Lecture 2: Homeostasis 1: Control Systems

Question 1

Regulated variables

Answer 1

1. 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

Question 2

how does regulation of variables occur?

input signal:
integrating center:
output signal:

Answer 2

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)

Question 3

A simple control system.all control systems have ______(#) components that are:

Answer 3

3 components

*figure 1.8

Question 3

2 negative feed back pathways for glucose

Answer 3

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

Question 4

glucotoxicity

Answer 4

too much glucose in the blood

Question 5

negative feedback arterial pressure

Answer 5

1. mean arterial pressure increases (stretches vessel)
2. baraorecoptors in aorta, carotid artery
3. baroreceptors send afferent signals via nerves to brainstem (away from sensor to brain)
4. brainstem (medulla is the integration center) processes increase in arterial pressure
5. efferent nerves leave the medulla to project to
6. the heart and blood vessels are the effector?
7. decrease heart rate (bradycardia) and dilate the blood vessels

Question 6

negative feedback produces a _______ response on a _______ _________

Answer 6

quick, regulated variable
*prevents sudden and severe changes in the body
*sends things in the opposite direction

Question 7

what are two examples of positive feedback?

Answer 7

lactation and child birth
*pitocin and oxytocin

• baby stops sucking (+ stops when original stimulus is no longer there)

Question 8

+ feedback childbirth
stim:
sensor:
integrating center:
efferent signal:
response:
return to ehance stem:
stops when:

Answer 8

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

Question 9

2 “P” phrases for positive feedback

Answer 9

for a PURPOSE
for a PARTICULAR PERIOD OF TIME

Question 10

what is an example of a feed forward mechanism? (3 examples)

Answer 10

info flows ahead
ex: cephalic phase of digestive
smell food, salivation increases for gastric secretions and motility to get started

2. anticipation of exercise
   - increased HR and respiration
3. anticipation of taking an exam:
   - sweating, increased HR, diarrhea (can be negative if too much)

Question 10

Homeostasis: Body temperature.

What organ systems are involved and what do they serve a purpose of?

Answer 10

Integ: heat loss
muscular: heat production
cardio: heat distribution
nervous: coordination of blood flow, heat production, and heat loss

Question 11

Homeostasis: Body Fluid Concentration

What organ systems are involved and what do they serve a purpose of?

Answer 11

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

Question 12

Homeostasis: Body Fluid Volume

What organ systems are involved and what do they serve a purpose of?

Answer 12

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

Question 13

Homeostasis: Waste product concentration

What organ systems are involved and what do they serve a purpose of?

Answer 13

urinary system: elimination of waste products from blood
cardio: transport of waste products to sites of excretion

Question 14

Homeostasis: Blood Pressure

What organ systems are involved and what do they serve a purpose of?

Answer 14

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

Question 15

3 causes of hypertension and affect on homeostasis

Answer 15

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

Question 16

what is circulatory shock?

Answer 16

1. blood vessels inadequately filled and blood cannot circulate normally
2. causes inadequate blood flow to meet needs of tissues
3. 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

Question 17

diabetes mellitus

Answer 17

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

Question 18

cancer

Answer 18

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)