NEET MDS Synopsis
AGENTS THAT DECREASE PERIPHERAL VASCULAR RESISTANCE (PVR)
Pharmacology
A. Sympathetic Nervous System Depressants
1. Antagonists
Both α-adrenoceptor antagonists and β-adrenoceptor antagonists are useful antihypertensives.
α-blocker Prazosin, phentolamine, phenoxybenzamine
β-blocker Propranolol ,Metoprolol, atenolol
α/β-blocker labetalol
2. Sympathetic depressants
a. Examples of peripherally acting agents include
reserpine This agent interferes with the storage of norepinephrine
quanethidine This agent interferes with the release of norepinephrine
trimethaphan This agent blocks transmission through autonomic ganglia.
b. Examples of Centrally acting agents include
alphamethyldopa
clonidine. These agents act by decreasing the number of impresses along sympathetic nerves.
Adverse Effect
include nasal congestion, postural hypotension, diarrhea, sexual dysfunction, dry mouth. sedation and drowsiness.
B. Directly Acting Vasodilators
Act on vascular smooth muscle cells independently of adrenergic nerves and adrenergic receptors.
Relaxation of vascular smooth muscle which leads to a decrease in peripheral vascular resistance.
Sites of action of vasodilators are many. For example
Calcium Channel Blocker’s MOA
. Decrease automaticity & conduction thru SA & AV nodes
. Decreased myocardial contractility
. Decreased peripheral & coronary
smooth muscle tone = decrease SVR
Potassium channels activators
minoxidil, cause vasodilation by activating potassium channels in vascular smooth muscle.
An increase in potassium conductance results in hyperpolarization of the cell membrane which is associated with relaxation of smooth muscle.
Nitrovasodilators, such as sodium nitroprusside,
Increase in intracellular cGMP. cGMP in turn activates a protein kinase. Directly-Acting Vasodilators are on occasion used alone but more frequently are used in combination with antihypertensive agents from other classes (esp. a β-blocker and a diuretic.)
The amino acids buffer system
Biochemistry
The amino acids buffer system
Amino acids contain in their molecule both an acidic (− COOH) and a basic (− NH2) group. They can be visualized as existing in the form of a neutral zwitterion in which a hydrogen atom can pass between the carboxyl and amino groups.
By the addition or subtraction of a hydrogen ion to or from the zwitterion, either the cation or anion form will be produced
Thus, when OH− ions are added to the solution of amino acid, they take up H+ from it to form water, and the anion is produced. If H+ ions are added, they are taken up by the zwitterion to produce the cation form. In practice, if NaOH is added, the salt H2N - CH2 - COONa would be formed. and the addition of HCl would result in the formation of amino acid hydrochloride.
PATHOPHYSIOLOGY OF THE CONDUCTION SYSTEM
Physiology
PATHOPHYSIOLOGY OF THE CONDUCTION SYSTEM
Cardiac arrhythmias = deviation from normal rate, rhythm
Heart block (types) = conduction system damage
Complete Heart Block = 3rd degree block
idioventricular beat (35-45/min)
Atria at normal sinus rhythm
Periods of asystole (dizziness, fainting)
Causes = myocardial infarction of ventricular septum, surgical correction of interseptal defects, drugs
Incomplete Heart Block = 2nd degree block
Not all atrial beats reach ventricle
Ventricular beat every 2nd, 3rd, etc. atrial beat, (2:1 block, 3:1 block)
Incomplete Heart Block = 1st degree block
All atrial beats reach ventricle
PR interval abnormally long = slower conduction
Bundle branch blocks (right or left)
Impulses travel down one side and cross over
Ventricular rate normal, QRS prolonged or abnormal
Fibrillation
Asynchronous contractions = twitching movements
Loss of synchrony = little to No output
Atrial Fibrillation
Irregular ventricular beat & depressed pumping efficiency
Atrial beat = 125 - 150/min, pulse feeble = 60 - 70/min
Treatment = Digitalis - reduces rate of ventricular contraction, reduces pulse deficit
Ventricular Fibrillation
Almost no blood pumped to systemic system
ECG = extremely bizarre
Several minutes = fatal
Treatment = defibrillation, cardiac massage can maintain some cardiac output
COPPER
Biochemistry
COPPER
The normal serum level of copper is 25 to 50 mg/dl.
Functions of copper
(a) Copper is necessary for iron absorption and incorporation of iron into hemoglobin.
(b) It is very essential for tyrosinase activity
(c) It is the co-factor for vitamin C requiring hydroxylation
(d) Copper increases the level of high density lipo protein and protects the heart.
Wilson’s disease
In case of Wilson’s disease ceruloplasmin level in blood is drastically reduced.
Wilson’s disease leads to
(i) Accumulation of copper in liver leads to hepatocellular degeneration and cirrhosis
(ii) Deposition of copper in brain basal ganglia leads to leticular degeneration
(iii) Copper deposits as green pigmented ring around cornea and the condition is called as Kayser-Kleischer ring
Over accumulation of copper can be treated by consumption of diet containg low copper and injection of D-penicillamine, which excretes copper through urine.
