2: Homeostasis

Homeostasis

The maintenance of relatively constant internal conditions despite changes in the internal or external environment.

He coined the term “Homeostasis“ and suggested that every regulatory mechanism of the body exists to maintain homeostasis, or constancy, of the body’s internal fluid environment.

Internal environment

The environment of the cells within the body.

Claude Bernard

He coined the term “internal environment“ and noted that body cells survived in a healthy condition only when the temperature, pressure, and chemical composition of their fluid environment remained relatively constant.

Set point

The normal reading or range of normal for a physiological variable. Also called “set point range.“

Circadian rhythms

Natural oscillations that repeat roughly every 24 hours, responding to environmental changes.

Fishbowl model

A model of homeostasis where the body is compared to a bowl of fluid that must be kept constant.

Wallenda model

A model of homeostasis comparing the body to a circus highwire walker.

Heating system model

A model where the body is likened to a home with a thermostat regulating temperature.

Integumentary system

This system separates the internal environment from the external environment, providing stability of internal fluid volume.

Skeletal system

This system supports and protects internal environment, allowing movement; stores minerals that can be moved into and out of internal fluid

Muscular system

This system powers and directs movements; provides heat

Nervous system

This system regulates homeostatic mechanisms, sensing changes, integrating information, sending signals to effectors

Endocrine system

In this system, homeostatic regulation by secreting signalling hormones that travel through internal environment to effector cells

Cardiovascular system

This system maintains internal constancy by transporting nutrients, water, oxygen, hormones, wastes, and other materials and heat within the internal environment

Lymphatic system

This system maintains constant fluid pressure by draining excess fluid from tissues, cleaning it, and recycling it to bloodstream

Immune system

This system defends internal environment against harmful agents

Respiratory system

This system maintains stable O₂ and CO₂ levels in body by exchanging these gases between external and internal environments; provides vocal communication with others for protection, hunting, etc.

Digestive System

This system maintains relatively constant nutrient level in body by digesting food and absorbing nutrients into internal environment

Urinary system

This system maintains constantly low level of waste and regulates pH of internal environment; helps maintain constancy of internal water volume and balance of ions and other substances

Reproductive system

This system passes genetic code containing information for forming a body and maintaining homeostasis to offspring

Homeostatic control mechanisms

Processes for maintaining or restoring homeostasis in response to changes.

Feedback control loop

Communication networks for maintaining or restoring homeostasis through self-regulation.

Afferent communication

Information going toward a control center.

Efferent communication

Information going away from a control center.

Sensor mechanism

the process wherein a sensor must be able to identify the condition being controlled.

Variable

Any state or condition in the body that can change.

Integrator (control center)

this receives and analyse the input from a homeostatic sensor; the value of a variable is compared with the setpoint value.

Effector mechanism

Its activity is regulated by feedback of info regarding their own effects on a controlled variable.

Effectors

these are organs that directly influence controlled physiological variables.

Feedback

The process of information constantly flowing back from the sensor to the integrator.

Stimulus

A change in a variable that elicits a reaction in a feedback loop.

Response

The operation of the effector in a feedback loop.

Negative feedback mechanism

Inhibitory feedback that opposes changes to stabilize physiological variables.

Positive feedback mechanism

Stimulatory feedback that amplifies changes, often leading to a specific outcome.

Feed-forward control

Information flowing ahead to trigger changes in anticipation of future events.

Intracellular control mechanisms

Operate at the cell level, regulating functions within the cell.

Intrinsic control mechanisms

Operate at the tissue and organ levels using chemical signals.

Extrinsic control mechanisms

Operate at the system and organism levels, involving nervous and endocrine regulation.

Pathology

The study of disease.

Pathophysiology

The organized study of physiological processes associated with disease.

Pathogenesis

The process by which an infection leads to disease.

Signs

Objective abnormalities that can be observed by someone other than the patient.

Symptoms

Subjective abnormalities felt only by the patient.

Syndrome

A collection of different signs and symptoms occurring together.

Acute disease

A disease with sudden onset, short duration, and quick resolution.

Chronic disease

A disease that develops slowly and lasts for a long time.

Subacute disease

A disease with characteristics between acute and chronic.

Aetiology

The study of factors causing a disease.

Idiopathic disease

A disease with undetermined causes.

Communicable disease

A disease that can be transmitted from one person to another.

Incubation period

The time it takes for an infection to develop after exposure.

Remission

The reversal of a chronic disease, potentially leading to a cure.

Epidemiology

The study of disease occurrence, distribution, and transmission in populations.

Endemic

A disease native to a local region.

Epidemic

A disease spreading to many people in a short time.

Pandemic

A disease affecting large geographic regions or spreading worldwide.

Pathogenic organisms

Organisms that cause disease, including prions, viruses, bacteria, fungi,

Prions

proteins that may cause misfolding of protein molecules, thus converting normal proteins of the cell into different proteins.

Viruses

intracellular parasites that consist of a DNA or RNA core surrounded by a protein coat and, sometimes, a lipoprotein envelope; they invade human cells and cause them to produce viral components..

Virion

the complete virus particle existing outside the host cell.

Bacteria

tiny, primitive cells that lack nuclei; cause infection by parasitizing tissues or otherwise disrupting normal function.

Fungi

simple organisms similar to plants but lack the chlorophyll pigments that allow plants to make their own food.

Protozoa

protists, one-celled organisms larger than bacteria whose DNA is organized into a nucleus.

Pathogenic animals

large, multicellular organisms such as insects and worms; parasitising human tissues, bite or sting, or disrupt normal body functions.

Tumours and cancer

abnormal tissue growths, or neoplasms, can cause various physiological disturbances.

Malnutrition

insufficient or imbalanced intake of nutrients which causes diseases.

Autoimmunity

occurs when the immune system attacks one’s own body.

Inflammatory response

a normal mechanism that usually speeds recovery from an infection or injury.

Degeneration

occurs when tissues break apart.