All serotonin receptors, except for 5-HT3, are coupled with G proteins instead of being ligand gated ion channels.

Serotonin (5-hydroxytryptamine, 5-HT) receptors are primarily G protein receptors, except for 5-HT3, which is a ligand-gated receptor. It is important to remember that 5-HT3 is most commonly associated with nausea. Additionally, 5-HT7 is linked to circadian rhythms. The stimulation of 5-HT2 receptors is believed to be responsible for the side effects of insomnia, agitation, and sexual dysfunction that are associated with the use of selective serotonin reuptake inhibitors (SSRIs).

Deep brain stimulation (DBS) for treatment resistant depression targets specific brain regions based on their known involvement in pleasure, reward, and mood regulation. The nucleus accumbens is targeted due to its role in pleasure and reward processing. The inferior thalamic peduncle is targeted based on PET studies showing hyperactivity in depression. The lateral habenula is chosen due to observed hypermetabolism in depressed patients. The subgenual cingulate gyrus is targeted due to its hyperactivity in depression. The ventral capsule/ventral striatum is chosen based on its association with improved mood and reduced depressive symptoms following ablation treatments for OCD and depression.

Apraxia: Understanding the Inability to Carry Out Learned Voluntary Movements

Apraxia is a neurological condition that affects a person’s ability to carry out learned voluntary movements. It is important to note that this condition assumes that everything works and the person is not paralyzed. There are different types of apraxia, each with its own set of symptoms and characteristics.

Limb kinetic apraxia is a type of apraxia that affects a person’s ability to make fine of delicate movements. This can include tasks such as buttoning a shirt of tying shoelaces.

Ideomotor apraxia, on the other hand, is an inability to carry out learned tasks when given the necessary objects. For example, a person with ideomotor apraxia may try to write with a hairbrush instead of using it to brush their hair.

Constructional apraxia affects a person’s ability to copy a picture of combine parts of something to form a whole. This can include tasks such as building a puzzle of drawing a picture.

Ideational apraxia is an inability to follow a sequence of actions in the correct order. For example, a person with ideational apraxia may struggle to take a match out of a box and strike it with their left hand.

Finally, oculomotor apraxia affects a person’s ability to control eye movements. This can make it difficult for them to track moving objects of read smoothly.

Overall, apraxia can have a significant impact on a person’s ability to carry out everyday tasks. However, with the right support and treatment, many people with apraxia are able to improve their abilities and maintain their independence.

Overview of Cranial Nerves and Their Functions

The cranial nerves are a complex system of nerves that originate from the brain and control various functions of the head and neck. There are twelve cranial nerves, each with a specific function and origin. The following table provides a simplified overview of the cranial nerves, including their origin, skull exit, modality, and functions.

The first cranial nerve, the olfactory nerve, originates from the telencephalon and exits through the cribriform plate. It is a sensory nerve that controls the sense of smell. The second cranial nerve, the optic nerve, originates from the diencephalon and exits through the optic foramen. It is a sensory nerve that controls vision.

The third cranial nerve, the oculomotor nerve, originates from the midbrain and exits through the superior orbital fissure. It is a motor nerve that controls eye movement, pupillary constriction, and lens accommodation. The fourth cranial nerve, the trochlear nerve, also originates from the midbrain and exits through the superior orbital fissure. It is a motor nerve that controls eye movement.

The fifth cranial nerve, the trigeminal nerve, originates from the pons and exits through different foramina depending on the division. It is a mixed nerve that controls chewing and sensation of the anterior 2/3 of the scalp. It also tenses the tympanic membrane to dampen loud noises.

The sixth cranial nerve, the abducens nerve, originates from the pons and exits through the superior orbital fissure. It is a motor nerve that controls eye movement. The seventh cranial nerve, the facial nerve, also originates from the pons and exits through the internal auditory canal. It is a mixed nerve that controls facial expression, taste of the anterior 2/3 of the tongue, and tension on the stapes to dampen loud noises.

The eighth cranial nerve, the vestibulocochlear nerve, originates from the pons and exits through the internal auditory canal. It is a sensory nerve that controls hearing. The ninth cranial nerve, the glossopharyngeal nerve, originates from the medulla and exits through the jugular foramen. It is a mixed nerve that controls taste of the posterior 1/3 of the tongue, elevation of the larynx and pharynx, and swallowing.

