MT 2 - Textbook Flashcards
transporter
specialized membrane component that returns transmitter molecules to the presynaptic neuron for reuse.
ionotropic receptor
- fancy ion channel
- when bound by a neurotransmitter molecule, an ionotropic receptor quickly changes shape, opening (or closing) its integral ion channel
- The opening (or closing) of channels in the postsynaptic membrane allows more (or fewer) of the channels’ favored ions to flow into or out of the postsynaptic neuron, thus changing the local membrane potential.
metabotropic receptor
- provide a link across the cell membrane to G proteins
- When activated, metabotropic receptors alter the inner workings of the postsynaptic cell, using second messengers that are activated by the G proteins.
- This two-step signaling process can cause changes in excitability of the postsynaptic cell, or it can cause other, slower but larger-scale responses.
Otto Loewi
electrically stimulate the vagus nerve in a frog, which he knew would cause its heart to slow down. The question was, Why did the heart slow down? Had electricity jumped from the vagus nerve to the heart, as the “sparks” believed? Or were the “soups” right? Had the nerve released a chemical to slow the heart?
collect the fluid that surrounded the slowing heart. Then he applied that fluid to the heart of another frog. If the first heart had been slowed by electrical signals from the vagus, then the fluid should have no effect on the second heart. But if activation of the vagus caused it to release a chemical that slowed the beating of the heart, then the fluid from the first heart should alter the beating of the second. In fact, the transferred fluid caused the second heart to slow down, providing Loewi with conclusive evidence of chemical neurotransmission (and a nice shiny Nobel Prize, in 1936). The neurotransmitter was later chemically identified as acetylcholine (ACh for short). The “soups” were vindicated.
Distinguish between endogenous and exogenous substances
endogenous is a substance from inside the body (psychotropic drugs). Exogenous substances come from outside the body.
what qualifications must a substance meet to be a transmitter candidate
- It can be synthesized by presynaptic neurons and stored in axon terminals.
- It is released when action potentials reach the terminals.
- It is recognized by specific receptors located on the postsynaptic membrane.
- It causes changes in the postsynaptic cell.
- Blocking its release interferes with the ability of the presynaptic cell to affect the postsynaptic cell.
amino acid neurotransmitters
A neurotransmitter that is itself an amino acid. Examples include GABA, glycine, and glutamate.
peptide neurotransmitters
Also called neuropeptide. A neurotransmitter consisting of a short chain of amino acids.
amine neurotransmitters
A neurotransmitter based on modifications of a single amino acid nucleus. Examples include acetylcholine, serotonin, and dopamine.
gasotransmitters
Also called gas neurotransmitter. A neurotransmitter that is a soluble gas. Examples include nitric oxide and carbon monoxide.
what are the most abundant neurotransmitters
amino acids
glutamate and GABA are most studied
glutamate
- employ three subtypes of ionotropic receptors—AMPA, kainate, and NMDA receptors—named for the compounds that selectively activate them.
- Activation of AMPA receptors, the most plentiful receptors in the brain, has rapid excitatory effects. NMDA receptors have unique characteristics that suggest they play a central role in memory formation
gaba
- subtypes of receptors for GABA
- GABAa receptors are related to anxiety relief. The are ionotropic; when activated, they allow more Cl– ions to flow into the postsynaptic cell, resulting in a rapid-onset local hyperpolarization that inhibits the cell’s activity.
- Compounds that mimic this action of GABAa tend to be effective calming agents because they produce a widespread decrease in neural activity. They thereby decrease the excitability of neurons
- GABAb receptors, in contrast, are metabotropic receptors with slower postsynaptic effects
- GABAb-selective drugs may help treat diverse chronic problems such as pain and mood disorders
co-localization
The synthesis and release of more than one type of neurotransmitter by a given presynaptic neuron.
important note for NTs
each of these classical neurotransmitters is carried by a different set of axons, and those axons project to different brain regions. Each type of neurotransmitter is thus talking to a distinct set of brain targets, and there may be overlap as two different transmitters arrive at the same target. How those targets respond depends on which neurotransmitter is being released and which kinds of receptors the target neurons possess
what are the known receptor subtypes of glutamate (are they metabo- or ionoropic)
AMPA, kainate, and NMDA receptors (ionotropic); mGluR’s (metabotropic glutamate receptors)
what is the function of glutamate AMPA, kainate, and NMDA receptors
Glutamate is the most abundant of all neurotransmitters and the most important excitatory transmitter. Glutamate receptors are crucial for excitatory signals, and NMDA receptors are especially implicated in learning and memory.
what are the known receptor subtypes of GABA
GABAa (ionotropic)
GABAb (metabotropic
what is the function of GABAa (ionotropic) receptor
GABA receptors mediate most of the brain’s inhibitory activity, balancing the excitatory actions of glutamate. GABAA receptors are inhibitory in many brain regions, reducing excitability and preventing seizure activity.
what is the function of GABAb (metabotropic) receptor
GABAB receptors are also inhibitory, by a different mechanism.
what are the known receptor subtypes of acetylcholine
muscarinic receptors (metabotropic)
nicotinic receptors (ionotropic)
what is the function of acetylcholine muscarinic (metabotropic) receptors
Both types of receptors are involved in cholinergic transmission in the cortex.
what is the function of acetylcholine nicotinic (ionotropic) receptors
Nicotinic receptors are crucial for muscle contraction.
what are the known receptor subtypes of dopamine
D1 through D5 receptors (all metabotropic)
what is the function of dopamine D1 through D5 receptors
(all metabotropic receptors)
DA receptors are found throughout the forebrain.
