Homeostasis and Feedback Systems Quiz

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Questions and Answers

What is defined as the steady state of the internal environment of the body?

Control systems

Equilibrium

Homeostasis (correct)

Feedback loop

Which of the following best describes a receptor in a feedback system?

Sends chemical signals only

Analyzes input and determines output

Monitors changes in a controlled condition (correct)

Provides means for control center's response

What is the role of the control center in a feedback system?

Analyzes input and determines an appropriate response (correct)

Provides a means for response

Monitors stimuli exclusively

Interfaces with the external environment

Which of the following conditions can disrupt homeostasis?

Severe infections Signup and view all the answers

What happens during a homeostatic imbalance?

Responses of body cells restore balance Signup and view all the answers

What does extracellular fluid (ECF) primarily consist of?

Sodium chloride and nutrients Signup and view all the answers

What is the primary difference between intracellular fluid (ICF) and extracellular fluid (ECF)?

ICF has large amounts of potassium and phosphate ions Signup and view all the answers

What is a stimulus in the context of a feedback system?

Any disruption that changes a controlled condition Signup and view all the answers

What is the primary function of the control center in a feedback system?

To establish the range of values for a controlled condition Signup and view all the answers

Which component of a feedback system provides the necessary means for a control center's response?

Effector Signup and view all the answers

What is interstitial fluid?

Fluid that fills spaces between cells Signup and view all the answers

Which type of feedback mechanism enhances the response of the system?

Positive feedback Signup and view all the answers

What may lead to a homeostatic imbalance in the body?

Congenital metabolic disorders Signup and view all the answers

When blood glucose levels fall too low, which component must respond to restore balance?

Effector Signup and view all the answers

How do cells in the human body primarily communicate with each other?

By using the nutrients found in ECF Signup and view all the answers

What term describes the internal environment that protects tissues from external influences?

Extracellular fluid Signup and view all the answers

Which organ system is affected by Multiple sclerosis and Parkinson’s disease?

Nervous system Signup and view all the answers

What is an effector's role in the feedback system?

To produce a response after receiving commands Signup and view all the answers

Which statement is true regarding the fluid systems in the human body?

Dynamic exchange occurs between ECF and ICF Signup and view all the answers

Which disorder is commonly related to disturbances in the endocrine system?

Goitre Signup and view all the answers

What role does extracellular fluid (ECF) play in maintaining homeostasis?

It maintains volume and composition of body fluids Signup and view all the answers

What role do receptors play in a feedback system?

Monitor and evaluate changes in a controlled condition Signup and view all the answers

Which component is NOT found in high concentrations in intracellular fluid (ICF)?

Sodium ions Signup and view all the answers

Environmental factors that can cause homeostatic failure include which of the following?

Chemical pollutants Signup and view all the answers

What type of cell communication allows for direct cytoplasmic transfer between adjacent cells?

Gap junctions Signup and view all the answers

Which type of signal is released by one cell and diffuses to nearby cells?

Paracrine signals Signup and view all the answers

In which context is contact-dependent signaling particularly important?

Cell growth and development Signup and view all the answers

Which method of cell-to-cell communication is restricted to adjacent cells due to diffusion limitations?

Paracrine signaling Signup and view all the answers

What is a characteristic of autocrine signals?

They act on the same cell that secreted them. Signup and view all the answers

What is a major function of cell adhesion molecules (CAMs) in contact-dependent signaling?

Transfer of signals across cell membranes Signup and view all the answers

What role do connexins play in gap junctions?

They form the channels connecting adjacent cells. Signup and view all the answers

Which of the following can function as both an autocrine and a paracrine signal?

Histamine Signup and view all the answers

What is the ultimate consequence of cardiac hypertrophy when it surpasses its compensation limit?

Myocyte death and cardiac failure Signup and view all the answers

Which growth factor is NOT mentioned as a trigger for increased cellular protein production in cardiac hypertrophy?

Epidermal growth factor Signup and view all the answers

What type of hyperplasia occurs in the female breast during puberty due to hormonal stimulation?

Physiologic hyperplasia Signup and view all the answers

What is a common cause of atrophy following immobilization of a bone fracture?

Disuse atrophy Signup and view all the answers

Compensatory hyperplasia is observed after which of the following events?

Partial resection of tissue Signup and view all the answers

Which statement best describes atrophy?

Reduction in cell size and number Signup and view all the answers

What is a likely consequence of diminished blood supply to a tissue?

Atrophy Signup and view all the answers

Endometrial hyperplasia is an example of which type of hyperplasia?

Pathologic hyperplasia Signup and view all the answers

What is the primary function of homeostasis?

To maintain stability through constancy Signup and view all the answers

Which term describes an increase in cell size due to increased workload, such as in cardiac hypertrophy caused by hypertension?

Hypertrophy Signup and view all the answers

What is the potential consequence if allostasis leads to sustained changes in the body’s set point?

