Homeostasis and Neurophysiology Flashcards
(27 cards)
In terms of fluid composition.
What makes up the human body?
60% of total body weight is water, 40% of total body weight is intracellular fluid (ICF), 20% of total body weight is extracellular fluid (ECF).
What is extracellular fluid comprised of?
Blood plasma and tissue fluid (a.k.a. interstitial fluid, ISF).
What is bioelectricity?
The electrical potentials generated by living cells and tissues.
What is tonicity?
Relative concentration of solute inside the cell compared to outside the cell. 3 types: hypotonic, isotonic, hypertonic. Impacts cell volume and function.
What is a hypotonic solution?
A solution with a lower [salt] than inside cell. Water will move into the cell.
What is a hypertonic solution?
A solution with a higher [salt] than inside cell. Water will move out of the cell.
Describe the properties of ion channels.
Made from membrane proteins (these could be receptors), can be highly selective, can be modulated, transport is passive. Stimuli cause opening / closing of ion channels.
What does the term open probability refer to?
The likelihood of ion channels being open.
What is electrophysiology?
Study of how electrical signals are generated, propagated, and regulated within the body.
How is the equilibrium potential established?
It is established through the balance of the chemical and electrical gradients to the point where there is no net movement of ions across the membrane
What does the Nernst equation describe?
It is used to calculate the equilibrium potential for a single ion species
Why might a bolus of KCl lead to heart failure?
A large increase in [K ion] would increase the equilibrium potential at rest above the threshold required for action potentials to be triggered. Cardiomyocytes cannot function correctly, heart will not be able to continue beating.
What is the role of the Na ion and K ion channels during an action potential?
Na ion channels open first, allowing Na ions to enter and depolarise the cell. K ion channels open later, allowing K ions to exit and repolarise cell.
How does ionic equilibrium determine resting potential?
Resting potential is maintained by the Na ion / K ion pump and a balance of ionic gradients. Occasional ion leaks occur but are not significant at rest.
What ensures action potential propagation is unidirectional?
Inactivation of Na ion channels creates a refractory period, preventing the action potential from traveling backward.
How does the axon size and myelination affect conduction speed?
Larger axon diameter = faster conduction, Myelination increases speed of propagation by allowing action potentials to jump between Nodes of Ranvier.
What happens during demyelination of nerves?
Ion leaks increase, slowing or disrupting nerve conduction, as seen in conditions like multiple sclerosis.
How do action potentials in myocytes differ from those in nerve cells?
Myocyte action potentials are longer in duration due to a plateau phase caused by voltage-gated Ca ion channels, allowing time for full muscle contraction.
What regulates the duration of cardiac action potentials?
Different regions of the myocardium use distinct combinations of ion channel sub-types, resulting in varied action potential durations.
What is the function of the plateau phase in myocyte action potentials?
The plateau ensures that the muscle has enough time to fully contract before the action potential ends.
What happens at the neuromuscular junction?
Ach binds to ligand-gated Ach receptors, causing ion flow which generates an end-plate potential. This can initiate muscle action potentials and contraction.
What is an end-plate potential?
The degree to which the motor end plate is depolarised. Summation of these potentials can lead to a muscle action potential.
Why are some nerves unmyelinated?
Unmyelinated nerves, like those for dull pain, conduct signals more slowly, which is adequate for their function.
How is the frequency of action potential initiation related to signal intensity?
Higher frequency of action potentials indicates a more intense signal, such as stronger pain, but is limited to about 1000 action potentials per second.
