Lecture 15 2/13/24 Flashcards
Which three mechanisms are required for homeostasis?
-receptor
-control center
-effector
What is the role of the receptor?
sensing component responsible for monitoring and responding to changes in internal/external environment
What is the role of the control center?
receive and process information from the receptor
What is the role of the effector?
responds to command of the control center to either oppose or enhance the stimulus
Which main systems are involved in coordinating the functions of body organs?
-nervous system
-endocrine system
What are the characteristics of the nervous system?
-ultra-fast, localized responses
-operates using electrical signals
-response based on frequency of impulses and number of nerve fibers
What are the general functions of the endocrine system?
-regulation of:
–extracellular fluid
–metabolism/energy balance
–biological clock
–mineral balance
–stress
–immune functions
-growth and development
-reproduction
Where does the endocrine system secrete hormones?
into the blood
What are hormones?
chemical messengers that affect the function of specifically receptive organs/tissues when transported to them via bodily fluids
What are the characteristics of hormones?
-produced in small amounts
-stimulatory or inhibitory
-control physiologic processes
-bathe all body cells
-responses to hormones are dose and time dependent
Why is endocrine disease systemic?
due to the hormones bathing all cells in the body
What is the main characteristic of the pituitary-dependent system of the hypothalamus?
hormone secretion stops when hypothalamus/pituitary are damaged/separated
What is the main characteristic of the pituitary-independent system of the hypothalamus?
hormone secretion does not stop with pituitary damage
What is the main characteristic of the transient endocrine system?
short duration
What are some examples of pituitary-independent regulation?
-regulation of glycemia
-regulation of calcium
-regulation of Na+ and K+
-regulation of digestive enzymes
What is the function of the transient endocrine system?
present only in the female to provide support for pregnancy, delivery, and onset of lactation
What is intracrine signaling?
hormone acts inside cell which produced it
What is autocrine signaling?
secreted hormone acts by binding to receptor on same cell from which it was released
What is paracrine signaling?
secreted hormone acts on target cells in the vicinity of the cell from which it was released
What is endocrine signaling?
secreted hormone acts by being distributed in the circulation to distant target cells
What is neuroendocrine signaling?
secreted hormone acts by being distributed in circulation to distant target cells or neurons
What are Leydig cells?
cells that produce testosterone
What is a neuroendocrine reflex?
a physical stimulus that causes a nervous signal, triggering the release of hormones from the brain into the blood
How do neurohormones differ from neurotransmitters?
-neurohormones are hormones synthesized in neurosecretory cells/neurons
-neurotransmitters are chemicals released by nerve endings into synaptic clefts without release into blood
What are examples of neurohormones?
-hypothalamic-releasing hormones
-hypothalamic-inhibiting hormones
-oxytocin
-ADH
What are the three chemical classifications of hormones?
-amino acid/fatty acid-derived
-steroid
-peptide/polypeptide
What are the characteristics of steroids/T3/T4?
-similar among species
-stable at room temp.
-plasma half-life of minutes to days
-synthesized and released
-hydrophobic/lipophilic
-oral administration
What are the characteristics of protein hormones?
-species differences
-labile
-plasma half-life of minutes
-synthesized and stored
-hydrophilic
-no oral administration
How do peptides and steroids differ in terms of presence in the plasma?
-peptides like to stay in the plasma
-steroids are easier to get out of the plasma
What leads to the majority of hormones being secreted in “pulses”?
-feedback mechanisms
-limited lifespan/half-life
What is a circadian rhythm?
one cycle per 24 hours
What is an infradian rhythm?
cycle that exceeds circadian rhythm; longer than 24 hrs but less than 1 yr
What is an ultradian rhythm?
many cycles within 24 hr period
Which type of rhythm do most hormones follow?
ultradian rhythm
Which factors impact hormone secretion?
-age
-sex
-disease
-surgery
-trauma
-anxiety
-drugs
-temp.
-photoperiod
What is a dose-dependent response?
hormones are only produced in response to a stimulus when the stimulus is at necessary concentration
What is a time-dependent response?
hormones are produced based on when a stimulus is received, and will decrease in concentration as time goes on
