Flashcards in travers- neuronal structure & signalling Deck (83):
what is the only region of the brain where neurons have been shown to divide?
______ are the major input processes of neurons (respond w/graded potentials)
the ______ of a neuron is the trigger zone for action potentials
where in the neuron are vesicles stored?
axon terminal (for release into the synaptic cleft)
which type of neuron has cell bodies outside the CNS?
afferent neurons (CBO in ganglia)
what type of cell makes up 90% of the CNS?
_______ are the myelinating glia cells in the PNS
________ are the myelinating glia cells in the CNS
PNS- schwann cells
list the functions of Astrocytes:
Regulate extracellular fluid, e.g. remove K+ and neurotransmitters: buffering role
Provide neurons metabolically (e.g. glucose)
Surround brain capillaries: form blood brain barrier
which myelinating glial cell can serve multiple neurons?
what facilitates the Movement of proteins & other material from one part of neuron to another
Microtubules (structural components of axon)
what are the 2 forms of transport through a neuron?
_________ transport occurs from the cell body toward the terminal
what type of motor protein does anterograde transport use?
(similar to myosin contractile proteins)
what motor protein does retrograde transport use?
what is the downside to retrograde transport in neurons?
it can carry viruses (herpes, rabies, polio) toward the neuron body
what virus remains latent in trigeminal ganglion?
Herpes simplex virus type 1
During latency, the herpes simplex virus (type 1) is transcriptionally quiet except for a _________
latency associated transcript (LAT)
characteristics of CNS damage and nerve regeneration:
Damaged CNS neurons do not regenerate
Axons “sprout” but axons do not reach targets
Scar formation prevents surviving axons from reaching targets
when a CNS neuron is damaged, what substance do the astrocytes produce? what does this cause?
Astrocytes make chondroitin sulfate proteoglycans that inhibit neuron growth
what determines the recovery of a PNS injury?
severity of the injury
anterograde degeneration due to severe trauma is also known as "________" degeneration. What does this do to the neuron?
leads to neuron cell death, transganglionic degradation, and transynaptic degradation
what is the nerve response to a less severe injury?
terminal degradation and Chromatolysis
what is Chromatolysis?
the degradation of nissl bodies (granular bodies of rough ER)
associated with protein synthesis
cell body swells, eccentric nucleus
after injury, schwann cells proliferate and produce _______ for substrate for regenerating axons
schwann cells produce ________ which is transported to the ganglion cell body
NGF (neural growth factors)
what is the role of NGF in neuron regeneration?
NGF regulates gene expression and promotes sprouting
the release of NGF will ultimately lead to ________ sprouting
what explains Increased Crossed-midline Sensitivity after the removal of the trigeminal nerve?
there is a negative correlation between ______ and the recovery and function of nerve damage
what is a synapse?
An anatomically specialized junction between a neuron and another cell at which the electrical activity of the presynaptic neuron influences the electrical activity in the postsynaptic cell
what are the types of synapses?
-Chemical vs electrical (also called gap junctions, rare in CNS)
-Excitatory vs inhibitory
name the 3 types of chemical synapses
what is the difference between temporal summation and spatial summation?
Temporal summation: adding together of PSP’s from one synaptic contact (over time)
Spatial summation: adding together of PSP’s produced by different synapses
a classical neurotransmitter can:
Functions in rapid communication (msec)
Act on postsynaptic cell to produce EPSP or IPSP
____________ are often co-released with neurotransmitters
what is the role of neuromodulators?
May act postsynaptically to amplify or dampen on-going synaptic activity
May act on pre-synaptic cell to alter synthesis, release, uptake or metabolism of neurotransmitters
Actions can involve changes in DNA/protein synthesis or enzyme activity: can thus be much slower in action (min – days)
how is acetylcholine synthesized?
Synthesized from choline and acetyl Co-enzyme A by choline acetyltransferase in synaptic terminal
examples of neurons that release ACh:
Neurons in nucleus basalis and pons
All preganglionic neurons (sympathetic & parasympathetic)
All postganglionic parasympathetic neurons
what are the 2 main regions of the CNS that release ACh? what is the role of these 2 regions?
-Basal forebrain (cognitive function)
-Pontine nuclei (sleep regulation)
what are the types of ACh receptors? where are they found?
