Animal Structure, Function, and Organization (10%)

Thermostatic Function of the Hypothalamus

(also controls circadian clock). Group of nerve cells in hypothalamus function as thermostat, responding to body temperatures outside the normal range by activating mechanisms that promote heat loss or gain.

Chemical Synapse

1.) An action potential arrives, depolarizing presynaptic membrane. 2.) Depolarization opens voltage-gated channels, triggering influx of Ca2+ 3.) Elevated Ca2+ concentration causes synaptic vesicles to fuse with the presynaptic membrane, releasing neurotransmitter into the synaptic cleft. 4.) The neurotransmitter binds to the ligand-gated ion channels in the postsynaptic membrane. Binding triggers opening, allowing Na+ and K+ to diffuse through.

Two Mechanisms of Terminating Neurotransmission

1.) Enzymatic breakdown of neurotransmitter at synaptic cleft. 2.) Reuptake of neurotransmitter by presynaptic neuron.

Myosin-actin Interactions Underlying Muscle Fiber Contraction

1.) Myosin head bound to ATP and is in its low energy configuration 2.) Myosin head hydrolyzes ATP to ADP and P, and is in its high-energy configuration 3.) Myosin head binds to actin, forming a cross bridge with the thin filament 4.) Myosin couples release of ADP and P to a power stroke that slides the thin filament along the myosin and returns the myosin head to a low energy state. 5.) Binding of new molecule of ATP releases the myosin head from actin and a new cycle begins

Fixed Action Pattern

A sequence of unlearned acts directly linked to a simple stimulus. Fixed action patterns are essentially unchangeable and, once initiated, are usually carried to completion. Trigger for the behavior is an external cue called a SIGN STIMULUS, such as a red object that prompts the male stickleback's aggressive behavior (red belly of other males acts as a sign stimulus for attack).

Associative Learning

Ability to associate with an environmental feature (such as a color) with another (such as a foul taste). Well suited for lab study! Animals learn to link many pairs of features of their environment, but not all. Pigeons can associate danger with a sound but not with a color.

Behavioral Rhythms

Although the circadian clock plays a small but significant role in navigation by some migrating species, it has a major role in the daily activity of all animals. Behavioral rhythms linked to the yearly cycle of seasons are circannual rhythms (potentially migration or reproduction, but these also correlate with availability)

Bioenergetics

Animals use chemical energy harvested from food they eat to fuel metabolism and activity. Food digested by enzymatic hydrolysis and nutrients absorbed by cells. ATP produced by cellular respiration (and fermentation) powers cellular work, enabling cells, organs, tissues, and organ systems to perform the functions that keep an animal alive. Other uses of energy in form of ATP= biosynthesis (body growth, and repair), synthesis of storage material (fat), and production of gametes. Production and use of ATP generates heat which animal eventually gives off to surroundings. Oxygen consumption= heat through cellular respiration.

Genetic Basis of Behavior

Antidiuretic Hormone (ADH) or vasopressin- peptide released during mating and binds to a specific receptor in the central nervous system (forms pair bonds in mated voles). When male prairie voles are given a drug that inhibits the receptor in the brain that detects vasopressin, male voles fail to form a pair bond after mating.

Interaction of Muscles and Skeletons in Movement

Back and forth movement of a body part is generally accomplished by antagonistic muscles. This arrangement works with either an internal skeleton, as in mammals, or an external skeleton as in insects.

Neurons

Basic units of nervous system. Receives nerve impulse from other neurons via cell body and multiple extensions called dendrites. Transmit impulses to other neurons, muscle cells, or other cells via extensions called axons (bundled together into nerves).

Altruism

Behavior that reduces an animal's individual fitness but increases fitness of other individuals in the population. High pitched alarm call of Belding's ground squirrel (alerts population of incoming hawk but makes that individual a target for attack). Honeybee societies with sterile workers labor on behalf of a single, fertile queen, even stinging intruders (causing their own death) despite not being able to reproduce on their own. Naked mole rats have a colony with one queen and 2-3 king mice. The rest are nonreproductive males/females who sacrifice themselves to protect king and queen from predators. *Altruism maintained by evolution even though it doesn't enhance the survival or reproductive success of the self-sacrificing individuals-ie parents sacrificing for offspring*

Closed Circulatory System

Circulatory fluid (blood) is confined to vessels and is distinct from interstitial fluid. One or more hearts pumps blood into large vessels that branch into smaller ones that infiltrate the tissues and organs. Chemical exchange occurs between the blood and interstitial fluid, as well as between the interstitial fluid and body cells. Annelids (earthworms), cephalopods (squid, octopus), and all vertebrates have closed circulatory systems. Higher blood pressure than open system, more effective delivery of O2 and nutrients.

