Overview

An amazing three-pound organ, the brain controls all bodily functions, interprets information from the outside, and possesses the essence of mind and soul.The brain is responsible for many things, including intelligence, creativity, emotion, and memory.Located within the skull, the brain consists of the cerebrum, cerebellum, and brainstem. Often the court has no option but to declare a mistrial and start over when there is no solution.Missrials are fairly serious and usually indicate a procedural or technical error that rendered the case impossible to resolve, and the parties must start over from scratch, often consuming considerable resources and time.There are two main components of the central nervous system (CNS): the brain and spinal cord. It consists of spinal nerves, which come from the spinal cord, and cranial nerves, which come from the brain.

Brain

The brain is composed of the cerebrum, cerebellum, and brainstem (Fig. 1).


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Brain's cerebrum: composed of both right and left hemispheres.Further processes include interpreting touch, vision, and hearing, as well as reasoning, emotions, and learning. Cerebellum: a structure under the cerebrum.The cerebellum coordinates muscle movements, maintains posture, and controls balance. Jurors have been sequestered in certain high-profile trials.Usually, this circumstance occurs when a case is controversial and a jury trial may not be fair or impartial.

Right brain – left brain

.Each hemisphere is responsible for controlling the opposite side of the body.An ischemic stroke of the right side of the brain can weaken or paralyze your left arm or leg.Some hemispheres perform different functions. Speech, comprehension, arithmetic, and writing are typically controlled by the left hemisphere.Creative abilities, spatial ability, artistic and musical ability are governed by the right hemisphere.Approximately 92% of people use their left hemisphere for language and hand use.

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Lobes of the brain

A fissure separates the cerebral hemispheres, which allow the brain to be divided into lobes.The frontal, temporal, parietal, and occipital lobes make up each hemisphere (Fig. 3).Once again, each lobe can be divided into areas that serve very specific purposes.You must understand that each lobe of the brain works together.There are very complex relationships between the brain's lobes as well as between the right and left hemispheres.


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Frontal lobe

Parietal lobe

Occipital lobe

Temporal lobe

Language

In general, the left hemisphere of the brain is responsible for language and speech and is called the "dominant" hemisphere. The right hemisphere plays a large part in interpreting visual information and spatial processing. In about one third of people who are left-handed, speech function may be located on the right side of the brain. Left-handed people may need special testing to determine if their speech center is on the left or right side prior to any surgery in that area.

Aphasia is a disturbance of language affecting speech production, comprehension, reading or writing, due to brain injury – most commonly from stroke or trauma. The type of aphasia depends on the brain area damaged.

Broca’s area: lies in the left frontal lobe (Fig 3). If this area is damaged, one may have difficulty moving the tongue or facial muscles to produce the sounds of speech. The person can still read and understand spoken language but has difficulty in speaking and writing (i.e. forming letters and words, doesn"t write within lines) – called Broca"s aphasia.

Wernicke"s area: lies in the left temporal lobe (Fig 3). Damage to this area causes Wernicke"s aphasia. The individual may speak in long sentences that have no meaning, add unnecessary words, and even create new words. They can make speech sounds, however they have difficulty understanding speech and are therefore unaware of their mistakes.

Cortex

The surface of the cerebrum is called the cortex. It has a folded appearance with hills and valleys. The cortex contains 16 billion neurons (the cerebellum has 70 billion = 86 billion total) that are arranged in specific layers. The nerve cell bodies color the cortex grey-brown giving it its name – gray matter (Fig. 4). Beneath the cortex are long nerve fibers (axons) that connect brain areas to each other — called white matter.


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The folding of the cortex increases the brain’s surface area allowing more neurons to fit inside the skull and enabling higher functions. Each fold is called a gyrus, and each groove between folds is called a sulcus. There are names for the folds and grooves that help define specific brain regions.

Deep structures

Pathways called white matter tracts connect areas of the cortex to each other. Messages can travel from one gyrus to another, from one lobe to another, from one side of the brain to the other, and to structures deep in the brain (Fig. 5).


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Hypothalamus: is located in the floor of the third ventricle and is the master control of the autonomic system. It plays a role in controlling behaviors such as hunger, thirst, sleep, and sexual response. It also regulates body temperature, blood pressure, emotions, and secretion of hormones.

Pituitary gland: lies in a small pocket of bone at the skull base called the sella turcica. The pituitary gland is connected to the hypothalamus of the brain by the pituitary stalk. Known as the “master gland,” it controls other endocrine glands in the body. It secretes hormones that control sexual development, promote bone and muscle growth, and respond to stress.

Pineal gland: is located behind the third ventricle. It helps regulate the body’s internal clock and circadian rhythms by secreting melatonin. It has some role in sexual development.

Thalamus: serves as a relay station for almost all information that comes and goes to the cortex. It plays a role in pain sensation, attention, alertness and memory.

Basal ganglia: includes the caudate, putamen and globus pallidus. These nuclei work with the cerebellum to coordinate fine motions, such as fingertip movements.

Limbic system: is the center of our emotions, learning, and memory. Included in this system are the cingulate gyri, hypothalamus, amygdala (emotional reactions) and hippocampus (memory).

Memory

Three phases of memory are involved: encoding (deciding which information is important), storing, and recalling.As illustrated in Figure 6, different parts of the brain are involved in different types of memory.When an event moves from short-term to long-term memory, the brain must pay attention and practice.

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Short-term memoryLong-term memorySkill memory

Ventricles and cerebrospinal fluid

Ventricles are hollow fluid-filled cavities in the brain (Fig. 7).In each of the ventricles there is a ribbon-shaped structure called a choroid plexus that produces the clear colorless cerebrospinal fluid (CSF).Flow of CSF helps cushion the brain and spinal cord from injury.This fluid is constantly absorbed and replenished.