The tenth cranial nerve, the vagus nerve, also originates from the medulla and exits through the jugular foramen. It is a mixed nerve that controls swallowing, voice production, and parasympathetic supply to nearly all thoracic and abdominal viscera. The eleventh cranial nerve, the accessory nerve, originates from the medulla and exits through the jugular foramen. It is a motor nerve that controls shoulder shrugging and head turning.

The twelfth cranial nerve, the hypoglossal nerve, originates from the medulla and exits through the hypoglossal canal. It is a motor nerve that controls tongue movement. Overall, the cranial nerves play a crucial role in controlling various functions of the head and neck, and any damage of dysfunction can have significant consequences.

Tyrosine is converted to L-DOPA by the enzyme tyrosine hydroxylase. L-DOPA is then converted to dopamine by the enzyme dopa decarboxylase.

Neurotransmitters are substances used by neurons to communicate with each other and with target tissues. They are synthesized and released from nerve endings into the synaptic cleft, where they bind to receptor proteins in the cellular membrane of the target tissue. Neurotransmitters can be classified into different types, including small molecules (such as acetylcholine, dopamine, norepinephrine, serotonin, and GABA) and large molecules (such as neuropeptides). They can also be classified as excitatory or inhibitory. Receptors can be ionotropic or metabotropic, and the effects of neurotransmitters can be fast of slow. Some important neurotransmitters include acetylcholine, dopamine, GABA, norepinephrine, and serotonin. Each neurotransmitter has a specific synthesis, breakdown, and receptor type. Understanding neurotransmitters is important for understanding the function of the nervous system and for developing treatments for neurological and psychiatric disorders.

Overview of Cranial Nerves and Their Functions

The cranial nerves are a complex system of nerves that originate from the brain and control various functions of the head and neck. There are twelve cranial nerves, each with a specific function and origin. The following table provides a simplified overview of the cranial nerves, including their origin, skull exit, modality, and functions.

The first cranial nerve, the olfactory nerve, originates from the telencephalon and exits through the cribriform plate. It is a sensory nerve that controls the sense of smell. The second cranial nerve, the optic nerve, originates from the diencephalon and exits through the optic foramen. It is a sensory nerve that controls vision.

The third cranial nerve, the oculomotor nerve, originates from the midbrain and exits through the superior orbital fissure. It is a motor nerve that controls eye movement, pupillary constriction, and lens accommodation. The fourth cranial nerve, the trochlear nerve, also originates from the midbrain and exits through the superior orbital fissure. It is a motor nerve that controls eye movement.

The fifth cranial nerve, the trigeminal nerve, originates from the pons and exits through different foramina depending on the division. It is a mixed nerve that controls chewing and sensation of the anterior 2/3 of the scalp. It also tenses the tympanic membrane to dampen loud noises.

The sixth cranial nerve, the abducens nerve, originates from the pons and exits through the superior orbital fissure. It is a motor nerve that controls eye movement. The seventh cranial nerve, the facial nerve, also originates from the pons and exits through the internal auditory canal. It is a mixed nerve that controls facial expression, taste of the anterior 2/3 of the tongue, and tension on the stapes to dampen loud noises.

The eighth cranial nerve, the vestibulocochlear nerve, originates from the pons and exits through the internal auditory canal. It is a sensory nerve that controls hearing. The ninth cranial nerve, the glossopharyngeal nerve, originates from the medulla and exits through the jugular foramen. It is a mixed nerve that controls taste of the posterior 1/3 of the tongue, elevation of the larynx and pharynx, and swallowing.

The tenth cranial nerve, the vagus nerve, also originates from the medulla and exits through the jugular foramen. It is a mixed nerve that controls swallowing, voice production, and parasympathetic supply to nearly all thoracic and abdominal viscera. The eleventh cranial nerve, the accessory nerve, originates from the medulla and exits through the jugular foramen. It is a motor nerve that controls shoulder shrugging and head turning.

The twelfth cranial nerve, the hypoglossal nerve, originates from the medulla and exits through the hypoglossal canal. It is a motor nerve that controls tongue movement. Overall, the cranial nerves play a crucial role in controlling various functions of the head and neck, and any damage of dysfunction can have significant consequences.

Alzheimer’s disease is associated with the presence of Hirano bodies.

