- Information
- AI Chat
Membrane action potentials
The Human Body (PY4010)
Kingston University
Students also viewed
Preview text
Membrane & action potentials
Concentrations of Na and K inside/outside the cell Potassium is high inside relative to outside. Sodium is high outside relative to inside. The Na/K pump
Membrane potential The voltage across the plasma membrane. Resting potential The membrane potential of a cell not sending signals. Potassium leak Potassium moves out of the cell down its concentration gradient. It can leave the cell through potassium channels in the cell membrane. This leaves behind the negatively charged anions.
3 sodium out and 2 potassium in.
Extra info ^^ but explains process
Electrical gradient There is a seperation of charge across the membrane with a more negative charge inside the cell.
We have a seperation of positive and negatively charged ions ⇒ this leads to a potential difference. Key points from above Chemical gradient is established by the Na/K pump. Electrical gradient is established by potassium “leak”. Seperation of charge over the membrane means there is a voltage established. Equilibrium potential The membrane potential at which the electrical and chemical gradients of a specific ion are balanced.
Nernst equation Used to calculate equilibrium potential of a specific ion in a cell.
The stimulus needs to cause sufficient depolarisation to raise the voltage above the threshold. The membrane potential does not reach sodium equlibrium potential as channels inactivate.
The action potential spreads along the axon. This is how nerves send electrical signals. At the synapse, an action potential will cause neurotransmitter release. Cardiac action potential Action potentials underlie the electrical conduction system in the heart. This controls the rhythm and synchronicity of contractions of the heart. Stage 0 (Depolarisation) ⇒ sodium channels open Stage 1 (Repolarisation begins) ⇒ sodium channels inactivate and potassium channels open Stage 2 (Plateau) ⇒ potassium channels are still open but some calcium channels are activated too which results in this plateau phase we don’t see in neurones Stage 3 (Repolarisation) ⇒ calcium channels close and potassium channels open Stage 4 ⇒ most sodium and potassium channels are closed
Neuronal vs Cardiac
Compare difference in: Resting membrane potential Shape of the action potential (triangle for neuronal and n for cardiac) Action potential duration (faster in neuronal rather than cardiac)
In cardiac: RMP lasts 300msecs. In neuronal: RMP lasts
Membrane action potentials
Module: The Human Body (PY4010)
University: Kingston University
