Neurons, Neural Communication, and Consciousness

Comprehensive practice flashcards covering cellular neurobiology, action potentials, synaptic transmission, sleep architecture, sleep disorders, dreaming theories, and psychoactive drug mechanisms.

What is the structural difference between nerves and tracts?

Nerves are bundles of axons located outside the brain and spinal cord in the peripheral nervous system, whereas tracts are bundles of axons located inside the brain and spinal cord.

What are the three primary types of neurons and their respective directional functions?

Sensory (afferent) neurons carry information toward the brain and spinal cord, motor (efferent) neurons carry signals away from the central nervous system to muscles and glands, and interneurons pass information between neurons within the central nervous system.

How do oligodendrocytes and Schwann cells differ in where they form myelin?

Oligodendrocytes produce the myelin sheath in the central nervous system (CNS), whereas Schwann cells form myelin in the peripheral nervous system (PNS).

What role does the neurilemma play in peripheral nerve recovery?

The neurilemma is the outer layer of Schwann cells that protects the axon and provides a tunnel that assists damaged peripheral nerves in regrowing.

How do multiple sclerosis and myasthenia gravis differ in the mechanisms that cause muscle impairment?

Multiple sclerosis damages and breaks down myelin in the central nervous system, whereas myasthenia gravis is an autoimmune condition where the immune system attacks acetylcholine receptors directly on muscle tissue.

What is the resting potential of a neuron, and how are potassium and sodium ions distributed at rest?

The resting potential is approximately $-70\,mV$, maintained with a higher concentration of potassium ions ($K^+$) inside the cell and a higher concentration of sodium ions ($Na^+$) outside the cell.

What does the all-or-none principle state regarding neural impulses?

It states that a neuron either fires completely or does not fire at all, meaning every action potential generated in a specific neuron has identical strength.

What two mechanisms clear neurotransmitters from the synaptic gap following transmission?

Reuptake (where the sending neuron reabsorbs the neurotransmitter) and enzyme breakdown (where an enzyme breaks the neurotransmitter down into recyclable parts).

How does curare produce muscle paralysis?

Curare functions as an antagonist that binds to and blocks acetylcholine (ACh) receptors on skeletal muscles, preventing motor signals from causing contractions.

What role does dopamine play along the mesolimbic reward pathway?

Dopamine is released in the nucleus accumbens during the anticipation of pleasurable stimuli, driving motivation, reinforcement, and reward-seeking behaviors.

How do GABA and glutamate differ in their regulatory effects on the central nervous system?

GABA is the primary inhibitory neurotransmitter that calms neural activity and prevents overexcitation, whereas glutamate is the primary excitatory neurotransmitter involved in learning, memory, and long-term potentiation (LTP).

How do Substance P and endorphins interact during pain transmission?

Substance P transmits pain signals from the body to the central nervous system, while endorphins reduce pain sensations partly by inhibiting the release of Substance P.

What is the difference between an agonist and an antagonist in psychopharmacology?

An agonist mimics or increases the activity of a neurotransmitter by binding to its receptors or blocking reuptake, whereas an antagonist binds to receptor sites without activating them, blocking the endogenous neurotransmitter from binding.

What is neurogenesis, and where does it notably occur in adult human brains?

Neurogenesis is the generation of new neurons, which occurs in adult humans primarily within the hippocampus.

What is synaptic pruning?

The developmental process where neural connections that are regularly stimulated are strengthened, while unused connections weaken and are eliminated.

What distinguishes circadian, ultradian, and infradian biological rhythms?

Circadian rhythms operate on an approximately $24\text{-hour}$ cycle, ultradian rhythms recur multiple times within a $24\text{-hour}$ period (such as the $90\text{-minute}$ sleep cycle), and infradian rhythms span longer than a single day (such as the menstrual cycle).

Who recorded the first human EEG, and who discovered REM sleep using EEG in 1953?

