Cell membranes and excitation Flashcards
Define various types of excitable cells Describe the basic function and structure of a neurone Define transmembrane resting potential in a neurone and its ionic effect Explain a local non-propagated synaptic or generator potential in an excitable cell Draw a diagram showing the transmembrane potential change associated with an action potential Explain the operation of voltage-gated sodium channels Describe the function of the Na,K ATPase pump Compare the propagation of an action potential in bo
What are the 2 types of excitable cells?
Muscle and nerve cells
What are the 3 types of muscle cells and what is their function?
Smooth, skeletal and cardiac. Contraction
What is a nerve cell called and what is its function?
Neurone. Conduction
Describe the structure of a neurone:
A neurone has a cell body soma consisting of 5-7 dendrites. It then has an axon hillock which is where the AP starts. It then has the main axon which is wrapped in Schwann cells and nodes of ranvier. This then leads to a terminal bouton synapse.
What is the transmembrane resting potential?
It is a form of stored potential energy which can be used to deliver an AP
What leaks out mostly from the membrane out of a neurone?
Potassium
Describe the NaKATPase pump:
Inside the cell 3Na+ ions will move out in place of 2K+ ions which will enter into the cell
What is the electrogenic pump:
Net loss of one positive charge form the cytoplasm to maintain the electrical gradient
What is the voltage within a neurone?
-70mV
Why are voltage gated sodium channels slow to open and close?
So they have time to reset and so there is a gap in the AP
What is the distribution of ions in the intra/extracellular fluid at rest?
The intracellular fluid has a high conc. of K and protein. The extracellular fluid has a high conc. of Na and Cl
What are the 2 types of response from a stimulus:
Local - non-propagated and propagated disturbance
What type of the response does the neurone work by?
All or nothing response
Describe an action potential graph including ionic movement:
Action potential occurs and breaks the threshold
Na enters into the cell on initial increase
Depolarisation
As the graph plateaus the Na channels close and K channels open
As the graph decreases, Ca enters the cell and K leaves
As the graph hits -70mV again this is the absolute refractory period
There is then hyperpolarisation, the membrane resets
Where does the AP start?
At the axon hillock
