Regulation of Respiration Flashcards
What are the structural features of gills?
- invaginated extension of the body surface
- highly folded to increase surface area
- protected by a specialised cover (operculum)
- pumping mechanism moves water over gills
- internal circulatory system distributes blood throughout the gills and body
What are the directions of blood flow across gills?
- deoxygenated blood - afferent blood vessel
* oxygenated blood - efferent blood vessels
What is the function of lamellae?
- increase surface area for gas exchange
* reduce the diffusion path - length between water and blood
What happens when there is a concurrent flow of blood and water?
- water and blood is flowing in the same direction
- huge difference between amount of oxygen in water and deoxygenated blood
- the 2 reach equilibrium and oxygen uptake is not maximised
How does a countercurrent flow of water and blood increase gas exchange?
- water and blood flow in opposite direction
* blood vessels constantly comes across water that hasn’t given up oxygen - there is a constant uptake of water
What are the structural and functional features of the lungs?
- invaginated, internalised extension of the body surface
- highly folded to increase surface area
- protected by ribs and thorax
- ventilation mechanism moves air in and out of lungs
- internal circulatory system distributes blood throughout the lung and body
Trachea function
Conducts air into the body
Bronchi
Branches off from the trachea
• They are the major passageways of the lung
What do bronchi branch into?
- Bronchioles
* at the end of bronchioles are alveoli
When do bronchioles constrict/dilate?
- bronchioles dilate during exercise (more air needed)
* bronchioles constrict for people who have asthma
Why does gas exchange occur at the alveoli?
- alveolar walls and capillary walls are very thin
* the endothelial and epithelial cells are very thin which minimises diffusion distance
What is the difference between epithelial and endothelial cells?
Endothelial: line the interior of blood vessels
Epithelial: coat the inner surface of internal organs
Where are cilia and mucus found?
- epithelial cells lining the airway produce a sticky mucus
* other cells lining airways have cilia
Function of mucus
Captures inhaled dirt and microorganisms
Function of cilia
Constant beating continually sweeps the mucus, with its trapped debris up towards the pharynx
What differs in the normal airway and the airway of someone with cystic fibrosis?
Normal
• cl- leaves via ion channel
• water follows via osmosis
• water allows cilia to sweep away foreign particles
CF
• lack of cl- channels causes a thick mucus to form
• cilia cannot beat properly and remove bacteria
what are surfactants
Substances that reduce the surface tension of a liquid
Why are surfactants needed in the lungs?
- results in less force required to inflate lungs
- without it lungs would be like wet tissue paper and very difficult to separate and will collapse - prematurely born babies may not have developed enough surfactant to help them breathe
Describe inhalation in reference to the diaphragm
- diaphragm contracts and pulls down on the thoracic cavity and the lungs
- air enters through trachea
- lungs expand (negative pressure)
Exhalation in reference to the diaphragm
- diaphragm relaxes
- elastic lung tissue pull the diaphragm back up
- this pushes the air out of the lungs and out the airways (positive pressure)
Inhalation related to intercostal muscles
- contraction of external intercostals
* this pushes out ribs and increases thoracic volume
Exhalation related to intercostal muscles
- contraction of internal intercostal muscles
* pulls in ribs and decreases thoracic volume
Respiratory centre in the brain
- brainstem - medulla and pons
* determines the depth, amplitude and frequency of breathing
What is the function of the phrenic nerve?
Controls the contraction and lowering of diaphragm
What are the sections of the brainstem and what happens if it is sliced in different regions?
Pons > Medulla > Spinal cord
Sliced in bc medulla and pons
• Can’t choose to regulate breath anymore but can still breath (in response to external stimuli)
Sliced in bw medulla and spinal cord
• breathing stops completely
What is breathing rate most sensitive to and why?
- Breathing rate is more sensitive to increased CO2 than to decreased O2
- increase in pCO2 causes an increase in breathing rate to match metabolic demand
Where are chemoreceptors found and what stimuli do they respond to?
Ventral surface of the medulla (brainstem)
• sensitive to increases in pCO2 (via changes in pH)
Aortic and carotid bodies (heart)
• sensitive to increases in CO2 and large decreases in pO2
What are the short-term changes in response to hypoxia?
- animal hyperventilates due to chemoreceptors in aortic and carotid bodies (or in gills for aquatic animals)
- reduce energy expenditure
- use anaerobic metabolic pathways to survive periods of reduced O2 availability
- increased BPG
Long-term changes that occur in response to hypoxia
- reset the thresholds of chemoreceptors for O2 so they are more sensitive to low pO2
- increase the number of red blood cells and blood Hb content (increases O2 capacity in blood)
- stimulates production of erythropoietin in the kidney and liver - this acts on bone marrow to produce more red blood cells
What is the downside to increasing the number of blood cells and Hb content?
Can lead to sticky blood
How does voluntary hyperventilation cause shallow water blackout?
• due to hypocapnia
Normal breathing before dive
• the oxygen levels decrease and CO2 increase simultaneously
• this triggers the urge to breathe
Hyperventilation before dive
• CO2 levels do not increase as fast
• O2 reaches low levels before low CO2 is detected
• failure in urge to breathe so blackout occurs
