Chapter 32 The Internal Environment of Animals: Organization and Regulation

Chapter 32 The Internal Environment of Animals:

Organization and Regulation

Diverse Forms & Challenges

● Because form and function are correlated, examining anatomy or structure often provides clues to

physiology, which is biological function.

● The study of animal form and function starts with an examination of the

organization of cells and tissues in the animal body.

● Animals depend on the organization of body systems for coordinating the

activities of different body parts including:

○ regulating body temperature

○ maintaining proper balance of body

salts and water.

Concept 32.1 Animal Form & Function at all Levels

● Multicellularity allows for cell specialization.

● Cells form a working animal body

through successive levels of structural and functional organization:

○ cells, tissues, organs, organ systems, organism

● Many organs have multiple functional roles, ie pancreas functions in

digestive system and the endocrine systems.

● specialized and complex organ systems are built from a few types of tissues:

○ epithelial, connective, muscle, and

endocrine.

Concept 32.1 Animal Form & Function at all Levels

Organ Systems

Concept 32.2 Endocrine & Nervous System Coordinate

● Animals have two major systems for coordinating and controlling responses to stimuli:

○ Endocrine system which uses signaling molecules released into the bloodstream by endocrine cells to carryto all locations in the body.

○ Nervous system which uses neurons to transmit signals along dedicated routes connecting specific locations in the body.

● The signaling molecules broadcasted throughout the body by the endocrine system are called hormones which cause distinct effects on cells that have

receptors for a particular hormone.

● The nervous system conveys information by a

particular pathway a nerve impulses travel towards mainly through xtensions called axons.

○ Nerve impulses can act on other neurons, on muscle cells, and on cells and glands that produce secretions.

Concept 32.2 Endocrine & Nervous System Coordinate

● Regulation of a signaling process involves not only its initiation but also its termination through different control process:

○ Negative feedback, also called feedback inhibition, a control circuit or loop that reduces, or “damps,” the stimulus.

○ Positive feedback, a control mechanism in which the response reinforces the stimulus, leading to an even greater response.

● In vertebrates neuroendocrine signaling involves the hypothalamus and the pituitary gland

○ posterior pituitary, which is an extension of the hypothalamus and stores and secretes hormones synthesized in the hypothalamus.

○ anterior pituitary is an endocrine

gland that both synthesizes and secretes

hormones.

Concept 32.3 Feedback Control Mechanisms

• A regulator uses internal mechanisms to control changes in the internal

environment.

• A conformer allows the internal

environment to change with external variables.

• Animals can be a regulator for some internal conditions and a conformer for others.

• Animals achieve homeostasis by maintaining a set point.

• Negative feedback loops reduces the stimulus.

• Positive feedback loops amplifies the

stimulus.

Concept 32.3 Feedback Control Mechanisms

• Thermoregulation is a process by which animals maintain a tolerable internal temperature.

• Endothermic animals are warmed by metabolism.

• Ectothermic animals gain most of their heat from the

environment.

• Heat exchange takes place by:

o Radiation

o Evaporation

o Convection

o Conduction

Concept 32.3 Feedback Control Mechanisms

• Adaptations for heat loss or heat gain:

o Integumentary system o Insulation

o Circulatory Adaptations o Cooling by evaporative

heat loss

o Behavioral response

o Adjusting heat production

o Acclimatization

Concept 32.3 Feedback Control Mechanisms

• Bioenergetics is the flow and

transformation of energy in animals.

• Metabolic Rate is the amount of energy an animal consumes in a unit of time ie calories/time

• Basal Metabolic Rate of endotherms is metabolism at rest (BMR)

•Standard Metabolic Rate of

exotherms is metabolism at rest.

•Activity greatly affects metabolic rate.

•Energy budgets vary amongst

animals and sexes.

Concept 32.4 Osmoregulation & Excretion

• Osmoregulation is the management of the body’s water and solute content.

