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CLASS 11
ENDOCRINE SYSTEM
-Endocrine system includes endocrine (ductless) glands and their secretions (hormones)
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Q) Relationship between endocrine and neural system→Endocrine gland regulates neural
activity and nervous system regulates endocrine glands
-They include
1
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Pituitary
3
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Thyroid
5
...
Thymus
7
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Pancreas (Islets of
Langerhans)
9
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HYPOTHALAMUS
Neurosecretory cells (nuclei) of hypothalamus secrete the following types of hormones:
• Releasing hormones:
Stimulate secretion of pituitary hormones
...
g
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Q)GnRH,a hypothalamic hormone,needed in reproduction,acts on→anterior pituitary gland and
stimulates secretion of LH and FSH
• Inhibiting hormones:
-Inhibit secretion of pituitary hormones
...
g
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• Oxytocin & vasopressin: These are transported axonally and stored in pituitary
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Q)Accumulation and release centre of neurohormones is→Hypothalmus
2
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- It is attached to hypothalamus bya stalk
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a
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Pars distalis (Anterior pituitary):
- It produces¨
Somatotropin (Growth hormone, GH)
-For body growth
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-Hyposecretion causes Dwarfism (stunted growth)
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-It leads to serious complications and premature death
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-It may be undetected for many years
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Q)Hormone that stimulates secretion of milk from female →prolactin
¨ Thyroid stimulating hormone (TSH): Stimulates thyroid gland to secrete thyroid hormones
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¨ Follicle stimulating hormone (FSH)
Stimulates gonadal activity
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In females, FSH stimulates growth and development of ovarian follicles
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In males, it stimulates synthesis and secretion of androgens from
testis
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Q)Gonadotrophic hormone is secreted by→anterior lobe of pituitary
Q)The immediate cause of induction of ovulation in human female is the large plasma surge
of→LH
Q) Secretion of progesterone by Corpus luteum by Corpus luteum is initiated by →LH
Q) Temporary endocrine gland in human body →corpus luteum
Pars intermedia
-In human, it is almost merged with pars distalis
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- It acts on melanocytes to regulate skin pigmentation
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Neurohypophysis
-It stores Oxytocin & Vasopressin from hypothalamus
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Oxytocin
- Contracts smooth muscles
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Q) Function of oxytocin is to help in
1)child birth
2) lactation
ii
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-Deficiency of ADH results in diminished ability of the kidney to conserve water
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- This is called Diabetes insipidus
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PINEAL GLAND
-Smallest endocrine gland
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-Secretes melatonin
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E
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sleep-wake cycle, body temperature etc
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- Influences defense capability
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THYROID GLAND
- Largest endocrine gland
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-The lobes are interconnected with isthmus (a connective tissue)
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-Follicular cells secrete the following hormones:
1)Thyroxin (tetraiodothyronine, T4) & Triiodothyronine

(T3):
Their functions are
o Regulation of basal metabolic rate (BMR)
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o Support RBC formation
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o Maintain water and electrolyte balance
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-It regulates(lowers) blood calcium levels (Hypocalcaemic hormone)
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Q)Calcitonin is a thyroid hormone which →lowers calcium level in blood

