intro Flashcards
What is the endocrine system
One of the control systems of the body. The other one is the nervous system
- includes the secretion of hormones from glands
Hormones are
chemical signals that affect the behavior of other glands or tissues
-Secreted in small amounts
Hormones influence…
- Metabolism of cells
- growth and development of body parts
- play a vital role in homeostasis
Do not actually initiate actions, but regulate them
-most present in blood at all times, but varying amounts, depending on body needs
they can produce general or localized effect
Names all the Endocrine glands
Pituitary glands hypothalamus pineal gland adrenal glands Pancreas overies testies thyroid parathyroid
Endocrine glands are
Ductless
- depend on blood and interstitial fluid for transport of their secretions, glands very vascular
- hormones secreted into blood cap.
Target cells are
cells stimulated by a particular hormone
-stimulated when the hormone binds to the receptor for that specific hormone
Topic Hormones
hormones that have other endocrine glands as target,
-act in beginning of the reaction stimulating another endo gland to release non-tropic hormone.
-Anterior pituitary mainly produces tropic hormones
EX: Anterior piutiarty stimulates Thyroid stimulating hormone (Thyrotropin),Adrenocorticotropic Hormone, Follicle Stimulating Hormone, Luteinising Hormone
Non-tropic Hormones
Hormones that directly stimulate target cells to induce effect
-usally last piece of larger process and chain of hormone secretions
EX: Glucocorticoids: secreted from the adrenal glands and released directly into the blood stream (cortisol and cortisone)
Antidiuretic Hormone (posterior pituitary)
Oxytocin (posterior pituitary)
Testosterone
Oestrogen
Epinephrine and norepinephrine (adrenal glands)
4 Chemical Categories of Hormones
- Steroids
- Eicosanoids
- Proteins and peptides
- Amines and amino acids
Bonus:
can also be cat. as Lipid soluble or water soluble
Lipid soluble
INSOLUBLE in water
- steroids and T3, T4 amines
(have benzene ring)
- Easily diffuse across the target cell membrane and binds to receptor in cytoplasm
-carried in the blood attached to proteins
-excreated slowly from body
not denatured in digestive system, can give orally
Water Soluble
- amino acids, proteins, peptides
- binds to receptor protein on plasma membrane and activates second messenger system
- dissolve in plasma
- given by injections because denatured in stomach
Steroids
- derived from cholesterol
- Lipid soluble hormones
- activation leads to the production of cellular enzyme
- EX: cortisol, aldosterone, testosterone, oestradiol, (steroid hormones- adrenal cortex steroids)
Eicosanoids
-derived from 20 carbon polyunsaturated fatty acids
-water soluble
-acts locally
- important for blood clotting, regulation of smooth muscle contraction, neurotransmitters release and action, defence against injury and infection, in reproductive system
EX: prostaglandins, prostacyclins, thromboxanes and leukotrienes
Proteins (long) and peptides ( short)
Consists of chains of Amino acids
- water-soluble- carried dissolved in plasma
- Binds to cell membrane activating second messenger system ( cAMP, Ca+)
- the second messenger causes cellular changes to the formation of an end product which leaves the cell, for which hormone is credited
- Excreted quicker than lipid soluble, because dissolved
EX: most of the anterior pituitary hormones are all proteins (TSH, GH, FSH, LH); insulin and glucagon, calcitonin, parathyroid hormone
Posterior pituitary hormones are peptides (ADH, Oxy); and prolactin, adrenocorticotropic hormone(ant pit)
Amines and amino acids
- derived from amino acids
- simplest hormone
- water soluble
EX: Epinephrine, norepinephrine, Thyroxine (T4), Triodothyronine (T3) (end in “ine”)
Hormone secretion control
types of input to endocrine cells
- changes in plasma concentration of mineral ions (glucose and amino acids – insulin)
- neurotransmitters released from neurons impinging on the endocrine cell (epinephrine)
- another hormone acting on the endocrine cell (FSH, TSH)
secreted in short bursts, so plasma concentrations of hormones may fluctuate rapidly
Sometimes secretions influenced by more than one input EX: insulin influenced by BGL, Symp and parasymp
What is negative feedback
when a stimulus causes a body response, in order the body to correct the initial stimulus – it reduces the difference between a variable and its set point
- result is that the activity of the hormone is maintained within normal physiological limits and homeostasis is ensured
- important for ions or molecules in the body to be kept within a normal range to maintain homeostasis
levels negative feedback operates
many levels:
- on hypothalamus
- on pituitary
- and/or on endocrine cell itself
What is positive feedback
when the stimulus continues to bring about an effect that ever increases in intensity – it increases the difference between a variable, and its set point
-lesser of the two, positive feedback also exists in a therapeutic manner to maintain homeostasis
EX: Oxytocin stimulates uterine contractions. Uterine contractions stimulate oxytocin release
