Regulation of Respiration

Question 1

What are the structural features of gills?

Answer 1

• 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

Question 2

What are the directions of blood flow across gills?

Answer 2

• deoxygenated blood - afferent blood vessel

* oxygenated blood - efferent blood vessels

Question 3

What is the function of lamellae?

Answer 3

• increase surface area for gas exchange

* reduce the diffusion path - length between water and blood

Question 4

What happens when there is a concurrent flow of blood and water?

Answer 4

• 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

Question 5

How does a countercurrent flow of water and blood increase gas exchange?

Answer 5

• 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

Question 6

What are the structural and functional features of the lungs?

Answer 6

• 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

Question 7

Trachea function

Answer 7

Conducts air into the body

Question 8

Bronchi

Answer 8

Branches off from the trachea

• They are the major passageways of the lung

Question 9

What do bronchi branch into?

Answer 9

• Bronchioles

* at the end of bronchioles are alveoli

Question 10

When do bronchioles constrict/dilate?

Answer 10

• bronchioles dilate during exercise (more air needed)

* bronchioles constrict for people who have asthma

Question 11

Why does gas exchange occur at the alveoli?

Answer 11

• alveolar walls and capillary walls are very thin

* the endothelial and epithelial cells are very thin which minimises diffusion distance

Question 12

What is the difference between epithelial and endothelial cells?

Answer 12

Endothelial: line the interior of blood vessels

Epithelial: coat the inner surface of internal organs

Question 13

Where are cilia and mucus found?

Answer 13

• epithelial cells lining the airway produce a sticky mucus

* other cells lining airways have cilia

Question 14

Function of mucus

Answer 14

Captures inhaled dirt and microorganisms

Question 15

Function of cilia

Answer 15

Constant beating continually sweeps the mucus, with its trapped debris up towards the pharynx

Question 16

What differs in the normal airway and the airway of someone with cystic fibrosis?

Answer 16

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

Question 17

what are surfactants

Answer 17

Substances that reduce the surface tension of a liquid

Question 18

Why are surfactants needed in the lungs?

Answer 18

• 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

Question 19

Describe inhalation in reference to the diaphragm

Answer 19

• diaphragm contracts and pulls down on the thoracic cavity and the lungs
• air enters through trachea
• lungs expand (negative pressure)

Question 20

Exhalation in reference to the diaphragm

Answer 20

• diaphragm relaxes
• elastic lung tissue pull the diaphragm back up
• this pushes the air out of the lungs and out the airways (positive pressure)

Question 21

Inhalation related to intercostal muscles

Answer 21

• contraction of external intercostals

* this pushes out ribs and increases thoracic volume

Question 22

Exhalation related to intercostal muscles

Answer 22

• contraction of internal intercostal muscles

* pulls in ribs and decreases thoracic volume

Question 23

Respiratory centre in the brain

Answer 23

• brainstem - medulla and pons

* determines the depth, amplitude and frequency of breathing

Question 24

What is the function of the phrenic nerve?

Answer 24

Controls the contraction and lowering of diaphragm

Question 25

What are the sections of the brainstem and what happens if it is sliced in different regions?

Answer 25

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

Question 26

What is breathing rate most sensitive to and why?

Answer 26

• 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

Question 27

Where are chemoreceptors found and what stimuli do they respond to?

Answer 27

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

Question 28

What are the short-term changes in response to hypoxia?

Answer 28

• 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

Question 29

Long-term changes that occur in response to hypoxia

Answer 29

• 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

Question 30

What is the downside to increasing the number of blood cells and Hb content?

Answer 30

Can lead to sticky blood

Question 31

How does voluntary hyperventilation cause shallow water blackout?

Answer 31

• 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