A&P Homeostasis Feedback Loops Flashcards

Homeostasis

the tendency of an organism or cell to regulate its internal environment and maintain equilibrium, usually by a system of feedback controls, so as to stabilize health and functioning

Afferent Neurons/Pathway

means the signal is traveling toward the control center

Efferent Neurons/Pathway

means the signal is moving away from the control center.

Negative Feedback

• Almost all homeostatic control mechanisms are _________ feedback mechanisms.

• These mechanisms change the variable back to its normal range

• Inhibit/Reduce the stimulus

• Oppose change

• Keep variables from straying too far outside of their normal ranges

• Responsible for maintaining a constant internal environment

Positive Feedback

• Exact opposite of a _________ feedback mechanism

• Stimulate the original stimulus

• Amplify or reinforce the change that is occurring

• Continues to deviate from the normal range

Blood Sugar

Type: Negative Feedback

Purpose: Maintain blood glucose within a healthy range for energy or prevent excessive glucose buildup in the blood.
Normal Range: 70–110 mg/dL of blood glucose

Stimulus: Blood Sugar (Low)

A drop in blood glucose levels, such as after fasting or intense exercise.

Sensor: Blood Sugar (Low)

Alpha cells in the pancreas detect the decrease in glucose concentration.

Control Center: Blood Sugar (Low)

The pancreas processes this information and releases glucagon.

Effector: Blood Sugar (Low)

The liver is the main _______; it converts stored glycogen into glucose and releases it into the bloodstream.

Response: Blood Sugar (Low)

Blood glucose levels rise back to the normal range.

Disease/Condition: Blood Sugar (Low)

Hypoglycemia can occur from excess insulin, fasting, starvation or endocrine disorders. Organ failure and brain dysfunction.

Stimulus: Blood Sugar (High)

A rise in blood glucose levels after eating.

Sensor: Blood Sugar (High)

Beta cells in the pancreas detect the increase in blood sugar.

Control Center: Blood Sugar (High)

The pancreas releases insulin to lower glucose levels.

Effector: Blood Sugar (High)

Body cells absorb more glucose, and the liver stores glucose as glycogen.

Response: Blood Sugar (High)

Blood glucose levels decrease to the normal range.

Disease/Condition: Blood Sugar (High)

Chronic hyperglycemia leads to diabetes mellitus Type 1 (no insulin) or Type 2 (cells become resistant to insulin).

Thermoregulation

Type: Negative Feedback

Purpose: Maintain stable core temperature for enzyme function and prevent overheating.
Normal Range: 97.7 - 99.5 °F

Stimulus: Thermoregulation (Low)

Exposure to cold causes a drop in body temperature.

Sensor: Thermoregulation (Low)

Thermoreceptors in the skin and hypothalamus detect cooling.

Control Center: Thermoregulation (Low)

The hypothalamus (preoptic area) and sends signals to activate heat-producing processes.

Effector: Thermoregulation (Low)

Skeletal muscles initiate shivering to generate heat, and blood vessels constrict to so less heat escapes (vasoconstriction).

Response: Thermoregulation (Low)

Body temperature increases to the normal range.

Disease/Condition: Thermoregulation (Low)

Severe cases result in hypothermia, which can impair cellular metabolism or frostbite.

Stimulus: Thermoregulation (High)

An increase in core body temperature due to environmental heat or exercise.

Sensor: Thermoregulation (High)

Thermoreceptors in the skin and hypothalamus sense the temperature rise.

Control Center: Thermoregulation (High)

The hypothalamus coordinates cooling mechanisms.

Effector: Thermoregulation (High)

Sweat glands increase sweat production, and blood vessels near the skin dilate → heat loss (vasodilation).

Response: Thermoregulation (High)

Heat dissipates through evaporation and radiation, lowering body temperature.

Disease/Condition:Thermoregulation (High)

Hyperthermia and heat stroke can result from failure of cooling mechanisms.