Cognition and Problem Solving

Cognition- process of knowing that involves awareness, reasoning, recollection, and judgement. Y shaped maze experiment proved abstract thinking in honeybees. *bees were trained in a color maze and could complete pattern mazes (maze where they follow one color, translated to a maze where they followed openings with the same pattern, like vertical lines) Problem solving- cognitive activity of devising a method to proceed from one state to another in the face of real or apparent obstacles. Most learned behaviors develop over short period of time, but some require gradual learning (bird songs learned in stages). Social learning= copying of behaviors (chimps cracking nuts)

Acetylcholine

Common neurotransmitter in vertebrates/invertebrates. Vital for nervous system function, muscle stimulation, memory formation, and learning. 2 major classes- 1.) Ligand-gated ion channel, 2.) G protein coupled receptor.

Cuboidal Epithelium

Cuboidal epithelium- dice shaped, specialized for secretion (kidneys, thyroid, salivary gland).

Intercellular Communication by Secreted Molecules Pt. 2

D.) Synaptic signaling- neurotransmitters diffuse across synapses and trigger responses in cells of target tissues (neurons, muscles, glands) E.) Neuroendocrine signaling- neurohormones diffuse into the bloodstream and trigger responses in target cells anywhere in the body.

Fibrous Connective Tissue

Dense with collagenous fibers. Found in tendons, which attach muscles to bones, and in ligaments which connect bones to joints.

Game Theory

Developed by American mathematician John Nash. Evaluates alternative strategies in situations where the outcome depends on these strategies of all individuals involved. Side blotched lizard (yellow, orange, or blue throat males). Each color associated with a different pattern of behavior and all favored by evolution for different reasons. Orange-most aggressive defend large territories with many females Blue- defend smaller territories and fewer females Yellow- mimic females and use sneak tactics to gain chance to mate. Mating success of each male influenced by abundance of other types of males, an example of FREQUENCY-DEPENDENT SELECTION.

Variation in Prey Selection

Diet and food preference can be genetically determined. Western garter snake in California (coastal individuals prefer banana slugs, whereas inland prefer frogs). In a lab- offspring of coastal mothers would prefer banana slugs as well (but not inland snakes).

Sliding Filament of Muscle Contraction

Each individual muscle fiber is a single cell. Within are multiple nuclei, each derived from one of the embryonic cells that fuse to the fiber. Surrounding nuclei are longitudinal myofibrils which consist of bundles of thin and thick filaments. Myofibrils in muscle fibers are made up of repeating sections called sarcomeres, which are basic contractile units of skeletal muscle. *Purple are thick myosin filaments *thin (actin) orange filaments remain the same as a sarcomere shortens and muscle fiber contracts

Regulatory Proteins and Calcium in Muscle Fiber Contraction

Each thin filament consists of two strands of actin, two long molecules of tropomyosin and multiple copies of troponin complex. Tropomyosin- regulatory protein in a muscle fiber at rest Troponin complex- set of additional regulatory proteins, are bound to actin strands of the thin filaments. Tropomyosin covers the myosin-binding sites along the thin filament, preventing actin and myosin from interacting.

Skeleton Types Pt. II

Endoskeleton: Animals ranging from sponges to mammals have a hardened internal skeleton buried within soft tissue. Sponges consist of hard, needle like structures of inorganic material or fibers made of protein. Echinoderms' (sea urchins, sea stars) bodies are reinforced by ossicles, hard plates composed of magnesium carbonate and calcium carbonate.

Migration

Environmental stimuli trigger behaviors and also provide cues that animals use to carry out those behaviors. Migration is a regular, long distance change in location guided by environmental cues. *sun, stars, magnetic fields*

Four Main Types of Tissue

Epithelial, connective, muscle, and nervous.

Spatial Learning

Establishment of a memory that reflects the environments spacial structure. In some animals spatial learning involves formulating a cognitive map, a representation in an animal's nervous system of the spatial relationships between objects in its surroundings.

Imprinting

Establishment of long lasting behavioral response to a particular individual or object. Can take place only during a specific time period in development (sensitive period).

Male Competition for Mates

Female choice selects for one best type of male, and results in low variation among males. Male competition for mates can reduce variation among males as well. Agonistic behavior- ritualized contest for mate/food.

Sexual Selection Influenced by Imprinting

Female zebra finch chicks that imprinted on ornamented fathers (fake ornament, zebra finches naturally do not have) preferred ornamented males as adult mates, males showed no preference. Females raised by a parent with no crest showed no preference in a mate. Mate-choice copying- individuals in a population copy the mate choice of others (guppies). When no other females present a female will choose an orange male, when another female is present she wants to mate with the male chosen by that female.

