biolpsy_07

Lecture Overview

• Biological Psychology 1

• Lecture 07: Homeostatic Regulation

• Presented by: Dr. Richárd Reichardt

• Contact: reichardt.richard@ppk.elte.hu

Homeostasis

• Living organisms strive to maintain a constant internal environment.

• Consistency is essential for biological processes.

• Negative Feedback Mechanism:

  • Temperature above set point: heating off

  • Temperature below set point: heating on

Homeostatic Regulation Process

• Change in variable is detected by a receptor.

• Receptor communicates the change to a control center.

• Control center issues a command to an effector to return the variable to its set point.

Body Temperature Regulation

• Humans as homeotherms maintain body temperature at about 36.5–37 °C (97.7–98.6 °F).

• Two primary factors influencing body heat:

  • Muscle function

  • Protein structure (heat enhances contraction speed but can destabilize proteins)

Receptors for Heat Detection

• Specific ion channels open at certain temperatures, critical for the thermoregulatory process.

Preoptic Area

• Primary control center for thermoregulation found in the hypothalamus.

• Other brain structures also contribute to the regulation of body temperature.

Effectors of Thermoregulation

• Various organs respond to body temperature changes.

• Adjusting the diameter of cutaneous blood vessels influences heat exchange with the environment.

Regulation of Body Water Content

• Consistency in the volume and solutes of the fluid bathing cells is essential.

• Body fluids categorized into intracellular and extracellular compartments.

• Decrease in fluid volume prompts thirst response.

Homeostatic Regulation of Thirst

• Water loss triggers mechanisms to stabilize blood pressure and induce thirst.

• Thirst encourages fluid intake.

Energy Regulation

• Food intake provides essential chemicals and energy for bodily functions.

• Hormones Involved:

  • Leptin: signals satiety

  • Ghrelin: signals hunger

Allostatic Regulation of Body Weight

• Hypothalamic lesions can alter the body weight set point.

• Allostasis:

  • Describes homeostasis with a variable set point.

  • It offers a better understanding of energy regulation than traditional homeostasis.

Changes in Weight Set Point

• Resetting the body weight set point is a gradual process, typically taking years.

• Basal metabolism decreases with lower energy intake, which makes weight loss difficult through dieting alone.

What is Sleep?

• Sleep is a recurrent daily behavior with unclear functions, warranting deeper study across species.

• Importance of clear behavioral indicators for sleep research.

Behavioral Indicators of Sleep

• Characterized by:

  • Decreased movement

  • Decreased responsiveness

  • Further deprivation exacerbates these states

Sleep in the Animal Kingdom

• All species, from Cnidarians to Drosophila, exhibit sleep-like states.

• Even bacteria exhibit circadian rhythms, highlighting sleep's evolutionary importance linked to natural light patterns.

Importance of Sleep for Nervous System Function

• Nervous systems evolved in contexts where circadian rhythms were already present.

• Sleep deprivation drastically affects cognition and can lead to severe consequences, including psychosis or death.

Regulation of Sleep

• Increased wakefulness leads to increased sleep pressure with occasional periods of alertness despite prolonged wakefulness.

• Borbely Model of Sleep Regulation: Discusses two regulatory mechanisms of sleep.

Homeostatic Process (Process S)

• Longer wakefulness leads to greater sleep needs.

• Wakefulness acts as a homeostatically regulated variable.

• Chemical Signal:

  • Adenosine likely serves as the signal, with receptors not yet precisely identified.

  • Control center located in the hypothalamus.

Circadian Process (Process C)

• 18th Century experiment by De Mairan studied Mimosa pudica to determine internal vs. light-driven rhythms.

Circadian Output via Suprachiasmatic Nucleus

• Hypothalamic nucleus generates neural activity with a circadian rhythm, influenced by gene expression rhythms.

Influence of Light on Circadian Rhythms

• The retinohypothalamic tract impacts circadian activity, demonstrating the influence of light conditions.

Sleep and Waking Mechanisms

• The ascending arousal system discovered in 1949 regulates wakefulness.

• Inhibiting these systems leads to drowsiness and sleep.

Neurophysiology of Sleep

• A hypothalamic nucleus inhibits neuromodulator systems for sleep onset.

• Orexinergic hypothalamic nucleus:

  • Critical for stabilizing the waking state.

  • Damage leads to narcolepsy.

Sleep Stages

• Distinct stages of sleep include Slow-Wave Sleep (SWS) which increase with sleep pressure.

• REM sleep characterized by dreaming and muscle atonia.

Sleep Cycle

• Sleep consists of cyclic patterns (1-2-3-REM) repeated 4-5 times during a night.

• SWS decreases and REM sleep increases with sleep cycles.

Closing Remarks

• Thank you for your attention!

• Next class: Sensory Systems I.