Homeostasis
Size and shape affect the way an animal interacts with its environment
Rate of exchange is proportional to a cell’s surface area while amount of exchange material is proportional to a cell’s volume
More complex organisms have highly folded internal surfaces for exchanging materials
In vertebrates, the space between cells is filled with interstitial fluid, which allows for the movement of material into and out of cells
All animal cells share similarities in the ways in which they
Exchange materials with their surroundings
Obtain energy from organic nutrients
Synthesize complex molecules
Reproduce themselves
Detect and respond to signals in their immediate environment
Tissues are classified into four main categories: epithelial, connective, muscle, and nervous
Epithelial tissue: covers the outside of the body and lines the organs and cavities within the body
It contains cells that are closely joined
The shape of epithelial cells may be
cuboidal (like dice)
columnar (like bricks on end)
squamous (like floor tiles)
The arrangement of epithelial cells may be
simple (single cell layer)
stratified (multiple tiers of cells)
pseudostratified (a single layer of cells of varying length)
Connect, anchor, and support
Includes blood, adipose, bone, cartilage, loose and dense connective tissue
Form extracellular matrix around cells
provides scaffold for attachment
Protects and cushions
mechanical strength
Transmit information
Nervous tissue: initiate and conduct electrical signals from one part of the animal’s body to another
Neuron: single nerve cell
Electrical signals produced in a nerve cell may stimulate or inhibit other cells to
Initiate new action potentials in other neurons
Stimulate muscle to contract
Stimulate glands to release chemicals
In vertebrates, the fibers and foundation combine to form six major types of connective tissue:
Loose connective tissue: binds epithelia to underlying tissues and holds organs in place
Cartilage: a strong and flexible support material
Fibrous connective tissue: is found in tendons and ligaments
Tendons: attach muscles to bones
Ligaments: connect bones at joints
Adipose tissue: stores fat for insulation and fuel
Blood: composed of blood cells and cell fragments in blood plasma
Bone: mineralized and forms the skeleton
Control and coordination within a body depend on the endocrine system and the nervous system
Endocrine system: transmits chemical signals called hormones to receptive cells throughout the body via blood
A hormone may affect one or more regions throughout the body
Hormones are relatively slow acting, but can have long-lasting effects
Nervous system: transmits information between specific locations
The information conveyed depends on a signal’s pathway, not the type of signal
Nerve signal transmission is very fast
Nerve impulses can be received by neurons, muscle cells, endocrine cells, and exocrine cells
Feedback control: maintains the internal environment in many animals
Animals manage their internal environment by regulating or conforming to the external environment
Regulator: uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation
Conformer: allows its internal condition to vary with certain external changes
Animals may regulate some environmental variables while conforming to others
Set point: normal value for controlled variable
Sensor: monitors particular variable
Integrator: compares signals from the sensor to set point
Effector: compensates for deviations between actual value and set point
Example: body temperature in mammals
Organisms use homeostasis to maintain a
“steady state” or internal balance regardless
of external environment
Acclimatization: homeostasis can adjust to changes in external environment
Thermoregulation: adaptation to the thermal environment
Osmoregulation: adaptation to the osmotic environment
Excretion: strategies for the elimination of waste products of protein catabolism
Homeostatic processes for thermoregulation involve form, function, and behavior
Thermoregulation: the process by which animals maintain an internal temperature within a tolerable range
Endothermic animals: generate heat by metabolism; birds and mammals are endotherms
Ectothermic animals: gain heat from external sources ectotherms include most invertebrates, fishes, amphibians, and nonavian reptiles
In general, ectotherms tolerate greater variation in internal temperature, while endotherms are active at a greater range of external temperatures
Endothermy is more energetically expensive than ectothermy
Heat regulation in mammals often involves the integumentary system: skin, hair, and nails
Five adaptations help animals thermoregulate:
insulation = skin, fur, feathers, blubber
circulatory adaptations= vasodilation and vasoconstriction
cooling by evaporative heat loss
behavioral responses
adjusting metabolic heat production
In winter, many animals bask in the sun or on warm rocks.
In summer, many animals burrow or move to damp areas.
Some animals migrate to more suitable climates.