DA receptors are involved in complex behaviors, including motor function, reward, and higher cognition.
what are the known receptor subtypes of norepinephrine
α1, α2, β1, β2, and β3 receptors (all metabotropic)
what is the function of norepinephrine a1, a2, B1, B2, and B3 receptors
(all metabotropic)
NE has multiple effects in visceral organs, important in sympathetic nervous system and fight-or-flight responses. In the brain, NE transmission provides an alerting and arousing function.
what are the known receptor subtypes of serotonin
5-HT1 receptor family (5 members)
5-HT2 receptor family (3 members)
5-HT3 through 5-HT7 receptors (all but one subtype [5-HT3] metabotropic)
what is the function of serotonin 5-HT1 receptor family
(5 members)
Different subtypes differ in their distribution in the brain.
what is the function of serotonin 5-HT2 receptor family
(3 members)
5-HT2 receptors may be involved in mood, sleep, and higher cognition.
what is the function of serotonin 5-HT3 through 5HT7 receptor family
(all but one subtype [5-HT3] metabotropic)
5-HT3 receptors are particularly involved in nausea.
what are the known receptor subtypes of miscellaneous peptides
Many specific receptors for peptides such as opioids (delta, kappa, and mu receptors), cholecystokinin (CCK), neurotensin, neuropeptide Y (NPY), and dozens more (all metabotropic)
what is the function of miscellaneous peptide receptors
Peptide transmitters have many different functions, depending on their anatomical localization. Some important examples include the control of feeding, sexual behaviors, and social functions.
dopaminergic
Referring to cells that use dopamine as their synaptic transmitter.
mesostriatal pathway
one of the dopaminergic pathways
One of these projections is called the mesostriatal pathway because it originates in the midbrain (mesencephalon) around the substantia nigra and projects axons to the basal ganglia (aka the striatum)
mesolimbocortical pathway
one of the dopaminergic pathways
originates in a midbrain region called the ventral tegmental area (VTA) and projects to various locations in the limbic system and cortex.
The mesolimbocortical system appears to be especially important for the processing of reward; it’s probably where feelings of pleasure arise.
Thus, it makes sense that the mesolimbocortical dopamine system is important for learning that is shaped by positive reinforcement (which usually involves a reward), especially via the D2 dopamine receptor subtype (Lerner et al., 2021).
Abnormalities in the mesolimbocortical pathway are associated with some of the symptoms of schizophrenia.
what does reuptake require
Reuptake of transmitters relies on transporters that bind molecules of neurotransmitter and conduct them back inside the presynaptic terminal. Once inside, the neurotransmitter molecules can be recycled.
qualifications for something to be an NT
- can be synthesized by presynaptic neurons and stored in axon terminals.
- released when APs reach terminal
- recognized by specific receptors on postsynaptic neuron
- causes change in postsynaptic cell
- blocking its release interferes with the ability of the presynaptic cell to affect the postsynaptic cell
chemical families of NTs
- amino acid
- peptide (neuropeptide)
- amines
- gases
amino acid and peptide NTs
based on single amino acid molecules or on short chain of amino acids (aka peptides)
amine NTs
a group of chemical messengers that include dopamine, serotonin, norepinephrine, epinephrine, and acetylcholine
gasotransmitters
gas molecules that dissolve in water (aka soluble gas) that diffuse between neurons to alter ongoing processes
subcategories of amine NTs
quaternary amines and monoamines
subcategories of neuropeptide NTs
opioid peptides and other neuropeptides
what are the most abundant NTs
amino acids
what are the most studied amino acid NTs (one excitatory and one inhibitory example)
glutamate (excitatory) and GABA (inhibitory)
glutamate
glutamatergic (glutamate-using) synapses employ subtypes of ionotropic receptors. several additional subtypes of glutamate receptors are metabotropic.
Glutamate is the most abundant of all neurotransmitters and the most important excitatory transmitter. Glutamate receptors are crucial for excitatory signals, and NMDA receptors are especially implicated in learning and memory.
glutamatergic
glutamate-using
what are the subtypes of ionotropic receptors for glutamate
AMPA
kainate
NMDA
named for the compounds that selectively activate them
what does activation of AMPA receptors do
- most plentiful receptors in the brain
- has rapid excitatory effects
what does activation of NMDA receptors do
play a role in memory formation
GABA
- GABA and GABA(A) receptors have been studied due to their relationship to anxiety relief
- GABA(A) receptors are ionotropic when activated, allowing more Cl- ions to flow into postsynaptic cell (causing hyperpolarization to inhibit cell activity)
- compounds that mimic GABA(A) show calming effects (ex., xanax) because they potentially activate GABA(A) receptors
- GABA(B) receptors are metabotropic. Drugs that select for GABA(B) may help treat chronic pain.
