Lecture 1: Homeostasis Flashcards
physiology definitions (2)
-study of mechanical, physical and biochemical functions of living organisms
-study of life: how cells, tissues, organs and whole organisms function
how does physiology differ from anatomy
-anatomy focuses on structure
-physiology emphases purpose (why) and mechanism (how)
functional organization of body
chemicals –> cells –> tissues –> organs –> organ systems –> organism
3 main functions of anatomical/physiological systems
-facilitate survival of the individual in its environment
-facilitate survival of species
-coordinate functioning of the individual’s anatomic/physiological systems
homeostasis definition
ability to maintain a relatively stable internal environment in an ever-changing outside world including regulating
examples of homeostasis (7)
-concentration of nutrient molecules like glucose
-concentration of oxygen and carbon dioxide
-concentration of waste products like urea
-pH
-concentration of water, salt, and other electrolytes
-volume and pressure
-temperature
does homeostasis always strive for the same internal conditions (setpoints) in a given organism? why?
no, because there are situations where setpoints will shift (i.e. puberty, topor/hibernation, fever)
daily torpor definition
when small animals lower their temperature during inactive periods to conserve energy
how do hummingbirds survive cold nights with daily torpor
-lower body temperature and metabolism by dropping into an energy-saving state of inactivity
-lose body mass overnight
fever definition
rise in body temperature caused by pyrogens
2 types of pyrogens
-exogenous
-endogenous
endogenous pyrogens
produced by foreign substances like bacteria or viruses
exogenous pyrogens
produced by immune cells in response to infection
how do pyrogens induce fever
cause a rise in setpoint for metabolic heat production
what somatic responses are induced when setpoint of thermoregulatory control system is above body temperature
shivering and vasoconstriction are activated
in order to maintain homeostasis, control systems must be able to (3)
-detect deviations from normal in internal environment that need to be held within narrow limits
-integrate this info with other relevant info
-make appropriate judgements in order to restore factor to its desired value
2 types of control systems
-positive feedback
-negative feedback
majority of responses are what kind of feedback system
negative
negative feedback system: main strategies/goals
-maintain stability by defending set points
-oppose initial change
negative feedback example: temperature regulation
-sensors: skin thermoreceptors sense change in temperature
-send info to hypothalamus which integrates info and maintains set point
-relays info to effectors (vasodilation, sweating and panting if core temperature is above set point; vasoconstriction and shivering if core temperature is below set point)
are systems limited in how they respond?
yes
3 main components of negative feedback system
-sensor
-integrator
-effector
sensor function
monitor magnitude of a controlled variable and relate it to integrating center
integrator aka
control center
integrator/control center function
compare sensor’s input with a set point
example of a control center
hypothalamus
effector function
receive info from integrating center and respond accordingly
homeostasis/negative feedback systems: clinical correlations (3)
-fever
-heat stroke
-addison’s disease and secondary adrenal insufficiency
addison’s disease aka
primary hypoadrenocorticism
addison’s disease definition
deficient production of mineralocorticoids/cortisol and glucocorticoids from adrenal cortex
causes of addison’s disease (4)
-primary hypoadrenocorticism (autoimmune)
-adrenocorticotropic hormone (ACTH)
-metastatic turmors to HPA axis
-infections to HPA axis
normal production of cortisol process
-hypothalamus releases CRH (corticotropin releasing hormone) from anterior pituitary
-directs anterior pituitary to release adrenocorticotropic hormone (ACTH)
-ACTH stimulates adrenal cortex to produce cortisol
addison’s disease: cause
-non functioning adrenal cortex
addison’s disease: effects
-no cortisol
-increased CRH
-increased ACTH
secondary adrenal deficiency: cause
non functioning anterior pituitary
secondary adrenal deficiency: effects
-low cortisol
-high CRH
-low ACTH
2 examples of positive feedback systems
-ovulation
-parturition
when is ovulation a positive feedback system
shortly before ovulation (negative feedback most of the time)
parturition definition
removing fetus from uterus/action of giving birth
parturition: positive feedback example
-uterine contractions –> fetus pushes against cervix –> neuroendocrine reflex stimulates oxytocin release –> oxytocin acts upon uterus to continue contractions until fetus leaves birth canal –> oxytocin release stops
normal production of estrogen process
-hypothalamus releases GnRH (gonadotropin releasing hormone) which signals anterior pituitary to release FSH and LH to produce estrogen
ovulation: positive feedback example
production of estrogen during ovulation stimulates additional release of FSH and LH from anterior pituitary to increase estrogen production
