23. Regulation of Respiration Flashcards
What are gills?
Invaginated extension of the body surface
What is the operculum?
Specialised cover that protects the gills
How is water and blood moved over the gills?
- Pumping mechanisms moves water over gills
- Internal circulatory system distributes blood throughout the gill and body
- Unidirectional pumping mechanism
What are the lamellae?
- Thin slices of tissue in the gills which increase surface area for gas exchange
How do lamella impact the diffusion distance?
They reduce the diffusion path (length between water and blood)
What vessels are found in the gills?
- Deoxygenated (afferent) blood enters (low O2)
- Oxygenated (efferent) blood leaves (high O2)
How is the unidirectional flow of water through the gills in fish achieved by?
- Sequential opening and closing of the mouth and operculum
- A small pressure differential between buccal and operculum cavities
Which type of flow is found in fish?
Countercurrent flow increases gas exchange
- Blood meets fresh oxygenated water
How does the mudskipper breath in air?
Reinforced gills that do not collapse in air, allowing limited gas exchange out of water
How does the armoured catfish breathe in air?
- Highly modified and vascularised intestine used for gas exchange out of water.
- Air is swallowed and later expelled from the anus
What are the lungs?
Invaginated internalised extension of body surface
What are the lungs protected by?
Ribs and thorax
What is the trachea?
Conducts air into the body
- protected
What are the bronchi?
Major air passageways of the lung
How are the bronchi further structured?
- Branch into bronchioles
- At the end of the bronchioles are the alveoli
What is the pathway of air conduction?
Trachea-Bronchi-Bronchioles
What are the trachea and bronchi composed of?
Cartilage
What are the bronchi and bronchioles composed of?
Layer of smooth muscle
What happens to the bronchioles in exercise?
They dilate
What happens to the bronchioles in asthma?
(Smooth muscle around) Bronchioles constrict - bronchiospasm
What causes constriction of bronchioles?
They are innervated - sympathetic nerves connected to release noradrenaline to constrict
What are the alveoli?
Hollow pockets of air with capillaries running through the surface
How is distance between gases in the alveoli and gases in the blood minimised for gas exchange?
Epithelial cell of the alveoli and endothelial cell of the capillary are fused, no connective tissue or fluid between them
What are 2 examples of respiratory tract secretions?
- Epithelial cells lining the airways produce sticky mucus the captures inhaled dirt and microbes
- Cell lining the airways have cilia
What does the cilia do?
Its beating continually sweeps the mucus, with its trapped debris up towards the pharynx
How does smoking affect breathing?
Smoking immobilises the cilia of the airways for hours
What is smoker’s cough?
Malfunctioning mucus escalator means you can’t clear obstructing mucus from airways
How does cystic fibrosis influence abnormal respiratory secretions?
- Unusually thick and dry respiratory mucus
- Obstructs the airway and also obstructs cilia function
What is the cause of cystic fibrosis?
- Single gene mutation results in non functional chloride channel protein
- Chloride ions cannot leave the cell
- A very thick mucus forms, which become clogged with debris and bacteria
What is the difference between a normal respiratory tract and a cystic fibrosis one?
- In the normal respiratory tract there is an ion channel
- It opens when there is thick mucus and water is dragged out via osmosis
- In the absence of this channel there is nothing to thin the mucus
What is a surfactant?
A substance which reduces the surface tension of a liquid
What is the surfactant of the lungs?
Phospholipoprotein
What is the lung surfactant secreted by?
Some alveolar cells
What does the lung surfactant do?
Results in less force required to inflate the lungs
- Without surfactant, lungs are delicate wet tissue which may collapse
How are the heads/tails of lung surfactant oriented?
Hydrophilic head and hydrophobic tail
- Tails facing the air space
What is respiratory distress syndrome?
- Surfactant is produced at 20 weeks in the mother’s womb
- RDS lacks surfactant
How does the diaphragm and surrounding respiratory tract behave during inhalation?
- Diaphragm contracts and pulls down on the thoracic cavity, pleural membranes, lungs
- Air enters through the trachea
- Lungs expand
What pressure is created in inhalation?
Negative pressure
What happens to the diaphragm and surrounding respiratory tract in exhalation?
- Diaphragm relaxes, elastic lung tissues pull the diaphragm back up and push air out of the airways
What is the pressure like in exhalation?
Positive pressure
What do the pleural membranes do?
They line the pleural cavity and cover each lung
What are the intercostal muscles?
Muscles between the ribs
How do the intercostal muscles aid inhalation?
Contraction of external intercostals push out ribs and increase thoracic volume
How do the intercostal muscles aid exhalation?
Exhalation is aided by the contraction of the internal intercostals which pull in the ribs and decrease thoracic volume
Is breathing involuntary or voluntary?
Normally involuntary but can be voluntary
Where are the sensory inputs of breathing sent?
To the central nervous system
What does the respiratory centre in the brainstem determine?
Medulla and pons
- Determines depth, amplitude and frequency of breathing
What does the phrenic nerve control?
Contraction and lowering of diaphragm
What do the efferent nerves control?
Efferent nerves (spinal motor neurons) activate intercostal muscles
What regulates increases in partial pressure of CO2?
Chemoreceptors on the ventral surface of the medulla are sensitive to increases in PCO2 (via change in pH)
What regulates a decrease in the pO2?
Chemoreceptors in the aortic and carotid bodies are sensitive to increases in CO2 and large decreases in pO2
Is the breathing rate more sensitive to CO2 or O2?
The breathing rate is more sensitive to increased CO2 than to decreased O2
How does an animal react to hypoxia?
- when o2 is reduced at high altitudes, an animal hyperventilates, due to activation of chemoreceptors in aortic and carotid bodies to maintain sufficient O2 delivery
What happens in aquatic hypoxia?
Causes an increase in gill ventilation in fish due to stimulation of chemoreceptors in the gills
How do animals try to survive periods of reduced O2 availability?
- Reduce energy expenditure
- Use anaerobic metabolic pathways
- Increased BPG
What are some measures for overcoming the problems of high altitude in the long term?
- Reset threshold of chemoreceptors for O2 so that they are more sensitive to pO2
- Increase number of RBC and blood Hb content (increase O2 capacity of the blood)
- Reduction in blood O2 stimulates production of erythropoietin in the kidney and liver which acts on bone marrow to produce more RBC
What do andeans do to overcome high altitude?
Andeans Increase the number of RBC and blood HB content (increases O2 capacity of the blood)
What do tibetans do to overcome problems of high altitude?
They increase their oxygen intake by taking more breaths per minute than people who live at sea level
Is hyperventilation voluntary or involuntary?
Can be involuntary (anxiety or panic) or voluntary
What does voluntary hypoventilation cause?
Before diving it can cause dangerous shallow water blackout due to hypocapnia
- CO2 dilates blood vessels
- Abnormally low CO2 level results in failure in urge to breathe
