BCS 110 Exam III Review

BCS 110 Exam 3 Review Session

Sleeping and Circadian Rhythms

Stages of Sleep

  • Awake

    • Low voltage, High frequency

    • Brain not in sync; Beta and Gamma waves

  • Pre-sleep

    • Brain begins to sync; intermittent Alpha waves

  • Stage 1 (Light Sleep)

    • Easy to wake; Theta waves

  • Stage 2

    • Sleep spindles: high-frequency bursts from Thalamus; K-complexes

    • Surges when Thalamus decides to wake or maintain sleep

    • Mainly Theta waves

  • Stage 3

    • Occasional Delta waves

  • Stage 4 (Deep Sleep/REM)

    • Predominantly Delta waves; dreaming occurs

    • Loss of muscle tone (paralysis)

    • Increased Beta and Gamma waves, resembling awake state

  • Emergent Stage 1

Course of Sleep

  • Sleep cycles occur approximately every 90 minutes: 1 -> 4 -> Emergent 1 -> 4, repeat

  • Deep sleep occurs within the first 1.5-3 hours of sleep

  • Sleepwalking occurs in stages 3 and 4, where muscles are paralyzed

  • Total awareness near the end of sleep; typically mistaken for deep sleep

  • Important to remember the sleep stage pattern!

Theories of Dreaming

  • Emergent Stage 1 Sleep

    • Everyone dreams; however, recollection varies

  • Subconscious Theory

    • Freudian theory: dreams reenact life events; largely disbelieved now

  • Activation-Synthesis Theory

    • Brain creates narrative based on random sensory inputs occurring during sleep

    • DLPFC contributes to story creation from received stimuli

Theories of Sleep

  • Recuperation Theory

    • Helps restore homeostatic balance (sodium reduction and nutrient restoration)

  • Evidence of Recuperation

    • Dolphins have uni-hemispheric sleep, indicating recuperation need

  • Adaptation Theory

    • Argues no homeostatic deficit; sleep has evolved as a protective mechanism

Sleep Deprivation

  • Sleep deprivation is personal; you can't 'bank' sleep

  • Long wakefulness can induce physiological and psychological disturbances, but varies

    • Physiological Evidence: reduced immunity, increased BP, lower body temp

    • Mood impacts: bad mood, lack of creativity, sleepiness; worsens with deep sleep deprivation

    • Potential positive role of REM: aids in memory processing and waking readiness

  • Logical and critical thinking often remain intact during sleep deprivation

Circadian Rhythms

  • Cycle approximately 24 hours, driven by zeitgebers (environmental cues)

  • Altered Cycles:

    • Free-running Cycle: Internal clock without environmental cues (~25 hours)

    • Jet Lag: shift in sleep caused by changes in zeitgebers (east vs. west travel)

  • Suprachiasmatic Nucleus (SCN)

    • Main circadian clock; responds to light input directly from retina

    • If SCN is removed, sleep cycles can shift dramatically

    • Transplanting SCN results in transplanting sleep cycles

Sleep-Wake Areas

  • Four key areas:

    • VLPO (Ventrolateral Preoptic Area): Initiates sleep

    • LHA (Lateral Hypothalamus): Initiates wakefulness

    • Rostral and Caudal nuclei: Regulate wake/sleep transitions

  • Sleep regulated by two neural processes: recuperation (need) and adaptation (urge)

Sleep Cycle: Wake

  1. LC releases norepinephrine to LHA and the brain

  2. LHA sends orexin back to support wakefulness

  3. LC sends GABA to suppress sleep centers

  4. SCN also sends GABA to suppress VLPO

Sleep Cycle: Sleep

  1. Adenosine levels rise throughout the day, pushing need for sleep

  2. SCN quiets at night as the pineal gland releases melatonin

  3. VLPO activates, inhibiting LC, leading to REM sleep activation

  4. LC disappears, REM activates; cycle continues

Sleep Drugs

  • Hypnotics: Activate GABA to inhibit wake centers; potential addiction

  • Antihypnotics: Reduce sleep time; stimulate sympathetic system

  • Chronobiotics: Alter circadian rhythms, melatonin supplements used for travel

Sleep Disorders

  • Insomnia: Difficulty falling or staying asleep

  • Sleep Apnea: Interrupted breathing during sleep

  • Hypersomnia / Narcolepsy: Excessive sleepiness during the day; often linked to deficiencies in orexin or norepinephrine

Hypothalamic Nuclei

  • SCN: Circadian clock

  • VLPO: Sleep regulation

  • LHA: Wakefulness regulation

Internal Regulation

Homeostasis

  • Maintains biological processes within narrow set ranges (set point vs. settling point)