Schizophrenia is a pathology that is characterized by a number of structural and functional brain alterations. Structural alterations include enlargement of the ventricles, reductions in total brain and gray matter volume, and regional reductions in the amygdala, parahippocampal gyrus, and temporal lobes. Antipsychotic treatment may be associated with gray matter loss over time, and even drug-naïve patients show volume reductions. Cerebral asymmetry is also reduced in affected individuals and healthy relatives. Functional alterations include diminished activation of frontal regions during cognitive tasks and increased activation of temporal regions during hallucinations. These findings suggest that schizophrenia is associated with both macroscopic and functional changes in the brain.

Broca’s aphasia is also known as non-fluent aphasia, while Wernicke’s aphasia is referred to as fluent aphasia.

Broca’s and Wernicke’s are two types of expressive dysphasia, which is characterized by difficulty producing speech despite intact comprehension. Dysarthria is a type of expressive dysphasia caused by damage to the speech production apparatus, while Broca’s aphasia is caused by damage to the area of the brain responsible for speech production, specifically Broca’s area located in Brodmann areas 44 and 45. On the other hand, Wernicke’s aphasia is a type of receptive of fluent aphasia caused by damage to the comprehension of speech, while the actual production of speech remains normal. Wernicke’s area is located in the posterior part of the superior temporal gyrus in the dominant hemisphere, within Brodmann area 22.

A fenestrated cavum septum pellucidum is linked to dementia pugilistica.

Dementia Pugilistica: A Neurodegenerative Condition Resulting from Neurotrauma

Dementia pugilistica, also known as chronic traumatic encephalopathy (CTE), is a neurodegenerative condition that results from neurotrauma. It is commonly seen in boxers and NFL players, but can also occur in anyone with neurotrauma. The condition is characterized by symptoms such as gait ataxia, slurred speech, impaired hearing, tremors, disequilibrium, neurobehavioral disturbances, and progressive cognitive decline.

Most cases of dementia pugilistica present with early onset cognitive deficits, and behavioral signs exhibited by patients include aggression, suspiciousness, paranoia, childishness, hypersexuality, depression, and restlessness. The progression of the condition leads to more prominent behavioral symptoms such as difficulty with impulse control, irritability, inappropriateness, and explosive outbursts of aggression.

Neuropathological abnormalities have been identified in CTE, with the most unique feature being the abnormal accumulation of tau in neurons and glia in an irregular, focal, perivascular distribution and at the depths of cortical sulci. Abnormalities of the septum pellucidum, such as cavum and fenestration, are also a common feature.

While the condition has become increasingly rare due to the progressive improvement in sports safety, it is important to recognize the potential long-term consequences of repeated head injuries and take steps to prevent them.

– A Battle’s sign is a physical indication of a basal skull fracture.
– Babinski’s sign is a clinical sign that suggests an upper motor neuron lesion.
– Kernig’s sign is a clinical sign that indicates meningeal irritation.
– Russell’s sign is characterized by scarring on the knuckles and back of the hand, and it is indicative of repeated induced vomiting.

Hoover’s Sign for Differentiating Organic and Functional Weakness

Functional weakness refers to weakness that is inconsistent with any identifiable neurological disease and may be diagnosed as conversion disorder of dissociative motor disorder. To differentiate between organic and functional weakness of pyramidal origin, Dr. Charles Franklin Hoover described Hoover’s sign over 100 years ago.

This test is typically performed on the lower limbs and is useful when the nature of hemiparesis is uncertain. When a person with organic hemiparesis is asked to flex the hip of their normal leg against resistance, they will not exert pressure on the examiner’s hand placed under the heel on the affected side. However, in hysterical weakness, the examiner will feel increased pressure on their hand. Hoover’s sign is a valuable tool for distinguishing between organic and functional weakness.

Understanding Action Potentials in Neurons and Muscle Cells

The membrane potential is a crucial aspect of cell physiology, and it exists across the plasma membrane of most cells. However, in neurons and muscle cells, this membrane potential can change over time. When a cell is not stimulated, it is in a resting state, and the inside of the cell is negatively charged compared to the outside. This resting membrane potential is typically around -70mV, and it is maintained by the Na/K pump, which maintains a high concentration of Na outside and K inside the cell.

