Psychopharmacology: Neurochemicals and Vision

• These notes cover psychopharmacology and vision.
• Exocytosis is the process of releasing neurotransmitters.

Neurochemicals

• These are not the chemicals themselves, but what is released.
• Neurotransmitters have direct synapses (axons/neurons) and utilize wire transmission.
  • This allows for more control and constrains how far the neurotransmitter goes.
• Neuromodulators are non-direct, releasing neurochemicals into the cerebrospinal fluid (CSF).
  • Volume transmission allows these chemicals to spread more globally.
• Neurohormones are non-direct and transmitted through the blood.

Types of Neurochemicals (Ways to classify them)

Size

• Small molecules consist of 1-2 amino acids.
• Neuropeptides are larger, containing 3-36 amino acids.
• Gasotransmitters are gases that float around, are built-in soma, float out of the membrane, float into other cells without activating receptors.

Small-Molecule

• Typically synthesized in the axon terminal buttons.
• Small molecules are easy to make.
• Vesicles are reused.
• Small amounts of Ca2+ are needed for exocytosis, the release of neurotransmitters.
  • This pushes vesicles to the membrane.
• Large amounts are needed to activate postsynaptic receptors.

Neuropeptides

• Typically synthesized in the soma and have to be sent to terminal buttons.
• Need more Ca2+ to push the vesicle to the membrane wall.
• Vesicles are used only once.
• Large amounts of Ca2+ for exocytosis.
• Small amounts are needed to activate postsynaptic receptors.

Receptors on a Neuron

• Two types exist in dendrites.

• An ionotropic receptor is the typical doorway.

  • The lock is on the door itself, so the gate opens when neurotransmitters bind.
  • Inhibition occurs when chlorine enters the cell, while excitation occurs when sodium enters.

• A metabotropic receptor functions differently.

  • It has a receptor site on one side which triggers G-proteins on another side, which are released and open their own ion channels.
  • Slower than ionotropic but is able to cover more area because of G-protein diffusion.

• A neurotransmitter doesn't just do one thing, it participates in various mechanisms.

• Loewi discovered acetylcholine.

• Acetylcholine (ACh) isn't just in one area because it doesn't do just one thing.

  • Cholinergic neurons are bundles of neurons.
  • They are in basal forebrain, brainstem, and the septal area and are sent and released to the cerebral cortex, hippocampus, hypothalamus, and amygdala, which all contribute to perceptual learning.

• ACh is the primary neurotransmitter at the neuromuscular junction.

  • Muscle contraction occurs due to ACh presence.

• ACh enzyme is vital to autonomous nervous system function.

• Nicotine mimics acetylcholine (ACh) and can selectively select where the drug goes.

• The autonomic system isn't really a pendulum, as the peripheral system calms.

Monoamines (Small-Molecules)

• There are 6 monoamines.
  • 6-36 amino acid chains comprise them.
  • These include catecholamines (3), indoleamines (2), and histamine.
• Catecholamines are synthesized from the amino acid tyrosine.
  • These include dopamine, norepinephrine, and epinephrine.

Dopamine

• It is a neurotransmitter involved with motivated behaviors and the processing of rewards.
• Rats nucleus stimulated in rats, so dopamine is released.
• When rats were given a button for dopamine, they kept pressing it until they died.
• Dopamine is related to addiction.

Dopamine Pathways

• Nigrostriatal System: Voluntary movement, Parkinson's disease.
• Mesolimbic System: Emotional processing (Amygdala), LTMC hippocampus), Rewards.
• Mesocortical System: Planning (Frontal lobe), Schizophrenia, Attention Deficit Hyperactivity Disorder (ADHD).

Norepinephrine

• Increases arousal and vigilance.
• Serves as the primary neurotransmitter in the sympathetic nervous system.
  • Located in the medulla, pons, hypothalamus, (biological drives-hunger, sleep, etc.).

Epinephrine

• Neurohormone.
• Regulates eating and blood pressure.
• Found in the Medulla.
• Adrenaline Rush.