Menke’s kidney hair syndrome
It is X-linked defect. In this condition copper is absorbed by GI tract, but cannot be transported to blood. The defect in transport of copper to blood is due to absence of an intracellular copper binding ATPase.
Alcoholic cirrhosis
General Pathology
Alcoholic (nutritional, Laennec’s) cirrhosis
Pathology
Liver is at first enlarged (fatty change), then return to normal size and lastly, it becomes slightly reduced in size (1.2 kg or more).
- Cirrhosis is micronodular then macronodular then mixed.
M/E
Hepatocytes:- show fatty change that decreases progressively. Few hepatocytes show increased intracytoplasmic haemochromatosis.
b. Fibrous septa:- Regular margins between it and regenerating nodules.
-Moderate lymphocytic infiltrate.
– Slight bile ductular proliferation.
Prognosis:- It Progresses slowly over few years.
Keratinized Gingiva and Attached Gingiva
PeriodontologyKeratinized Gingiva and Attached Gingiva
The gingiva is an essential component of the periodontal tissues, providing
support and protection for the teeth. Understanding the characteristics of
keratinized gingiva, particularly attached gingiva, is crucial for assessing
periodontal health.
Keratinized Gingiva
Definition:
Keratinized gingiva refers to the gingival tissue that is covered by
a layer of keratinized epithelium, providing a protective barrier
against mechanical and microbial insults.
Areas of Keratinized Gingiva:
Attached Gingiva:
Extends from the gingival groove to the mucogingival junction.
Marginal Gingiva:
The free gingival margin that surrounds the teeth.
Hard Palate:
The roof of the mouth, which is also covered by keratinized
tissue.
Attached Gingiva
Location:
The attached gingiva is the portion of the gingiva that is firmly
bound to the underlying alveolar bone.
Width of Attached Gingiva:
The width of attached gingiva varies based on location and can
increase with age and in cases of supraerupted teeth.
Measurements:
Greatest Width:
Found in the incisor region:
Maxilla: 3.5 mm - 4.5 mm
Mandible: 3.3 mm - 3.9 mm
Narrowest Width:
Found in the posterior region:
Maxillary First Premolar: 1.9 mm
Mandibular First Premolar: 1.8 mm
Clinical Significance
Importance of Attached Gingiva:
The width of attached gingiva is important for periodontal health,
as it provides a buffer zone against mechanical forces and helps
maintain the integrity of the periodontal attachment.
Insufficient attached gingiva may lead to increased susceptibility
to periodontal disease and gingival recession.
Assessment:
Regular assessment of the width of attached gingiva is essential
during periodontal examinations to identify potential areas of concern
and to plan appropriate treatment strategies.
Rocky Mountain Spotted Fever
General Pathology
Rocky Mountain Spotted Fever (Spotted Fever; Tick Fever; Tick Typhus)
An acute febrile disease caused by Rickettsia rickettsii and transmitted by ixodid ticks, producing high fever, cough, and rash.
Symptoms and Signs
The incubation period averages 7 days but varies from 3 to 12 days; the shorter the incubation period, the more severe the infection. Onset is abrupt, with severe headache, chills, prostration, and muscular pains. Fever reaches 39.5 or 40° C (103 or 104° F) within several days and remains high (for 15 to 20 days in severe cases),
Between the 1st and 6th day of fever, most patients develop a rash on the wrists, ankles, palms, soles, and forearms that rapidly extends to the neck, face, axilla, buttocks, and trunk. Often, a warm water or alcohol compress brings out the rash. Initially macular and pink, it becomes maculopapular and darker. In about 4 days, the lesions become petechial and may coalesce to form large hemorrhagic areas that later ulcerate
Neurologic symptoms include headache, restlessness, insomnia, delirium, and coma, all indicative of encephalitis. Hypotension develops in severe cases. Hepatomegaly may be present, but jaundice is infrequent. Localized pneumonitis may occur. Untreated patients may develop pneumonia, tissue necrosis, and circulatory failure, with such sequelae as brain and heart damage. Cardiac arrest with sudden death occasionally occurs in fulminant cases.
Levels of Organization
PhysiologyLevels of Organization:
CHEMICAL LEVEL - includes all chemical substances necessary for life (see, for example, a small portion - a heme group - of a hemoglobin molecule); together form the next higher level
CELLULAR LEVEL - cells are the basic structural and functional units of the human body & there are many different types of cells (e.g., muscle, nerve, blood)
TISSUE LEVEL - a tissue is a group of cells that perform a specific function and the basic types of tissues in the human body include epithelial, muscle, nervous, and connective tissues
ORGAN LEVEL - an organ consists of 2 or more tissues that perform a particular function (e.g., heart, liver, stomach)
SYSTEM LEVEL - an association of organs that have a common function; the major systems in the human body include digestive, nervous, endocrine, circulatory, respiratory, urinary, and reproductive.
There are two types of cells that make up all living things on earth: prokaryotic and eukaryotic. Prokaryotic cells, like bacteria, have no 'nucleus', while eukaryotic cells, like those of the human body, do.