1. 13.1 Hypothalamus and Pituitary Gland
Chapter 13 Endocrine System
13.1 Hypothalamus and Pituitary Gland

2. Endocrine System Endocrine system releases hormones into the blood
Blood delivers hormones throughout the body
Endocrine system acts more slowly than the nervous system
Endocrine system consists of the Endocrine glands
Pituitary, thyroid, parathyroid, adrenal and pineal glands
Also consist of other organs and tissues not specifically part of the Endocrine system
Hypothalamus, pancreas, ovaries, testes, kidneys, liver

4. Hormone Functions Regulation of: Control growth and development
Chemical composition and volume of interstitial fluid
Metabolism and energy balance
Contraction of smooth and cardiac muscle
Gland secretions
Control growth and development
Regulate operation of reproductive system
Help establish circadian rhythm

5. Hormone Actions
Endocrine hormones are delivered throughout the body via the blood
Hormones only affect specific target cells
Hormones bind to specific receptors on the target cells
Only target cells for a given hormone have receptors that bind and recognize that hormone
Hormone secretion is controlled by signals from the nervous system, chemical changes in the blood, other hormones

6. Hypothalamus and Pituitary Gland
Hypothalamus: small region in the brain
Synthesizes 9 hormones
Pituitary Gland: secretes hormones that control other Endocrine glands
Composed of 2 lobes
Anterior Pituitary
Posterior Pituitary
Pituitary hormones are controlled by inhibiting and releasing hormones produced by the hypothalamus

7. Hypothalamus and Pituitary Gland
Anterior Pituitary Hormones
Human Growth Hormone (hGH): most abundant anterior pituitary hormone
Synthesizes and secretes insulin growth factors (IGF)
Stimulate protein synthesis, help maintain muscle and bone mass, promote healing of injuries and tissue repair
Control of hGH secretion:
Growth hormone-releasing hormone (GHRH): promotes secretion of hGH
Growth hormone-inhibiting hormone (GHIH): stops secretion of hGH

8. Hypothalamus and Pituitary Gland
Anterior Pituitary Hormones
Control of hGH secretion example:
Low blood sugar levels (hypoglycemia) stimulates the hypothalamus to secrete GHRH (Growth hormone-releasing hormone)
High blood sugar levels (hyperglycemia) inhibits the release of GHRH and stimulates the release of GHIH (Growth hormone-inhibiting hormone)
Thyroid-Stimulating Hormone (TSH): stimulates synthesis and secretion of thyroid hormones
Thyrotropin-releasing hormone (TRH) from the hypothalamus controls TSH secretion via negative feedback
There is no Thyrotropin-inhibiting hormone

9. Hypothalamus and Pituitary Gland
Anterior Pituitary Hormones
Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH)
Females: FSH initiates development of ovarian follicles
LH triggers ovulation
Both FSH and LH stimulate follicular cells to secrete estrogen
Males: FSH stimulates sperm production in the testes
LH stimulates testes to secrete testosterone
Gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates release of FSH and LH
Release of FSH, LH, GnRH is suppressed by estrogen in females and testosterone in males via negative feedback loops

10. Hypothalamus and Pituitary Gland
Anterior Pituitary Hormones
Prolactin (PRL)
Helps stimulate milk production
Prolactin-inhibiting hormone (PIH) suppresses release of prolactin
Prolactin-releasing hormone (PRH) stimulates a rise in prolactin level during pregnancy
Adrenocorticotropic Hormone (ACTH)
Produces and secretes glucocorticoid hormone
Corticotrophin-releasing hormone (CRH) from the hypothalamus stimulates secretion of ACTH
Release is caused by low-blood glucose or physical trauma

11. Hypothalamus and Pituitary Gland
Posterior Pituitary Hormones
Doesn’t synthesize hormones but it stores and releases 2 hormones
Oxytocin
Stimulates contraction of the uterus and ejection of milk from the breast
Secretion is stimulated by uterine stretching
Function in males and in non-pregnant females is unknown
Partly responsible for feelings of sexual pleasure during and after intercourse

12. Hypothalamus and Pituitary Gland
Posterior Pituitary Hormones
Antidiuretic Hormone (ADH)
Acts to retain body water and increase blood pressure
Causes the kidneys to retain more water = decreasing urine volume
Without ADH urine output increase from 1-2 liters to 20 liters a day
Amount of ADH secreted depends on blood osmotic pressure and blood volume
As blood volume FALLS --> blood osmotic pressure RISES
As blood volume RISES --> blood osmotic pressure FALLS

13. Hypothalamus and Pituitary Gland
Posterior Pituitary Hormones
Regulation of Secretion and actions of ADH
High osmotic pressure (drop in blood volume) due to dehydration stimulates osmoreceptors
Neurosecretory cells receive excitatory input from the osomoreceptors
Generate nerve impulses that cause the release of ADH in the posterior pituitary

14. Hypothalamus and Pituitary Gland
Posterior Pituitary Hormones
Blood carries ADH to 3 target tissues:
Kidneys: respond by retaining more water  decreasing urine output
Sweat glands: lowers rate of water loss by perspiration from the skin
Smooth muscle walls in the arteries: artery walls to constrict  increasing blood pressure
Low blood osmotic pressure or highblood volume inhibits osmoreceptors
Inhibition of osmoreceptors reduces or stops ADH secretion
Causing the opposite effect on the target organs

15. Check for Understanding 1
4 functions of hormones
Explain how target cells and receptors affect hormone actions
Most abundant anterior pituitary hormone
If your blood pressure drops what hormone is secreted in order to raise it again
In order for our body to release hGH what must be released first
Initiates follicle development in females and sperm production in males

16. Check for Understanding 1
Regulation, Control of growth and development, regulate reproductive system, establish circadian rhythm
Endocrine glands secrete a hormone, that hormone will only be able to affect a target cell with a receptor for that hormone
Human Growth Hormone (hGH)
Antidiuretic Hormone (ADH)
Human Growth Hormone releasing Hormone (GHRH)
Follicle Stimulating Hormone (FSH)