Hans Berger recorded the first human EEG in the 1920s, and Eugene Aserinsky and Nathaniel Kleitman discovered REM sleep in 1953.

What are the frequency ranges and behavioral states associated with beta, alpha, theta, and delta waves?

Beta waves ($15\text{ to }30\,Hz$) occur during alert wakefulness or anxiety; alpha waves ($7\text{ to }12\,Hz$) occur during relaxed drowsiness; theta waves ($4\text{ to }7\,Hz$) occur during Stages 1 and 2 of sleep; and delta waves ($\le 4\,Hz$) dominate deep Stage 3 sleep.

How does the suprachiasmatic nucleus (SCN) regulate melatonin production?

Light-sensitive retinal cells send signals to the SCN in the hypothalamus, which directs the pineal gland to suppress melatonin in daylight and stimulate its release when darkness falls.

What two electrophysiological hallmarks appear during NREM Stage 2 (N2) sleep?

Sleep spindles (short bursts of rapid, rhythmic activity linked to memory processing) and K-complexes (isolated, high-voltage waves that often occur in response to external environmental stimuli).

Why is REM sleep classified as paradoxical sleep?

The brain exhibits high electrical activity resembling waking beta waves, yet the body experiences REM paralysis because the brain stem blocks motor signals from reaching the muscles.

How does the composition of a $90\text{-minute}$ sleep cycle change across a night of sleep?

NREM Stage 3 deep sleep dominates early in the night and gradually diminishes or disappears, while REM sleep episodes become progressively longer toward the morning.

How does adenosine cause sleep pressure, and by what mechanism does caffeine counteract it?

Adenosine builds up progressively throughout waking hours to inhibit neural activity and produce drowsiness; caffeine acts as an adenosine antagonist, binding to and blocking adenosine receptors to prevent sleepiness.

What neurochemical deficiency is responsible for narcolepsy and its associated cataplexy?

A deficiency in orexin (also known as hypocretin), a neurotransmitter synthesized in the brain that promotes and sustains wakefulness.

What are the key differences between night terrors and nightmares regarding sleep stage and recall?

Night terrors occur during NREM Stage 3 deep sleep early in the night and leave little to no conscious memory, whereas nightmares occur during REM sleep later in the night and are typically remembered upon waking.

How did Sigmund Freud distinguish manifest content from latent content in dreams?

Manifest content refers to the consciously remembered narrative storyline of a dream, while latent content represents the hidden, unconscious, and symbolic meaning of the dream.

What is the biological explanation of dreams according to the activation-synthesis theory?

Formulated by J. Allan Hobson and Robert McCarley, it states that the pons generates spontaneous neural signals during REM sleep (activation), and the cerebral cortex synthesizes these signals by assembling them into a narrative (synthesis).

How does alcohol alter the balance of inhibitory and excitatory neurotransmission?

Alcohol enhances the inhibitory effects of GABA while suppressing the excitatory effects of glutamate, producing central nervous system depression, motor impairment, and slowed reaction times.

How do opioid drugs trigger dopamine surges in the nucleus accumbens?

Opioids act as endorphin agonists, binding to endorphin receptors and suppressing the GABAergic interneurons that normally restrain dopamine release, thereby causing dopamine to surge.

What is the synaptic mechanism of action of cocaine?

Cocaine blocks the reuptake transporters for dopamine, serotonin, and norepinephrine, forcing these neurotransmitters to accumulate and remain active in the synaptic gap.

What natural neurotransmitter system does the active ingredient in cannabis (THC) target?

THC binds to cannabinoid receptors in the brain that normally bind anandamide, a neurotransmitter involved in appetite, memory, pain, and mood.

What did Bruce Alexander conclude from his late-1970s 'Rat Park' experiment?

Rats placed in a socially enriched, low-stress environment consumed significantly less morphine solution than rats in isolated cages, indicating that environmental stress and isolation heavily mediate addiction vulnerability.