Anatomical review of the brain and Clinical application in Psychiatry

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Introduction:
Human thoughts, feelings, and actions begin in the central nervous system. The brain acts as the primary mediator- organ, controlling and determining how people interact with the world. All human responses are the result of the complex interaction between underlying neuroanatomy and neurophysiology, as well as genetic, environmental and development factors.

The nervous system is your body's decision and communication center. The central nervous system (CNS) is made of the brain and the spinal cord and the peripheral nervous system (PNS) is made of nerves. Together they control every part of your daily life, from breathing and blinking to helping you memorize facts for a test. Nerves reach from your brain to your face, ears, eyes, nose, and spinal cord... and from the spinal cord to the rest of your body. Sensory nerves gather information from the environment; send that information to the spinal cord, which then speed the message to the brain. The brain then makes sense of that message and fires offa response. Motor neurons deliver the instructions from the brain to the rest of your body. The spinal cord, made of a bundle of nerves running up and down the spine, is similar to a superhighway, speeding messages to and from the brain at every second.
Brain

·         Brain is the most important structure in the human body. Weighs 3 to 5 pounds, the brain contains approximately 140 billion cells, making it the most complicated and vital organ in the body. Brain cells are categorized as either neurons or neuroglia. Neurons generate and conduct electrical signals.
·         Neuroglia provides the mechanical and physiological support to the neurons.
·         White matter is composed of the axons of neurons that are insulated by myelin. White matter makes up the core of major brain structures.
·         The gray matter or cortex typically covers the surface of these organs.
·         The cortex is functional area of the brain where neurons communicate with each other and where neurotransmitters are concentrated.
Parts of the brain
·         The brain is made of three main parts: the forebrain, midbrain, and hindbrain.
·         The forebrain consists of the cerebrum and diencephalon(thalamus, hypothalamus and limbic system).
·         The midbrain consists of the mesencephalon (tectum and tegmentum).
·         The hindbrain is made of the cerebellum, pons and medulla. Often the midbrain, pons, and medulla are referred to together as the brainstem.
The Cerebrum: The cerebrum or cortex is the largest part of the human brain, associated with higher brain ftlnction such as thought and action. The cerebral cortex is divided into four sections, called "lobes": the frontal lobe, parietal lobe, occipital lobe, and temporal lobe.
Functions of these lobes-
·         Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving
·         Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli  
·         Occipital Lobe- associated with visual processing
·         Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech
Normal functions and symptoms of dysfunction of the cerebrum:
Lobe
Location
Normal function
Symptoms of alteration
Frontal
Anterior or front area of the brain
Programming and execution of motor functions, higher thought process, intellectual insight, judgment, expression of emotion, decision making.
Changes in affect, alteration in language production, motor functioning, decision making, impulsive behavior
Parietal
Posterior to central sulcus
Sensory perception,following directions on a map, reading a clock, or dressing oneself.
Decreased consciousness of pain sensation, difficulty with time concepts, alteration in personal hygiene, inability to calculate numbers or perform motor actions, poor attention span.
Temporal
Lies beneath skull on both sides
Primarily responsible for hearing and receiving information via ears
Auditory hallucinations, increased sexual focus, decreased motivation, alterations in memory and emotional responses, sensory aphasia
Occipital
Most posterior of brain
Seeing and receiving information via eyes
Visual hallucinations
                       
