Biopsychology: Homeostasis, Hunger, Temperature, Sleep, and Thirst

Comprehensive practice flashcards detailing concepts in biological psychology including homeostasis mechanisms, negative and positive feedback systems, hunger pathways, body temperature regulation, sleep stages and disorders, circadian rhythms, and osmotic versus hypovolemic thirst.

How is homeostasis defined?

The body's processes to physiologically regulate its internal environment in response to fluctuations that occur in the internal or external environment.

What is homeostatic imbalance, and what consequences can it have?

The inability to maintain internal balance, which affects normal body functions and can lead to disease, disorder, or death.

What causes hypothyroidism, and what are its symptoms according to the lecture?

It occurs when the body fails to produce or regulate thyroid hormones. Failed thyroid hormone homeostasis causes weight gain, lack of concentration, and fatigue.

Which brain structure automatically runs most homeostatic processes?

The hypothalamus.

What is negative feedback in the context of homeostasis?

A mechanism in which the body senses a change and attempts to counteract or reverse that unwanted change.

What are three physiological examples of negative feedback?

Blood pressure regulation, body temperature regulation (sweating when hot, shivering when cold), and fluid balance (urinating after consuming excess water).

How does positive feedback homeostasis function?

Its processes amplify themselves and become progressively stronger until the initiating trigger or cause is eliminated.

How do labor and delivery exemplify a positive feedback loop?

Cervical stretching sends nerve signals to the brain to release oxytocin, which triggers uterine contractions. Increased stretching prompts greater oxytocin release and stronger contractions until delivery ends the stimulus.

How does hemostasis (blood clotting) demonstrate positive feedback?

Activated clotting factors at a bleeding wound summon additional clotting factors continuously until the bleeding ceases.

What are the three structural components of a homeostatic system?

The receptor (sense organ that detects a stimulus), the control center/brain (evaluates input against a set point and decides action), and the effector (muscle or gland executing the command).

What is the normal physiological range for human blood pH, and what are the terms for deviations from this range?

Normal blood pH is $7.35 - 7.45$. A pH below $7.35$ is acidosis, and a pH higher than $7.45$ is alkalosis.

Which stomach-derived hormone primarily stimulates appetite and promotes meal initiation?

Ghrelin.

What are four gastrointestinal and endocrine satiety-related signals that decrease hunger?

Cholecystokinin (CCK), peptide YY, GLP-1, and insulin.

Where is leptin produced, where does it act, and what is its homeostatic role?

Leptin is produced mainly by body fat tissue, acts in the hypothalamus to reduce food intake, and provides long-term information about body energy stores.

What distinguishes homeostatic eating from non-homeostatic eating?

Homeostatic eating is driven by biological energy and nutrient requirements, whereas non-homeostatic eating is motivated by reward, taste, stress, food availability, emotions, social contexts, and learned habits.

What characterizes Prader-Willi Syndrome?

A genetic condition marked by the permanent loss of the satiety response, causing life-threatening hyperphagia because the brain fails to register fullness.

What is hypothalamic obesity?

Unchecked hunger and rapid weight gain caused by hypothalamic damage or tumors disrupting the brain's detection of leptin and insulin.

What is congenital leptin deficiency?

A rare genetic mutation that prevents the body from synthesizing leptin, causing the brain to perceive constant starvation and driving extreme early-onset overeating.

Anorexia nervosa

severe homeostasic dysregulation where the brain adapts to starvation by blunting normal orexigenuc (hunger-stimulating) signals or misinterpreting internal metabolic feedback.

Leptin Resistance and Obesity

the gut signals fullness but the brain fails to listen, leaving hunger signals permanently active.

What is the normal set-point for human body temperature, and which hypothalamic structure controls it?

$37\,^\circ\text{C}$, regulated by the thermoregulatory center in the hypothalamus.

What three physiological mechanisms does the body deploy to conserve and generate heat when exposed to cold?

Cutaneous vasoconstriction (reducing skin heat loss), contraction of erector muscles (raising hairs to trap insulating air), and shivering (involuntary muscle contractions that boost metabolic heat).

What physiological changes occur to cool the body when it is hot?

Relaxation of erector muscles, vasodilation (increasing blood flow to skin to dissipate heat), and sweat gland secretion (cooling through evaporation).

How do homeotherms/endotherms differ from poikilotherms/ectotherms?

Homeotherms/endotherms (such as mammals and aves) generate internal body heat, whereas poikilotherms/ectotherms (such as reptiles and amphibians) cannot regulate internal heat and depend on external environmental sources.

Which sleep scientist is noted for research on sleep's effects on the brain and body?

Matthew Walker.

What is the recommended daily sleep duration for healthy adults?

$7 - 9\,\text{hours}$.

How long does a standard human sleep cycle last, and how many cycles occur in a typical night?

One cycle lasts approximately $90 - 120\,\text{minutes}$, with $4 - 5$ cycles occurring per night.

What percentage of adult sleep is spent in NREM Stage 2, and what brain wave patterns characterize it?

About $45\%$ of sleep; characterized by slowing brain waves interrupted by short bursts of brain activity known as sleep spindles and K-complexes.

Which stage of sleep shown in the EEG diagram is defined by the appearance of sleep spindles and K-complexes?

Stage N2 sleep.

What are the primary electrophysiological and functional features of NREM Stage 3 sleep?

Deepest NREM sleep dominated by slow, strong delta waves, comprising approximately $25\%$ of adult sleep, and critical for physical repair and immune function.