GABA(A) vs. GABA(B)
GABA(A) = ionotropic
GABA(B) = metabotropic
types of acetylcholine receptors
muscarinic (metabotropic) and nicotinic (ionotropic)
types of norepinephrine receptors
alpha 1, alpha 2, beta 1, beta 2, beta 3 (all metabotropic)
types of serotonin receptors
- 5-HT1 receptor family (5 members)
- 5-HT2 receptor family (3 members)
- 5-HT3 through 5-HT7 receptors
(all but one subtype [5-HT3] are metabotropic)
miscellaneuos peptides
Many specific receptors for peptides such as opioids (delta, kappa, and mu receptors), cholecystokinin (CCK), neurotensin, neuropeptide Y (NPY), and dozens more (all metabotropic)
what is 5-HT2 receptor family responsible for
mood, sleep, and higher cognition
what are 5-HT3 receptors responsible for
nausea
who discovered acetylcholine as a NT
Otto Loewi
where are cholinergic neurons found
many cholinergic (ACh-containing) neurons are found in nuclei within basal forebrain
ionotropic, nicotinic receptors
excitatory and drive muscle contractions
metabotropic, muscarinic receptors
either excitatory or inhibitory and are crucial in cognitive processes
mesostriatal pathway
a projection of the dopaminergic path that originates in the midbrain around the substantia nigra and projects axons to the basal ganglia.
mesolimbocortical pathway
a projection of the dopaminergic path that originates in the midbrain (ventral tegmental area) and projects to various locations in the limbic system and cortex. this path is especially important in processing reward
what are the two branches of the dopaminergic projection that we are focusing on
- mesostriatal pathway
- mesolimbocortical pathway
dopamine
**has fewer neurons associated
receptors are involved in complex behaviors, including motor function, reward, and higher cognition.
where do serotonergic fibers originate
**has fewer neurons associated (even fewer than dopamine)
serotonergic fibers originate from neurons sprinkled along the midline of the midbrain and brainstem in the raphe nuclei
serotonin 5-HT where are they produced? what do they contribute to?
A synaptic transmitter that is produced in the raphe nuclei and is active in structures throughout the cerebral hemispheres.
participates in the control of all sorts of behaviors: mood, vision, sexual behavior, anxiety, sleep, and many other functions.
where are cell bodies located for norepinephrine
many of the brain’s noradrenergic neurons have their cell bodies in two regions of the brainstem and midbrain: the locus coeruleus and the lateral tegmental area
They participate in the control of behaviors ranging from alertness to mood to sexual behavior (and many more).
opioid peptides
- act as NTs
- a group of endogenous substances with actions that resemble those of opiate drugs like morphine
endogenous
growing or originating from within an organism.
gut peptides
hormones and neuropeptides that affect digestion, appetite, and gut motility
can act as synaptic transmitters, and they are often co-localized with classical transmitters
oxytocin, orexin, and vasopressin
peptide hormones, such as oxytocin, orexin, and vasopressin, are produced by the hypothalamus and pituitary. These peptides are involved in an astonishing variety of functions, ranging from basic housekeeping like urine production through to higher-level functions like memory, pair-bonding
gas NT
nittrous oxide
how are gasotransmitters different from neurotransmitters
- Gasotransmitters are produced in cellular locations other than the axon terminals, especially in the dendrites, and are not held in vesicles; the substance simply dissolves in cellular fluids and diffuses out of the neuron as it is produced
- gases can function as retrograde transmitters: by diffusing from the postsynaptic neuron back to the presynaptic neuron
agonist
A substance that mimics or boosts the actions of a transmitter or other signaling molecule
A substance that mimics the normal action of a neurotransmitter on its receptors by binding to the receptors and activating them is thus a receptor agonist.
antagonist
A substance that blocks or attenuates the actions of a transmitter or other signaling molecule
Drugs classified as receptor antagonists bind to receptors but do not activate them—instead, they block the receptors from being activated by their normal neurotransmitter
What are the three main categories of presynaptic drug effects?
Effects on transmitter production, effects on transmitter release, and effects on transmitter clearance.
How can drugs affect neurotransmitter production?
They can inhibit enzymes needed for synthesis, block axonal transport of raw materials, or interfere with neurotransmitter storage in synaptic vesicles.
Give an example of a drug that affects neurotransmitter storage.
Reserpine interferes with the storage of neurotransmitters in synaptic vesicles.
How do local anesthetics like procaine (Novocain) affect synaptic transmission?
They block sodium channels, preventing action potentials and thus stopping neurotransmitter release.
