NEET MDS Synopsis
CENTRAL NERVOUS SYSTEM PHARMACOLOGY
Pharmacology
CNS acting drugs are of major therapeutic and clinical importance.
They can produce diverse physiologicaland psychologicaleffects such as:
•Induction of Anesthesia
•Relief of Pain
•Prevention of Epileptic seizures
•Reduction of Anxiety
•Treatment of Parkinsonism
•Treatment of Alzheimer's disease
•Treatment of Depression
•Centrally acting drugs also include drugs that are administered without medical intervention like tea, coffee, nicotine, and opiates.
The Skull
AnatomyThe skull, the skeleton of the head, is the most complex bony structure in the body because it:
Encloses the brain, which is irregular in shape;
Houses the organs of special senses for seeing, hearing, tasting, and smelling; and
Surrounds the openings in to the digestive and respiratory tracts.
In the anatomical position, the skull is oriented so that the inferior margin of the orbit (eye socket) and the superior margin of the external acoustic meatus (auditory canal) are horizontal. This is called the orbitomenial plane (Frankfort plane).
The term cranium (L. skull) is sometimes used when referring to the skull without the mandible (lower jaw), but the cranium is often used when referring to the part of the skull containing the brain.
The superior part is the box-like structure called the calvaria (cranial vault, brain case); the remainder of the cranium, including the maxilla (upper jaw), orbits (eyeball sockets) and nasal cavities, forms the facial skeleton.
The term skullcap (calotte) refers to the superior part of the calvaria, which is removed during autopsies and dissections. The inferior aspect of the cranium is called the cranial base.
Muscle pathology
General Pathology
Muscle pathology
1. Myasthenia gravis
a. An autoimmune disease caused by autoantibodies to acetylcholine receptors at the neuromuscular junctions.
b. Characterized by muscle weakness or the inability to maintain long durations of muscle contractions; this worsens during exercise but recovers after rest.
c. Affects various muscle groups, including:
(1) Eyes—diplopia, ptosis.
(2) Neck—dysphagia, problems swallowing or speaking.
(3) Extremities—arms and legs.
d. Treatment: cholinesterase inhibitors(neostigmine), anti-immune therapy.
2. Muscle tumors
a. Rhabdomyoma—benign tumor of skeletal muscle.
b. Leiomyoma
(1) Benign tumor of smooth muscle.
(2) Most common tumor found in women.
(3) Usually affects the uterus, although it can occur anywhere.
c. Rhabdomyosarcoma
(1) Malignant tumor of skeletal muscle.
(2) Most common sarcoma found in children.
(3) Usually affects head and neck region—orbit, nasal cavity, and nasopharynx.
Hypercementosis
PeriodontologyHypercementosis
Hypercementosis is a dental condition characterized by the excessive
deposition of cementum on the roots of teeth. This condition can have various
clinical implications and is associated with several underlying factors.
Understanding hypercementosis is essential for dental professionals in
diagnosing and managing related conditions.
Characteristics of Hypercementosis
Definition:
Hypercementosis is defined as a generalized thickening of the
cementum, often accompanied by nodular enlargement of the apical third
of the root. It can also manifest as spike-like excrescences known as
cemental spikes.
Forms of Hypercementosis:
Generalized Type: Involves a uniform thickening of
cementum across multiple teeth.
Localized Type: Characterized by nodular
enlargements or cemental spikes, which may result from:
Coalescence of cementicles adhering to the root.
Calcification of periodontal fibers at their insertion points
into the cementum.
Radiographic Appearance
Radiographic Features:
On radiographs, hypercementosis is identified by the presence of a
radiolucent shadow of the periodontal ligament and a radiopaque lamina
dura surrounding the area of hypercementosis, similar to normal
cementum.
Differentiation:
Hypercementosis can be differentiated from other conditions such
as periapical cemental dysplasia, condensing osteitis, and focal
periapical osteopetrosis, as these entities are located outside the
shadow of the periodontal ligament and lamina dura.
Etiology of Hypercementosis
Varied Etiology:
The exact cause of hypercementosis is not completely understood, but
several factors have been identified:
Spike-like Hypercementosis: Often results from
excessive tension due to orthodontic appliances or occlusal forces.