• Specialized epithelial cells

called transport epithelium are essential to osmoregulation.

• Nitrogenous waste has the greatest effect on

osmoregulation.

• Enzymes remove nitrogen from macromolecules to form a toxic molecule called ammonia.

• Many species convert ammonia to urea or uric acid.

• Endotherms typically produce

more nitrogenous wastes

Concept 32.4 Osmoregulation & Excretion

• Ammonia is very soluble in water, therefore it is most common waste product of aquatic species.

• Because of ammonia’s toxicity it can not be transported in large volumes.

• Mammals, many amphibians, and marine fishes excrete urea, produced in the liver.

• Urea has low toxicity, but

conversion of ammonia to urea costs energy.

• Land snails, insects, birds, and many reptiles excrete uric

acid.

• Animals excrete uric acid as a

solid which is expensive to

produce.

Concept 32.4 Osmoregulation & Excretion

• Solution separated by a membrane differ in osmotic pressure or osmolarity.

• Osmoconformers do not

actively adjust to surroundings.

• An osmoregulator must control its internal molarity, which

allows them to inhabit a variety of habitats.

• Energy costs depend on the external environment.

• Stenohaline animals cannot tolerate changes in external osmolarity.

• Euryhaline animals can

survive under fluctuations, e.g.

American shad.

Concept 32.4 Osmoregulation & Excretion

• Marine fishes constantly lose water across their gills and produces little urine?

• Sharks remove salt and excrete the waste as feces.

• Fresh water animals constantly lose salt and gain water from diffusion.

• Marine fishes constantly drink water and excrete ions and water with little amounts of urine.

• Some aquatic invertebrates

produce a protective shell around the cell during dry periods.

• Terrestrial adaptations include: a

waxy cuticle, protective shells, and

diurnal behavior.

• Body fluids must first be

collected and then adjusted.

• During filtration the transport epithelium

membrane retains cells and proteins, called filtrate.

• Flatworms have system called protonephridia which are a network of tubes leading to the

nephridiopores from the dead-end branch called flame bulb.

• Metanephridium is a system of tubes with internal openings that

collect fluids in earthworms.

Concept 32.4 Osmoregulation & Excretion

Concept 32.4 Osmoregulation & Excretion

• Terrestrial insects have malpighian tubules that remove nitrogenous

wastes from hemolymph and transport to the

digestive tract to pass through the rectum as a solid.

• The kidneys of vertebrates function in excretion and osmoregulation.

• The kidneys have a dense network of capillaries

associated with tubules

and ducts that carry urine

out of the tubules of the

kidney to ureter.

Concept 32.5 The Mammalian Kidney

• Each kidney is supplied with blood from a renal artery and renal vein.

• Urine exits the kidney through a ureter that drains into the urinary bladder.

• Urine is expelled through the urethra.

• The neprhon consists of a single long tubule and a ball of

capillaries called the glomerulus.

• Bowman’s capsule surrounds the glomerulus.

• Each human kidney has a million

nephrons.

Concept 32.5 The Mammalian Kidney

• The proximal tubule reabsorbs most of the salt and water

from the filtrate as well as other valuable nutrients.

• The Descending limb of the Loop of Henle reabsorbs water from the filtrate.

• In the ascending limb of the Loop of Henle salt diffuses out of the tubule.

• The distal tubule is important in regulating K and NaCl of body fluids.

• The collecting duct carries the

filtrate to the renal medulla

and actively reabsorbs NaCl.

Concept 32.5 The Mammalian Kidney

• Antidiuretic hormone is

produced by the hypothalamus stimulates cells in the distal

and collecting tubules to

reabsorb water in response to increasing blood osmolarity.

• Another system is activated by blood pressure and involves the hormone aldosterone

which acts on the distal tubules to reabsorb more water and Na.

• Another hormone inhibits other

mechanisms to reduce NaCl

reabsorption.