What deadly toxin blocks action potentials throughout the body?
Tetrodotoxin (found in puffer fish)
How does Botox (botulinum toxin) affect neurotransmitter release?
It blocks acetylcholine (ACh) release, causing local muscle paralysis.
What role do autoreceptors play in regulating neurotransmitter release?
They monitor neurotransmitter release and provide feedback to the presynaptic neuron.
How does caffeine affect neurotransmitter release?
Caffeine blocks adenosine autoreceptors, preventing inhibition of neurotransmitter release and increasing alertness.
Why is neurotransmitter clearance important?
It allows new transmitter release to have an effect and prevents excessive neurotransmitter buildup.
NT clearance is the general removal of NTs from synaptic cleft (reuptake is a specific type of clearance)
What are two ways drugs can alter neurotransmitter clearance?
Blocking reuptake or inhibiting enzymes that break down neurotransmitters.
How do reuptake inhibitors work?
They prevent the presynaptic neuron from reabsorbing neurotransmitters, allowing them to remain in the synapse longer.
What are the two major types of postsynaptic drug effects?
Direct effects on neurotransmitter receptors and effects on intracellular processes.
What are first-generation antipsychotics, and how do they work?
First-generation antipsychotics (e.g., chlorpromazine, haloperidol) act as dopamine D2 receptor antagonists, reducing hallucinations and delusions in schizophrenia
What is the difference between first- and second-generation antipsychotics?
First-generation antipsychotics target dopamine D2 receptors, while second-generation antipsychotics also block certain serotonin receptors, aiming to alleviate both positive and negative symptoms of schizophrenia.
What are some potential future directions for antipsychotic drug development?
Third-generation antipsychotics are being researched to target neurotransmitters like glutamate and oxytocin for improved schizophrenia treatment.
How do monoamine oxidase inhibitors (MAOIs) work?
MAOIs block the enzyme monoamine oxidase, preventing the breakdown of dopamine, serotonin, and norepinephrine, leading to increased synaptic transmission and improved mood.
What are tricyclic antidepressants, and how do they function?
Tricyclic antidepressants (e.g., imipramine) block the reuptake of neurotransmitters like serotonin and norepinephrine, increasing their availability in synapses.
What is the mechanism of selective serotonin reuptake inhibitors (SSRIs)?
SSRIs (e.g., fluoxetine, citalopram) specifically block serotonin reuptake, increasing its concentration in the synapse to treat depression and anxiety.
How do serotonin-norepinephrine reuptake inhibitors (SNRIs) differ from SSRIs?
SNRIs (e.g., venlafaxine) block the reuptake of both serotonin and norepinephrine, making them useful for depression and anxiety disorders.
What are benzodiazepines, and how do they work?
Benzodiazepines (e.g., alprazolam, lorazepam) bind to GABA_A receptors, enhancing the inhibitory effects of GABA, reducing neuronal excitability, and alleviating anxiety.
Why were barbiturates replaced by benzodiazepines for anxiety treatment?
Barbiturates, though effective, have a high risk of overdose and addiction, whereas benzodiazepines are safer and more specific in their action.
What are newer alternatives to benzodiazepines for anxiety treatment?
Newer anxiolytics include drugs affecting serotonin neurotransmission and hormones that interact with GABA receptors.
What is the primary active compound in opium, and what does it do?
Morphine is the main active compound in opium, acting as a powerful analgesic (painkiller) but also carrying a high risk of addiction.
Name some synthetic opioids and their relative strength.
Synthetic opioids include oxycodone, heroin (diacetylmorphine), and fentanyl, with fentanyl being 30-40 times more potent than heroin.
What brain region is crucial for opioid pain relief?
The periaqueductal gray (PAG) in the midbrain has a high concentration of opioid receptors and is a key site for opioid-induced pain relief.
What are endogenous opioids, and what are their functions?
Endogenous opioids (e.g., endorphins, enkephalins, dynorphins) are naturally occurring peptides in the brain that bind to opioid receptors to modulate pain and mood.
How do opioid antagonists like naloxone (Narcan) work?
Naloxone rapidly binds to opioid receptors, blocking the effects of opioids and reversing overdoses.
What are the two main cannabinoid receptors?
CB1 and CB2 receptors.
What is the most studied endocannabinoid, and what does it do?
Anandamide; it influences mood, pain relief, nausea, blood pressure, and glaucoma.
What receptors does nicotine act on?
Nicotinic acetylcholine (ACh) receptors.
What brain area is involved in nicotine addiction?
The ventral tegmental area (VTA).
What is the primary mechanism of cocaine’s action?
It blocks the reuptake of monoamine neurotransmitters (dopamine and norepinephrine), increasing their effects.
Why is crack cocaine more addictive than powder cocaine?
It is smoked, allowing it to enter the brain more rapidly.
How do amphetamines affect neurotransmitter release?
They increase neurotransmitter release and block reuptake/metabolism, leading to potent synaptic effects.
How does the DSM-5 define addiction?
