Feedback loops (fluid and gas in diff flashcards)

Question 1

Draw a feedback loop when you are exercising

Answer 1

Stimulus
- Decrease in blood glucose due to exercise

Receptors
a) Alpha cells in pancreatic Islets
b) Chemoreceptors (peripheral adrenal gland)
c) Chemoreceptors (central hypothalamus)

Message
a) Signalling within Islets
b) CRH (Corticotropin-releasing hormone secreted from hypothalamus) stimulates ACTH (adrenocorticotropic hormone released from pituitary gland) -> Adrenal cortex
c) Sympathetic NS -> Adrenal medulla

Modulator
a) Alpha cells in Islets of Langerhans
b) Adrenal cortex
c) Adrenal medulla

Message
a) Glucagon
b) Cortisol
c) Adrenaline

Effector
-Body cells
-Liver

Response
-Body cells
-Glycogenolysis (glycogen -> glucose)
-Lipolysis (lipids -> glucose)
-Liver
-Glycogenolysis (glycogen -> glucose)
-Lipolysis (lipids -> glucose)
-Gluconeogenesis (proteins -> glucose)

Feedback
-Negative feedback loop
-Increase in blood glucose and a return to homeostasis

Question 2

Draw a feedback loop when you are eating/finished eating

Answer 2

Stimulus
- Increase in blood glucose due to eating

Receptors
a) Beta cells in the pancreatic Islets
b) Chemoreceptors

Message
- Signalling with Islets

Modulator
a) Beta cells in Islets of Langerhans

Message
a) Insulin

Effectors
-Body cells
-Liver
-Fat body cells

Response
-Body cells
-Absorb glucose
-Liver
-Glycogenesis (glucose -> glycogen)
-Lipogenesis (glucose -> lipids)
-Fat cells
-Lipogenesis (glucose -> lipids)

Feedback
-Negative feedback
-Decrease blood glucose and return to homeostasis

Question 3

Draw a feedback loop when CO2 levels are high

Answer 3

Stimulus
-Increased CO2 levels in blood, H+ increased (= decrease in pH; more acidic)
->Caused by exercise (increase cellular respiration)
->Decrease rate and depth of breathing

Receptors
-Chemoreceptors for CO2 in aorta, carotid artery and hypothalamus
-Chemoreceptors for pH in carotid artery and medulla oblongata

Message
-Nervous system / nerve impulses

Modulator
-Medulla oblongata

Message
-Autonomic nervous system

Effectors
-Diaphragm
-intercoastal muscles

Response
-Diaphragm + intercoastal muscles work to increase rate and depth of breathing
-CO2 decreases, H+ decrease and pH increases

Feedback
-Negative feedback
-CO2, H+ and pH returns to set point

Question 4

Draw a feedback loop on when you are cold

Answer 4

Stimulus:
-Decrease in body temperature below the set point (e.g. exposure to cold)

Receptor:
-Thermoreceptors in the skin and hypothalamus detect the drop in temperature

Message
-Nerve impulawa are sent from thermoreceptors to hypothalamus

Modulator:
-Hypothalamus compares temperature to the set point and initiates corrective action

Message:
-Nerve impulses are sent to effectors via the autonomic nervous system and motor neurons

Effector:
-Skeletal muscles
-Blood vessels in the skin (arterioles)
-Adrenal medulla
-Thyroid gland

Response:
-Skeletal muscles contract rapidly (shivering) → generates heat
-Arterioles vasoconstrict → less blood flow to skin → conserves heat
-Adrenal medulla secretes adrenaline and noradrenaline → increases cellular metabolism
-Thyroid gland releases thyroxine → raises metabolic rate over time → more heat produced

Feedback:
-Negative feedback
-The warming responses raise body temperature back to the set point
-Thermoreceptors detect this rise and reduce stimulation to the hypothalamus
-Heat gain mechanisms are reduced or turned off

Question 5

Draw a feedback loop on when you are hot

Answer 5

Stimulus:
-Increase in body temperature above the set point (e.g. from exercise or a hot environment)

Receptor:
-Thermoreceptors in the skin and hypothalamus detect the rise in temperature

Modulator:
-Hypothalamus processes the information and compares it to the set point

Message:
-Nerve impulses are sent from the hypothalamus to effectors via the autonomic nervous system

Effector:
-Sweat glands
-Blood vessels in the skin (arterioles)
-Body’s metabolism

Response:
-Sweat glands increase secretion → sweat evaporates → cools the skin
-Arterioles in skin vasodilate → more blood to the surface → heat lost by radiation/convection
-Metabolic rate may decrease slightly to reduce internal heat production

Feedback:
-Negative feedback
-The cooling responses reduce body temperature back to the set point
-This decrease is detected by the thermoreceptors, which reduce stimulation of the hypothalamus
-Heat loss mechanisms are turned off