To trigger an action potential, the membrane potential must be raised to around -55mV. This can occur when a neurotransmitter binds to the postsynaptic neuron and opens some ion channels. Once the membrane potential reaches -55mV, a cascade of events is initiated, leading to the opening of a large number of Na channels and causing the cell to depolarize. As the membrane potential reaches around +40 mV, the Na channels close, and the K gates open, allowing K to flood out of the cell and causing the membrane potential to fall back down. This process is irreversible and is critical for the transmission of signals in neurons and the contraction of muscle cells.

Neurotransmitters are substances used by neurons to communicate with each other and with target tissues. They are synthesized and released from nerve endings into the synaptic cleft, where they bind to receptor proteins in the cellular membrane of the target tissue. Neurotransmitters can be classified into different types, including small molecules (such as acetylcholine, dopamine, norepinephrine, serotonin, and GABA) and large molecules (such as neuropeptides). They can also be classified as excitatory or inhibitory. Receptors can be ionotropic or metabotropic, and the effects of neurotransmitters can be fast of slow. Some important neurotransmitters include acetylcholine, dopamine, GABA, norepinephrine, and serotonin. Each neurotransmitter has a specific synthesis, breakdown, and receptor type. Understanding neurotransmitters is important for understanding the function of the nervous system and for developing treatments for neurological and psychiatric disorders.

The tuberoinfundibular pathway links the hypothalamus with the pituitary gland, rather than the pineal gland.

Neurotransmitters are substances used by neurons to communicate with each other and with target tissues. They are synthesized and released from nerve endings into the synaptic cleft, where they bind to receptor proteins in the cellular membrane of the target tissue. Neurotransmitters can be classified into different types, including small molecules (such as acetylcholine, dopamine, norepinephrine, serotonin, and GABA) and large molecules (such as neuropeptides). They can also be classified as excitatory or inhibitory. Receptors can be ionotropic or metabotropic, and the effects of neurotransmitters can be fast of slow. Some important neurotransmitters include acetylcholine, dopamine, GABA, norepinephrine, and serotonin. Each neurotransmitter has a specific synthesis, breakdown, and receptor type. Understanding neurotransmitters is important for understanding the function of the nervous system and for developing treatments for neurological and psychiatric disorders.

The Basal Ganglia: Functions and Disorders

The basal ganglia are a group of subcortical structures that play a crucial role in controlling movement and some cognitive processes. The components of the basal ganglia include the striatum (caudate, putamen, nucleus accumbens), subthalamic nucleus, globus pallidus, and substantia nigra (divided into pars compacta and pars reticulata). The putamen and globus pallidus are collectively referred to as the lenticular nucleus.

The basal ganglia are connected in a complex loop, with the cortex projecting to the striatum, the striatum to the internal segment of the globus pallidus, the internal segment of the globus pallidus to the thalamus, and the thalamus back to the cortex. This loop is responsible for regulating movement and cognitive processes.

However, problems with the basal ganglia can lead to several conditions. Huntington’s chorea is caused by degeneration of the caudate nucleus, while Wilson’s disease is characterized by copper deposition in the basal ganglia. Parkinson’s disease is associated with degeneration of the substantia nigra, and hemiballism results from damage to the subthalamic nucleus.

In summary, the basal ganglia are a crucial part of the brain that regulate movement and some cognitive processes. Disorders of the basal ganglia can lead to significant neurological conditions that affect movement and other functions.

The Cerebral Cortex and Neocortex

The cerebral cortex is the outermost layer of the cerebral hemispheres and is composed of three parts: the archicortex, paleocortex, and neocortex. The neocortex accounts for 90% of the cortex and is involved in higher functions such as thought and language. It is divided into 6-7 layers, with two main cell types: pyramidal cells and nonpyramidal cells. The surface of the neocortex is divided into separate areas, each given a number by Brodmann (e.g. Brodmann’s area 17 is the primary visual cortex). The surface is folded to increase surface area, with grooves called sulci and ridges called gyri. The neocortex is responsible for higher cognitive functions and is essential for human consciousness.

