Neurophysiology Review Flashcards
T/F: L-dopa is produced when dopamine is broken down by neurons
False
L-dopa is produced from tyrosine and then converted to dopamine
Clinical relevance: Parkinson disease/mood/affect/emotional experience; binds 2 metabotropic receptors
T/F: the circumventricular organs are characterized by the absence of glial endfeet surrounding the cerebral capillaries
True
The circumventricular organs are regions where the BBB is “incomplete”. Tight junctions between capillary endothelial cells are not present
These regions all require exposure to plasma constituents to do their job — area postrema (vomiting), OVLT and SFO (ADH release), posterior pituitary (ADH and oxytocin release)
These areas are also more sensitive to damage d/t toxins in the blood, and drugs will cross into these regions
T/F: influx of calcium into a neuron can elicit apoptosis in a susceptible neuron
True
Calcium influx via the NMDA receptor initiates apoptosis in any cell receiving synaptic input from the overactive cell, even if the cell isn’t impacted by the original insult
T/F: full consciousness is produced by the release of ACh and glutamate (EAA) from medullary and pontine regions
False
These systems are sufficient to be considered “awake”, but full awareness/consciousness requires serotonergic, noradrenergic, and dopaminergic signaling as well
T/F: P-glycoprotein is required for the movement of glucose from the plasma into the CSF
False
Glucose requires a specific transporter (GLUT1) that is insulin inependent
P-glycoprotein is responsible for moving many drugs or other substances from the CSF to the blood
T/F: the ability to recognize an object by feel alone (stereognosis) is completed in somatosensory cortex 1
False
This is done by S2 which also is able to compare 2 objects and ties to memory
T/F: damage to the insular cortex abolishes the ability to feel pain
False
The insular cortex coordinates autonomic responses. Damage produces asymbolia - painful inputs are recognized as painful, but not perceived as unpleasant
T/F: damage to the dorsal visual pathway impairs the ability to use visual info in motor actions
True
The dorsal visual pathway involves the use of visual information in motion while the venral visual pathway involves higher cognitive processing using visual info (naming objects, etc…)
Because of the 2 pathways, the ability to name an object can be divorced from the ability to copy the object
T/F: activation of the saccule will give rise to the sensation of falling forward
False
The utricle senses horizontal linear acceleration, while the saccule senses vertical linear acceleration.
Falling forward is sensed by the anterior semicircular canals! Falling backward would be the posterior canals, and turning in circles would be horizontal canals
T/F: Spasticity results from increased gamma-motor neuron activity in the muscle spindle
True
Spasticity results from damage to the cortical regions that activate the brainstem inhibitory area, which usually inhibits gamma motoneurons. Thus if this area is damaged, there will be un-inhibited gamma-motorneuron activity in the muscle spindle
What creates and maintains the membrane potential?
Created by Na/K ATPase (3 sodium out for every 2 potassium in)
Maintained by the selective permeability of the membrane via K+ leak channels and ClC1 chloride channel
The source of myelin is different in central vs. peripheral neurons.
____ provide myelination in CNS while _______ provide mylination in the PNS
Oligodendrocytes = central
Schwann cells = peripheral
Release of NT onto a postsynaptic cell results in different actions depending on if it is ionotropic or metabotropic
If it is ionotropic, and the signal is _____ or ______ -the cell depolarizes and an EPSP occurs
If it is ionotropic, and the signal is _____ or ______ -the cell hyperpolarizes and an IPSP occurs
Calcium; sodium
Chloride; potassium
Release of NT onto a postsynaptic cell results in different actions depending on if it is ionotropic or metabotropic
What are some examples of types of G proteins that impact intracellular response?
Gs = stimulation of AC activity
Gi = inhibition of AC activity
Gq = activation of IP3/DAG
What monoamine NTs are derived from tyrosine
Dopamine — binds 2 metabotrobic receptors
Catecholamines: epinephrine and norepinephrine — binds alpha and beta adrenergic receptors
What monoamine NT is derived from histidine
Histamine — involved in wakefulness, binds H1 and H2 receptors
What monoamine NT is derived from tryptophan
Serotonin (5-HT)
Serotonin (5HT) binds multiple receptor subtypes. Most are metabotropic, but one is ionotropic. What is the significance of the ionotropic receptor for serotonin — what is the physiologic response?
The ionotropic receptor is found in area postrema and triggers vomiting
GABA is an inhibitory NT involving chloride entrance into the cell. It binds 2 receptors, GABA-A which is ______ and GABA-B which is ______
Ionotropic; metabotropic
Almost all spinal inhibitor reflexes rely on what NT? What type of receptor?
