RETICULAR FORMATION AND ITS LIMBIC SYSTEM

Reticular Formation

Is a set of interconnected nuclei that are located throughout the brainstem

Reticular Formation

Resembles a net (Reticular) that is made up of nerves cells and nerve fibers

Median Column, Medial Column, Lateral Column

Reticular Formation is divided into 3 longitudinal columns what are those

Raphe Nuclei

Other term for median column

Gigantocellular Reticular Nuclei

Other term for Medial Column

Parvocellular Reticluar Nuclei

Other term for Lateral Column

Median Column (Raphe Nuclei)

 consist of Intermediate-size neurons

 Are the place of synthesis of the neurotransmitter Serotonin, which plays

an important role in mood regulation

Medial Column (Gigantocellular Reticular Nuclei)

-contains large neurons

-Involved in motor coordination

Lateral Column (Parvocellular Reticluar Nuclei)

contains small neurons

1. Control of Skeletal Muscle, 2. Control of Somatic and Visceral Sensations, 3. Control of the Autonomic Nervous System, 4. Control of Endocrine Nervous system, 5. Influence on the biological clocks

Functions of Reticular Formation

Control of Skeletal Muscle

Influence the activity of alpha and gamma motor neurons (through Reticulospinal

Tract and Reticulobulbar Tract)

Control of Skeletal Muscle

Can maintain muscle tone, balance and reflexes

Control of Skeletal Muscle

Plays an important role in maintaining the tone of antigravity muscles during

standing

Control of Skeletal Muscle

important in controlling the muscles of facial expression associated with emotions

Control of Somatic and Visceral Sensations

Can influence all ascending pathways that pass to supraspinal levels

Control of Somatic and Visceral Sensations

The influence can be Facilitatory or Inhibitory

Control of Somatic and Visceral Sensations

Have a key role in the “Gating Mechanism” for control of pain perception

Reticular Activating System (RAS)

Responsible for arousal, sleep and level of consciousness

Reticular Activating System (RAS)

Contains circuit s that originate from several areas of the midbrain including the

midbrain reticular formation, and ascend to the cerebral cortex and thalamus

Reticular Activating System (RAS)

These pathways are predominantly associated with the neurotransmitter

Acetylcholine and Norepinephrine. which are thought to play important roles in

regulating the arousal and wakefulness

Alert, Lethargic, Obtunded, Stupor, Coma

Level of Consciousness

Alert

 Normal consciousness

 Appearance of wakefulness, awareness of the self and environment

Lethargic

 Consist of severe drowsiness

 Can be aroused by moderate stimulation and then drift back to sleep

Obtunded

 decrease alertness, slowed psychomotor responses

 needs repeated stimulation to maintain attention and response to

environment

Stupor

 sleep like state (not unconscious), with little or no spontaneous activity

 may only moan as a verbal response

Coma

cannot be aroused, no response to any stimuli

Ascending Arousal System

Other term for Reticular Activating System (RAS)

Limbic System

Group of structures that lie in the border zone between the cerebral cortex and the

hypothalamus

Limbic System

Involved in the control of Emotion, Behavior, Long term memory

Paleomammalian Cortex

Other term for limbic system

LIMBIC

border or margin

Anterior Thalamic Nucleus, Mamillary Bodies, Hypothalamus

Structure of limbic system from diencephalon

Cingulate Gyrus, Parahippocampal Gyrus, Hippocampus, Amygdaloid Body, Subcallosal, Fornix

Structure of limbic system from Cerebrum/ Cortical Area

Nucleus Accumbens, Septal Nucelus, Amygdala,

limbic system structure from Subcortical Area

Hippocampus, Dentate Gyrus, Parahippocampal Gyrus

Hippocampal Formation is compromise of

Anterior Thalamic Nucleus

Receive input from the mamillary bodies. Involved in memory processing

Mamillary Bodies

Part of the hypothalamus that receives signal from the hippocampus via fornix

and projects them to the thalamus.

Hypothalamus

regulates the number of autonomic processes.

Cingulate Gyrus

 Located immediately above the corpus callosum

 Is the integral part of the limbic system

 Involve in emotional functions and processing, learning and memory

depression and schizophrenia

Manifestation of Cingulate Gyrus

Parahippocampal Gyrus

Lies between the Hippocampal Fissure and Collateral Sulcus

Hippocampus

 Play a central role in the consolidation of new memories.

 Concerned with converting recent memory to long term memory

Anterograde Amnesia

Manifestation of Hippocampus

Anterograde Amnesia

difficulty in learning new information. Most

common in TBI.

Amygdaloid Body

 Resembles an Almond

 Situated partly Anterior and partly Superior to the tip of the Inferior Horn of

the Lateral Ventricle.

Fornix

white matter structure connecting the hippocampus with the other brain

structures particularly the mamillary bodies and septal nuclei.

Nucleus Accumbens

 Involved in reward, pleasure and addiction

 Also play a role in sexual arousal and a “high” derived from certain recreational

drugs.

Septal Nucleus

A set of structures that lie in front of the lamina terminalis, considered as

pleasure zone.

Amygdala

located deep within the temporal lobe and related with a number of

emotional processes

Amygdala

 Responsible for sexual desire

 Sex with anything

KLUVER BUCY SYNDROME

Amygdala Lesion: (+) Hyper sexuality known as

Hippocampal Formation

 A compound structure in the medial temporal lobe of the brain

 Comprised of Hippocampus, Dentate Gyrus, Parahippocampal Gyrus

Hippocampus

 Curved elevation of gray matter

 Resembles a sea horse in coronal section

EPENDYMA, Alveus

In hippocampus the convex ventricular surface is covered with _______, beneath which lies a thin layer of white matter called the_______

Alveus

consists of nerve fibers that originated in the hippocampus and

unite medially to form a bundle called the Fimbria

Molecular Layer, Pyramidal Layer, Polymorphic Layer

The Hippocampus has three layers

Molecular Layer

superficial, consists of nerve fibers and scattered small

neurons

Pyramidal Layer

consists of large pyramid shaped neurons

Polymorphic Layer

inner layer of hippocampus

Dentate Gyrus

Narrow, notched band of gray matter that lies between the FIMBRIA of the

hippocampus & the parahippocampal gyrus

a. Molecular Layer

b. Granular Layer

c. Polymorphic Layer

The Dentate Gyrus has three layers:

Parahippocampal Gyrus

Lies between the Hippocampal Fissure and Collateral Sulcus

Alveus, Mammillothalamic Tract,

Connecting Pathways of The Limbic System

Alveus

Consists of a thin layer of white matter that lies on the superior or ventricular

surface of the hippocampus

Alveus

Composed of nerve fibers that originate in the hippocampal cortex

Alveus

The fibers unite on the medial border of the hippocampus to form a bundle called

the Fimbriae

Mammillothalamic Tract

Provides important connections between the mammillary body and the anterior

nuclear group of the thalamus

Striata Terminalis

Arises from the posterior aspect of Amygdaloid Nucleus

Striata Terminalis

Is a bundle of nerve fibers that runs posteriorly in the roof of the inferior horn of the

lateral ventricle on the medial side of the tail of the caudate nucleus.