Chapter 40 Thermoregulation

Based only on size, which animal would have the greater BMR (O2/hr), a sheep or a rat? However, if you divide an animal's BMR by its body mass in kg, which animal (sheep or rat) has a greater BMR (O2/hr/kg of body mass)?

- A sheep because the size of an animal is directly associated with the overall chemical energy requirements. - Energy required to maintain each gram of body weight is inversely related to body weight. Each gram of a mouse requires 20x as many calories as each gram of an elephant.

What processes is the endocrine system responsible for?

- Growth - Development - Reproduction - Metabolic processes - Digestion

What processes is the nervous system responsible for?

- Locomotion - Cognition - Behavior

What is the difference between negative and positive feedback?

- Negative feedback: functions to DAMPEN the stimulus. Homeostasis relies largely on negative feedback. - Positive feedback: a response that AMPLIFIES the stimulus. These processes are driven to completion, rather than kept in balance.

Energy Budgets for Four Animals: Which animals do not grow as adults? Which animal uses the greatest fraction of its energy budget for thermoregulation? Which animal uses the smallest fraction of its energy for thermoregulation? Which animal uses the greatest fraction of its energy budget to keep active?

- Penguins and the deer mice - Mouse - Snake - Penguin

What is the difference between a regulator and a conformer? Give an example!

- Regulator: uses internal control mechanisms to regulate internal changes in the face of external fluctuations. - Ex: river otter is a temperature regulator - Conformer: allows internal conditions to vary with certain environmental changes. - Ex: largemouth bass is a temperature conformer.

What does it mean if an animal is a countercurrent heat exchanger? What happens during this process? What is the result?

- it involves the antiparallel arrangement of blood vessels. - Process: - Arteries transfer heat to veins - Heat exchange occurs along the entire length of the exchanger - As blood in veins approaches the center of the body, it is almost as warm as the body core. RESULT: countercurrent heat exchanges minimizes body heat loss as a result of supplying blood to body parts (feet) immersed in cold water.

When does a human have the lowest heart rate and lowest body temperature? When does a human have the highest risk of cardiac arrest? Greatest muscle strength?

- lowest heart rate and lowest body temperature occurs after midnight. - highest risk of a cardiac arrest: after 6AM and before noon - Greatest muscle strength? After 6PM and before midnight.

What is bioenergetics? What is the equation for the breakdown of ATP? What are the four metabolic processes where an animal gives off heat into its surroundings?

- overall flow and transformation of energy in an animal. - ATP + H2O ----> Pi + ADP + energy - 4 Metabolic Processes: - The digestion and absorption of organic molecules - Cellular respiration - Cellular work - Biosynthesis (which involves growth, storage, and reproduction).

Where is brown fat found? How do we know?

-Adults, but mostly babies. :) - How we know: positron emission tomography scans. Scientists think that these deposits of brown fat function to maintain core body temperature by generating and distributing heat.

In a walrus, what layer of skin contains blubber? Why is it so important that a walrus have this layer of blubber?

-Hyperdermis - It is important that the walrus have this layer of blubber because it protects the walrus from heat loss since heat transfer occurs 50x to 100x faster than heat transfer in air.

What six factors influence the metabolic rate of an animal?

1. Age 2. Sex 3. Size 4. Activity 5. Temperature 6. Nutrition

Cite at least two specific biochemical or physiological processes that are altered when body temperature increases above 37 C.

1. Proteins lose their tertiary structure 2. Membranes become too fluid, lose their structure, and fail to transfer molecules between membranes.

What are the four physical processes that allow for the exchange of heat between an organism and its environment?

1. Radiation 2. Evaporation 3. Convection 4. Conduction

Which type of signal would be involved in stimulating your muscles to contract while running? Which signal would be involved with coordinating digestion processes while you sleep? Which signal would be involved in regulating homeostasis within the body?

1. The Nervous System Signals 2. Endocrine System 3. BOTH!

What are the layers of the skin?

1. epidermis 2. dermis 3. hypodermis

Give an example of a poikilotherm and ectotherm

A fresh water fish living in lakes that change temperature throughout the year. Freshwater fish obtain their heat from the environment and their body temperature changes as the temperature of the lake changes.

What is the FULL definition of homeostasis? What are the homeostatic levels for the four following processes: temperature, blood pH, blood sugar levels, and blood osmolarity.

