1. The Endocrine System Contributes to: By: To control
control of growth, development, reproduction, behaviour, energy metabolism, and water balance
By:
Secreting hormones
To control
Organ and tissue functions

2. Endocrine System
A system of ductless secretory organs (glands) located in various parts of the body
Include
Pineal
Anterior/posterior pituitary
Thyroid
Parathyroid
Thymus
Adrenal
Islets of Langerhans,
Ovaries
Testes
Main function
Secrete hormones directly into the blood or extracellular fluid

3. Hypothalamus Is not a gland but a region of the brain
Part of the nervous system
Very important for function of endocrine system
Produce neurohormones that stimulate or inhibit production of other hormones in the pituitary gland

4. Hormones of The Hypothalamus
Thyrotropin-releasing hormone (TRH)
Stimulates release of thyroid-stimulating hormone (TSH)
Gonadotropin-releasing hormone (GnRH)
Stimulates release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Growth hormone-releasing hormone (GHRH)
Stimulates release of growth hormone (GH)
Corticotropin-releasing hormone (CRH)
Release of adrenocorticotropic hormone (ACTH)
Somatosin
Inhibits the release of growth hormone (GH)
Dopamine
Inhibits the release of thyroid-stimulating hormone (TSH)

6. Hormones: Maintaining Homeostasis
Chemical management system for the body
Chemicals produced by cells in one part of the body that regulate the processes of cells in another part of the body
Chemical messengers
act on cells from another part of the body
Local regulators (paracrine)
act on nearby cells
Self regulators (autocrine)
cells that produce chemicals to stimulate their own cellular processes

7. Tropic vs Non-Tropic Hormones
Target endocrine glands
Nontropic Hormones
Target cells, tissues, and organs

9. Hormones
Produced and secreted by cells, tissues and organs that compose the endocrine system (glands) directly into the blood or extracellular fluid
Hormones are circulated throughout the body
Only target cells will respond to specific hormones
Hormones are broken down by enzymes in target cell, liver or kidneys where they are reused or excreted

10. Hormones Secreted in an inactive form – prohormones
Prohormones are converted by target cells or by enzymes in the blood to an active form
Angiotensinogen → angiotensin

11. Hormones Protein hormones Steroid hormones
Consist of AA (3 to 200 in length)
Usually hydrophilic (water soluble)
Diffuse well through blood
Cannot pass through lipid bilayer
Steroid hormones
Derived from cholesterol
Not water soluble
Usually encased with protein (protein carrier) to travel through blood
Pass easily through lipid bilayer

12. Hormone Mechanisms Water-Soluble Glucagon Cannot pass membrane
Bind to receptor molecules in the cell membrane
Signal is activated
Secondary messenger is activated (cAMP – cyclic adenosine monophosphate)
Change is caused inside cell
Acts in the cytosol or the nucleus
Regulate protein production, ion channels
Activation of protein kinases
Glucagon
Breakdown of glycogen into glucose

13. Controlling Blood Glucose Levels

14. Hormone Mechanisms Lipid-Soluble Aldosterone Can pass membrane (lipid)
Bind to receptors inside a cell (cytosol or nucleus)
Turn on or off an action of a specific gene
Changes amount of protein that is synthesized by cell
Aldosterone
Increase sodium absorption → increases water retention → increase blood pressure

16. Major Features of Hormone Mechanisms
Only the cells that contain surface or internal receptors for the hormones respond to the hormones
Once bound to their receptors, hormones produce a response by turning cellular processes on or off. They do this by altering the proteins that are functioning in or produced by the cell
Hormones are effective in very small concentrations because of the amplification that occurs in both the surface and internal receptor mechanisms
The response to a hormone differs among target organs and among species

17. Hormones: Negative Feedback Mechanisms
Secretion of hormones are regulated by negative feedback mechanisms
Hormones inhibit other hormones
Multiple hormones can be secreted at a time