Gerstmann’s Syndrome: Symptoms and Brain Lesions

Gerstmann’s syndrome is a condition that is characterized by several symptoms, including dyscalculia, dysgraphia, finger agnosia, and right-left disorientation. Patients with this syndrome have been found to have lesions in areas such as the left frontal posterior, left parietal, temporal, and occipital lobes. The left angular gyrus, which is located at the junction of the temporal, occipital, and parietal lobes, seems to be the main area of overlap. Although the function of the angular gyrus is not well understood, it is believed to be involved in various functions such as calculation, spatial reasoning, understanding of ordinal concepts, and comprehension of metaphors.

Organic processes are indicated by the presence of visual hallucinations.

Perseveration: The Clinical Symptoms in Chronic Schizophrenia and Organic Dementia

Perseveration is a common behavior observed in patients with organic brain involvement. It is characterized by the conscious continuation of an act of an idea. This behavior is frequently seen in patients with delirium, epilepsy, dementia, schizophrenia, and normal individuals under extreme fatigue of drug-induced states.

In chronic schizophrenia and organic dementia, perseveration is a prominent symptom. Patients with these conditions tend to repeat the same words, phrases, of actions over and over again, even when it is no longer appropriate of relevant to the situation. This behavior can be frustrating for caregivers and family members, and it can also interfere with the patient’s ability to communicate effectively.

In schizophrenia, perseveration is often associated with disorganized thinking and speech. Patients may jump from one topic to another without any logical connection, and they may repeat the same words of phrases in an attempt to express their thoughts. In organic dementia, perseveration is a sign of cognitive decline and memory impairment. Patients may repeat the same stories of questions, forgetting that they have already asked of answered them.

Overall, perseveration is a common symptom in patients with organic brain involvement, and it can have a significant impact on their daily functioning and quality of life. Understanding this behavior is essential for effective management and treatment of these conditions.

Alzheimer’s disease is not characterized by significant frontal lobe atrophy, but rather by early medial temporal lobe atrophy (MTA) on MRI, particularly in the hippocampus, entorhinal cortex, amygdala, and parahippocampus. In contrast, frontotemporal lobar degeneration (FTLD) typically affects the frontal and anterior temporal lobes in behavioral variant frontotemporal dementia (bvFTD of Pick’s disease), the left anterior temporal lobe in semantic dementia (SD), and the left perisylvian fissure in progressive nonfluent aphasia (PNFA).

Frontotemporal Lobar Degeneration (FTLD) is a pathological term that refers to a group of neurodegenerative disorders that affect the frontal and temporal lobes of the brain. FTLD is classified into several subtypes based on the main protein component of neuronal and glial abnormal inclusions and their distribution. The three main proteins associated with FTLD are Tau, TDP-43, and FUS. Each FTD clinical phenotype has been associated with different proportions of these proteins. Macroscopic changes in FTLD include atrophy of the frontal and temporal lobes, with focal gyral atrophy that resembles knives. Microscopic changes in FTLD-Tau include neuronal and glial tau aggregation, with further sub-classification based on the existence of different isoforms of tau protein. FTLD-TDP is characterized by cytoplasmic inclusions of TDP-43 in neurons, while FTLD-FUS is characterized by cytoplasmic inclusions of FUS.

Neurotransmitters are substances used by neurons to communicate with each other and with target tissues. They are synthesized and released from nerve endings into the synaptic cleft, where they bind to receptor proteins in the cellular membrane of the target tissue. Neurotransmitters can be classified into different types, including small molecules (such as acetylcholine, dopamine, norepinephrine, serotonin, and GABA) and large molecules (such as neuropeptides). They can also be classified as excitatory or inhibitory. Receptors can be ionotropic or metabotropic, and the effects of neurotransmitters can be fast of slow. Some important neurotransmitters include acetylcholine, dopamine, GABA, norepinephrine, and serotonin. Each neurotransmitter has a specific synthesis, breakdown, and receptor type. Understanding neurotransmitters is important for understanding the function of the nervous system and for developing treatments for neurological and psychiatric disorders.

Prolactin secretion from the anterior pituitary gland is inhibited by dopamine, which is also referred to as prolactin-inhibiting factor (PIF) and prolactin-inhibiting hormone (PIH). The reason why antipsychotic medications are linked to hyperprolactinaemia is due to the antagonism of dopamine receptors. On the other hand, serotonin and melatonin seem to stimulate prolactin secretion. While animal studies have indicated that adrenaline and noradrenaline can decrease prolactin secretion, their effect is not as significant as that of dopamine.

