The endocrine system Flashcards
What is the endocrine system composed of
-endocrine glands that secrete hormones
-lacks continuity unlike the rest of the body organ system
Who does the endocrine system work with?
-the nervous system and endocrine system both work together to control homeostasis
What are the chemical messengers released by the endocrine system
hormones that are produced by cells, tissues , or organs
Hormone
-means to excite, and regulate the physiological (metabolic) activity of cells
-circulating hormones release their effect in a target cell
-the onset of hormones effects and their length (half-life) differ between hormones
-the duration of a hormone varies from a fraction of a minute to a wee
Endocrine system: response time, pathway type, and duration time
response time: slower
pathway type: extracellular fluid ex: blood
duration time: longer
Nervous system: response time, pathway type, and duration time
response time: faster
pathway type: neurons
duration time: shorter
List 5 the major effects of some hormones
- aids in reproduction, gametogenesis, fertilization, and implantation
- growth and development
- mobilizing body defense against pathogens
- maintaining water and electrolyte balance
- regulates cell metabolism and energy balance
Endocrine glands
cells that secret hormones directly into the ECF (extracellular fluid) blood, lymph
List the endocrine glands
- pineal gland
- pituitary gland
- thyroid gland
- parathyroid gland
- thymus
- adrenal gland
- ovaries
- testes
- pancreas (endocrine and exocrine)
exocrine glands
use ducts to secrete non-hormonal substances onto a free surface, not endocrine in nature do not secrete hormones
List the exocrine glands
- salivary glands
- sebaceous glands
- sweat glands
- mammary glands
- Brunner glands
- liver ( the largest gland in the body)
- pancreas
List other structures that also contain endocrine tissue
- hypothalamus (neuroendocrine gland)
- atria of heart (upper chamber)
- kidney
- small intestine
- stomach
- placenta
- skin
- adipose tissue
Target cell, tissue, organ
cell, tissue, or organ responding to the hormone
paracrine signaling
-hormone only affects one or just a few different types of cells
-ex: somatostatin (inhibits the release of insulin) in pancreatic isle
- this is a localized effect
endocrine signaling
-hormones affect many different types of body cells
- ex: insulin
- this is an overall effect
chemistry of hormones
-the chemical nature of a hormone will determine its action on cells
amino acid based hormones
-receptors usually on the outside of cells
-amino acids are water soluble
-embedded within the plasma membrane (made of fats)
biogenic amines
a modification of the amino acid tyrosine
-based on 1 amino acid
- ex: thyroxine, epinephrine, norepinephrine
peptides
short chains of amino acids
-ex: OT (oxytocin) and ADH (anti-diuretic hormone)
proteins
long chains of amino acids
ex: insulin
steroids
-synthesized from cholesterol, has receptors on the inside of the cell
-these are lipid-soluble hormones made by the adrenal gland, ovaries, and testes
prostaglandins (PGs)
-biologically active lipids associated with nearly all cell membranes
-potent in very small amounts
- nicknamed local hormone (affect cyclic-AMP function)
-produce a variety of effects such as raising BP, pain, inflammation
List the mechanisms of hormone action (at the cellular level)
- changes plasma membrane permeability, membrane potential, and opening/closing of ion channels
- synthesis of enzymes
- activates or deactivates enzymes
- increases secretory activity
- increase in mitosis
Target specificity: hormones
-the ability of a target cell to respond to a hormone depends on the presence of specific receptors on the plasma membrane or within the cytoplasm to which the hormone can bond
What three things effect the hormone’s effect on the target cell?
- concentration of the hormone
- number of receptors on or in the target cell
- affinity between the hormone and the receptor
receptors
-they are not constant, they vary depending upon the type of cell
-are dynamic structures
up-regulation
- persistently low levels of hormones can cause its target to form additional receptors for that hormone
-can have greater potency even with the little amount there
down-regulation
-prolonged exposure to high hormone concentrations can decrease the number of receptors for that hormone
permissivness
-one hormone cannot exert its full effects without another hormone being present
ex: reproductive system hormones cause the development of the reproductive system, but you need thyroid hormone for the normal timely development, lack of will result in delay
synergism
-more than one hormone produces the same effects at the target cell and their combined effects are augmented
ex: glucagon and epinephrine both target the liver to release glucose. When together they release 150% more of what is released when they act alone
antagonism
-one hormone has the opposite effect of another hormone
ex: insulin and glucagon
-insulin lower blood glucose
-glucagon raises blood glucose
*made in pancreatic isle
secondary messenger systems
-used with water soluble amino acid based hormones cannot travel through to the plasma membrane of tissue cells and must exert their effects through intracellular second messengers, that are made when the hormone bind to or on the receptor
primary messenger
-the hormone therefor acts as this
5 steps in secondary messenger systems
- the hormone binds to the receptor in the plasma membrane
- the receptor activates the G-protein
- The G-protein activates special enzymes such as adenylate cyclase
- Adenylate cyclase converts ATP to cAMP
5.Cyclic AMP activates protein kinases that cause cellular changes
8cyclic AMP easily diffuses through the cell and acts as the second messenger
Direct gene activation system
-used with lipid soluble hormones
-lipid soluble hormones are chemically similar to plasma membrane and easily diffuse through target cell and bind to a receptor in cytoplasm or nucleus
-steroid hormones may activate genes within the nucleus of the target cell which cause synthesis of proteins that cause cellular changes
-this results in producing a structural or physiological effect
** steroid based hormones do not require a second messenger
Which amino acid based hormone does not stop outside the cell
thyroid hormone
-has iodine, and when it attaches to the plasma membrane it acts like a steroid based hormone and can penetrate the cell with the receptor located on the inside of the cell
stimuli
-result in endocrine glands manufacturing and releasing hormones
-the amount of hormones released depends on stimulus
How are most hormones controlled by?
-a negative feedback system
What are three ways a endocrine gland can be stimulated?
- hormonal stimuli
- humoral stimuli
- neural stimuli
hormonal stimuli
- a hormone stimulates an endocrine gland to release its hormones
- ex: thyroid stimulating hormone
- ex: adrenocorticotropic hormone
Thyroid stimulating hormone (TSH)
-a hormone made by the pituitary gland that causes the thyroid gland to release thyroid hormone
Adrenocorticotropic hormone (ACTH)
-made by the pituitary gland that causes the release of hormones from the adrenal gland
humoral stimuli
-changes in the concentration of chemicals
- ions or nutrients in the bloodstream stimulate an endocrine gland to release its hormones
- ex: when blood levels of glucose are high, this causes the release of insulin to lower levels
- ex: when blood levels of calcium are high (depleting bone tissue) this causes the release of calcitonin to lower levels
neural stimuli
-nerve impulses stimulate an endocrine gland to release its hormones
- ex: sympathetic nervous system causes the adrenal glands to release norepinephrine and epinephrine
- ex: the hypothalamus (neuroendocrine gland) causes the posterior pituitary gland to secrete oxytocin
ex: the hypothalamus causes the posterior pituitary to secrete anti-diuretic hormone
Pituitary gland (hypophysis)
-called the master gland
-located within the Sella turcica of sphenoid done
-pea sized
-separated into anterior and posterior
-both lobes structurally and functionally separate
-posterior pituitary glands attached to the hypothalamus by a stalk like structure called the infundibulum
Anterior lobe (adenohypophysis)
-contains glandular epithelial cells
-true endocrine glands because made of epithelial tissue
-no direct neural connection with the hypothalamus
-releasing and inhibiting hormones secreted by neurons in the hypothalamus travel via the hypophyseal portal system where they regulate the anterior pituitary hormones