how would thick walled alveoli affect the exchange of respiratory gases
Answers
Alveoli are air sacs present at the end of the respiratory tree of the lungs. They are present in a bunch closely linked with each other.
Alveoli are single cell thick to perform exchange of gases. If the size and thickness of alveoli sacs will change or get thicker, it will affect the exchange of gases. There will be difficult in gaseous exchange from the sacs.
"Increase in axonal diameter and myelination
(a)When the axon diameter is increased, the internal resistance to current flow is decreased. As a result, the conduction velocity of the nerve impulse increases. This is seen in the large axons of squids.
(b)When the axon is insulated, the leakage of current to the surroundings is reduced. Thus, the distance travelled by large currents increase which is seen as faster velocity of nerve impulse conduction.
Evolutionary, such insulation is achieved by myelination.
Myelination refers to the process by which a type of nerve cells - The CNS has the oligodendrocytes and the PNS has the Schwann cells - wrap the axons of neurons in myelin providing the said insulation. This myelin wrap is of several layers and is called the myelin sheath.
The myelin sheath is discontinuous with gaps called Ranvier nodes.
Action potential is found at these nodes and thus the generated potential travels passively through the myelinated segment till it reaches the next adjacent node."