1. Endocrine System
Chapter 32

2. Homeostasis
Organisms use homeostasis to maintain a “steady state” or internal balance regardless of external environment
In humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level
Regulation of room temperature by a thermostat is analogous to homeostasis

3. Sensor/ control center: Thermostat turns heater off. Response:
Heating stops.
Room
temperature
decreases.
Stimulus:
Room
temperature
increases.
Set point:
Room temperature
at 20C
Figure 32.4 A nonliving example of temperature regulation: control of room temperature
Stimulus:
Room
temperature
decreases.
Room
temperature
increases.
Response:
Heating starts.
Sensor/
control center:
Thermostat
turns heater on. 3

4. Sensor/control center: Thermostat in hypothalamus Response: Sweat
Blood vessels
in skin dilate.
Stimulus:
Increased body
temperature
Body
temperature
decreases.
Homeostasis:
Internal body
temperature of
approximately
36–38C
Body
temperature
increases.
Stimulus:
Decreased body
temperature
Figure 32.8 The thermostatic function of the hypothalamus in human thermoregulation
Response:
Blood vessels
in skin constrict.
Sensor/control center: Thermostat
in hypothalamus
Response: Shivering 4

5. Homeostasis
Homeostasis in animals relies largely on negative feedback, a control mechanism that reduces the stimulus
Homeostasis moderates, but does not eliminate, changes in the internal environment
Set points and normal ranges for homeostasis are usually stable, but certain regulated changes in the internal environment are essential

6. Animation: Negative Feedback
Right click slide / Select play

7. Animation: Positive Feedback
Right click slide / Select play

8. Feedback Mechanisms negative feedback helps to maintain homeostasis
positive feedback
enhances an already existing response

9. Nervous vs Endocrine Nervous immediate
acts thru electrical impulses and neurotransmitters
effect is localized and short duration
Endocrine
acts thru chemicals – hormones
act on cells with receptors
effect is generalized and long term duration

10. Endocrine cell Cell body of neuron
(a) Signaling by hormones
(b) Signaling by neurons
Stimulus
Stimulus
Endocrine
cell
Cell
body of
neuron
Nerve
impulse
Axon
Hormone
Signal
travels
everywhere.
Signal
travels to
a specific
location.
Blood
vessel
Nerve
impulse
Figure 32.9 Signaling in the endocrine and nervous systems
Axons
Response
Response 10

11. Neuroendocrine Pathways
Hormone pathways that respond to stimuli from the external environment rely on a sensor in the nervous system
In vertebrates, the hypothalamus integrates endocrine and nervous systems
Signals from the hypothalamus travel to a gland located at its base, called the pituitary gland
Anterior pituitary
Posterior pituitary 11

12. Hypothalamus region in the forebrain regulates internal environment
contains hormone-secreting cells
produces and releases
ADH, Oxytocin
interacts with pituitary
contains releasing hormones
pituitary gland

13. Pituitary Gland pea-sized gland at base of hypothalamus
contains stimulating hormones
two lobes
posterior lobe
stores and secretes hormones synthesized in the hypothalamus
antidiuretic hormone (ADH)
released in response to blood being concentrated
goes to kidney
* causes water to be reabsorbed
negative feedback

16. Pituitary Gland Oxytocin uterine contractions milk letdown
positive feedback

17. Posterior pituitary function
Pituitary Gland
Posterior pituitary function

18. Pituitary Gland anterior pituitary affecting other glands
thyroid stimulating hormone (TSH)
Triiodothyronine / tyroxine
* both regulate metabolism and growth
rate increases

19. Pituitary Gland adrenocorticotropic hormone (ACTH) adrenal cortex
release of cortisol
raises blood sugar levels
counteracts inflammation
gonadotropic hormone
follicle stimulating (FSH)
luteinizing hormone (LH)
stimulates ovaries and testis to produce gametes

20. Pituitary Gland not affecting other glands
meloncyte stimulating hormone (MSH)
skin color changes
prolactin (PRL)
milk production
carbohydrate / fat metabolism
growth hormone
skeletal and muscular growth
increases the rate of amino acids entering cells to produce proteins

21. Anterior pituitary function
Pituitary Gland
Anterior pituitary function

22. Hypothalamus and pituitary
Pituitary Gland
Hypothalamus and pituitary

23. Hormones Classified as protein or protein derivative
bind to receptor on cell membrane
steroid
receptors are located within the cytoplasm of the cell
react with receptor site on selected cells
secreted by endocrine glands, endocrine cells, and certain neurons
travel through the bloodstream to nonadjacent target cells
chemical signal
communication between cells, body parts

24. Hormones prostaglandins local hormone not carried by blood
affects neighboring cells
promotes pain and inflammation
growth hormones
promotes cell division

25. Hormones pheromones affect metabolism
influence the behavior of another individual
active between animals not humans

26. Hormone Action activation of receptor transduction of signal
functional response

27. Action of Hormones wide range of effects induce target cells
2 ways hormones can influence cell metabolism
1.) peptide hormone
peptides, proteins, glycoproteins, modified amino acids
Glucagon, ADH, oxytocin, TRH, insulin, somatotropin, prolactin, FSH, LH, TSH

28. Mechanism of a peptide hormone
Protein Hormone
Mechanism of a peptide hormone

29. Protein Hormone hormone binds to a receptor at cell surface
glucagon
hormone binds to a receptor at cell surface
binding triggers a change in activity of enzymes inside the cell
glucagon receptor
cyclic AMP
+ Pi
ATP
cAMP activates
protein kinase A
Protein kinase A converts phosphorylase
kinase to active form and inhibits an
enzyme required for glucagon synthesis.

