Copyright 2009, John Wiley & Sons, Inc. Pancreas
Jan 13, 2016
Copyright 2009, John Wiley & Sons, Inc.
Pancreas
Copyright 2009, John Wiley & Sons, Inc.
Pancreatic Islets
Both exocrine and endocrine gland Roughly 99% of cells produce digestive enzymes Pancreatic islets or islets of Langerhans
Alpha or A cells secrete glucagon – raises blood sugar Beta or B cells secrete insulin – lowers blood sugar Delta or D cells secrete somatostatin – inhibits both insulin
and glucagon F cells secrete pancreatic polypeptide – inhibits
somatostatin, gallbladder contraction, and secretion of pancreatic digestive enzymes
18-3
Cell Types in the Pancreatic Islets
Alpha cells (20%) produce glucagon Beta cells (70%) produce insulin Delta cells (5%) produce somatostatin F cells produce pancreatic polypeptide
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
1
GLUCAGON
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
GLUCAGON
1
2 Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
GLUCAGON
1
2
3
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
GLUCAGON
1
2
3
4
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
GLUCAGON
1 5
2
3
4
INSULIN
Insulin acts on variousbody cells to:
• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
INSULINGLUCAGON
1 5
2
3
4
6 Insulin acts on variousbody cells to:
• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis
Blood glucose level falls
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
INSULINGLUCAGON
1 5
2
3
4
6
7
Insulin acts on variousbody cells to:
• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis
If blood glucose continuesto fall, hypoglycemiainhibits release ofinsulin
Blood glucose level falls
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
INSULINGLUCAGON
1 5
2
3
4
6
7
8
Copyright 2009, John Wiley & Sons, Inc.
Pineal Gland
Copyright 2009, John Wiley & Sons, Inc.
Pineal Gland
Attached to roof of 3rd ventricle of brain at midline
Masses of neuroglia and pinealocytes Melatonin – amine hormone derived from
serotonin Appears to contribute to setting biological
clock More melatonin liberated during darkness
than light
SCN lesioning
Tau mutant with period of ~20h
Wild type animal with period of ~24h
Transplanting SCN of donor with ~20-h period
Wild type animal acquiresperiod of donor (~20h)
SCN lesioning abolishes circadian rhythm
A
B
C
SCN and sleep
Modified from Ralph and Lehman, Trends Neuro 1991
Melatonin: Produced by pineal gland, released at night-inhibited during the day (circadian regulation); initiates and maintain sleep; treat symptoms of jet lag and insomnia
Hypothalamus and Pituitary Gland
Copyright 2009, John Wiley & Sons, Inc.
Anterior pituitary
Release of hormones stimulated by releasing and inhibiting hormones from the hypothalamus
Also regulated by negative feedback Hypothalamic hormones made by
neurosecretory cells transported by hypophyseal portal system
Anterior pituitary hormones that act on other endocrine systems called tropic hormones
Copyright 2009, John Wiley & Sons, Inc.
Hormones of the Anterior Pituitary1. Human growth hormone (hGH) or somatotropin
Stimulates secretion of insulin-like growth factors (IGFs) that promote growth, protein synthesis
2. Thyroid-stimulating hormone (TSH) or thyrotropin Stimulates synthesis and secretion of thyroid hormones by
thyroid
3. Follicle-stimulating hormone (FSH) Ovaries initiates development of oocytes, testes stimulates
testosterone production
4. Luteinizing hormone (LH) Ovaries stimulates ovulation, testes stimulates testosterone
production
Copyright 2009, John Wiley & Sons, Inc.
Hormones of the Anterior Pituitary5. Prolactin (PRL)
Promotes milk secretion by mammary glands
6. Adrenocorticotropic hormone (ACTH) or corticotropin
Stimulates glucocorticoid secretion by adrenal cortex
7. Melanocyte-stimulating Hormone (MSH)
Copyright 2009, John Wiley & Sons, Inc.