Ability of an animal to maintain a relatively constant internal environment even when the external environment changes significantly. - Body Temp: 98.6 F and 37 C - Blood pH: 7.4 - Blood glucose: 90mg/100 mL blood - Blood and interstitial fluid osmolarity: 300 mOsm/L

What is uncoupled oxidative phosphorylation?

An uncoupling protein is found in the ETC and as a result, less ATP is produced. This uncoupling allows brown fat cells to generate at least 10x more heat than is normally generated via cellular respiration.

If an animal regulates one physiological process such as osmolarity, does it also regulate all other physiological processes in the body? If so, give an example.

Animals may regulate some internal conditions while allowing others to conform to the environment. - Ex: large mouth bass is an osmoregulator (in freshwater) as well as a temperature conformer.

What are the two types of major sweat glands in humans?

Apocrine: glands associated with stress, releases sweat into pilary canal of a hair follicle, and is regulated by hormones. Eccrine: main gland used to regulate body temperature, and is present throughout the body.

Basal metabolic rate (BMR) is used as the minimal metabolic rate for endotherms. Under what conditions is an animal's BMR measured? What is the BMR of a woman? What is the BMR of a man?

BMR: applies to endotherms. To determine the BMR of an endotherm the animal must be: 1. at rest 2. fasting 3. non-stressed 4. comfortable temperature range BMR of a woman: 1300-1500 kcal/day BMR of a man: 1600-1800 kcal/day

What are the two ways to regulate body temperature by adjusting metabolic heat production? Describe two situations where an animal alters its behavior to help it regulate its body temperature. What is the difference between them?

Behavioral: moving to a location that is warmer/cooler; social behavior- huddling Two ways: - Shivering thermogenesis: muscle activity produces heat. - Non-shivering thermogenesis: many animals (including humans) contain brown fat that is specialized for rapid heat production via non-shivering thermogenesis. Difference: shivering generates heat as a byproduct of cellular work (rapid muscle contraction). Non-shivering thermogenesis occurs when the oxidation of fatty acids in brain fat cells is "tweaked" to generate more heat and less ATP.

Which type of heat transfer primarily occurs when you sit on the seat of your car after its been parked for 8 hours in an open parking lot on a hot summer day?

Conduction

Define Conduction

Conduction: direct transfer of heat between molecules of objects in direct contact with each other.

What type of heat transfer primarily occurs when you experience the cooling effects of an ocean breeze?

Convection

Define Convection

Convection: transfer of heat by movement of air or liquid past a surface.

What is an ectotherm, and an endotherm?

Ectotherm: an animal that obtains its heat primarily from the environment (cold-blooded). Endotherm: an animal that obtains its heat primarily through internal metabolism (warm-blooded).

What type of heat transfer primarily occurs when you sweat while running.

Evaporation

Define Evaporation

Evaporation: removal of heat from the surface of a liquid that is losing some of its molecules as gas.

Give an example of a homeotherm and endotherm.

Humans!

Give an example of a poikilotherm and endotherm.

Hummingbirds even though it generates heat via metabolism, it can also lower its body temperature at night to reflect cooler ambient temps.

When is evaporative cooling the only way that an endotherm can cool its body? Describe two situations where an animal alters its behavior to help it regulate its body temperature.

If the environmental temperatures are above body temperatures, animals gain heat from the environment as well as metabolism. The animal needs to rapidly release heat to prevent its body from rapidly overheating. Evaporative cooling releases a huge amount of heat from the body as liquid water is converted too water vapor. Many terrestrial animals have sweat glands controlled by the nervous system that enhances evaporative cooling.

After adjusting for size, how does the SMR of an alligator differ from the BMR of a man?

If you adjust for size, an alligator uses ~1/200 the energy of a man. This difference is because ectothermy has much lower energy requirements.

Are ectotherms always poikilotherms?

NO! Some ectothermic animals live in environments with stable temperatures. Example: tropical fish that live in CONSTANT temperature.

Are endotherms always homeotherms?

No! Some animals will enter inactive states in which they maintain lower body temperatures. Example: hummingbirds (decrease temperature set point at night-torpor).

What is a poikilotherm and homeotherm?

Poikilotherm: animals whose body temperature varies with the environment. Homeotherms: animals with a relatively constant body temperature.

Which type of heat transfer primarily occurs when a bird warms itself by sitting in a position where it can easily absorb the sun's energy.

Radiation

Define Radiation

Radiation: emission of electromagnetic waves. It can transfer heat between objects that are not in direct contact.

