Physiology

TSH works on iodide trapping

ABC of Biochemistry 6th -308

Micelles provide a mechanism for solubilizing fat-soluble nutrients in the aqueous solution of the intestinal lumen until the nutrients can be brought into contact with and absorbed by the intestinal epithelial cells. Because vitamin D is fat soluble, it is absorbed in the same way as other dietary lipids.

Explanation : Anterior or Preoptic group- 1. Preoptic nucleus 2. Paraventricular nucleus 3. Anterior nucleus 4. Supraoptic nucleus 5. Suprachiasmatic nucleus
Middle or Tuberal group- 1. Dorsomedial nucleus 2. Ventromedial nucleus 3. Lateral nucleus 4. Arcuate (tuberal) nucleus
Posterior or Mamillary group- 1. Posterior nucleus 2. Mamillary body

Ref: Sembulingam 6th edition (Table- 149.1)

The two testes of the human adult form up to 120 million sperm each day.

Intrinsic factor of Castle, secreted by parietal cells of gastric glands plays an important role in erythropoiesis. It is necessary for the absorption of vitamin B12 (which is called extrinsic factor) from GI tract into the blood. Vitamin B12 is an important maturation factor during erythropoiesis. Absence of intrinsic factor in gastric juice causes deficiency of vitamin B12, leading to pernicious anaemia.

Folic acid acts as a catalyst in DNA synthesis.

Golgi apparatus sorts and packages proteins within a cell

During sleep:
1. Pulse & RR decreases
2. BP falls
3. Tendon relex lost

Vasoactive intestinal peptide (VIP) is a gastrointestinal (GI) neurocrine that causes relaxation of GI smooth muscle. For example, VIP mediates the relaxation response of the lower esophageal sphincter when a bolus of food approaches it, allowing passage of the bolus into the stomach.

Explanation:

কোন ব্যাখ্যা যোগ হয় নি।

Secretin is released from small intestine when stomach acid contents come to duodenum.
Functions:
• It inhibits gastric emptying to delay the acid contents of stomach to enter in the duodenum.
• It inhibits gastric secretion.
• It acts on pancreatic duct to produce large volume of watery, NaHCO₃ secretion.
• It stimulates the secretion of NaHCO₃ rich bile in the liver by acting on the bile ducts.

Normally, GFR is about 180 L/day, and tubular reabsorption is 178.5 L/day, leaving 1.5 L/day of fluid to be excreted in the urine.

Examples of Mechanoreceptors
Tactile receptors
1.Merkel cells- Specialised cells present in the epidermis, sense light touch and softness.
2. Meissner corpuscles- An encapsulated nerve ending, present at the upper part of the dermis. They can sense light touch and vibrations.
3. Ruffini endings- These are also encapsulated, present in the dermis. They sense heavy and continuous pressure.
4.Pacinian corpuscles- They are encapsulated by connective tissue, located deep in the dermis of the skin. They respond to deep pressure.

Propioreceptors
These receptors sense body movement and position and help in maintaining the posture. It is required for locomotion and motor skills.
1.Muscle spindles- sense muscular movement.
2.Golgi tendons- sense tension in the tendons during muscle contractions.
3.Joint receptors- sense movement in the ligaments.

Explanation : Root value for Jaw jerk is Pons – V cranial nerve, Biceps jerk is C5, C6,Triceps jerk is C6 to C8 , Supinator jerk or radial periosteal reflex is C7, C8 ,Wrist tendon or finger flexion reflex is C8, T1, Knee jerk or patellar tendon reflex is L2 to L4, Ankle jerk or Achilles tendon reflex is L5 to S2.
Ref : Sembulingam 6th edition (Table-142.3)

Prognathism is a feature of acromegaly

Explanation :

Ref : Sembulingam 6th edition (Table- 141.1)

Explanation : First order neurons (primary neurons) are bipolar cells in the retina. Axons from the bipolar cells synapse with dendrites of ganglionic cells. Second order neurons (secondary neurons) are the ganglionic cells in ganglionic cell layer of retina. Axons of the ganglionic cells form optic nerve. Optic nerve leaves the eye and terminates in lateral geniculate body. Third order neurons are in the lateral geniculate body. Fibers arising from here, reach the visual cortex.
Ref : Sembulingam 6th edition (Page- 989)

