Living Systems

Examples of Living Systems in the following topics:

• Defining Physiology

  • Physiology is the science of the normal function of living systems.
  • A stable internal environment is needed for normal physiological function and survival of a living system.
  • Each system contributes to the homeostasis of other systems and of the entire organism.
  • For instance, the neuroendocrine system is the complex interactions of the neurological and endocrinological systems.
  • Anatomy and physiology are complimentary disciplines as the structure of body systems often influences system function.

• Overview of the Endocrine System

  • The endocrine system is a system of ductless glands that secrete hormones, which are chemical messengers that act at a distance.
  • The endocrine system is a system of ductless glands that secrete hormones directly into the circulatory system to be carried long distances to other target organs regulating key body and organ functions.
  • Endocrine signalling is typically slow to initiate but is prolonged in response, providing a counterpoint to the more rapid and short lived nervous system signals.
  • The endocrine system is in contrast to the exocrine system which features ducted glands which secrete substances onto an epithelial surface for example a sweat gland.
  • The endocrine systems found in the head and neck include the hypothalamus, pineal, pituitary and thyroid glands.

• Life Functions

  • An organism is a living system capable of growth, reproduction,metabolism, response to stimuli, adaptation and homeostasis.
  • Cells are the basic unit of life that can be found in every living organism. 
  • Multicellular organisms are typically made up of organ systems, organs, tissues, and cells.
  • The world is made up of both living (biotic) and nonliving things.
  • Living and nonliving things can be distinguished by function.

• Levels of Organization

  • Living organisms are made up of four levels of organization: cells, tissues, organs, and organ systems.
  • Using the circulatory system as an example, a cell in this system is a red blood cell, the heart's cardiac muscle is a tissue, an organ is the heart itself, and the organ system is the circulatory system.
  • An organism is made up of four levels of organization: cells, tissues, organs, and organ systems.
  • While most organ systems control a few specific physiological processes, some processes are more complex and require multiple organ systems to work together.
  • For example, blood pressure is controlled by a combination of the renal system (kidneys), the circulatory system, and the nervous system.

• Comparing the Nervous and Endocrine Systems

  • The nervous system and endocrine system both use chemical messengers to signal cells, but the speed of transmission is different.
  • Both the nervous system and the endocrine system use chemical messengers to signal cells, but the speed at which these messages are transmitted and the length of effect differs.
  • The nervous system responds rapidly to stimuli by sending electrical action potentials along neurons, which in turn transmit these action potentials to their target cells using neurotransmitters, the chemical messenger of the nervous system.
  • The response to stimuli by the nervous system is near instantaneous although the effects are often short lived.
  • The endocrine system relies on hormones to elicit responses from target cells.

• Spleen

  • The spleen, similar to a large lymph node, acts primarily as a blood filter in the mononuclear phagocyte system of the immune system.
  • The spleen is the largest distinct organ of the lymphatic system.
  • The spleen plays important roles in regards to red blood cells and the immune system.
  • Besides these increased risks, the loss of the spleen does not cause major immune system impairment, and most people will still live normal and healthy lives because the lymph nodes and liver perform the same functions as the spleen.
  • In particular, those with splenomegaly (an enlarged spleen that could rupture) or splenic cancers are typically better off living without their spleen than living with the risk of severe bleeding from a ruptured spleen or the plethora of symptoms caused by splenic cancer and its metastases.

• Immunological Memory

  • Immunological memory refers to the ability of B and T cells to produce cells that become long-lived memory cells against specific pathogens.
  • The name "adaptive immune system," is considered to be adaptive because it is a result of an adaptation to an infection with the pathogen during the individual's lifetime and continues to prepare the immune system for potential future pathogens.
  • The passive immunity is short-lived, ranging from a couple days to a couple months.
  • Vaccination is an extremely effective manipulation of the immune system that helps fight diseases.
  • When B and T cells begin to replicate, some of the offspring that they produce will end up becoming long-lived memory cells.

• Kidney Transplant

  • If no living-related donor is available, it may take months or years on the waiting list before a suitable donor organ is available.
  • Living-donor renal transplants are further characterized as genetically related (living-related) or non-related (living-unrelated) transplants, depending on whether a biological relationship exists between the donor and recipient.
  • The first kidney transplants between living patients were undertaken in 1954, both in Boston and in Paris.
  • Thus, having medications to suppress the immune system was essential.
  • However, suppressing an individual's immune system places that individual at greater risk of infection and cancer (particularly skin cancer and lymphoma), in addition to the side effects of the medications.

• Subdivisions of the Nervous System

  • The nervous system is comprised of two major subdivisions, the central nervous system (CNS) and the peripheral nervous system (PNS).
  • Gray matter, which is only gray in preserved tissue but pink or light brown in living tissue, contains a relatively high proportion of neuron cell bodies.
  • The PNS is further subdivided into the autonomic nervous system (ANS) and the somatic nervous system.
  • As mentioned, the autonomic nervous system acts as a control system and most functions occur without conscious thought.
  • The enteric nervous system (ENS) controls the gastrointestinal system and is sometimes considered part of the autonomic nervous system.

• Aging and the Nervous System

  • One of the effects of aging on the nervous system is the loss of neurons in cerebral cortex.
  • One of the effects of aging on the nervous system is the loss of neurons.
  • The cerebral cortex can lose as much as 45% of its cells and the brain can weigh 7% less than in the prime of our lives.
  • Parkinson's disease is the most common movement disorder of the nervous system.
  • Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive deterioration together with declining activities of daily living and neuropsychiatric symptoms or behavioral changes .