1. Hormones & Endocrine System
Chapter 40
Hormones & Endocrine System

2. The Human Endocrine System

3. Regulation Why are hormones needed?
chemical messages from one body part to another
communication needed to coordinate whole body
homeostasis & regulation
metabolism
growth
development
maturation
reproduction
growth hormones

4. Regulation & Communication
Animals rely on 2 systems for regulation
endocrine system
ductless gland which secrete chemical signals directly into blood
chemical travels to target tissue
slow, long-lasting response
nervous system
system of neurons, central nerve system
transmits “electrical” signal to target tissue
fast, short-lasting response
Hormones coordinate slower but longer–acting responses to stimuli such as stress, dehydration, and low blood glucose levels. Hormones also regulate long–term developmental processes by informing different parts of the body how fast to grow or when to develop the characteristics that distinguish male from female or juvenile from adult. Hormone–secreting organs, called endocrine glands, are referred to as ductless glands because they secrete their chemical messengers directly into extracellular fluid. From there, the chemicals diffuse into the circulation.

5. Target cells have receptors for the hormone that fit like a lock & key
Target Cell Concept
Target cells have receptors for the hormone that fit like a lock & key

6. Regulation by chemical messengers
Neurotransmitters released by neurons
Hormones release by endocrine glands
Endocrine gland
Axon
Neurotransmitter
Hormone
carried
by blood
Receptor
proteins
Target cell

7. Classes of Hormones Protein-based hormones Lipid-based hormones
polypeptides
small proteins: insulin, ADH
glycoproteins
large proteins + carbohydrate: FSH, LH
amines
modified amino acids: epinephrine, melatonin
Lipid-based hormones
steroids
modified cholesterol: sex hormones, aldosterone

8. How do hormones act on target cells
Lipid-based hormones
lipid-soluble
diffuse across membrane & enter cells
bind to receptor proteins in cytoplasm & then this hormone-receptor complex moves into nucleus
bind to receptor proteins in nucleus
bind to DNA as transcription factors
activates transcription of enzymes & other proteins that carry out response

9. Action of steroid (lipid) hormones
Cytoplasm
Blood plasma
Steroid
hormone S S 1
Protein
carrier S 2
Plasma membrane 1
Steroid hormone (S) passes through plasma membrane. 2
Inside target cell, the steroid hormone binds to a specific receptor protein in the cytoplasm or nucleus. 4 S 3
Hormone-receptor complex enters nucleus & binds to DNA, causing gene transcription 3
DNA
mRNA 5
Protein 4
Protein synthesis is induced.
Nucleus 5
Protein is produced.

10. How do hormones act on target cells
Protein-based hormones
hydrophilic & not lipid soluble
can’t diffuse across membrane
trigger secondary (2°) messenger pathway
transmit “signal” across membrane
“signal transduction”
usually activates a series of 2° messengers (often cAMP)
multi-step “cascade”
activate cellular response
enzyme action, uptake or secretion of molecules, etc.
Signal molecule
Cell surface receptor
enzyme
cAMP
G protein
ATP
Target protein
Nucleus
Cytoplasm

11. Action of protein hormones1
Protein
hormone
activates enzyme
G protein
Receptor
protein
cAMP 3 2
ATP
activates
enzyme
protein
messenger cascade
GTP
activates
enzyme 4
Cytoplasm
Produces an action

12. Action of epinephrine (adrenalin)
Liver cell 1
Epinephrine
activates adenylyl cyclase
adrenal gland
G protein
Receptor
protein
cAMP 3 2
ATP
activates
protein kinase-A
GTP
activates
phosphorylase 4
released to blood
Cytoplasm
Glycogen
Glucose

13. Benefits of a 2° messenger system1
Receptor protein
Activated adenylyl cyclase
Signal molecule
Not yet
activated 2
Amplification 4
Amplification
cAMP 3 5
GTP
G protein
Protein kinase 6
Amplification
Amplification!
Enzyme 7
Amplification
Enzymatic product

14. Endocrine system Ductless glands release hormones into blood
Duct glands = exocrine
(tears, salivary)

15. Major vertebrate hormones (1)

16. Major vertebrate hormones (2)

17. Endocrine & Nervous system links
Hypothalamus = “master control center”
nervous system
receives information from nerves around body about internal conditions
regulates release of hormones from pituitary
Pituitary gland = “master gland”
endocrine system
secretes broad range of hormones regulating other glands

18. Thyroid gland
Hypothalamus
Anterior
pituitary
Gonadotropic
hormones:
Follicle-
stimulating
hormone (FSH)
& luteinizing
hormone (LH)
Mammary
glands
in mammals
Muscles
of uterus
Kidney
tubules
Posterior
Thyroid-stimulating
Hormone
(TSH)
Antidiuretic
hormone
(ADH)
Adrenal
cortex
Bone
and muscle
Testis
Ovary
Melanocyte
in amphibian
Adrenocorticotropic
hormone (ACTH)
Melanocyte-stimulating hormone
(MSH)
Oxytocin
Prolactin (PRL)
Growth hormone (GH)

