Animal physiology

Tissues

Specialized cells rarely function alone, but rather as groups of these imilar cells. There are many different kinds of cells, but they are all classified as one of four these groups types: **epithelial**, **muscle**, **connective**, or **nervous**.

To survive, organisms must:

* extract energy and nutrients from the environment
* build all internal structures they need
* eliminate toxins and metabolic waste products
* sense the environment and respond to it in various ways, including movement
* maintain constant conditions in their internal environments
* reproduce

BMR measured when:

1. In thermoneutral zone (range of temp. where MR is minimal)
2. Fasting (no more SDA)
3. Resting

Basal metabolic rate (BMR)

Applies to homeotherms;The metabolic rate of a resting endotherm at a temperature within its thermoneutral zone.

Standard metabolic rate (SMR)

Applies to poikilotherms (ectotherms).

SMR measured when:

1. Fasting (no more SDA)
2. Resting
i.e., SMR varies with temp.

Epithelial tissues

Are sheets of cells that create barriers between different compartments and frequently have secretory functions.

Muscle tissues

Contract to generate forces and movement.

Connective tissues

Provide structure and support.

Nervous tissues

Convey and process information.

Organ system

A group of organs that work together to carry out certain functions.

Blood plasma

Is the fluid portion of the blood and is 20% of all extracellular fluid.

Interstitial fluid

Is the fluid that batches the cells of the body and is 80% of all extracellular fluid.

Homeostasis

A narrow range of stable and optimal physical and biochemical conditions.

Set point

The desired temperature.

Comparator

Senses the current temperature and compares that value to the set point. Thus the sensing of the temperature is **feedback** information.

Error signal

The results of any difference between the set point and feedback information; is converted into commands.

Regulatory systems

They obtain, process, and integrate information; they use that information to issue commands to **effectors** such as muscles or glands that effect changes in the internal environment. Effectors are also called **controlled** **systems** because their activities are controlled by the neural or hormonal signals from their respective -. Important components of any - are the sensors such as light-, temperature-, and pressure-sensitive cells that provide feedback information to be compared with internal set points.

Negative feedback

Is information used to counteract the influence that created an error signal.

Positive feedback

Amplifies a response.

Feedforward information

Is a feature of regulatory systems that changes the set point in anticipation of a change in conditions.

Thermoregulatory adaptations

Enables animals to tolerate extreme conditions or to control their body temperatures in spite of environmental conditions in order to stay within thermal limits for optimal function.

Temperature sensitivity (Q10)

This of a reaction or process can be described in terms of Q10, a factor calculated by dividing the rate of a process or reaction at a certain temperature, RT, by the rate of that same process or reaction at a temperature 10 degrees Celsius lower, RT–10:

Q10 = (RT)/(RT-10)

Acclimatized

To (cause to) change to suit different conditions of life, weather, etc.

Isozymes

Are enzymes that differ in amino acid sequence but catalyse the same chemical reaction.

Homeotherms

Animals that maintain a constant body temperature.

Poikilotherms

Animals that experience a fluctuating body temperature.

Endotherms

Have the ability to vary their metabolic heat production to compensate for the loss of heat to the environment.

Ectotherms

Are largely dependent on environmental sources of heat.

Heterotherms

Organisms that act like ectotherms some of the time and like endotherms at other times.

Radiation

Heat moves from warmer objects to cooler ones via the exchange of infrared -.

Convection

Heat exchanges with a surrounding medium such as air or water that flows over a surface.

Conduction

Heat flows directly between two objects at different temperatures when they come into contact.

Evaporation

Heat is transferred away from a surface when water evaporates on that surface.

Energy budget

The total balance of heat production and heat exchange, based on the simple fact that if the body temperature of an animal is to remain constant, the heat entering the animal must equal the heat leaving it. The heat coming in is usually from metabolism and radiation (Rabs, for radiation absorbed). Heat leaves the body via the four mechanisms listed above—radiation emitted (Rout), convection, conduction, and evaporation. The - takes the mathematical form:

Heat in = heat out

Aorta

A large blood vessel with oxygenated blood.

Countercurrent heat exchange

Heat is exchanged between blood vessels carrying blood in opposite directions.

Thermoneutral zone

When within a narrow range of environmental temperatures, the metabolic rates of endotherms (birds and mammals) are at low levels and independent of environmental temperature. It is bounded by a **lower critical temperature** and an **upper critical temperature**.

Brown fat

Most nonshivering heat production occurs in specialized adipose tissue. In these cells, a protein called **thermogenin** uncouples proton movement from ATP production, allowing protons to leak across the inner mitochondrial membrane rather than having to pass through the ATP synthase and generate ATP. In nonshivering thermogenesis, metabolic fuels are consumed without producing ATP, but heat is still released.

Hypothalamus

The major thermoregulatory integrative centre of mammals at the base of the brain. This centre is a key player in many regulatory systems of vertebrates.