19. The Pituitary Gland The Master Gland
Produces hormones that control most of the other glands in the endocrine system
Made up of anterior lobe and posterior lobe
Links endocrine system to nervous system via portal vein (hypothalamus)
Influenced by hypothalamus
Releasing hormones/inhibiting hormones

20. 2. portal vein
4. anterior pituitary gland
5. hypophyseal vein
6. posterior pituitary gland
8. pituitary stalk
9. capillary network
10. neurons
11. neurosecretory cells
12. hypothalamus

21. Anterior Pituitary Gland
Major hormones secreted into the bloodstream
Tropic
Growth hormone (both)
thyroid-stimulating hormone
adrenocorticotropic hormone
follicle-stimulating hormone
luteinizing hormone
Nontropic
Prolactin
Melanocyte-stimulating hormone

22. Prolactin Promote milk production in mammary glands
Suckling on nipple causes stimulus
Regulated by dopamine
Too much
Hyperprolactinaemia
Too little
Hypoprolactinaemia

23. Growth hormone Cell division, protein synthesis, bone growth
Release of growth hormone stimulates release of IGF in liver (insulin growth factor) that stimulates these functions
Conversion of glycogen to glucose, fats to fatty acids – regulates levels in blood
Stimulates cells to take up FA, AA and limits muscle cells to take up glucose

24. Growth hormone Underproduction Cause Overproduction Dwarfism
Heart disease, increased fat
Cause
Genetic, benign tumour on pituitary gland
Overproduction
Acromegaly – body tissues get larger over time
Gigantism – excessive production of growth hormone
Benign tumour on pituitary gland

25. Thyroid-stimulating hormone
Controls production of the thyroid hormones
Underproduction
Hyperthyroidism
Cause
Thyroid is producing too much thyroid hormone
Overproduction
Hypothyroidism
Thyroid if producing too much thyroid hormone

26. Adrenocorticotropic hormone
Controls production of cortisol, adrenaline, noradrenaline
Underproduction
Cushing’s syndrome
Cause
Steroid medication, tumour of pituitary gland
Overproduction
Cushing’s disease
Addison’s disease (loss of function of cortex of adrenal gland)
Adenoma (non-cancerous tumour) in the pituitary gland
Autoimmunity

27. Follicle-stimulating hormone/luteinising hormone
Puberty development/function of the gonads (testes/ovaries)
Sex steroid production
Germ cell production (sperm/eggs)
Underproduction
Incomplete development at puberty
Infertility
Overproduction
Turner syndrome (female is missing entire/parts of x chromosome)
Kallmann’s syndrome (failure to start/complete puberty)
Cause
Testicular/ovarian failure,

28. Melanocyte-stimulating hormone
Causes darkening in humans by releasing melanin in the skin and hair and eyes
Specialized cells called melanocytes release melanin
Protects from UV rays
Overproduction
Increase production of melanin
Cause
Prolonged exposure to sun or skin tanning
Underproduction
Lack of skin pigmentation
Loss of natural protection from UV rays and sun
Damage to pituitary glands

29. Posterior pituitary gland
Stores and releases 2 major hormones into the bloodstream
Antidiuretic hormone (vasopressin)
oxytocin
These hormones are produced by the hypothalamus and stored here

30. Antidiuretic Hormone (vasopressin)
Causes distal convoluted tubule to become permeable to water
Helps maintain water balance
Overproduction
Kidneys retain too much water
Underproduction
Kidneys excrete too much water

31. Oxytocin Contraction of the womb Lactation Overproduction
Not clear
Underproduction
Linked to autism

32. Thyroid gland
Located in the front of the throat and shaped like a bow tie
Secretes
Thyroxine (T₄)
calcitonin

33. Thyroxine (T₄) Prohormone (inactive) Contains 4 iodine atoms
Active form is triiodothyronine
Contains 4 iodine atoms
Regulates body’s metabolic rate, heart and digestive function, muscle control, brain development, maintenance of bones
Overproduction
Thyrotoxicosis – too much thyroxine in bloodstream recognized by goitre
Causes
Hyperthyroidism
Graves Disease
Underproduction
Hypothyroidism
Autoimmune diseases, poor iodine diet