19. Pituitary Gland - has 2 portions:
Posterior Pituitary
Neurons in hypothalamus called neurosecretory cells produce 2 hormones that pass down axons to posterior pituitary
ADH (antidiuretic hormone) - causes water to be reabsorbed in kidney collecting ducts; affects blood volume & blood pressure
ADH release is controlled by negative feedback
Oxytocin - causes uterine contractions & milk letdown when a baby is nursing
Oxytocin release is controlled by positive feedback – –

20. Hypothalamus and the Pituitary

21. Regulating blood osmolarity
Dehydration
Lowers
blood
volume
& pressure
If amount of dissolved material in the blood is too high, the body needs to dilute the blood
Osmotic concentration
of blood increases
Osmoreceptors
Negative
feedback
Negative
feedback
ADH synthesized in hypothalamus
ADH
ADH released from posterior pituitary into blood
Increased
water
retention
Increased
vasoconstriction
leading to higher
blood pressure
Reduced
urine volume

22. Connected to hypothalamus via a portal system of blood vessels
Anterior Pituitary
Connected to hypothalamus via a portal system of blood vessels
Hypothalamus controls anterior pituitary by producing:
1. hypothalamic-releasing hormones
TSH-releasing hormone (TRH)
LH-releasing hormone (LHRH)
2. hypothalamic-inhibiting hormones
Prolactin release-inhibiting hormone – –

23. Hypothalamus and the Pituitary

24. Anterior Pituitary 3 Anterior Pituitary hormones affect other glands:
Thyroid-Stimulating Hormone (TSH)
Stimulates thyroid gland to release its hormones
Adrenocorticotropic Hormone (ACTH)
Stimulates adrenal cortex to produce hormones
Gonadotropic Hormones:
1. FSH - follicle-stimulating hormone
Stimulates ovaries & testes to produce gametes
2. LH - luteinizing hormone from testes & ovaries
Stimulates ovaries & testes to produce sex hormones – –

25. Anterior Pituitary (cont’d)
3 Anterior Pituitary hormones do NOT affect other glands:
Prolactin (PRL)
Stimulates mammary glands to produce milk after childbirth
Growth Hormone (GH) or somatotropic hormone
Causes skeletal & muscle growth
Melanocyte-Stimulating Hormone (MSH)
Causes skin-color changes in fish, amphibians & reptiles – –

26. Effect of Growth Hormone

27. Acromegaly
Overproduction of GH in adults. Only bones of face, fingers & toes can enlarge

28. Thyroid Gland
Largest endocrine gland. Located in neck just below the larynx.
Composed of large number of follicles, each of which is filled with thyroid hormones:
Triiodothyronine (T3)
Contains 3 iodine atoms
Thyroxine (T4)
Contains 4 iodine atoms
Thyroid hormones increase metabolic rate. – –

29. Regulating metabolism
Hypothalamus
TRH = TSH-releasing hormone
Anterior Pituitary
TSH = thyroid stimulating hormone
Thyroid
produces thyroxine hormones
metabolism & development
bone growth
mental development
Increase metabolic use of energy
blood pressure & heart rate
muscle tone
digestion
reproduction
The thyroid gland produces two very similar hormones derived from the amino acid tyrosine: triiodothyronine (T3), which contains three iodine atoms, and tetraiodothyronine, or thyroxine (T4), which contains four iodine atoms. In mammals, the thyroid secretes mainly T4, but target cells convert most of it to T3 by removing one iodine atom. Although both hormones are bound by the same receptor protein located in the cell nucleus, the receptor has greater affinity for T3 than for T4. Thus, it is mostly T3 that brings about responses in target cells.
tyrosine
iodine
thyroxine

30. Goiter
Iodine deficiency causes thyroid to enlarge as it tries to produce thyroxine. Due to stimulation by anterior pituitary.

31. Hypothyroidism
If thyroid fails to develop properly in children & is not treated with hormones, cretinism develops.
Individuals are short & stocky
Mental retardation will occur unless treatment is started within two months of birth
Hypothyroidism in adults produces myxedema
Individuals gain weight, lose hair, are lethargic, have slow pulse rate, low body temperature
Administration of hormones restores normal functions. – –

32. Cretinism

33. Hyperthyroidism
If thyroid produces too much thyroid hormone, Graves disease results.
Exophthalmic goiter forms - protruding eyes
Patients will also be hyperactive, nervous & irritable, and suffer from insomnia – –

34. Thyroid Gland (cont’d)
Also secretes a hormone that regulates blood calcium levels:
Calcitonin
Secreted by thyroid when blood calcium levels rise
Effects of Calcitonin:
Causes deposition of calcium in the bones
When blood calcium returns to normal, release of calcitonin by thyroid is inhibited – –

35. Parathyroid Gland
Secretes parathyroid hormone (PTH) which has the following effects:
Increases blood calcium levels
Causes blood phosphate (HPO42-) levels to decrease
Low blood calcium levels stimulate release of PTH
PTH promotes the release of calcium from bones – –

