What is Grey Matter Definition Structure and Function
Our brain is deemed as one of the most complex and intriguing structures. But anatomically it can be divided into a few discrete parts which are: the right and left hemispheres, frontal lobes, occipital, temporal, and parietal lobe. Another common divider for the brain is grey matter and white matter.
Grey and white matter tissues are present in our central nervous system. Grey matter forms the outermost layer of our brain and has a pinkish-grey tone (that’s where the name comes from). The grey matter has an essential role in enabling human beings to function normally on a daily basis. Grey matter and white matters are both vital sections of the brain and spinal cord.
We will learn a great deal about the grey matter in the brain in this article. We will be covering functions of grey matter, the difference between grey and white matter, and also learning how to increase grey matter through certain activities.
(Image will be Uploaded Soon)
Grey Matter Contents
The material between our ears is present in two shades; white and grey. The difference between these two matters is in the amount of fat content. The grey matter contains:
High concentration of neuronal cell bodies (which is responsible for its grey tone).
Unmyelinated Axons - Axons are elongated portions of the neuron which is placed at the center of the cell in between axon and soma. These axons are unmyelinated which means they do not have a covering of fatty protein which is whitish in color.
Non-neuron Brain Cells Which are also Called Glial Cells - These cells provide energy and nutrients to the neurons. They also help in transporting glucose to the brain, clean excess chemicals out of the brain, and may also affect the intensity of how neurons communicate.
Grey matter forms from ectoderm (the outermost layer of skin) in early development years and continues to form till we attain 8 years of age. After this point, the grey matter starts decreasing in brain areas but the matter density increases. This higher density allows further mental development and higher processing powers of our brains.
Grey Matter in Brain
Grey matter in the brain is found in abundance in the cerebellum, brain stem, cerebrum, and spinal cord.
The cerebrum has a sheet of grey matter of thickness of 2 to 5 mm.
Grey matter in the brain is highly concentrated in the Cerebellum, which is just 10% of the total brain volume. The cerebellum contains more neural cell bodies than all the other parts of the brain combined.
Grey Matter Composition and Placement
The grey matter has somas which are neuronal cell bodies. These structures are circular in shape and contain the nucleus of the cells. Our cerebellum has 10 to over 50 billion cells.
White matter is a layer of nerve fibers lying below the grey matter surface. White matter connects neurons in the grey matter to other parts of the brain.
Grey matter is present throughout the inside of the spinal cord in a horn-like structure and white matter fills up the surrounding sections of the spinal cord.
Grey matter around the cerebrum is referred to as the cortex of the brain. We have two major cortexes in our brains: cerebellar and cerebral cortexes.
The cortex has a wrinkled appearance due to the presence of ridges (called gyri) and grooves (called sulci).
Gyri and sulci increase the surface area of the brain which allows more neurons to be present (which is not possible on a smooth surface). This is crucial for the effective working of the brain.
Grey matter also contains glial cells which are supportive to the neurons. Glial cells, specifically oligodendrocytes (they produce myelin) and astrocytes are present in numbers that are 10 times more than neurons.
Grey matter also has capillary blood vessels and neuropil which is a mix of glia, dendrites, and unmyelinated axons.
Grey Matter Function
Grey matter performs many functions in our bodies that are basic for living. It enables us to control our movements, regulate emotions, retain memories, and controls many other aspects of human life that depend on grey matter in brain.
Grey matter processes information in the brain. Grey matter receives signals from our sensory organs or other areas within the grey matter. There are structures in grey matter that process these signals. These sensory stimuli are then directed to the neurons present in our central nervous system where synapses produce a response to the stimuli.
Grey matter in the cerebellum affects human personalities and plays a role in:
Motor functioning and automatic movements
Intelligence
Organization
Planning
Processing sensory information
Language processing
The grey matter of the spinal cord has its own functions. The anterior column of grey matter connects to the brain via a pathway known as the pyramidal tract (originating in the cerebral cortex) and is essential for motor movements
The posterior grey matter in the spinal cord helps in receiving sensory signals and enables our body’s constant interaction with the environment.
The lateral grey matter in the spinal cord is present in the middle and regulates the autonomic nervous system by activating the sympathetic nervous system. Our bodies’ response to stressful situations is stimulated by the sympathetic nervous system. For example, when our heartbeat accelerates, the nervous system sends extra blood to muscles.
How to Increase Grey Matter
There are a few ways of boosting your mood and reducing stress which also leads to an increase in the grey matter in the brain.