Under what conditions is the Standard Metabolic Rate (SMR) measured in ectoderms? After adjusting for size, how does the SMR of an alligator differ from the BMR of a man?

SMR: applies to ectotherms. To determine the SMR of an ectotherm the animal must be: 1. at rest 2. fasting 3. non-stressed 4. PARTICULAR temperature.

Give 2 examples of positive feedback.

The birth process: 1. The movement of the fetus into the birth canal stimulates nerve fibers in the uterus that sends a signal to the brain to release the hormone oxytocin. 2. Oxytocin triggers more contractions in the uterus, which pushes the fetus further into the birth canal and stimulates more nerve fibers to send more signals to the brain to release more oxytocin. Example two: gastrin stimulation of gastric juices: signal stops when a bolus of food is processed into chyme and the chyme enters the SI.

What layer of skin contains hair follicles and sweat glands?

The dermis

What two organ systems function to coordinate the activity of the body?

The endocrine and nervous system.

Which system uses chemical signals that travel throughout the body and target particular cells that contain receptors for the signal? What does it do?

The endocrine system! It uses hormones as its chemical signals. - Generally slow acting and often long lasting signals - Chemical signal frequently travels throughout the body via the bloodstream. - Its response is limited to cells that have the receptor for the signal (target cells).

Which system uses BOTH electrical and chemical signals that travel in well defined pathways? What does it do?

The nervous system! It uses neurons to send electrical and chemical signals. - It is FAST acting and SHORT lasting. - It also uses dedicated communication lines (axons) to transmit signals a particular pathway. - Its response is limited to cells that are connected by specialized junctions (synapses) to a axon that transmits an impulse.

What are some of the mechanisms involved in thermoregulation?

They involve the integumentary system: skin, hair and nails.

How is heat generated through non-shivering thermogenesis in the mitochondria of brown fat cells?

Triglycerides are broken down to fatty acids and glycerol, and most of the fatty acids are immediately oxidized in the mitochondria. HOWEVER, the oxidative phosphorylation process is uncoupled and most of the energy generated from the oxidation of the fatty acids goes toward heat production.

Give an example of a homeotherm and ectotherm

Tropical fish

What unit of measurement describes an individual's metabolic rate? What is the minimal metabolic rate?

Unit: joules and kilocalories Minimal metabolic rate: the amount of energy that an animal must use for basic biological functions such as: cell maintenance, breathing, and heart beat.

Give an example of negative feedback.

When our body temperature increases, blood vessels on the surface of the skin dilate to increase the release of body heat. When body heat is lost, negative feedback functions to return blood vessels to their normal diameter.

A desert rabbit has large vascularized ears. When the ambient temperature is GREATER than the rabbit's body temperature, how does the diameter of the blood vessels in its ears change in order to help prevent the rabbit from overheating?

When the ambient air temperature is greater than the rabbit's body temperature heat will want to flow into the rabbit, so blood vessels will temporarily constrict. Less heat is absorbed form the environment, which helps prevent the rest of the body form overheating. Blood vessels return to normal size when the air temperature is less than 40C.

A desert rabbit has large vascularized ears. When the ambient temperature is LESS than the rabbit's body temperature, how does the diameter of the blood vessels in its ears change in order to help the rabbit lose excess body heat?

When the ambient air temperature is less than the rabbit's body temperature, blood vessels will dilate to increase the amount of heat that is released from the body via radiation and convection.

What is vasoconstriction?

decrease in the diameter of the superficial blood vessels.

What is vasodilation?

increases the diameter of blood vessels found near the body's surface.

What is the metabolic rate? How can we measure it?

metabolic rate: the sum of all energy-requiring biochemical reactions over a given time interval. Measured in joules, calories (cal) or kilocalories (kcal). - Methods of measurement: - to measure an animal's rate of heat loss: calorimeter, amount of oxygen consumed or carbon dioxide produced.

What is the circadian rhythm? What hormone is involved with the sleep and wake cycle? What is the key point of this biological clock?

set of physiological changes that occur every 24 hours. - hormone: melatonin - Key point: biological clock maintains rhythm even when variation in human activity, room temp., and light levels are minimized.

What are alterations in homeostasis? Give an example.

set points and normal ranges for homeostasis can change under various circumstances. Example: testosterone levels change dramatically during a males life.

What is thermoregulation? Why is it important?

the process by which animals maintain an internal temperature within a tolerable range. It is important because most biochemical and physiological processes are sensitive to changes in body temperature (example: enzyme activity and membrane structure change when temperature increases/decrease).