The cerebral cortex is highly wrinkled. Essentially this makes the brain more efficient, because it can increase the surface area of the brain and the amount of neurons within it.
 A deep furrow divides the cerebrum into two halves, known as the left and right hemispheres. The two hemispheres look mostly symmetrical yet it has been shown that each side functions slightly different than the other. Sometimes the right hemisphere is associated with creativity and the left hemisphere is associated with logic abilities. The corpus callosum is a bundle of axons which connects these two hemispheres.
Nerve cells make up the gray surface of the cerebrum which is a little thicker than your thumb. White nerve fibers underneath carry signals between the nerve cells and other parts of the brain and body.
Diencephalon: Constitutes only 2% of the CNS by weight.Has extremely wide spread and important connections; the great majority of sensory, motor and limbic pathways involve the diencephalon. It includes: thalamus, hypothalamus and the limbic system. 
Mesencephalon: Structures of major importance of mesencephalon or midbrain include nuclei, and fiber tracts. It extend from the pons to the hypothalamus and is responsible for integration of various reflexes, including visual, auditory and righting reflexes.
Pons: Is a bulbous structure that lies between the mid brain and the medulla. Composed of large bundles of fibers and forms a major connection between the cerebellum and the brain stem. Also contains the central connections of cranial nerve V through VIII and center for respiration and skeletal muscle tone.
Medulla: Is the connecting structure between the spinal cord and the pons, and all of the ascending and descending fiber tracts pass through it. The vital centers are contained within the medulla , and is responsible for regulation of heart rate, blood pressure and respiration. Reflex centers for swallowing, sneezing, coughing and vomiting.
Basal nuclei:
Also known as basal ganglia are concentrations of cell bodies closely involved in motor functions and association. They are concentrations of grey matter located within the white matter of the cerebrum and midbrain. Among the most well known basal nuclei are caudate lobe, putamen, globus pallidus, and substantia nigra. Functions of these basal nuclei are:
·         Translate rnovements such as walking while it is happening, and they also modulate and correct muscle functioning that allows movement to occur in a coordinated manner.
·         Aid in the learning and programming of the complex motor behavior which in the course of time becomes automatic.
Conditions such as Huntington's disease and Parkinson's disease are associated with basal nuclear dysfunction and their inability to effectively communicate with the cerebral cortex. Even some medications given to treat psychiatry disorders alter the basal nuclei, example: chlorpromazine and haloperidol are two older neuroleptic antipsychotic medications that cause hypertonicity or dystonia.
Some of the network of nuclei and their functions:
l . Cerebral cortex: involved in critical decision making and higher order thinking such as abstract reasoning.
2. Limbic system: involved in regulating emotional behavior, memory and learning.
3. Basal ganglia: co-ordinates involuntary movements and muscle tone.
4. Hypothalamus: regulates pituitary homones.
5. Locus ceruleus: makes norepinephrine, a neurotransmitter involved in response to stress. It's located in the pons region of the brain.
6. Raphe nuclei: makes serotonin, involved in regulation of sleep and behavior mood.
The Cerebellum
The cerebellum, or "little brain", is similar to the cerebrum in that it has two hemispheres and has a highly folded surface or cortex. This structure is associated with regulation and coordination of movement, posture, and balance. It is situated at the base of the skull, above the brainstem and beneath the occipital lobe of the cerebral cortex.
Functions:
·         Fine Movement Coordination
·         Balance and Equilibrium  
·         Muscle Tone
Limbic system:
Instincts, primitive drives, sexual arousal, fear, aggression and other emotions are part of the functions of the structures deep within the brain called the limbic system or limbic lobe. The structures of this system are:
-- Hippocampus
-- Thalamus
-- Hypothalamus
-- Amygdala
 -- Limbic Midbrain Nuclei
Hippocampus
·         Involved in storing information, especially the emotions attached to memory.
·         Deterioration of these nerves lead to hallmark symptoms of memory dysfunction.
·         Damage to the left hippocampus impairs verbal memory and damage to the right one causes difficulty with recognition and recall of complex visual and auditory patterns.
·         Modulates emotional states,
·         Regulates affective responses to events
·         Difficulties in memory of Alzheimer disorder.
Thalamus
·         Relay switching center of the brain
·         Thus it prevents the cortex from becoming overload with sensory stimulus.
·         Damage to a very small area will cause defect in many cortical functions, thus causing behavioral problems.
·         Influences prefrontal cortical functions such as affect and foresight.
·         influences mood and general body movements associated with strong emotions, such as fear or rage.
Hypothalamus
·         Basic human activities such as sleep-rest patterns, body temperature, thirst, and physical drives(hunger and sex) are regulated by this area.
·         Situated deep within the brain.
·         Dysfunction of this structure causes sleep and appetite problems.
·         Also helps in the production of ADH, and Oxytocin.
·         Research indicates that some symptomatic behaviours, such as appetite and sleep problems in the depressed clients, the seasonal mood changes of SAD (Seasonal Affective disorder), and temperature regulation problems in clients with schizophrenia.
Amygdala
·         This is directly connected to more primitive centers of the brain.   Lies adjacent to the hippocampus
·         This provides an emotional component to memory and is involved in modulating sexuality and aggression.
·         Impulsive acts of aggression and violence have been linked to deregulation.
·         Modulates emotional states, regulates affective responses to events.
·         Rapid misfiring of neurons in this regions causes typical symptoms of BPAD and panic disorder.

