Reticular Formation, Hypothalamus, and Limbic System

The reticular formation is a network of neurons located deep within the brainstem. It is divided into two parts:

• Upper part: located in the midbrain and pons, plays a role in activating consciousness and wakefulness.

• Lower part: located in the medulla and pons, controls brainstem reflexes such as eye movement, posture, respiration, cardiovascular function, and salivation.

Overall functions of the reticular formation:

• Maintain cortical tone.

• Regulate spinal reflexes.

• Serve as the center for autonomic reflexes.

Damage to the reticular activating system leads to excessive sleep.

Neurotransmitters in the reticular formation:

• Adrenaline is released from the reticular activating system.

• Noradrenaline is produced from the locus coeruleus.

• Dopamine is produced from the substantia nigra.

• Serotonin is produced from the raphe nuclei.

• Acetylcholine is produced from the gigantocellular nucleus.

The descending reticular formation plays a role in regulating spinal reflexes and maintaining muscle tone.

Sleep is divided into two stages:

• Slow-wave sleep: deep sleep.

• Rapid eye movement sleep: dream sleep.

The hypothalamus is the center of the limbic system, playing a crucial role in regulating physiological functions:

• Autonomic function:

• Anterior part: parasympathetic center.

• Posterior part: sympathetic center.

• Thermoregulation:

• Anterior part: heat-loss center.

• Posterior part: heat-conservation center.

• Antidiuresis:

• ADH is released from the supraoptic and paraventricular nuclei.

• Regulation of uterine and mammary gland activity:

• Oxytocin is released from the supraoptic and paraventricular nuclei.

• Hunger center: ventromedial nucleus.

• Thirst center: lateral part.

• Lateral hypothalamus: related to hunger, thirst, and anger.

The third ventricle region is related to fear and punishment response.

The posterior and anterior hypothalamus are related to sexual behavior.

The limbic system consists of structures such as:

• Hippocampus: involved in memory and learning.

• Amygdala: related to emotion and aggression.

• Limbic cortex: connects the cerebral cortex to subcortical limbic structures, controlling behaviors like taste, smell, hearing, thinking, sensory integration, and motor coordination.

Role of the limbic system in emotion:

• Formation and expression of emotions: Amygdala and hippocampus.

• Reducing the intensity of emotional responses: Septum.

• System of hesitation and doubt: Septum, hippocampus, prefrontal cortex.

Effects of drugs on the nervous system:

• Reserpine inhibits NE and 5HT, causing depression.

• L-Dopa is used in the treatment of Parkinson’s disease, causing the release of DA in the brain, which may induce schizophrenic symptoms.

Note: This article is just a brief introduction to the reticular formation, hypothalamus, and limbic system. To understand these structures and functions better, you need to consult further specialized materials.