34. Calcitonin Reduces levels of Calcium (Ca²⁺) in the blood stream
Opposes the action of parathyroid hormone
Overproduction
No apparent effect on body
Underproduction

35. Parathyroid gland
4 spherical glands (size of a pea) located on each side of the posterior surface of the thyroid gland
Secretes
Parathyroid hormone

36. Parathyroid hormone
Stimulates enzymes in kidneys to convert vitamin D into calcitrol increasing absorption of Ca²⁺ and phosphates from food
Underproduction
Muscle cramps
Osteoporosis
Overproduction
Kidney stones

37. Pineal gland Located near the centre of the brain Secretes
melatonin
Secretion of melatonin is controlled by circadian rhythm (biological processes that fluctuate on a 24 hour timetable)
Helps to synchronize biological clock (jet lag, sleep disorders)
Melatonin also produced in retina of the eye
Overproduction
Reduced core body temperature
Underproduction
No apparent effect on the body

38. Adrenal glands Consist of two regions Adrenal medulla
contains highly modified neuro-secretory neurons
2. Adrenal cortex
contains non-neural endocrine cells

39. Adrenal medulla Secretes
Epinephrine, nor-epinephrine
These chemicals can act as hormones or neurotransmitters (transmit nerve signals to brain)
Part of the “fight or flight” response

40. Epinephrine Released when body encounters stresses Increase heart rate
glycogen and fat breakdown
Major blood vessels dilate (increase blood flow)
Blood vessels in skin constrict (chills and sweating)
Increase in blood pressure
Reduces water loss
Digestive system slows
Used to counter anaphylaxis

41. Adrenal cortex
Secretes
Aldosterone, cortisol

42. Glucocorticoids
Cortisol – Helps raise blood glucose levels using three mechanisms
Stimulate synthesis of glucose from fats and proteins
Reduce glucose uptake by the body cells except in the central nervous system
Promote breakdown of fats and proteins into fatty acids and amino acids as alternative fuels

43. Mineralocorticoids Aldosterone Overproduction Causes Underproduction
Increase amount of sodium /water reabsorption in bloodstream
Increase amount of potassium removal in urine
Increase blood pressure
Overproduction
High blood pressure, low potassium, alkaline blood
Causes
Adrenal tumour
Underproduction
Addison’s disease, low blood pressure

44. Regulating blood sugar
Occurs automatically in our body
Pancreas – contain both exocrine and endocrine glands
Exocrine
secretes digestive enzymes into the small intestine
Endocrine
Islets of Langerhans - Secretes insulin (beta cells) and glucagon (alpha cells)

45. Insulin/Glucagon
Regulate the ability of most tissues in the body to metabolize fuel substances (glucose, fats, proteins)

46. Insulin Secreted by beta cells Lower blood glucose levels by
Acts on skeletal muscles, liver cells, adipose tissue (fat) to uptake glucose
In the Liver
Lowers fatty acid levels
promotes fatty acid uptake and storage in adipose tissue
Inhibits breakdown of fats into fatty acids
Lowers amino acid levels
Promotes protein synthesis
Inhibits breakdown of proteins

47. Glucagon Secreted by alpha cells Increase blood glucose levels by
Stimulating breakdown of glycogen into glucose
Stimulates breakdown of fats into fatty acids
Stimulates breakdown of proteins into amino acids
Stimulate cells to use amino acids and non-carbohydrates to synthesize glucose

48. Glucose levels throughout the day

49. Unstable levels of glucose
Hyperglycemia (above 200mg/dL of blood)
Blood glucose levels are too high
(norm mg/dL)
Symptoms
Frequent urination, sugar in the urine, vision problems, fatigue, weight loss
Hypoglycemia (below 70mg/dL of blood)
Blood glucose levels are too low
(norm mg/dL)
Nervousness, cold sweats, hunger, headaches, weakness

