveolar dead space = ?
Physiological dead space
Which feature of cardiac myocytes allows for the transmission of ions between adjacent cells?
- Cardiac myocytes contain intercalated discs which join myocytes together and enable transmission of ions between adjacent myocytes
–> This movement of ions allows synchronised contraction of the myocardium
Which ions are responsible for the generation of the “funny” current?
- Sodium ions and potassium ions
–> The funny current is a mixed sodium and potassium current which is activated by hyperpolarisation (rather than depolarisation)
–> One of the reasons why it is termed a “funny” current is due to a mixture of sodium and potassium ions being involved, rather than just one type of ion
Which of the following options describes the events which occur during the rapid repolarisation phase of the cardiac action potential?
Rapid efflux of potassium ions causes a sharp decrease in membrane potential
What type of hypoxia can be caused by cyanide poisoning?
- Histotoxic hypoxia occurs when the body’s cells are unable to utilize oxygen, even though there may be adequate oxygen levels in the blood
Which region of the heart does the pulmonary vein drain into?
Left atrium
Pulmonary oedema –> which chamber of the heart is affected?
Left ventricle
Peripheral oedema –> which chamber of the heart is affected?
Right ventricle
Which of the following is responsible for opening ryanodine receptors during contraction in cardiac myocytes, causing a release of calcium ions from sarcoplasmic reticulum stores?
Ca 2+ ion influx
Which of the following options describes the state of the sodium (Na+), potassium (K+) and calcium (Ca2+) channels during the depolarisation phase of the cardiac action potential?
Voltage-gated Na+ channels open, L-type Ca2+ channels open, voltage-gated K+ channels closed
What kind of molecule is surfactant?
Phospholipid
Which of the following options shows the correct equation relating blood flow, pressure and resistance in a blood vessel?
Flow = Change in pressure/Resistance
Which of the following statements best describes the pathophysiology of a reduced forced vital capacity (FVC) in a patient with kyphoscoliosis?
The abnormal curvature of the spine reduces chest wall compliance during inspiration
Which of the following is taken up by macrophages to develop foam cells?
- LDL
–> LDL is oxidised as part of the atherosclerotic pathway, and is then phagocytosed by macrophages in the vessel wall
–> These macrophages become known as foam cells
In which blood vessel is there the largest fall in blood pressure and velocity?
Arterioles
In terms of local control of blood flow, what substance is the most potent vasoconstrictor?
- Endothelin
–> Its production is stimulated by angiotensin II and vasopressin, among other mediators
Does obesity cause increased or decreased lung compliance?
Decreased
–> Obesity causes mechanical compression of the diaphragm, lungs and chest cavity