What defines REM sleep in terms of brain activity and subjective experience?

Rapid eye movements, high brain activity resembling wakefulness (beta waves), and vivid dreaming; comprises roughly $25\%$ of adult sleep.

What is sleep debt?

The difference between the amount of sleep an individual needs and the actual amount of quality sleep received.

Insomnia

Difficulty sleeping.

Hypersomnolence

excessive sleepiness

Parasomnia

Unusual behavior during sleep. (Sleep walking)

What is oneirology?

The scientific study of dreams.

How do G. William Domhoff and Adam Schneider define a dream?

A report of a memory cognitive experience that occurs under conditions most frequently produced during the state of sleep.

Normal dreams

reflect daily experiences.

Nightmares

Disturbing dreams causes fear and anxiety.

Recurring dreams

Similar dreams.

Prophetic or precognitive dreams

a dream that seem to predict what will happen later.

Daydreams

imagined situatios while you are awake.

What is a lucid dream?

A dream state in which the dreamer actively realizes they are dreaming while the dream is still happening.

What is a false awakening dream?

A phenomenon where an individual dreams that they have woken up, when in reality they are still asleep.

Where is the master biological circadian clock located in the human brain?

The suprachiasmatic nucleus (SCN), located within the hypothalamus.

How does environmental light modulate the circadian rhythm through the SCN?

The suprachiasmatic nucleus is sensitive to light and uses environmental light signals to adjust clock gene expression and coordinate 24-hour cycles throughout the body.

What distinguishes Delayed Sleep-Wake Phase Disorder (DSWPD) from Advanced Sleep-Wake Phase Disorder (ASWPD)?

DSWPD involves a sleep-wake schedule that is significantly delayed compared to average timings, whereas ASWPD involves going to bed and waking much earlier than average.

What are the two major fluid compartments of the human body?

Intracellular fluid (ICF; fluid inside cells) and extracellular fluid (ECF; fluid outside cells, comprising blood plasma and interstitial fluid).

What is the primary difference in etiology between osmotic thirst and hypovolemic thirst?

Osmotic thirst is triggered by increased plasma osmolality leading to cellular dehydration, while hypovolemic thirst is triggered by a drop in extracellular fluid volume (plasma/blood volume).

What is normal plasma osmolality, and what percentage increase is required to evoke osmotic thirst?

Normal plasma osmolality is $280 - 295\,\text{mOsm/kg}$; a $1 - 2\%$ increase above normal is sufficient to trigger osmotic thirst.

Why do solutes like NaCl, sucrose, and mannitol stimulate osmotic thirst, whereas urea does not?

NaCl, sucrose, and mannitol are non-permeating (effective) solutes that remain in the ECF and draw water out of cells by osmosis. Permeating (ineffective) solutes like urea freely cross cell membranes without establishing a gradient or shrinking cells.

Which circumventricular structures house the osmoreceptors that detect osmotic thirst?

The organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), and median preoptic nucleus (MnPO), all featuring fenestrated capillaries lacking a typical blood-brain barrier.

Where is vasopressin (ADH) synthesized and released, and how does it act on the renal tubules?

Synthesized in the hypothalamus and released from the posterior pituitary; it binds V2 receptors in kidney collecting ducts to insert aquaporin-2 channels, increasing water reabsorption.

Why does the conscious sensation of thirst diminish minutes after drinking, before intestinal absorption occurs?

Receptors in the mouth, throat, and upper stomach signal the brain that water has arrived, rapidly suppressing thirst and vasopressin secretion to prevent overhydration.

What differentiates Central Diabetes Insipidus from Nephrogenic Diabetes Insipidus?

Central DI is caused by insufficient synthesis or release of vasopressin (ADH), whereas Nephrogenic DI occurs when the kidneys fail to respond to circulating ADH.

What blood sodium threshold defines hypernatremic dehydration, and what are its potential consequences in vulnerable individuals?

Blood sodium exceeding $145\,\text{mmol/L}$; in vulnerable individuals, severe hypernatremic cellular shrinkage can cause confusion, seizures, coma, or death.

What magnitude of plasma volume reduction is typically required to activate hypovolemic thirst?

A reduction of greater than $10\%$ ($> 10\%$).

Where are low-pressure and high-pressure cardiovascular baroreceptors located?

Low-pressure baroreceptors are in the great veins and right atrium; high-pressure baroreceptors are in the carotid sinus and aortic arch.

What is the sequence of enzymatic conversions in the renin-angiotensin-aldosterone system (RAAS)?

Renin from the kidney converts liver-derived angiotensinogen into angiotensin I, which is subsequently converted into angiotensin II by angiotensin-converting enzyme (ACE) primarily in the lungs.

What three major actions does Angiotensin II exert to correct hypovolemia?

Acts on AT1 receptors in the SFO and OVLT to stimulate thirst and ADH release, promotes vasoconstriction to elevate arterial pressure, and stimulates adrenal aldosterone secretion to increase renal sodium reabsorption.

Why is oral rehydration solution (ORS) effective in managing hypovolemic shock in cholera or severe gastroenteritis?

It contains water, sodium, and glucose; intestinal cotransport of glucose facilitates rapid sodium and water absorption, directly replacing lost ECF volume and electrolytes.

How does Addison's disease induce hypovolemia?

Adrenal insufficiency leads to a deficiency of aldosterone and cortisol, impairing the kidneys' capacity to reabsorb sodium and causing secondary water loss.