Indoleamines: Serotonin

• Synthesized from tryptophan (comes from diet, increases serotonin).
  • Found in grains, meat, and dairy products.
• Low levels of serotonin don't cause depression, whereas high levels don't get rid of depression.
• Located in Enteric Nervous System (Digestive Tract).
  • 95% control neurons involved with digestion.
• Also in the raphe nuclei of the pons, medulla, & cerebellum.
  • 5% in CNS.
• Regulates mood, sleep, appetite, aggression, & dominance.
  • Social dominance.
• Leads to carbohydrate consumption (high carb foods = comfort food).
  • Leads to self-medication as feelings will fade and the need to "feel better".
  • Major Depressive Order.
• Low Serotonin - If struggling TODAY give SSRI, but should be short term, & get them into cognitive behavioral therapy.
• Imbalance is due to a perception issue, imbalances in the brain come from the way people view the world, not the other way.

Indoleamines: Melatonin

• Neurohormone.
• Located in the Pituitary Gland.
• Controls Sleep.
• Melatonin just makes the consumer unconscious, but doesn't give you quality sleep.
• Melatonin is a supplement, not medicine, so there are no FDA regulations.
  • It should be temporary.
• Anxiety some issues for sleep and melatonin doesn't do anything for anxiety.

Histamine

• Controls reactions of the body (like allergic reactions).

Amino Acids

• Include Glutamate, gaba, Glycine, and 5+ more.

Amino Acids: Glutamate

• It is the major excitatory neurotransmitter in the CNS.
• Extended action can be toxic to neurons (poisonous).
• Widely distributed in the CNS.
• Functions for long-term memory.

Subtypes of Iontropic Glutamate Receptors

• Activate sodium channels producing EPSPs.

• AMPA (most common) receptors (glutamate activates these receptors lets Na+ in).

• Kainate.

• Iontropic/metatropic are subsets of ligand gates.

• Both voltage-gated dependent & ligand-dependent.

• NMDA (commy 1 to allow ca2+ in).

• Only opens with depolarization and glutamate occur.

  • AMPA receptors are ligand receptors that pair W/NMDA receptors
  • Na+ & Ca2+ Ca2+ (Ca2+ will make it supper positive, so nevron will grow more-long-term porentiation).

• Neurons doesn't influence intelligence; the connections (synapses) do.

• Glutamate can inhibit dopaminergic neurons.

Amino Acid: GABA

• Built/synthesized from givtamate.
• The major inhibitory neurochemical in the CNS.
• Widely distributed in the CNS.
• Controls mood and seizure threshold.
  • Can help calm down.
• Anything that fits into GABA can activate it (like lock that opens wwany key).
• GABA is inhibition, lets Chloride in (-), so no action potential.
• Ethanol is like GABA, can't mix w/antidepressents.
  • Reduces activity of the nervous system

Drug Actions at the Synapse

• Agonists enhance the activity of a neurotransmitter.
• Antagonists reduce the activity of a neurotransmitter ,NOT excitation or inhibition.
• Alcohol is GABA agonist.
  • Inhibition is even greater.
• Caffeine is adenosine antagonist, can fit in receptor but not activate it so adenosine can't go in then
• Tolerance: lessened effects as a result of repeated administration by higher dosage
• Withdrawal occurs when substance use is discontinvea,.
  • Is the opposite of the effects caused by the drug
• Addiction: compulsive need to use a drug repeatedly, changes in reward, impuises control, craving circuits, Dopamine

Psychoactive Drugs: Stimulants

• Increase alertness & mobility
• Ecstasy (MDMA): stimulates release of serotonin, oxytocin, norepinephrine, dopamine

Marijuana (Cannabis)

• Active ingredient THC looks like an endogenous cannabinoid receptor agonist.
• Affects the hippocampal & prefrontal cortex (memory & higher-order processing-fully developed pre-frontal cortex mid-20s).
• Mild euphoria, perceptual distortions, hallucinations, & depression.
• When legalized in States, there are more rates of schizophrenia, legalized for $ not science.
• It can be used w/chema to try & restore appetite, to give them the "munchies".
• Chronic use is once a week or mare.
• Use for sleep is so bad - just unconscious but not good sleep.
• Schizophrenia

Alcohol

• GABAA receptor agonist
• Stimulants dopaminergic reward pathways
• Rapid tolerance
• Damaging effects on health
• Only abt. half a glass of red wine is good-thins blood so takes Strain off heart, good for cholesterol, antioxidents

Ch. 5: Vision Notes

• Most important process for us-vision neurons take up 50% of the brain
• The brain "creates" vision, which is how we get illusions.

