Homeostasis (1&2) Flashcards
(7 cards)
What is homeostasis?
Homeostasis is the process by which biological systems actively maintain internal stability while adapting to changing external conditions. It’s dynamic, not static—meaning the body constantly adjusts internal conditions through regulatory mechanisms.
It is vital for survival because key physiological variables (like blood glucose and body temperature) must remain within a safe range.
If homeostasis is disrupted, it can cause disease (e.g., diabetes), and conversely, disease can disrupt homeostasis (e.g., infection altering body temperature).
What are the five components of a homeostatic control system?
Sensor (Receptor): Detects changes in a specific physiological variable (like temperature or glucose).
Set Point: The normal target range for that variable—not a single number, but a range
Control Center: Compares the detected value with the set point and decides if a response is needed.
Effector(s): Tissues or organs that receive signals and act to correct the disturbance
Response: The specific action by the effector that brings the variable back toward the set point.
What are common misconceptions about homeostatic control systems?
The set point is not fixed; it’s a range and can be reset (e.g., fever).
The system is always active, not just turned on when a disturbance occurs.
The effector’s response is the action (e.g., vasoconstriction), not the change in the variable itself (e.g., raised temp).
Homeostasis does not aim to keep things constant, but rather similar—it’s about dynamic balance.
What are some key physiological variables regulated by homeostasis?
Homeostasis maintains several critical internal variables within safe ranges. These include:
Body temperature: Maintained to avoid hypothermia or hyperthermia.
Blood glucose levels: Prevents hyperglycemia or hypoglycemia.
Blood gases (O₂ and CO₂): Ensures proper oxygen delivery and pH regulation.
Blood pH: Critical for enzyme function; disruptions can cause acidemia or alkalemia.
Essential ions: Like calcium, potassium, sodium, and iron—imbalances lead to conditions like anemia or hyponatremia.
Blood pressure: High BP (hypertension) can cause cardiovascular disease.
Body weight: Regulated through energy intake/output; imbalances lead to obesity or anorexia.
How does thermoregulation demonstrate homeostatic control?
Thermoregulation keeps body temperature within a healthy range (~36.1–37.4°C), using a feedback loop:
In a cold environment:
Sensor: Skin and hypothalamus detect a drop in temp.
Set Point: Control center (hypothalamus) sees the value is below the set point.
Effectors:
Blood vessels constrict to reduce heat loss.
Muscles shiver to generate heat.
Response: Heat production increases → temp rises toward normal.
In a hot environment:
Effectors:
Blood vessels dilate (vasodilation) to lose heat.
Sweat glands activate for evaporative cooling.
Response: Body cools down toward the set point.
This is a classic example of negative feedback, where the response reverses the initial disturbance
How do the endocrine and nervous systems contribute to homeostasis?
Endocrine System:
Releases hormones (like insulin or glucagon) into the bloodstream.
Acts slowly, but has long-lasting effects.
Regulates long-term processes like metabolism, growth, and glucose balance.
Example: Pancreas secreting insulin in response to high blood glucose.
Nervous System:
Uses neurons to send rapid signals (via electrical impulses).
Regulates quick adjustments like breathing rate or blood pressure.
Response is fast but short-lived compared to hormones.
Example: Hypothalamus adjusting body temperature via sweating or shivering.
These systems often work together, such as during a stress response.
How does the body maintain blood glucose homeostasis, and how is this impaired in diabetes?
The body maintains blood glucose between 3.9–7.1 mMol/L using two key hormones:
Insulin (from beta cells in pancreas):
Secreted when blood glucose is high (after eating).
Stimulates cells to absorb glucose and store it as glycogen (especially in liver/muscle).
Lowers blood glucose to normal.
Glucagon (from alpha cells):
Secreted when blood glucose is low (e.g., fasting).
Stimulates glycogen breakdown and glucose release by the liver.
Raises blood glucose.
Diabetes Mellitus:
Type 1 Diabetes: Autoimmune destruction of beta cells → no insulin → glucose stays in blood.
Type 2 Diabetes: Insulin resistance → insulin is made, but cells don’t respond → glucose not absorbed.
Consequences:
Chronic high blood glucose can damage organs, cause dehydration, nerve damage, and lead to cardiovascular disease.
This breakdown shows how disease results from disrupted homeostasis.
