Previous year paper of Human physiology, for BDS first year students. if there is anything wrong kindly suggest me thank you.......

1. GENERAL HUMAN PHYSIOLOGY 2018
SHAHID EQUABAL Page 1
PART- 1
1. Describe the function of the saliva. Describe the regulation of salivary secretion.
2+4=6
Function: saliva is very essential. Since it has many functions,
i. Preparation of food for swallowing.
ii. Appreciation of taste.
iii. Digestive function.
iv. Cleansing function and protective function.
v. Role in speech.
vi. Excretory function.
vii. Regulation ob body temperature.
viii. Regulation of water balance.
Regulation of salivary secretion:
 On the average about 1-2 liters of saliva are secreted /day.
 It ranges from a continuous spontaneous basal flow rate of 0.5 ml/min to a
maximum flow rate of about 5 ml/min in response to a potent stimulus.
 Salivary secretion is enhanced by two different types of salivary reflexes:
 Simple or unconditioned reflex.
 Acquired or conditioned reflex.
 SIMPLE or UNCONDITIONED REFLEX:
 It occurs when chemoreceptor’s and pressure receptors within the oral cavity
respond to the presence of food.
 On activation these receptors initiate impulses in afferent nerve fibers that carry
the information to the salivary center located in the medulla of the brain.
 Acquired or conditioned reflex:
 In this case salivation occurs without oral stimulation.
 Just thinking about, smelling, or hearing the preparation of pleasant food
initiate salivation through this reflex.
 Also called mouth watering.
 Sympathetic and parasympathetic responses in the salivary glands both
these increase salivary secretions.
 PARASYMPATHETIC:
 It exerts the dominant role in salivary secretion, and produces a prompt and
abundant flow of watery saliva that is rich in enzymes.

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 SYMPATHETIC:
 It produces a much smaller volume of thick saliva that is rich in mucus.
 That is the mouth feels drier than usual in stressful conditions.
 Salivary secretions is the only digestive secretion that is totally under the neural
control
2. Write briefly on: 3×4=12
a. Role of platelets in hemostasis.
b. Myasthenia gravis.
c. P-R interval.
d. Transport of carbon dioxide in blood.
a. Role of platelets in hemostasis:
Whenever a vessel is ruptured, hemostasis is achieved by several mechanisms:
(1) Vascular constriction
(2) Formation of a platelet plug
(3) Formation of a blood clot as a result of blood coagulation
(4) Eventual growth of fibrous tissue into the blood clot to close the hole in the vessel
permanently.
b. Myasthenia gravis:
Myasthenia gravis is an autoimmune disorder affecting the myoneural junction, is
characterized by varying degrees of weakness of the voluntary muscles.
 Causes:
In MG, the receptors at the muscle surface are destroyed or deformed by antibodies
that prevent a normal muscular reaction from occurring.
 Risk factor:
Risk factors for myasthenia gravis include:
• Female gender and age under 40 years
• Male gender and age over 60 years
• Other autoimmune disorders
SIGN AND SYMPTOMS:
• Diplopia and ptosis:
Weakness of the muscles of the face and the throat, and generalized weakness
c. P-R interval:
 The PR interval is the time from the onset of the P wave to the start of
the QRS complex.
 It reflects conduction through the AV node.
 The normal PR interval is between 120 – 200 ms (0.12-0.20s) in duration.
 If the PR interval is > 200 ms, first degree heart block is said to be present.
 PR interval < 120 ms suggests pre-excitation or AV nodal rhythm.

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d. Transport of carbon dioxide in blood:
 In Dissolved form
 In Bicarbonate form
 In Carbamino compound form
 In Dissolved form:
 Venous blood with PCO2 45 mm Hg contains 2.7ml/100ml CO2 in dissolved form.
 Arterial blood with PCO2 40 mm Hg contains 2.4ml/100ml CO2 in dissolved form.
 In Bicarbonate form:
 Chloride shift or Hamburger phenomenon.
 In Carbamino compound form:
 In plasma – CO2 combines with amino group of plasma proteins – forms
Carbamino proteins.
 In RBC – combines with amino group of Hb – forms Carbamino Hemoglobin.
 This combination of CO2 with Hb – Reversible.
 Carbon dioxide dissociation curve:

