Ch. 20 A: The Endocrine System

What are endocrine glands?

• glands without ducts (ductless)

• secrete hormones directing into the bloodstream

Describe specificity of hormones

• a hormone can only affect trager cells of organs that have receptors for that specific hormone

How is hormone secretion regulated?

• regulated by a self-adjusting mechanism called a feedback loop

positive feedback look

• pushes levels to extreme (or further away from the norm)

Negative feedback loop

• main one we see in hormone regulation!

• maintains appropriate level of hormones in blood

What is the hypothalumus?

• the major control center of the endocrine system

What 3 things does the hypothalamus do?

• 1. secretes regulatory hormones

• 2. produces oxytocin and ADH (antidiuretic hormone)

• 3. controls the stimulation of the adrenal gland medulla

What do regulatory hormones (secreted by hypothalamus) do?

• control release of anterior pituitary hormones: releasing and inhibiting hormones

Pituitary gland: where is it found, what is a major structure?

• houses in sella turcica of sphenoid bone

• divided into anterior and posterior lobes

• contains infundibulum

What is the infundibulum?

• connects hypothalamus to pituitary gland

Anterior pituitary gland

• also known as the adenophypophysis

• secretes many hormones

• highly vascular

The anterior pituitary produces tropic hormones. What are tropic hormones?

• hormones that act on other endocrine structures

What are the four tropic hormones?

“FLAT hormones”

• Follicle-stimulating Hormone (FSH)

• Luteinizing Hormone (LH)

• Adrenocorticotropic hormone (ACTH)

• Thyroid Stimulating Hormone (TSH)

Growth Hormone (GH)

promotes growth and development of tissue

Follicle Stimulating Hormone (FSH)

• acts on ovaries and testies

  • permits production of sperm and egg (gametes)

Luteinizing Hormone (LH)

• acts on ovaries and testes

  • stimulates production of sex hormones (estrogen and testosterone)

Thyroid Stimulating Hormone (TSH)

• acts on thyroid to secrete thyroid hormone which regulates metabolism

Adrenocorticotrophic Hormone (ACTH)

• acts on adrenal cortex, stimulating secretion of cortisol and other hormones

Prolactin (PRL)

• stimulates milk production in mammals

  • using right before birth and a little while after

Endorphins

• bodies natural pain killer

  • block pain receptors so brain can’t receive it

• morphine

• synthetic pain killer

Pituitary dwarfism

• hypor-secretion of GH during childhood

  • shorter in stature

Gigantism

• hyper-secretion of GH during childhood

  • still proportional —> longer arms = longer legs

Acromegaly

• hyper-secretion of GH during adult hood

  • inc. in mass/size in hands fingers, feet

What are the two hormones synthesized by hypothalamus, stored in posterior pituitary gland?

1. Antidiuretic hormone (ADH)/ vasopressin

2. Oxytocin

Antidiuretic hormone (ADH)/ vasopressin

• reduced fluid loss via urine

Oxytocin

• stimulates contraction of the uterus during child birth

pitocin

• synthetic oxytocin that increases the strength of uterine contraction (speeds up child birth)