#Hypothyroidism (Goiter):
- Enlargement of thyroid gland due to deficiency of iodine
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- Hypothyroidism during pregnancy affects the baby causing
stunted growth (cretinism), mental retardation, low intelligence quotient, abnormal skin,
deaf-mutism etc
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This is result of →deficiency of iodine in diet
Q)Toxic agents present in food which interfere with thyroxine synthesis lead to development
of→ simple goitre
Q)A health disorder that results from the deficiency of thyroxine in adults and characterised by a
low metabolic rate,increase body weight and tendency to retain water in tissues is→myxoedema
#Hyperthyroidism
- Abnormal increase of thyroid hormones resulting in adverse effects on the physiological
activities
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Q)Acromegaly is caused by→excess of thyroid hormone
- Exophthalmic goiter (Grave’s disease):
- It is a form of Hyperthyroidism
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Q)Graves disease is caused due to→hypersecretion of thyroid gland
5
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-They secrete Parathyroid hormone (PTH) – a peptide hormone
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• Stimulates the bone resorption (demineralization)
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• Along with TCT, it helps in calcium balance in the body
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THYMUS GLAND
It is located between lungs behind sternum on the ventral side of aorta
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Functions of thymosins:
• Differentiation of T-lymphocytes
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• Promote antibody production for humoral immunity
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-So, production of thymosins decreases
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7
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A)ADRENAL CORTEX
- It has 3 layers:
inner zona reticularis,
middle zona fasciculata &
outer zona glomerulosa
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- Stimulate gluconeogenesis, lipolysis and proteolysis
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- Maintain cardiovascular system and kidney functions
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- Produces anti-inflammatory reactions and suppress immune response
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-Aldosterone stimulates reabsorption of Na+ & water from renal tubules and excretion of K+ and
PO- ions
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-Deficiency of corticoid hormones affects carbohydrate metabolism
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-This condition is called Addison’s disease
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- They are rapidly secreted in response to stress emergency situations so called emergency
hormones (hormones of
Fight or Flight)
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-Stimulate glycogenolysis to increase
glucose in blood
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Q) Adrenaline directly affects on→SA node
Q)Feeling of tremors of an earthquake a scared resident of 7th floor of a building starts climbing
down rapidly
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PANCREAS (ISLETS OF LANGERHANS)
- A composite (heterocrine) gland i
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exocrine + endocrine
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- There are about 1-2 million Islets (1-2% of pancreatic tissue)
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-They maintain Glucose homeostasis in blood
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-It
o Acts on hepatocytes and stimulates glycogenolysis resulting in an increased blood sugar
(hyperglycemia)
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o Reduces the cellular glucose uptake and utilization
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It
o Acts on hepatocytes and adipocytes to enhance cellular glucose uptake and utilization
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-Thus, blood glucose level decreases (hypoglycemia)
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-Prolonged hyperglycemia leads to Diabetes mellitus (loss of glucose through urine and
formation of harmful compounds
like ketone bodies)
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Q) Insulin is a→hormone
Q)Hormone having anti insulin effect →glucagon and cortisol
Q) Diabetes is due to→hormone deficiency
Q)A peptide hormone which act on hepatocytes,adipocytes and enhances cellular glucose
uptake and utilisation →insulin
Q)Insulin acts on →adipocytes and hepatocytes but not pancreatic cells
Q)Insulin is associated with→hypoglycemia
9
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- A pair of testis is present in the scrotal sac
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-Leydig (interstitial) cells in the inter-tubular spaces produce hormones called androgens (mainly
testosterone)
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• Spermatogenesis (sperm production)
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• Help in anabolism of protein and carbohydrate
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OVARY (FEMALE GONAD)
- It is the female primary sex organ
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- It produces one ovum during each menstrual cycle
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- Ovarian follicles produce Estrogen (a steroid hormone)
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- It secretes progesterone (a steroid
hormone)
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• Development of ovarian follicles & mammary glands
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g
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Q) Hormone that control menstrual cycle in human beings →FSH,LH and estrogen
Functions of Progesterone:
• It supports pregnancy
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#SPECIAL ENDOCRINE ORGANS
1) Atrial wall of heart
Produce a peptide hormone called Atrial natriuretic factor (ANF)
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2)JGA of kidney
-Produces Erythropoietin (peptide
hormone)
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3)Gastro-intestinal tract
Produce peptide hormones
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g
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B) Secretin
-Stimulates exocrine pancreas to secrete
water and bicarbonate ions
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D)Gastric inhibitory peptide (GIP):
- Inhibits gastric secretion
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-These help for the normal growth of tissues and their repairing or regeneration
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-A hormone binds to its specific receptor to form hormonereceptor complex
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-Hormone receptors are 2 types:
1)Membrane-bound receptors:
-Some hormones (e
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protein hormone, FSH) interact with membrane-bound
receptors (do not enter the target cell)
- It generates second messengers (e
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cyclic AMP, IP3, Ca2+)
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2) Intracellular receptors
(mostly nuclear receptors):
-Some hormones (e
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steroid hormones, iodothyronines) interact with intracellular receptors
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-Cumulative biochemical actions result in physiological and developmental effects

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