Osmoregulation

Type: Negative Feedback

Purpose: Maintain proper water and solute balance or prevent excess dilution of blood.
Normal Range: 275–295 mOsm/kg or 280–300 mOsm/L

Stimulus: Osmoregulation (Low)

Excess water intake and the concentration of solutes in the blood is lower than normal.

Sensor: Osmoregulation (Low)

Osmoreceptors in the hypothalamus detect the decrease in osmolarity.

Control Center: Osmoregulation (Low)

The hypothalamus stimulates the posterior pituitary to decrease/inhibits antidiuretic hormone (ADH).

Effector: Osmoregulation (Low)

The kidneys produce more urine and less water reabsorbed in the kidneys. You feel less thirsty and drink less water.

Response: Osmoregulation (Low)

Blood water content increases, restoring osmotic balance.

Disease/Condition: Osmoregulation (Low)

Hyponatremia and can cause cells — especially in the brain — to swell due to osmotic water movement.

Stimulus: Osmoregulation (High)

Water loss (dehydration)

Sensor: Osmoregulation (High)

Osmoreceptors in the hypothalamus detect the increase in osmolarity.

Control Center: Osmoregulation (High)

The hypothalamus signals the pituitary gland to release more ADH.

Effector: Osmoregulation (High)

Kidneys reabsorb more water and thirst is triggered.

Response: Osmoregulation (High)

Blood solute concentration decreases to the normal range.

Disease/Condition: Osmoregulation (High)

In diabetes insipidus, a lack of ADH release or kidney response prevents water reabsorption, leading to excess water loss, dehydration, and hypernatremia.

Calcium Regulation

Type: Negative Feedback

Purpose: Maintain calcium levels for nerve and muscle function or Prevent harmful calcium buildup.
Normal Range: 8.5-10.5 mg/dL

Stimulus: Calcium Regulation (Low)

A drop in blood calcium concentration.

Sensor: Calcium Regulation (Low)

The parathyroid glands detect the low calcium level.

Control Center: Calcium Regulation (Low)

The parathyroid glands release parathyroid hormone (PTH).

Effector: Calcium Regulation (Low)

PTH stimulates bone cells to release calcium, increases kidney reabsorption, and enhances intestinal absorption.

Response: Calcium Regulation (Low)

Blood calcium levels rise to normal.

Disease/Condition: Calcium Regulation (Low)

Hypocalcemia (muscle spasms or seizures). Osteoporosis (Weak and brittle bones)

Stimulus: Calcium Regulation (High)

An increase in blood calcium concentration.

Sensor: Calcium Regulation (High)

The thyroid gland’s C cells detect elevated calcium levels.

Control Center: Calcium Regulation (High)

The thyroid gland releases calcitonin.

Effector: Calcium Regulation (High)

Calcitonin promotes calcium storage in bones and increases excretion through the kidneys.

Response: Calcium Regulation (High)

Blood calcium levels decrease to normal.

Disease/Condition: Calcium Regulation (High)

Hypercalcemia can result in kidney stones, skeletal weakness, and arrhythmias.

Blood Pressure

Type: Negative Feedback

Purpose: Ensure proper blood flow and oxygen delivery or Prevent strain on heart and vessels.
Normal Range: 120/80 mmHg.

Stimulus: Blood Pressure (Low)

A sudden drop in blood pressure, possibly from dehydration or blood loss.

Sensor: Blood Pressure (Low)

Baroreceptors in the neck arteries (sinus and aortic arch) detect decreased pressure.

Control Center: Blood Pressure (Low)

The medulla oblongata in the brainstem processes this information and increase release of ADH, Epinephrine & Aldosterone.

Effector: Blood Pressure (Low)

The heart increases its rate and force of contraction, and blood vessels constrict.

Response: Blood Pressure (Low)

Blood pressure rises back to a normal level.

Disease/Condition: Blood Pressure (Low)

Prolonged hypotension can cause dizziness, fainting, or shock.