Thermoregulation is controlled by a region of the brain called the hypothalamus
The hypothalamus triggers heat loss or heat generating mechanisms
Fever is the result of a change to the set point for a biological thermostat
Negative feedback: the variable being regulated brings about responses that move the variable in the opposite direction
ex: Decrease in body temperature leads to responses that increase body temperature
May occur at cellular or molecular level
Also prevents homeostatic responses from overcompensating
Positive feedback: reinforces the direction of change
Far less common
Accelerates a process
Explosive system
ex: Birth in mammals
Feedforward regulation: animal’s body begins preparing for a change in some variable before it occurs
Anticipatory
Speeds up homeostatic responses and minimizes deviations from the set point
Many result from or are modified by learning
Size and shape affect the way an animal interacts with its environment
Rate of exchange is proportional to a cell’s surface area while amount of exchange material is proportional to a cell’s volume
More complex organisms have highly folded internal surfaces for exchanging materials
In vertebrates, the space between cells is filled with interstitial fluid, which allows for the movement of material into and out of cells
All animal cells share similarities in the ways in which they
Exchange materials with their surroundings
Obtain energy from organic nutrients
Synthesize complex molecules
Reproduce themselves
Detect and respond to signals in their immediate environment
Tissues are classified into four main categories: epithelial, connective, muscle, and nervous
Epithelial tissue: covers the outside of the body and lines the organs and cavities within the body
It contains cells that are closely joined
The shape of epithelial cells may be
cuboidal (like dice)
columnar (like bricks on end)
squamous (like floor tiles)
The arrangement of epithelial cells may be
simple (single cell layer)
stratified (multiple tiers of cells)
pseudostratified (a single layer of cells of varying length)
Connect, anchor, and support
Includes blood, adipose, bone, cartilage, loose and dense connective tissue
Form extracellular matrix around cells
provides scaffold for attachment
Protects and cushions
mechanical strength
Transmit information
Nervous tissue: initiate and conduct electrical signals from one part of the animal’s body to another
Neuron: single nerve cell
Electrical signals produced in a nerve cell may stimulate or inhibit other cells to
Initiate new action potentials in other neurons
Stimulate muscle to contract
Stimulate glands to release chemicals
In vertebrates, the fibers and foundation combine to form six major types of connective tissue:
Loose connective tissue: binds epithelia to underlying tissues and holds organs in place
Cartilage: a strong and flexible support material
Fibrous connective tissue: is found in tendons and ligaments
Tendons: attach muscles to bones
Ligaments: connect bones at joints
Adipose tissue: stores fat for insulation and fuel
Blood: composed of blood cells and cell fragments in blood plasma
Bone: mineralized and forms the skeleton
Control and coordination within a body depend on the endocrine system and the nervous system
Endocrine system: transmits chemical signals called hormones to receptive cells throughout the body via blood
A hormone may affect one or more regions throughout the body
Hormones are relatively slow acting, but can have long-lasting effects
Nervous system: transmits information between specific locations
The information conveyed depends on a signal’s pathway, not the type of signal
Nerve signal transmission is very fast
Nerve impulses can be received by neurons, muscle cells, endocrine cells, and exocrine cells
Feedback control: maintains the internal environment in many animals
Animals manage their internal environment by regulating or conforming to the external environment
Regulator: uses internal control mechanisms to moderate internal change in the face of external, environmental fluctuation
Conformer: allows its internal condition to vary with certain external changes
Animals may regulate some environmental variables while conforming to others
Set point: normal value for controlled variable
Sensor: monitors particular variable
Integrator: compares signals from the sensor to set point
Effector: compensates for deviations between actual value and set point
Example: body temperature in mammals
Organisms use homeostasis to maintain a
“steady state” or internal balance regardless
of external environment
Acclimatization: homeostasis can adjust to changes in external environment
Thermoregulation: adaptation to the thermal environment
Osmoregulation: adaptation to the osmotic environment
Excretion: strategies for the elimination of waste products of protein catabolism
Homeostatic processes for thermoregulation involve form, function, and behavior
Thermoregulation: the process by which animals maintain an internal temperature within a tolerable range
Endothermic animals: generate heat by metabolism; birds and mammals are endotherms
Ectothermic animals: gain heat from external sources ectotherms include most invertebrates, fishes, amphibians, and nonavian reptiles
In general, ectotherms tolerate greater variation in internal temperature, while endotherms are active at a greater range of external temperatures
Endothermy is more energetically expensive than ectothermy
Heat regulation in mammals often involves the integumentary system: skin, hair, and nails
Five adaptations help animals thermoregulate:
insulation = skin, fur, feathers, blubber
circulatory adaptations= vasodilation and vasoconstriction
cooling by evaporative heat loss
behavioral responses
adjusting metabolic heat production
In winter, many animals bask in the sun or on warm rocks.
In summer, many animals burrow or move to damp areas.
Some animals migrate to more suitable climates.
Thermoregulation is controlled by a region of the brain called the hypothalamus
The hypothalamus triggers heat loss or heat generating mechanisms
Fever is the result of a change to the set point for a biological thermostat
Negative feedback: the variable being regulated brings about responses that move the variable in the opposite direction
ex: Decrease in body temperature leads to responses that increase body temperature
May occur at cellular or molecular level
Also prevents homeostatic responses from overcompensating
Positive feedback: reinforces the direction of change
Far less common
Accelerates a process
Explosive system
ex: Birth in mammals
Feedforward regulation: animal’s body begins preparing for a change in some variable before it occurs
Anticipatory
Speeds up homeostatic responses and minimizes deviations from the set point
Many result from or are modified by learning