Neural Communication Flashcards
Action potential transmits signal from neuron cell body to the axon terminals.
Electrical communication
Neurotransmitters travel across the synapse and bind to post synaptic receptors.
Chemical Communication
Pituitary gland releases corticoptropin releasing hormone to signal to the adrenal glands to release cortisol
Hormonal communication
Communication begins with neuronal transmission from one part of the cell to another part of the same cell via their axons which is
electrical
Communication between neurons at synapses is
chemical
Neurons communicate with?
other neurons, end organs, and external sensory receptors (brain/afferent neurons)
What happens at the neuron?
- neurotransmitters bind with receptors on the neuron at the dendritic spines 2. Chemical changes inside the spine that are communicated via the dendrite to the cell body 3. if accumulation of signals is sufficiently large cell communicates down the axon to the axon terminals. 4. At the axon terminals cell-specific neurotransmitter released
How does the neuron signal the axon terminals to release neurotransmitter?
Signals come in at the dendrites and are accumulated by the cell body, if accumulation is sub threshold, cell is hyperpolarized and inhibited from signaling, if accumulation is at or above threshold the cell body sends a signal to the axon terminals to release neurotransmitter
What are action potentials?
An electrochemical process that is directly related to the structure of the cell wall and the concentrations of important ions on both sides of the wall
What are the most important voltage sensitive ion channels?
sodium and potassium
At rest voltage sensitive ion channels are?
closed
Identify the normal concentration of sodium and potassium ions.
Sodium is greater on the outside and potassium is greater on the inside of the cells
What happens when a cell depolarizes?
The cell opens and sodium ions rush in, to maintain homeostasis the potassium channels open and potassium ions pour out. The sodium channels close, then the potassium channels close. Then the sodium/potassium pump works to return ion concentrations back to homeostasis. Overall outcome is a wave of signal moving downstream.
What is absolute refractory period?
No signal can cause the neuron to fire both sodium and potassium channels are open
What is relative refractory period?
A larger than normal signal can cause the neuron to fire. Sodium ions begin to close but potassium channels still open.
What happens when the action potential arrives at an axon terminal?
It turns from electric to chemical. A calcium channel opens and calcium motivates vesicles to move toward cell walls. Vesicles bind with the cell wall. Exocytosis of contents of the vesicles, calcium channels close and neuron returns to its resting state.
Communication within a neuron is?
electrical
Communication between neurons is?
chemical
What are circiuts
the networks that coordinate behavior
What are pathways?
Projections or groups of neurons that project between structures that use the same neurotransmitter.
What are the three criteria for being a neurotransmitter?
must be stored in the presynaptic neuron, must be released with depolarization induced by the influx of calcium (in the presynaptic neuron), and it must bind with a specific receptor on the postsynaptic neuron.
What four amino acid neurotransmitters are there?
Glutamate, aspartate, GABA, and Glycine
What are the two subcategories of monoamines?
Catecholamines and Idoleamines
What are the three types of catecholamine neurotransmitters are there?
Dopamine, epinephrine, and norepinephrine
What are the five types of indolamine neurotransmitters are there?
serotonin, melatonin, acetylcholine, histamine, orexin/hypocretin
Which of the amino acid neurotransmitters are excitatory?
Glutamate and asparate
Which of the amino acid neurotransmitters are inhibitory?
GABA and Glycine
Which neuron keeps the brain up and running, and are essential for memory formation, motor skills, plasticity, and mental illness
Glutamate
What happens if there is too much Glutamate?
stroke, nerve cell toxicity
What does GABA do? What happens if there is not enough?
GABA puts the brakes on the brain and not enough GABA can cause seizures. They provide constraint over too much cortical circuitry.
What can increasing GABA treat?
epilepsy, insomnia, pain, anxiety, and the management of mania
Monoamine neurotransmitters have the capacity to
fine-tune and coordinate the response of the major neurons
Which medication groups inhibit the degradation of monoamines therefore causing an increase in monoamines?
MAO inhibitors
When Monoamine Oxidases (which breakdown monoamines) are inhibited an excessive amount of NE is released which can result in?
dangerous elevations in blood pressure (can result in stroke or death)
Why are some foods dangerous in relation to MAO Inhibitors?
Because certain food products and medications enhance the release NE which can exponentially increase the NE already being released by inhibiting MAO.
How do we acquire tyrosine?
It is diet dependent
Describe Catecholamine synthesis.
Tyrosine->Tyrosine hydroxylase-> L-DOPA-> Dopa Decarboxylase-> Dopamine-> Dopamine B-hydroxylase (DBH)-> Norepinephrine-> Phentolamine N-methyltransferase (PNMT)-> Epinephrine
What are the three nuclei that contain the cell bodies that project the three primary branches of the dopamine network?
Substantia nigra, cells of the ventral tegmental area, and the short tracts in the arcuate nucleus of the hypothalamus
What is the Nigrostriatl system or mesotriatal system?
Primary projections from the substantia nigra (located in the ventral midbrain) to the caudate and putamen (or collectively aka striatum)
Parkinsons disease is the result of
loss of dopamine neurons in the substantia nigra
EPS d/t antipsychotic medications causes those symptoms by?
blockading dopamine neurons in the substantia nigra
The mesolimbocortical DA system includes
the ventral tegmental area (ventral midbrain) that project to the nucleus accumbens, prefrontal cortex, amygdala, and hippocampus.
which part of the ventral tegmental area is involved with reward and substance abuse?
accumbens
Which areas of the brain seem to be impaired in patients with ADHD?