As “substance use disorder” (SUD), which can range from mild to severe depending on the number of criteria met.
How many DSM-5 criteria must be met for a mild substance use disorder diagnosis?
Two or three criteria.
What is the moral model of addiction?
It blames substance use on weak character and lack of self-control, but has limited success in treatment.
What is the disease model of addiction?
It views addiction as a medical condition requiring treatment but lacks a clear biological cause.
What is the physical dependence model of addiction?
It argues that people continue drug use to avoid withdrawal symptoms, though it does not explain initial addiction.
What is the positive reward model of addiction?
It suggests that drug use is reinforced by pleasurable effects, leading to compulsive use.
What is the function of the eye?
The eye captures light at the front and projects detailed images onto the retina, a layer of neurons at the back, where light is converted into neural signals in a process called transduction.
What is transduction in vision?
Transduction is the process by which the retina converts light into neural signals that can be interpreted by the brain.
Why is a sharp optical image important for good vision?
A sharp optical image ensures that light from a single point on an object forms a single point on the retina, preventing blurring and ensuring clarity.
What part of the eye is primarily responsible for focusing light onto the retina?
The cornea, the transparent outer layer of the eye, refracts light and is the main component for focusing.
What is refraction in the context of vision?
Refraction is the bending of light as it passes through different media, such as from air into the cornea, which helps focus light onto the retina.
How does the lens contribute to vision?
The lens fine-tunes the image on the retina by changing shape, a process controlled by the ciliary muscles.
What is accommodation in vision?
Accommodation is the process by which the lens changes shape to focus on objects at different distances.
What causes farsightedness (presbyopia)?
Aging reduces the elasticity of the lens, making it harder to focus on close objects. People compensate by holding objects farther away or using reading glasses.
What is myopia (nearsightedness), and what causes it?
Myopia occurs when the eyeball is too long, causing the lens and cornea to focus light in front of the retina instead of directly on it. It is corrected with lenses that adjust refraction.
Why is the image on the retina upside down and reversed?
The biconvex shape of the lens bends light in such a way that the visual scene is inverted. The brain processes and corrects this orientation.
What controls the movement of the eye?
The extraocular muscles, three pairs of muscles that extend from the eyeball to the skull, allow the eyes to track and fixate on objects.
What is the retina?
The retina is a thin layer of neurons at the back of the eye where visual information begins to be processed.
What are photoreceptors, and what are the two types?
Photoreceptors are sensory neurons that detect light. The two types are rods (sensitive to low light) and cones (detect color and require more light).
What neurotransmitter changes occur in photoreceptors when exposed to light?
Unlike typical neurons, rods and cones decrease their neurotransmitter release when exposed to light, generating graded potentials instead of action potentials.
What are bipolar cells and their function?
Bipolar cells receive input from rods and cones and transmit signals to ganglion cells, which form the optic nerve and send information to the brain.
What is the function of horizontal and amacrine cells?
Horizontal cells modulate interactions between photoreceptors and bipolar cells.
Amacrine cells connect bipolar cells and ganglion cells, refining visual processing.
what forms the optic nerve
The axons of ganglion cells form the optic nerve, which transmits processed visual data to the brain.
What is convergence in the visual system?
Convergence refers to multiple rods sending signals to a single ganglion cell, increasing sensitivity in low light but reducing detail perception.
What is a receptive field in the visual system?
A receptive field consists of the stimulus features that excite or inhibit a sensory cell.
How do photoreceptors respond to light?
At rest, rod and cone photoreceptors release glutamate. Light hyperpolarizes photoreceptors, reducing glutamate release.
How do on-center bipolar cells respond to glutamate?
Glutamate inhibits on-center bipolar cells. Light reduces glutamate release, exciting these cells.
How do off-center bipolar cells respond to glutamate?
Glutamate excites off-center bipolar cells. Light reduces glutamate release, inhibiting these cells.
Why are they called on-center and off-center bipolar cells?
On-center bipolar cells are excited when light is turned on in their receptive field center. Off-center bipolar cells are excited when light is turned off in their receptive field center.
How do bipolar cells influence ganglion cells?
Bipolar cells release glutamate, always depolarizing ganglion cells. On-center bipolar cells excite on-center ganglion cells, and off-center bipolar cells excite off-center ganglion cells.
What do ganglion cells report to the brain?
They fire nerve impulses to report “light” or “dark” to higher visual centers.
What is the structure of ganglion cell receptive fields?
They have a concentric structure with a central area and a surrounding ring, leading to two types: on-center/off-surround and off-center/on-surround.
How do these receptive fields affect ganglion cell activity?
Uniform illumination has little effect, but a well-placed small spot of light in the receptive field significantly alters activity.
This is because the center of a cell’s receptive field and its surround have antagonistic effects on each other.
Do neurons in the lateral geniculate nucleus (LGN) have similar receptive fields?
Yes, LGN neurons also have concentric on-center/off-surround or off-center/on-surround receptive fields.
What is lateral inhibition?
