Neuro LOs

Be able to explain how electrodes can be used to study electrical signals in neurons.

A stimulation electrode is used to inject CURRENT, while a recording electrode detects the VOLTAGE

Name the 3 most important types of CNS glia and how their major functions differ

Astrocytes: aid in neurongenesis, transmission of signals, support, nourishment, protection, etc. Oligodendrocytes: myelinate axons to speed conductance NG2 glia: form synaptic connections with neurons

Be able to explain how an electrochemical equilibrium forms across membranes.

At electrochemical equilibrium, there is no net ion flow. This can be acheived when no ion channels are open other than the potassium leak channels.

Give examples of the main excitatory and inhibitory neurotransmitters at the neuromuscular junction (in vertebrates) and in the central nervous system

Acetylcholine - excitatory, present in CNS Glutamate - main excitatory neurotransmitter in CNS GABA - mai inhibitory neurotransmitter in CNS Biogenic amines - include dopamine, norepinephrine, epinephrine, serotonin, etc. Found in specific CNS and PNS systems

Explain and be able to identify excitatory and inhibitory synapses

If the reversal potential is higher than the threshhold potential, a synapse is excitatory. If it is lower, the synapse is inhibitory

Know when and how to apply the Goldman Equation

Use when looking at the concentration differences/membrane permeability of sepcific ions. Can be used to see how specific changes to ion concentration would impact overall membrane potential

Be able to use and apply Ohm's law.

Use when looking at the relationship between voltage and resistance (1/conductance)

electrical response characteristics of olfactory receptor neurons

each neuron has a specific response pattern for a molecule, creating a response mosaic for each odorant ex. Odorant X causes high response in neurons A and B with low response in neuron C, while Odorant Y causes high response in neurons B and C with low response in neuron A.

explain the activity dependence of synaptic connections

the amount of activity at a synapse determines whether the neuron is pruned or remains

Identify the 6 major functions of astrocytes

- Neurongenesis - Homeostasis - Structure - Blood brain barrier - Metabolic support - Synaptic transmission

Describe the functional steps of the synaptic vesicle cycle.

1. Transmitter synthesized into vesicles 2. Action potential rushes into postsynaptic terminal, depolarizing the membrane and opening Ca++ channels 3. Ca++ flows into cell and fuses vesicles with membrane, allowing neurotransmitter to release into synaptic cleft 4. Neurotransmitter binds to postsynaptic receptor molecules, triggering the opening/closing of ion channels 5. EPSP/IPSP 6. Glial uptake or enzyme degradation of leftover neurotransmitter - some parts may be recycled 7. Vesicular membrane removal

Explain how a cochlear implant works

A microphone outside the ear sends a signal down a wire to an electrode sitting in the scala tympani, which then stimulates the auditory nerve

Describe the differences between NMDA and AMPA receptors.

AMPA receptors are only permeable to Na+ and K+ and must be activated for NMDA receptors to function NMDA receptors are permeable to Na+, K+, and Ca++

Describe the functional and structural characteristics of Acetylcholine, Glutamate, and GABA receptors.

Acetylcholine: neurotransmitter synthesized from acetyl-coA and choline and is transported in vesicles. Leftover neurotransmitter is broken down by acetylcholinesterase, choline is then recycled Glutamate: Synthesized in breakdown of glutamine in synapse, transported in vesicles, and binds to receptors. Leftover glutamate is used to create more glutamine in glia, which is then taken back into synapse. GABA: large extracellular component, functions as a chloride channel to hyperpolarize cell, and serves as receptor site for many depressant drugs. Structurally otherwise similar to acetylcholine receptor

Explain the afferent and efferent projections in the cochlea corresponding to mechanoelectrical transduction within hair cells by shear forces btw cochlear membranes

Afferent - inner hair cells, responsible for mediating actual hearing and sending auditory input to brain Efferent - outer hair cells, amplify sound by enhancing the shear force on the basilar membrane when tugged on by the tectorial membrane

Explain the reversal potential of synaptic transmitter receptors and the significance of the reversal potential.