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Part-2
3. Describe thalamus and enumerate its function: 1+4=5
The thalamus is a small structure within the brain located just above the brain stem
between the cerebral cortex and the midbrain and has extensive nerve connections to
both.
Function:
 Relay of sensation (Except olfactory system)
 Spatial sense
 Regulation of consciousness
 Regulation of sleep and alertness
 Main largest product of embryonic diencephalon
 Great sensory gateway to cerebral cortex
 Damage to thalamus can lead to permanent coma
 Sensory integration relay station for all sensory
4. Write briefly: 3×4=12
a) Menstrual cycle.
b) Function of thyroid hormone.
c) Juxta Glomerular apparatus.
d) Smell sensation.
a) Menstrual cycle:
 Menstrual cycle begins at puberty. The cyclical changes in the endometrium of
uterus, in response to ovarian hormones constitute the menstrual cycle.
 It is divided into the following 3 phases:
1. Proliferative phase
2. Secretory phase
3. Menstrual phase.
1. Proliferative Phase: This is also known as follicular Phase.
This phase follows the last menstrual phase.
It has the following characteristic features:
• There is generalized active proliferation of endometrium.
• Endometrium grows from 1 to 3 mm.
2. Secretory phase: This is also known as progestational phase. It is characterized by the
following features:
 There is further growth of endometrium.
 It grows up to 5 to 7 mm in thickness
3. Menstrual phase:
 Menstrual phase follows secretory phase and lasts for 3 to 5 days.
 The average amount of blood loss during menstrual phase is about 50 to 60 ml.

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b) Function of thyroid hormone.
 Thyroid is an endocrine gland situated at the root of the neck on either side of
the trachea.
 Thyroid gland secretes three hormones:
1. Tetraiodothyronine or T4 (thyroxin)
2. Tri-iodothyronine or T3
3. Calcitonin
 Thyroid hormones have two major effects on the body:
I. To increase basal metabolic rate
II. To stimulate growth in children.
1. ACTION ON BASAL METABOLIC RATE (BMR):
 Thyroxin increases the metabolic activities in most of the body tissues, except
brain, retina, spleen, testes and lungs.
 It increases BMR by increasing the oxygen consumption of the tissues.
 In hyperthyroidism, BMR increases by about 60% to 100% above the normal level
and in hypothyroidism it falls by 20% to 40% below the normal level.
2. ACTION ON PROTEIN METABOLISM :
 Thyroid hormone increases the synthesis of proteins in the cells.
 The protein synthesis is accelerated by the following ways:
i. By Increasing the Translation of RNA
ii. By Increasing the Transcription of DNA to RNA
iii. By Increasing the Activity of Mitochondria
iv. By Increasing the Activity of Cellular Enzymes
c) Juxta Glomerular apparatus:
 Juxtaglomerular apparatus is a specialized organ situated near the glomerulus of
each nephrons
 Juxtaglomerular apparatus is formed by three different structures:
i. Macula densa
ii. Extra glomerular mesangial cells
iii. Juxtaglomerular cells.
Function:
 Primary function of Juxtaglomerular apparatus is the secretion of hormones.
 It also regulates the Glomerular blood flow and glomerular filtration rate.
 Juxtaglomerular apparatus secretes two hormones:
i. Renin
ii. Prostaglandin

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Secretion of renin is stimulated by four factors:
i. Fall in arterial blood pressure
ii. Reduction in the ECF volume
iii. Increased sympathetic activity
iv. Decreased load of sodium and chloride in macula densa
Prostaglandin is also secreted by interstitial cells of medulla called type I medullary
interstitial cells
d) Smell sensation:
 Olfactory receptors are situated in olfactory mucus membrane, which is the
modified mucus membrane that lines upper part of nostril.
 Mucus secreted by Bowman glands continuously lines the olfactory mucosa.
 The olfactory sense is highly developed in the rabbit and dog, which are called
macrosmatic; but is much less in man, apes, monkeys (primates), which are called
microsmatic.
 Localization of smell i.e. direction from which a smell comes depend on the
difference of time between the arrivals of odoriferous molecules in the two
nostrils.