module 13 first half: endocrinology Flashcards
(39 cards)
what is homeostasis and how is it maintained in the body?
The process by which conditions inside the body are maintained at constant levels
- it’s maintained by the nervous system and the endocrine system
what are the functions of the endocrine system
- maintenance of the internal environment (body temp, body fluid, volume, osmolality)
- adaptation to stress
- control of growth and metabolism
- control of reproduction
differences between endocrine system and nervous system actions
endocrine system indirectly affects many organs at a distance by secreting hormones into the blood
- slower to take effect
- last longer and are more widespread within the body
nervous system has direct contact over organs through synapse
- faster to take effect
glands - what is the endocrine gland, how does it work
a group of specialized cells that synthesize, store, and release a special chemical (hormones) into the blood
- hormone goes into the blood stream and circulates to specific target cells that have receptors for the hormone
- hormone will have it’s effect and can either stimulate or inhibit the activity of the cell
list all the glands in the body
- hypothalamus
- pituitary glands
- thyroid gland
- adrenal glands
- pancreas
- gonads (ovaries/testes)
three categories of hormones
- hormones derived from the amino acid tyrosine (thyroxine, triiodothyronine)
- secreted from the thyroid gland - hormones derived from proteins
- calcitonin, parathyroid hormone, pituitary and pancreatic hormones, and most releasing/inhibiting hormones from the hypothalamus - steroid hormones
- cortisol, aldosterone, estrogen, progesterone, testosterone, all derived from cholesterol
protein hormones - hydrophilic/hydrophobic?, receptor location?, movement through the blood?
protein hormones are hydrophilic
- they can circulate freely in the blood
- they cannot diffuse through the cell membrane
- the receptor is located on the cell membrane
steroid and thyroid hormones - hydrophilic/hydrophobic?, receptor location?, movement through blood?
steroid and thyroid hormones are hydrophobic
- they require a protein carrier to help them circulate in the blood
- they can diffuse through the cell membrane
- the receptor is located inside the target cell
hormones - characteristic of how they are secreted in the blood and what their special effects do
hormones are secreted into the blood in “pulses”
- by a specific stimulus and in amounts that vary with the strength of the stimulus
- their special effects regulate preexisting reactions
what is a hormone receptor? what triggers the response from the cell?
structure in or on a cell that interacts with a chemical (the hormone) in a particular way
- type of hormone determines where the receptor is located
- interaction between receptor and hormone triggers a response from the cell
explain the process of receptors for hydrophobic hormones
- hormone first released by its carrier protein
- receptors are located in the cytoplasm or on the nucleus
- once hormone is inside the cell, it will bind with the receptor
- this new hormone/receptor complex binds to the DNA within the nucleus to alter activities of the cell:
- increase/decrease transcription of specific genes (altering production of downstream proteins)
explain the process of receptors for hydrophilic hormones
- hormone must alter activity of the cell from the “outside”
- receptors are located on the cell membrane
- when hormone attaches to the receptor, it initiates a sequence of chemical reactions that will alter cell activity
what are the 3 ways the receptor in a hydrophilic hormone can affect the cell
- second messenger system
- tyrosine kinase
- G - proteins
explain the process of the second messenger system
- Hormone receptor complex causes a G - protein on the inside of the cell produces a second messenger
- most widely studies second messenger is called cyclic adenosine monophosphate (cAMP) - Second messenger is released into the cytoplasm and rapidly alters proteins present inside the cell
- These altered proteins trigger a sequence of reactions inside the cell
- leads to a variety of intracellular responses (such as protein release)
explain the process of tyrosine kinase
- Hormone receptor complex activates tyrosine kinase on the inside surface of the membrane
- Intracellular tyrosine kinase alters existing proteins that will alter the activity of the cell
explain the process of ion channels
- Hormone receptor complex activates a G - protein that lies within the cell membrane
- This G- protein can open adjacent ion channels
- If the ion is Ca++, it acts as a second messenger, altering existing proteins once it diffuses into the cell
what happens after hormones have had their effects on their target tissue
hormones are broken down by different systems in the body
1. Metabolic destruction
- in the blood or by tissues (mainly liver and kidneys)
2. Excretion by the liver
- into the bile
3. Excretion by the kidneys
- into the urine
how is the secretion of hormones controlled
through negative feedback loops
where is the hypothalamus located?
what type of information from the body does it receive?
what does the hypothalamus regulate in the body (homeostatic & behavioural)
located at the base of the brain, above the pituitary gland and below the thalamus
- it receives informations from all over the body
- composed of regions made up of nerve cell bodies (nuclei), several of these nuclei control the release of hormones from the pituitary gland
involved with the body’s homeostatic mechanisms, including regulation of:
- body temperature, water balance, energy production
involved in regulating the behavioural drives of:
- thirst
- hunger
- sexual behaviour
to perform these actions, the hypothalamus receives lots of information from all around the body including:
- metabolic, hormonal, temperature, and neural information
list all the hormones the hypothalamus secretes and what they cause
- prolactin inhibiting hormone (PIH)
- prolactin releasing hormone (PRH)
- thyrotropin releasing hormone (TRH)
- corticotropin releasing hormone (CRH)
- growth hormone releasing hormone (GHRH)
- growth hormone inhibiting hormone (GHIH)
- gonadotropin releasing hormone (GnRH)
these are referred to as inhibiting/releasing hormones because they cause the release or inhibition of a hormone from the anterior pituitary gland
explain the pituitary gland structure
anterior pituitary: what it’s made of, its function, how its regulated, how the hypothalamus and pituitary work together
the pituitary gland is divided into two regions:
- anterior pituitary
- posterior pituitary
anterior pituitary is made up of endocrine tissue
- these cells secrete pituitary hormones directly into the blood
- regulated by the hypothalamus through a special circulatory system, the hypothalamic-hypophyseal portal system
the hypothalamus communicates with the anterior pituitary by secreting the releasing or inhibiting hormones into the portal system
- these hormones travel to the anterior pituitary to either stimulate or inhibit the release of pituitary hormones
what is the posterior pituitary made of, it’s function, hormones released (what is the tract called)
the posterior pituitary develops from neural tissue at the base of the brain
- it contains axons and nerve terminals of neurons whose cell bodies lie in the hypothalamus
- this tract is referred to as the hypothalamic hypophyseal tract
these neurons produce neurohormones (ADH and oxytocin) in the hypothalamus that are secreted into the blood in response to action potentials
anterior pituitary hormones result of thyrotropin releasing hormone (TRH)
causes the release of thyroid stimulating hormone (TSH)
- TSH then stimulates the thyroid gland to secrete two thyroid hormones
- triiodothyronine (T3)
- thyroxine (T4)
anterior pituitary hormones result of corticotropin releasing hormone (CRH)
stimulates the release of adrenocorticotropic hormone (ACTH) from the anterior pituitary
- ACTH then stimulates the adrenal glands to secrete mainly cortisol
- ACTH has a minor affect in the secretion of adrenal androgens and aldosterone as well