Explanation : Amplitude of accommodation varies with age. Amplitude of accommodation at different age groups is: 10 years = 11.0 D, 20 years = 9.5 D, 30 years = 7.5 D, 40 years = 5.5 D, 50 years = 2.0 D, 60 years = 1.2 D, 70 years = 1.0 D.
Ref : Sembulingam 6th edition (Page- 998)

This patient is most likely suffering from analgesic nephropathy in view of the chronic history of NSAID consumption. Chronic intake can result in papillary necrosis and tubulointerstitial nephritis leading to anaemia, UTIs and haematuria. Diagnosis is made by ultrasound or CT scan alongside this clinical picture. An ultrasound is particularly useful if patients complain of sudden flank pain which can result from sloughed papillae causing urinary obstructions. Antegrade pyelography (D) is used to investigate a potential area of obstruction within the kidney which is not indicated in this case. Retrograde pyelography (A) is conducted to investigate obstructions via a catheter. A renal biopsy (B) would be useful to assess the degree of damage to the kidney but this is not essential as stopping analgesics or replacing them with alternatives, such as paracetamol, can reduce or even improve the condition. An abdominal x-ray alone would not be a useful modality for revealing renal damage in this case (C).

Basal ganglia are part of extrapyramidal system. Hypothalamus is associated with temperature regulation. It controls food habit, emotion & sexual behavior.

Receptors of calcitonin are found in bone & kidney.

Orthotolidine test is used to detect blood in urine.

Explanation : Trigeminal nerve acts as afferent nerve in case of corneal,conjunctival & nasal superficial mucous membrane reflexes. Glossopharyngeal nerve acts as afferent nerve in case of uvular & pharyngeal reflex.
Ref : Sembulingam 6th edition (Table- 142.1)

Others are classical sites of insulin receptor.

Receptors are those in the rods and cones in the retina that respond to light are- photoreceptors

Intrinsic factor is secreted by the parietal cells of the gastric fundus (as is HCl). It is absorbed, with vitamin B12, in the ileum.

Effects of insulin on various tissues
Adipose tissue
Increased glucose entry Increased fatty acid
Increased glycerol phosphate synthesis Increased triglyceride deposition Activation of lipoprotein lipase Inhibition of hormone sensitive lipase Increased K+ uptake
Muscle
Increased glucose entry Increased glycogen synthesis Increased amino acid uptake
Increased protein synthesis in ribosomes Decreased protein catabolism
Decreased release of gluconeogenic amino acids Increased ketone uptake
Increased K+ uptake

Explanations:
In response to hypoxia kidney release erythropoietin that acts on bone marrow & stimulate erythropoiesis.

Cl- activates salivary alpha amylase.

• Intrapleural space: -8 mm Hg
• Joint synovial spaces: -4 to -6 mm Hg
• Epidural space: -4 to -6 mm Hg

Explanations:
The principal haemostatic mechanism is believed to be via extrinsic pathway which is assessed by PT.

Explanation : Superior semicircular canal gives response to rotation in anteroposterior plane (transverse axis). Horizontal semicircular canal gives response to rotation in horizontal plane (vertical axis). Semicircular canals are concerned with angular (rotatory) acceleration. Otolith organ is concerned with linear acceleration and detects acceleration in both horizontal and vertical planes. Utricle responds during horizontal acceleration and saccule responds during vertical acceleration.
Ref : Sembulingam 6th edition (Page- 924, 926)

When RBCs are delivered from the bone marrow into the circulatory system, they normally circulate an average of 120 days before being destroyed. Even though mature RBCs do not have a nucleus, mitochondria, or endoplasmic reticulum, they do have cytoplasmic enzymes that are capa- ble of metabolizing glucose and forming small amounts of adenosine triphosphate.
These enzymes also do the following:
(1) maintain pliability of the cell membrane;
(2) maintain membrane transport of ions;
(3) keep the iron of the cells' hemoglobin in the ferrous form rather than the ferric form;
(4) prevent oxidation of the proteins in the RBCs.
Even so, the metabolic systems of old RBCs become progressively less active, and the cells become more and more fragile, presumably because their life processes wear out.

