1. Endocrine System I: Superior Glands
Homeostatic Mechanisms
Endocrine System vs Nervous System
Endocrine vs Exocrine Glands
Types and Actions of Hormones
Interaction of Hormones with Target Cells
Effects of Hormones on Target
Control Mechanisms of Endocrine Glands
Endocrine Signaling as Simple/Complex Reflexes
Major Superior Endocrine Organs
Pituitary
Anterior: GH, Pl, FSH, LH, TSH, ACTH
Posterior: Oxytocin, ADH
Thyroid: TH synthesis and release; Calcitonin
Parathyroids: PTH

2. Homeostasis
Maintenance of a stable internal environment = a dynamic state of equilibrium

3. Feedback Mechanisms Example of Negative feedback Receptor and
Low blood glucose

4. Feedback Mechanisms
Examples of Positive feedback

5. Endocrine System I: Superior Glands
Homeostatic Mechanisms
Endocrine System vs Nervous System
Endocrine vs Exocrine Glands
Types and Actions of Hormones
Interaction of Hormones with Target Cells
Effects of Hormones on Target
Control Mechanisms of Endocrine Glands
Endocrine Signaling as Simple/Complex Reflexes
Major Superior Endocrine Organs
Pituitary
Anterior: GH, Pl, FSH, LH, TSH, ACTH
Posterior: Oxytocin, ADH
Thyroid: TH synthesis and release; Calcitonin
Parathyroids: PTH

6. The Endocrine System
A more broad-based and long-lasting communication system than the nervous system
Uses chemical messages (hormones) that are released into the blood
Hormones control several major processes
Reproduction
Growth and development
Mobilization of body defenses
Maintenance of much of homeostasis
Regulation of metabolism

7. Comparing Two Control Systems
Mode of Messaging
Speed of Signaling
Length of Response Time
Range of Focus
Nervous System
Endocrine System
Short duration; response stops in seconds or minutes
Neuron “wiring” leading directly to and from target
Narrow & specific, a few cells to part of one organ
Rapid, in milliseconds
Hormones travel through blood stream systemically
Broad & general; many target tissues and organs stimulated collectively
Long-lasting; minutes to days
Slow; minutes, hours, or days

8. Endocrine System I: Superior Glands
Homeostatic Mechanisms
Endocrine System vs Nervous System
Endocrine vs Exocrine Glands
Types and Actions of Hormones
Interaction of Hormones with Target Cells
Effects of Hormones on Target
Control Mechanisms of Endocrine Glands
Endocrine Signaling as Simple/Complex Reflexes
Major Superior Endocrine Organs
Pituitary
Anterior: GH, Pl, FSH, LH, TSH, ACTH
Posterior: Oxytocin, ADH
Thyroid: TH synthesis and release; Calcitonin
Parathyroids: PTH

9. Glandular Epithelium
Gland – one or more cells that secretes a particular product
Two major gland types
Endocrine gland
Ductless
Secretions are hormones
Exocrine gland
Empty through ducts to the epithelial surface
Include sweat and oil glands

10. Types of Hormones Peptide-based hormones Steroid hormones
Prostaglandins and catecholamines
Insulin Growth hormone

11. Hormones as Chemical Messengers
Endocrine gland (source)
Target organs or glands
Hormones move through the bloodstream to target organs

12. Endocrine System I: Superior Glands
Homeostatic Mechanisms
Endocrine System vs Nervous System
Endocrine vs Exocrine Glands
Types and Actions of Hormones
Interaction of Hormones with Target Cells
Effects of Hormones on Target
Control Mechanisms of Endocrine Glands
Endocrine Signaling as Simple/Complex Reflexes
Major Superior Endocrine Organs
Pituitary
Anterior: GH, Pl, FSH, LH, TSH, ACTH
Posterior: Oxytocin, ADH
Thyroid: TH synthesis and release; Calcitonin
Parathyroids: PTH

