Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
13 Cards in this Set
- Front
- Back
|
What are the typical resting membrane potentials in neurons, skeletal muscle fibers & rods?
Explain the membrane channels which establish these resting potentials? |
Neurons: -65 mV
-A large # of K+ channels open, some Cl- channels open & few NA+ channels open Skeletal muscle fibers: -90 mV -large # of K+ & Cl- channels open & few Na+ channels open Rods (photoreceptors): -40 mV -relatively more NA+ channels open than neurons & muscle fibers |
|
|
The Na+/K+ ATPase transfers how many K+ & Na+ in what direction?
What kind of charge diference does this pump ultimately lead towards? |
3 Na+ ions transported out as 2 K+ ions go inwards
It leads to a net loss of + charges within the cell |
|
|
What are symports or antiports?
|
proteins that shuttle ions by using the gradient of one ion or molecule to create energy to transfer another molecule in the same direction (symports) or opposite direction (antiport)
|
|
|
What happens when [K+] is increased inside a cell?
|
Depolarization of the cell
This causes a reduction in the rate of K+ ion loss from the cell and the interior becomes less negative |
|
|
What happens when [K+] is decreased inside a cell?
|
Hyperpolarization of the cell
This causes an increase in the rate of K+ ion loss from the cell and interior becomes more negative |
|
|
What are three pumps which maintain Na+, K+, H+ & Ca2+ levels?
|
Ca2+ ion ATPase
H+ ATPase Na+/K+ ion ATPase |
|
|
What ion strongely influences neuron and skeletal muscle membrane potentials?
|
In resting neurons K+ flux stongely influences resting potential whereas skeletal muscle cells are highly influenced by K+ and Cl-
|
|
|
How do ion channels function as conductors in the cell membrane?
|
Conductance is the inverse of electrical resistance...
Total membrane conductance for an ion is the number of channels for that ion times that channels conductance. gx - membrane conductance Nx - # open channels for ion x yx - single channel conductance gx = (Nx)(yx) |
|
|
The electrical chemical gradient for K+, Na+ & Ca2+ inside a neuron are +15mV, -127mV & -188mV respectively. What direction will these ions passively flow?
|
The resting membrane potential for a neuron is -65mV
K+ will passively leave, but this loss is matched by the active K+ uptake Na+ & Ca2+ will passively flow into the cell if channels were open |
|
|
What are the typical equilibrium potentials for Na+, Cl-, Ca2+, & K+ ions in skeletal muscle fibres and neurons?
|
Neurons: Em is -65mV
Na+: +62mV Cl-: -65mV Ca2+: +123mV K+: -80mV Muscle fibers: Em is -90mV Na+: +65mV Cl-: -90mV Ca2+: +132mV K+: -95mV |
|
|
What does the electrical equivalent circuit model of a cell membrane potential tell us?
|
The model can be generalized to describe the entire surface of the cell, noting that:
-the capacitance of entire cellular surface is the sum of all membrane patch capacitances -the total membrane conductance is the sum of all conductances of open channels |
|
|
What is Ischaemic Cerebral Edema?
What is this form of edema called and how does it affect white and grey matter? Why does edema happen? What 2nd type of edema follows? |
Ischaemic Cerebral Edema is an interruption to the cerebral blood supply which causes irreversible cellular damage due to cellular swelling
This edema is called "cytotoxic edema". It affects grey (cells) matter more than white (axons) matter. Failure of ATP for the Na+/K+ pump allows Na+ & Cl- to enter the cells and K+ leaves. The Na+ & Cl- ions pull H2O through aquaporins into the cell causing cell swelling. Thus ischaemia first causes cytotoxic edema followed by "vasogenic edema" in which blood vessels become permiable and fluid accumulates in EC space causing further damage. |
|
|
Why would KCl be used for lethal injection?
|
It raises the EC [K+] which depolarizes excitable cells such as nerve and muscle. Cardiac muscle fails to generate action potentials b/c voltage-gated Na+ channels become inactivated (closed). Death follows from failure of the heart to beat.
|
