Anatomy – Brain
The brain is the body’s most complex organ and forms the center of the body’s nervous system. The brain floats within the thick bones of the cranium (skull) in cerebrospinal fluid (CSF). The network of blood vessels transporting blood to and from the brain are highly specialized and forms what scientists call the blood-brain barrier. Many substances in the blood (including, but not limited to, certain drugs) are not transported to the brain because the specialized blood vessels filter them out.
The adult brain weighs about 1,5 kg and is composed of three main parts:
- The cerebrum (the largest part of the brain)
- The cerebellum
- The brain stem
The brain stem is located at the lowest portion of the brain and serves as a connection between the brain and the spinal cord. The brain stem regulates the body’s involuntary functions, including breathing, heart beat, digestion, and blood pressure.
Toward the rear of the head is a small area of the brain called the cerebellum. The cerebellum regulates balance and coordination
The cerebrum is what most people think of when they think of the brain: it is the largest area of the brain and is located atop the brain stem and cerebellum. The wrinkles in the brain are actually folds of the brain’s tissue. The neural tissue of the brain (tissue made up of neurons or nerve cells) are folded up within the cerebrum in such a way that a great deal of neural tissue is enclosed in the skull. Every fold of this tissue is called a sulcus and the smooth section between folds (the “valleys”) is called a gyrus.
The cerebrum is divided into two equal halves, the right and left hemispheres. Each hemisphere has lobes which are named for the bones in the skull that cover them:
- Frontal lobe
- Parietal lobe
- Occipital lobe
- Temporal lobe
A fifth lobe, the insular lobe, is located deeply around the sylvian fissure behind the temporal lobe.
The cerebrum handles most of what we would consider to be “brain work”, that is, it is involved with problem solving, organization, thought, emotions, and memory. The cerebrum controls voluntary movement. This portion of the brain also interprets sensory input (what we see, hear, touch, smell, and taste).
Neurosurgeons and experts in the study of the brain know that different areas of the brain are associated with different functions. For instance, the portion of the cerebrum that interprets the images that come through our eyes is distinct from the area of the brain that helps us speak. Brain mapping helps neurosurgeons to understand what portions of the brain are involved in which specific functions. While scientists might generally state that a certain area of the brain is involved in hearing, there can be variation by individuals.
The right and left hemispheres of the brain each control the opposite side of the body, that is, the right hemisphere regulates the activity of the left arm and leg and vice versa. While many areas of the two hemispheres are mirror images of the other (for instance, the area that controls the right hand is in the left hemisphere and is the mirror image of the area of the right hemisphere that controls the left hand), some functions are unique to each hemisphere. In most people, the language center of the brain is located in the left hemisphere.
The right and left hemispheres of the brain are connected by a large bundle of nerves called the corpus collosum.
Circulation to the Brain
The brain is fed by an intricate network of blood vessels around the brain. Every heart beat pumps a specific amount of blood to the body; about a quarter of that blood winds up going to the brain. The healthy brain uses about 20% of all of the oxygen taken in through the lungs and delivered by the blood. It has been estimated that a person engaged in deep thought or solving a difficult problem may use 50% of his or her total oxygen intake to fuel the brain.
The adult brain is made up of about 100 billion neurons or nerve cells. These neurons have branch-like projections called axons that touch each other at what has been estimated to be at least 100 trillion different points of contact. This dense network of axons is called the “neuron forest”.
The brain sends and receives messages by way of a tiny electrical charge that travels through the neuron forest. The points at which neurons and axons make contact are called synapses. When the electrical charge from the brain travels through a neuron and reaches a synapse, it may release a tiny burst of chemicals called neurotransmitters. The body makes dozens of different types of neurotransmitters. The goal of the neurotransmitter is to travel across the synapse and relay the signal to other cells. Thus, the messaging system of the brain to the body involves electrical and chemical processes that happen across thousands of points in a fraction of a second.
Other Structures in the Brain
The brain also contains the thalamus, hypothalamus, pituitary gland, amygdalae, and hippocampus.
The thalamus is a grey nucleus responsible for relaying signals associated with sensory input, spatial orientation, and motor activities. The thalamus also helps to regulate consciousness, sleep, and altertness. Sensory input (except for sense of smell) relays those messages first to the thalamus, which forwards them to the appropriate area of the cortex.
Hypothalamus and Pituitary Gland
The hypothalamus is a small structure about the size of an almond located just beneath the thalamus and just above the brain stem. The hypothalamus works closely with the pituitary gland and helps relay signals and process information related to the body’s endocrine system. The hypothalamus regulates certain autonomic (involuntary) functions and helps regulate the body’s metabolism. The hypothalamus controls hunger, thirst, fatigue, and helps regulate our body temperature. It helps to coordinate hormonal activity initiated by the pituitiary gland.
The pituitary gland regulates and secretes nine major hormones which control many important body functions, including growth, pregnancy, sexual activity.
Two almond-shaped structures in the cerebrum known as amygdalae (singular: amygdala) are believed to help process emotional response, facilitate memory storage, and interpret olfactory stimuli (smells). Studies indicate that the amydalae help to store memories associated with emotional events, such as response to news of a tragedy or a fearful experience. Although the amygdalae are not memory storage regions, they help to consolidate, organize, and interpret the types of memories that are retained in long-term memory. Recent neuroimaging studies are bringing evidence that abnormalities of the amygdalae may relate to mental health or mood disorders.
Hippocampus is located in the cerebrum with mirror-image right and left halves, the hippocampus aids in:
- Short-term memory storage
- Organizing and transitioning certain short-term memories into long-term memory
- Spatial orientation, including sense of direction
- The sense of smell
The shape of the hippocampus has been compared to that of a seahorse.
The brain is a complex structure that is not yet fully understood by modern medicine. The Neuro Spinal Hospital believes that individuals facing brain disorders benefit by a better understanding of how the brain works. The brain can be incredibly resilient and it is sometimes possible that the brain can compensate for damaged areas by training new portions of the brain to handle key functions. Brain disease, disorders, tumours, and injuries can often be managed, but require expert medical intervention, in the form of fast, accurate diagnosis and state-of-the-art treatment.