Lateral inhibition occurs when sensory receptor cells inhibit the reporting of information from neighboring receptor cells.
How does lateral inhibition affect brightness perception?
It enhances contrast at edges, making darker edges appear darker and lighter edges appear lighter.
What is an example of lateral inhibition in vision?
Ganglion cells at the edge of a dark band are inhibited by neighboring photoreceptors exposed to lighter areas, making the dark edge appear even darker.
Why do identical gray patches appear different in brightness perception experiments?
The brain assumes light sources come from above, influencing how it interprets brightness and shading.
how many rods vs. cones do we have
rods: 100 million
cones: 4 million
whats the difference in sensitivity between rods vs cones
rods: high (low light)
cones: low (needs bright light)
whats the difference in color vision between rods vs cones
rods: no color vision
cones: can detect color
whats the difference in location between rods vs cones
rods: outside fovea (none inside)
cones: concentrated in fovea (some outside fovea too)
whats the difference in acuity between rods vs cones
rods: low
cones: high
whats the difference in response time between rods vs cones
rods: slow
cones: fast
Why do objects appear to have different colors?
Objects appear colored based on the wavelengths of light they reflect. Our eyes detect these reflected wavelengths, which our brain interprets as different colors.
What is the visible spectrum of light for humans?
The human visual system detects wavelengths between 400 and 700 nanometers (nm), perceiving shorter wavelengths as blue and longer wavelengths as red.
What are the three dimensions of color perception?
Brightness - Varies from dark to light.
Hue - The color itself (e.g., blue, green, red, etc.).
Saturation - Ranges from rich, vivid colors to gray.
How do different wavelengths correspond to color perception?
Short wavelengths (~400-500 nm) = Blue/Violet
Medium wavelengths (~500-600 nm) = Green/Yellow
Long wavelengths (~600-700 nm) = Orange/Red
How does lighting affect color perception?
Under dim light, blues appear more vivid, while reds appear duller.
Colors can also appear different based on surrounding objects due to contrast effects.
What is the trichromatic theory of color vision?
Proposed by Hermann von Helmholtz, it suggests that humans have three types of cones in the retina, each sensitive to different wavelengths: blue (short), green (medium), and red (long).
What is the opponent-process theory of color vision?
Proposed by Ewald Hering, it suggests that color vision is based on three opposing pairs of colors: blue vs. yellow, red vs. green, and black vs. white. This explains phenomena like afterimages.
How many types of cone photoreceptors do humans have?
Humans have three types of cones:
S-cones (short-wavelength, blue-sensitive)
M-cones (medium-wavelength, green-sensitive)
L-cones (long-wavelength, red-sensitive)
Do cones have narrow spectral tuning to specific colors?
No, cone pigments broadly overlap in sensitivity, meaning multiple cones respond to various wavelengths, allowing the brain to interpret colors through comparative activation.
What happens when cone photoreceptors absorb light?
Light hyperpolarizes the cone cells, leading to reduced glutamate release, which alters the activity of downstream bipolar and ganglion cells.
How does lateral inhibition influence color perception? What cells does it occur between?
Lateral inhibition, occurring through interactions between bipolar and horizontal cells, enhances contrast at edges, making colors and brightness differences more distinct.
Why do two areas reflecting the same wavelength sometimes appear different?
Context effects and assumptions made by the brain (e.g., overhead lighting assumptions) influence perceived color, as seen in brightness illusions.
What are color afterimages, and how are they explained?
Color afterimages occur when staring at a color for a prolonged time leads to cone fatigue, causing the brain to perceive the opposing color when looking away.
What are the two main visual processing streams in the brain?
The ventral stream (the “what” pathway) is responsible for object recognition (perception-based vision), while the dorsal stream (the “where” pathway) is responsible for spatial awareness and guiding movements (action recognition).
What evidence supports the existence of these two streams?
Studies of monkeys and humans with brain lesions show distinct deficits: ventral stream damage impairs object recognition, while dorsal stream damage affects visually guided actions.
What is an example of ventral stream damage?
Patient D.F., who suffered carbon monoxide poisoning, lost the ability to recognize objects but could still reach for and grasp them correctly.
What happens when the dorsal stream is damaged?
Individuals with optic ataxia struggle to use vision to guide movements but can still recognize objects.
How do fMRI studies contribute to understanding visual processing?
fMRI scans show distinct activation patterns in the lateral occipital cortex for object recognition and in the parietal lobe for visually guided movements.
What brain region is specialized for face recognition?
The fusiform gyrus in the ventral stream is crucial for identifying faces.
What environmental factor is linked to increased myopia (nearsightedness)?
Studies suggest that low exposure to outdoor sunlight during childhood leads to excessive eyeball growth, increasing myopia risk.
What study supports the role of outdoor exposure in myopia prevention?
A study compared Chinese children in Singapore (who spent ~30 min outdoors daily) and Sydney (who spent ~2 hrs outdoors daily). Myopia rates were 30% in Singapore vs. 3% in Sydney.
