Section 4 - Thermoregulation

Hypothermia

A patholigcal lowering of the body temperature to or beyond the point of survival

Homeotherm

Warm-blooded animal

• Mammals and birds

• Able to maintain ther own body temperatures

Poikilotherms

Cold-blooded animal

• Body temperatures are roughly the same as the environment

Which type generates their own eat? Homeotherms or Poikilotherms?

Homeotherms

How do homeotherms generate their own heat?

By converting matter to energy

• Results in a large amount of energy where 2/3rds is lost as heat.

Generation of heat at the cellular level (how it works)
What type (Homeo/Poikilo) sees more of this action?

• The Na/K pump in the membrane flips to move potassium into and sodium out of the cell. This process, which is active transport, utilizes ATP. Therefore, the entire process generates heat which is captured and stored in the body’s water reservoir.

• Homeotherms have more pumps per cell than poikilotherms

What types of cells are especially important to the addition of body heat?

Muscle cells

What organ creates a significant amount of the body’s heat?

The heart

Diurnal Temperature Rhythm

A body temperature pattern that repeats on a daily basis

Diurnal animals

Animals active during the daylight hours but asleep at night

At what point in the daily cycle of a diurnal animal is the body’s temperature the coolest?

The time right as they awaken from sleep

Why does the body cool so much during sleep?

the BMR (Basal metabolic rate) is at a minimal, meaning heat rate, nerve function, and respiration are slowed—generating less heat

How does the body warm itself after waking?

As an animal moves about, its metabolism increases, of which increases heat generation

How are nocturnal animals different than diurnal animals?

Due to nocturnal animals being awake at night and asleep during the day, they essentially have a “flipped” heat graph compared to diurnal animals.

Why do dehydrated animals have a harder time regulating their body temperature?

Due to the lack of water content in the animal’s body (water is a heat sink)

• Lack of water leads to a wider fluctuation in body temperatures

What external factors heavily impact an animal’s body temperature?

• The temperature of the environment itself (extreme temps call for more physiological effort)

• The water content found in the environment (humidity and precipitation… water is a heat sink!)

What does “smaller animals have a great surgace area per unit of mass” actually mean?

For every gram of body weight, a small animal has more exposed skin than a large animal does

• This is important for why smaller animals get dehydrated faster

The hypothalamus senses low and high temperatures and activates specific systems to maintain body heat

True

How does the body cool itself down?

• Maximize surface area

• Sweating (insensitive)

  • Water is brought to the surface of the body to then be dissipated into the environment. The cool water on the body surface then allows for heat in the body to be drawn out into the environment.

• Panting

Why do animals pant?

To increase water and heat loss

• Water is expelled when breathing!

What do eccrine glands mostly secrete? apocrine glands?

• eccrine: water

• apocrine: proteins

What species has the most eccrine glands?

Humans

How do animals respond to low temperatures?

• Minimized exposed surface area

  • Puckering of the skin (goosebumps)

• Piloeretion

  • Erection of hair

• Shivering

  • Muscle spasms (recall than 75% of muscle activity is lost as heat)

• Decrease blood flow to the extremities

  • Extremities have more exposed surface area + not as important as the torso cavity

• Brown fat metabolism

Brown fat vs white fat

• Brown fat contains more mitchondira and have a faster metabolic rate

Hibernation

A dormant state in animals where all physiological processes are slowed

• They are NOT stopped

• Strictly done by warm-blooded animals

• Heavily dependent on brown fat

What can wake an animal from hibernation early?

When core body temperature reaches a critically low level

• Waking raises BMR and core body temp.

Why is exposure to water at extreme temperatures dangerous?

Water causes faster air exposure due to the heat conductivity of water

Hyperthermia

A pathological increasing of body temperature to or beyond the point of survival

• Associated with times of extreme fluid loss

What species is most at risk for hyperthermia?

Pigs, as they are unable to sweat or pant well

• Depend on mud

Why is hypothermia a risk during anesthesia?

Neural tissue is put to sleep, and the body itself cools as if asleep. The hypothalamus then cannot sense and correct body temperature.

Heat stroke

Result of body temperature building up faster than the evaporative cooling effects can remove it

Why do fevers occur?

The body raises the BMR to combat the infection, as bacteria and viruses are generally killed in the presence of high heat

What could happen during a fever if the hypothalamus’ temperature detecting cells are denatured/damaged?

Can lead to the body temperature to climb continually without any rate limit

Denature

Change in the function of a protein

BMR is partially regulated by cells in the hypothalaus which sense heat

True