chapter 33: animal body- basic form and function

homeostasis

process by which organisms maintain a relatively stable internal environment, in humans, body temperature, blood pH, and glucose concentration are each maintained at a constant level

homeostasis factors

-organisms are open systems - constant exchange of materials with environment.

-organisms' energy requirements

-homeostatic processes involve: physical adaptations, behavior, physiology

bioenergetics

overall flow and transformation of energy in an animal, determines how much food an animal needs and it relates to an animal's size, activity, and environment

basal metabolic rate

average amount of energy used by an organism in a non-active state

torpor

physiological state in which activity is low and metabolism

decreases, enables animals to save energy while avoiding difficult and dangerous conditions

hibernation

long-term torpor that is an adaptation to winter cold and food scarcity

estivation

enables animals to survive long periods of high temperatures and scarce water

mechanisms of homeostasis

for a given variable, fluctuations above or below a set point serve as a stimulus; these are detected by a sensor and trigger a response, the response returns the variable to the set point

negative feedback

a primary mechanism of homeostasis, whereby a change in a physiological variable that is being monitored triggers a response that counteracts the initial fluctuation

positive feedback

feedback that tends to magnify a process or increase its output (pregnancy)

acclimatization

physiological adjustment to a change in an environmental factor, homeostasis adjusts

thermoregulation

must maintain a relatively constant internal temperature to keep enzymes efficient and avoid denaturation, controlled by the hypothalamus

heat exchange

radiation, convection, conduction, evaporation

integumentary system

skin, hair, nails is used for heat regulation

5 adaptations help animals thermoregulate

-insulation

-behavioral responses

-circulatory adaptations

-cooling by evaporative heat loss

-adjusting metabolic heat production

insulation

major thermoregulatory adaptation in mammals and birds, skin, feathers, fur, and blubber reduce heat flow between an

animal and its environment, very important in marine animals like walruses and whales

circulatory adaptations

regulation of blood flow near the body surface significantly affects thermoregulation, many endotherms and some ectotherms can alter the amount of blood flowing between the body core and the skin

vasodilation

blood flow in the skin increases, facilitating heat loss

vasoconstriction

blood flow in the skin decreases, lowering heat loss

concurrent exchange

countercurrent heat exchangers transfer heat between fluids flowing in opposite directions and thereby reduce heat loss, found in many marine animals, birds, and endothermic insects

cooling by evaporative heat loss

many types of animals lose heat through evaporation of water from their skin, sweating or bathing moistens the skin, helping to cool an animal down, panting increases the cooling effect in birds and many mammals

behavioral responses

both endotherms and ectotherms use behavioral responses to control body temperature, some terrestrial invertebrates have postures that minimize or maximize absorption of solar heat, honeybees huddle together during cold weather to retain heat

adjusting metabolic heat production

some animals adjust their rate of metabolic heat production by increasing their muscle activity such as moving or shivering, that generates heat

nonshivering thermogenesis

takes place when hormones cause mitochondria to increase their metabolic activity

acclimatization in thermoregulation

birds and mammals can vary their insulation to acclimatize to seasonal temperature changes, when temperatures are subzero, some ectotherms produce "antifreeze" compounds to prevent ice formation in their cells

fever

a response to some infections, reflects an increase in the normal range for the biological thermostat

endothermic animals

generate heat by metabolism; birds and mammals are endotherms

ectothermic animals

gain heat from external sources; ectotherms include most

invertebrates, fishes, amphibians

endotherms

can maintain a stable body temperature even in the face of large fluctuations in environmental temperature, endothermy is more energetically expensive than ectothermy

4 main types of animal tissues

epithelial, connective, muscle, nervous

epithelial tissue

line cavities, open spaces, and surfaces

classified by number of layer and shape of the cell

single layer = simple

multiple layers = stratified

single layer of cells of varying length = pseudostratified

connective tissue

connect tissues together and provides support, consist of cells (fibroblasts) embedded in a non-cellular matrix, contains some combination of collagen, elastic, or reticular fibers

muscle tissue

generates movement, 3 kinds of muscle tissue:

skeletal - voluntary, striated

smooth - involuntary, no striations

cardiac - involuntary, striated, intercalated discs

nervous tissue

generate and send electrical signals, functions in the receipt, processing, and transmission of information

neuron

nerve cell, a specialized cell transmitting nerve impulses

glial cell

support cells in the nervous system in which different types of glial cells perform distinct roles in the nervous system, outnumber neurons (10 to 1) in the brain, fulfill many vital functions, most brain tumors caused by mutations in glia

dendrites

neural input region that receives informationfrom other neurons, branch-like structures

soma (cell body)

integrates information coming from dendrites; houses basic cellular architecture (nucleus, etc.), big role in electrical communication, regulates cell function, integrates information from all dendrites by summing the electrical signals generated there

axon

long projection leading away from the soma,information integrated by the soma is relayed down the axon, primary output communication that carries action potential

axon terminals

the very end of the axon, contacts the dendrites of other neurons to pass information along, electrical to chemical communication

astrocytes

help form semi-permeable Blood Brain Barrier by contacting blood vessels, convey nutrients from the blood to neurons, help maintain homeostasis in the extracellular environment, minor role in cleaning up some extracellular debris

oligodendrocytes

create myelin that wraps around axon inside the brain and spinal cord, central nervous system

schwann cells

create myelin that wraps around axon outside the brain and spinal cord, peripheral nervous system

microglia

protect the brain by scavenging for pathogens, damaged cells, and other debris, acts as brain's mini immune system

ependymal cells

form the barrier around ventricles and channels containing cerebrospinal fluid (CSF), contain Cilia, hairlike projections that can move to help CSF flow

neuron communication

signals are possible because each neuron has a charged cellular membrane (a voltage difference between the inside and the outside), the charge of this membrane can change in response to neurotransmitter molecules released from other neurons and environmental stimuli

chemical synapse

depolarization causes voltage-gated Ca2+ channels to open calcium ions initiate a signaling cascade that causes synaptic vesicles, containing neurotransmitter molecules, to fuse with the presynaptic membrane, fusion of a vesicle with the presynaptic membrane causes neurotransmitter to be

released into the synaptic cleft, once neurotransmission has occurred, the neurotransmitter must be removed from the

synaptic cleft so the postsynaptic membrane can "reset" and be ready to receive another signal