Bio 1.2.1 - Explain how homeostasis is maintained in the cell and within an organism in various environments (including temperature and pH).
Homeostasis: the ability of the body or a cell to seek and maintain a condition of equilibrium or stability within its internal environment when dealing with external changes.
Yo Sean! Below is a rap about Homeostasis! You should listen to it!
Background Information
- The nervous and endocrine systems control homeostasis in the body through feedback mechanisms involving various organs and organ systems.
- Homeostasis is achieved by making sure the temperature, pH (acidity), and oxygen levels (and many other factors like electrolyte balance and blood pressure) are set just right for your cells to survive.
- You are a homoeothermic organism, which means you regulate your own body temperature. Other species like reptiles are not homoeothermic.
![Picture](/uploads/2/8/1/7/28177325/8397104.gif?559)
- The human body tries to maintain a constant temperature of 98.6 degrees F.
- If the body becomes too hot, part of the brain registers this and will activate the sweat glands to help lower the temperature.
- When it's too cold, the muscles are activated, shivering to help generate heat.
- If blood pressure falls, a neurotransmitter called norepinephine is released, which causes the blood vessels to constrict and increases the heart rate which causes blood pressure to rise.
- Other conditions in the body, like blood sugar levels and pH balance, are also monitored and adjusted when they fall outside of the normal range.
- The relationships among all these variables, however, change based on age, activity level, and the environment.
Negative feedback
|
Positive feedback
|
Ph and homeostasis
![Picture](/uploads/2/8/1/7/28177325/4495387.jpg?541)
- Our bodies control pH very carefully. Just a small deviation either way can hurt us tremendously.
- For example, both acidic and basic pHs are required at various points in digestion to maintain balance during the process.
- Saliva in the mouth, the starting point of digestion, is only mildly acidic for the purpose of initially breaking down the food without damaging the teeth or delicate throat tissue.
- The stomach needs to be highly acidic to jump-start the breakdown process as well as act as a defense for the body against any harmful bacteria or other intruders.
- To balance things out on the basic side, it is important that the small intestine has a high pH, because most of the enzymes used in digestion can't function properly in an acidic environment
To the left is a chart showing everyday materials and their pH levels.
body systems used in homeostasis
Many body systems are used in homeostasis. Here are some:
- The circulatory system transports nutrients to all of your body's tissues. Red blood cells provides oxygen to your entire body, white blood cells help to fight off sickness, and platelets clot the blood so you don't continue to bleed. Plasma has the awesome job of holding all of the waste and excess nutrients that the other cells may have left behind.
- The digestive system breaks down nutrients that the body needs to stay healthy and function properly and then disposes of the waste that is left over.
- The renal system helps maintain homeostasis through excretion of urine. The kidneys filter harmful substances out of your body in the form of urine and store it in the bladder until it is finally excreted out through the urethra
- The respiratory system provides oxygen which will then be transported by the circulatory system all over the body. It also allows you to breathe out harmful gases like carbon dioxide.
- The nervous system sends messages throughout the human body to signal things such as production of necessary hormones and signaling the different actions such as constriction of blood vessels and reflex actions to try and maintain homeostasis.
Homeostasis of the cell
The main part of the cell that works to maintain homeostasis is the cell membrane. That's what protects the cell from outside world that could potentially disrupt a cell's homeostasis. The cell membrane is made up of mostly fats (lipids) and protein and is selectively permeable, meaning it only lets certain molecules pass through the membrane. When there is too much of a certain molecule inside the cell, the cell membrane allows some of the molecules to go through the membrane and leave the cell. When there is too much of a molecule outside the cell and not enough inside the cell, the cell membrane will allow enough of the molecule to enter to maintain homeostasis.
Processes used to help maintain homeostasis
![Picture](/uploads/2/8/1/7/28177325/298479.jpg?292)
Passive Transport:
- The cell membrane maintains homeostasis through the processes of diffusion, osmosis and filtration, which are passive forms of transport
- Passive forms of transport move molecules such as water (osmosis) and substrates across the cell membrane
- When there is too much of a certain molecule within the cell, the cell uses diffusion to transport some of those molecules into the environment. When there is not enough of a molecule within the cell, the cell uses diffusion to transport molecules from the environment into the cell
- Diffusion takes no energy on the part of the cell. It is the movement of substance down the concentration gradient, going from a high concentration of a substance to a lower concentration
- Through the processes of diffusion and osmosis, the cell membrane works to maintain homeostasis in the cell by transporting molecules to create equilibrium between the inside of the cell and its environment
![Picture](/uploads/2/8/1/7/28177325/3611553.jpg?195)
Active Transport:
- Active transport is the movement of molecules across a cell membrane in the direction against their concentration gradient, going from a low concentration to a high concentration.
- Active transport is usually associated with accumulating high concentrations of molecules that the cell needs, such as ions, glucose and amino acids.
- If the process uses chemical energy, such as from adenosine triphosphate (ATP), it is known as active transport.
- Secondary active transport involves the use of an electrochemical gradient. Active transport uses cellular energy, unlike passive transport, which does not use cellular energy.
- Examples of active transport include the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants.
![Picture](/uploads/2/8/1/7/28177325/8576044.gif?471)
Endocytosis:
- A form of active transport, meaning it requires energy in the form of ATP
- Endocytosis is the process by which materials move into the cell
- Used to help absorb large polar molecules that cannot pass through the cell (or plasma) membrane
![Picture](/uploads/2/8/1/7/28177325/426550.jpg?478)
Exocytosis:
- A form of active transport; uses energy in the form of ATP
- Materials are exported out of the cell by secretory vesicles. In this process, the Golgi complex packages macromolecules into transport vesicles that travel to and fuse with the plasma membrane. This fusion causes the vesicle to spill its contents out of the cell
- Exocytosis is important in expulsion of waste materials out of the cell and in the secretion of cellular products such as digestive enzymes or hormones, which helps to maintain homeostasis
Types of homeostasis in cells
Lab for 1.2.1
The lab below is a great activity for you to do to show you real life examples of your body maintaining homeostasis. If you're a student, (or a teacher!) you should consider doing this lab with your class to have a fun experience while learning at the same time.
Your browser does not support viewing this document. Click here to download the document.
Branden