Neurophysiology Review Flashcards by Sarah Gillen

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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What monoamine NTs are derived from tyrosine

Dopamine — binds 2 metabotrobic receptors

Catecholamines: epinephrine and norepinephrine — binds alpha and beta adrenergic receptors

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What monoamine NT is derived from histidine

Histamine — involved in wakefulness, binds H1 and H2 receptors

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What monoamine NT is derived from tryptophan

Serotonin (5-HT)

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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

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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

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Almost all spinal inhibitor reflexes rely on what NT? What type of receptor?

Glycine — ionotropic receptor (chloride)

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Which NT receptor involves calcium influx and is especially active after seizure/stroke/TBI?

NMDA receptor

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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

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2 components of BBB

Tight junctions between capillary endothelial cells

Podocytes from glial cells cover capillaries to reduce surface area

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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)

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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