Chapter 2 Flashcards
In what way did Sherrington’s conclusions agree with Ramón y Cajal’s conclusions?
Both concluded that neurons are separate from one another.
Sherrington based his conclusions on what type of evidence?
Observations of reflexive responses.
Why did Sherrington conclude that synaptic transmission differs from conduction along an axon?
Reflexes are slower than axonal transmission.
An EPSP is an abbreviation for what?
Excitatory PostSynaptic Potential.
Although one pinch did not cause a dog to flex its leg, a rapid sequence of pinches did. Sherrington cited this observation as evidence for what?
Temporal summation.
The extensor muscles of a leg relax when the flexor muscles contract. Sherrington saw this observation as evidence for what?
Inhibitory synapses.
What channels in a neuron open during an EPSP?
Sodium.
In what way were Sherrington’s conclusions important for psychology as well as neuroscience?
He demonstrated the importance of inhibition.
What evidence led Sherrington to conclude that transmission at a synapse is not the same as transmission along an axon?
The velocity of conduction through a reflex arc is slower than the velocity of an action potential along an axon. Therefore, a delay must occur at the junction between one neuron and the next.
How does temporal summation differ from spatial summation?
Temporal summation is the combined effect of quickly repeated stimulation at a single synapse. Spatial summation is the combined effect of several nearly simultaneous stimulations at several synapses onto one neuron.
Can an inhibitory message flow along an axon?
No. Only action potentials propagate along an axon. Inhibitory messages—IPSPs—decay over time and distance.
How did Loewi demonstrate chemical transmission at a synapse?
He transferred fluid from one frog’s heart to another’s.
What are the brain’s most abundant excitatory and inhibitory neurotransmitters, respectively?
Glutamate and GABA.
Which of these is a catecholamine?
Dopamine.
Why does removing phenylalanine from circulation increase the serotonin in the brain?
Phenylalanine and tryptophan compete for entry to the brain.
Suppose you want to cause the presynaptic terminal of an axon to release its transmitter. How could you do so without an action potential?
Inject calcium into the presynaptic terminal.
What is a second messenger?
A chemical released inside a cell after it is stimulated at a metabotropic synapse
How do the effects of neuropeptides differ from those of other transmitters?
Their effects last longer.
What fact makes it possible to develop drugs with a limited effect, such as suppressing nausea?
Each transmitter attaches to more than one type of receptor.
A transporter protein produces which of the following?
Reuptake.
Except for the magnitude and speed of effects, methylphenidate (Ritalin) affects synapses the same way as which drug?
Cocaine.
How do cannabinoids affect synapses?
They inhibit the release of both excitatory and inhibi-tory transmitters.
Electrical synapses are important when the nervous system needs to accomplish what?
Synchrony between neurons.
What part of the brain produces releasing hormones that control the pituitary gland?
Hypothalamus
Across species, how much do neurotransmitters vary?
Most animals have all or nearly all the same neurotransmitters.
Name the three catecholamine neurotransmitters.
Epinephrine, norepinephrine, and dopamine. Do not confuse the term catecholamine with acetylcholine.
How do ionotropic and metabotropic synapses differ in speed and duration of effects?
Ionotropic synapses act more quickly and more briefly.
Ionotropic synapses are most important for what types of behavior?
Ionotropic synapses are most important when precise timing is important, such as visual or auditory perception.
How do LSD and opiate drugs influence behavior?
LSD binds to one type of serotonin receptor. Opiates bind to endorphin receptors.
What happens to acetylcholine molecules after they stimulate a postsynaptic receptor?
The enzyme acetylcholinesterase breaks acetylcholine molecules into two smaller molecules, acetate and choline. The presynaptic neuron then reabsorbs the choline.
What happens to serotonin and catecholamine molecules after they stimulate a postsynaptic receptor?
Most serotonin and catecholamine molecules are reabsorbed by the presynaptic terminal. Some of their molecules are broken down into inactive chemicals, which then diffuse away.
How do amphetamine and cocaine influence synapses?
They block reuptake of released dopamine, serotonin, and norepinephrine.
- Which part of the pituitary—anterior or posterior—is neural tissue, similar to the hypothalamus? Which part is glandular tissue and produces hormones that control the secretions by other endocrine organs?
The posterior pituitary is neural tissue, like the hypo-thalamus. The anterior pituitary is glandular tissue and produces hormones that control several other endocrine organs.