Development of a pathology Signup and view all the answers

What type of cellular response occurs as an adaptation to chronic irritation?

Metaplasia Signup and view all the answers

What is an example of a reversible cellular response to acute transient injury?

Acutereversible injury Signup and view all the answers

In the context of allostasis, what role does the brain play?

Predicts the body’s needs Signup and view all the answers

Which of the following is NOT a form of cellular adaptation to severe physiologic changes?

Necrosis Signup and view all the answers

What could happen if there is a failure of homeostasis?

Development of diseases Signup and view all the answers

Study Notes

Applied Homeostasis

Homeostasis is the body's internal equilibrium maintained through constant interactions of regulatory processes.
Homeostasis is a dynamic state—not static, but a constant adjustment.
Body's internal equilibrium can shift within a narrow range. (e.g. blood glucose level normally stays between 70-110 mg/dL).
All body structures contribute to maintaining the internal environment within normal limits.

Desired Learning Outcomes

Explain homeostasis at a cellular level.
Differentiate between homeostasis and allostasis.
Explain adaptation, acclimatization, biological clock & apoptosis.
Describe the effects of increased demand/stress on a cell.

Intro: The Cell

Cell theory (Schleiden & Schwann, 1839): Cells are the functional & structural unit of living organisms.
All life is composed of one or more cells formed from pre-existing cells.
Cells are the smallest form of life as it is the structural basis for living organisms.
A cell is the basic living unit in the body.

The Cell

The human body contains approximately 100 trillion cells.
Each cell is uniquely adapted to perform specific functions.
Cells all have basic functional characteristics such as metabolism.
Cells deliver end products to the surrounding medium.
Cells can reproduce additional cells of their own kind.
Cells, tissues, organs and systems.

Internal Environment

The proper functioning of body cells depends on the precise regulation of the composition of the interstitial fluid surrounding them .
This interstitial fluid is often called the body’s internal environment.
Blood plasma and interstitial fluid exchange substances.
Substances move across the tiny blood capillaries' thin walls.
Capillaries give cells the needed materials (e.g., glucose, oxygen, ions).
They also remove wastes (e.g., carbon dioxide) from the interstitial fluid.
Unicellular organisms (e.g., amoeba) are dependent on the external environment.
Multicellular organisms are largely independent from their external surroundings, with an internal environment.

Internal Environment (Extracellular Fluid)

Internal environment is a watery medium bathing all the cells of the body – Extracellular Fluid (ECF).
ECF comprises blood plasma.
Also includes Interstitial fluid surrounding the cells.
Intracellular fluid (ICF) is the fluid within cells.

Cell-Cell Communication

Cells communicate with each other for conveying physiological information.
Four basic cell-to-cell communication methods:
- Gap junctions: Allow direct cytoplasmic transfer of electrical and chemical signals between adjacent cells.
- Contact-dependent signals: Require interaction between surface molecules on one cell membrane and another.
- Local communication: Uses paracrine and autocrine signals that diffuse through extracellular fluid to reach target cells.
- Long-distance communication: Uses a combination of electrical signals (nerve cells) and chemical signals (blood). (e.g., hormones)

Important characteristics of cell-cell communication types

Gap junctions: Are not all alike, differing across tissues. 20 different connexin isoforms. Only way to allow direct transfer of electric signals between cells.
Contact-dependent signals: Mediated by Cell adhesion molecules (CAMs) which occur in immune system development and growth. CAMs act as receptors and link to cytoskeleton and intracellular enzymes allowing signal transfer in both directions across cell membranes.

Local communication (Paracrine and Autocrine Signals)

In some cases, one molecule can act as both an autocrine and paracrine signal. - Cells release paracrine signals.
Signal molecules reach their target cells by diffusing through interstitial fluid.
The signaling range is limited to adjacent cells due to diffusion distance.
Histamine (a paracrine molecule), is an example released from damaged cells in response to skin injury.

Long-distance communication (Electrical or Chemical)

Communication is by nervous and endocrine systems.
Endocrine system utilizes hormones.
Hormones are secreted into the blood for circulation throughout the body.
Hormones only act on target cells that have receptors for the hormone.
Nervous system uses a combination of chemical and electrical signals.
In neurons, an electrical signal travels along a nerve cell (neuron) until it reaches the end.
This signal becomes a chemical signal (neurocrine).
If a molecule quickly diffuses from the neuron to a target cell, it's called a neurotransmitter.
If the molecule takes longer for action and is through the blood, it's called a neurohormone.

Cellular Signaling (Primarily Chemical)

Cells can detect both chemical and physical signals.
Physical signals are generally converted to chemical signals at the receptor level.
Receptors sense diverse stimuli but initiate limited cellular signals.
Receptors have ligand-binding and effector domains.
Same ligand might have different effects depending on effector domain.
Ligand binding triggers receptor conformation change.
Signal sorting and integration happen in signaling pathways (often multistep, with secondary messengers).
Second messengers enable readily diffusible information transfer throughout the cell.