Glycine — ionotropic receptor (chloride)
Which NT receptor involves calcium influx and is especially active after seizure/stroke/TBI?
NMDA receptor
The CSF in the CNS is produced by the ___ ____ and membranes lining the ventricles
Describe its content in comparison to plasma
Choroid plexus
Low protein, glucose, and K content relative to blood
Mg content higher than plasma
2 components of BBB
Tight junctions between capillary endothelial cells
Podocytes from glial cells cover capillaries to reduce surface area
What happens to cerebral blood flow if systemic BP goes too high?
Activation of alpha-adrenergic receptors on cerebral vasculature
Vasoconstriction
Prevents high BP from damaging capillaries (where BBB is — so protects the BBB as much as possible)
What happens if cerebral blood flow is compromised?
Brain will activate pressor regions in the medulla, driving systemic pressure up to force blood through to the brain
The vasculature in the brain is innervated with ______, meaning if the vasculature is distended, torqued, or twisted, _____ is perceived
Nociceptors; pain
What effect do intracranial bleeds have on BP?
Increased intracranial pressure can lead to tremendous increases in systemic BP as the brain tries to maintain perfusion
To be considered “awake” what 2 components are required?
Medullary RAS and parabrachial nuclei (glutamate)
Pedunculopontine tegmental nucleus and laterodorsal n. (ACh)
Differentiate S1 from S2 in sensory processing
S1 = initial processing - identify characteristics of what activated receptors
S2 = stereognosis (ability to recognize an unseen object by touch); comparing 2 objects
Role of PTO in sensory processing
Association cortex; involved in naming objects
Nociception involves slightly myelinated _____ fibers, or unmyelinated ____fibers
The peripheral ending can be activated by numerous chemicals, including ____ and _____ - leading to increased amount of pain perceived
A delta; C
Bradykinin; substance P
Spinal processing is different for A vs C pain fibers
_____ path is likely for fast/sharp pain via A delta fibers
_____ path islikely for slow/dull pain via C fibers
Spinothalamic
Spinoreticulothalamic
The spinoreticulothalamic path for C type pain is important because there is a synapse in the spinal cord at the level where the afferent enters the spinal cord
This synapse is where what 2 events happen?
The gating mechanism — non-nociceptive input from a-beta fibers (cutaneous) inhibits painful inputs via presynaptic inhibition
Descendign opioid inputs via the raphe nuclei also act to decrease transmission at this synapse
What causes chronic, or neuropathic, pain?
Changes in periphery leading to sensitization of the nociceptors themselves, or changes in spinal cord sensitivity to nociceptive input
In terms of focusing image onto the retina, the ____ involves the most refraction of light while the ____ has variable refraction
Cornea
Lens
[more round lens/more bending = close vision; flatter lens/less bending = far vision]
Condition characterized by cloudiness in the lens interfering with light passage
Cataract
Condition characterized by inability to change the shape of the lens (stiffness or inflexibility)
Presbyopia
The mechanism of photoreceptors involve light hitting the photoreceptor, causing it to hyperpolarize, reducing ____ release
Glutamate
Disruptions in the _____ ___ ____ disrupt the ability of the eyes to move together; also involved in focus, detection of motion, and initial processing
Lateral geniculate body
Significance of primary visual cortex
Initial processing; columns devoted to orientation of the lines in the visual field
Job is to create a contour map of the visual field
Blobs involved in initial color processing
What do V2 and V4 do in visual processing?
V2 = depth perception
V4 = color perception
Endolymph vs. perilymph contents
Endolymph surrounds hair cells; high in K+, low in Na+
Perilymph is similar to plasma/ECF; high in Na+, low in K+
Basilar membrane vs tectorial membrane
Hair cells arise from organ of Corti in basilar membrane; basilar membrane bends based on wavelength of sound. High pitched sounds cause maximal bending close to oval window; low pitched sounds cause maximal bending at helicotrema
Tip of hair cells insert into tectorial membrane
Pathway of sound to the brain
Superior olive (localization of sound source) — medial detects intraural time differences; lateral detects intraural volume differences
Inferior colliculus suppresses info from echoes
Superior colliculus creates 3D map of where sound is
Primary auditory cortex creates tonotopic map of sound, loudness, etc
Auditory association cortex makes complex map of sound, including harmonies, etc.