Abnormal movements known as athetoid movements are commonly associated with issues in the basal ganglia.

Cerebellar Dysfunction: Symptoms and Signs

Cerebellar dysfunction is a condition that affects the cerebellum, a part of the brain responsible for coordinating movement and balance. The symptoms and signs of cerebellar dysfunction include ataxia, intention tremor, nystagmus, broad-based gait, slurred speech, dysdiadochokinesis, and dysmetria (lack of finger-nose coordination).

Ataxia refers to the lack of coordination of voluntary movements, resulting in unsteady gait, difficulty with balance, and clumsiness. Intention tremor is a type of tremor that occurs during voluntary movements, such as reaching for an object. Nystagmus is an involuntary movement of the eyes, characterized by rapid, jerky movements.

Broad-based gait refers to a wide stance while walking, which is often seen in individuals with cerebellar dysfunction. Slurred speech, also known as dysarthria, is a common symptom of cerebellar dysfunction, which affects the ability to articulate words clearly. Dysdiadochokinesis is the inability to perform rapid alternating movements, such as tapping the fingers on the palm of the hand.

Dysmetria refers to the inability to accurately judge the distance and direction of movements, resulting in errors in reaching for objects of touching the nose with the finger. These symptoms and signs of cerebellar dysfunction can be caused by a variety of conditions, including stroke, multiple sclerosis, and alcoholism. Treatment depends on the underlying cause and may include medications, physical therapy, and surgery.

As an AI language model, I cannot provide a response without knowing the context of the rewrite you are referring to. Please provide more information of context so that I can assist you better.

Serotonin (5-hydroxytryptamine, 5-HT) receptors are primarily G protein receptors, except for 5-HT3, which is a ligand-gated receptor. It is important to remember that 5-HT3 is most commonly associated with nausea. Additionally, 5-HT7 is linked to circadian rhythms. The stimulation of 5-HT2 receptors is believed to be responsible for the side effects of insomnia, agitation, and sexual dysfunction that are associated with the use of selective serotonin reuptake inhibitors (SSRIs).

Neurotransmitters are substances used by neurons to communicate with each other and with target tissues. They are synthesized and released from nerve endings into the synaptic cleft, where they bind to receptor proteins in the cellular membrane of the target tissue. Neurotransmitters can be classified into different types, including small molecules (such as acetylcholine, dopamine, norepinephrine, serotonin, and GABA) and large molecules (such as neuropeptides). They can also be classified as excitatory or inhibitory. Receptors can be ionotropic or metabotropic, and the effects of neurotransmitters can be fast of slow. Some important neurotransmitters include acetylcholine, dopamine, GABA, norepinephrine, and serotonin. Each neurotransmitter has a specific synthesis, breakdown, and receptor type. Understanding neurotransmitters is important for understanding the function of the nervous system and for developing treatments for neurological and psychiatric disorders.

Brain Anatomy

The brain is a complex organ with various regions responsible for different functions. The major areas of the cerebrum (telencephalon) include the frontal lobe, parietal lobe, occipital lobe, temporal lobe, insula, corpus callosum, fornix, anterior commissure, and striatum. The cerebrum is responsible for complex learning, language acquisition, visual and auditory processing, memory, and emotion processing.

The diencephalon includes the thalamus, hypothalamus and pituitary, pineal gland, and mammillary body. The thalamus is a major relay point and processing center for all sensory impulses (excluding olfaction). The hypothalamus and pituitary are involved in homeostasis and hormone release. The pineal gland secretes melatonin to regulate circadian rhythms. The mammillary body is a relay point involved in memory.

The cerebellum is primarily concerned with movement and has two major hemispheres with an outer cortex made up of gray matter and an inner region of white matter. The cerebellum provides precise timing and appropriate patterns of skeletal muscle contraction for smooth, coordinated movements and agility needed for daily life.

The brainstem includes the substantia nigra, which is involved in controlling and regulating activities of the motor and premotor cortical areas for smooth voluntary movements, eye movement, reward seeking, the pleasurable effects of substance misuse, and learning.

An infarction to the left posterior cerebral artery typically results in pure alexia, also known as alexia without agraphia, which is characterized by the inability to read but the ability to write.

