Respiratory Flashcards
What is the central pattern generator?
A network of communicating pathways producing respiratory patterns depending on the animals need.
What input systems act to regulate respiration patterns?
Muscle stretch receptorsIrritant receptorsIntercostal Golgi tendon organsChemoreceptors
Name the peripheral chemoreceptors and the location of the main adult one.
AorticCarotid - at the carotid bifurcation, adjacent to the carotid sinus
Describe the Hering-Breuer reflex
Stretch receptors in the lung react to inflation of the lung, they send OFF signals to the pons of the brain stem which inhibit the dorsal respiratory group. Therefore preventing further inspiration.
What effects does activation of irritant receptors of respiratory epithelium have? Which nervous system is activated?
CoughingMucous productionShallow breathing BronchoconstrictionParasympathetic nervous system
Which respiratory group does the pre-botzinger complex work upon?
Dorsal respiratory group.
The ventral respiratory group works on which phase of respiration?
Expiration
Which cranial nerve controls the carotid body?
Glossopharyngeal
What parameters are monitored by the peripheral chemoreceptors?
PO2 PCO2(H+)
Which parameter doe central chemoreceptors measure?
PCO2
Which nerve is stimulated in activation of the carotid body in response to low PO2?
Carotid sinus nerve
Why is PCO2 the main governor of respiration?
Hb saturation doesn’t differ much until PO2 dips below 70mmHg
What is a respiratory acidosis caused by?
Increased h+ due to increased PaCO2
What is the normal pH of blood?
7.4
Why can’t h+ ions stimulate central chemoreceptors?
They can’t cross the BBB
What is the first line of defense against respiratory acidosis/alkalosis?
Buffers
What is a buffer?
A molecule that can pick up or donate h+ ions
What is a strong acid?
One which fully dissociates in solution
What is the equation of pH?
Negative log of h+ concentration.
How do we distinguish a bronchiole from a bronchii?
Bronchiolar walls have no cartilage
What is meant by monopodial division?
Divisions which make the further tubes smaller
What is the function of a type one alveolacyte?
Gas exchange
What is the function of a type 2 alveolacyte?
Secretion of surfactant
What is the function of the elastic fibres surrounding the alveolar sacs?
Elastic recoil
What artery supplies the lung mesenchyme with oxygen?
Bronchial artery which branches off the aorta
What vessels allows venous drainage of the lung tissue?
Caudal vena cava or the vessels drain directly into the left atrium
Name the types of fetal gas exchange occurring between the foetus and the placenta.
Counter currentConcurrentCross currentPool
How does the foetus adapt to its state of relative hypoxia within the uterus?
Insensitive carotid bodiesHigh cardiac outputHigh affinity of Hb for oxygen
Name a stimulus of the first breath of the neonate after birth.
HypoxiaDecreased body temperatureSensory stimuli from the mother
Which stage of respiratory development development involves the differentiation of type one and two epithelial cells?
Terminal sac phase
In which phase of respiratory development is there the most secretion of surfactant?
Alveolar phase
What does the endoderm of the fetal lung develop into?
Respiratory epithelium and glands
What happens in the pseudoglandular phase of development?
The bronchiole tree extends into the mesenchyme of the lung, vascularisation occurs
In which phase of respiratory development do the respiratory bronchioles form?
Canalicular
Describe the splitting of the principle bronchi.
The right has three splits whereas the left has only two. Also the left deviates more laterally than the right which remains within the midline.
Describe the process of inhalation.
Muscle relaxation, increased space in the lungs, drop in alveolar pressure relative to atmospheric pressure causing air to move into the lungs.
Which muscles contract during inspiration?
Diaphragm contracts and flattens.External intercostals pull the chest cavity cranially and outwards
What is meant by the transpulmonary pressure?
The difference between alveolar and interpleural pressure.
What is the difference between passive and active respiration?
Active utilizes muscle contraction whereas passive utilizes elastic recoil.
What causes surface tension in the alveolus?
Hydrogen bonding between air and water on the alveolar epithelium
What is the function of surfactant? How does it work?
It prevents surface tension by embedding its hydrophilic head into the solute present on the epithelial wall, thereby reducing hydrogen bonding between water and air.
What is the structure of surfactant like?