What practical intervention helps reduce childhood myopia?
Encouraging children to spend recess outdoors has been shown to reduce myopia development
What is amblyopia?
A condition where vision is weak in one eye due to improper visual development, often caused by misaligned eyes (lazy eye).
How is amblyopia treated?
Treatment often involves patching the stronger eye, forcing the weaker eye to develop properly.
What is the critical period for treating amblyopia?
Early childhood is the most effective time for intervention, as the brain’s visual system is still plastic.
What are the four types of chemical communication in the body?
Synaptic communication, endocrine communication, pheromone communication, and allomone communication
How does endocrine communication differ from synaptic communication?
Endocrine communication involves hormones released into the bloodstream to affect distant target organs, while synaptic communication involves neurotransmitters traveling across a synapse to affect a nearby neuron.
What is pheromone communication?
It is the release of chemicals outside the body to affect other individuals of the same species, such as ants leaving pheromone trails to food sources.
What is allomone communication?
It is chemical signaling between species, such as flowers releasing allomones to attract pollinators. (one species attracting another species)
What are the three main classes of hormones?
Peptide hormones, amine hormones, and steroid hormones.
What are peptide hormones made of?
Short chains of amino acids, similar to small proteins.
How are amine hormones different from peptide hormones?
Amine hormones are smaller and derived from a single modified amino acid.
What are steroid hormones derived from?
Cholesterol, giving them a four-ring carbon structure.
Name three peptide hormones.
Insulin, oxytocin, and growth hormone (GH).
Give two examples of amine hormones.
Epinephrine (adrenaline) and melatonin.
Name two steroid hormones.
Testosterone and cortisol.
How do peptide and amine hormones act on cells?
They bind to receptors on the cell surface and activate second messengers inside the cell.
How do steroid hormones act on cells?
They pass through the cell membrane, bind to receptors inside the cell, and influence gene expression.
Why do steroid hormones act more slowly than peptide and amine hormones?
They involve gene transcription and protein synthesis, which take more time.
Can a single hormone have multiple effects on different organs?
Yes, hormones can cause different effects depending on receptor type and cell context.
Give an example of a hormone with multiple effects.
Testosterone stimulates sperm production in the testes and promotes muscle growth and beard development.
Why is the pituitary gland called the “master gland”?
It regulates many other endocrine glands.
What structure connects the hypothalamus to the pituitary gland?
The pituitary stalk (infundibulum).
What are neuroendocrine cells?
Cells that receive synaptic input like neurons but release hormones into the bloodstream instead of neurotransmitters.
What two hormones are stored in the posterior pituitary?
Oxytocin and vasopressin (ADH).
Where are oxytocin and vasopressin produced?
In the hypothalamus, specifically the supraoptic and paraventricular nuclei.
What is the function of oxytocin?
It stimulates uterine contractions, milk ejection, and social bonding.
What is vasopressin’s main function?
It regulates water balance and blood pressure.
What is the first stage in bringing males and females together?
Sexual attraction.
How is sexual attraction linked to reproductive readiness in many species?
It is closely synchronized with physiological readiness to reproduce.
What cues often attract male mammals to females?
Female odors that reflect estrogen levels.
Why does female sexual attractiveness peak alongside fertility?
Because estrogen secretion is associated with the release of eggs.
What term describes a female displaying behaviors that promote sexual interaction?
Proceptive.
What are some proceptive behaviors in female rats?
Ear wiggling and a hopping and darting gait.
What is copulation also known as?
sexual intercourse
What does copulation involve in mammals?
Intromission (insertion of the penis into the vagina) followed by stimulation and ejaculation.
What is the refractory phase?
The period after copulation during which animals will not mate again.
What is the Coolidge effect?
The phenomenon where animals resume mating sooner when presented with a new partner.
When is a female said to be sexually receptive?
When she is willing to copulate, also known as being “in heat” or “in estrus.”
Why are most species seasonal breeders?
Because females are receptive only when mating is likely to produce offspring.
What are postcopulatory behaviors?
Behaviors occurring after copulation, such as parental behaviors or mechanisms preventing other males from mating.
What is copulatory lock?
A phenomenon where the male’s penis swells after ejaculation, temporarily preventing withdrawal and blocking other males from mating.
What type of fertilization do mammals, birds, and reptiles use?
Internal fertilization.
How do female rats attract males for mating?
By releasing pheromones and displaying proceptive behaviors.
What is the stereotyped posture female rats assume when receptive?
Lordosis.
What role does testosterone play in male sexual behavior?
It drives male interest in copulation and is necessary for mounting and ejaculation.
What happens when a male rat is castrated (removal or supression of testicles)?
He stops ejaculating and eventually ceases mounting receptive females.
What hormones activate female rat copulatory behaviors?
Estrogen and progesterone.
What brain region is crucial for female sexual receptivity in rats?
The ventromedial hypothalamus (VMH).
What brain region controls male copulatory behaviors?
The medial preoptic area (mPOA).
How does the vomeronasal system influence male sexual behavior?