13. Hormone Interaction with Target Cells
Hormones bind to receptors sticking out from the plasma membrane of target cells or within target cells
growth factor insulin epinephrine
Hormones
Receptors
Examples of receptors found in the plasma membrane of cells

14. Two Mechanisms of Hormone Action
Non-steroid hormone action
1. Hormone binds to a membrane receptor; does not enter cell
2. Sets off a reaction where a G protein with bound GTP activates adenylate cyclase enzyme.
3. Adenylate cyclase produces cyclic AMP (second messenger) by converting ATP --> cAMP
5. cAMP, in turn, activates phosphorylating activation proteins (protein kinases) that trigger additional intracellular changes (enzyme activation, secretion, ion channel changes) to promote a specific response
(A few peptide hormones activate Ca+2 release via second messengers in the PIP2 calcium signaling system).
Adenylate
Cyclase G
protein
cAMP
Steroid hormone action
Diffuses through the plasma membrane of target cells
Enters the nucleus or binds to cytoplasmic receptor
Binds to a specific protein within the nucleus if not already bound
Binds to specific sites on the cell’s DNA
Activates genes that result in synthesis of new proteins

15. Endocrine System I: Superior Glands
Homeostatic Mechanisms
Endocrine System vs Nervous System
Endocrine vs Exocrine Glands
Types and Actions of Hormones
Interaction of Hormones with Target Cells
Effects of Hormones on Target
Control Mechanisms of Endocrine Glands
Endocrine Signaling as Simple/Complex Reflexes
Major Superior Endocrine Organs
Pituitary
Anterior: GH, Pl, FSH, LH, TSH, ACTH
Posterior: Oxytocin, ADH
Thyroid: TH synthesis and release; Calcitonin
Parathyroids: PTH

16. Effects Caused by Hormones
Changes in target cells by hormonal activation
Changes in plasma membrane permeability or electrical state
Synthesis of proteins, such as enzymes
Activation or inactivation of enzymes
Stimulation of mitosis
Activation of transcription of certain genes
Target cell activation depends on three factors
Blood levels of the hormone
Relative number of receptors on or in the target cell
Affinity of binding between receptor and hormone

17. Target Cell Activation
Hormones influence the number of their receptors
Up-regulation—target cells form more receptors in response to the hormone
Down-regulation—target cells lose receptors in response to the hormone
Hormones are removed from the blood by
Degrading enzymes
Kidneys
Liver
Half-life—the time required for a hormone’s blood level to decrease by half

18. Control of Hormone Release
Hormone levels in the blood are maintained by negative feedback
A stimulus or low hormone levels in the blood triggers the release of more hormone
Hormone release stops once an appropriate level in the blood is reached

19. Endocrine System I: Superior Glands
Homeostatic Mechanisms
Endocrine System vs Nervous System
Endocrine vs Exocrine Glands
Types and Actions of Hormones
Interaction of Hormones with Target Cells
Effects of Hormones on Target
Control Mechanisms of Endocrine Glands
Endocrine Signaling as Simple/Complex Reflexes
Major Superior Endocrine Organs
Pituitary
Anterior: GH, Pl, FSH, LH, TSH, ACTH
Posterior: Oxytocin, ADH
Thyroid: TH synthesis and release; Calcitonin
Parathyroids: PTH

20. Control Mechanisms of Endocrine Glands
Hormonal: Chemical stimulus (i.e. endocrine glands are activated by other hormones
Humoral: Changing blood levels of certain ions stimulate hormone release
Neural: Nerve impulses stimulate hormone release; most are under control of the sympathetic nervous system

21. Endocrine Signaling (Reflexes)
Simple Endocrine Reflex
Involves only one hormone
Controls hormone secretion by the heart, pancreas, parathyroid gland, and digestive tract
Complex Endocrine Reflex
Involves:
One or more intermediary steps
Two or more hormones (tropic hormones cause secretion of a second hormone in target glands)
The hypothalamus
Figure 9.3

22. Location of Major Endrocrine Organs
Figure 9.3