Overview of Cell Signaling

Signal molecules bind to receptors on the cell membrane.
Plasma membrane is where signals are received.
Transduction: Relay molecules in a signal transduction pathway.
Response: Activation of cellular response inside the cell.

Intro-Homeostasis

Homeostasis: Maintenance of internal equilibrium through regulatory processes.
In response to changing conditions, the body's equilibrium shifts within compatible limits.
Blood glucose levels (e.g, 70 to 110 mg/dL).

Feedback control Systems of Homeostasis

Feedback systems, also called loops, constantly monitor and adjust internal conditions.
Each monitored variable (like temperature, BP, or blood glucose) is called a Controlled Condition
A disruption of a controlled condition is called a stimulus.

Components of Feedback Systems

Receptor: Body structure sensing changes in a controlled condition; sends input to control centre.
Control center: Determines set point and analyses the input, generating an appropriate response/output.
Effector: Receives output from control center, causing changes in controlled condition.

Feedback System Diagram

Shows how one part of the system feeds the information back to the others to continuously create homeostasis.

Feedback System Types

Negative feedback: Response negates or reverses the stimulus. (e.g., maintaining body temperature).
Positive feedback: Response reinforces the stimulus. (e.g., childbirth).

Negative feedback example

Example is blood glucose regulation.
Sensors detect high blood glucose.
Control center (pancreas) releases insulin
Effectors (cells) take up glucose from blood.
Blood glucose falls to normal level.

Components of a Feedback System

Receptors detect and send signals
Control center receives, processes, and decides on feedback
Effectors perform the feedback (action)

Homeostatic Mechanisms

Congenital metabolic disorders (inherited causes).
Aging (with Homeostenosis): Homeostenosis refers to a decrease in homeostatic functions and ability associated with aging.
Chromosomal abnormalities (genetic causes).
Environmental factors (e.g., UV radiation, pollutants.)

Homeostatic Imbalance

Disturbances of homeostasis, normal body equilibrium
Negative feedback mechanisms may overwhelm
Positive feedback mechanisms can be destructive.

Examples of Homeostatic Imbalance in body systems

Integumentary system (e.g., burns, skin cancer)
Skeletal system (e.g., scoliosis, osteoporosis)
Muscular system (e.g., muscular dystrophy)
Nervous system (e.g., multiple sclerosis, Alzheimer’s)
Endocrine system (e.g., goiter, diabetes, pituitary dwarfism)
Cardiovascular system (e.g., atherosclerosis)
Lymphatic system (e.g., immunodeficiencies like AIDS, autoimmune disorders)
Respiratory system (e.g., bronchitis, emphysema)
Digestive system (e.g., heartburn, ulcers)
Urinary system (e.g., kidney stones, polycystic kidney disease)
Reproductive system (e.g., pelvic inflammatory disease, cancer)

Homeostasis Model vs. Allostasis Model

Homeostasis maintains constant internal conditions.
Allostasis adjusts internal conditions in response to changing anticipated needs (i.e., anticipating future changes).

Features of homeostasis

Stability of internal conditions
Maintaining of life
pH, concentration of ions, osmolality, blood glucose, blood oxygen

Features of allostasis

Adapting to changing internal/external environments
Blood pressure, heart-rate, body core temperature, hormones, sleep-wake cycles, and metabolic energy

Acclimatization

Physiological or behavioral changes within an organism
In response natural climate or environment.
Usually completely reversible
E.g., elevated altitude, physiological responses in red blood cell count increase to compensate for lower oxygen concentration.

Apoptosis

Programmed cell death is tightly regulated in humans.
Removing damaged cells and assisting in development.
Cell removal mechanism.
Abnormalities can be linked to neurodegenerative diseases.

Necrosis

Uncontrolled cell death.
Features are cell swelling, inflammation, and membrane integrity loss.
Different from Apoptosis as it is not a regulated process.

Biological Clock

Inherent biological mechanism influencing cyclical behaviors and physiological processes.
Daily, monthly, and seasonal changes within the body are common examples.
Control of circadian rhythms (e.g., sleep-wake cycles, temperature, hormone levels).

Suprachiasmatic Nucleus (SCN)

Master biological clock controlling daily (circadian) rhythms

Applied Physiology of Homeostasis with Examples

Blood glucose regulation: Hormones (insulin & glucagon) regulate blood glucose levels.
Blood pressure control: A balance of hormonal control and nerves maintain blood pressure.
Examples from patient cases (dehydrated patient example).

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Description

Test your knowledge on homeostasis and the feedback systems in the human body. This quiz covers key concepts such as receptors, control centers, and the effects of imbalances. Understand how the internal environment is regulated and the roles of various body fluids.