Neuro E2 Hail Mary

Godspeed

Ways Acetylcholine Agonists Exert Effects

1) Directly bind and activate ACh receptors (nicotine, muscarine)

2) Trigger massive presynaptic ACh release (black widow spider venom)

3) Inhibit acetylcholinesterase (AChE) from breaking down ACh (Sarin gas, VX nerve agent).

Immunocytochemistry

Experimental cell-imaging method that uses tagged antibodies to localize proteins, neurotransmitters, or enzymes inside cells ("snapshot of cells").

In Situ Hybridization

Experimental cell-imaging method that uses labeled complementary nucleic acid probes to detect mRNA and localize active protein/peptide synthesis in a cell.

Ligand-Binding & PET

Experimental receptor-imaging methods that use radioactive ligands to locate receptors in brain tissue or in the living brain via Positron Emission Tomography (PET).

Precursor for Catecholamine Monoamines (Dopamine, Norepinephrine, Epinephrine)

Tyrosine.

Precursor for Indolamine Monoamines (Serotonin / 5-HT)

Tryptophan.

Acetylcholine Synthesis

Acetyl CoA + Choline -> ACh + CoA (catalyzed by the enzyme Choline acetyltransferase / ChAT).

Acetylcholine Degradation

ACh -> Acetic acid + Choline (catalyzed by the enzyme Acetylcholinesterase / AChE in the synaptic cleft).

Main Excitatory Neurotransmitter in the CNS

Glutamate.

Main Inhibitory Neurotransmitters in the CNS

GABA and Glycine.

Ionotropic Receptors

Fast ligand-gated ion channels (made of 4 or 5 subunits forming a pore):

AMPA, NMDA, Kainate, GABA_A, Glycine, Nicotinic ACh (nACh), Serotonin (5-HT3), and Purines (P2X).

Metabotropic Receptors

Slow/modulatory G-protein-coupled receptors (GPCRs):

mGluRs (1–8), GABA_B, Dopamine (D1–D5), NE/Epi (alpha and beta), Histamine, Serotonin (all except 5-HT3), Muscarinic ACh (M1–M5), and Purines (A-type/P2Y).

Basic Structure of a GPCR

A single polypeptide with 7 membrane-spanning alpha-helices coupled to an intracellular 3-subunit (alpha, beta, gamma) G-protein.

Glutamate Receptors (Ionotropic)

AMPA (Na+ channel)

Kainate (Na+ channel)

NMDA (Na+ and Ca2+ channel that has 2 binding sites, is blocked by Mg2+ at resting potential, and requires membrane depolarization to open).

Glutamate Receptors (Metabotropic)

mGluRs (8 subtypes of GPCRs that increase or decrease NMDA receptor activity).

General Categories of Neurotransmitters

Amino acids (glutamate, GABA, glycine, aspartate)

Amines (catecholamines and indolamines)

Peptides (endorphins, enkephalins, substance P)

Esters (acetylcholine), and Others (ATP, NO, CO).

Chemoreceptors

Sensory receptors that respond to chemicals (used in gustation/taste and olfaction/smell).

Filiform Papillae

Cone-shaped bumps located all over the tongue.

Fungiform Papillae

Mushroom-shaped bumps located on the sides and tip of the tongue.

Foliate Papillae

Fold-shaped ridges located on the back and sides of the tongue.

Circumvallate (Vallate) Papillae

Mound-shaped bumps arranged in a V at the back of the tongue.

Types of Taste Receptors

Saltiness (Na+ channel)

Sourness (H+/K+ channels)

Bitterness (T2R GPCRs)

Sweetness (T1R2+T1R3 GPCR)

Umami (T1R1+T1R3 GPCR).

Salt Receptor

Na+-selective channel that lets Na+ enter and depolarize the taste cell, opening voltage-gated Na+ and Ca2+ channels to release serotonin (5-HT).

Amiloride

A high blood pressure drug that blocks the Na+-selective salt taste channel.

Receptor for Acidity (Sourness)

H+ ions from acidic foods enter proton channels and block K+ leak channels; positive charge builds up, depolarizing the taste cell and releasing serotonin (5-HT).

Taste Perception Pathway

Tongue/Epiglottis ->

Cranial Nerves 7, 9, 10 ->

Medulla (gustatory nucleus / solitary tract) ->

VPM Nucleus of Thalamus ->

Primary Gustatory Cortex (Insular cortex: "What am I tasting?") & Parietal Cortex ("What texture is on my tongue?") (Ipsilateral).

Secondary Taste Pathways

From the medulla, taste also projects to the Pons (vomiting center), Hypothalamus (appetite/satiety), and Amygdala/Hippocampus (emotional response).

Locations of Primary Chemical Senses

Taste (gustation): taste buds on the tongue, epiglottis, soft palate, and pharynx; Smell (olfaction): olfactory epithelium in the top of the nasal cavity.

How Mammals Detect Pheromones

Using the Vomeronasal Organ (VNO) in the nasal cavity (often inhaling pheromones via the Flehmen response), which sends signals to the accessory olfactory bulb, medial amygdala, and hypothalamus.

