Lecture 2: Homeostasis 1: Control Systems Flashcards
Regulated variables
- kept in normal range by control mechanisms
a. keeps the variable’s value near a set-point value
b. usually this value is optimal for physiological processes
c. in disease states, the set point can be shifted
how does regulation of variables occur?
input signal:
integrating center:
output signal:
locally and by reflexes
input signal: variable detected by a sensor (local control and reflex)
integrating center: processes input signal against set-point (only reflex)
output signal: from integrating center to adjust the variable (both)
A simple control system.all control systems have ______(#) components that are:
3 components
*figure 1.8
2 negative feed back pathways for glucose
STIM: blood glucose levels rise
1. beta cells in pancreas release insulin into blood
2. liver takes up glucose and stores it as glycogen
3. blood glucose levels decline = homeostasis (90mg/100mL)
GLYCONEOGENSIS
STIM: blood glucose levels fall
1. alpha cells in pancreas release glucagon
2. liver breaks down glycogen and releases glucose into the blood
3. blood glucose levels rise = homeostasis
GLYCOGENOLYSIS
glucotoxicity
too much glucose in the blood
negative feedback arterial pressure
- mean arterial pressure increases (stretches vessel)
- baraorecoptors in aorta, carotid artery
- baroreceptors send afferent signals via nerves to brainstem (away from sensor to brain)
- brainstem (medulla is the integration center) processes increase in arterial pressure
- efferent nerves leave the medulla to project to
- the heart and blood vessels are the effector?
- decrease heart rate (bradycardia) and dilate the blood vessels
negative feedback produces a _______ response on a _______ _________
quick, regulated variable
*prevents sudden and severe changes in the body
*sends things in the opposite direction
what are two examples of positive feedback?
lactation and child birth
*pitocin and oxytocin
- baby stops sucking (+ stops when original stimulus is no longer there)
+ feedback childbirth
stim:
sensor:
integrating center:
efferent signal:
response:
return to ehance stem:
stops when:
stim: baby pushing cervix
sensor: cervix stretches to activate brain signal
integrating center: brain
efferent signal: oxytocin released from pituitary
response: oxytocin causes uterus to contract to promote birth
return to enhance stem: contraction pushes toward cervix and birth canal
stops when: baby is born
2 “P” phrases for positive feedback
for a PURPOSE
for a PARTICULAR PERIOD OF TIME
what is an example of a feed forward mechanism? (3 examples)
info flows ahead
ex: cephalic phase of digestive
smell food, salivation increases for gastric secretions and motility to get started
- anticipation of exercise
- increased HR and respiration - anticipation of taking an exam:
- sweating, increased HR, diarrhea (can be negative if too much)
Homeostasis: Body temperature.
What organ systems are involved and what do they serve a purpose of?
Integ: heat loss
muscular: heat production
cardio: heat distribution
nervous: coordination of blood flow, heat production, and heat loss
Homeostasis: Body Fluid Concentration
What organ systems are involved and what do they serve a purpose of?
Nutrient Concentration:
- digestive: nutrient absorption, storage and release
- cardio: nutrient distribution
urinary: control of nutrient loss in urine
Oxygen, Carbon Dioxide:
- resp: absorption of oxygen and CO2
- cardio: internal transport of oxygen and carbon dioxide
Homeostasis: Body Fluid Volume
What organ systems are involved and what do they serve a purpose of?
urinary: elimination or conservation of water from blood
digestive: absorption of water; loss of water in feces
integumentary: loss of water through perspiration
cardio: distribution of water
Homeostasis: Waste product concentration
What organ systems are involved and what do they serve a purpose of?
urinary system: elimination of waste products from blood
cardio: transport of waste products to sites of excretion
Homeostasis: Blood Pressure
What organ systems are involved and what do they serve a purpose of?
cardio: pressure generated by heart moves blood through the vessels
nervous & endocrine: adjustments in heart rate and blood vessel diameter can raise or lower BP
3 causes of hypertension and affect on homeostasis
chronic stress: constriction of blood vessels
kidney damage: retaining excess blood volume
excess dietary salt: expansion of blood volume
affect: blood pressure set point for homeostasis is now higher and body will defend new, higher pressure
what is circulatory shock?
- blood vessels inadequately filled and blood cannot circulate normally
- causes inadequate blood flow to meet needs of tissues
- baroreflex senses decrease in pressure and constricts vessels to worsen flow
ex: hemorrhage, body constricts vessels to stop bleeding, but this is making it worse
diabetes mellitus
result of: homeostatic imbalance
Type 1: damage to pancreas, reduction in insulin release
Type 2: most common insulin cannot effectively store blood glucose in muscle (insulin is there, it just cannot be stored
cancer
all types are homeostatic imbalance
1. inappropriate cell division or growth of tumors
tumors physically impair normal processes (Ex: press on brain)
2. tumors cause inappropriate changes to processes (ex: liver dysfunction)
