Biology Homeostasis and Feedback Systems

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Questions and Answers

What is the role of the modulator in the feedback system?

Communicates using nerve impulses only

Detects the stimulus in the environment

Processes information from the receptor (correct)

Carries out a response to the stimulus

What does homeostasis primarily refer to?

The ability to evolve over generations

The ability to thrive in various climates

The ability to adapt to environmental changes quickly

The ability to maintain a constant internal environment (correct)

What happens to enzymes during hyperthermia?

They operate at optimal levels

They are completely inactivated

They become more active

They denature and cause metabolic reactions to fail (correct)

Which of the following is NOT an internal environmental factor that the body regulates for homeostasis?

Air pressure outside the body Signup and view all the answers

Which of the following is NOT one of the methods of heat transfer?

Absorption Signup and view all the answers

Which organ is primarily responsible for thermoregulation?

Skin Signup and view all the answers

What is the primary function of negative feedback in homeostasis?

To maintain conditions within a narrow range Signup and view all the answers

Which situation is an example of positive feedback?

Contractions during childbirth Signup and view all the answers

What does the hypothalamus monitor in the body?

Body core temperature Signup and view all the answers

What are tolerance limits?

The acceptable range for internal factors sustaining life Signup and view all the answers

Which method of heat transfer exclusively removes heat?

Evaporation Signup and view all the answers

What is the primary function of peripheral thermoreceptors?

Detect changes in external temperature Signup and view all the answers

Why are mammals considered a successful group concerning homeostasis?

They maintain constant levels of activity despite fluctuations in conditions. Signup and view all the answers

Which significant effect occurs during cell respiration related to thermoregulation?

Production of ATP Signup and view all the answers

In a feedback system, what does a stimulus do?

It triggers a response that alters the original condition. Signup and view all the answers

What is a potential harmful effect of positive feedback?

Exacerbation of conditions like heat stroke Signup and view all the answers

What is the primary role of the hypothalamus in thermoregulation?

Serving as the thermoregulatory centre Signup and view all the answers

Which effectors are involved in responding to decreased temperature?

Skeletal muscles and skin-based effectors Signup and view all the answers

How do hair erector muscles respond to cold temperatures?

They contract to trap an insulating layer of air Signup and view all the answers

What occurs in the body when temperatures increase?

Increased sweat production Signup and view all the answers

Which mechanism helps to increase heat loss at elevated temperatures?

Relaxation of hair erector muscles Signup and view all the answers

What effect does hyperglycemia have on cells in the body?

Inhibits chemical reactions due to osmotic changes Signup and view all the answers

What is the effect of skeletal muscle activity during cold exposure?

Muscles undergo involuntary contraction to generate heat Signup and view all the answers

Which of the following describes the role of endocrine glands during increased body temperature?

They decrease metabolic activity to reduce heat production. Signup and view all the answers

What is the primary role of the liver in blood glucose regulation?

Converts glycogen to glucose for release into the blood Signup and view all the answers

Which type of cells in the pancreas secrete glucagon?

Alpha cells Signup and view all the answers

What condition occurs when blood glucose levels are too low?

Hypoglycemia Signup and view all the answers

What is the function of antidiuretic hormone (ADH)?

Promotes water reabsorption in kidneys Signup and view all the answers

Which glands secrete glucocorticoids such as cortisol?

Adrenal cortex Signup and view all the answers

Which of the following describes gluconeogenesis?

Conversion of fats and amino acids to glucose Signup and view all the answers

What role does the pancreas play in the regulation of blood sugar levels?

Secretes glucagon and insulin Signup and view all the answers

What happens to cells if there is too much water in the body?

Cells undergo cytolysis Signup and view all the answers

Which hormone is primarily responsible for increasing the permeability of kidney tubules to sodium and water?

Aldosterone Signup and view all the answers

What is the main consequence of increased CO2 levels in the body?

Potential damage to cells Signup and view all the answers

Where are central chemoreceptors located, and what do they primarily detect?

In the medulla oblongata, detecting carbon dioxide levels Signup and view all the answers

Which of the following correctly describes the role of the inspiratory centre?

It initiates inhalation by triggering respiratory muscles. Signup and view all the answers

How does voluntary control of breathing primarily occur?

Through connections between cerebral cortex and spinal cord. Signup and view all the answers

Which of the following components are involved in the regulation of gas concentrations in the body?

Respiratory and circulatory systems Signup and view all the answers

What primary function do peripheral chemoreceptors serve?

