Neurophysiology Flashcards
Free nerve endings contain receptors for what sensations?
Pain, temperature, crude touch
Anomic aphasia is usually caused by damage to which area of the brain?
Angular Gyrus
Nonfluent aphasia such as in Pick’s Disease is caused by a lesion in which brain area?
Broca’s area
Fluent aphasia is caused by a lesion in which brain area?
Wernicke’s Area
Memory loss can be a result of a lesion in which brain area?
Hippocampus
Concentration of glucose and protein in CSF is higher, lower, or same as plasma
Lower (both glucose and protein)
Part of the cerebellum connected to the vestibular nuclei, and is associated with central vertigo
Flocculonodular Lobe
What frequencies of sound produce vibration of the basilar membrane at the base of the cochlea (near oval and round window)
High frequency
What frequencies of sound produce vibration of the basilar membrane at the apex of the cochlea (near helicotrema)
Low frequency
What percentage of the human genome is involved in the formation and function of the nervous system?
40%
Electrical vs chemical synapse
Electrical - by gap junctions, two way
Chemical - neurotransmitter and receptor at synapse, one way only
Two internal structures in the presynaptic terminal and their function
Transmitter vesicles - contain neurotransmitter
mitochondria - provide ATP for neurotransmitter generation
Events that lead to neurotransmitter release from presynaptic terminals
- Action potential depolarizess presynaptic terminal
- Voltage Gated Calcium channel opens,making calcium enter terminal
- Calcium causes release of neurotransmitters from vessels by binding to release sites
Two actions of neurotransmitter in the postsynaptic neuron
- Gating Ion Channels
2. Activating second messengers
Logic behind ion channels
Differentiate cation channel and anion channel
Neurotransmitter opens ion channel, (diameter large enough for ions to pass) closes when substance is no longer present
Cation channels are lined with negative charge, which attracts + carge sodium, potassum etc,
Anion channels are lined with positive charge, attracting negative charge (chloride, etc)
Ion channels provide rapid or prolonged neuronal control?
Rapid
Second messengers provide rapid or prolonged control
Prolonged
Components of the inactive G protein
GDP, alpha beta and gamma component
Which component of the G protein is the activator
Alpha
Mechanism of acivation of G protein
- Neurotransmitter activates receptor
- Conformational change exposes G protein binding site
- G protein binds
- Alpha subunit releases GDP and binds GTP
- A-GTP complex dissociates from beta and gamma
- A-GTP performs its function
- GTP is hydrolyzed to GDP, releasing it from target protein and binding it back to B and Y
Role of sodium, potassium, and chloride channels in postsynaptic membrane
Sodium channels allow Na entry to postsynaptic cell, increasing membrane potential - excitation
Potassium channels allow exit of K on postsynaptic cell, decreasing membrane potential - inhibition
Chloride channels allow chloride entry into the cell, decreasing membrane potential - inhibition
Rapidly acting neurotransmitters vs neuropeptide
Rapidly acting is small, vesicles reusable
Neuropeptides are large and long acting, vesicles unreusable, autolyzed after release
Mechanism of recycling of vesicles in presynaptic cells
- Vesicle fuses with membrane to release neurotransmitter
- Vesicle invaginates back to the terminal, forming new vesicle
- New vesicle synthesizes new transmitters
Enzyme responsible for synthesizing acetylcholine
Choline acetyltransferase
Components of acetylcholine
AcetylCoA + choline
Enzyme which splits acetylcholine in the synaptic cleft
Cholinesterase
What happens to choline at the synaptic cleft
Actively transported back to presynaptic terminal to be used for synthesis of new acetylcholine
Which of the ff are inhibitory, excitatory, or both?
Acetylcholine, Norepinephrine, Dopamine, Glycine, GABA,Glutamate, Serotonin
Inhibitory - dopamine, glycine, gaba, serotonin (pain and higher cortex)
Excitatory - glutamate
Both - acetylcholine (excitatory except in vagus), norepinephrine,
Neurotransmitter not stored in vesicles in the presynaptic terminal and freely diffuses from presynaptic to postsynaptic cell
Nitric oxide
Mechasnism of neuropeptide release
Synthesis in ribosome, transport to ER and Golgi,packaged into transmitter vesicle, action potential releases transmitter and autolyzes vesicles
What is excitatory post synaptic potential and inhibnitory post synaptic potential and principle behind it
increase or decrease in resting membrane potential after synaptic excitation
What is the principle of summation in excitation of neurons
Sucessive excitation of synapses increase EPSP to the threshold potential, thus eliciting action potential in the postsynaptic neuron
In which part of the postsynaptic neuron is action potential first generated
Beggining part of axon (higher concentration of sodium channels than soma)
Neurotransmitter involved in presynaptic inhibition and mechanism
GABA - opens anion channels, causing chloride influx which cancels excitatory effect of sodium
Mechanics of spatial and temporal summation
Spatial summation - multiple synapses in a soma are charged simultaneously
Temporal summation - one synapse charged consecutively, before effect of previous impulse fades
Mechanics of decremental conduction and its implications in location of synapses along a dendrite?