Branches to the prefrontal cortex
Current speculation implicates problems with the mesolimbic system with….what in schizophrenia?
positive symptoms
Current speculation implicates problems with the mesocortical system with…what in schizophrenia?
negative symptoms
the tuberoinfundibular dopamine system is…
the short tracts in the arcuate nucleus of the hypothalamus that release dopamine into the portal veins of the pituitary gland.
How does dopamine affect the anterior pituitary
By inhibiting the synthesis and release of prolactin
Any interruption between the DA and the prolactin producing cells will lead to
hyperprolactinemia
Why might antipsychotics cause an increase in prolactin?
Because they block dopamine receptors and dopamine inhibits the release of prolactin
All neurons that produce norepinephrine are called?
noradrenergic neurons
Noradrenergic neurons convert
dopamine to norepinephrine
50% of the NE neurons have their cell bodies located in the
locus coeruleus-small nuclei on each side of the brain stem.
The remainder of NE neurons is found in
loose clusters in the medullary reticular formation
NE system plays an important role in
alertness and anxiety
What is a treatment for medication resistant depression?
Vagus nerve stimulation
A high resting heart rate after an MVA is a predictor of?
later PTSD
Vagus nerve stimulations may work by
regulating the locus coeruleus and the NE system
Because NE is cleared from the synaptic cleft by a reuptake transporter that is also capable of taking up DA…atomoxetine may result in…
an increase in DA as well as NE
Epinephrine plays a much greater role
outside the brain as a hormone, compared with its role as a CNS neurotransmitter
No other neurotransmitter is more closely associated with modern neuropsychopharmacology than…
serotonin
Serotonin is synthesized from
tryptophan an essential amino acid that cannot be synthesized in the body
What are good sources of dietary tryptophan?
grains, meats, and dairy products
What happens to serotonin in the pineal gland?
It is converted into melatonin
Where do serotonin neurons reside in the brain?
the raphe nuclei in the brain stem
Serotonin plays an important role in?
mood, anxiety, and sleep/wake cycle
Blockade of the reuptake of the transmitter with the serotonin transporter results in…
increasing the availability of serotonin in the synaptic cleft which is the therapeutic effect of commonly prescribed anti-depressants.
This neurotransmitter play a prominent role in the peripheral ANS and is the neurotransmitter at the neuromuscular junction.
ACh
ACh in the CNS arise from cell bodies in the
brain stem and forebrain with prominent projections to the cortex and hippocampus
ACh projections to the hippocampus that are involved with learning and memory are disrupted in
Alzheimer’s disease
A recent study found that elderly people taking anticholinergic medications such as Benadryl and TCA’s
had poorer memory, increased brain atrophy, and worse performance on cognitive tests
In the striatum, the ACh neurons balance the
dopaminergic input from the substantia nigra to coordinate extrapyramidal motor control
Disruption of the balance with DA blocking antipsychotic agents can result in
EPS
What medications can be given to restore the ACh/DA balance and restore normal movement in EPS?
anticholinergic agents
Histamine, in the brain, is involved with
arousal and attention
Most of the histamine cell bodies in the brain start in the
tuberomammillary nucleus of the posterior hypothalamus, with sparse but wise spread projections to all regions of the brain and spinal cord
Histamine neurons are quiet when
mammals are sleeping
Unintended sedation may occur with TCAs, clozapine or olanzapine due to
the blocking of the histamine transmission (antihistamines)
When histamine neurons are active
mammals are cognitively and physically alert
What medication indirectly activates the histamine neurons and has been used successfully as a treatment for narcolepsy, excessive sleepiness, and ADHD…
Modafinil
Histamine 3 receptor antagonists are research medications that have the potential to
brighten the brain
What neurotransmitters are similar to histamines?
Orexin/Hypocretin
Where do Orexin/Hypocretin reside?
in the hypothalamus and have projections throughout the brain and spinal cord.
What do Orexin/Hypocretin modulate?
sleep and wakefulness in the opposite direction of histamines.
Orexin/Hypocretin antagonists have been developed and FDA approved for treatment of
insomnia
Neuropeptides are
small chains of amino acids and are considerably larger than the classic neurotransmitters.
Peptides must be transcribed from
mRNA on the ribosomes of the endoplasmic reticulum.
Unlike monoamines, neuropeptides are not recycled by the neuron but rather are
broken down by degradative enzymes (peptidases) on the receptor membrane
Depending on the tissue, synapse, and frequency of stimulation neuropeptides may act as
transmitters, hormones OR modulators
Nitrous Oxide is poorly understood but MAY be involved with
aggression, sexual behavior, and migraine headaches
Endocannabinoids are
the naturally occurring neurotransmitter that activates the cannabinoid (CB1) receptor (the same one marijuana activates)
The cannabinoid receptor is widely expressed
throughout the brain on presynaptic terminals
Endocannabinoids are retrograde messengers that when coupled with CB1 receptor
inhibit the release of the presynaptic neurotransmitter…which reduces neural activity, which causes the calming effect of marijuana
The molecular pony express acting as a sequence of riders, handing on the message to the next specialized molecule, until the message has reached a functional destination, such as gene expression or activation of otherwise sleeping and inactive molecules.
Signal transduction
What is the first messenger of signal transduction?
neurotransmitter
Each molecular site within the transduction cascade of chemical and electrical messages is a potential location
for malfunction associated with a mental illness
