Nervous System Flashcards
Define: nerve net, nerve, cephalization, ganglia, CNS, PNS
Cephalization - is the clustering of sensory organs and neurons (in a brain) near the front end of animal
Ganglia - clusters of neurons
CNS - consists of the brain and longitudinal nerve cord(s
PNS - consists of nerves connecting the CNS with the rest of the body
What are the three stages of information processing in the nervous system?
Sensory input - transmit information from sensors that detect external stimulation
Integration - interneurons in CNS integrate (analyze and interpret) sensory input and generate motor output
Motor output - motor output leaves CNS via motor neurons that communicate with effector cell
What is the resting potential of a neuron and how is it generated? What does the negative sign indicate?
When a neuron is not sending a signal, it is “at rest.” When a neuron is at rest, the inside of the neuron is negative relative to the outside
Under what circumstances could ions flow through ion channels from a region of low ion concentration to a region of high ion concentration?
- Na+ concentration is higher OUTSIDE the cell (so is Cl- concentration)
- K+ concentration is higher INSIDE the cell
- Concentration of other anions (-ve charge) is also higher INSIDE the cell
Why is the resting potential of neurons different from the equilibrium potentials of K+ and Na+?
The inside of the cell becomes negative relative to the outside, setting up a difference in electrical potential across the membrane. System moving towards equilibrium: … The movement of K+ ions down their concentration gradient creates a charge imbalance across the membrane
Define hyperpolarization, depolarization
Hyperpolarization increases the size of the membrane potential so that the inside of the cell becomes more negative (further from 0).
Depolarization decreases size of membrane potential so that the inside of the cell becomes less negative (closer to 0). This is caused by opening of gated Na+ channels, increasing the Na+ permeability
What is an action potential? What is the function of APs in the nervous system?
When a stimulus causes depolarization that reaches the threshold, an Action Potential (AP) is generated. APs are all-or-nothing responses in which the membrane potential changes from negative to positive
Describe the 5 steps involved in generation of an action potential.
- Resting state: Na activation gates close and Na inactivation gate is open. K is also closed
- Depolarization: stimulus rapidly opens some Na activation gates allowing Na to enter the cell
- Rising phase: Depolarization opens more and more Na activation gates causing further depolarization of neuron.
- Falling phase: inactivation gates on Na channels slowly stop influx of Na
Activation gates on K channels open causing K to rapidly exit cell - Undershoot: K channels close slowly, the membrane potential becomes more negative than rest potential
How are APs conducted along axons?
To do this APs regenerate themselves along the axon. An AP is initiated in axon hillock due to some stimulus. Na+ influx creates an electrical current which depolarizes the neighbouring region of membrane.
What is the refractory period in a region of neuron’s membrane and why does it occur?
During falling phase and undershoot, inactivation gates/loops on Na+ channels are closed meaning that a second depolarizing stimulus cannot trigger an AP
Describe the two types of synapse
Electrical synapses contain gap junctions that do allow electrical current to flow from cell to cell
Chemical synapses transmit information between cells by the release of chemical neurotransmitters from the pre-synaptic cell
What is the difference between white and grey matter in the CNS?
Grey matter, which has a pinkish-grey color in the living brain, contains the cell bodies, dendrites and axon terminals of neurons, so it is where all synapses are. White matter is made of axons connecting different parts of grey matter to each other.