Epinephrine

Fight or flight hormone- produces different responses in different targeted cells.

Excretory Systems: Protonephridia

Flatworms lack coelom or body cavity, use these systems. Network of dead end tubules that branch throughout body. Cellular units called flame bulbs cap branches of each protoneprhidium. 1.) Drawn by beating cilia, interstitial fluid filters through the membrane where the cap cell and tubule cell interlock. 2.) Filtrate empties into external environment

Foraging

Food obtaining behavior. Variation of a gene dictates how far fruit fly larvae travel when foraging. On average, larvae carrying the allele (for^r gene) traveled nearly twice as far while foraging as do the larvae with the for^s (sitter allele). Optimal foraging- natural selection should favor a foraging behavior that minimizes the cost of foraging and maximizes the benefits.

Forebrain, Midbrain, & Hindbrain in Vertebrates

Forebrain- contains olfactory. bulb and cerebrum: processes smells, regulates sleep, learning, and any complex processing Midbrain- Coordinates routing of sensory input Hindbrain- part of which forms cerebellum controls involuntary activities such as blood circulation, and coordinates motor activities (locomotion).

Forms of Animal Communication

Fruit-fly courtship=stimulus response chain, response to each stimulus is itself the stimulus for the next behavior. Honey bee dance language. Pheromones- animals that communicate through odors or tastes emit these chemical substances. Can also serve as alarm signals (ie. injured fish skin can release a substance inducing a fright response in other fish)

Gas Exchange

Gas undergoes net diffusion from where its partial pressure is higher to where it is lower. Air is more conducive to gas exchange than water due to higher O2 content, lower density, and lower viscosity.

Thermoregulation

Heat comes from internal metabolism or external environment. Mammals/birds are ENDOTHERMIC (generate heat via metabolism). Regulators! Reptiles, fish, invertebrates are EXOTHERMIC (gain heat from external sources). Conformers! Adjust temps via behavioral means. Because heat source is largely environmental, ectotherms consume much less food (tolerate fluctuations in internal temps better than endotherms). *Not exclusive, ie. mammal/bird can warm themselves in sun*

Glia in the Vertebrate Nervous System

In embryos, two types of glia play essential roles in the development of the nervous system: radial glia and astrocytes. Radial glia- form tracks along which newly formed neurons migrate from neural tube, the structure that gives rise to the CNS. Astrocytes- adjacent to brain capillaries participate in formation of blood-brain barrier, a physiological mechanism that restricts the entry of many substances from the blood into the CNS.

Transport Epithelia

In most animals, osmoregulation and metabolic waste removal rely on transport epithelia. One or more layers of epithelial cells specialized for moving particular solutes in controlled amounts in specific directions. Arranged in tubular networks with extensive surface area. Some transport epithelia face the outside environment directly. *Enable albatross and other marine birds to survive on seawater

Schwann Cells and Myelin Sheath

In the PNS, glia called schwann cells wrap themselves around axons, forming layers of myelin. Gaps between adjacent schwann cells are called nodes of Ranvier. Myelin sheath- electrical insulation of vertebrate axons. produced by glia: OLIGODENDROCYTES in the CNS, and Schwann cells in the PNS!!

Experience and Behavior

Innate behavior- developmentally fixed Cross-fostering study- young of one species placed in care of adults from another species in same or similar environment (the extent to which offspring behavior changes in such a situation provides a measure of how the social and physical environment influences behavior). Twin study- researchers compare behavior of twins raised together and raise apart (instrumental in studying disorders that alter behavior- anxiety, alcoholism) Learning- modification of behavior as a result of specific experiences. Depends on nervous system organization established during development following instructions encoded in the genome. Changes to neuronal connectivity=formation of memories

Smooth Muscle

Lacks striations, is found in walls of digestive system, bladder, arteries, and other internal organs. Cells are spindle shaped, responsible for involuntary body activities (churning of stomach, constriction of arteries).

Metabolic Rate and Size

Larger animals have more body mass and require more chemical energy. Body mass to the 3/4 power=metabolic rate. M^(3/4) It takes energy to maintain each gram of body mass (inversely related to body size). Each gram for a mouse, requires 20x as many calories as a gram of an elephant, even though elephant uses far more calories. Smaller animals=higher metabolic rate per gram demands a higher rate of oxygen delivery. (ie. smaller animals have higher breathing rate, blood volume, and heart rate).

Reciprocal Altruism

Like in unrelated humans, favors or exchange aid adaptive if the aided individual returns favor in the future.