Limbic midbrain nuclei
·         This is a collection of neurons that appear to play a role in the biologic basis of addiction.
·         Sometimes referred to as the pleasure or reward center of the brain.
·         The main function is to reinforce chemically certain behavior, ensuring their repetition.
Structure
Function
Dysfunction
Amygdala
Modulates emotional states. Regulates affective responses to events
Rapid misfiring of neurons in this region causes typical symptoms of BPAD. panic disorder.
Thalamus
Relays all sensory information, except smell. Filters incoming information regarding emotions and memory to prevent cortex overloading.

Hypothalamus
Regulates basic human functions such as sleep-rest patterns, body temperature, and physical drives of hunger and sex.
Symptomatic behavior in depressed clients, seasonal mood changes in SAD and temperature regulation problem in schizophrenic.
Hippocampus
Modulates emotional states, Regulates affective responses to events
Difficulties in memory of Alzheimer disorder.
Brain stem
Brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord.
The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves. This is an extremely important part of the brain as the nerve connections of the motor and sensory systems from the main part of the brain to the rest of the body pass through the brain stem.
This includes the corticospinal tract (motor), the posterior column-medial lemniscus pathway (fine touch, vibration sensation and proprioception) and the spinothalamic tract (pain, temperature, itch and crude touch). Brain stem regulates the central nervous system, and is pivotal in maintaining consciousness and regulating the sleep cycle. The brain stem has many basic functions including heart rate, breathing, sleeping and eating.
Clinical application
1.Schizophrenia
Researchers have noted that an increase in ventricular size is apparent in many people with schizophrenia. In schizophrenia increased ventricle size is most likely related to neurodevelopmental factors; that is, the brain around the ventricles has failed to develop, and the ventricles have enlarged to fill the empty face.
Other biologic differences found in people with schizophrenia include a decrease in cerebral blood flow, particularly in the prefrontal areas of the cortex. Imaging technologies that tracks blood flow and glucose metabolism has substantiated this physiologic change. These brain changes result in a decline in frontal cognitive functions, such as organizing, planning, learning, problem solving and critical thinking. Another biological theory (dopamine hypothesis), it is caused by alterations of dopamine levels in the brain.
2.Depression
Decreased amounts of norepinephrine and serotonin, two important brain neurotransmitters, are thought to play a role in depression. Some researchers have found evidence for the involvement of acetylcholine, dopamine, and GABA. The receptor, thyroid, hypothalamic, and pituitary has a role in depression.
3.Anxiety
Research has indicated that drugs that activate GABA receptors, causing an inhibitory effect, can calm anxious patients. Other neurotransmitters, such as norepinephrine, epinephrine, dopamine, and serotonin might also have roles in anxiety.
4.Dementias
Alzheimer's disease is caused by brain atrophy, which has been demonstrated microscopically as neurofibrillary tangles and amyloid plaques. Patients with AD tend to have enlarged ventricles, narrowing of the cortical ribbon (gray matter), widening of the sulci, and decrease in the width of the gyri. Furthermore, a loss of cholinergic pathways is found in patients with AD, contributing to memory problems.
5.Degenerative diseases
Parkinson's disease is an example of a degenerative disease that affects both motor function and emotional stability. In Parkinson's, microscopic examination of the basal ganglia, specifically the caudate nucleus and globus pallidus, reveals degenerative changes. The decreased availability of dopamine which is synthesized by the substantia nigra leads to EPS.
6.Demyelinating diseases
In Multiple sclerosis both the myelin and eventually the axons break down. The degeneration of myelin causes various problems, including loss of sensation, muscle weakness, fatigue, double vision, and tingling in the extremities. People with Multiple sclerosis also experience psychological symptoms.
7.Anorexia Nervosa
It appears to be associated with hypothalamic dysfunction.
References:
l . Stuart G W, Laraia M T; Principles and practice of Psychiatry Nursing; 7th edition; Harcourt Pvt Ltd:India.
2.Chaurasia B D; Anatomy Regional and Applied; 3rd edition; volume 3; CBS Publishers: New Delhi, India.
3.Fortinash K M, Worret P A H; Psychiatry Mental Health Nursing; 4th edition; Mosby Elsevier: USA.
4.Keltner NL, Schwecke LH, Bostrom CE. Psychiatric Nursing. 5th ed. Mosby Elsevier: USA.




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