Describe the two processes that maintain resting membrane potential?
Diffusion: There are alot of potassiums leaving and only a few sodiums entering. This makes the outside more positive and inside more negative. Active Transport: Pumps are pushing in potassiums and pushing out sodiums to reinforce the charges of in and outides.
Explain how stimulus intensity is determined.
Intensity is determined by frequency of cycles.
Explain how a signal propagates down an axon.
A signal propogates down an axon like a wave or falling dominos, each ones voltage change causing the next one to occur.
Why doesn't a signal go backwards?
The action potential hyperpolarizes to keep the signal from going backwards.
Describe the effects of axon diameter and myelination on teh speed of an action potential.
The larger the diameter and more myelinated an axon is, the fast the signal goes.
Explain how normokalemia, hyperkalemia, and hypokalemia will effect action potential formation.
Normokalemia: A subthreshold graded potential does not fire an action potential and a suprathreshold graded potential does. Hyperkalemia: Brings membrane closer to threshold and signal that wouldn't normally trigger an action potential will. Hypokalemia: Hyperpolarizes membrane and makes the neuron less likely to fire an action potential in response to a stimulus that would normally be above threshold.
List 3 ways to terminate the effects of a neurotransmitter.
-Neurotransmitters degraded by enzymes. -Neurotransmitters are recycled. -Neurotransmitters float away from synaptic cleft.
Describe how physiological addiction occurs.
1)Drugs increase release of neurotransmitters. 2)Postsynaptic membrane loses receptor sites (decreased sensitivity). 3)Drug wears of and neurotransmitters levels go back to normal. 4)Withdrawal occurs.
Define Cholinergenic receptors; List 2 types; their effects; their locations
Bonds to acetylcholine; muscularinic and nicotinic; muscularinic is CNS and PNS Skeletal and cardiac muscles; nicotinic on skeletal muscles in parasympathetic PNS and CNS
Define Andrenergic receptors; two types; their effects; and their locations
Bonds with norepinephrine; alpha a and beta; a is mostly excitatory, beta mostly inhibitory (except heart)
Why is long term potentiation important?
Using neurons often improves its ability to function; May be related to memory and learning; Glutamate is a key element in potentiatiom
Describe the process of PSN axonal repair.
1) Ends of the axon dies. 2) Fragments cleared by phagocytes and microglial cells. 3) Schwann cells splint break, secrete growth factors, and rejoins previous connections.
Why does CNS axonal repair fail?
Fails because glial cells cseal off damages area and secretes growth inhibitors because of the lack of space in the skull.