Myotatic refex vs. GTO reflex
Myotatic reflex occurs when stretching of muscle spindle leads to contraction of stretched muscle
GTO reflex occurs when too much force is placed on contracting muscle so that strong inhibition stops contraction
Role of primary motor cortex and supplementary and premotor cortex in voluntary motion
Primary motor cortex = relay the desired action to the lower motoneurons to activate the muscles
Supplementary and premotor cortex = planning of motions, postural control
Role of parts of the cerebellum in voluntary motion
Spinocerebellum: medial is postural control, lateral is to correct ongoing motion
Cerebrocerebellum involves planning of complex motion; motor memory
Vestibulocerebellum is eye movements/postural movements for future motions
Contractile cells of BBB
Pericytes
Role of Na/K/2Cl transport in BBB
Transports ions from CSF to blood
Expression tied to endothelin 1 and 3
Endothelin production tied to astrocyte signals
Role of P-glycoprotein in BBB transport
Moves drugs that don’t belong that crossed BBB back into blood
The NMDA receptor is an ionotropic receptor activated by exogenous N-methyl-D-aspartate. It is also activated by _____ and ______. When activated, it allows _____ influx
Glutamate; aspartate; Ca
_____ serves as a coagonist at the NMDA receptor and is required for EAA to have an effect, but on its own cannot open the channel
Glycine
Role of Mg in NMDA receptor
Mg binds inside the channel, blocking it
To open the channel, Mg must leave; depolarization forces Mg out of the channel
[PCP binding site is inside the channel, internal to Mg binding site, and blocks the channel]
Increased intracellular Ca following NMDAR activation results in what 4 events?
Activation of phospholipase A2 — release of arachidonate from membrane and physical damage to membrane; arachidonate acts at ryanodine receptor on ER releasing more Ca from intracellular stores causing unfolded protein response, activation of eIF2a-kinase, impaired mitochondrial function
Activation of calcineurin (phosphatase) - activates NOS, increases NO synthesis
Activation of Mu-calpain (protease) - proteolysis — spectrin, eIF4G, metabolic impairment
Activation of apoptotic pathway - cytochrome C and caspase 9
Location of NT: dopamine
Substantia nigra, ventral tegmental area
Location of NT: EAA
Dorsal and ventral pathways (to cortex)
Location of NT: NE
Locus coeruleus
Location of NT: serotonin
Raphe nuclei
Location of NT: ACh
Pedunculopontine tegmental and laterodorsal nuclei
Location of NT: histamine
Tuberomammilary nucleus of the hypothalamus
Which division of the motor cortex determines whether it’s okay to move and identifies the goal and motion required to meet that goal?
Premotor cortex
Which division of the motor cortex exerts postural control, identifies the specific motor sequence required and plans the motion, changing tactics if necessary?
Supplementary motor cortex
Which division of the motor cortex codes the individual motions required to reach the goal and activate the muscles?
Primary motor cortex
The ______ receives input from nearly all of the cerebral cortex and transmits it to the basal ganglia. The output from the basal ganglia (GPi and SNpr) is inhibitory and projects to motor areas in the brainstem and thalamus (releases_____)
Striatum; GABA
Result of damage to any basal ganglia structure
Slowness of voluntary movement, involuntary movements, involuntary posutres, or a combination of these
Result of damage to SNpc in basal ganglia
Tremor at rest, slowness of movement, rigidity, and postural instability (main features of parkinsons)
Components of basal ganglia
Striatum (caudate + putamen) — output inhibitory
Globus pallidus (external segment+internal segment)
Substantia nigra (pars compacta+pars reticulata) — dopaminergic; stimulates D1(+) and D2(-) receptors
Subthalamic nucleus — input from frontal lobe, output excitatory to other BG nuclei, kept under tonic inhibition by Gpe
Compare/contrast direct pathway vs indirect pathway via basal ganglia
Normally direct pathway allows motion and indirect pathway prevents motion
What happens in basal ganglia with huntington disease?
Indirect pathway is abolished, resulting in excess movement
Loss of ACh tone causes this
Noxious stimuli is sensed by TRP receptors, which are ligand-gated non-selective cation channels permeable to Ca, Na, and/or K
What are the following channels for: TRPV1, TRPA1, TRPM8?
TRPV1 — capsaicin, heat
TRPA1 — mustard, cool
TRPM8 — menthol, cool
4 regions of the brain in which tight junctions are absent (i.e., not included in BBB)
OVLT
SFO
Posterior pituitary
Area postrema
