1. The Endocrine System

2. Hormones may have effects in a single location or throughout the body
The Endocrine System
Signaling molecules sent out by the endocrine system are called hormones
Hormones may have effects in a single location or throughout the body
Only cells with receptors for a certain hormone can respond to it
The endocrine system is well adapted for coordinating gradual changes that affect the entire body
© 2016 Pearson Education, Inc.

3. Hormone Overview
Hormones are produced by specialized cells in endocrine glands
Cells secrete hormones into interstitial fluid
Blood transfers hormones to target sites
These hormones regulate the activity of other cells

4. What type of signaling was this?.
What type of signaling was this?
(a) Signaling by hormones
STIMULUS
Endocrine
cell
Hormone
Signal
travels
everywhere.
Long-distance:
Called “endocrine” or
hormonal signaling
Blood
vessel
Figure 32.4a Signaling in the endocrine and nervous systems
Response

5. Hormones control several major processes
Reproduction
Growth and development
Mobilization of body defenses
Maintenance of much of homeostasis (electrolyte, water and nutrient balance of the blood)
Regulation of metabolism

6. © 2016 Pearson Education, Inc.
Thyroid gland
Pineal gland
Hypothalamus
Thyroid hormone (T3 and T4 )
Melatonin
Calcitonin
Pituitary gland
Parathyroid glands
Posterior pituitary
Parathyroid hormone (PTH)
Oxytocin
Vasopressin, also
called antidiuretic
hormone (ADH )
Adrenal glands (atop kidneys)
Adrenal medulla
Epinephrine and norepinephrine
Anterior pituitary
Adrenal cortex
Follicle-stimulating
hormone (FSH)
Glucocorticoids
Mineralocorticoids
Luteinizing
hormone (LH)
Thyroid-stimulating
hormone (TSH)
Ovaries (in females)
Estrogens
Adrenocorticotropic
hormone (ACTH)
Figure 32.5 The human endocrine system
Progesterone
Prolactin
Growth hormone (GH)
Testes (in males)
Melanocyte-stimulating
hormone (MSH)
Androgens
Pancreas
Insulin
Glucagon

7. Mechanisms of Hormone Action
Hormones affect only certain tissues or organs (target cells or organs)
Target cells must have specific protein receptors to be affected by a hormone
Hormone binding influences the working of the cells

8. Hormone Solubility
Nonsteroidal hormones are soluble in water but not in lipids
These hormones cannot pass through the plasma membrane of target cells
Instead, they bind to cell-surface receptors, and that triggers events leading to a cellular response
The intracellular response is called signal transduction
A signal transduction pathway typically has multiple steps

9. There, the receptor alters transcription of particular genes
Steroidal hormones are lipid soluble and bind to receptors inside cells
When bound by the hormone, the hormone-receptor complex moves into the nucleus
There, the receptor alters transcription of particular genes
© 2016 Pearson Education, Inc.

10. Multiple Effects of Hormones.
Multiple Effects of Hormones
Many hormones elicit more than one response
For example, epinephrine is secreted by the adrenal glands and can raise blood glucose levels, increase blood flow to muscles, and decrease blood flow to the digestive system
Target cells vary in their response to a hormone because they differ in their receptor types or in the molecules that produce the response

11. constricts, decreasing
© 2016 Pearson Education, Inc.
(a) Liver cell
(b) Smooth muscle cell in wall of blood vessel that supplies skeletal muscle
(c) Smooth muscle cell in wall of blood vessel that supplies intestines
Epinephrine
Epinephrine
Epinephrine
b receptor
b receptor
a receptor
Glycogen
deposits
Glucose
Figure One hormone, different effects (part 1: detail)
Glycogen breaks down
and glucose is released
from cell.
Cell relaxes.
Cell contracts.
Blood vessel dilates,
increasing flow to
skeletal muscle.
Blood vessel
constricts, decreasing
flow to intestines.
Blood glucose level
increases.

12. Regulating and Conforming
An animal that is a regulator uses internal mechanisms to control internal change despite external fluctuation
An animal that is a conformer allows its internal condition to change in accordance with external changes

13. (temperature conformer) Ambient (environmental)40
River otter (temperature regulator)
Body temperature (C) 30 20
Largemouth bass
(temperature conformer) 10
Figure Regulating and conforming 10 20 30 40
Ambient (environmental)
temperature (C)

14. The response returns the variable to the set point
Animals achieve homeostasis by maintaining a variable at or near a particular value, or set point
Fluctuations above or below the set point serve as a stimulus; these are detected by a sensor and trigger a response
The response returns the variable to the set point
© 2016 Pearson Education, Inc.

15. Stimulus: change in internal variable
NORMAL RANGE
for internal variable
Stimulus: change in
internal variable
Response
Figure 32.UN02 Summary of key concepts: feedback control
Control center
Sensor

16. Homeostasis in animals relies largely on negative feedback, a control mechanism that reduces the stimulus (positive feedback reinforces a stimulus to increase the response)
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
© 2016 Pearson Education, Inc.

17. . Response: Blood vessels in skin dilate. Thermostat in hypothalamus
activates cooling
mechanisms.
Response:
Sweat
Body temperature
increases.
Body temperature
decreases.
NORMAL BODY
TEMPERATURE
(approximately
36–38C)
Body temperature
increases.
Body temperature
decreases.
Figure The thermostatic function of the hypothalamus in human thermoregulation
Response: Shivering
Thermostat in
hypothalamus
activates warming
mechanisms.
Response: Blood
vessels in skin
constrict.

18. Thermostat turns heater off. Room temperature increases.
decreases.
ROOM
TEMPERATURE
AT 20C (set point)
Figure A nonliving example of temperature regulation: control of room temperature
Room temperature
increases.
Room temperature
decreases.
Thermostat
turns
heater on.