part 5: Limbic System, Reticular Formation & Brain Protection

What is the limbic system?

A group of structures in the brain that control emotion, motivation, and memory.

What are the three main parts of the limbic system?

Amygdala, cingulate gyrus, and hippocampus.

What is the function of the amygdala?

It processes anger, danger, fear, and other emotional responses.

What is the function of the cingulate gyrus?

It expresses emotions through gestures, resolves mental conflict, shifts attention, and helps with cooperation and flexibility.

What is the function of the hippocampus?

It is crucial for forming and retrieving memories.

What is the overall function of the limbic system?

It links emotions and memories to behavior, influencing motivation and emotional expression.

How is the limbic system connected to the prefrontal cortex?

It allows emotional responses to be consciously controlled and experienced.

What happens when the limbic system is overactive or underactive?

It can contribute to emotional disorders like anxiety, depression, or aggression.

What is the reticular formation?

A network of neurons extending through the brainstem that connects with the hypothalamus, thalamus, cerebrum, and spinal cord.

What is the main function of the reticular formation?

It regulates arousal and consciousness by sending repeated activating signals to the brain.

What happens if the reticular activating system (RAS) is damaged?

It can lead to coma or loss of consciousness.

What does the RAS filter?

Incoming sensory information, preventing sensory overload by ignoring repetitive or weak stimuli.

What is an electroencephalogram (EEG)?

A recording of the electrical activity of the brain.

What are brain waves?

Patterns of electrical activity in the brain measured in Hertz (Hz).

Why are EEGs useful?

They can diagnose brain disorders such as epilepsy, lesions, tumors, or sleep disorders.

What does a flat EEG indicate?

No electrical brain activity — clinical evidence of death.

How do brain waves change?

They vary with age, sensory input, brain disease, and chemical state of the body.

What protects the brain from physical and chemical injury?

Bone (skull), meninges, cerebrospinal fluid (CSF), and the blood-brain barrier.

What are meninges?

Three connective tissue membranes that cover and protect the brain and spinal cord.

What are the three meninges (from outermost to innermost)?

Dura mater, arachnoid mater, and pia mater.

What is the function of the meninges?

They protect the CNS, enclose venous sinuses, and contain cerebrospinal fluid.

What is the dura mater?

A tough, double-layered outer membrane that forms the strongest meninx.

What is the arachnoid mater?

The middle meninx that forms a loose covering around the brain.

What is found beneath the arachnoid mater?

The subarachnoid space, which contains cerebrospinal fluid (CSF) and large blood vessels.

What are arachnoid villi?

Projections that allow CSF to be absorbed into venous blood in the dural sinuses.

What is the pia mater?

The innermost, delicate membrane that clings tightly to the brain surface.

What is cerebrospinal fluid (CSF)?

A clear, watery fluid that cushions the CNS and maintains chemical stability.

How is CSF similar to blood plasma?

It has a similar composition but contains less protein and different ion concentrations.

What are the main functions of CSF?

To protect the brain from trauma, provide buoyancy, prevent the brain from crushing under its own weight, and deliver nutrients.

What produces CSF?

The choroid plexuses located in the ventricles of the brain.

What are choroid plexuses?

Clusters of capillaries that filter blood plasma to form CSF.

How do choroid plexuses regulate CSF composition?

They use ion pumps to adjust CSF composition and remove wastes.

What is the blood-brain barrier (BBB)?

A protective mechanism that maintains a stable environment for brain tissue by restricting passage of substances from the blood.

What forms the blood-brain barrier?

Tight junctions in capillary endothelial cells, a thick basal lamina, and astrocyte end-feet.

What substances can freely pass through the BBB?

Nutrients like glucose and amino acids, and fat-soluble substances such as alcohol, nicotine, and anesthetics.

Where is the BBB absent in the brain?

At areas like the vomiting center and hypothalamus, allowing monitoring of blood composition.

How can stress affect the BBB?

Stress increases permeability, allowing more chemicals to pass through.

What is the overall importance of the BBB?

It prevents harmful substances and pathogens from entering brain tissue.