RESP Flashcards
What is Daltons Law?
total pressure = sum of all partial pressure
why?
what is Boyle’s law?
at a constant temperature, the absolute pressure of a fixed amount of gas is inversely proportional to its volume
P1V1 = P2V2
using Dalton’s law, what will the total lung capacity of someone (age 23) with a lung volume of 8 litres at the surface be once they have dived to 160m?
P1V1 = P2V2 8x1 = 17 x V2 8/17 = V2 V2 = 0.47L 470mls
what is Henry’s law in relation to concentrations of dissolved gases?
when a gas is in contact with a liquid, it dissolves in proportion to its partial pressure
therefore a greater concentration of a particular gas in the gas phase, more of it dissolves into the solution at a faster rate
C = P x Solubility
what is the alveolar gas equation?
PAO2 = PiO2 - PaCO2/R
why is surfactant important?
surfactant is produced by type ii pneumocytes and markedly reduces the cohesive forces between water molecules on the alveoli surface
it therefore lowers the surface tension which makes lung increases lung compliance and makes it easier to expand the lungs
what occurs during parasympathetic bronchoconstriction?
Vagus nerve neurons terminate in the parasympathetic ganglia in the airway wall
short post-synaptic nerve fibres on the ganglia reach the muscle + release acetylcholine (ACh) which acts on muscarinic receptors of M3 subtype on muscle cells
this stimulates airway smooth muscle constriction
what occurs during sympathetic bronchodilation?
sympathetic nerve fibres release noradrenaline and this activates adrenergic receptors (either alpha or beta)
sympathetic nerve fibres in airway smooth muscle cells have beta adrenergic receptors
activation of these beta 2 receptors on the airway of the smooth muscle causes muscle relaxation
what are the two main types of cholinergic receptors involved in respiration?
nicotinic
muscaranic
what do nicotinic receptors respond to?
acetylcholine and nicotine
what stimulates nicotinic receptors?
Both sympathetic and parasympathetic systems
Mainly parasympathetic
where are nicotinic receptors found?
post ganglionic neurons
neuro-muscular function
what stimulates muscarinic receptors?
parasympathetic systems
how many types of muscarinic receptors are there?
5
M1,M2,M3,M4,M5
what is the role of the M3 receptor?
it is found in the lungs and when acetylcholine binds to it, bronchoconstriction occurs
define hypersensitivity
an excessive response by the immune system to things that do not need to be responded to
what are the types of hypersensitivity according to Gell and Coombs’ classification?
type I
type ii
type iii
type iv
what is an example of type I hypersensitivity?
anaphylaxis
what mediates type I hypersensitivity?
IgE
what happens during a type I hypersensitivity reaction?
there is an immunological memory to something which causes a immediate and often severe allergic response.
free antigens cross link IgE on mast cells and basophils which causes the release of vasoactive substances
what is histamine?
a chemical released by mast cells when an antigen binds to IgE, connected to receptors on the cell surface
what effect does histamine have locally?
it causes increased venule permeability which causes some arterial dilation and contracts smooth muscle. this results in a local increase in blood flow and oedema and an increased delivery of immune cells to the damaged area
essentially it causes inflammation
when will a type ii hypersensitivity reaction occur?
when IgM or IgG bind to cell surface associated antigens
what does a type ii hypersensitivity reaction lead to?
tissue injury or altered receptor function