Blood Tissue

Liquid extracellular matrix called Plasma, consists of water, salts, and dissolved proteins. Suspended in plasma are erythrocytes (red blood cells), and leukocytes (white blood cells), and cell fragments called platelets. Red cells carry oxygen, white cells function in defense, and platelets aid in clotting.

Mating Systems and Parental Care

Male that stays with and helps a single mate may ultimately have more viable offspring than it would by seeking additional mates. (ie. why many birds are monogamous). In birds with young that can feed for themselves almost immediately after hatching, males will maximize reproductive success by mating with many partners. In mammals the mother is the only one that can care for the young (lactating females), males usually play no role in raising young. However, males may offer protection but will have a harem (gorillas, lions).

Osmoregulation Marine Animals

Marine- No substantial challenges in water balance, but still actively transport solutes to establish levels in hemolymph (circulatory) different than external. Internal salt concentration lower than ocean. Salt diffuses from water into their bodies (across gills). Bony fish (cod)- lose water constantly via osmosis. They balance water loss by drinking a lot of sea water. The excess salt ingested with seawater are eliminated via gills and kidneys Sharks (high urea build up can denature proteins)- TMAO organic molecule protects proteins from denaturing effect of urea. TMAO also functions in osmoregulation of sharks. Sharks do not drink, water slowly enters body via osmosis and food

Mating Systems and Sexual Dimorphism

Monogamous, polygamous. Polygamous= 1.) Polygyny- single male and many females 2.) Polyandry- single female and multiple males Sexual dimorphism- extent to which males and females differ in appearance typically varies with the type of mating system. In monogamous species males and females look very similar. Polygamous species the sex that attracts the multiple mating partners is typically showier and larger than the opposite sex.

Motor Units in a Vertebrate Skeletal Muscle

Motor unit- single motor neuron and all the muscle fibers it controls. When a motor neuron produces action potential, all the muscle fibers in its motor unit contract as a group. Strength of contraction depends on how many muscle fibers the neuron controls.

Fast Twitch and Slow Twitch Fibers

Muscle fibers vary in the speed with which they contract: fast twitch develop tension two to three times faster than slow twitch fibers. Speed difference reflects rate at which myosin heads hydrolyze ATP. Most human skeletal muscles have both types, although the eye and hand muscles are fast twitch ONLY. Cardiac muscle- found in heart, striated like skeletal muscle. Smooth muscle- found in walls of hollow organs (vessels/tracts of circulatory, digestive, and reproductive system). Lacks striation due to actin/myosin filaments not regularly arrayed along length of the cell.

Glia in Mammalian Brain

Neurons of vertebrates and most invertebrates require supporting cells called glial cells, or glia (meaning glue). Glia outnumber neurons 10-50 fold. Glia nourish neurons, insulate axons of neurons, and regulate extracellular fluid surrounding neurons.

Feedback Circuits Regulate Digestion

Nutrition is regulated at multiple levels, food intake triggers nervous and hormonal responses that cause secretion of digestive juices and promote movement of ingested material through the canal. Insulin and glucagon control synthesis and breakdown of glycogen, thereby regulating glucose availability. Vertebrates store excess calories in glycogen (in liver and muscle cells) and in fat (in adipose cells). Diabetes 1- Can't produce insulin Diabetes 2- Insulin inhibited from picking up glucose, so blood glucose remains elevated.

The Structure of Skeletal Muscle

Physical interaction of protein filaments is required for muscle function. Thin filaments- globular protein actin. Two strands of polymerized actin are coiled around one another. Thick filaments- staggered arrays of myosin molecules. Muscle contraction is result of filament movement powered by chemical energy, muscle extension occurs only passively. Skeletal muscle moves bones and body. Typical skeletal muscle is a bundle of fibers running along length of muscle.

Thyroid Regulation: Hormone Cascade Pathway

Regulates bioenergetics: blood pressure, heart rate, muscle tone, digestive and reproductive functions.

Osmoregulation

Regulating chemical composition of body fluids depends on balancing uptake and loss of water and solutes. Homeostasis requires osmoregulation. Structurally and functionally linked to excretion. Water enters and leaves cells via osmosis, which occurs when two solutions separated by a membrane differ in total solute concentration. Unit of measurement for solute concentration= OSMOLARITY (#of moles of solute per liter of solution). Hyperosmotic, hypoosmotic, and isoosmotic

Chemical Digestion in the Stomach

Saliva contains amylase-enzyme breaks down starch and glycogen. Esophagus and trachea meet at pharynx (throat region). Stomach secretes gastric juice and mixes with food via churning. Mixture is called chyme. Gastric juice composed of HCl (very acidic pH of 2, can digest nails!) Low pH denatures proteins. Protease (second component of gastric juice)- or protein digesting enzyme called pepsin. Cleaves proteins into smaller polypeptides. Pepsinogen is inactive form of pepsin. Pepsinogen + HCl => Pepsin

