2. Thermoregulation

Success Criteria

Your learning has been successful if you can do the following:

I can define thermoregulation and describe what the set point is.
I can explain why it is important for the body to be kept at this set point.
I can explain the four mechanisms of heat transfer.

Vocabulary

Learn these so you can communicate this concept well.

Active transport: Movement of substances across a cell membrane against its concentration gradient, assisted by enzymes and requiring energy.
Aerobic respiration: Enzyme controlled process which requires oxygen to produce 38 ATP from the breakdown of glucose.
ATP: Energy 'currency' of the cell, used to perform many cell processes.
ATP synthase: Enzyme that produces 38 ATP at the end of the electron transport chain, during aerobic respiration.
Conduction: Loss of heat by transfer from a hot surface touching a cold surface.
Convection: Loss of heat in a liquid or gas by particle movement in currents.
Core temperature: Actual temperature of the vital organs such as the heart, brain and liver.
Denature: Loss of an enzyme's normal shape so that it no longer functions; caused by a less than optimal temperature.
Enzymes: Biological catalyst that speeds up a chemical reaction.
Evaporative cooling: Loss of heat through sweat.
Lipid bilayer: Two layers of phospholipids that make up the bulk of the cell membrane. Its fluidity selectively allows the passage of some substances.
Membrane permeability: How easily substances can pass through the cell membrane.
Radiation: Loss of heat in infrared radiation emitted by the skin.
Set point: Temperature that the body is trying to maintain via thermoregulation (37°C)
Thermoregulation: Homeostatic process of controlling body temperature.

Hei Mahi (Do Now)

Do Now in your OneNote/Notebook:

1. What is homeostasis?
2. Write down as many human characteristics that are homeostatic (things that happen to maintain a stable internal environment).

Hei Mahi (Do Now)

Do Now in your OneNote/Notebook:

1) Define what is considered to be normal body temperature in humans.

2) Explain why cells need a warm temperature to function.

Hei Mahi (Do Now)

Do Now in your OneNote/Notebook:

I placed these four objects in a fridge. Which one would get the coldest in 10 minutes? Explain your answer.

Exit Task

In your Learning Journal:

Re-write this interpreting question so it is asking about Thermoregulation:

What is the consequence?

Then, write an answer for it.

Exit Task

In your Learning Journal:

Re-write this interpreting question so it is asking about Thermoregulation:

Why does it happen?

Then, write an answer for it.

Exit Task

In your Learning Journal:

Re-write this interpreting question so it is asking about Heat Transfer:

How did it happen?

Then, write an answer for it.

What is Thermoregulation?

THERMOREGULATION is the homeostatic process of controlling body temperature.

With thermoregulation in humans, the body CORE TEMPERATURE is maintained at a stable internal environment with a SET POINT of 37°C. (Note that core temperature and set point are different things).

What is the Purpose of Thermoregulation?

Enzyme Function

Our survival depends on the ability of life processes to occur. AEROBIC RESPIRATION is a particularly essential life process, as it produces the ATP we need to carry out other processes such as ACTIVE TRANSPORT.

Aerobic respiration is made possible by ENZYMES, especially the enzyme ATP synthase.

Enzymes are temperature-sensitive, meaning they can only function within a narrow range of temperatures of around 37°C. Enzymes DENATURE in humans above 38°C. Below 37°C, the rate of reaction reduces until a point that enzyme activity does not occur.

Thermoregulation is vital in maintaining this optimal set point of 37°C, so that enzymes can function, our life processes can occur and that we may survive.

(Links to EXCELLENCE) Enzymes when core temperature is HOTTER than the set point.

At higher temperatures, enzymes can become denatured, meaning that their three-dimensional shape is altered and they lose their ability to function. The rate of denaturation increases with temperature, so as the body temperature increases, the activity of the enzymes also decreases.

The specific temperature at which this occurs can vary depending on the specific enzyme, but in general, a 1-2°C increase in core body temperature can cause denaturation of some enzymes. A core body temperature of around 41°C can be life-threatening, and at this temperature, many enzymes can become denatured and stop functioning properly.