Brain Blood Supply and Consequences of Occlusion

The brain receives blood supply from the internal carotid and vertebral arteries, which form the circle of Willis. The circle of Willis acts as a shunt system in case of vessel damage. The three main vessels arising from the circle are the anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA). Occlusion of these vessels can result in various neurological deficits. ACA occlusion may cause hemiparesis of the contralateral foot and leg, sensory loss, and frontal signs. MCA occlusion is the most common and can lead to hemiparesis, dysphasia/aphasia, neglect, and visual field defects. PCA occlusion may cause alexia, loss of sensation, hemianopia, prosopagnosia, and cranial nerve defects. It is important to recognize these consequences to provide appropriate treatment.

The Cerebral Cortex and Neocortex

The cerebral cortex is the outermost layer of the cerebral hemispheres and is composed of three parts: the archicortex, paleocortex, and neocortex. The neocortex accounts for 90% of the cortex and is involved in higher functions such as thought and language. It is divided into 6-7 layers, with two main cell types: pyramidal cells and nonpyramidal cells. The surface of the neocortex is divided into separate areas, each given a number by Brodmann (e.g. Brodmann’s area 17 is the primary visual cortex). The surface is folded to increase surface area, with grooves called sulci and ridges called gyri. The neocortex is responsible for higher cognitive functions and is essential for human consciousness.

The Cerebellum: Anatomy and Function

The cerebellum is a part of the brain that consists of two hemispheres and a median vermis. It is separated from the cerebral hemispheres by the tentorium cerebelli and connected to the brain stem by the cerebellar peduncles. Anatomically, it is divided into three lobes: the flocculonodular lobe, anterior lobe, and posterior lobe. Functionally, it is divided into three regions: the vestibulocerebellum, spinocerebellum, and cerebrocerebellum.

The vestibulocerebellum, located in the flocculonodular lobe, is responsible for balance and spatial orientation. The spinocerebellum, located in the medial section of the anterior and posterior lobes, is involved in fine-tuned body movements. The cerebrocerebellum, located in the lateral section of the anterior and posterior lobes, is involved in planning movement and the conscious assessment of movement.

Overall, the cerebellum plays a crucial role in motor coordination and control. Its different regions and lobes work together to ensure smooth and precise movements of the body.

Catecholamines are a group of chemical compounds that have a distinct structure consisting of a benzene ring with two hydroxyl groups, an intermediate ethyl chain, and a terminal amine group. These compounds play an important role in the body and are involved in various physiological processes. The three main catecholamines found in the body are dopamine, adrenaline, and noradrenaline. All of these compounds are derived from the amino acid tyrosine. Overall, catecholamines are essential for maintaining proper bodily functions and are involved in a wide range of physiological processes.

Norepinephrine: Synthesis, Release, and Breakdown

Norepinephrine is synthesized from tyrosine through a series of enzymatic reactions. The first step involves the conversion of tyrosine to L-DOPA by tyrosine hydroxylase. L-DOPA is then converted to dopamine by DOPA decarboxylase. Dopamine is further converted to norepinephrine by dopamine beta-hydroxylase. Finally, norepinephrine is converted to epinephrine by phenylethanolamine-N-methyltransferase.

The primary site of norepinephrine release is the locus coeruleus, also known as the blue spot, which is located in the pons. Once released, norepinephrine is broken down by two enzymes: catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO). These enzymes play a crucial role in regulating the levels of norepinephrine in the body.

Aphasia is a language impairment that affects the production of comprehension of speech, as well as the ability to read of write. The areas involved in language are situated around the Sylvian fissure, referred to as the ‘perisylvian language area’. For repetition, the primary auditory cortex, Wernicke, Broca via the Arcuate fasciculus (AF), Broca recodes into articulatory plan, primary motor cortex, and pyramidal system to cranial nerves are involved. For oral reading, the visual cortex to Wernicke and the same processes as for repetition follows. For writing, Wernicke via AF to premotor cortex for arm and hand, movement planned, sent to motor cortex. The classification of aphasia is complex and imprecise, with the Boston Group classification and Luria’s aphasia interpretation being the most influential. The important subtypes of aphasia include global aphasia, Broca’s aphasia, Wernicke’s aphasia, conduction aphasia, anomic aphasia, transcortical motor aphasia, and transcortical sensory aphasia. Additional syndromes include alexia without agraphia, alexia with agraphia, and pure word deafness.