Hypothermia

Is a below-normal body temperature.

Daily torpor

Daily bouts of regulated hypothermia.

Hibernation

Regulated hypothermia that lasts for days or even weeks, during which the body temperature falls close to environmental temperature.

Respiratory gases

That what animals must exchange are oxygen (O2 ) and carbon dioxide (CO2 ). Cells need to obtain O2 from the environment to produce an adequate supply of ATP by cellular respiration. CO2 is an end-product of cellular respiration, and it must be removed from the body to prevent toxic effects.

Ventilation

Mechanisms that move air or water over the environmental sides of those surfaces.

Perfusion

Mechanisms that circulate extracellular fluids on the internal sides.

Partial pressures

Describes the concentrations of different gases in a mixture.

Fick’s law of diffusion

Whether in air or water, the diffusion rates of respiratory gases between an animal and its respiratory medium—air or water— depend on the partial pressure gradients across the gas exchange surfaces and on other factors that are described quantitatively with a simple equation:

* Q is the rate at which a gas such as O2 diffuses between two locations.
* D is the diffusion coefficient, which is a characteristic of the diffusing substance, the medium, and the temperature.
* A is the area across which the gas is diffusing.
* P1 and P2 are the partial pressures of the gas at the two locations.
* L is the path length, or distance, between the two locations.
* (P1 – P2 )/L is a partial pressure gradient.

External gills

Gills are highly branched and folded extensions of the body surface that provide a large surface area for gas exchange. These gills are vulnerable to damage and are tempting morsels for predators.

Internal gills

Protective body cavities for gills.

Lungs

Are highly divided internal cavities with large surface areas for respiratory gas exchange with air. Because it’s tissue is elastic, it can be inflated with air and deflated as a means of ventilating the respiratory exchange surfaces.

Tracheae

A respiratory gas exchange system consisting of a network of air-filled tubes in insects that branch through all tissues of the insect’s body. It divides into two smaller airways, the **primary bronchi** (singular bronchus). The primary bronchi extend all the way to the posterior air sacs and also branch into **secondary** **bronchi**. The posterior air sacs also have connections to the secondary bronchi. Secondary bronchi divide into tubelike **parabronchi** that run parallel to one another through the lungs in a posterior to anterior direction.

Afferent blood vessels

Bring deoxygenated blood to the gills.

Efferent blood vessels

Take oxygenated blood away from the gills.

Countercurrent blood flow

Blood flows through the lamellae in the opposite direction to the flow of water over the lamellae. This flow maximizes the transfer of O2 from water to blood.

Dead space

The air remaining in lungs and airways after exhalation.

Air sacs

Are an important and unique feature of the avian respiratory system, and they occupy much of the body cavity of the bird. They can be divided into a group of anterior air sacs and a group of posterior air sacs. The are interconnected with each other, with the lungs, and with air spaces in some of the bones. They are not gas exchange surfaces; rather, they act as bellows to maintain a unidirectional flow of air through the lungs.

Pharynx

Where air that enters the lungs through the oral cavity or through the nasal passages join together.

Larynx

Or the voice box, which houses the vocal cords.

Bronchi

Are the major air passageways of the lungs. They lead to the **bronchioles**, which are finely branched, as are the blood vessels.

Alveoli

Are the sites of gas exchange.

Surface tension

Gives the surface of a liquid the properties of an elastic membrane.

Surfactant

Is a substance that reduces the surface tension of a liquid.

LaPlace’s law

Which describes the relationships between pressure (P), tension (T), and radius (r) of bubbles: P = 2T/r. The larger the radius, the less pressure it takes to overcome the tension. Alveoli are not all the same size, so according to , inhalation should preferentially inflate the larger alveoli and not the smaller ones. The unique property of lung surfactant solves this problem because as the larger alveoli inflate, their surface tension increases, favouring the inflation of the smaller alveoli. Also, the increased surface tension in the inflated lungs adds to the recoil during exhalation, facilitating the emptying of the lungs.

Thoracic cavity

A closed compartment bounded on the bottom by a sheet of muscle called the **diaphragm**.

Pleural membrane

A continuous sheet of tissue that covers each lung and also lines the thoracic cavity adjacent to the lung.

Intercostal muscles

Between the ribs are two sets of these muscles. The external - muscles expand the thoracic cavity by lifting the ribs up and outward. The internal - muscles decrease the volume of the thoracic cavity by pulling the ribs down and inward. During strenuous exercise, the external - muscles increase the volume of air inhaled, making use of the inspiratory reserve volume, and the internal - muscles increase the amount of air exhaled, making use of the expiratory reserve volume. The abdominal muscles can also aid in breathing. When they contract, they cause the abdominal contents to push up on the diaphragm and thereby contribute to the expiratory reserve volume.