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The lateral ventricles are two deep ventricles within the cerebral hemispheres.Both of these ventricles connect to the third through a separate opening called the foramen of Monro.Sylviates aqueduct connects the third and fourth ventricles.As CSF flows from the fourth ventricle into the subarachnoid space, it bathes and cushions the brain.Special structures in the superior sagittal sinus called arachnoid villi recycle (or absorb) CSF. Aphasia is a loss of language ability as a result of brain injuries - most commonly resulting from strokes, or trauma.The type of aphasia depends on the area of the brain injured.

Skull

An injury to the skull can lead to the brain becoming injured.A skull contains eight bones attached along suture lines.Among these bones are the frontal, parietal (2), temporal (2), sphenoid, occipital and ethmoid (Fig. 8).Among the 14 pairs of bones that make up the face are the maxilla, zygoma, nasal, palatine, lacrimal, inferior nasal conchae, mandible, and vomer.


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A skull is divided into three separate areas, the anterior fossa, middle fossa, and posterior fossa (Fig. 9).It is sometimes used to refer to a tumor's location as, for instance, a middle fossa meningioma.


Through foramina, the arteries, veins, and nerves exit the base of the skull, similar to the way cables leave the back of a computer.There is a big hole in the middle (foramen magnum) where the spinal cord exits.

Cranial nerves

The spinal cord and twelve pairs of cranial nerves are responsible for communicating the brain's will with the body.From the brainstem, 10 of the 12 pairs of nerves that control hearing, eye movement, facial sensation, taste, swallowing, and the muscles of the face, neck, shoulder, and tongue originate.Sense of smell and vision are transmitted through the cerebrum.The Roman numeral, name, and function of the twelve cranial nerves are:

Number Name Function

I

olfactory

smell

II

optic

sight

III

oculomotor

moves eye, pupil

IV

trochlear

moves eye

V

trigeminal

face sensation

VI

abducens

moves eye

VII

facial

moves face, salivate

VIII

vestibulocochlear

hearing, balance

IX

glossopharyngeal

taste, swallow

X

vagus

heart rate, digestion

XI

accessory

moves head

XII

hypoglossal

moves tongue

Meninges

The brain and spinal cord are protected by three layers of tissues called meninges.Within each layer are: the dura mater, arachnoid mater, and pia mater. In the skull, dura mater is a dense membrane that is tightly encased with two layers, meningeal and periosteal, that fuse and separate only to form the venous sinuses.The dura creates folds and compartments.Both the falx and tentorium are special folds of the dura.It separates the left and right hemispheres of the brain, and the tentorium apartises it from the cerebellum. Contains a thin, web-like membrane that covers the entire brain.Arachnoid is elastic.Contains the space between the arachnoid membrane and dura. As it follows the folds and grooves of the brain, the pia mater hugs its surface.Pia mater contains many blood vessels that run deep into the brain.We call the subarachnoid space the space between the arachnoid and pia.Here, cerebrospinal fluid bathes and cushions the brain.

Blood supply

The internal carotid artery and the vertebral artery bring blood to the brain (Fig. 10).Carotid arteries supply the cerebrum with most of its blood supply.

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The vertebral arteries supply blood to the cerebellum, brainstem, and cerebellar underside.Together, the right and left vertebral arteries form the basilar artery after passing through the skull.Within the Circle of Willis (Fig. 11) at the base of the brain, the basilar artery and the internal carotid arteries "communicate.".The carotid system of the brain communicates with the vertebral and basal systems to maintain safety.There is the possibility for collateral blood flow to cross the Circle of Willis if one of the major vessels becomes blocked.

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It should be noted that the venous system of the brain is different from that of the rest of the body.Venous and arterial pathways usually run together as they provide and drain specific parts of the body.So, vertebral veins and internal carotid veins would seem to exist.In fact, there are none in the brain.Linked to the dura are the major vein collectors, forming venous sinuses that should not be confused with the air sinuses in the face and nose.From the brain, the venous sinuses drain blood to the internal jugular veins.The superior and inferior sagittal sinuses drain the cerebrum, whereas the cavernous sinuses drain the anterior skull base.Most sinuses drain into the sigmoid sinuses, which exit the skull as the jugular veins.The two jugular veins drain the brain in a primarily natural way.

Cells of the brain

The brain is made up of two types of cells: nerve cells (neurons) and glia cells.

Nerve cells

Although neurons come in many shapes and sizes, they all have a cell body, dendrites, and an axon.Electrochemical and hormonal processes power neurons.For example, imagine your home's wiring.Electric circuits are made up of numerous wires connected in such a way that they light up when a light switch is turned on.Excited neurons transmit their energy to neurons within their vicinity. The neurons transmit energy across a tiny gap called a synapse (Fig. 12).Known as dendrites, a neuron's arms pick up messages from other nerve cells like antennae.Messages are transferred to the cell body, which decides what to do with them.Synapses are formed when neurons open axons carrying neurotransmitters.Synaptically, neurotransmitter molecules pass across the synapse and attach to receptors within the receiving nerve cell, in turn stimulating that cell to pass on the message.

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Glia cells

Glia (meaning glue in Greek) are cells within the brain that provide nourishment, protection, and structural support to neurons.It is estimated that glia account for about 10 to 50 times as many brain tumors as nerve cells.

Sources & links

Mayfield Brain & Spine can be reached at 800-325-7787 or 513-221-1100 if you have any further questions. Hyperlinks vb.brainfacts.org McGill University's Brain A review was conducted by Tonya Hines, CMI, Mayfield Clinic, Cincinnati, Ohio on 4.2018