11) Distinguish between spatial and temporal summation, and between excitatory and inhibitory neurotransmitters Flashcards
Define “Summation”
the process by which graded potentials add together
What causes spatial summation? Temporal summation?
Spatial summation results from the buildup of neurotransmitters released simultaneously by SEVERAL presynaptic end bulbs
Temporal summation results from the buildup of neurotransmitter released by a SINGLE presynaptic end bulb two or more times in rapid succession
Spatial summation is the summation of postsynaptic potanetials in response to stimuli that occur at ______ in the membrane of a postsynaptic cell at _____ time(s).
Spatial summation is the summation of postsynaptic potanetials in response to stimuli that occur at DIFFERENT LOCATIONS in the membrane of a postsynaptic cell at the SAME time(s).
Temporal summation is the summation of postsynaptic potanetials in response to stimuli that occur at ______ in the membrane of a postsynaptic cell at _____ time(s).
Temporal summation is the summation of postsynaptic potanetials in response to stimuli that occur at THE SAME LOCATION in the membrane of a postsynaptic cell at DIFFERENT time(s).
Suppose that EPSPs summate in a postsynaptic neuron in response to simultaneous stimulation by the neurotransmitter glutamate, serotonin, and acetylcholine released by three separate presynaptic neurons. Is this an example of spatial or temporal summation?
Spatial summation
Which statement is true?
a) a single postsynaptic neuron receives input from many presynaptic neurons
b) a single postsynaptic neuron receives input from one presynaptic neuron
c) several postsynaptic neurons receive input from many presynaptic neurons
d) several postsynaptic neurons receive input from a single presynaptic neuron
b
T/F
The sum of all excitatory and inhibitory effects of presynaptic neurons at any given time determines the effect on the postsynaptic neuron
True
If total excitatory effects are greater than total inhibitory effects but less than threshold level of stimulation, the result is an _____ that (does/does not) threshold
the result is an EPSP that DOES NOT reach threshold
T/F
Following EPSP, subsequent stimuli can more easily generate a nerve impulse through summation because the neuron is partially polarized
False -
Following EPSP, subsequent stimuli can more easily generate a nerve impulse through summation because the neuron is partially DEPOLARIZED
What causes a nerve impulse? (in terms of EPSPs and IPSPS?)
If the total excitatory effects are greater than the total inhibitory effects, and the threshold is reached, one or more nerve impulses will be triggered.
Impulses continue to be generated as long as the EPSP is at or above threshold level
T/F
If the total excitatory effects are greater than the total inhibitory effects, regardless of threshold, a nerve impulse will be triggered.
False - the total excitatory effects must be greater than the total inhibitory effects, yes, but the threshold MUST be reached.
When does an IPSP occur? How does this impact the postsynaptic neuron?
if the total inhibitory effects are greater than the excitatory effects, the membrane hyperpolarizes
The results in the inhibition of the postsynaptic neuron and an inability to generate a nerve impulse.
Suppose that the net summation of the EPSPs and IPSPs is depolarization that brings the membrane potential of the trigger zone of teh postsynaptic neuron to -60 mV. Will an action potential occur in the postsynaptic neuron?
Since -60 mV is below the threshold, an action potential will not occur in the postsynaptic neuron.
Define neurosecretory cells.
Cells that secrete hormones
Which of the following is an example of neurosecretory cells?\
a) a neuron that secretes hypothalamic releasing hormone
b) a neuron that secretes inhibiting hormone into blood capillaries of the hypothalamus
c) a neuron that secretes oxytocin into the blood capillaries
d) a neuron that secretes antidiuretic hormone into the blood capillaries of the posterior pituitary
e) all of the above
e
Define “neurotransmitters”
chemical substances that neurons use to communicate with other neurons, muscle fibers, and glands
Neurotransmitters are chemical substances that neurons use to communicate with other:
a) neurons
b) effectors
c) muscle fibers
d) glands
e) neurons and muscle fibers
f) a, c, d are true
g) a and d are true
f
What are the two major classes of neurotransmitters? What determines these two classes? Give examples of each.