36. Regulating blood calcium levels via PTH from parathyroid gland
Low blood Ca++
Parathyroids –
Parathyroid
hormone (PTH)
Negative
feedback
PTH activates Vitamin D into hormone that enables calcium absorption from intestines. This is why Vitamin D deficiency causes rickets = poor bone formation
Increased absorption
of Ca++ from intestine due to PTH activation of Vitamin D
Reabsorption of Ca++ &
excretion of PO4
Osteoclasts
dissolve CaPO4
crystals in bone, releasing Ca++
Increased blood Ca++

37. Regulating blood calcium levels via calcitonin from thyroid gland
High blood Ca++
Parathyroids –
Calcitonin
Negative
feedback
PTH activates Vitamin D into hormone that enables calcium absorption from intestines. This is why Vitamin D deficiency causes rickets = poor bone formation
Decreased absorption
of Ca++ from intestine
Release of Ca++
Reduce activity of osteoclasts, thus storing Ca++ in bones
Decreased blood Ca++

38. Regulation of Blood Calcium Level

39. Adrenal Glands Paired adrenal glands sit atop each kidney.
Each gland consists of two portions
Inner adrenal medulla
Produces:
Epinephrine & norepinephrine
Short-term response to stress (fight or flight)
Outer adrenal cortex
Mineralocorticoids & glucocorticoids
Long-term response to stress – –

40. Adrenal Glands (cont’d)
Hypothalamus exerts control over both portions of adrenal gland.
1. Nerve impulses from hypothalamus stimulate adrenal medulla to secrete its hormones.
2. ACTH-releasing hormone from hypo controls anterior pituitary’s secretion of ACTH, which in turn stimulates the adrenal cortex to secrete glucocorticoids
Stress prompts hypothalamus to stimulate the adrenal glands –

41. Adrenal Glands

42. Adrenal Medulla
Epinephrine & norepinephrine produce short-term responses to stress:
Accelerate breakdown of glucose to form ATP
Trigger breakdown of glycogen to produce glucose
Increase cardiac rate & force
Raises blood pressure
Raises breathing rate & O2 usage
Inhibits peristalsis – –

43. Adrenal Cortex
Two types of hormones provide long-term response to stress:
Mineralocorticoids
Regulate salt & water balance.
Aldosterone is most important one.
•Promote absorption of Na+ & excretion of K+.
•Increase blood volume & blood pressure – –

44. Adrenal Glands

45. Adrenal Cortex (cont’d)
Glucocorticoids
Regulate carbohydrate, protein & fat metabolism leading to an increase in blood glucose level
•Cortisol is most important one.
Raises blood glucose by promoting breakdown of:
1. Muscle proteins
2. Fatty acids
Cortisol also counteracts the inflammatory response & can reduce pain of arthritis.
However, it suppresses immune system. – –

46. Adrenal Cortex (cont’d)
Cortex also produces small amounts of male & female sex hormones in both sexes. – –

47. The Effects of Anabolic Steroid Use

48. Pancreas Made up of exocrine & endocrine tissues.
Pancreatic Islets (Langerhans)
The endocrine portion of pancreas. Produces & secretes two hormones:
•Insulin
•Glucagon
Exocrine portion produces & secretes digestive enzymes – –

49. Pancreas -  (Beta) Cells
Make & secrete:
•Insulin
Released when there is high blood glucose levels; usually just after eating •Actions of insulin:
1. Stimulates uptake of glucose by cells, especially liver, muscle & adipose tissues
2. Promotes storage of glycogen in liver & muscles
3. Overall effect is to lower the blood glucose levels. – –

50. Pancreas -  (Alpha) Cells
Make & secrete:
•Glucagon
Released when there is lower blood glucose levels; usually in between meals •Actions of glucagon:
1. Stimulates liver to breakdown glycogen
2. Promotes breakdown of fat to glycerol & fatty acids
3. Overall effect is to increase the blood glucose levels. – –

51. Regulating blood sugar levels
beta islet cells
triggers uptake of glucose by body cells
triggers storage in liver
- depresses appetite
pancreas
- triggers release of glucose by liver
- stimulates appetite
pancreas
alpha islet cells

52. Diabetes Mellitus
Disease in which liver cells, & most body cells, are unable to take up glucose as they should.
•Symptoms:
1. Rise in blood glucose levels
2. Extreme hunger
3. Frequent urination leads to thirst
4. Glucose in the urine
Two types of Diabetes:
1. Type 1 Diabetes
Pancreas not producing insulin
2. Type 2 Diabetes
Cells don’t respond to insulin that is there – –

53. Other Endocrine Organs
Gonads:
•Testes
Produce androgens (male sex hormones = testosterone)
These bring about secondary sex characteristics
•Ovaries
Produce female hormones, estrogen & progesterone
Involved in monthly menstrual cycle
Also bring about secondary sex characteristics – –

54. Other Endocrine Organs
Pineal Gland:
Located at base of brain.
Produces melatonin. Involved in circadian rhythms (daily 24-hour cycles)
Thymus Gland
Produce thymosins
Involved in differentiation of T lymphocytes – –

55. Melatonin Production