At the reversal potential of a neurotransmitter receptor, a given neurotransmitter will cause no net flow of ions through that receptor's channel. If this potential is below the threshhold potential, depolarizing postsynaptic currents will be inhibitory.

Be able to explain what happens in regards to currents and ion channel states at the threshold of an action potential

At the threshold of an action potential, a depolarizing current is generated, triggering more and more voltage gated sodium channels to open.

Know what properties allow microglia to have immune system functions

Blood brain barrier: Formed by glia and endothelial cells to prevent pathogens from entering bloodstream

Know the main components of the central nervous system

Bottom > top: Spinal cord Hindbrain - pons, cerebellum, medulla Midbrain - dopaminergic neurons Diencephalon - contains thalamus Cerebral cortex

Basic anatomy of taste receptors in humans

Bumps (papillae) on toungue are surrounded by trenches containing the taste buds, which have both G-protein receptors and various direct ion channels

Describe how currents flow across the membrane during the action potential

Current is increasingly negative as sodium enters the cell, then a positive current is generated as potassium flows out after the peak of the action potential

List and explain the key events of phototransduction

DARK: cGMP binds to inside of receptors > channels open, Na+ and Ca++ flow in, K+ flows out > depolarization LIGHT: cGMP is reduced > Ca++ and Na+ channels close, K+ continues flowing out > hyperpolarization

Describe what determines whether a transmitter and receptor is inhibitory or excitatory

Depends on which ion channel receptors are present

Understand the major anatomical coordinates as they apply to the nervous system

Dorsal: crown of brain/backside of spine Ventral: underside of brain/stomach side of spine Rostral: front/top of brain Caudal: back of head/inferior spine Sagittal: midline plane Coronal: plane dividing front and back

Know when and how to apply the Nernst equation.

E = (RT/ZF) ln (Cout/Cin) Use when discussing the total membrane potential of one specific ion in a neuron

Describe major mechanosensory receptor organs and their basic functions

EPIDERMIS Free nerve endings: detect lighter touches and painful stimuli Merkel cells: small receptive field, form and texture perception. Most effective cells in reading braille DERMIS Meissner corpuscles: small receptive field, motion detection, and grip control Ruffini endings: large receptive field, direction of motion SUBCUTANEOUS Pacincian corpuscles: large receptive field, distant vibration, tool use PROPRIORECEPTORS Muscle spindles: wrap around muscle cells and respond to stress, obtaining info about internal muscular environment Golgi tendon organs: have nerve endings within tendons, gauge isotonic tension

Explain the basic organization and function of the eye, including the fovea and blind spot, the function of the lens, and the "inside out" layering of the retina

Fovea: concentrated collection of cones in the retina Blind spot: area with gap in the retina for optic nerve to pass through, no photoreceptors Lens: light passes through and is focused onto various spots on retina through accommodation (reshaping of lens by ciliary muscles) Retina: innermost lining of eye, contains the photoreceptors light > BACK - photoreceptors > (horizontal cells) > bipolar cells > (amacrine cells) > ganglion cells > optic nerve - FRONT

Understand how glia communicate with other glia and neurons

Glia can send "gliatransmitters" through vesicle fusion, exchangers, and transporters

Recognize in which way electrical properties of glia are different from those of neurons

Glia send nonsummative graded potentials, not action potentials

Define major differences between graded potentials and action potentials

Graded potentials are small excitatory (more positive) or inhibitory (more negative) currents varying in size and strength depending on ion concentrations and flow. Action potentials are generated by a voltage of about -40 mV and are an all or nothing current that initiates cell to cell communication.

Understand how action potentials propagate throughout the membrane

Graded potentials can summate, creating a current that reaches the threshold of excitation and triggers an action potential to occur.

Be able to recognize and describe electrical signals of neurons.

