Neuronal Communication Flashcards
Give two reasons why a refractory period should follow an action potential?
- Ensures action potentials are unidirectional
- Ensures action potentials occur as discrete impulses
List three factors that affect the rate of conduction of an action potential:
- Myelination
- Temperature
- Axon diameter
Name two types of synapses:
- Excitatory synapse
- Inhibitory synapse
What effect do inhibitory synapses have on the post-synaptic membrane?
Hyperpolarisation (Cl-)
What term describes the process in which more than one impulse is needed to generate an action potential at a synapse?
Summation
Name the process by which an action potential is generated from a single presynaptic neurone releasing neurotransmitters a number of times.
Temporal summation
Name the process by which an action potential is generated from multiple presynaptic neurones releasing neurotransmitters.
Spatial summation
What is a response?
An action carried out by an effector
What is a stimulus?
A change in the external/ internal environment of an organism
What are the two main features of sensory receptors?
- Contain specialised cells
- Act as transducers
What do olfactory receptors detect?
Volatile chemicals
What do gustatory cells detect?
Soluble chemicals
Explain how changes in the pressure in the skin leads to the generation of an impulse in the sensory neuron.
When the Pacinian Corpuscle is deformed by the pressure, stretch mediated Na ion channels open in the sensory neurone. Na ions enter the sensory neurone by diffusion across the electrochemical gradient, depolarising the membrane and generating an action potential
What are the Nodes of Ranvier?
Gaps in the myelin sheath which expose the axon of the neurone to the extracellular fluid
Explain how an action potential is generated:
At resting potential, the inside of the cell is more negative (-70mV) than the outside of the cell due to the action of the Na/K pump. 3 Na out and 2 K in via active transport from the tissue fluid outside of the axon. All voltage gated channels are closed at this point. All Na are closed with a few K open causing some K ions to diffuse.
When pressure is applied to the Pacinian corpuscle, it is deformed and stretch mediated Na ion channels are opened, causing the diffusion of Na across the electrochemical gradient into the sensory neurone, depolarising the neurone and generating an action potential. The potential difference increases to -55mV which induces a positive feedback reaction, some Na voltage gated ion channels open causing Na to diffuse across the electrochemical gradient into the axon from the extracellular tissue. +40mV is reached (peak action potential), once depolarisation has reached the threshold potential, it generates an impulse.
