BIOLOGICAL CONTROL SYSTEM

1. ENDOCRINE CONTROL
SYSTEM
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VADLAMUDI NAMRATHA

2. Contents
 Introduction
 The major areas of control and integration
 Anatomy of endocrine system
 Physiology of endocrine system
 Homeostatic feedback mechanism
 References
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3. Introduction
 The endocrine system helps
regulate and maintain various body functions
by synthesizing (making) Releasing hormones, chemical
messengers.
The factors involved are:
Signal
 Generation
 Propagation
 Recognition
 Transduction
 Response
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4. The major areas of control and
integration are:
 responses to stress and injury, growth
 development, absorption of nutrients, energy
metabolism, water and electrolyte balance.
 reproduction, birth, and lactation.
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5. Anatomy of endocrine
system
 The endocrine system refers to the collection
of glands of an organism that secrete hormones directly
into the circulatory system to be carried toward a distant
target organ.
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6. Glands
 Glands are of two types.
 Endocrine glands do not have a duct system and are
called ductless glands. These glands release hormones
directly into the blood or lymph.
 Exocrine glands such as the sudoriferous (sweat)
glands contain ducts.
* Ducts are tubes leading from a gland to its target
organ.
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7. Endocrine glands
 Pituitary
 Thyroid
 Parathyroid
 Adrenal
 Pineal
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8. Endocrine glands(contd..)Several organs and tissues are not exclusively classified as endocrine
glands but contain cells that secrete hormones.
 Hypothalamus
 Thymus
 Pancreas
 Ovaries
 Testes
 Kidneys
 Stomach
 Liver
 Small intestine
 Skin
 Heart
 Adipose tissue
 Placenta
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9. Pituitary gland or hypophysis
 Master of all glands.
 Pituitary gland itself has a master- the hypothalamus.
 The hypothalamus is the major integrating link between the
nervous and endocrine system.
 Cells in the hypothalamus synthesize at least 9 different
hormones , the pituitary gland secretes seven.
 Together ,these hormones play important roles in the
regulation of virtually all aspects of growth , development ,
metabolism and homeostasis. 9

10. Pituitary gland(contd..)
The pituitary gland is pea shaped structure that is located
in the hypophyseal fossa and is divided into 2 main
portions
 Anterior pituitary (glandular portion )
 Posterior pituitary ( nervous portion)
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11. Anterior pituitary
 Adenophysis (adeno=gland,-hypophysis=undergrowth)
 Release of anterior pituitary hormones is stimulated by
releasing hormones and suppressed by inhibiting hormones
from the hypothalamus.
5 types of anterior pituitary cells that secrete seven hormones
they are:
 Somatotrophs
 Thyrotrophs
 Gonadotrophs
 Lactotrophs
 corticotrophs
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12. Hormones of the anterior
pituitary
 Somatotrophs - Human growth hormone( hGH )
Stimulates several tissues to secrete insulin like growth factors ,
hormones that stimulate general body growth and regulate aspects
of metabolism.
 Gonadotrophs- secrete 2 gonadotropins
Follicle stimulating hormone (FSH)
Luteinizing hormone(LH)
They act on gonads.
They stimulate secretion of estrogens and progesterone .
They stimulate sperm production and secretion of testosterone in
the testes.
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13. Hormones of the anterior
pituitary(contd..)
 Lactotrophs – secrete prolactin (PRL)
Which initiates milk production in the mammary glands.
 Corticotrophs – secrete adrenocorticotropic hormone
(ACTH) a.k.a corticotropin.
Which stimulates the adrenal cortex to secrete
glucocorticoids such as cortisol.
 Thyrotrophs – secrete thyroid stimulating hormone also
known as thyrotropin .TSH controls the secretions and
other activities of the thyroid gland.
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14. Posterior pituitary
 Also known as Neurohypophysis
 It doesn't synthesize hormones it stores and releases
them.
 Neurosecretory cells of hypothalamus secrete two
hormones :
Oxytocin(OT)
Antidiuretic hormone (ADH) or vasopressin
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15. Posterior pituitary hormones
 Oxytocin: neurosecretory cells of hypothalamus secrete OT
in response to uterine distention.
It stimulates contraction of smooth muscle cells of uterus
during childbirth.
 Vasopressin : ADH is secreted in response to elevated blood
osmotic pressure,dehydration,loss of blood volume, pain or
stress.
It conserves body water by decreasing urine volume;
decreases water loss through perspiration; raises blood
pressure by constricting arterioles.
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16. Thyroid gland
 The butterfly shaped thyroid gland is located just inferior to
larynx(voice box).
 Microscopic spherical sacs called thyroid follicles make up
most of the thyroid gland.
 The wall of each follicle consists primarily of cells called
follicular cells .
 A few cells called parafollicular cells or C cells lie
between follicles.
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17. Thyroid gland hormones
 T3 (triiodothyronine) T4 ( thyroxine) from follicular cells
which stimulates release of TSH ( thyroid stimulating hormone)
in response to low thyroid hormone levels ; low metabolic rate
,cold , pregnancy.
High iodine level suppresses T3 / T4 secretion
 Calcitonin(CT) - from parafollicular cells
 High blood Ca+2 levels stimulate secretion
 Low blood Ca+2 levels inhibit secretion
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18. Parathyroid glands&PTH
 The parathyroid glands are embedded in the posterior
surfaces of the lateral lobes of the thyroid gland.
 They consist of chief cells and oxyphil cells.
 The chief cells produce parathyroid hormone (PTH) also
called parathormone.
 PTH regulates the homeostasis of Calcium ,Magnesium
,&Phosphate ions by increasing blood calcium and
magnesium levels and decreasing blood phosphate levels.
 PTH secretion is controlled by the level of calcium in the
blood. 18