Detect changes in H+ (pH) concentration Signup and view all the answers

In osmoregulation, what role does aldosterone play?

Increases sodium and water reabsorption Signup and view all the answers

Study Notes

Homeostasis

The ability of an organism to maintain a constant internal environment within small tolerance limits necessary for life.
Important internal environmental factors that the body regulates include:
- Body temperature
- Blood pH
- Blood pressure
- Concentrations of dissolved substances in body fluids
- Concentration of blood glucose
- Concentration of O2 & CO2
- Concentration of metabolic wastes
Tolerance limits are the upper and lower limits of a normal range of a factor.
Homeostasis provides the body with a degree of independence from the environment.
Mammals are successful because they can maintain constant levels of activity despite fluctuations in external and internal environmental conditions.
This steady state is maintained by feedback systems, usually operated through negative feedback.

Feedback systems

A feedback system is a circular situation in which the body responds to a stimulus, with the response altering the original stimulus.
Negative feedback:
- Involved in maintaining conditions within a narrow range.
- Responses counteract the original stimulus and restore the system to its original state.
- The response reverses the direction of the stimulus.
- Example: Controlling blood glucose levels.
Positive feedback:
- A stimulus causes responses that increase the stimulus in the same direction.
- Acts as an amplifier of response.
- Does not contribute to homeostasis and can be damaging to the body.
- Example: High fever/heat stroke, uterine contractions during childbirth.

Components of a feedback system

Receptor (detector): Specialized cells in the brain or organs detect the stimulus.
- A stimulus never stays exactly constant but fluctuates around the set value (set point).
Modulator (processing centre): Processes information from the receptor and sends information to the effector.
Effector: Organs, muscles, or glands carry out a response that reverses the stimulus.
Communication in the feedback system can be by hormones or nerve impulses.

Thermoregulation

The process of regulating body temperature.
Important because:
- High body temperature (hyperthermia) denatures enzymes, causing metabolic reactions to fail.
- Low body temperature (hypothermia) inactivates enzymes, slowing down metabolic activities.
Involves controlling the amount of heat lost and heat gained across the body surface.
Heat can be transferred in and out of the body through conduction, convection, and radiation.
Evaporation can only remove heat.
Heat can also be gained through metabolism.
During cell respiration, food is oxidized to release energy.
- Some energy is used for cellular work, like active transport and cell division.
- Most of the energy is released as heat energy.
Thermoregulation is controlled by the hypothalamus in the brain.
- Monitors the body's core temperature.
The skin is the major homeostatic organ involved in thermoregulation, due to its large surface area.

Components of the thermoregulatory system

Receptors:
- Peripheral thermoreceptors in the skin (warm and cold receptors) detect changes in external temperature.
- Central thermoreceptors in the hypothalamus detect changes in blood temperature.
Modulator: Thermoregulatory centre in the hypothalamus.
Effectors:
- Skin-based effectors:
  - Sweat glands
  - Hair erector muscles
  - Skin arterioles/capillaries
- Skeletal Muscles
- Endocrine glands:
  - Adrenal gland
  - Thyroid gland

Responding to decreased temperature (increase heat gain & reduce heat loss)

Effectors:
- Skin-based effectors:
  - Sweat glands: Not stimulated. No sweat production. No evaporation of sweat.
  - Hair erector muscles: Contract, raising the hairs and trapping a layer of air, which acts as an insulating layer to reduce heat loss.
  - Skin arterioles/capillaries: Vasoconstriction. Less blood flows to the surface of the skin, reducing heat loss by radiation.
- Skeletal muscles: Shiver (involuntary contraction) to produce heat.
- Endocrine glands:
  - Adrenal gland: Stimulated to release adrenaline, which increases the body's metabolic rate in the liver to generate heat.
  - Thyroid gland: Stimulated to release thyroxine, which also increases metabolic rate.

Responding to increased temperature (reduce heat gain & increase heat loss)

Effectors:
- Skin-based effectors:
  - Sweat glands: Stimulated to produce and release sweat. Evaporation of sweat removes heat from the skin surface.
  - Hair erector muscles: Relax, lowering the hairs and minimizing trapped air layer, allowing heat loss.
  - Skin arterioles/capillaries: Vasodilation. More blood flows closer to the surface of the skin, increasing heat loss by radiation.
- Skeletal muscles: Not stimulated, no shivering. No heat production.
- Endocrine glands:
  - Adrenal gland: Not stimulated, no adrenaline secretion. No heat production.
  - Thyroid gland: Not stimulated, no thyroxine secretion. No heat production.

