Chapter 17 - Endocrine System Flashcards
Exocrine Glands
Nonhormonal substances with ducts (sweat, saliva)
Endocrine Glands
Produce hormones and lack ducts
Hormones
long-distance chemical signals; travel in blood or lymph
Autocrines
exert effects on same cells that secrete them
Paracrines
locally acting, affect cells other than those that secrete them
What Hormones do
- Alter plasma membrane permeability membrane potential by opening or closing ion channels
- Stimulate synthesis of proteins
- Activate or deactivate enzymes
- Induce secretory activity
- Stimulate mitosis
Water-Soluble Hormones
All amino acid–based hormones except thyroid hormone
• Act on plasma membrane receptors
• Via G protein second messengers
•Cannot enter cell
Lipid-Soluble Hormones
- steroid and thyroid hormones
* Enters cell to act on intracellular receptors that directly activate genes
Target Cells
Target cells must have specific receptors to which hormone binds, for example
Target cell activation depends on
- Blood levels of hormone
- Number of receptors on or in target cell
- Affinity of binding between receptor and hormone
Hormonal Up-Regulation
target cells form more receptors in response to low hormone
Hormonal Down-Regulation
target cells lose receptors in response to high hormone
3 Types of Activations
Humoral Stimulus - hormone release caused by altered levels of ion or nutrient, i.e. low Ca2+, Parathyroid releases PTH to increase Ca2+
Neural Stimulus - Hormone release due to neural input, i.e. Ap to Adrenal Medulla to release Epi and Norepi.
Hormonal Stimulus - Hormone released because of another hormone (tropic hormone) Hormone from Hypothalamus to anterior pituitary gland to release other hormone.
Posterior Pituitary Hormones
Oxytocin and Antidiuretic Hormone
Anterior Pituitary Hormones
Growth hormone, TSH, ACTH, FSH, LH, PRL
Roles of Oxytocin
stimulates uterine contraction
trigger for milk
neurotransmitter in brain
Roles of ADH
inhibits or prevents urine formation
targets kidney tubules to reabsorb water
inhibited by alcohol
Growth Hormone
Indirect Mechanism
stimulates adipose cells to break down stored fat,
fueling growth effects,
increases uptake of amino acids from the blood
enhances cellular proliferation
reduces apoptosis,
all promote the growth of target cells in the bones, muscles, nervous and immune systems
Direct Mechanism - fat and carbohydrate metabolism which fuels the processes
Thyroid Stimulating Hormone (TSH)
- Produced by thyrotropic cells of anterior pituitary
- Stimulates normal development and secretory activity of thyroid
- Release triggered by thyrotropin-releasing hormone from hypothalamus
- Inhibited by rising blood levels of thyroid hormones that act on pituitary and hypothalamus
Adrenocorticotropic Hormone (ACTH)
- Secreted by corticotropic cells of anterior pituitary
- Stimulates adrenal cortex to release corticosteroids
- Triggered by hypothalamic corticotropin-releasing hormone (CRH) in daily rhythm
Follicle Stimulating Hormone (FSH)
- Secreted by gonadotrophs of anterior pituitary
- FSH stimulates gamete production
- Triggered by gonadotropin-releasing hormone (GnRH) during and after puberty
Luteinizing Hormone (LH)
- Secreted by gonadotrophs of anterior pituitary
- LH promotes production of gonadal hormones
- Triggered by gonadotropin-releasing hormone (GnRH) during and after puberty
Prolactin (PRH)
- Regulation of PRL release controlled by prolactin-inhibiting hormone (PIH)
- Suckling stimulates PRL release and promotes continued milk production
- Hypersecretion causes inappropriate lactation, lack of menses, infertility in females, and impotence in males
Thyroid
Hormone: increase metabolic rate, heat production, regulation of tissue growth and development, maintenance of blood pressure.
Hyposecretion=myxedema, cretinism
Hypersecretion=graves disease