Meditation - As per a study from Harvard University, long-term meditation has been shown to increase the amount of grey matter in the brain within the sensory and insula region and sensory and auditory cortex. Meditation alters brain wave patterns and helps you sleep better.
Physical Activities - Apart from the health benefits of physical activities, science has proven that working out increases grey matter in the brain. Cardiovascular exercises enhance the central nervous system and increase both grey matter and white matter in our brains.
Playing Video Games - Many people feel that playing video games is bad for your brain. But according to a study done by the Macquarie University of Sydney and the University of Electronic Science and Technology of China, video games change the brain structure. They heighten the connection between a few insular cortex subregions and result in a larger surface area and greater volume of grey matter
FAQs on Grey Matter in Brain and Spinal Cord
1. What is grey matter in the brain?
Grey matter is the part of the central nervous system that contains mainly neuronal cell bodies, dendrites, and unmyelinated axons. It appears gray because it lacks the fatty myelin sheath that makes white matter look white. In the brain, grey matter forms the outer layer called the cerebral cortex and also occurs in deeper regions like the basal ganglia. It is primarily responsible for processing information and controlling functions such as thinking, memory, and voluntary movement.
2. What is the function of grey matter?
The main function of grey matter is to process and integrate information in the nervous system. It performs this role through:
- Housing neuron cell bodies that generate and process nerve impulses
- Enabling synaptic transmission between neurons
- Controlling higher functions like learning, memory, speech, and decision-making
- Regulating voluntary muscle movements via the motor cortex
Because it contains most of the synapses, grey matter is crucial for cognitive and sensory processing.
3. Where is grey matter located in the body?
Grey matter is located in both the brain and the spinal cord. Its distribution includes:
- The outer layer of the brain called the cerebral cortex
- Deep brain structures such as the thalamus and basal nuclei
- The central H-shaped region of the spinal cord
In contrast to the brain, where grey matter is mostly on the outside, in the spinal cord it is located centrally.
4. What is the difference between grey matter and white matter?
The key difference between grey matter and white matter is that grey matter contains neuron cell bodies, while white matter contains myelinated axons. Specifically:
- Grey matter: composed of cell bodies, dendrites, and unmyelinated fibers; involved in processing information
- White matter: composed mainly of myelinated axons; responsible for transmitting signals between different brain regions
Grey matter handles analysis and integration, whereas white matter ensures fast communication within the nervous system.
5. Why is grey matter called grey?
Grey matter is called grey because it lacks large amounts of the fatty substance myelin, which gives white matter its pale color. The presence of numerous neuron cell bodies, capillaries, and unmyelinated fibers gives it a grayish appearance in fresh tissue. This color difference is visible in anatomical sections of the brain and spinal cord.
6. What structures are found in grey matter?
Grey matter contains the main cellular components responsible for neural processing. These include:
- Neuron cell bodies (soma)
- Dendrites
- Unmyelinated portions of axons
- Neuroglial cells such as astrocytes and microglia
- Numerous synapses
These structures enable communication and integration of signals within the central nervous system.
7. How does grey matter help in learning and memory?
Grey matter supports learning and memory by enabling synaptic connections between neurons. It contributes through:
- High density of synapses that allow information processing
- Synaptic plasticity, especially in regions like the hippocampus
- Integration of sensory and cognitive inputs in the cerebral cortex
Changes in synaptic strength within grey matter form the biological basis of memory and skill acquisition.
8. What is grey matter in the spinal cord?
In the spinal cord, grey matter is the central H-shaped region that contains neuron cell bodies involved in reflexes and signal integration. It is organized into:
- Dorsal horns for sensory information
- Ventral horns for motor neuron cell bodies
- Lateral horns (in some segments) for autonomic neurons
This arrangement allows the spinal cord to coordinate reflex actions and relay signals to and from the brain.
9. Does grey matter increase or decrease with age?
Grey matter volume generally decreases with normal aging. This reduction occurs due to:
- Loss or shrinkage of neurons
- Reduction in synaptic density
- Changes in cortical thickness
However, lifestyle factors such as learning and physical activity can help maintain grey matter in certain brain regions.
10. What happens if grey matter is damaged?
Damage to grey matter can impair processing, cognition, sensation, or movement depending on the affected area. Possible effects include:
- Memory loss if the hippocampus is affected
- Movement disorders if the motor cortex or basal ganglia are damaged
- Sensory deficits if the sensory cortex is involved
Conditions such as stroke, multiple sclerosis, and neurodegenerative diseases can lead to grey matter damage.