19. Adrenal glands
 The adrenal glands are located superior to the kidneys.
 They consist of an outer adrenal cortex and inner adrenal
medulla.
 Adrenal cortex is divided into 3 zones : zona glomerulosa ,zona
fasciculata , zona reticularis.
 Adrenal medulla – chromaffin cells
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20. Adrenal cortex hormones
 Mineralocorticoids (aldosterone) from zonaglomerulosa
cells
Increase sodium and water reabsorption and decrease
pottasium reabsorption.
 Glucocorticoids(cortisol) from zona fasciculata cells
Promote protein breakdown,gluconeogenesis,and lypolysis.
 Androgens (dehydroepiandrosterone DHEA) from zone
reticularis
Stimulate growth of axillary and pubic hair
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21. Adrenal medulla hormones
 Epinephrine and norepinephrine from chromaffin
cells
 Released during stress and produce effects similar to
sympathetic responses
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22. Pineal gland
 Attached to the roof of the third ventricle of the brain at
the midline.
 The gland consists of masses of neuroglia and secretory
cells.to set the body’s biological clock.
 Pineal gland secretes melatonin an amine hormone which
appears to contribute
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23. Physiology of endocrine system
 Endocrine System & Nervous System
 Hormone Property
 Hormonal Regulation
 Classes of Hormones
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24. Neuro endocrine system
 The endocrine system and the nervous system are so closely
associated that they are collectively called the neuroendocrine
system.
 Neural control centers in the brain control endocrine glands.
 The main neural control center is the hypothalamus, also
known as the "master switchboard.“
 Suspended from the hypothalamus by a thin stalk is the
pituitary gland.
 The hypothalamus sends messages to the pituitary gland; the
pituitary gland, in turn, releases hormones that regulate body
functions. 24

25. Hormone property
Specificity :
 As hormones travel through the body, they pass through cells
or along the plasma membranes of cells until they encounter
a receptor for that particular hormone.
 Hormones can only affect target cells that have the
appropriate receptors.
 This property of hormones is known as specificity. Hormone
specificity explains how each hormone can have specific
effects in widespread parts of the body.
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26. Hormonal Regulation
 The levels of hormones in the body can be regulated by
several factors.
 The nervous system can control hormone levels through
the action of the hypothalamus and its releasing and
inhibiting hormones.
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27. Classes of hormones
 Hormones are classified into 2 categories depending on
their chemical make-up and solubility:
 water-soluble and lipid-soluble hormones.
 Each of these classes of hormones has specific mechanisms
for their function that dictate how they affect their target
cells.
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28. Water soluble hormones
 Water-soluble hormones include the peptide and amino-acid
hormones such as insulin , and oxytocin.
 As their name indicates, these hormones are soluble in water.
 Water-soluble hormones are unable to pass through the
phospholipid bilayer of the plasma membrane and are therefore
dependent upon receptor molecules on the surface of cells.
 When a water-soluble hormone binds to a receptor molecule on
the surface of a cell, it triggers a reaction inside of the cell. This
reaction may change a factor inside of the cell such as the
permeability of the membrane or the activation of another
molecule. 28

29. Lipid soluble hormones
 Lipid-soluble hormones include the steroid hormones such as
testosterone, estrogens, glucocorticoids, and mineralocorticoids.
 Because they are soluble in lipids, these hormones are able to pass
directly through the phospholipid bilayer of the plasma membrane
and bind directly to receptors inside the cell nucleus.
 Lipid-soluble hormones are able to directly control the function of
a cell from these receptors, often triggering the transcription of
particular genes in the DNA to produce "messenger RNAs
(mRNAs)" that are used to make proteins that affect the cell’s
growth and function.
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30. Homeostatic Feedback
Mechanisms
 Many endocrine glands are linked to neural control
centers by homeostatic feedback mechanisms.
 The two types of feedback mechanisms are
 negative feedback and
 positive feedback.
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31. Negative Feedback
 Negative feedback decreases the deviation from an
ideal normal value
 It is important in maintaining homeostasis.
 Most endocrine glands are under the control of
negative feedback mechanisms.
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32. Negative Feedback e.g.
 An example of negative feedback is the regulation of the blood
calcium level.
 The parathyroid glands secrete parathyroid hormone, which
regulates the blood calcium amount.
 If calcium decreases, the parathyroid glands sense the decrease
and secrete more parathyroid hormone.
 Conversely, if blood calcium increases too much, the parathyroid
glands reduce parathyroid hormone production.
 Both responses are examples of negative feedback because in
both cases the effects are negative (opposite) to the stimulus. 32

33. Positive Feedback
 Positive feedback mechanisms control self-perpetuating
events that can be out of control and do not require
continuous adjustment.
 In positive feedback mechanisms, the original stimulus is
promoted rather than negated.
 Positive feedback increases the deviation from an ideal
normal value.
 Unlike negative feedback that maintains hormone levels
within narrow ranges, positive feedback is rarely used to
maintain homeostatic functions.
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34. Positive Feedback e.g.
 An example of positive feedback can be found in childbirth
 The hormone oxytocin stimulates and enhances labor contractions.
 As the baby moves toward the vagina (birth canal), pressure
receptors within the cervix (muscular outlet of uterus) send
messages to the brain to produce oxytocin. Oxytocin travels to the
uterus through the bloodstream, stimulating the muscles in the
uterine wall to contract stronger (increase of ideal normal value).
 The contractions intensify and increase until the baby is outside the
birth canal.
 When the stimulus to the pressure receptors ends, oxytocin
production stops and labor contractions cease. 34

35. References
http://hpp.adam.com/pages/guide/reftext/html/endo_
sys_fin.html
http://www.innerbody.com/image/endoov.html
Principles of anatomy & physiology Gerard J Tortora
Bryan Derrickson
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