  • Uses negative feedback to maintain stability

  • Hypothalamus: Key control center for these processes

Components of Integrated Response

  • Autonomic: Fast response adjusting nerve component balance

  • Endocrine: Slow response involving hormone release

  • Somatic: Motivating behavioral changes

Hypothalamus Functions

  • PVN: Initiates autonomic/endocrine responses; controls several hormones

    • Different components responding to fast and slow processes

Regulation Mechanisms

  • Autonomic responses: Body’s adjustments like sweating or shivering

  • Endocrine responses: Metabolic changes and thermoregulatory responses through hormonal adjustments

  • Somatic responses: Behavioral adjustments to internal and external temperatures

Body Temperature Regulation

  • Key neurons located in medial preoptic and anterior nuclei

  • These neurons integrate input on external/internal temperature

Osmotic and Hypovolemic Thirst

Osmotic Thirst Receptors

  • Monitors osmotic pressure; OVLT & SFO detect cell shrinkage

  • Response:

    • Endocrine: release of ADH to conserve water

    • Somatic: Generate the desire to drink

Hypovolemic Thirst

  • Baroreceptors: Detect pressure changes related to blood volume

  • Hypotension initiates conservation of water via nuclei activation in the hypothalamus

Energy Balance and Long-term Regulation

Energy Regulation

  • Brain must acquire glucose to produce ATP (energy)

  • Different states:

    • Prandial (fed state): storing glucose into glycogen

    • Fasting: breaking down stored molecules for energy

Long-term Regulation

  • Stable body weight linked to homeostatic and hedonic mechanisms

  • Lipostatic Hypothesis: The brain monitors body fat; leptin indicates fat energy storage

  • Implications of the hypothalamic nuclei regulation in energy needs

Neural Regulation of Appetite

Hunger Signals

  • Autonomic response to activating rest & digest functions

  • Endocrine adjustments lowering metabolic rate

  • Somatic: Initiate feeding behavior through orexin and MCH

Satiety Signals

  • Activate sympathetic system encouraging energy expenditure

  • Endocrine responses increasing metabolic rate

  • Somatic suppression of feeding behavior

Hedonic Mechanisms

  • Eating driven by emotional and motivational aspects linked to dopamine and serotonin

Eating Disorders

  • Anorexia: Low motivation and suppressed appetite

  • Bulimia Nervosa: Binge eating followed by purging due to high motivation

Hormones and Sex

  • Steroid Hormones: Three types influencing sexual behavior

    1. Androgens (testosterone)

    2. Estrogen (estradiol)

    3. Progestogens

Endocrine System Regulation

  • Gonadal hormone release controlled by hypothalamus actions

Hypothalamic Inputs

  • Arcuate Nucleus: Monitors male hormone levels

  • Anteroventral PN: Monitors female hormone levels; feedback mechanisms in place

Fetal Development

  • Gonadal Development: Influences from Sry gene determine male/female structures

  • Duct Development: Hormonal influences define external and internal structures

Hormonal Mechanisms of Sexual Behavior

  • Male and female sexual drive regulation influenced by testosterone and cyclical hormonal surges

Brain Mechanisms of Sexual Behavior

  • Reward circuits and areas of the brain involved in sexual behavior identification

Language and Speech

Language Features

  • Human language’s distinguishing features and comparison to animal communication

Language Evolution Theories

  • Various theories discussing origin and development of language abilities

Lateralization and Localization of Language

  • Areas of the cortex engaged in understanding and producing language

Wernicke-Geschwind Model

  • Processing spoken and written language through specialized pathways

Aphasias

  • Different types of language deficits based on brain damage locations

Language Localization

  • Evidence suggesting language areas are not strictly localized, but spread out

Other Languages and Dyslexia

  • Processing of sign language and bilingualism in the brain, alongside dyslexia observations

Learning and Memory

Memory Types and Definitions

  • Distinctions between short-term and long-term memory, including explicit and implicit categories

Memory Engram and Long-term Potentiation

  • Processes involved in memory formation and consolidation mechanisms

Alzheimer’s Disease & Memory

  • Effects on memory and types of memory affected by the disease

Conclusion on Memory Structures

  • Summary of the neuroanatomical basis for different types of memories bespeaking distinct brain regions.

  • Angular gyrus: translates the visual code from reading into an auditory code

  • Wernicke’s area: where meaning of words is understood; further translates thought processes into verbal responses

  • Arcuate fasciculus: fibers that connect Broca’s area to Wernicke’s area

  • Broca’s area: activates the appropriate programs that drive the neurons of the primary