L2/3 Homeostasis - feedback/forward control

Question 1

homeostasis

Answer 1

maintain internal stability, with coordinated responses to stimuli

Question 2

negative feedback control and advantages/disadvantages?

Answer 2

control action DECREASES the effect of disturbance
-A: automatic compensation for disturbance
-A: holds system constant in changing conditions
-D: energetically costly and must be in “bad spot” first to be fixed. (must suffer for a sec to get desired result)

Question 3

sensors

Answer 3

report values of controlled variable

Question 4

integrator

Answer 4

(mostly brain) uses sensor signals and previous knowledge to “command’

Question 5

effector

Answer 5

answers to integrator and performs tasks

Question 6

T or F, controlled variables can change value?

Answer 6

true

Question 7

does afferent signal go in or out?

Answer 7

in (karen complaint = sensor signal)

Question 8

does efferent signal go in or out?

Answer 8

out exit (manager orders more tp stocked = integrator orders)

Question 9

positive feedback control and A/D’s?

Answer 9

control action INCREASES the effect of any disturbance
-A: drives system to an extreme
check lec cap 4:55pm

Question 10

positive feedback control example: childbirth

Answer 10

-baby pushes on cervix

-stretching (pushing on) cervix causes nerve impulses to be sent to brain

-brain stimulates pituitary to release oxytocin

-oxytocin causes uterus to contract

Question 11

feed-forward control? A/D’s

Answer 11

control action is independent of output (anticipatory action, like salivating when smell food)

-A: speedy, can minimize or eliminate disturbance
-D: needs good prediction, mistakes can be costly

*kind of skips everything (sensor, integrator, effector)

Question 12

what physiological factors are maintained by homeostasis

Answer 12

[nutrients]
[O2 and CO2]
[waste products]
pH
[water and electrolytes]
temp
volume and pressure
defense against foreign invader

Question 13

intrinsic systems

Answer 13

“built in” to an organ or tissue
-increased CO2 production by exercising leads to relaxation of smooth muscles and dilation of blood vessels

Question 14

extrinsic systems

Answer 14

contained outside of an organ or system, permitting coordinated regulation of several organs
-high blood glucose detected by endocrine system, which exerts hormonal control (insulin)

Question 15

direct intercellular communications

Answer 15

Small molecules and ions
-gap junctions: “channels”
-transient direct linkup of cell’s surface markers: external puzzle piece channel

Question 16

indirect intercellular communication via extracellular chemical messengers

Answer 16

paracrine secretions: “shooting in the dark”

neurotransmitter secretion: “neuron shoots neurotransmitter”
-neurotransmitter: NS signaling acts via electrical signals to control rapid response

Question 17

how do cells talk to eachother?

Answer 17

hormones and neurohormones = endocrine signaling
secrete stuff into blood for distant target cells