Sexual Selection and Mate Choice

Sexual dimorphism results from sexual selection, a form of natural selection in which differences in reproductive success among individuals are a consequence of differences in mating success. Intersexual selection- members of one sex choose mates based on the characteristics of the other sex (courtship songs). Mate preferences of females may play a central role in the evolution of male behavior and anatomy. (stalk eyed flies, peacocks, songbirds) Intrasexual selection- involves competition between members of one sex for mates

Simple Squamous Epithelium

Simple squamous epithelium- Single layer of plate like cells that function in exchange of material by diffusion. Thin/leaky-lines blood vessels and air sacs of lungs (diffusion critical).

Skeleton Types

Skeletal systems: Hydrostatic- consists of fluid held under pressure in a closed body compartment. Main type of skeleton in most cnidarians, flatworms, nematodes, and annelids. Exoskeleton- Hard covering deposited on an animal's surface. Shells of clams/molluscs. Insects and arthropods have a jointed exoskeleton called a cuticle, a coat secreted by epidermis. 30-50% of cuticle consists of chitin, a polysaccharide similar to cellulose. Cuticle may be hardened with organic compounds.

Stratified Squamous Epithelium

Stratified squamous epithelium- multilayered, regenerates rapidly. New cells formed by division near the basal surface push outward replacing cells that sloughed off. Outer skin/lining of mouth, anus, and vagina.

Parasympathetic and Sympathetic Divisions

Sympathetic division- corresponds to arousal and energy generation (fight or flight). Heart beats faster, digestion inhibited, liver converts glycogen to glucose, adrenal medulla secretes epinephrine (adrenaline) Parasympathetic- Activation causes opposite responses that promote calming and a return to self-maintenance.

Roles of Sarcoplasmic Reticulum

Synaptic terminal of motor neuron releases acetylcholine, which depolarizes the plasma membrane of the muscle fiber. The depolarization causes action potentials to sweep across the muscle fiber and deep into it along the transverse tubules. The action potentials trigger the release of calcium from the sarcoplasmic reticulum into the cytosol. Calcium initiates the sliding of filaments by allowing myosin to bind to actin.

Coefficient of Relatedness

The benefit, B, is the average number of extra offspring that the recipient of an altruistic act produces. The cost, C, is how many fewer offspring the altruistic individual produces. The Coefficient of relatedness, r, equals the fraction of genes that, on average, are shared. Natural selection favors altruism when the benefit to the recipient multiplied by the coefficient of relatedness exceeds the cost to the altruist. *when rB > C this is called Hamilton's rule (meaning natural selection favors this altruistic act). *Natural selection that favors altruism by enhancing reproductive success of relatives is called KIN SELECTION

Evolution of Hormone Function

Thyroid hormone plays a role across many evolutionary lineages in regulating metabolism. In frogs, stimulates reabsorption of tadpole's tail during metamorphosis.

Torper/Hibernation

Torper: physiological state of decreased activity/metabolism. Daily torper in small birds/mammals (ie. chickadees/hummingbirds torper on a cold night, while a bat torpers during the day). When active they have high metabolic rates and very high rates of energy consumption. Hibernation: long term torper adaptation to winter cold/food scarcity.

Inclusive Fitness

Total effect an individual has on proliferating its genes by producing its own offspring and by providing aid that enables other close relatives to produce offspring.

Types of Feeders

Types of feeders: 1.) Filter Feeding- strain small organisms or food particles from surrounding medium (whales and other aquatic animals). 2.) Substrate Feeding- animals that live in or on their food source (maggots, caterpillars) 3.) Bulk feeding- (most animals including humans) eat large pieces of food. Adaptations include claws, venomous fangs, pincers, tentacles, jaws, and teeth. 4.) Fluid feeding- suck nutrient rich fluid from a living host (tsetse fly, mosquito, aphids are fluid feeders of plants). Some fluid feeders (hummingbirds and bees) benefit host (ie. pollination).

Glia

Various types of glia help nourish, insulate, and replenish neurons and in some cases modulate neuron function.

Ventricles, Gray Matter, and White Matter

Ventricles deep in the brain's interior contain cerebrospinal fluid. Most of the gray matter is on the brain surface, surrounding the white matter.