Function of Anterior Pituitary Hormones
18-15
1) Human Growth Hormone Increases synthesis of insulin-like growth factors
“(IGFs) or somatomedins” at target cells target cells are liver, skeletal muscle, cartilage
and bone. IGF will work locally or enter bloodstream and they will lead to: increases cell growth & cell division Increases cell uptake of amino acids & synthesis of
proteins stimulate lipolysis in adipose so fatty acids used for
ATP retard use of glucose for ATP production so blood
glucose levels remain high enough to supply brain
18-16
Regulation of hGH Low blood sugar stimulates
release of GNRH from hypothalamus anterior pituitary releases
more hGH, more glycogen broken down into glucose by liver cells
High blood sugar stimulates release of GHIH from hypothalamus less hGH from anterior
pituitary, glycogen does not breakdown into glucose
18-17
Diabetogenic Effect of Human Growth Hormone Excess of growth hormone
raises blood glucose concentration pancreas releases insulin continually beta-cell burnout
Diabetogenic effect causes diabetes mellitis
18-18
2) Thyroid Stimulating Hormone (TSH)
Hypothalamus regulates the production of Thyroid Stimulating Hormone (TSH)
TSH stimulates the synthesis & secretion of T3 and T4 at thyroid gland
Metabolic rate stimulated
18-19
3) Follicle Stimulating Hormone (FSH)
FSH functions initiates the formation of follicles within the ovary stimulates follicle cells to secrete estrogen stimulates sperm production in testes
18-20
4) Luteinizing Hormone (LH)
In females, LH stimulates secretion of estrogen(with FSH) ovulation of secondary oocyte from ovary formation of corpus luteum secretion of progesterone
In males, stimulates interstitial cells to secrete testosterone
5) Prolactin (PRL)
Under right conditions, prolactin causes milk production
Suckling reduces cause prolactin levels rise along with milk production
Nursing ceases & milk production slows
18-22
6) Adrenocorticotrophic Hormone
ACTH stimulates cells of the adrenal cortex that produce glucocorticoids
18-23
7) Melanocyte-Stimulating Hormone Releasing hormone from hypothalamus
increases its release From the anterior pituitary
Function not certain in humans (increase skin pigmentation in frogs )
Copyright 2009, John Wiley & Sons, Inc.
Regulation of Ant. Pitutary Hormone Secretion
negative feedback
Hypothalamus
Hypothalamus Hypothalamus is a section of
brain above where pituitary gland is suspended from by infundibulum or stalk
Functions of hypothalamus
• Endocrine function
• Caloric balance
• Osmolarity balance
• Thermal regulation
• Autonomic balance
• Sleep
• Affective behavior
• Memory
• Somatic movements
Copyright 2009, John Wiley & Sons, Inc.
Hypothalamus Hypothalamus is a section of brain above
where pituitary gland is suspended from by infundibulum or stalk
Hypothalamus is a major link between nervous and endocrine system
It receives input from cortex, thalamus, limbic system & internal organs
Is influenced by emotions and the metabolic state of the individual
Hypothalamus Releasing Hormones: Secretion Synthesizes hormones in cell bodies of neurons
Hormones are transported down the axon and stored in the nerve endings
Hypothalamus Releasing Hormones: Secretion Synthesizes hormones in cell bodies of neurons
Hormones are transported down the axon and stored in the nerve endings
Delivered to the anterior pituitary via the hypothalamic-hypophyseal portal system
Usually initiates a three-hormone sequence Hypothalamus controls pituitary gland with 7
different releasing & inhibiting hormones
Hypothalamus and anterior pituitary
18-33
Flow of Blood to Anterior Pituitary
Controlling hormones enter blood Travel through portal veins Enter anterior pituitary at capillaries
Hypothalamic control of anterior pituitary secretions
Hypothalamus Releasing Hormones: Secretion Synthesizes hormones in cell bodies of neurons
Hormones are transported down the axon and stored in the nerve endings
Delivered to the anterior pituitary via the hypothalamic-hypophyseal portal system
Usually initiates a three-hormone sequence Hypothalamus controls pituitary gland with 7
different releasing & inhibiting hormones
Endocrine Control: Three Levels of Integration
Figure 7-13: Hormones of the hypothalamic-anterior pituitary pathway
Hypothalamus Releasing Hormones: Secretion Synthesizes hormones in cell bodies of neurons
Hormones are transported down the axon and stored in the nerve endings
Delivered to the anterior pituitary via the hypothalamic-hypophyseal portal system
Usually initiates a three-hormone sequence Hypothalamus controls pituitary gland with 7
different releasing & inhibiting hormones
Hypothalamic control of anterior pituitary
Effect on Ant Pituitary
Hormones
(+) TSH & Prolactin Thyrotropin-releasing hormone (TRH)
1.
(+) ACTH Corticotropin-releasing hormone (CRH)
2.
(+) GH Growth hormone releasing hormone (GHRH)
3.
(+) Prolactin Prolactin releasing hormone (PRH) 4.
(+) Gonadotropic hormones
(LH, & FSH)
Gonadotropin-releasing hormone (GnRH)
5.
(-) Prolactin Prolactin inhibitory hormone (PIH)“Dopamine”
6.
(-) GH(-) TSH
Growth hormone inhibitory hormone (GHIH) “Somatostatin (SS)”
7.
Hypothalamic hormones
Copyright 2009, John Wiley & Sons, Inc.
Hypothalamus
FSH & LH GH
Anterior Pituitary
GHIH/SSGHRHGnRH TRH PRIH PRH CRH
TSH Prolactin ACTH+ - -+ + + - + +
Copyright 2009, John Wiley & Sons, Inc.
Regulation of Ant. Pitutary Hormone Secretion
negative feedback
Hypothalamus
Copyright 2009, John Wiley & Sons, Inc.