-Muscarinic receptors: Mostly found in CNS
-Nicotinic receptors: Relatively few in central nervous system
which ACh receptor triggers G protein that open or close ion channels?
how do nicotinic receptors cause changes in the postsynaptic cell?
ACh binding opens ion channel within receptor
Channel permeable to Na+ and K+, therefore depolarizing
_________ is an autoimmune disorder in which individual makes antibodies to nicotinic receptors
how is myasthenia gravis treated?
Treated with acetylcholinisterase inhibitors
which ACh receptor disorder is the most common form of dementia?
what are Biogenic Amines synthesized from?
what are the 3 bionegic amines that are classified as Catecholamines? what amino acid are they produced from?
dopamine, norepinephrine, epinephrine
-Synthesized from the amino acid tyrosine
describe the life cycle of catecholamines:
1) Synthesis- Presynaptic terminal
-Stored in vesicles
2) Release- Ca++ dependent
3) Termination of action
a. presynaptic neuron re-uptake
______ is a common molecule that can breakdown catecholamines
T/F: Receptors for catecholamines are almost exclusively G-protein coupled receptors
Catecholamines are associated with what neurological diseases?
Parkinsons’s disease, depression, schizophrenia
what are the 2 structures of the CNS that produce dopamine?
Ventral tegmental area
the ventral tegmental area associated with ________ and _________
reward and addiction
the substantia nigra is associated with the ______ system
there are ______ dopamine receptor subtypes. All are G-protein coupled
what is the main effect from activation of D1 (dopamine 1) receptors? D2?
D1: activate adenylate cyclase
D2: inhibit adenylate cyclase (leading to hyperpolarization)
what condition is often associated with the D2 receptors of patients receiving dopamine blocking drugs?
T/F: Norepinerphrine requires presence of additional enzymes for synthesis from Epinephrine
Epinerphrine requires presence of additional enzymes for synthesis from norepinephrine
NE neurons include:
Sympathetic postganglionic neurons (and some CNS)
Epinephrin neurons include:
Adrenal gland (medulla) as circulating hormone (not much in CNS)
catacholamine and other biogenic amine receptors are almost all _________ coupled
what are the 2 different types of alpha NE receptors? what is their function?
α1 (intracellular release Ca++): excitatory
α2 inhibitory via opening K+ channels or blocking Ca
how do beta NE receptors function?
beta receptors: (ß1, ß2 ,ß3): open Ca++ channels
NE can have very different effect on tissue depending on what?
the receptor type (alpha 1 or 2, beta)
what regions of the CNS use Norepinephrin?
Locus ceruleus- attention/sleep
Other brainstem groups- Autonomic & homeostatic functions
Serotonin is involved with which CNS structures? what is the role of these structures?
Rostal raphe nuclei
-Sleep, mood, homeostatic function
Caudal raphe nuclei
T/F: serotonin is involved in many functions ranging from sensorimotor systems to cognitive function
Histamine is derived from amino acid ______
histamine is involved in the control of _____________ cycles in the CNS
what are the "Excitatory Amino Acids"?
glutamate & aspartate
Glutamate: most common excitatory neurotransmitter
Glutamate & aspartate bind to several classes of _________receptors
Amino acid neurotransmitter receptors are also a class of _________ receptors, which are g-protien coupled
the N-methyl-D-aspartate (NMDA) receptors are the Synaptic mechanism of _______________
Long term potentiation
-functions that last (memory formation, chronic pain)
what factors promote long term potentiation?
- Phosphorylation of NMDA receptor (removal of Mg+ block)
- Calcium entry into cell via NMDA receptor
what is the Major inhibitory neurotransmitter in CNS?
GABA (gamma-amminobutyric acid)
GABA is a modified form of what?
What type of receptor is GABAa? what effect does it have? what about GABAb?
GABAA : ionotropic receptor
----opens Cl- channel
GABAB receptor: metabotropic receptor
----opens K+ channels
what disease is linked to a GABA deficiency?
characteristics of glycine:
Amino Acid neurotransmitter
A) Inhibitory neurotransmitter (mostly spinal cord)
B) Receptor opens Cl- channels
C) Blocked by strychnine
________ function as neuromodulators
(hint: they are formed by the linking of 2 base units)
what is the only gaseous neurotransmitter? what are its effects?
Nitric oxide (NO)
Can modulate neurotransmitter release, e.g. glutamate & GABA
the neurotransmitter ______ is usually excitatory, and is co-released with other classical neurotransmitters