Homeostasis

Question 1

define homeostasis

Answer 1

the maintenance of a stable internal environment, essential for healthy function of body cells/tissues & organs

Question 2

give 4 examples of things controlled by homeostasis

Answer 2

1 blood pressure
2 blood glucose
3 ion balance
4 water balance

Question 3

which two systems are integrated to allow communication w/in the body to maintain homeostasis & adapt to changes in circumstances

Answer 3

endocrine and nervous systems

Question 4

describe the components of the feedback loop

Answer 4

1 imbalance (stimulus)
2 receptor ( to step 3 via AFFERENT PATHWAY)
3 control centre in brain (to step 4 via EFFERENT PATHWAY)
4 effector (target organ)
5 response by homeostasis

Question 5

what is the function of the comparator?

Answer 5

compares message from sensor to the set level (correct value). if too high/low, target organs are targetted to bring back to physiological range

Question 6

afferent pathway?

Answer 6

signal going to comparator

Question 7

efferent pathway?

Answer 7

output signal

Question 8

describe negative feedback loops. give examples

Answer 8

change occurs in opposite direction to the stimulus
- reduces output of system
- decrease in function
eg restores bp, return plasma osmolality, temp regulation

Question 9

describe how blood pressure is controlled when it has gone too low

Answer 9

• BARORECEPTORS register low bp
• SINUS nerve firing is reduced (baroreceptor reflex)
• MEDULLARY CARDIOVASCULAR CENTRES (comparator) causes arterioles to constrict & HR inc

Question 10

describe positive feedback loops. give examples

Answer 10

enhances the stimulus O causes reaction to occur at faster rate
eg secretion of oxytocin during childbirth

Question 11

describe how oxytocin is secreted during childbirth`

Answer 11

1 uterus is more excitable 
2 causes uterine contractions
3 fetus presses on cervix
4 AFFERENT signal to hypothalamus 
5 oxytocin secreted by POST PIT
6 causes MORE UTERINE CONTRACTIONS etc etc 

7 birth terminates +ve feedback