Membrane potential decreases as it moves along the dendrite due to leaky membranes
Synapses closer to soma have more effect in excitation or inhibition
TRUE OR FALSE - Excitatory synapses can infinitely be stimulated
FALSE. Principle of fatigue of synaptic transmission as a protective factor for overexcitation, such as seizure (ubos neurotransmitter, activate inhibitors, ion concentration changes, etc)
Effect of acidosis and alkalosis on synaptic transmission
Acidosis - depresses neuronal activity
Alkalosis excites activity
(Think H+ makes outside more positive, potential decrease, similar to K+ exit)
(bicarb is negative, does opposite)
Effect of hypoxia on synaptic transmission
Inhibitory. Synaptic transmission is highly dependent on O2, which is why HIE happens if panget sats
Effect of strychnine on neuron excitability and mechanism of action
Excitatory by inhibiting inhibitory neurotransmitters
5 basic types of sensory receptors
Mechanoreceptors - compression and stretch Thermoreceptors Nociceptors - pain Electromagnetic receptors - retina Chemoreceptors
What is differential sensitivity
Each receptor is highly sensitive to what it is designed to perceive, and almost unresponsive to other stimuli
What is the Labeled Line principle regarding modalities of sensation
Each nerve fiber follows a specific tract and terminates at the center (ex, pain center, vision center), thus only one modality of sensation is transmitted by electical impule of nerve fiber
Mechanism of tonic receptors and give examples
Slowly adapting receptors,
ex muscle spindle, vestibular system,pain receptor, arterial baroreceptors, chemoreceptor of carotid
Mechanism of phasic receptors and give examples
Rapid reaction to change in stimulus strength, but quickly adapts
ex: pacinian corpuscle - when sitting down, no impulse even if may pressure sa pwet
Type A vs Type C fibers
A - large and medium sized myelinated fibers of spinal nerves
C fibers - small unmyelinated low velocity sensory fibers and postganglionic autonomic fibers
The A-alpha fibers are divided into Group 1a and 1b. Differentiate the two
1a -a annulospiral ending of muscle spindle
1b - golgi tendon organ fibers
What are A-beta and A-gamma fibers, also known as Group II?
Fibers from most discrete cutaneous tactile receptors and flower-spray ending of muscle spindle
What are A-delta fibers, also known as Group III?
Fibers carrying temperature, crude touch, and prickling pain
What are C fibers, also known as Group IV
Unmyelinated fibers carrying pain, itch, temperature, and crude touch
Meissner’s corpuscle is an elongated encapsulated nerve ending of type ____ fiber
A-beta
Function of Meissner’s corpuscle
Sensitive to movement of objects and low frequency vibration - rapidly adapting
Function of Merkel’s disc
Continuous touch sensation
Hair contains touch receptors? TRUE OR FALSE?
TRUE - the hair end organ
Function of ruffini endings
Slowly adapting - for signaling deformation like heavy prolonged touch and pressure
Function of pacinian corpuscle
Detection of pressure and vibration
What fiber transmits tactile signals in peripheral nerves?
A-beta - most specialized receptors - for rapid transmission and localization/sensitivity
A-delta and C fiber - free nerve endings - cruder signals, poorly localized
Pruritus is sensed by the brain through stimulation of what fiber
C fiber
Logic behind scratching when itchy?
Removes irritant,or causes pain which supresses itch signals by lateral inhibition
Stimuli which excite pain receptors
Mechanical, thermal, and chemical
Chemicals which excite chemical pain receptors
Bradykinin, serotonin, histamine, K, acids, acetylcholine, proteolytic enzymes
Chemicals which enhance sensitivity of pain endings but do not directly excite them.
Prostaglandin, Substance P
TRUE OR FALSE - Pain receptors exhibit adaptibility?
FALSE. Isipin mo pain is warning taht something is wrong. correct first
TRUE OR FALSE - Pain intensity is associated with rate of damage of tissue and total damage done to tissue?
FALSE. Think burns
Temperature at which tissues begin to be damaged by heat, also temp when average person begins to perceive pain?
45 deg C
Fast vs Slow pain fibers in terms of
A. Fiber used
B.eliciting factor
Fast pain is transmitted by A-delta fibers from mechanoreceptors and thermoreceptors
Slow pain is transmitted by C fibers, usually from chemoreceptors
Neurotransmitter secreted by A-delta nerve fiber endings in the spinal cord
Glutamate
Termination of C fibers in the spinal cord
Substantia gelatinosa (Laminae II and III)
Termination of A-delta fiber in the spinal cord
Lamina I
Neurotransmitter secreted by C nerve fiber ending involved in slow chronic pain
Substance P
Neurotransmitters involved in analgesia system of brain
Enkephalin and serotonin
Nerve fiber which transmits visceral pain?