Adaptations of Digestive System Correlates with Diet

Vertebrate digestive systems display many evolutionary adaptations associated with diet. Assortment of teeth (carnivore, omnivore, herbivore). Herbivores have fermentation chambers (mutualistic microorganisms digest cellulose). Herbivores have longer alimentary canals due to longer time required to digest vegetation.

Excretory Systems: Metanephridia

*Osmoregulatory and excretion function Annelids (earthworms) use this. Excretory organs that collect fluid directly from coelom. A pair of metanephridia are found in each segment of an annelid, where they are immersed in coelomic fluid and enveloped by capillary network. Earthworms inhabit damp soil and experience uptake of water by osmosis through skin. Metanephridia balance water influx by producing dilute urine (hypo osmotic to body fluids).

Conduction of an Action Potential

*Propagate more rapidly in myelinated axons because the time-consuming process of opening and closing ion channels occurs at a limited number of positions along the axon. This is called SALTATORY CONDUCTION.

Excretory System Function Overview

1.) Filtration- excretory tubule collects a filtrate from the blood. Water and solutes are forced by blood pressure across the selectively permeable membranes of a cluster of capillaries and into the excretory tubule. 2.) Reabsorption- the transport epithelium reclaims valuable substances from the filtrate and returns them to the body fluid. 3.) Secretion- other substances such as toxins and excess ions, are extracted from body fluids and added to contents of excretory tubule. 4.) Excretion- altered filtrate (urine) leaves system and body.

Coordination of Endocrine and Nervous System: Invertebrates

1.) Neurosecretory cells in brain produce PTTH hormone, which is stored in corpora cardiac until release. 2.) PTTH signals its main target organ, the prothoracic gland, to produce hormone ecdysteroid. 3.) Ecdysteroid secretion from the prothoracic gland is episodic, with each release stimulating a molt. 4.) Juvenile hormone (JH) secreted by corpora allot determines result of molt. High concentrations, JH suppresses metamorphosis.

Kidneys: The Nephron and Collecting Duct

1.) Proximal tubule- reabsorption in proximal tubule is critical for recapture of ions, water, and nutrients. 2.) Descending limb of loop of henle- upon leaving proximal tubule, filtrate enters loop of hence, which further reduces filtrate volume via distinct stages of water and salt movement. *numerous water channels formed by aquaporins, proteins making membrane permeable to water. 3.) Ascending limb- filtrate reaches tip of the loop and then returns to the cortex in the ascending limb. Unlike descending, has transport epithelium that LACKS aquaporins/water channels. 4.) Distal tubule- regulates K+ and NaCl concentration of body fluids. 5.) Collecting duct- processes filtrate into urine, carries to the renal pelvis. As filtrate passes along transport epithelium of collecting duct, hormonal control of permeability and transport determines extent to which urine becomes concentrated.

Generation of Action Potentials

1.) Resting state- the gated Na+ and K+ channels are closed (ungated channels maintain resting potential). 2.) Depolarization- a stimulus opens some sodium channels. Na+ inflow through those channels depolarizes membrane. If the depolarization reaches threshold, it triggers action potential. 3.) Rising phase of action potential- depolarization opens most sodium channels while the potassium channels remain closed. Na+ influence makes the inside of the membrane positive with respect to the outside. 4.) Falling phase of action potential- most sodium channels become inactivated, blocking Na+ inflow. Most potassium channels open, permitting K+ outflow which makes inside of cell negative again. 5.) Undershoot- sodium channels close but some potassium channels still open. As these channels close and sodium channels become unblocked membrane returns to resting state.

Intercellular Communication by Secreted Molecules

A.) Endocrine signaling- secreted molecules diffuse into the blood stream and trigger responses in target cells anywhere in the body. B.) Paracrine signaling- secreted molecules diffuse locally and trigger a response in neighboring cells C.) Autocrine Signaling- secreted molecules diffuse locally and trigger a response in cells that secrete them.

Voltage-gated Ion Channel

Action potentials are signals conducted by axons. Change in membrane potential in one direction opens voltage gated channel. Opposite change, closes channel. Hyperpolarization- increase in membrane potential (makes inside of membrane more negative) Depolarization- decrease in membrane potential (often involves gated sodium channels).

Stress and Adrenal Gland

Adrenal hormones respond to stress. 2 parts: 1.) Adrenal Medulla- "Fight or flight response" triggers release of epinephrine (adrenaline), and norepinephrine. Both synthesized from amino acid tyrosine (and both are neurotransmitters). 2.) Adrenal cortex- becomes active under stressful conditions like low blood sugar, decreased blood volume/pressure, and shock. ACTH hormone released, stimulates endocrine cells to synthesize and secrete a family of steroids called corticosteroids (2 types). A.) Glucocorticoids (cortisol)- make more glucose available as fuel (break down muscles into amino acids) B.) Mineralocorticoids- maintain salt/water balance.