50. Diabetes
High glucose levels in the blood caused by problems with insulin production
Classified into 3 different types
Type 1
Type 2
Symptoms
Gestational
Frequent urination, increased thirst/appetite

51. Type 1 Also called juvenile diabetes or insulin-dependant
Beta cells do not produce any insulin
Daily administration of insulin is required usually by injection or pump

52. Type 2
Reduced insulin production or the inability of insulin to bind to its receptors properly
Developed in adulthood and is associated with obesity
90% of diabetics have this type
Controlling diet and exercise helps restore normal levels of insulin production

53. Gestational Occurs in about 2 to 10% of pregnant women
High blood glucose levels develop during pregnancy
Usually a temporary condition but does increase the risk of both mother and child developing later in life

54. Reproductive Hormones
Gonads (sex glands)
Males – testes
Females – ovaries
Sex hormones
Androgens, estrogens, progestins
Regulate development of
male and female reproductive systems, sexual characteristics, mating behaviour

55. Female Reproductive System
Pair of ovaries
Located in abdominal cavity
Produce female gametes (ova, eggs)
Produce estrogen and progesterone
FSH and LH from the pituitary gland stimulate the maturation of the follicles in the ovary and trigger ovulation

56. Estrogen Estradiol Stimulates maturation of the sex organs at puberty
Release of egg during ovulation
Development of secondary sexual characteristics (breast development, body hair, widening of pelvis)
Sex drive

57. Progestins Progesterone Secreted by the corpus luteum in the ovary
Maintains uterus for implantation of a fertilized egg
Growth and development of an embryo

58. Oogenesis Production and release of eggs (ova) by the ovaries
Releases oocytes - immature eggs that have undergone 1 meiotic division
Polar body is associated with it
Disintegrates quickly
Females produce up to 1 million
Only ~380 are ovulated before menopause

59. Ovulation
Monthly release of one or a few developing oocytes into the oviduct
Burst of LH causes follicle to rupture
Ova becomes ovum
Moves through the oviduct (fallopian tubes) via cilia that line these tubes
Fertilization occurs here in the oviduct
undergoes second meiotic division only if penetrated by sperm cell producing a zygote
If not fertilized egg will degenerate

60. Ovarian cycle Occurs from puberty to menopause
Involves release of a mature egg approx every 28 days
Coordinated with the menstrual cycle (month)
Prepares the uterus to implant the egg if fertilization occurs

61. Corpus luteum
LH causes ruptured follicle to grow into an enlarged yellowish structure
Initiates luteal phase – prepares uterus to receive an egg
If egg is fertilized:
Acts as an endocrine gland- secretes estrogens, progesterone and inhibin
Progesterone – inhibits GnRH – FSH LH
Inhibin prevents secretion of FSH
If egg is not fertilized
Corpus luteum shrinks

62. Menstrual cycle Begins at day 0
Results from the breakdown of the endometrium
Releases blood and tissue breakdown products from the uterus to the outside through the vagina
Day 4 or 5 – flow ceases and endometrium begins to grow again
Same hormones that control ovarian cycle control this cycle

63. Menopause High levels of sex hormones stops Late 40’s or early 50’s
Menstrual/Ovarian cycle stops
Side effects
Hot flashes, headaches, mood swings
Treated with HRT (hormone replacement therapy)

64. Male reproductive system
Testes
Affect the development of male secondary characteristics
Secrete androgens (testosterone)
Stimulates puberty, facial hair, vocal cords, sex drive
Spermatogenesis – production of sperm
Release of testosterone in the body is controlled by LH which is controlled by GnRH

65. Spermatogenesis Sperm development from spermatogonia
Takes about 9 to 10 weeks - spermatogonium to sperm
Testes produce about 130 million fertile sperm each day

66. Spermatogenesis Leydig cells - secrete testosterone
Sertoli cells – supply nutrients to spermatocytes and seal them off from body’s blood supply
Coiled seminiferous tubules located in epididymis store mature sperm
Vas deferens – transport sperm upon ejaculation