C fibers
Parietal pain vs Visceral pain
Visceral pain is dull, aching, poorly localized
Parietal pain is sharp, localizing
Special spinal cord tract where thermal signals enter in the spinal cord
Tract of Lissauer
Definiton of diopter
1 meter / focal length of lens
Arrange by increasing index of refraction
Air, Cornea, aqueous, Lens, Vitreous
Air 1 Aqueous humor 1.33 Vitreous hunor 1.34 Cornea 1.38 Lens 1.4(ave)
Two thirds of refractive power of eye is supplied by what?
Cornea
Muscle responsible for accomodation
Ciliary Muscle
Layers of the Retina
Outside to inside
- Pigmented layer
- Rods and cones
- Outer nuclear layer (of rods and cones)
- Outer plexiform layer
- Inner nuclear layer
- Inner plexiform layer
- Ganglionic layer
- Layer of optic nerve fibers
- Inner limiting membrane
Central fovea is composed almost entirely of (rods/cones/both)?
Cones
Light sensitive photochemical in rods and cones
Rods - rhodopsin
Cones - “color pigments”
Histology of outer segment of rod and cone vs inner segment
Large number of discs, infolded cell membrane with pigment proteins as transmembrane proteins.
Inner segmebt - organelles
Pigment contained in pigment layer of retina and function
Melanin - black pigment which prevents light reflection in globe, allowing contrast
Storage location of vitamin A in retina
Pigment layer
Rhodopsin is a combination of which two molecules
Scotopsin and 11-cis retinal
What happens when light energy is absorbed by rhodopsin
11-cis retinal changes to all-trans retinal, which is unstable and splits from scotopsin
Pathway: rhodopsin - bathorhodopsin - lumirhodopsin - metarhodopsin I - metarhodopsin II - all trans retinal & scotopsin
It is also called activated rhodopsin. This molecule excites electrical changes in rods and transmit visual image
Metarhodopsin II
Reconversion of rhodopsin from all-trans to cis is catalyzed by what enzyme
Retinal isomerase
Form of vitamin A which can be used to replenish 11-cis retinal and pathway involved
All-trans retinol
All trans retinal – all trans retinol (isomerase) – 11-cis retinol – 11cis retinal
Severe vitamin A deficiency can cause what opthalmologic problem and pathophysio
Nyctalopia (night blindness)
Decreased retinal and rhodopsin
Most sensory receptors are depolarized when exposed to stimulus. Which receptor is hyperpolarized when exposed?
Rods
Sodium channel in outer surface of rod is gated by?
cGMP
G protein stimulated by activated rhodopsin which is involved in hyperpolarization
Transducin
Physiology of ions in the rod at the dark state
Inner membrane Na K pump pumps Na out and K in
Inner membrane K leaks out in nongated K channels
Outer membrane Na leaks in cGMP gated channel
Normal electronegativity in cell is -40mV
How does light hyperpolarize the rod?
- Rhodopsin is activated by light forming metarhodopsin II
- Activated rhodopsin stimulates transducin, a g protein
- Transducin activates cGMP phosphodiesterase, which catalyzes breakdown of cGMP
- Reduced cGMP closes Na channels
- Continued Na K pump pumping makes inside of cell lose Na, hyperpolarizing it
- Rhodopsin kinase inactivates the activated rhodopsin and ion flow reverts to normal
Enzyme which inactivates the activated rhodopsin
Rhodopsin kinase
Difference in structure of pigment in cones vs rods
In cones, retinal is the same as in rods, but scotopsin structure is different depending on pigment. (Photopsins)
How many color pigments are present in a cone?
1
Wavelength of peak light sensitivity for RGB
Blue - 445 nm
Green - 535 nm
Red - 570 nm
Wavelength of peak light sensitivity for rhodopsin
505 nm
Rods vs cones in dark adaptation
Cones adapt faster, rods are more sensitive
Loss of red cones is called
Protanopia
Loss of green cones is called
Deuteranope
Retinal cells which transmit signals horizontally in the outer plexiform layer from rods/cones to bipolar cells
Horizontal cells
Retinal cells which transmit signals vertically from rods cones and horizontal cells to the inner plexiform layer
Bipolar cells
Cells which transmit signals from bipolar cells to ganglion cells
Amacrine cells
Cells which transmit output signals from retina to the brain
Ganglion cells
Retinal cell which transmits inhibitory signals retrograde from inner plexiform to outer plexiform
Interplexiform cell
Retinal cells which transmit signals horizontally
Horizontal and amacrine cells
Direct visual pathway in rod vs cone
Rod - bipolar - amacrine - ganglion
Cone - bipolar - ganglion
Neurotransmitter in synapse bet rod or cone and bipolar cell
Glutamate
TRUE OR FALSE Transmission of most signals in the retina is by action potentials
FALSE. Electronic conduction since stimulus hyperpolarizes. This allows graded conduction depending on light intensity
Cells involved in lateral inhibition and purpose?
Horizontal cells - allows contrast
Attenuation reflex in middle ear mechanism
Tensor tynpani pulls malleus inward
Stapedius pulls stapes outward
Reduces intensity to protect cochlea
Nicotinic receptor blocker at the ganglia but not at the NMJ
Hexamethonium