Regulation of blood sugar levels

Important because:
- High blood glucose level (hyperglycemia) increases blood osmotic pressure, causing water to move out of cells. This can stop chemical reactions.
- Low blood glucose level (hypoglycemia) means cells do not have enough glucose for respiration. This can also disrupt metabolism.
Organs involved:
- Liver
- Pancreas
- Adrenal glands

Role of the liver

Converts glucose into glycogen for storage or glycogen to glucose for release into the blood.

Role of the pancreas

Contains clusters of hormone-secreting cells called the islets of Langerhans.
These clusters contain α cells and β cells:
- α cells secrete glucagon.
- β cells secrete insulin.
Effects of insulin:
- Increases glucose uptake by cells.
- Promotes glycogen formation from glucose in the liver.
- Promotes protein synthesis.
- Suppresses gluconeogenesis.
- Inhibits lipolysis.
Effects of glucagon:
- Increases glycogen breakdown to glucose in the liver.
- Promotes gluconeogenesis.
- Increases lipolysis.

Role of the adrenal glands

Adrenal glands consist of two parts:
- Adrenal medulla (inner): Secretes adrenaline and noradrenaline.
- Adrenal cortex (outer): Secretes glucocorticoids (cortisol).

Treatment of diabetes mellitus using gene therapy

Involves taking a copy of the insulin gene and finding a way to get it into target cells so they can produce insulin.
A vector (like a virus) is used to carry the insulin gene and deliver it into the cell.
Once inside the cell, the gene is expressed to produce therapeutic insulin.

Regulation of body fluid concentrations

Osmoregulation is very important because:
- Too much water: Cells undergo cytolysis (bursting) as water enters the cells by osmosis.
- Too little water: Chemical reactions stop, blood pressure drops, and toxic wastes accumulate.
Like thermoregulation, osmoregulation is based on a balance between fluid gain and fluid loss.
A constant composition of body fluids is achieved when fluid gain equals fluid loss.

The kidneys

Important excretory and osmoregulatory homeostatic organs.
The functional units of the kidneys are called nephrons.

Antidiuretic hormone (ADH)

Also known as vasopressin.
Released from the posterior pituitary gland.
Causes the distal convoluted tubule and collecting duct of the nephron to become more permeable to water.

Aldosterone

Plays an important role in osmoregulation.
Released from the adrenal cortex.
Increases the permeability of kidney tubules, leading to greater sodium reabsorption into the bloodstream.
As a result, more water is reabsorbed.

Regulating water intake by the thirst mechanism

The thirst mechanism is triggered by a decrease in blood volume and an increase in blood osmolarity (concentration of solutes in the blood)
Specialized receptors in the hypothalamus sense these changes and trigger the feeling of thirst.

Regulation of gas concentrations

The levels of respiratory gases (oxygen and carbon dioxide) must be regulated properly to ensure a continuous supply of oxygen for cell respiration and to remove carbon dioxide, a toxic waste product.
Too much carbon dioxide will cause a drop in blood pH, which can damage cells and disrupt metabolism.
Carbon dioxide is carried to the lungs by blood and later excreted in expired air, while oxygen from inspired air is delivered to the cells by blood.
Both the respiratory and circulatory systems are involved in the regulation of gas concentrations.

Control of breathing

Breathing rate is regulated by the respiratory centre located in the medulla oblongata.
The respiratory centre contains two regions:
- Inspiratory centre: Controls inhalation.
- Expiratory centre: Controls exhalation.
Carbon dioxide and hydrogen ions (pH) are the main chemical factors that affect breathing rate.
- Increases in their concentrations are detected by chemoreceptors:
  - Central chemoreceptors (located in the medulla oblongata) detect changes in carbon dioxide concentration in the blood.
  - Peripheral chemoreceptors (located in the aorta and carotid arteries) detect changes in hydrogen ion concentration in the blood.

Voluntary control of breathing

Voluntary control comes from connections between the cerebral cortex and spinal cord.
It bypasses the respiratory centre in the medulla oblongata.
It provides protection by preventing harmful/irritating gases and water from entering the lungs.

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Description

Explore the essential concepts of homeostasis and feedback systems in biology. This quiz covers the mechanisms through which organisms maintain a stable internal environment and respond to stimuli. Test your knowledge on key regulatory processes and their significance for survival.