Final Exam - Endocrine System (parts 1, 2, and 3) Flashcards
What are the characteristics of human hormones?
- generally secreted by endocrine glands directly into circulatory system
- trigger a change in another organ’s activities
- affect only certain target cells that have the specific receptor of the hormone
What are the two main classes of hormones?
- amino acid-based hormones
- steroids
How do hormones act?
based on chemical nature and receptor location
What are the characteristics of water-soluble hormones?
- act on plasma membrane receptors
- act via G protein second messengers
- cannot enter cell
What are the characteristics of lipid-soluble hormones?
- act on intracellular receptors that directly activate genes
- can enter cell
What are the characteristics of hormone levels in the blood?
- controlled by negative feedback systems
- levels vary only within narrow, desirable ranges
What are the three types of endocrine gland stimuli?
- humoral stimuli: blood
- neural stimuli: nerve fibers
- hormonal stimuli: other hormones
How does humoral stimuli work?
changing blood levels of ions and nutrients directly stimulate secretion of hormones
How does neural stimuli work?
nerve fibers stimulate hormone release
How does hormonal stimuli work?
hormones stimulate other endocrine organs to release their hormones
What are the characteristics of nervous system modulation?
- nervous system can make adjustments to hormone levels when needed by stimulating or inhibiting endocrine glands
- can override normal endocrine controls in extreme circumstances
What three factors impact target cell activation?
- blood levels of hormone
- relative number of receptors on/in target cell
- affinity of binding between receptor and hormone
What is up-regulation, in terms of target cell receptors?
target cells form more receptors in response to low hormone levels
What is down-regulation, in terms of target cell receptors?
targets cells lose receptors in response to high hormone levels, which desensitizes the target cells
When does the nervous system tend to act vs when does the endocrine system tend to act?
- nervous system acts when an immediate or short-term response is needed
- endocrine system acts when the response can last over a longer time period
What are the characteristics of the hypothalamus?
- portion of the brain that contains a number of small nuclei with a variety of functions
- links the nervous system to the endocrine system via the pituitary gland
- connected to pituitary gland via infundibulum
What are the two lobes of the pituitary gland?
- posterior pituitary
- anterior pituitary
What is the posterior pituitary?
composed of neural tissue that secretes neurohormones
What is the anterior pituitary?
consists of glandular tissue
What are the characteristics of the pituitary-hypothalamic relationship for the posterior pituitary?
- posterior lobe is neural tissue derived from a downgrowth of the brain
- maintains neural connection to hypothalamus via hypothalamic-hypophyseal tract
- hypothalamus secretes oxytocin and ADH, which are stored in axon terminals in posterior pituitary
What are the characteristics of the pituitary-hypothalamic relationship for the anterior pituitary?
- anterior lobe is glandular
- vascular connection to the hypothalamus via hypophyseal portal system
- hypothalamus secretes releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion
What are the characteristics of oxytocin?
- strong stimulant of uterine contractions
- acts as hormonal trigger for milk ejection
- neurotransmitter in brain
- positive feedback
What are the characteristics of ADH?
- hypothalamus contains osmoreceptors that monitor solute conc.
- if solute conc. is too high, posterior pituitary secretes ADH
- targets nephrons to reabsorb more water
- inhibited by alcohol and diuretics
What are the anterior pituitary hormones?
- growth hormone
- thyroid-stimulating hormone (tropic)
- adrenocorticotropic hormone (tropic)
- follicle-stimulating hormone (tropic)
- luteinizing hormone tropic)
- prolactin