Oldest Sense

Chemical sensation (gustation and olfaction).

Layout of the Retina

Divided into nasal and temporal halves;

features the optic disk (blind spot where blood vessels and optic nerve exit)

and the macula (center of retina containing the fovea pit).

Difference Between Rods and Cones

Rods: long/cylindrical, many disks, 1000x more sensitive to dim light, high convergence, located in peripheral retina; Cones: short/tapering, fewer disks, detect bright light and color (high visual acuity), low convergence, concentrated in the fovea.

Layers of the Retina (Inside-Out)

Light travels through: Ganglion cell layer -> Amacrine Cell (Inner plexiform layer) -> Inner nuclear layer → bipolar cell → horizontal (Outer plexiform layer) -> Outer nuclear layer -> Photoreceptor outer segments -> Pigmented epithelium.

Duplex Retina

A retina containing both rods (scotopic/dim peripheral vision) and cones (photopic/bright, color, high-detail foveal vision).

Trichromatic Theory

Specific colors result from the relative activity of three cone types:

Short/Blue (~430 nm), Medium/Green (~530 nm), and Long/Red (~560 nm).

Targets of the Optic Tract

1) LGN of the Thalamus (conscious vision)

2) Hypothalamus (biological rhythms)

3) Tectum (pupil size and eye movement)

4) Superior colliculus (orients eyes/fovea to new stimuli).

Damage to Optic Nerve, Tract, and Chiasm

Left optic nerve cut = blindness in left eye (left hemifield)

Left optic tract cut = blindness in right visual field

Optic chiasm cut = tunnel vision (loss of peripheral vision).

Cells in Primary Visual Cortex (V1)

Simple cortical cells (monocular; respond to stationary bars/edges of light at a specific orientation with on/off areas),

Complex cells (binocular/monocular; respond to moving bars of light at a specific orientation)

Blobs (analyze color).

On-Center and Off-Center Cells

Retinal ganglion cells that detect illumination contrast/edges:

On-center cells fire action potentials when light hits the center (inhibited by light in surround)

Off-center cells fire when dark hits the center or light hits the surround (inhibited by light in center).

Structure of the Tympanic Membrane

Cone-shaped membrane (eardrum) at the end of the outer ear's auditory canal that vibrates in response to sound waves and moves the malleus.

Attenuation Auditory Reflex

Contraction of the tensor tympani and stapedius muscles during loud sounds; adapts to loud sounds, protects the inner ear, and helps understand speech better.

Middle Ear and Its Components

Air-filled cavity with the Eustachian tube

two muscles (tensor tympani, stapedius), and three ossicles (Malleus, Incus, Stapes) that amplify vibrations from the tympanic membrane to the oval window.

Basilar Membrane Structure

Membrane in the cochlea supporting the Organ of Corti; narrow and stiff at the base (high frequencies, 20,000 Hz) and wider and less stiff at the apex (low frequencies, 20 Hz).

Flow of Fluid Through the Cochlea

Stapes pushes oval window ->

pushes perilymph in scala vestibuli to apex (helicotrema) ->

flows into scala tympani to round window ->

bends basilar membrane upward and bends hair cell stereocilia.

Structure of the Cochlea and Its Fluids

Divided into 3 fluid chambers by Reissner's membrane and the basilar membrane:

Scala vestibuli (top, perilymph),

cala media (middle, endolymph with Organ of Corti),

Scala tympani (bottom, perilymph).

Causes of Deafness

Conduction deafness (earwax, tympanic membrane rupture, ossicle damage)

Nerve deafness (damage to the auditory nerve or hair cells).

What the Vestibular System Detects

Balance, equilibrium, posture, and head/body/eye movements: Otolith organs (utricle and saccule) detect gravity, head tilt, and linear acceleration; Semicircular canals detect head rotation.

Glabrous Skin

Smooth, hairless skin found on the palms, fingers, soles of the feet, and lips.

Meissner's Corpuscle

Small receptive field, rapid adaptation (superficial skin mechanoreceptor).

Merkel's Disk

Small receptive field, slow adaptation (superficial skin mechanoreceptor).

Pacinian Corpuscle

Large receptive field, rapid adaptation (deep skin mechanoreceptor).

Ruffini's Ending

Large receptive field, slow adaptation (deep skin mechanoreceptor).

What a Homunculus Illustrates

A somatosensory cortex map showing that cortical space is proportional to receptor density and sensitivity (largest for hands, fingers, lips, and tongue) rather than physical body size.

Sensory Neuron Crossing & Spinal Tract

Touch/vibration axons travel up the spinal cord ipsilaterally in the Dorsal Columns,

cross (decussate) in the Medulla (contralateral by the midbrain)

and travel up the Medial Lemniscus to the thalamus.

Somatosensory Areas of the Parietal Lobe

Somatosensory cortex (Areas 1, 2, 3a, 3b in the postcentral gyrus)

Posterior parietal cortex (Areas 5, 7).

Segments of the Spinal Cord

30 total segments in 4 divisions:

Cervical (C1–C8), Thoracic (T1–T12), Lumbar (L1–L5), and Sacral (S1–S5).