Part 3 – Cerebral White Matter, Basal Nuclei, Diencephalon

What is cerebral white matter composed of?

Deep myelinated fibers and their tracts.

What is the main function of cerebral white matter?

Communication between the cerebral cortex, lower CNS centers, and other areas of the cerebrum.

What are basal nuclei (basal ganglia)?

Masses of gray matter found deep within the cortical white matter.

What structures make up the basal nuclei?

Several groups of cell bodies including the substantia nigra and amygdala.

What is the general function of the basal nuclei?

Motor control — they help regulate voluntary motor activities and coordinate movement.

What neurotransmitter plays a major role in basal nuclei function?

Dopamine.

What happens when the basal nuclei are damaged or dopamine is reduced?

Motor disorders such as Parkinson’s disease can occur.

What is another term used for basal nuclei?

Basal ganglia.

What is the basal ganglia often described as?

The master of the motor system.

How does the basal ganglia coordinate movement?

It connects motor areas from the brainstem, cortex, and cerebellum to produce smooth movement.

What are two types of movement problems associated with basal ganglia damage?

Unwanted, extraneous movements or difficulty initiating intended movements.

What is the diencephalon?

The central core of the forebrain that surrounds the third ventricle.

What are the three paired structures of the diencephalon?

Thalamus, hypothalamus, and epithalamus.

What is the thalamus?

Two egg-shaped masses of gray matter connected by the intermediate mass, acting as a relay center for sensory information.

Why is the thalamus called the "Grand Central Station" of sensory information?

Because sensory impulses from all senses (except smell) pass through it before reaching the cortex.

What types of information are processed in the thalamus?

Sensory, motor, emotion, somatosensory, vision, auditory, and limbic information.

What does the thalamus do with sensory input?

It sorts, edits, and relays impulses as a group to appropriate cortical areas.

What are some key functions of the thalamus?

Mediating sensation, motor activities, cortical arousal, learning, and memory.

Give an example of thalamic function in attention.

Hearing your name in a noisy crowd or filtering important sensory information.

What disorder may involve abnormal thalamic filtering?

Autism.

What is the hypothalamus?

A small but vital region located below the thalamus, forming the lower walls of the third ventricle.

What are mammillary bodies?

Paired nuclei on the anterior hypothalamus that act as relay stations for olfactory pathways.

What is the infundibulum?

A stalk that connects the hypothalamus to the pituitary gland.

What is the hypothalamus often referred to as?

The main visceral control center of the body.

List several functions of the hypothalamus.

It regulates blood pressure, heart rate, digestion, breathing, temperature, hunger, thirst, sleep, and emotions such as fear and rage.

How does the hypothalamus help regulate body temperature?

It initiates cooling or heat-conserving mechanisms to maintain homeostasis.

How does the hypothalamus regulate hunger and satiety?

It monitors blood nutrient levels and triggers feeding or fullness responses.

What role does the hypothalamus play in sleep?

It regulates sleep and the sleep cycle through interaction with other brain centers.

What are the endocrine functions of the hypothalamus?

It controls secretion of hormones by the anterior pituitary and produces ADH and oxytocin released by the posterior pituitary.

What is the epithalamus?

The most dorsal portion of the diencephalon, located above the thalamus.

What gland is found in the epithalamus?

The pineal gland.

What does the pineal gland secrete?

Melatonin.

What is the function of melatonin?

It regulates sleep, wake cycles, and mood.

What is the choroid plexus and where is it found?

A network of capillaries in the epithalamus that produces cerebrospinal fluid (CSF).

How does the choroid plexus help the brain?

It filters blood, forms CSF, and removes waste products.