lecture 5 - homeostasis

Homeostasis

The maintenance of stable conditions in the internal environment

Homeostatic regulation is a _____ process in which key set points are constantly

surveilled by sensors and acted upon by effectors.

Homeostatic regulation is a dynamic process in which key set points are constantly surveilled by sensors and acted upon by effectors.

Molecular and genetic homeostasis

DNA replication requires assembly of around 3 to 6 billion nucleotides in correct order to

produce 20,000 to 25,000 genes encoding ~100,000 proteins. Each type of cell has

different mechanisms that control its gene expression and protein formation.

Cellular homeostasis

Each cell of the body has many separate control mechanisms that regulate its function.

Tissues homeostasis

The cells that make up a tissue communicate with each other via mechanical and chemical signals and in some cases form organs that have their own internal controls.

Organ homeostasis

Organs communicate with each other via the nervous system and by releasing different substances that can alter the function of other cells and organs.

What is and an Example of a stimulus in homeostasis

changes in internal or external environment

Body temp over 37C

What can be a sensor of homeostasis regulation

Detects the change

Nerve cells in skin and brain, thermoreceptors, pancreatic a/B cells

What’s control and whtpats an example of control in homeostasis regulation

Processes input and decides on a response

Temperature regulatory center in the brain, hypothalamus,endocrine pancreas’s

What’s does an effector do and what’s example of an effector in homeostasis regulation

Carries out corrective action

Sweat glands throughout the body

most homeostatic control mechanisms employ what type of feedback?

negative feedback

Negative feedback does what to a response?

it reduces a response

If a factor becomes excessive or deficient, a control system initiates _______ , which consists of a series of changes that return the factor toward a certain set point, thus maintaining homeostasis.

If a factor becomes excessive or deficient, a control system initiates negative feedback , which consists of a series of changes that return the factor toward a certain set point, thus maintaining homeostasis.

What does feed forward control do?

continues a response until the desired effect has occurred. The response adapts to the extent of effect.

When does feed forward control occur?

sensors cannot keep up with response outcomes, e.g. neuronal

signaling. Responses are continuously surveilled and then turned off when the desired

effect has be achieved.

Feed forward is a form of what?

delayed negative feedback

What does positive feedback lead to ?

disequilibrium and homeostatic instability.

It perpetuates or a response rather than turning off a response.

Can result in severe and negative outcomes.

What’s not truly a positive feedback

in the case of childbirth, where oxytocin stimulates uterine contractions, and contractions stimulate release of more oxytocin, there is a termination point.

What percentage of the adult human body is fluid ; water containing ions and other substances (O2, glucose, amino acids, fats, etc)

50-70%

Most of this fluid is what?

intracellular

Extracellular fluids and cellular fluids have ___ compositions

1/3 of fluid is ___

2/3 of fluid is ____

1/3 of fluid is extracellular

2/3 of fluid is intracellular

Extracellular fluid is in constant motion

• It circulates in the blood, where it is constantly mixed

• From capillaries, it diffuses between the blood and the interstitial fluid

• These combined movements allow for continuous exchange of substances between (i) cells and the interstitial fluid, (ii) the interstitial fluid and blood

respiratory system

provides and removes?

Provides: O² and pH regulation

Removes : CO² and water

Gastrointestinal

Provides:

Removes :

Provides: nutrients

Removes : Metabolic waste (urea, bilirubin)

• Undigested material

• Sloughed cells

• Microbial and bacterial waste

Hepatic

provides:

Removes:

provides: Converts nutrients to useable

forms for other tissues

Removes: Metabolic waste (urea, bilirubin)

• Hormones

• Toxic substances (drugs, toxins

renal

Provides:

Removes:

Provides: filtered plasma

Removes: metabolic waste ( urea, uric acid, creatine, excess ions and water from food )

Organism size provides and removes

provides repopulates cells when needed

removes cells when damaged

Nervous system does what ?

Controls muscular and secretory activities

What’s sensory input

Sensory receptors (ex. Skin eyes ears)

Integration of info

Brain and spinal (CNS)

Motor output

Voluntary and autonomic responses

Hormone system

Controls metabolic functions

Endocrine glands

Secreted hormones regulate cellular functions

plasma membrane does what

separates the inside of cells from their environment.

functions as a selective barrier to the passage of molecules

between intracellular and extracellular environments.

Water is at what concentration?

higher concentration inside cells than outside,

but ion

gradients prevent loss of water from cells.

What structure is responsible for maintaining these different environments?

Biological membranes