30. Action of Hormones 2.) steroid hormone act more slowly
action lasts longer
limited to adrenal cortex, ovaries and testis
Estrogens, progestins, androgens, cortisol, aldosterone
derived from cholesterol
enters the cell because they are lipids
binds with DNA
activates transcription
inhibits transcription

31. Mechanism of a steroid hormone
Steroid Hormones
Mechanism of a steroid hormone

32. Major Endocrine Glands and Their Hormones Hypothalamus
Pituitary gland
Anterior pituitary
Pineal gland
Melatonin
Posterior pituitary
Oxytocin
Vasopressin
(antidiuretic
hormone, ADH)
Thyroid gland
Thyroid hormone
(T3 and T4)
Calcitonin
Adrenal glands
(atop kidneys)
Parathyroid glands
Parathyroid hormone (PTH)
Adrenal medulla
Epinephrine and
norepinephrine
Ovaries (in females)
Estrogens
Progestins
Figure 32.11a Exploring the human endocrine system (part 1: glands and hormones)
Adrenal cortex
Glucocorticoids
Mineralocorticoids
Testes
(in males)
Androgens
Pancreas
Insulin
Glucagon 32

33. Thyroid Gland epiglottis thyroid cartilage (Adam’s apple) pharynx
trachea (windpipe)
parathyroid gland
anterior
posterior

34. Stimulus
Response
Blood level of thyroid hormone falls below a set point. +
Hypothalamus –
TRH –
Anterior Pituitary
Rise in the blood level of thyroid hormone inhibits secretion of TRH and TSH.
TSH
Thyroid Gland
Thyroid hormone
is secreted

35. Thyroid/Parathyroid located in the neck largest gland
stimulates all cells to metabolize faster
more glucose broken down, more energy used
contains
triiodthyronine (T3) / thyroxine (T4)
regulates metabolism and growth rate

36. Thyroid/Parathyroid lack of iodine can result in a simple goiter
hypothyrodism
minimal production
cretinism
failure of thyroid to develop properly
results in stunted growth
myxedema
adults
lethargy, weight gain, loss of hair, slower pulse rate, lowered body temperature

38. Thyroid/Parathyroid hyperthyroidism overproduction exophthalmic goiter
eyes protrude due to swelling of the muscles that moves the eyes

39. Parathyroid hormone action
Parathyroid Gland
Parathyroid hormone action

40. Calcium Regulation calcium levels high calcitonin
regulates calcium levels in the blood
secreted by thyroid gland in response to high levels
causes calcium to be deposited in the bone tissue
osteoblasts
reduces the activity and number of osteoclasts
cell that causes the erosion of bone

41. Calcium Regulation parathyroid glands calcium levels too low PTH
released in response to low calcium levels
promotes the activity of osteoclasts
promotes the reabsorption of calcium by the kidneys
activates vitamin D
stimulates the absorption of Ca from the intestine

43. Calcium Regulation hyperparathyrodism Ca levels too high
results in tetany
body shakes from continuous muscle contractions
brought about by increased excitability of nerves
hypoparathyrodism
Ca levels too low
bones become soft and fragile

44. Adrenal Glands sit atop the kidneys consists of adrenal medulla
inner portion
produces epinephrine and norepinephrin
brings about bodily changes
emergency
responsible for fight-flight response to stress and excitement
effects are short term

46. Same receptors but different intracellular proteins (not shown)
Different receptors
Different cellular responses
Different cellular responses
Epinephrine
Epinephrine
Epinephrine
 receptor
 receptor
 receptor
Glycogen
deposits
Figure One hormone, different effects
Vessel
dilates.
Vessel
constricts.
Glycogen
breaks down
and glucose
is released
from cell.
(a) Liver cell
(b) Skeletal muscle
blood vessel
(c) Intestinal blood
vessel 46

47. Adrenal Glands adrenal cortex outer portion secretes cortisol
maintains glucose levels in the absence of food
inhibits blood glucose uptake by muscle and other tissues
causes breakdown of proteins to amino acids and conversion to glucose
causes degradation of adipose tissue to fatty acids for use as energy source

48. Adrenal Glands feedback control of cortisol secretion
hypothalamus senses rise in glucose and secretes less releasing hormone (CRH)
corticotropin-releasing hormone
anterior pituitary responds by secreting less ACTH
adrenocorticotropic hormone
adrenal cortex slows its secretion of cortisol

49. Control of cortisol secretion
Adrenal Cortex
Control of cortisol secretion

50. Adrenal Glands mineralocorticoids regulate salt and water balance
leads to an increase in blood volume and blood pressure

51. Control of Glucose Metabolism
Hormones and glucose metabolism

52. Pancreatic Hormones lies between the kidney and near the duodenum
secretes
insulin
high blood glucose (sugar)
stimulates uptake of glucose by
liver cells
adipose cells
muscle cells
stored as glycogen
lowers blood sugar

53. Pancreatic Hormones glucagon low blood glucose
major target are the liver and adipose tissue
stimulates liver to break down glycogen
uses fat and protein in preference to glucose as energy
adipose tissue cells break down fat to glycerol and fatty acids
liver then takes these up and uses them as substrates for glucose formation

54. Excess glucose accumulates
Diabetes Mellitus
Excess glucose accumulates
Type 2
target cells don’t respond
usually appears in adults
diet, drugs
Type 1
autoimmune disease
usually appears in childhood
insulin injections

56. Hormones in the Balance
Impacts, Issues Video
Hormones in the Balance