Leptin produces satiety

Circulating level of Leptin is responsible for food intake regulation. Leptin decreases food intake.
Reference-Ganong/26th/P-481/Figure-26.9

Explanation- Distension of the stomach by food initiates contractions of the rectum and, frequently, a desire to defecate. The response is called the gastrocolic reflex, and may be amplified by an action of gastrin on the colon. Because of the response, defecation after meals is frequent in children. In adults, habit and cultural factors play a large role in determining when defecation occurs.
Reference-Ganong physiology/26th/P-494

Transport processes for macromolecules:
this process also called- Functional system of cell
1.Exocytosis(Neurotransmitters,Hormones,Enzymes,Proteins)
2. Endocytosis
◆ Pinocytosis(cell drinking)-proteins,vitamins
◆ Phagocytosis(cell eating)-bacteria,dead cell, tissue debris.

Secondary Polycythemia
Whenever the tissues become hypoxic because of too little oxygen in the breathed air, such as at high altitudes, or because of failure of oxy- gen delivery to the tissues, such as in cardiac failure, the blood-forming organs automatically produce large quantities of extra RBCs. This condition is called secondary polycythemia, and the RBC count commonly rises to 6 to 7 million/mm³, about 30% above normal.

A common type of secondary polycythemia, called phys iological polycythemia, occurs in those who live at altitudes of 14,000 to 17,000 feet, where the atmospheric oxygen is very low. The blood count is generally 6 to 7 million/mm³, which allows these people to perform reasonably high lev- els of continuous work, even in a rarefied atmosphere.

Digestion of proteins does not occur in mouth, since saliva does not contain any proteolytic enzymes. So, the digestion of proteins starts only in stomach.

Based on differences in the resting tone in muscles and the limbs involved, CP is classified into different groups.
The most prevalent type is spastic CP that is characterized by spasticity, hyperreflexia, clonus, and a positive Babinski sign.
These are all signs of damage to the corticospinal tract .
Dyskinetic CP is characterized by abnormal involuntary movements (chorea and athetosis) and may reflect damage to extrapyramidal motor areas. It is not uncommon to have signs of both types of CP.
The rarest type is hypotonic CP that presents with truncal and extremity hypotonia, hyperreflexia, and persistent primitive reflexes.

Neurotransmitter of Fast pain- Glutamate & Substance P for slow pain.

Function of brainstem
1. Control of respiration
2. Control of the cardiovascular system
3. Partial control of gastrointestinal function
4. Control of many stereotyped movements of the body
5. Control of equilibrium
6. Control of eye movements

Testosterone, the principal hormone of the testes, is a C19 steroid with a hydroxyl group in the 17 position . It is synthesized from cholesterol in the Leydig cells and is also formed from androstenedione secreted by the adrenal cortex. 

Pituitary apoplexy ( characterized by a sudden headache, vomiting,visual disturbances and hormonal dysfunction. The cause is most commonly
due to the abrupt growth of a pituitary adenoma or pituitary infarction.The headache in apoplexy is usually very abrupt and can be mistaken for
a subarachnoid haemorrhage, although usually not as severe. Thepresentation can be unilateral or generalized. Visual defects are most
commonly of the superior quadrant bitemporally. Visual disturbances,such as loss of vision and opthalmoplegia affecting cranial nerves III, IV
and VI, help differentiate apoplexy from other intracranial pathology.Hypopituitarism can also follow an apoplexy although this is dependent
on degree of damage and often patients present feeling very tired ornauseous. Kallman syndrome (A) is characterized by gonadotrophin
deficiency and congenital anosmia. Septo-optic dysplasia (B) is a congenitaldisorder characterized by the triad of optic nerve hypoplasia, hypopituitarism
and forebrain abnormalities. The empty sella syndrome (D) is theobservation of absent pituitary tissue within the sella turcica observed on
imaging, however pituitary function is normal due to ectopic or unusual position of pituitary tissue within the sella fossa. Sheehan syndrome (C) is
also called postpartum hypopituitarism and is most commonly a rare complication of pregnancy. Patient's present with agalactorrhoea,
amenorrhoea and hypothyroidism after pregnancy.

Explanation : All-or-none Law, Infatigability, Adaptation, Summation, Refractory period, Conductivity etc are the properties of a nerve fibre.
Ref : Sembulingam 6th edition (Page- 768, 769)

Explanations:
Hemostasis means prevention & arrest of bleeding from a cut vessel.

The kidneys synthesize glucose from amino acids and other precursors during prolonged fasting, a process referred to as gluconeogenesis. The kidneys’ capacity to add glucose to the blood during prolonged periods of fasting rivals that of the liver.

PCT has maximum capacity of reabsorption. Most of the reabsorption takes place here.