Negative Feedback Regulation
Low blood glucose(hypoglycemia)stimulates release of
GHRH
1 Low blood glucose(hypoglycemia)stimulates release of
hGH
GHRH stimulatessecretionof hGH bysomatotrophs
GHRH
1
2
Low blood glucose(hypoglycemia)stimulates release of
hGH
GHRH stimulatessecretionof hGH bysomatotrophs
GHRH
hGH and IGFs speedup breakdown of liverglycogen into glucose,which enters the bloodmore rapidly
1
3
2
Low blood glucose(hypoglycemia)stimulates release of
hGH
GHRH stimulatessecretionof hGH bysomatotrophs
GHRH
hGH and IGFs speedup breakdown of liverglycogen into glucose,which enters the bloodmore rapidly
Blood glucose levelrises to normal(about 90 mg/100 mL)
1
3
4
2
Low blood glucose(hypoglycemia)stimulates release of
hGH
GHRH stimulatessecretionof hGH bysomatotrophs
GHRH
hGH and IGFs speedup breakdown of liverglycogen into glucose,which enters the bloodmore rapidly
Blood glucose levelrises to normal(about 90 mg/100 mL)
If blood glucosecontinues to increase,hyperglycemia inhibitsrelease of GHRH
1
3
4
5
2
Anteriorpituitary
Low blood glucose(hypoglycemia)stimulates release of
High blood glucose(hyperglycemia)stimulates release of
hGH
GHRH stimulatessecretionof hGH bysomatotrophs
GHIHGHRH
hGH and IGFs speedup breakdown of liverglycogen into glucose,which enters the bloodmore rapidly
Blood glucose levelrises to normal(about 90 mg/100 mL)
If blood glucosecontinues to increase,hyperglycemia inhibitsrelease of GHRH
1 6
3
4
5
2
Anteriorpituitary
GHIH inhibitssecretion ofhGH bysomatotrophs
Low blood glucose(hypoglycemia)stimulates release of
High blood glucose(hyperglycemia)stimulates release of
hGH
GHRH stimulatessecretionof hGH bysomatotrophs
GHIHGHRH
hGH and IGFs speedup breakdown of liverglycogen into glucose,which enters the bloodmore rapidly
Blood glucose levelrises to normal(about 90 mg/100 mL)
If blood glucosecontinues to increase,hyperglycemia inhibitsrelease of GHRH
1 6
7
3
4
5
2 GHIH inhibitssecretion ofhGH bysomatotrophs
Low blood glucose(hypoglycemia)stimulates release of
High blood glucose(hyperglycemia)stimulates release of
Anteriorpituitary
hGH
GHRH stimulatessecretionof hGH bysomatotrophs
GHIHGHRH
A low level of hGH andIGFs decreases the rateof glycogen breakdownin the liver and glucoseenters the blood moreslowly
hGH and IGFs speedup breakdown of liverglycogen into glucose,which enters the bloodmore rapidly
Blood glucose levelrises to normal(about 90 mg/100 mL)
If blood glucosecontinues to increase,hyperglycemia inhibitsrelease of GHRH
1 6
7
83
4
5
2 GHIH inhibitssecretion ofhGH bysomatotrophs
Low blood glucose(hypoglycemia)stimulates release of
High blood glucose(hyperglycemia)stimulates release of
Anteriorpituitary
hGH
GHRH stimulatessecretionof hGH bysomatotrophs
GHIHGHRH
A low level of hGH andIGFs decreases the rateof glycogen breakdownin the liver and glucoseenters the blood moreslowly
Blood glucose levelfalls to normal(about 90 mg/100 mL)
hGH and IGFs speedup breakdown of liverglycogen into glucose,which enters the bloodmore rapidly
Blood glucose levelrises to normal(about 90 mg/100 mL)
If blood glucosecontinues to increase,hyperglycemia inhibitsrelease of GHRH
1 6
7
8
9
3
4
5
2 GHIH inhibitssecretion ofhGH bysomatotrophs
Low blood glucose(hypoglycemia)stimulates release of
High blood glucose(hyperglycemia)stimulates release of
Anteriorpituitary
hGH
GHRH stimulatessecretionof hGH bysomatotrophs
GHIHGHRH
A low level of hGH andIGFs decreases the rateof glycogen breakdownin the liver and glucoseenters the blood moreslowly
Blood glucose levelfalls to normal(about 90 mg/100 mL)
hGH and IGFs speedup breakdown of liverglycogen into glucose,which enters the bloodmore rapidly
Blood glucose levelrises to normal(about 90 mg/100 mL)
If blood glucosecontinues to increase,hyperglycemia inhibitsrelease of GHRH
If blood glucosecontinues to decrease,hypoglycemia inhibitsrelease of GHIH
1 6
7
8
9
10
3
4
5
2