Graded potentials: may be receptor or synaptic. Analog signal (intensity makes a difference) Action potentials: All or nothing digital current, occurs when signal reaches the threshold of excitation

Explain the mechanism of synaptic habituation and sensitization of the sensory neuron to motor synapse, with the role of the interneuron

Habituation: innoculous stimulation of siphon will lead to decreased response over time Sensitization: innoculous stimulation of siphon paired with tail shock will active the modulatory neuron then interneuron, initiating glutamate release and g-protein signaling cascade that will cause increased gill withdrawal. Over time will lead to increased gill withdrawal from innocuous touches

Relative numbers of olfactory neurons in humans vs dogs, relative numbers of genes for ORMs in humans vs mice

Humans are relatively olfactory deficit! Humans: 12 million olfactory cells, 950 odorant receptor genes (60% dormant) Dogs: 1 billion olfactory cells Mice: 1500 odorant receptor genes

Be able to explain how changes in specific ion distributions would influence the resting potential.

Increased K+: hyperpolarization, more negative resting potential Increased Na+: depolarization, more positive resting potential

Describe typical ion distributions in and around neurons, and how these distributions come about.

Intracellular: High concentrations of potassium, low concentrations of sodium and chloride Concentrations are maintained at resting potential by ion channels - allow ions to diffuse down concentration gradient, creating selective permeability

Differentiate between pheromone perception in mice vs humans

Mice use pheromones for intercommunication, while it is unknown if humans use any pheromone signaling

Explain the advantages and disadvantages of multistep biochemical signaling

Multistep pathways allow for more regulation and amplification, creating a larger and more refined response from fewer signaling molecules. They are also less quick than direct synaptic transmission.

Compare and contrast neurons and glia

Neurons: 50% of brain volume, synapse using dendrites and axons, propagate APs as electrochemical impulses, no mitotic capability Neuroglia: 50% of brain volume, no dentrites/axons (protrusions!), propagate Ca++ signals, extensive mitotic capability

Explain the basic organization of the outer and inner ear

OUTER Auricle and ear canal - funnel sound waves in Tympanic membrane - eardrum, soundwaves vibrate Ossicles - malleus -> incus -> stapes; vibrate against each other to transmit sound from tympanic membrane to inner ear Oval window - connects with stapes, entrance to cochlea INNER Cochlea -3 chambers: scala vestibuli (top), scala media (middle), scala tympani (bottom) -Tectorial membrane - upper membrane, connects to the hair cells of the basilar membrane -Basilar membrane - houses hair cells, ceiling of scala tympani Vestibular system - composed of semicircular canals (acceleration) and utricle/saccule (gravity)

Basic anatomy of the human olfactory system

Odorants enter nasal cavity and depolarize olfactory epithelium, triggering spike potentials tp travel up the olfactory nerves inside the cribriform plate to the olfactory bulb, bypassing the thalamus. The input finally reaches and synapses in the endorhinal cortex.

Describe the mechanism of long term synaptic sensitization in an aphasia circuit

Over time, PKA will cause genes to code for more regulatory components that will lead to a constant phosphorylated state and stronger synaptic activity, strengthening the response

Be able to describe neural pathways that underlie mechano and pain sensation and their cortical representation

Pain fibers: travel contralaterally along spinal cord and end in somatosensory cortex and limbic system mechanosensory fibers: travel ipsilaterally along spinal cord and end in somatosensory cortex

Explain what a pump does, compared to an exchanger or a co-transporter

Pumps are primary active transporters that use energy from the breakdown of ATP, while exchangers and cotransporters are secondary active transporters. They move ions down the concentration gradients that have been generated by pumps.

Understand the concept of a receptive field and be able to apply it to two point discrimination

Receptive field: area in which the presence of a stimulus will alter the firing of a neuron. Due to the close proximity of sensory cells, fields may overlap, creating a unipolar spike potential if two stimuli are too close in proximity

Explain changes in ion conduction during each stage of the action potential

Resting: potassium passing through leak channels Rising: Sodium flows into cell through voltage gated channels Falling phase: Voltage gated potassium channels/sodium potassium pumps allow potassium to flow out of the cell Recovery: Inactivation of voltage gated channels, potassium leak channels generate hyperpolarization

Explain which currents cause what portions of the action potential, during the rising, falling, and after-hyperpolarization phases.

