Textbook Sections (Midterm 1) Flashcards
What are the three broad categories of anesthesia?
Local anesthesia, regional anesthesia (larger region than local like epidural during child birth), and general anesthesia
How do local anesthetics like lidocaine work?
Block Na+ channels → inhibit action potentials → numb sensation
When are sedatives used?
Sedatives are often used alongside anesthesia to reduce anxiety or induce sleep
What is the role of GABA receptor agonists in sedation?
They enhance inhibitory synaptic transmission, reducing neuronal activity
How does general anesthesia typically affect neurons?
General anesthetics often work on GABA receptors or block glutamate NMDA receptors (e.g., ketamine)
What does the Goldman equation account for that the Nernst equation does not?
The Goldman equation accounts for the permeability of multiple ions across the membrane
What happens to membrane potential if only Na+ is permeable?
ENa (around +60 mV)
How does membrane permeability change during an action potential?
During an action potential, Na+ permeability increases, causing depolarization, and later K+ permeability increases causing hyperpolarization
Why are squid giant axons important in neuroscience research?
Their large size allows for easy experimental manipulation and was crucial in the study of action potentials (helped Hodgkin and Huxley observe changes in Na+ and K+ conductance)
What evolutionary advantage do giant axons provide squid?
Can conduct APs quicker, making it easier to escape prey
What do Tetrodotoxin (pufferfish) and saxitoxin (dinoflagellates) do to Na⁺ channels?
They block Na⁺ channels, leading to paralysis by preventing action potential generation
What is the effect of μ-conotoxins from cone snails on Na⁺ channels?
They block Na⁺ channels, paralyzing prey
How do α-toxins from scorpions affect Na⁺ channels?
They prolong Na⁺ channel inactivation, increasing the duration of action potentials and disrupting normal neuronal function
What do β-toxins from scorpions do to Na⁺ channels?
They shift the voltage dependence of Na⁺ channel activation, causing channels to open at more negative potentials and inducing uncontrolled action potential firing
How does batrachotoxin from frogs affect Na⁺ channels
It removes inactivation of Na⁺ channels, causing continuous neuronal firing
Which toxins block K⁺ channels, and what is their effect
Dendrotoxin (wasps), apamin (bees), and charybdotoxin (scorpions) block K⁺ channels
What are channelopathies?
Genetic diseases caused by mutations in ion channel genes, affecting voltage-gated or ligand-gated ion channels
What is the main characteristic of epilepsy and how are ion channels involved?
Recurring seizures linked to mutations in Na⁺, K⁺, and Ca²⁺ channel genes
What ion channel mutation is associated with Severe Myoclonic Epilepsy of Infancy?
Reduced Na⁺ channel function due to mutations in SCNAs
How does a mutation in KCN genes cause Benign Familial Neonatal Convulsion?
Mutations in K⁺ channels cause brief seizures in newborns
What is ataxia and which ion channel mutations are involved?
Ataxia is the loss of voluntary motor movement, often caused by mutations in K⁺ or Ca²⁺ channels
How does a mutation in CACNA1A cause Spinocerebellar Ataxia Type 6?
Polyglutamine expansions in this Ca²⁺ channel gene lead to degeneration of cerebellar cells
What mutation is associated with Familial Hemiplegic Migraine Type 1?
Gain-of-function mutations in CACNA1A, increasing Ca²⁺ current and causing severe headaches and ataxia
How do mutations in the SCN9A gene affect pain perception?
Mutations lead to conditions like Inherited Erythromelalgia (IEM), where Na⁺ channels are more excitable, increasing pain sensitivity
What is Sinoatrial Node Dysfunction and Deafness (SANDD) caused by?
A mutation in CACNA1D that disrupts Ca²⁺ influx, leading to congenital deafness and cardiac dysfunction
What ion channel mutation is linked to X-linked Congenital Stationary Night Blindness (CSNB)?
Mutations in CACNA1F reduce Ca²⁺ currents in retinal cells, impairing night vision
How does latrotoxin cause excessive neurotransmitter release?
It bypasses the usual Ca²⁺ requirement for vesicle fusion, leading to painful muscle cramping
What is the effect of botulinum toxin on neuromuscular transmission?
It blocks neurotransmitter release at neuromuscular junctions, leading to paralysis by cleaving SNARE proteins
How does tetanus toxin affect the spinal cord?
It blocks inhibitory neurotransmitter release, leading to uncontrolled muscle contractions (tetany)
What are myasthenic syndromes, and what do they cause?