Hematocrit

The percent of the blood volume consisting of RBCs.

Positive cooperativity

The influence of O2 binding to one Hgb subunit on the O2 affinity of the other subunits.

Myoglobin

Consists of just one polypeptide chain associated with an iron-containing ring structure that can bind one O2 molecule. It has a higher affinity for O2 than Hgb does, so it picks up and holds O2 at PO2 values at which Hgb is releasing its bound O2. It facilitates the diffusion of O2 in muscle cells and provides an O2 reserve for times when metabolic demands are high and blood flow is interrupted.

Bohr effect

The influence of pH on the function of Hgb.

Carbonic anhydrase (CA)

Speeds up the conversion of CO2 to H2CO3.

Carotid and aortic bodies

They are chemosensors. In these nodes of neural tissue we have physiological sensitivity to blood PO2 on the large blood vessels leaving the heart.

Circulatory system

Consists of a muscular pump (heart), a fluid (blood), and a series of conduits (blood vessels) through which the fluid is pumped throughout the body.

Cardiovascular system

Heart, blood, and vessels.

Gastrovascular system

Highly branched central cavities that bring the external environment into the animal.

Heats

Muscular chambers in circulatory systems that move the extracellular fluid through the body.

Hemolymph

The extracellular fluid that is the same as the fluid in the circulatory system, in open circulatory systems.

Extracellular fluid

In animals with a closed circulatory system, it refers to both the fluid in the circulatory system and the fluid outside it.

Interstitial fluid

The extracellular fluid outside the circulatory system.

Open circulatory systems

In these systems a heart moves the hemolymph through vessels leading to different regions of the body. The fluid leaves the vessels to filter through the tissues before returning to the heart.

Ostia

Opening through where the fluid returns directly to the heart. They have valves that allow hemolymph to enter the relaxed heart but prevent it from flowing in the reverse direction when the heart contracts.

Arteries

Blood flows out of the heart and into these vessels that carry blood away from the heart.

Capillaries

Are tiny, thin-walled vessels where materials are exchanged between blood and the interstitial fluid.

Arterioles

Smaller branches from arteries that feed blood into capillary beds.

Venules

Small vessels that drain capillary beds.

Veins

Consists out of venules that ultimately deliver blood back to the heart.

Pulmonary circuit

When blood is pumped from the heart to the lungs and back to the heart.

Systemic circuit

When blood is pumped from the heart to the rest of the body and back to the heart.

Sinus venosus

Where blood returning from all parts of the body collects, that feeds into the muscular **atrium**.

Atrium

Pumps blood into the more muscular chamber, the **ventricle**.

Bulbus arteriosus

The last chamber where contraction of the ventricle pushes blood into. It is a highly elastic chamber.

Aorta

A large dorsal artery where blood leaving the gills collects in, which distributes blood to smaller arteries and arterioles leading to all the organs and tissues of the body.

Atrioventricular (AV) valves

One-way valves between the atria and ventricles, prevent backflow of blood into the atria when the ventricles contract. The right - valve is called the **tricuspid valve** because it has three leaves. The left AV valve is called the **bicuspid valve** because it has two leaves. The bicuspid valve is also called the **mitral valve** because it has the shape of a religious headdress called a miter. There are also one-way valves between the ventricles and the arteries leaving the heart. The **pulmonary valve** goes to the lungs, and the **aortic valve** goes to the aorta. These two valves are also called **semilunar** **valves** because their separate leaves are shaped like half-moons.

Superior (upper) vena cava and the inferior (lower) vena cava

Are the large veins that return deoxygenated blood from the upper and lower body to the right atrium.

Pulmonary artery

Where the right ventricle pumps the blood into when it contracts, causing the tricuspid valve to close.

Pulmonary veins

Return the oxygenated blood from the lungs to the left atrium, from where the blood enters the left ventricle through the bicuspid valve.

Cardiac cycle

Contraction of the two atria, followed by contraction of the two ventricles and then relaxation. It is divided into two phases: **systole**, when the ventricles contract, and **diastole**, when the ventricle relax. At the very end of diastole, just before the ventricles contract, the atria contract and top off the volume of blood in the ventricles. The sounds of the —the “lub-dup” heard through a stethoscope—are created by the heart valves slamming shut.

Pacemaker cells

Some cardiac muscle cells that initiate action potentials without stimulation from the nervous system. These specialized muscle cells do not contract, but they generate rhythmic sequences of action potentials that spread to neighbouring cardiac muscle cells that do contract. Since cardiac muscle cells are in electrical contact with one another through gap junctions, the action potentials from the pacemaker cells spread rapidly through a large mass of cardiac muscle, causing it to contract in unison. Coordinated contraction is essential for pumping blood effectively.

Sinoatrial node

The primary pacemaker of the heart is a group of modified cardiac muscle cells, located at the junction of the superior vena cava and right atrium.