2 classes based on size:
1) Small-molecule NTs (acetylcholine, amino acids, biogenic amines, nitric oxides)
2) Neuropeptides (enkephalins, endorphins, substance P)
What amino acids have powerful excitatory effects? Powerful inhibitory effects?
glutamate
Gamma-aminobutyric acid
glycine
aspartate
Powerful excitatory effects - glutamate, aspartate
Powerful inhibitory effects - GABA, aspartate
Most excitatory neurons in the CNS and 50% of the synpases in the brain communicate via:
a) GABA
b) aspartate
c) glutamate
d) glycine
e) dopamine
c
This neurotransmitter binds to ionotropic receptors and opens causing an inflow of cations, causing an EPSP.
a) GABA
b) glutamate
c) aspartate
d) norepinephrine
e) epinephrine
b
Approximately 33% of all brain synapses consist of this inhibitory neurotransmitter:
a) GABA
b) glutamate
c) dopamine
d) glycine
e) epinephrine
a
The binding of ____ to ionotropic receptors opens Cl- channels found only in the CNS, where it is the most inhibitory neurotransmitter.
GABA
Approximately 1/3 of all inhibitory brain synapses and 1/2 of inhibitory synapses in the spinal cord uses ____
GABA
Antianxiety drugs like diazepam/Valium enhance the action of _____
GABA
50% of inhibitory neurotransmitters in the spinal cord use ____ and 50% use _____. The binding of these neurotransmitters opens Cl- channels
GABA and Glycine
____ are modified decarboxylated amino acids
biogenic amines
Most biogenic amines bind to _____ receptors
metabotropic
Biogenic amines cause:
a) excitation
b) inhibition
c) excitation and inbhibition
c - both (it depends on the type of metabotropic receptor at the synapse)
What are catecholamines?
It is a chemical classification that includes an amino group (-NH2) and a catechol ring composed of six carbons and two adjacent hydroxyl (-OH) groups)
They include:
- norepinephrine
- dopamine
- epinephrine
This biogenic amine is synthesized from the amino acid tyrosine
catecholamines
Catecholamine is broken down by what two enzymes?
catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO)
This neurotransmitter is secreted by the adrenal medulla that produces action similar to those that result from sympathetic stimulation:
a) dopamine
b) serotonin
c) noradrenaline
d) epinephrine
e) nitric oxide
both c and d
This neurotransmitter plays a role in arousal, dreaming, and regulating moood
norepinephrine
This neurotransmitter is active during emotional resposnes, addictive behaviours, and pleasurable experiences.
dopamine
This neurotransmitter helps regulate skeletal muscle tone and some aspects of movement due to contraction of skeletal muscles
dopamine
The stiffness of Parkinson’s disease is due tot he degeneration of neurons that release_____
dopamine
One form of schizophrenia is due to the accumulation of excess_____
dopamine
Biogenic amines include:
a) catecholamines
b) seratonin
c) nitric oxide
d) more than one
e) Purines
d - catecholamines, seratonin, and purines
This neurotransmitted is concentrated in neurons within the raphe nucleus
serotonin
What is the function of the raphe nucleus? What neurotransmitter contributes to these functions?
involved in sensory perception, temperature regulation, mood control, appetite, and induction of sleep.
Serotonin
The characteristic ring structure of adenosine triphosphate is called a ____ ring
purine
adenosine and its triphosphate, diphosphate, and monophosphate derivatives is an _____ (inhibitory/excitatory/both) neurotransmitter in the ____ (CNS/PNS/both)
excitatory
both
These two neurotransmitters are released together from some symapthetic neurons in the PNS
ATP and norepinephrine
This neurotransmitter is involved in sensory perception, temperature regulation, mood control, appetite, and induction of sleep
serotonin
What neurotransmitters help regulate moood?
serotonin and norepinephrine
Where is NO secreted?
brain, spinal cord, adrenal glands, and erves to penis
The enzyme nitric oxide synthase (MOS) catalyzses formation of ____ from amino acid arginine
nitric oxide
T/F
Nitric oxide is formed on demand and acts immediately
true
Nitric oxide lasts for ten seconds before it combines with ____ and ____ to form inactive nitrites and nitrates
oxygen and water
T/F
Serotonin may play a role in memory and learning
false - nitric oxide
this neurotransmitter is produced by phagocytic cells to kill microbes and cancer cells
nitric oxide
This neurotransmitter is released by endothelial cells in blood vessel walls, where it diffuses into smooth muscle cells and causes vasodilation
nitric oxide
This neurotransmitter contributes to vasodilation in smooth muscle cells, which lowers blood pressure and causes erection
nitric oxide
Viagara alleviates the effects of erectile dysfunction by enhancing the effect of _____
Nitric oxide
What are the inhibitory small-molecule neurotransmitters? Excitatory ones?
Inhibitory: GABA, glycine,
excitatory:
nitric oxide
biogenic amines - Purines (ATP), serotonin, catecholamines (norepinephrine, epinephrine, dopamine), aspartate, glutamate
What is another name for 5-hydroxytryptamine (5-HT)
serotonin