Digestion in Small Intestine

Alimentary canal's longest compartment (small diameter). First 10 inches form the duodenum. Chyme from stomach mixes with digestive juices from pancreas, liver, and gallbladder (as well as gland cells from intestinal wall itself). *Hormones released by stomach and duodenum control digestive secretions into the alimentary canal* Chyme in duodenum triggers release of hormone secretin, stimulates pancreas to secrete bicarbonate (neutralizes acidity of chyme and acts as a buffer for chemical digestion in small intestine). Fats hard to digest (insoluble with water)- fat digestion facilitated by bile salts, which act as emulsifiers that break apart fat and lipid globules. Bile secreted by liver and stored in gallbladder. Bile also destroys defunctive red blood cells.

Lung Ventilation

Amphibians ventilate lungs by positive pressure breathing, which forces air down trachea. Birds use a system of air sacs as bellows to keep air flowing through the lungs in one direction only. Mammals ventilate lungs by negative pressure breathing, which pulls air into lungs when the rib muscles and diaphragm contract. Incoming and outgoing air mix, decreasing efficiency of ventilation.

Double Circulation

Amphibians, reptiles, mammals, & birds have two circuits of blood flow. Both pumps in the heart. PULMONARY CIRCUIT= Right side of heart pumps oxygen poor blood to capillary beds of gas exchange tissues, where there is a net movement of O2 into blood and CO2 out. Gas exchange takes place in the lungs, in amphibians (pulmocutaneous circuit) as gas exchange happens in lungs and capillaries in the skin. SYSTEMIC CIRCUIT= left side of the heart pumping oxygen rich blood from gas exchange tissues to capillary beds in organs and tissues throughout the body. After exchange oxygen poor blood returns to heart to start pulmonary circuit. Double circulation= vigorous blood flow to brain, muscles, and other organs because heart depressurizes the blood after it passes through capillary beds of lungs or skin.

Anhydrobiosis

Animal enters dormant state when habitat dries up. Tardigrades can dehydrate to 2% water content and survive, dry as dust, for a decade or more. Just add water and they come back to life.

Nitrogenous Waste

Animals excrete via ammonia, urea, or uric acid. Ammonia- very toxic, can interfere with oxidative phosphorylation. Removed by enzymes. These animals need lots of water because ammonia tolerated only at low concentrations. Most aquatic species!! Lost via diffusion to the surrounding water. Urea- (mammals, amphibians, sharks, some bony fish) Ammonia so toxic it can only be transported and excreted in very dilute solutions. Urea is product of energy consuming metabolic cycle that combines ammonia with CO2 in liver. Advantage= low toxicity, Disadvantage= high energy cost. Tadpoles excrete ammonia, frogs secrete urea. Uric Acid- (Reptiles/birds/insects/snails)- Non toxic, doesn't readily dissolve in water, excreted as semi-solid paste with little water loss. Evolution/adaptation- dependent on environment. Tortoises excrete mainly uric acid (save water), but aquatic turtles secrete both urea and ammonia.

Circulatory System: Heart, arteries, veins

Arteries and veins distinguished by direction in which they carry blood (not by O2 content). Arteries carry blood away from the heart towards capillaries, and veins return blood towards the heart from capillaries. *exception- portal veins, carry blood between pairs of capillary beds. Hepatic portal vein carries blood between capillary beds in digestive system to the liver. Hearts of all vertebrates contain two or more muscular chambers. Chambers that receive blood are called ATRIA, chambers that pump blood out are called VENTRICLES.

Skeletal Muscle

Attached via tendons, skeletal muscle (aka. striated muscle), is responsible for voluntary movement. Bundles of long cells that are called muscle fibers. During development skeletal muscle fibers for by the futon of many cells, resulting in multiple nuclei in each muscle fiber. Sarcomeres (contractile units) along fibers gives the striated appearance. Building muscle increases size of fibers, but not the number.

Osmoregulation Freshwater Animals

Body fluids are hyperosmotic, body cannot tolerate salt concentrations as low as that of freshwater. Excrete large amounts of very dilute urine, and drink almost no water. Salts lost by diffusion and in the urine are replenished by eating and salt uptake across gills. *Salmon and other euryhaline fish that go between oceans and freshwater can adjust body to osmoregulate in both ways.

Central Nervous System

CNS- The neurons that carry information into and out of the CNS constitute the peripheral nervous system (PNS). When bundled together, axons of neurons form nerves. Neuron shape can vary from simple to complex such as interneurons (receive signals from tens of thousands of synapses). Neurons that transmit information to target cells have highly branched axons.

