Endocrine System

p 960-972

Endocrine System

p. 960 Figure 45.5

p. 961 Table 45.1 Endocrine Glands and hormones

Endocrine Glands: specialized organs that produce hormones

• Contain no ducts; release hormones directly into bloodstream
• Endocrine cells release hormone from glands
• Exocrine glands; release hormones via a duct
• Example: sweat, mucus and digestive enzymes
• Neurosecretory cells- neurons that receive signals from other nerve cell; respond by releasing hormones into body or a storage organ where released at a later time.

How Hormones Work

• Target cells
• Cells that are affected by the hormones
• Hormones are specific

Gland X produces Hormone Y and this hormone has effects on Organ Z. Organ Z is target organ

• Tropic hormones (i.e. sex hormones) have other endocrine glands as their target cells

 

Negative Feedback System

• High levels of hormone signals endocrine system to slow down or shut down production
• Levels of hormone drops below “normal” endocrine systems will receive the start signal for production.

 

 

Endocrine System

Hypothalmus

• Functions as an endocrine gland
• Part of CNS (located in the lower region of the brain)
• Relays information between the endocrine and nervous system
• Example: Nervous system will detect seasonal temperatures changes; the hypothalamus then triggers release of reproductive hormones.
• Subject to feedback inhibition by hormones
• The neurosecretory cells secrete hormones that are either stored or regulate the activity of pituitary gland
• Pituitary Gland
• Called the master gland- secretes hormones that target other glands which stimulate them to secrete their own hormones
• Located at the base of the hypothalamus
• 2 Parts à     1. Anterior Pituitary               2. Posterior Pituitary

 

 

Anterior Pituitary

• Develops from a fold of tissue at the roof of the embryonic mouth that grows upward toward the brain…eventually loses connection with mouth.
• The hypothalamus secrete Releasing Hormones that stimulate the anterior pituitary and inhibit
• The hypothalamus secrete Inhibiting Hormones that inhibit the anterior pituitary and

 

Hormones

Growth Hormone GH- stimulates growth (especially in bones)

Adrenocorticotropic hormone ACTH- stimulates adrenal cortex to secrete its hormones

Thyroid-stimulating hormone TSH- stimulates thyroid to secrete hormones

FSH- Follicle-stimulating hormone- stimulates production of ova and sperm

LH- Luteinizing Hormone- stimulates ovaries and testes

Prolactin- stimulates milk production

Endorphins-also produced by the brain; inhibits perception to pain

 

Posterior Pituitary

• The posterior pituitary is actually an extension of the hypothalamus.
• The posterior pituitary secretes 2 hormones that are produced by the hypothalamus

Antidiuretic hormone ADH (or Vasopressin)	acts on kidney, increasing water retention and thus decreasing urine volume
Oxytocin	causes uterus to contract

 

Pancreas

• Produces enzymes released into small intestine
• Secretes 2 hormones
• glucagons and Insulin- both are produced in a cluster of cells called Islet of Langerhans
• Both target liver and muscles

Glucagon- stimulates liver to convert glycogen into glucose Increases the levels of glucose in the blood