Download Synaptic Transmission: Exploring the Mechanisms of Neural Communication and more Exams Health sciences in PDF only on Docsity!
NS 4320 SYNAPSE EXAM 2 WITH COMPLETE
SOLUTIONS!!
Who is Charles Scott Sherrington - ANSWER - Demonstrated and coined 'synapse'
- Inferred several properties through experiments on the Reflex Arc The circuit from sensory neuron to muscle response is called a ___________ -Reflex Arc ANSWER
Leg Flexion Reflex -response of muscle (a purely behavioral observation) ANSWER - Measurement of time between stimulation of skin and
The speed of conduction through the reflex arc was slower than the known speed ofconduction along an uninterrupted axon, this is _______________________ - ANSWER - Sherrington's observations and conclusions (1): Delayed Transmission: a dog's foot is pinched, and the dog flexes that leg after a short delay this is an example of ________________ - ANSWER Delayed Transmission Sherrington's observations and conclusions (2): Temporal Summation: -cumulative and produce a reflex ANSWER - Repeated stimuli occurring within a brief time are Ex. Pinch the leg once --> no response Ex. Pinch leg several times quickly --> movement
Ex. More rapid the pinching --> greater the movement Pinching the leg several times in fast succession results in a reflex this is an example of________________ - ANSWER Temporal Summation
Sherrington's observations and conclusions (3):Spatial Summation: - ANSWER -- Spatial Summation: several synaptic inputs originating from separate locations at the same time are cumulative and produce areflex ex. Pinching the leg in one place --> nothing happens ex. Pinching the leg in two different places --> movement pinching leg in two different places at once results in movement this is an example of ________________ - ANSWER Spatial Summation What are three of Sherrington's observed properties of reflexes suggesting specialprocesses at the junctions between neurons (synapses)? - ANSWER -Reflexes are slower than conduction along an axon -Several weak stimuli presented at nearby places or times produce a stronger reflexthan one stimulus alone does
-When one set of muscles becomes excited, a different set becomes relaxed What did John Eccles find? -depolarizations of the postsynaptic membrane ANSWER single neuron recordings - graded
The synapse consists of 2 neurons, where? -Terminal ANSWER o Neuron 1: at the Presynaptic o Neuron 2: at the Postsynaptic Membrane
- Eccles: Inhibitory Postsynaptic Potentials (IPSPs) o When flexor muscles contract, interneuron in spinal cord generates _____________ onthe neuron that control the extensor muscles - ANSWER - Hyperpolarizations, or IPSPs
What happens in an IPSP? -decreasing the probability of an action potential (the inside becomes more negative) ANSWER - IPSPs increase negative charge on membrane,
In an IPSP (through the synaptic input) what does the the postsynaptic membrane do? -ANSWER - opens potassium channels (K+ leaves cell) and opens chloride channels (Cl- enters cell) In an IPSP, the opening of K+ and Cl- channels results in what? -the cell inside more negative, Active brake mechanism against excitation (action ANSWER - As a result, potential less likely) What does it mean for a neuron to have a spontaneous rate of firing? -periodic production of action potentials even without synaptic input ANSWER - A
What did Thomas R. Elliot suggest based on results from his experiment? -experimented with the effects of adrenaline on organs ANSWER -
- Suggested that synapses use chemicals to link neurons What did Otto Loewi demonstrate? -transmission between neurons (nerves send messages by releasing chemicals) ANSWER - the chemical nature of impulse
Explain Loewi's experiment: -heart, decreasing the heartbeat; when he transferred fluid from that heart to another ANSWER -He stimulated the vagus nerve to one frog's frog's heart, he observed a decrease in its heart rate
Chemical that is released by a neuron at the synapse and that stimulates anotherneuron - ANSWER - Neurotransmitter (NT)
What are the typical classes of neurotransmitters? (6) - ANSWER - amino acids
- peptides
- acetylcholine- monoamines
- purines- gases
Neurons synthesize NTs from amino acids in the diet -acetylcholine (NT) ANSWER o Choline - o Phenylalanine - catecholamines (NT) o Tryptophan - serotonin (NT) What are the two locations of NT synthesis? -NTs ANSWER o Presynaptic terminal, smaller o Soma/Cell body, larger NTs (body=large) What happens with excess neurotransmitters? -into inactive chemicals in the Presynaptic Terminal ANSWER - Enzymes break them down
After synthesis, where are larger neurotransmitters transported to? -various cell locations ANSWER -
Why do neuropeptides (larger neurotransmitters) get exhausted quickly? -They intrinsically have slow production and use, so they are not reabsorbed and ANSWER - recycled like smaller neurotransmitters are __________ can also be released by the cell body, dendrites, or along axon - ANSWER
o At transmitter-gated channels o Quick start with short duration (5 ms half life)o Localized effect on membrane o Immediately opens ion gateso Used for quick transmission like in vision, hearing, muscle, movements, etc.
What kind of effect? - ANSWER - Ionotropic effect o Late start (30 ms) with duration up to many minutes o Activates g-protein in cello G-protein activates second messenger system o NTs - various, also neuropeptides o Affect much of cell§ Open or closes ion channels § Change protein production § Widespread effects, typical for other senses, arousal, attention, & emotion -ANSWER - Metabotropic effect
What happens when a G-protein activates second messenger system in a metabotropiceffect? - ANSWER - The second messenger communicates to many areas within the cell
- It may open or close ion channels in the membrane how do metabotropic effects affect much of the cell? -closing ion channels or by changing protein production ANSWER - By opening or
Where are neuropeptides synthesized? - ANSWER - In the Cell Body
Neuropeptides are released by ___________ -and sides of axon) ANSWER - Dendrites (but also cell body
Describe Reuptake: -taken back up (often by transporter/membrane proteins) ANSWER - Neurotransmitters detach from the receptor and are
Describe Inactivation: - ANSWER - NT broken down by enzyme, parts taken back What neurotransmitter has many ionotropic synapses? -(ACh) nicotinic receptors, ionotropic effects open Na+ channel ANSWER - Acetylcholine
What are neuropeptides important for? -changes in behavior and experience ANSWER - Hunger, thirst, and other long-term
What are some of the symptoms of inhibition of acetylcholinesterase? -Small pupils, muscle spasms, vomiting excessive salivation, urination, defecation, ANSWER - respiratory arrest ____________ are receptors that respond to the released transmitter by inhibiting furthersynthesis and release (they provide negative feedback) - ANSWER - Autoreceptors
Why are synapses the major gateway for modulating our nervous system by drugs? -ANSWER - All drugs that affect behavior act on synapses
What drug is used to treat Parkinson's diseaseand also is used to increase the supply of dopamine? - ANSWER L-DOPA
What is a gap junction? -the membrane of another ANSWER - The CONTACT a membrane of one neuron has with
What happens at an electrical synapse? - ANSWER - Electrical current flows directly
