introduction Flashcards
physiology
study of how the body functions
homeostasis
the ability to maintain relatively stable conditions in the internal environment
- if you are eating you are changing your eating levels
- if you stand up you are changing your blood pressure
- your body is constantly trying to stay in homeostasis
- cells can only survive within a narrow range of conditions
- body conditions must be maintained within with physiological limits
- organ systems function together to maintain homeostasis
what body conditions control the physiological limits
- pH - effects the shape of proteins
- temp - need to maintain homeostasis or will not create enough/too much proteins
- blood gases (CO2, O2)
- blood pressure - too high, your heart works to fast, wears out the heart faster. too low, heart isn’t pumping fast enough so cells die off
- intracellular + extracellular fluid volumes
- body weight
disease
failure to maintain homeostasis
what systems control homeostasis
nervous and/or endocrine systems control all other systems (control centres)
how does the nervous/endocrine systems act towards to
1) maintain homeostasis
2) permit departures from homeostasis in a controlled matter. e.g. pregnancy, having to create the skeleton and systems of the baby takes a toile on the womens body growth, freight
homeostasis regulation
change in internal environment must be detected or anticipated, you can prepare for the event thatll change your homeostasis
- the NS and/ or endocrine system responds, altering systems responsible for that condition
types of NS/endocrine responses
1) anticipatory responses
- e.g. respiratory rate at start of exercise which leads to proprioceptors (NS sensory receptor) signal movement before a change in internal condition occurs (gases in blood)
- learned or behavioural, its Winnipeg and its January its cold, you assume that its cold and you put on a jacket without looking at the weather.
2) feedback mechanisms
- most common
- mechanisms that respond to change in the system, their must be a change for this to happen.
- consists of set points, receptors, control areas, and effectors
- set points: range of values of a variable that doesn’t bring a response
- variable is monitored by receptors - info (input) fed back to control area which is either NS or endocrine gland - output (effectors) which are muscles or glands
what are the types of feedback mechanisms
types:
a) negative feedback
- most common to maintain homeostasis mechanism
- result of the output variable moves back toward the set point i.e. in opposite (negative) direction to the change that triggered the response (input).
- this is how your thermos stat works
e. g. body core temp (= variable): set point 36 to 37.8. temp if temp (e.g. 40)
b) positive feedback
example of negative feedback
1) hypothalamus thermostat cells (R) detect high temp (stimulus)
2) brain (NS) central area
3) effector =smooth muscle dilate the blood vessels of skin relax (causing dilation) + sweat glands secrete sweat
result of homeostatic regulation
result: core blood to skin surface and sweat evaporates, higher heat loss and decrease in temp
changes in set point
set point can change e.g. fever
hypertension- 90% don’t know how they are caused. your body tries to lower you blood pressure but cannot and sets the set point to a new blood pressure which is higher, creating hypertension. medication varies on finding your set point to bring it down.
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positive feedback
- less common - NOT homeostatic, in fact takes you out of homeostasis
- output intensifies the input
- e.g. childbirth - during labour to the mother
- uterine contractions signal the brain (hypothalamus and posterior pituitary gland ) releases oxytocin (hormone) this continues until the baby is born.
- oxytocin levels remain high after baby is born, to continue the uterine contractions to get the placenta out
- in the same directions