Phospholipid, protein and calcium, a bit like a cell membrane molecule
How does the volume of surfactant differ between alveolus?
It doesn’t, they all contain the same volume
How does the concentration of surfactant differ between small and large alveoli?
Smaller have a greater concentration
What is the equation for pressure in the alveoli?
P=2T/R
What effect does increased turbulence have on resistance?
Resistance increases
What is laminar flow of air?
All going in the same direction
What is the equation for airway resistance?
R = 8 x length x viscosity / pi x radius^4
Why does resistance decrease at the distal airway?
Decreased tube radius
How do you work out minute volume?
Tidal volume x respiratory rate
What is the tidal volume?
Volume of air in/exhaled in a single breath
Why is there a residual volume to the lungs?
Limits to compression
What is dynamic equilibrium?
When molecules in the gas phase equal that of the solute phase
What is meant by partial pressure?
The concentration of a gas in a gas mixture
Why does the pressure of air alter from the nares to the bronchi?
Humidify action of air in the nasal cavity
How do you work out the partial pressure of oxygen in the lung?
Atmospheric pressure minus partial pressure of water which humidifies the air
What is dead space air?
Air which is being ventilated but not involved in gas exchange
Which type of dead space occurs with a decrease in perfusion?
Functional dead space
What does an vascular block cause?
A decrease in perfusion despite adequate ventilation
What type of block causes a high ventilation:perfusion ratio?
Vascular block
What effect does a bronchiolar block have on the ventilation:perfusion block?
Decrease
How much oxygen can one liter of blood carry? (Maximum)
200mL
What is the concentration of Hb per liter of blood?
150 g/L
What type of iron is found in the harm group of Hb?
Ferrous iron - Fe2+
What type of binding does Hb have with oxygen?
Cooperative binding - the binding of one molecule makes it easier for further molecules to bind
How does the sigmoidal oxy-hemoglobin curve change beyond 70mmhg
It plateaus - there isn’t much increase beyond this
What effect does increased temperature have on oxygen offloading?
Increased
How does the increase in temp causing increased oxygen offloading apply to physiological situations?
Skeletal muscle increases in temperature during exercise
What change in pH causes increased offloading of oxygen? Which substances cause the decrease in the body?
Decreased pH - acidityLactic acid and 2,3-diphosphoglycerate
Which enzyme is key in the transportation of CO2 in the blood?
Carbonic anhydrase
Which substance is CO2 mainly transported in in the blood?
Bicarbonate ions HCO3-
O2 is uploaded to Hb with _____ CO2 and ____ pH
LowHigh
What do extra alveolar vessels do?
Move blood to and from the lungs
What do alveolar vessels do?
Gas exchange
Why do extra alveolar blood vessels dilate with inhalation?
Blood vessels are connected to the visceral pleura
Which vessels of the lungs provide most resistance?
Capillaries
What is the overall effect of sympathetic stimulation on pulmonary vessels?
Vasoconstriction
Beta sympathetic receptors cause _____ of the pulmonary vessels in comparison to alpha receptors.
Vasoconstriction
What effect does alveolar hypoxia have on lung vessels? Why does this occur?
Vasoconstriction Maintenance of the ventilation:perfusion ratio
Why is generalized hypoxia bad in terms of the va:p?
Generalized vasoconstriction = deceased perfusion Increased pulmonary vascular resistance
Which has more vascular smooth muscle a cow or a dog?
Cow
What effect does nitric oxide have on pulmonary arterioles?
Vasodilation
What causes the release of NO from endothelial cells?
Bradykinin, increased blood flow speed, PNS stimulation
Which adrenoceptors are the most effective target to cause bronchoconstriction?
Beta 2 sympathetic receptors
Name the three physiological methods of altering bronchiolar diameter.
Autonomic nervous systemNANC neuronsIrritant receptors
Why is oral uptake of terbutaline and albuterol limited in the body?
They have high pKa values
What is the effect of increasing dosage of terbutaline on its pharmacological effects?
The selectivity of terbutaline decreases at higher dosages
How long after administration can ventipulmin still be found being excreted in the urine?
12 days
What contraindications are found with beta2 agonists of the ANS?