In the case of hyperthermia, the elevated body temperature can cause denaturation of enzymes involved in cellular metabolism, leading to a decrease in metabolic rate. This can result in decreased energy production and decreased efficiency in cellular processes, leading to potential cellular damage and dysfunction.

Additionally, hyperthermia can affect the activity of enzymes involved in the regulation of body temperature itself. For example, hyperthermia can impair the activity of heat shock proteins, which help protect cells from heat stress, further exacerbating the effects of elevated body temperature.

(Links to Excellence) Enzymes when the core temperature is COLDER than the set point.

At low temperatures, the movement of the enzyme molecules becomes sluggish, and their ability to bind to substrates and catalyze reactions decreases. This results in a decrease in the rate of chemical reactions, which can have a significant impact on the functioning of the body. For example, enzymes involved in energy production and metabolism become less efficient, leading to decreased energy production and an increase in fatigue.

Hypothermia occurs when the core body temperature drops below the normal range of 36-37°C. As the body temperature decreases, the activity of enzymes decreases as well. This can result in a slowing or cessation of many physiological processes, including cellular respiration, metabolism, and cellular function.

Cell Membrane Permeability and Integrity

MEMBRANE PERMEABILITY refers to how easily substances can pass through the cell membrane. This helps to maintain the proper balance of ions and other substances inside the cell, and protects the cell from harmful substances.

The integrity and permeability of the cell membrane is determined by the fluidity of the LIPID BILAYER that makes up the membrane. The lipid bilayer is composed of phospholipids, and at normal temperatures, the phospholipids are in a fluid state and can move freely within the lipid bilayer. The more fluid, the more permeable.

Changes in our core temperature can alter the permeability of our cell membranes, affecting diffusion of substances into and out of the cell.

(Links to EXCELLENCE) Membrane permeability when core temperature is HOTTER than the set point.

An increase in temperature can cause the phospholipids to become more fluid, which can increase the fluidity of the cell membrane - more than normal. This can increase the permeability of the membrane, allowing ions and other small molecules to move more freely across the membrane - more than what's required to maintain a constant internal environment.

This increased permeability can lead to the loss of ions and small molecules, leading to cellular dehydration and altering the normal ion gradients across the membrane. This can disrupt normal cellular processes and contribute to the development of cellular damage.

(So, the cell could be spending energy on active transport of ions, but membrane that's too permeable could undo the work done by active transport).

This increased fluidity can also affect the function of membrane proteins, which are embedded in the lipid bilayer. In extreme cases, high temperatures can cause the lipid bilayer to become so fluid that it can break apart, leading to a loss of membrane integrity and cell death.

(Links to EXCELLENCE) Membrane permeability when the core temperature is COLDER than the set point.

When the body temperature decreases, the phospholipids and therefore the cell membrane becomes less fluid. This can lead to changes in the permeability of the membrane, making it more difficult for ions and other small molecules to cross the membrane causing disruptions in normal cell function.

For example, changes in ion gradients across the membrane can interfere with the normal function of ion channels and transporters, which play critical roles in maintaining cell membrane potential, transmitting nerve impulses, and transporting ions and other small molecules into and out of the cell.

This decreased permeability can also affect the function of membrane proteins and enzymes, which may become more rigid and less able to perform their normal functions. In extreme cases, low temperatures can cause the lipid bilayer to become so rigid that it can no longer maintain its integrity, leading to cell damage or death.

For example, hypothermia can also disrupt normal membrane-associated enzyme activity, which can interfere with a wide range of metabolic processes. For example, enzymes involved in the breakdown of glucose to produce ATP may become less efficient, reducing the cell's ability to produce energy.

Mechanisms of Heat Transfer

Name two things Bear Grylls did to help either stop losing heat or produce more heat.

Heat can be gained or lost from any place where the body is in contact with the environment (skin, lungs and digestive tract), through one or several of the following mechanisms:

Conduction

CONDUCTION is the loss of heat by transfer from a hot surface touching a cold surface. It only accounts for 3% of heat loss, because air is a bad conductor.