Stimulus: Blood Pressure (High)

A rise in blood pressure from stress, exertion, or sodium intake.

Sensor: Blood Pressure (High)

Baroreceptors in the neck arteries (sinus and aortic arch) detect increased pressure.

Control Center: Blood Pressure (High)

The medulla oblongata decreases/suppressed release of ADH, Epinephrine & Aldosterone.

Effector: Blood Pressure (High)

The heart rate slows, and blood vessels dilate.

Response: Blood Pressure (High)

Blood pressure decreases to normal.

Disease/Condition: Blood Pressure (High)

Chronic hypertension may lead to heart disease or stroke.

Blood Clotting

Type: Positive Feedback

Purpose: Prevent blood loss after injury.
Normal Range: No clotting unless injury occurs.

Stimulus: Blood Clotting

Injury to a blood vessel wall exposes collagen fibers.

Sensor: Blood Clotting

Platelets detect the damaged tissue

Control Center: Blood Clotting

Platelets release thrombin (chemical signals) to attract more platelets and activate clotting factors.

Effector: Blood Clotting

Platelets and clotting factors form the initial platelet plug through platelet aggregation (platelet attracting more platelets) and producing a fibrin mesh, which together seal the damaged blood vessel and prevent bleeding.

Response: Blood Clotting

The formation of a stable clot, which occurs when the clotting cascade activates a chain of clotting factors that produce fibrin, strengthening the platelet plug to seal the damaged vessel and stop bleeding.

Disease/Condition: Blood Clotting

Hemophilia causes poor clotting (bleeding out); thrombosis causes excessive clotting.

Childbirth Contractions

Type: Positive Feedback

Purpose: Deliver the baby.
Normal Range: No uterine contractions before labor

Stimulus: Childbirth Contractions

The baby’s head pushes against the cervix.

Sensor: Childbirth Contractions

Stretch receptors in the wall of the cervix detect this stretching and send nerve impulses to the brain

Control Center: Childbirth Contractions

The hypothalamus stimulates the pituitary gland to release oxytocin.

Effector: Childbirth Contractions

The oxytocin travels through the bloodstream and acts on the uterus, stimulating it to contract more forcefully.

Response: Childbirth Contractions

Contractions continue and strengthen until childbirth occurs.

Disease/Condition: Childbirth Contractions

Weak contractions can prolong labor or require medical induction (C-Section).

Fever

Type: Positive Feedback

Purpose: Elevate body temperature to fight infection.
Normal Range: 97.7 - 99.5 °F

Stimulus: Fever

Pathogen or infection enters the body.

Sensor: Fever

Immune cells detects pyrogens (fever-inducing substances)

Control Center: Fever

The hypothalamus receives signals from pyrogens and raises the body’s temperature set point. (acts as the body’s thermostat and controls body temperature).

Effector: Fever

Skeletal muscles induce shivering, and blood vessels constrict to conserve heat (vasoconstriction).

Response: Fever

Body temperature increases to fight infection; later, cooling mechanisms restore normal temperature.

Disease/Condition: Fever

Hyperpyrexia and Sepsis occurs if temperature regulation fails.

Lactation

Type: Positive Feedback

Purpose: Produce milk for infant nourishment.
Normal Range: No milk without stimulation.

Stimulus: Lactation

Infant suckling stimulates sensory receptors in the nipple.

Sensor: Lactation

Nerve endings in the nipple detect suckling.

Control Center: Lactation

The hypothalamus signals the pituitary gland to release prolactin and oxytocin.

Effector: Lactation

Prolactin promotes milk production, and oxytocin triggers milk ejection

Response: Lactation

Continued suckling maintains milk flow and hormone release.

Disease/Condition: Lactation

Galactorrhea (poor milk production) may occur if milk production continues without nursing.

Ovulation

Type: Positive Feedback

Purpose: Release mature egg for fertilization.
Normal Range: Monthly cycle (~28 days).

Stimulus: Ovulation

Rising estrogen levels from developing ovarian follicles.