Lecture 2- What should a nervous system do? Flashcards
What was the big thing in the 16th century and how did it relate to the brain?
-electricity -people were discovering that you could contain it (Leyden jars) -animals like stingray can produce it so people wondered if electricity was the way nerves communicated
Who was Luigi Galvani and what did he do?
- 18th century Italian doctor, proved that elctricity was central to how infromation travels in the nervous system -when you generate electricity you can activate a nerve and then contract a muscle not just contracting a muscle by using electricity
What are nerve cells specialized to do?
-for transmission of electrical signals -nerve cells are little bioelectric devices (like batteries) -the electrical activity can be measured by inserting very small electrodes into the cell
What would you see when recording the difference of potential across a membrane?
-stereotypic event= the same size only thing that changes is how many and how close to each other
How is the difference in membrane potential achieved in the nerve cell?
-by selective movement of ions via ion transporters
What is an ion channel?
-allows ions to diffuse down concentration gradient -usually specific to only one ion -have opening and closing behaviour, may be voltage gated etc.
What is an ion transporter?
-it moves ions against concentration gradient (electrogenic)
What is electrochemical equilibrium?
-ions are free to travel will be equally distributed and no difference in membrane potential -if there are selective channels that let the ion go only one way then with every k+ leaving it leaves behind a more negative environment and goes into more positive= results in change in membrane potential
What is the key to using the membrane potential to create the nerve impulse?
-voltage dependence of the ion channels -Na+ open when depolarisation and will open and close really quickly under a millisecond -some Na goes in and some K goes out every action potential -this is how neurons communicate
How does the membrane potential difference travel through the axon?
-all of the current exchanges occur across membranes -one depolarisation activates the membrane next to it to depolarisation
How does nerve impulse conduction differ in vertebrates and invertebrates?
-vertebrates we have a better way of conducting nerve impulses faster= insulate (whereas invertebrates can only make longer bigger nerves with less resistance) -myelin sheath, then really concentrated channels in the node of ranvier = saltatory conduction
What is the function of a synapse?
-the cells of the nervous system must also integrate, process and store information -covergence and divergence of signals= the Synapse
What percentage of synapses in humans are electrical and what are they good for?
-less than 1% -good for synchronization of neuronal groups (eg. respiratory group)
What is the only effect an electrical synapse can have?
-excitation
What type of transmission occurs in electrical synapses?
-passive transmission, no complex energy-dependent release machinery -fast, no long latency due to complex energy-dependent machinery, diffusion, and post-synaptic receptor activation