Cerebral Gray Matter

Basal Nuclei Anatomy

The gray matterThe inner portion of the spinal cord composed mostly of neuron cell bodies and synapses. of the brain is unmyelinated cell bodies.  We call clusters of cell bodies nucleiClusters of neurons in the CNS responsible for processing information. in the brain and ganglia outside of the CNSComposed of the brain and spinal cord; integrates and processes information. . In olden days, these were also referred to as ganglia.  Confusing.  We will consistently refer to these gray matter masses as nuclei in the brain. They include cell bodies, axon terminals, and synapseThe junction between two neurons where communication occurs. areas. 

Always begin with anatomyThe study of the structure of the human body..  Always begin with something you are familiar with on the diagram.  This is a coronal or a front section A cut or slice of the body or an organ for study., cutting the brain into an anteriorThe front of the body or toward the front when standing in the anatomical position. and a posterior section.  These open areas here are the ventricles.  The basal nucleiClusters of neurons in the brain that help regulate movement and coordination. have been revised in classification as we advance neurobiology.  As our tools become more precise, we realize that there are more discrete areas of the basal nuclei.  These are the only three terms to be concerned with right now.  Terms such as lentiform nucleusA component of the basal nuclei involved in movement regulation. are too outdated for us and corpus striatumA part of the basal nuclei involved in movement and reward processing. is too much for us.  On this diagram, locate the green and the purple.  These are the three structures that together will be the basal nuclei for now.

Basal Nuclei Functions

The basal nuclei are synapse areas between Axon terminals and cell bodies. The neurotransmitterChemicals that transmit signals across synapses. that is secreted at these synapses is dopamineA catecholamine neurotransmitter involved in motor control, motivation, and reward.. It can be either excitatory or inhibitory depending on which structure in the basal nuclei we are talking about. These areas of synapse will not work if the substantial nigra of the midbrainThe upper portion of the brainstem involved in visual and auditory processing. stops making melaninA brown-black pigment made by melanocytes in the stratum basal and given to keratinocytes as melanos. 

Your basal nuclei is full of interneuronsNeurons that process information and connect sensory and motor neurons, found only in the CNS.. These interneurons consolidate sensory information from ascending tractsBundles of axons that carry sensory information from the spinal cord to the brain. and the cerebellumThe brain region responsible for balance, coordination, and fine motor control.. They determine a motor response. The response will be distributed to the thalamusThe brain’s relay center, sending sensory information to the cerebral cortex.. The basal nuclei rely primarily on proprioceptor information to assess posture and position. These proprioceptorsSensory receptors that monitor the position and movement of the body. are carefully placed at joints like your elbows, hips, and knees. The basal nuclei receive information from the optic nerve. They also get data from other cranial nervesNerves that arise from the brain and control head and neck functions. carrying sensory information regarding balance and movements. When the basal nuclei receives information from the cerebellum it is primarily concerned with preventing unnecessary movements.

For example an unnecessary movementA fundamental property of life involving motion of the body or its parts. could be a tremor.  Because this info is funneled through the thalamus, a Parkinson’s tremor can be voluntarily stopped.  The patient is able to prevent it, but only consciously, not unconsciously.  The basal nuclei are not getting the dopamine they need from the substantia nigraA midbrain structure involved in movement and dopamine production..

The basal nuclei don’t only take information from the cerebellum or your ascending tractsBundles of nerve fibers in the CNS that carry signals between brain regions.. It also retrieves learned movement patterns from your memoryThe ability to store and recall information.. Examples include a sequence of dance steps. They also include the steps needed to tie your shoes or any patterns involved in playing an instrument. The basal nuclei access all these patterned movements. Then it distributes its instructions to the thalamus.

Reticular Formation

In your cerebrumThe largest part of the brain, responsible for thought, memory, and voluntary movements. there is this outward radiating web of unmyelinated neuronsThe functional cells of the nervous system that transmit signals.. This previously has been called the corona radiataThe layer of follicular cells that surrounds a developing oocyte.. The term corona means headRounded proximal end that fits into the acetabulum of the hip bone. and radiata means radiating outward. These arrows on this diagram indicate those neurons. Over the last 20 years, we’ve learned more about their function. We have replaced their name with the reticular formationA network of neurons in the brainstem that regulate alertness and consciousness.. This can also be called the reticular activating system.

Reticular Formation

All of these neurons work together with some of your special senses. They process sensory information and motor output pathways. This collaboration gives you a baseline level of consciousness. Differences in the reticular activating system account for how people study differently. For example I need to be in a sensory deprivation PET tank in order to study. I have a best friend who could study in the cafeteria. Neither of us is good or bad. It depends on how our reticular activating system can ignore certain stimuliChanges in the environment that are detected by sensory receptors. or be distracted by it. Pain modulation, or your conscious interpretation of it, is funneled through this reticular activating system.  Have you ever live in some serious chronic pain?  I have/do.  Each time you experience pain, you level up.  This is how it works: you experience pain. You convince your brain the pain is normal. You experience pain again at an increased level. You convince your brain this new level is normal. You experience pain again at an even more increased level. You convince your brain the pain is normal. This cycle increases your tolerance for pain. It allows you to ignore your body yelling at you that there is something wrong. Personally this validates my insomnia that I claim to be a product of my pain levels.

The reticular formation of the cerebrum is what we’re talking about here. Right just the Gray matter that’s innervating the big brain hat. Many fibers of this Gray matter connect to areas in the ponds. They also connect to the medulla oblongataThe lowest part of the brainstem controlling vital functions like breathing and heart rate. of the brain stem. The reticular formation collaborates with these areas. It controlsVariables that remain constant to ensure a fair test. motor output to your neuromuscular junctions. It also controls cardiovascular organs like the heart and blood vessels.