Exam 2 Study Guide: Chapters 4, 5, and 6

Vocabulary flashcards covering neurochemistry, drug actions, neural development, and visual processing based on Chapters 4 through 6 lecture notes.

Neurotransmitters

Chemical messengers that engage in wiring transmissions by acting on neurons in their own immediate vicinity (generally at a synapse), typically released from an axon terminal and crossing the synaptic gap.

Acetylcholine (ACh)

The first chemical messenger to be discovered; a major small-molecule neurochemical used at the neuromuscular junction, in the autonomic nervous system, and in the central nervous system.

Cholinergic neurons

Neurons that use acetylcholine (ACh) as their major neurochemical.

Norepinephrine

A major monoamine and catecholamine neurochemical involved in arousal, vigilance, and CNS activation, converted from dopamine by the action of an enzyme.

Serotonin

A major monoamine and indoleamine neurochemical synthesized in the raphe nuclei from the amino acid tryptophan (via tryptophan hydroxylase) that participates in the regulation of mood, sleep, aggression, social status, and appetite.

Dopamine

A major monoamine and catecholamine neurochemical implicated in motor control, reward, psychosis, planning, and reinforcement, operating via pathways such as the nigrostriatal and mesolimbic pathways.

Glutamate

A small-molecule amino acid neurochemical and the most common excitatory neurochemical in the CNS, used by as many as $90\%$ of synapses in the human brain to strongly depolarize neurons.

GABA (Gamma-aminobutyricacid)

A major inhibitory amino acid neurochemical serving as the primary inhibitory neurochemical of the CNS, involving as many as $40\%$ of synapses in the central nervous system.

Nicotinic receptor

A fast postsynaptic ionotropic receptor found at the neuromuscular junction, autonomic nervous system, and CNS that responds to both acetylcholine (ACh) and nicotine.

Muscarinic receptor

A slower postsynaptic metabotropic receptor found in heart muscle and other smooth muscles that responds to both acetylcholine (ACh) and muscarine.

Agonists

Substances that boost, help, or promote the activity of a neurochemical by acting like a neurotransmitter, blocking reuptake, or increasing release.

Antagonists

Drugs that reduce the activity of a neurochemical by reducing release, blocking receptor sites, or increasing metabolism.

Placebo effects

Perceived benefits from inactive substances or procedures, often influenced by a user's expectations, experiences, and motivations.

Tolerance

The process in which more of a drug is needed to produce the same effect, or when drug effects are lessened as a result of repeated administration due to changes at the synapse.

Withdrawal

Symptoms that occur when psychoactive substances are no longer administered, are discontinued, or are administered in smaller quantities.

Addiction

A compulsive craving for drug effects or experience in spite of negative consequences, characterized by a compulsive need to readminister a drug that overwhelms behavioral control and distorts reward systems.

Psychoactive drugs

Substances that cross the blood-brain barrier, affect mood, and change consciousness.

Stimulants

A class of drugs that increase alertness and mobility/movement, including caffeine, nicotine, cocaine, amphetamines, and ecstasy.

Opioids

Substances derived from opium poppy resin (containing morphine and codeine) that interact with endorphin receptors to produce profound pain relief and a remarkable sense of euphoria.

Alcohol

A substance whose main effect is acting as an agonist at the GABA receptor, while also stimulating dopaminergic pathways (craving and addiction) and antagonizing NMDA glutamate receptors.

Tetrahydrocannabinol (THC)

The most important psychoactive compound among over $300$ in cannabis, which produces mild euphoria and perceptual distortion by binding to endogenous cannabinoid receptors (anandemide and 2-AG).

Neural tube

A developmental structure formed by the embryonic neural plate (progressing from neural plate to neural groove to neural tube) that develops into the brain and spinal cord, persisting in the adult brain as ventricles and the center of the spinal cord.

Ventricular zone

The embryonic region where the birth of new neurons and glia occurs.

Migration

The movement of stem cells (daughter cells formed by mitosis) to their mature locations to form the cerebral cortex in an inside-out fashion, guided by radial glia.

Radial glia

Special glia that radiate from the ventricular layer to the outer margins of the cerebral cortex like spokes of a wheel, serving as pathways for migrating neurons.

Synaptogenesis

The formation of synapses that takes place after neuron cell bodies reach their final locations and aggregate with other cell bodies.

Neurites

Branches projecting off the neuronal cell body that will eventually develop into axons and dendrites.

Growth cones

Swellings at the tips of growing axons or dendrites equipped with sensory and motor abilities that guide neurites to form synaptic connections with target neurons.

Apoptosis

Programmed cell death affecting as many as $40\%$ to $75\%$ of cells during migration, beginning prenatally and continuing until the age of $2$ years.

Pruning

The developmental process in which functional synapses are maintained while nonfunctional synapses degenerate, reducing the overall number of functional synapses.

Neurotrophins

A class of chemicals, including nerve growth factor (NGF), released by target cells that protect presynaptic neurons from apoptosis and ensure their survival.

Myelination

A structural and functional maturational process in the nervous system that progresses from the spinal cord toward the forebrain (bottom to top), with sensory systems myelinating before motor systems.

Critical period

A developmental window during which experience is influential and after which it has little to no effect, initiated in the visual system by the maturation of GABA circuits.

Spina bifida

A condition resulting in mobility problems that occurs when the neural tube fails to close completely during development.

Phenylketonuria (PKU)

A heritable condition caused by a recessive allele resulting in a lack of liver enzymes necessary to convert the amino acid phenylalanine into tyrosine.

Primary visual cortex

The visual processing area located at the back of the occipital lobe, damage to which leads to blindness or scotomas.

Scotomas

Specific areas of blindness resulting from damage to the visual cortex.

Visual agnosia

A condition where an individual is unable to recognize a visual object.

Prosopagnosia

A condition also called face blindness, characterized by an inability to recognize the faces of familiar people.

Lateral geniculate nucleus (LGN)

A visual structure with connections to the hypothalamus (regulating circadian rhythm) and the superior colliculus (guiding movements of the eyes and head).

Optic chiasm

The anatomical junction where optic nerve tracts cross before proceeding onward to the thalamus.

Somatosensory cortex

Located in postcentral gyrus

Primary auditory cortex

axons from neurons in cochlea project to

Inferior colliculi

Thalamus

Primary cortex in temporal lobe

Periaqueductal gray area

Large # of opioid receptors

Stimulation of PAG reduces sensation of pain

Nociceptors

Pain receptors respond to injury, heat, chemicals. Free never endings that respond to pain

Phantom limb pain

Pain that is perceived as arising from a missing body part

Loss of input in plasticity of touch

Synesthesia

A blending of the senses, experience of one sense triggers an experience of another sense “cross overs”

Olfactory pathways

Sense of smell, stimuli only sense that bypasses thalamus, has wide connections with cortex and limbic system.

Olfactory pathways

Sense of smell, stimuli only sense that bypasses thalamus, has wide connections with cortex and limbic system.

Myastenia gravis

Autoimmune disorder, acetylcholine receptors on muscle fibers are attacked

Extreme muscle weakness, slurred speech,

Amyotrophic lateral sclerosis (ALS)

Scarring, motor neurons in the spinal cord and brain stem degenerate, muscles that rely on these neurons breakdowns, more common in later life

Parkinson’s disease

Difficulty initiating movement, degeneration of substantial nigra, less dopamine activity in basal ganglia, tremor in resting body parts, loss of balance, autonomic disturbances, cognitive decline late in disease

Huntington’s disease

100% genetics disorder, begins in middle age, dominant 50% of offspring will have disease, repeats chromosome 4, excess protein cause cell death in basal ganglia