Sensation & Perception

• Sensation: the activation of sensory receptors.
• Transduction: to take one form of energy, convert to another form.
  • To transform "light for vibration, etc. to action potential".
• Perception: a process that the brain goes through where it takes different patterns of neural signals, & builds our external representations.
  • Sensation outside Stimuli transduction turned into wnar brain can understand perception is how brain interprets it.
• Electromagnetic Radiation: energy waves produced by the sun.
• Visible light:
  • Wavelength: the distance between successive peaks of a wave
    • Hue (color)
  • Amplitude: wave height
    • Intensity (brightness)
• Range of energy visible to humans falls between 400 $ 700 nanometers
• Infrared waves also known as heat
• Reflection -photons bounce off of it
• Absorption -photons absorbed
• Refraction: bend it in diff. direction
• Black: no color, Pigmentation is opposite of light-it consumes light
• White; all color
• Stigmatism: sclera mishapened.

Anatomy of Eye

• Iris: adjusts depending how much light is in the environment.

• Pupil: a hole, looks black as light can't exit it.

• Lens: adjusts for focus on different depths.

• Cornea bends light to allow us to focus

• Both eyes see the same thing.

• Visual info is processed contralaterally.

• Nasal info travels contralaterally, temporal info travels ispalaterally

• The retina recieves/is sensitive to light, composed of photoreceptors.

  • The fovea is straight back, high definition, is only 1% of the retina.

Fovea

• Central Vision: the ability to perceive visual stimuli focused on the macula of the retina.
  • Badly poorly lit area & bensly packed w/cones, color processing.
• The eye moves 3-4 times every second.

Periphery

• Peripherou vision: the ability to perceive visual stimuli that are off to the side while looking straight anead.
  • Better af seeing in the dark.
  • Area of retina excluding the fovea
  • Bad color vision
  • Covert (not directly at) attention
  • Better at detecting motion, even slight, even better than fovea.
  • More sensititve to light
• Cats don't have foveas, so they live in blurry life, but they are good at nunting so peripheral vision to see better movement

Photoreceptors

Cones

• 6 million.
• Photopic vision brignty lit conditions, highly colored
  • Bright light (brightly lit areas)
• Only in fovea of the retina

Rods

• 100 million

• Scotopic vision: vision in poorly lit condition.

  • Dim light.

• No rods in fovea, so only see in dark in peripheral vision

• NO color.

• Cones don't give color, so the viewer misses one and sees black & white

• Green is all 3 cone types activated at the same time

• Need 2 cone types to get color

Pathway of Vision

• Both eyes see the same thing.
• Visual info processed contralaterally.
  • The left half of vision processed in the right hemisphere
  • and the right half of vision processed in the left hemisphere.
• Nasal info travels contralaterally.
• Temporal info travels ispalaterally.
• Retina only sees in 2-dimension.
  • We only see in 3-dimension, which is why we have 2 eyes so we can "see" 3-dimension
• Lateral Geniculare Nucleus (LGN) is a part of the thalamus. Stacked layers.
• The lateral geniculate nucleus (LGN)
  • Receives 90% of optic tract axons. Goes to LGN then back to occipital lobe.
  • Six layers
    • Input from each eye
    • reflexual visual sometimes
• Superior Coliculi (IS)- Visual processing Cinferior coliculi (auditory), what you hear influences what you think you will see.
• The Striate Cortex.
• Primary Visual Cortex (aka striate cortex, aka V1).
  • Cortical receptive fields.
    • Simple cortical cells (only care abt. basic lines or shape, starts the illustration of vision).
      • Shape
    • Complex Cortical cells-Movement
• Visual Perception

Color Vision

• Trichromatic Theory - In the eye
• Tri (3) colors
• Color Vision (Herring) in the brain
  • Opponent process theory: green/red, blue/yellow, black/white
• Color Contrast: the same color appears different depending upon the context of surrounding colors.
• Color Constancy: colors look the same regardless of the type of light illuminating the object