Functions of thalamus, hypothalamus & limbic system

🧠 Lecture Notes: The Limbic System

🖇 I. Definition & Main Concept

📌 The Limbic System is the involuntary (unconscious) system responsible for extreme emotional reactions, such as:

• Excessive joy (too much happiness)
• Excessive sadness or anger

📌 Its main role is to maintain balance between these extreme emotions — a process similar to homeostasis, keeping internal emotional stability.

📌 Example:

• ↑ Pleasure center → Laughter
• ↑ Anger center → Fear
• Defect: Abnormal behavior (e.g., laughing loudly at a funeral).

🟣 II. Location & Main Structures

📌 Located around (beneath) the cerebral cortex (subcortical area) — described as surrounding the cortex like a tail.

📌 Main parts include:

• Cingulate gyrus
• Parahippocampal gyrus
• Amygdaloid nuclei (Amygdala) — related to smell and emotion

🟠 III. Major Functions of the Limbic System

1️⃣ Olfaction (Sense of Smell)

• The most primitive function.
• Controlled by the amygdaloid nuclei.

2️⃣ Regulation of Endocrine Function

• Controls hormone secretion related to circadian rhythm:
• • Melatonin: Active at night 🌙
  • Cortisol: Active during the day ☀️

3️⃣ Autonomic Regulation (Body Control)

• Maintains heart rate, blood pressure, and body temperature.
• Keeps internal physiological balance.

4️⃣ Regulation of Food Intake

• Contains:
• • Feeding center (stimulates eating)
  • Satiety center (stops eating)
• Defects →
• • Hyperphagia: Excessive eating
  • Amnephagia: Refusal to eat

5️⃣ Sexual Activity

• Controls sexual behavior and function in both males & females.
• Proven in experiments on animals (e.g., dogs).

6️⃣ Personality, Behavior, and Motivation

• Governs emotions, motivation, and behavior patterns.
• Example:
• • In experiments, removing the limbic system in a mother cat caused her to eat her kittens’ food instead of feeding them → loss of maternal motivation.

7️⃣ Circadian Rhythm

• Helps regulate daily biological cycles (sleep–wake pattern, hormones).

📌 IV. Key Concepts Emphasized by the Instructor

🖇 1. Defining Role:

• The limbic system controls extreme emotions and maintains emotional balance (homeostasis).

🖇 2. Emotion–Reaction Link:

• ↑ Pleasure → Laughter
• ↑ Anger → Fear

🖇 3. Major Functional Domains:

• Olfaction
• Autonomic control (HR, BP, Temp)
• Feeding & Satiety centers
• Motivation and behavior

🖇 4. Defects and Examples:

• Emotional imbalance: Laughing at inappropriate times.
• Feeding disorder: Hyperphagia or amnephagia.

🚨 V. Clinical & Conceptual Highlights

• Acts as the emotional and motivational center of the brain.
• Strongly connected with the hypothalamus → links emotion with body regulation.
• Damage causes abnormal emotions, behavior, or appetite.
• Essential for maintaining emotional homeostasis and personality.

ال thalamus مع محاضرة ال basal ganglia