chapter 18 endocrine system

Exocrine glands

Secretions go to ducts that carry into body cavities, lumens of organs, or body surfaces (ex: sweat mucus digestive juices saliva)

Endocrine glands

Secretions go to the blood ex: hormones

Hormones travel through

The circulatory system and bind receptors on target cells

What is a receptor

Binding site on a target cell for hormones

Hormones can act

Locally or at a distance

Local hormones

Paracrines (act on neighboring cells) autocrines (act on the cell that secreted them)

Circulating hormones (endocrine)

Enter bloodstream and target a distant cell or organ

Amino acid derivatives

Small molecules, similar structure to amino acids ex: epinephrine and thyroid hormones

Peptide hormones

Chains of amino acids ex: oxytocin, adh, lh, and fsh

Lipid derivatives

Corticosteroids

Lipid soluble hormones

Steroid and thyroid hormones.

Cross lipid bilaterally of target cell and bind receptor inside target cell

Effect: turn genes on or off within the nucleus

Water soluble hormones

Amino acid derivatives, peptide hormones

Cannot pass lipid bilayer, bind to receptor proteins on extracellular surface

Effect: receptor binding stimulates release of enzyme inside cell that triggers hormone responses

Amplification (water soluble hormones)

Thousands of second messengers may appear amplifying effect on target cell

Neural stimuli

Something from the nervous system is stimulating hormone release

Humoral stimuli

Refers to blood, triggers the release of pth

Other hormones

One hormone can trigger the release of another

Pituitary gland

Lies within the sella turcica of sphenoid bone

Anterior lobe (adenohypophysis) posterior lobe (neurohpyphysis)

Hypothalamus

Located superior to the pituitary gland and it is connected by the infundibulum

Integrating center between nervous and endocrine system

Contains capillaries to carry hormones to the pituitary

Hypothalamus secretes

Regulatory hormones that control secretions of the anterior pituitary

Hypothalamus produces hormones and them

Along axons to posterior pituitary

Hypothalamus controls

Output to the adrenal medulla leading to secretion of epinephrine

Releasing hormones (hypothalamus)

Stimulate synthesis and secretion of anterior pituitary hormones

GH RH

Inhibiting hormones

Prevents synthesis and secretion of anterior pituitary hormones

GH IH

Thyroid stimulating hormone (TSH)

Acts on thyroid gland to regulate production and release of thyroid hormones

Controlled by TRH of hypothalamus

Adrenocorticotropic hormone (ACTH)

Acts on adrenal cortex to regulate production the glucocorticoids

Controlled by CRH of hypothalamus

Follicle stimulating hormone (FSH)

Female: promotes follicle development

Male: sperm production in tested

Co