Myasthenic syndromes cause weakness and fatigue due to defective neuromuscular transmission
What is Lambert-Eaton Myasthenic Syndrome (LEMS) and its cause?
LEMS is an autoimmune disorder where antibodies target and reduce the number of voltage-gated Ca²⁺ channels in motor neuron terminals, decreasing neurotransmitter release and causing muscle weakness
What are congenital myasthenic syndromes?
Congenital myasthenic syndromes are genetic disorders affecting presynaptic proteins (e.g., SNAP-25, synaptotagmin) or vesicle size, resulting in reduced acetylcholine release and muscle weakness
What causes color blindness?
Mutations in the genes for cone photopigments
How does the brain distinguish color?
Compares the activity levels of different cone types (ex: green light activates both M and L cones, but the M cones are more strongly activated, signaling green to the brain)
What happens if the three types of cones overlap?
The overlap in their absorption spectra allows us to perceive various colors
What are the three types of cones?
Short- (S), medium- (M), and long-wavelength (L)
What is Protanopia?
Loss of long-wavelength-sensitive cones (L cones); difficulty perceiving reds
What is Deuteranopia?
Loss of medium-wavelength-sensitive cones (M cones); difficulty perceiving greens
Where are color blindness conditions most common?
These deficiencies are more common in males because the genes for the L and M pigments are located on the X chromosome
What is color contrast?
The perception of a color changes based on its surrounding colors
What is color consistency?
Despite changes in lighting, an object’s color can appear constant, allowing us to recognize objects under different lighting conditions (e.g., a tennis ball looking the same in sunlight and at dusk)
Besides wavelength, what two other things help with perceiving colors?
- Context
- Past experiences
What neurotransmitter receptors are affected by toxins from plants and animals?
Many toxins affect neurotransmitter receptors, particularly acetylcholine (ACh) receptors, glutamate receptors, GABA receptors, and glycine receptors
What are nicotinic and muscarinic ACh receptors named after?
Nicotinic ACh receptors are named after nicotine (from tobacco), and muscarinic ACh receptors are named after muscarine (from the mushroom Amanita muscaria)
What are the symptoms of nicotine and muscarine poisoning?
Symptoms include nausea, convulsions, and, in the case of muscarine poisoning, potentially death
Name three toxins that block nicotinic ACh receptors and their sources
α-bungarotoxin from the banded krait snake
Curare (δ-tubocurarine) used by South American natives
α-conotoxin from cone snails
What are atropine and scopolamine, and what do they block?
Atropine (from deadly nightshade) and scopolamine (from henbane) are plant toxins that block muscarinic ACh receptors
What receptor does the betel nut toxin arecoline target, and what is its effect?
Arecoline from betel nuts targets nicotinic ACh receptors and acts as a stimulant
Name two toxins that target glutamate receptors and their sources
Kainate and quisqualate from mushrooms and seaweeds target glutamate receptors, causing excitotoxicity
What does strychnine block, and what is its effect?
Strychnine blocks glycine receptors, leading to seizures
What do bicuculline and picrotoxin block, and what is their effect?
Bicuculline (from Dutchman’s breeches) and picrotoxin block GABA receptors, causing overstimulation of the CNS
What is muscimol, and what does it activate?
Muscimol is a hallucinogen from mushrooms that activates GABA receptors
How does baclofen function and what is it used for?
Baclofen is a synthetic GABA receptor agonist used to treat muscle spasms
What are the key toxins to remember that block nicotinic ACh receptors?
α-bungarotoxin, curare (δ-tubocurarine), and α-conotoxin
How does GABA function in the developing brain compared to the mature brain?
In the developing brain, GABA acts as an excitatory neurotransmitter, while in the mature brain, it functions as an inhibitory neurotransmitter
What causes GABA’s shift from excitatory to inhibitory during brain development?
The shift is due to changes in intracellular Cl⁻ concentration, driven by the Na⁺/K⁺/Cl⁻ co-transporter in immature neurons and the K⁺/Cl⁻ co-transporter in mature neurons
What is the role of NKCC1 and KCC2 in the function of GABA?
NKCC1 increases intracellular Cl⁻ in immature neurons, making GABA excitatory. KCC2 removes Cl⁻ from cells in mature neurons, making GABA inhibitory
Why is early depolarizing GABA important during brain development?
Early depolarizing GABA responses help control neuronal growth, migration, and synaptic development