Rising: generated by depolarizing sodium current Falling: hyperpolarizing current from voltage gated potassium channels Recovery: both currents die out and return to resting potential

Explain the key differences between rods and cones

Rods: detect contrast, active at very low light levels. Comprised of longer outer segment with disks and cytoplasmic space Cones: shorter receptors, detect color at higher light ranges

Explain in detail the molecular machinery that holds the how vesicles are triggered to release when an action potential stimulates the presynaptic membrane.

SNARE protein complex - t snare: fuses to postsynaptic membrane - v snare: binds to vesicles

Explain the difference between simple and complex cells in the visual cortex

Simple cells - only fire in response to one stimulus position complex cells - can respond to stimuli of any position as long as they are oriented correctly, allowing for more abstract visual processing

Describe the differences between small molecule and peptide neurotransmitters.

Small molecule: fast acting, carry a short-term response Peptide: 3-36 amino acids long, slow acting with a prolonged response

Explain why neurons need synapses.

Synapses are responsible for the actual transmission of signals from neuron to neuron/receptor cell, and can also release neurotransmitters when induced by action potentials

Explain the functional characteristics of the NMDA receptor that make it capable of being a coincidence detector.

The Mg2+ block allows NMDA receptors to serve as coincidence detectors. In order for NMDA receptors to open, the receptors require both glutamate and a depolarizing current, causing the Mg2+ to be removed and the ions to flow through. The depolarizing current must be generated by both the post and presynaptic neurons firing

Define the aplysia gill reflex

The aplysia snail will withdraw its gill when the siphon is touched

Define the localization of sound based on interaural time differences by projections to the medial superior olive

The ear closest to the sound source will recieve the most stimulation, allowing the impulse to travel to the other end of the medial superior olive while the ear futher away only sends a signal to the closer end. Depending on the side of the MSO recieving the signal, the closeness of stimuli to one ear or the other can be determined

Be able to describe the gate mechanisms that can alter the perception of pain

The firing of mechanosensory A-beta fibers activates the inhibitory interneuron that connects to the pain pathway, thus decreasing the chances of a pain signal being transmitted and reducing the sensation of pain when mechanosensory stimulation is present Inhibit at: -interneuron -C fiber synapse -dorsal horn projection neuron synapse

Understand how the flow of specific ion types results in potential changes across the membrane.

The influx of Na+ ions depolarizes the membrane - may trigger action potential if threshold of excitation is reached! Flow of K+ ions out hyperpolarizes the membrane - falling phase of action potential

Understand variation in neural firing patterns (such as tonic and phasic patterns of activation)

Tonic: sustained, constant firing Phasic: intermittent firing of action potentials

Be able to explain the organization of the spinal column

Top > bottom: Cervical vertebrae (8) Thoracic vertebrae ( 12) Lumbar vertebrae (5) Sacral vertebrae (5) Coccyx Cauda equina: includes nerves from lumbar, sacral, and coccygeal pairs Vertebrae composed of white matter horns surrounded by gray matter columns

Explain the role of the utricle and saccule as gravity detectors, and the ampullae as rotational acceleration detectors

Utricle/saccule: contain a gelatinous layer called the macula housing hair cells and otolith crystals. Tilt causes the otoliths to shift within the macula and pull on the hair cells, allowing gravity to be sensed. Ampullae: rounded chambers of semicircular canals containing fluid and hair cells. Movement of fluid causes the ampullae to move, the speed of which can be used to detect acceleration. More fluid sloshing = increased strength of pulses fired

Describe the molecular structure of voltage gated K+, Na+ and Ca++ channels.

Voltage gated channels are composed of a transmembrane unit, pore domain, voltage sensor, binding sites, beta protein subunit, and sometimes inactivation balls.