It detects pheromones, which stimulate male arousal and erections.
What are common maternal behaviors in rats?
Nest building, crouching over pups, cleaning, retrieving, and nursing.
What hormone is crucial for maternal behaviors?
A combination of estrogens, progesterone, oxytocin, and prolactin.
How does pregnancy prepare rats for maternal care?
Pregnancy hormones shape the brain to display maternal behaviors before exposure to pups.
What distinguishes human sexuality from most other species?
The diversity of reproductive behaviors.
Who pioneered the scientific study of human sexual behavior?
Alfred Kinsey.
What are the four phases of human sexual response, according to Masters and Johnson?
Excitement, plateau, orgasm, and resolution.
What is a key difference in the sexual response of men and women?
Men have a refractory phase after orgasm, while many women can have multiple orgasms.
What determines whether a mammalian embryo develops as male or female?
The presence of an X- or Y-bearing sperm at fertilization.
What is the role of the SRY gene?
It directs the development of testes in XY individuals.
What happens if an XY individual has a dysfunctional SRY gene?
The gonads develop into ovaries, leading to a female phenotype.
What is the first effect of sex chromosomes on development?
They determine whether the indifferent gonads become ovaries or testes.
How do fetal testes influence male development?
They secrete testosterone, androgen, and anti-müllerian hormone (AMH), which promote male reproductive structures.
What happens in the absence of testosterone, androgen, and AMH?
The embryo develops female reproductive structures by default.
What is the role of dihydrotestosterone (DHT)?
It masculinizes external genitalia, forming the scrotum and penis.
What happens if an embryo lacks 5-alpha-reductase?
Testosterone is not converted to DHT, leading to incomplete masculinization of external genitalia.
What is Turner syndrome?
A condition where an individual has only one X chromosome, leading to underdeveloped ovaries.
What is congenital adrenal hyperplasia (CAH)?
A disorder where XX individuals are exposed to excess androgens before birth, leading to intersex characteristics.
What is androgen insensitivity syndrome (AIS)?
A condition where XY individuals cannot respond to androgens, leading to female-typical external anatomy but no uterus or ovaries.
What is 5-alpha-reductase deficiency?
A condition where testosterone is not converted to DHT, leading to ambiguous genitalia at birth but masculinization at puberty.
What is the organizational hypothesis?
It proposes that early exposure to androgens masculinizes the brain, while absence leads to feminization.
What is the sexually dimorphic nucleus of the preoptic area (SDN-POA)?
A brain region larger in male rats than in females, influenced by androgen exposure at birth.
How does testosterone affect neural development in rats?
It is converted to estrogen in the brain, masculinizing specific regions.
What is the spinal nucleus of the bulbocavernosus (SNB)?
A group of motor neurons in the spinal cord that control penile muscles, present in males but lost in females.
How do androgens contribute to the survival of SNB motor neurons?
Androgens act on BC muscles to prevent their degradation, which in turn preserves the innervating SNB motor neurons.
What is the role of androgen in adult SNB neurons?
In adulthood, androgens cause SNB neurons to grow and help form new spinal connections.
What is the human equivalent of the SNB motor neuron system found in rodents?
In humans and other nonrodents, the BC motor neurons are located in Onuf’s nucleus.
How does maternal behavior affect the development of the SNB system in male rats?
Mothers lick male pups more due to detecting androgen metabolites, which helps masculinize their spinal cord.
How does maternal licking influence female rat behavior later in life?
Females that were licked more as pups show enhanced estrogen and oxytocin sensitivity and become more attentive mothers.
How does social influence interact with hormonal signaling in human gender development?
Social influences amplify subtle sex differences caused by prenatal androgens, leading to gender-specific behaviors.
What evidence suggests that prenatal androgens influence human sexual orientation?
Women with congenital adrenal hyperplasia (CAH) exposed to androgens in utero exhibit more masculine behaviors and are more likely to identify as lesbian.
What phenomenon in the Dominican Republic provides insight into gender development?
“Guevedoces” are raised as girls but develop male genitalia at puberty and later adopt male behaviors, suggesting prenatal androgens influence gender identity.
How does the fraternal birth order effect relate to male sexual orientation?
The more older biological brothers a boy has, the higher the probability that he will be gay, possibly due to maternal immune responses.
What brain structure has been linked to sexual orientation in men?
The third interstitial nucleus of the anterior hypothalamus (INAH-3) is larger in heterosexual men than in gay men.
What prenatal biological markers are associated with lesbian orientation?
Lesbians tend to show markers of higher prenatal androgen exposure, such as altered ear sounds, eye-blink patterns, and finger length ratios.
How does identical twin research contribute to understanding sexual orientation?
Identical twins are more likely to share the same sexual orientation than fraternal twins, indicating a genetic component, but not the sole determining factor.
Why is sexual orientation unlikely to be a conscious choice?
Most gay and straight people report that their romantic and sexual interests have been consistent since childhood, and no reliable method has been found to change orientation.