BP abnormalitiesTachycardia HypokalaemiaSeizures
Where in the body is albuterol metabolized?
Liver
How is terbutaline excreted?
By the kidneys, relatively unchanged
How can an antagonist of the PNS work?
Anticholinergics - blocks ACh
Name two methods of action which result in PNS agonism.
Anticholinesterase inhibitorsCholinergics
What effect does bethanechol have on smooth muscle?
Increases contraction – bronchoconstriction
What is the significance of Pilocaprine action?
By causing miosis of the pupil it increases drainage angle of the eye and therefore is used to treat glaucoma.
What clinical conditions are Anticholinesterase inhibitors used for?
Myasthesia gravis - neostigmineParasite infection - organophosphates
Outline the method of action of methylxanthines.
They increased cAMP in cells thereby interfering with myosin light chain kinase molecules (increased activation of MLCphosphorylase and causing relaxation of smooth muscle.
Name a methylxanthine.
Theophylline
What class of drugs are considered direct antitussives?
Opioids
Name two types of opioid receptors found in the body.
Kappa and mu
What other effects can methylxanthines have in the body?
- Relaxing bronchial smooth muscle
- Positive inotropy
- Positive chronotropy
- Increase BP
- Increased renal blood flow - mild diuresis
- Anti-inflammatory effects
- Respiratory - Increased PCO2
Which opioid has higher potency codeine or butorphanol?
Butorphanol has ten times the potency of codeine
What effects to opioids have on the respiratory system?
Reduce response to respiratory irritantsRespiratory / CV depressionSedation
What types of cough are targeted by anti-tussive therapy?
Exhaustive or non-productive coughs
What are exogenous surfactants used to treat?
Neonatal respiratory distress
What effect does doxapram have upon the body?
Chemoreceptor activity increased
Increased respiratory rate and tidal volume
Increased adrenaline release
Outline the two main actions of mucolytic drugs and the names of the substances which cause these.
N-acetylcysteine - breaks disulfide bonds between mucous moleculesBromhexine HCl - hydrolysis of mucopolysaccarides
Which type of mucolytic drug is ineffective in the presence of protein? Describe a situation in which this may occur.
Bromhexine HClProtein is presence during infection or inflammatory processes
How do mucolytics work?
They decrease the viscosity of respiratory mucosa secretions.
Outline the process of action of expectorants.
They are gastric irritants which cause increased vagal tone and therefore increase respiratory secretions and therefore substance expulsion.
How do decongestants work?
The reduce the thickness of gastric mucosa by causing vasoconstriction of nasal vessels and reducing ECF between nasal cells
Outline the three procedures of carbon dioxide in the blood.
What is the difference between anatomical and functional dead space?
Anatomical is air which is found in regions of the respiratory tract which do not take part in gas exchange whereas functional dead space gas is that found in exchange areas under low perfusion
What is the partial pressure of oxygen in atmospheric air?
160mmHg
21% of atmospheric pressure (760mmHg)
What is the normal minute volume of a dog at rest?
10mL/kg
What is the normal PO2 within the dogs lungs? How is that calculated?
149mHg
Due to humidification of air down the respiratory tract the PH2O must be subtracted from the original value.
PAO2 = (760-50) x 0.21 = 149mmHg
Describe the route of the vagus nerve through the thorax
It enters the thorax within then vagosympathetic trunk, entering the middle cervical ganglion, on leaving it runs through the thorax dorsal to the phrenic nerve and ventral to the sympathetic trunk, giving off the recurrent laryngeal and cardiac nerves. In the caudal thorax it bifurcated to dorsal and ventral trunks before leaving through the diaphragm to supply the abdominal viscera.
What is the route and function of the phrenic nerve in the thorax?
The phrenic nerve supplies the diaphragm. It arises from C5 and C7 (+ some vertebral connections) and runs through the ventral thorax
Describe the anatomy of the ansa subclavia within the thorax.
The ansa subclavia are small branches which connect the middle cervical and cervicothoracic ganglion of the thorax around the subclavian artery. It allows the separation of the vagus and sympathetic trunk nerves.
Outline the function of the vagus nerve within the thorax.
Caudal to the middle cervical ganglion of the thorax the vagus nerve gives off small branches which provide parasympathetic innervation to the heart and lungs