Be able to describe the flow of ions within hair cells during the bending of cilia

When cilia are bent, the previously closed K+ and Ca++ channels open, allowing the ions to flow INWARD and depolarize the hair cell ***Inward positive current is depolarizing due to the high positive charge and high K+ concentration of the scala media!

Describe the mechanisms of the following: a. Short term facilitation b. Short term depression c. Post tectonic augmentation d. Long term potentiation

a. Facilitation is initiated by synaptic activity b. Depression is caused by a decrease in postsynaptic responses after facillitation due to depletion of vesicles c. Augmentation - the pulses caused by the increase in readily available vesicles after tetanus has ended d. Long term potentiation: over time, genes are coded for more regulatory components that create a consistent phosphorylated state -> strengthen synapses over time!

understand how left and right visual fields from both eyes project to contralateral hemispheres

due to crossover in optic chiasm, retinal input is mirrored AND upside down

Describe the difference (in structure and function) of electrical and chemical synapses.

electrical synapses: less common, faster but simpler. join cytoplasm of sending and recieving cells directly through gap junctions chemical synapses: release neurotransmitters into synaptic cleft through exocytosis. more adaptable

understand the role of lateral inhibition in the retina and how it contributes to the center-surround receptive field architechture of retinal ganglion cells and edge detection

excited horizontal cells can inhibit neighboring cells, leading to the increased contrast in edges - forms a sharper image

what are the 2-3 niches in the adult brain that make new neurons?

hippocampus, olfactory bulb, and olfactory epithelium (PNS)

explain regrowth of cut neurons, as well as the failure to generate new in the adult brain

if neurons are cut in the axons, they may be able to regrow - neurons cannot regenerate if injured due to hypoxemia (cell bodies would die)

Explain the differentiating characteristics of ion pumps and ion channels in terms of active and passive transporters

ion channels: passive, allow ions to move down their concentration gradient ion pumps: active, use ATP phosphorylation to move ions against concentration gradient

Be able to explain receptive fields in different components of the retina and on-center vs off-center bipolar cells and ganglion

monocular receptive field: outer edges of visual field, pathway travels ipsilaterally with no crossover in optic chiasm binocular receptive field: center portion of visual field, pathway travels contralaterally, crossing over in optic chiasm visual field is projected onto retina both mirrored and upside-down! on-center cells: light in center is excitatory, light in surround is inhibitory off-center cells: light in center is inhibitory, light in surround is excitatory on and off center cells can be used to define edges!

Determine what physiological characteristics will result if a certain functional part of a channel is changed or blocked in a specific way.

pore: ions would not be able to move through the channel despite depolarization voltage sensor: the channel would not be able to open or close in response to changes in membrane potential pore loop: there would be nothing to physically open the channel

Known mechanisms of salt, acid, sweet, umami, and bitter taste transduction

salt/acid: act directly on ion channels, causing depolarization of Na+ and K+ channels, leading to signaling sweet/bitter/umami: amino acid signaling, act on g-protein receptors, which then use secondary messengers to trigger Na+ and K+ channels

Describe the components of a basic circuit, including sensory neurons, interneurons, and the motorneuron

sensory neuron - detect stimulation, transmits to modulatory neuron > interneuron > g-protein cascade > motor neuron > reflexive action

Name the known types of receptors

sweet, sour, bitter, salt, umami

circuit construction through overlapping initial innervation followed by activity-dependent pruning

synapses start with multiple neurons connected to one cell, then the highest activity synapse remains connected

Describe the various sources of signals (synaptic, paracrine, endocrine)

synaptic: released into synaptic cleft -> postsynaptic receptors paracrine: released to receptors on multiple target cells endocrine: released into capillary bloodstream and transported to distant cells

Describe the functional characteristics of each structural characteristic of the above channels

transmembrane units/pore loop: insert into cell membrane pore: tunnel that allows ions to pass through voltage sensors: contain positive charges that enable movement (closes pore when hyperpolarized, opens when depolarized)