Generalized Hypercementosis: Can occur in
various circumstances, including:
Teeth Without Antagonists: In cases where
teeth lack opposing teeth, hypercementosis may develop as a
compensatory mechanism to keep pace with excessive tooth
eruption.
Low-Grade Periapical Irritation: Associated
with pulp disease, where hypercementosis serves as compensation
for the loss of fibrous attachment to the tooth.
Systemic Associations:
Hypercementosis may also be observed in systemic conditions,
including:
Paget’s Disease: Characterized by
hypercementosis of the entire dentition.
Other Conditions: Acromegaly, arthritis,
calcinosis, rheumatic fever, and thyroid goiter have also been
linked to hypercementosis.
Clinical Implications
Diagnosis:
Recognizing hypercementosis is important for accurate diagnosis and
treatment planning. Radiographic evaluation is essential for
distinguishing hypercementosis from other dental pathologies.
Management:
While hypercementosis itself may not require treatment, it can
complicate dental procedures such as extractions or endodontic
treatments. Understanding the condition can help clinicians anticipate
potential challenges.
Monitoring:
Regular monitoring of patients with known systemic conditions
associated with hypercementosis is important to manage any potential
complications.
Control of processes in the stomach
PhysiologyControl of processes in the stomach:
The stomach, like the rest of the GI tract, receives input from the autonomic nervous system. Positive stimuli come from the parasympathetic division through the vagus nerve. This stimulates normal secretion and motility of the stomach. Control occurs in several phases:
Cephalic phase stimulates secretion in anticipation of eating to prepare the stomach for reception of food. The secretions from cephalic stimulation are watery and contain little enzyme or acid.
Gastric phase of control begins with a direct response to the contact of food in the stomach and is due to stimulation of pressoreceptors in the stomach lining which result in ACh and histamine release triggered by the vagus nerve. The secretion and motility which result begin to churn and liquefy the chyme and build up pressure in the stomach. Chyme surges forward as a result of muscle contraction but is blocked from entering the duodenum by the pyloric sphincter. A phenomenon call retropulsion occurs in which the chyme surges backward only to be pushed forward once again into the pylorus. The presence of this acid chyme in the pylorus causes the release of a hormone called gastrin into the bloodstream. Gastrin has a positive feedback effect on the motility and acid secretion of the stomach. This causes more churning, more pressure, and eventually some chyme enters the duodenum.
Intestinal phase of stomach control occurs. At first this involves more gastrin secretion from duodenal cells which acts as a "go" signal to enhance the stomach action already occurring. But as more acid chyme enters the duodenum the decreasing pH inhibits gastrin secretion and causes the release of negative or "stop" signals from the duodenum.
These take the form of chemicals called enterogastrones which include GIP (gastric inhibitory peptide). GIP inhibits stomach secretion and motility and allows time for the digestive process to proceed in the duodenum before it receives more chyme. The enterogastric reflex also reduces motility and forcefully closes the pyloric sphincter. Eventually as the chyme is removed, the pH increases and gastrin and the "go" signal resumes and the process occurs all over again. This series of "go" and "stop" signals continues until stomach emptying is complete.
Ketamine
Pharmacology
Ketamine
- Causes a dissociative anesthesia.
- Is similar to but less potent than phencyclidine.
- Induces amnesia, analgesia, catalepsy and anesthesia, but does not induce convulsions.
- The principal disadvantage of ketamine is its adverse psychic effects during emergence from anesthesia. These include: hallucinations, changes in mood and body image.
- During anesthesia, many of the protective reflexes are maintained, such as laryngeal, pharyngeal, eyelid and corneal reflexes.
- Muscle relaxation is poor.
- It is not indicated for intracranial operations because it increases cerebrospinal fluid pressure.
- Respiration is well maintained.
- Arterial blood pressure, cardiac output, and heart rate are all elevated.
Methicillin
Pharmacology
Methicillin
Methicillin is an antibiotic related to penicillin and other beta-lactam containing antibiotics. It is often used to treat infections caused by bacteria carrying an antibiotic resistance, e.g., staphylococci. As methicillin is deactivated by gastric acid, it has to be administered by injection.
Uses Methicillin serves a purpose in the laboratory to determine antibiotic sensitivity in microbiological culture.
Molecular techniques
General Pathology
Molecular techniques
Different molecular techniques such as fluorescent in situ hybridization, Southern blot, etc... can be used to detect genetic diseases.