Roles of Parathyroid Hormone in Blood Calcium Levels

Ca2+ ions essential to normal functioning of cells, homeostatic control of blood calcium level is vital. When levels fall, parathyroid hormone released (PTH) which raises level of Ca2+ (causes mineral matrix of bone to break down and release Ca into bloodstream) In kidneys PTH stimulates reabsorption of Ca2+ through renal tubules. PTH indirectly raises blood Ca2+ by promoting production of vitamin D. PTH stimulates conversion of (food or sunlight) to active vitamin D in the liver.

Organization of Vertebrate Circulatory Systems

Cardiovascular system is often used to describe heart and blood vessels in vertebrates. Blood circulates to and from the heart through an elaborate network of vessels, the total length of blood vessels in an average human adult is 2x earth's circumference. Blood vessels= arteries, veins, capillaries. Arteries- carry blood from heart to organs. Within organs arteries branch into arterioles. Arterioles (small vessels) convey blood to capillaries. Capillaries- microscopic vessels with very thin, porous walls. Network of capillaries= capillary beds, infiltrate tissues. Across thin walls of capillaries gases and other chemicals exchanged by diffusion between blood and interstitial fluid around tissue cells. At downstream end capillaries converge into VENULES and venules converge into veins. Veins- vessels that carry blood back to the heart.

Cartilage Tissue

Collagenous fibers embedded in a rubbery protein-carb complex called chondroitin sulfate. Collagen (secreted by chondrocytes) and chondroitin sulfate make cartilage. Strong, yet flexible support material.

Large Intestine

Colon, cecum, and rectum (feces stored until it can be eliminated). Colon- leads to rectum/anus. Completes recovery of water. Cecum- ferments ingested material (especially in animals that eat lots of plants). Humans have a small cecum.

Pseudostratified Columnar Epithelium

Consists of a single layer of cells varying in height and the position of their nuclei. Forms mucous membrane in eukaryotic cells (lining portion of respiratory tract), the beating cilia sweep the film of mucus across surface.

Circadian Rhythm

Cyclic alterations in metabolism. Occur every 24 hours. Rise/fall of temp over 24 hour period. Can be slowly changed due to stimuli (jet lag to another time zone, light/dark..etc)

Simple Endocrine Pathway

Endocrine cells respond to a change in internal or external variable by secreting hormone molecules that trigger a specific response by target cells.

Signaling in Endocrine and Nervous System

Endocrine: Signaling molecules (hormones) released into bloodstream by endocrine cells are carried to all locations in body. Response limited to cells that have a receptor for the signal. Nervous: neurons transmit signals (nerve impulses) along dedicated routes connecting specific locations in the body. Fast, don't last long! Response limited to cells that connect by specialized junctions to an axon that transmits an impulse.

Exchange with Environment

Exchange surfaces are usually internal but are connected to the environment via openings on the body (ie. mouth). The exchange surfaces are finely branches or folded, providing more surface area. Digestive, respiratory, and excretory systems all have such exchange surfaces. Interstitial fluid- Spaces between cells are filled with this fluid. Complex body plans include circulatory fluid (blood), exchange between interstitial fluid and circulatory fluid enables cells throughout the body to obtain nutrients and get rid of waste.

Feedback Loops (Positive and Negative)

Feedback loop linking response back to an initial stimulus is a feature of many control pathways. Negative feedback- response reduces initial stimulus (ie. decreasing hormone signaling, negative feedback regulation prevents excessive pathway activity) Positive feedback- reinforces a stimulus. Oxytocin pathway (mammary glands, secrete milk in response to circulating oxytocin), release leads to more suckling and more stimulation. Activation of pathway sustained until baby stops suckling

Cardiac Muscle

Forms contractile wall of the heart. Striated like skeletal muscle and has similar contractile properties. Has branched fibers that interconnect via intercalated disks, which relay signals from cell to cell and synchronize heart contraction.

Kidneys

Functions for osmoregulation and excretion in vertebrates. Urine produced by each kidney exits through a duct called the ureter. The two ureters drain into urinary bladder. During urination, urine is expelled through a tube called the urethra. Kidney has outer renal cortex, and inner renal medulla. Supplied blood via renal artery and drained by a renal vein. Nearly all fluid in the filtrate is reabsorbed into the surrounding blood vessels and exits the kidney in the renal vein. Remaining fluid leaves excretory tubules as urine, collected in inner renal pelvis and exit kidney via ureter.

Nervous Tissue

Functions in receipt, processing, and transmission of information. Contains neurons (nerve cells) which transmit nerve impulses, as well as support cells called glial cells (glia). Concentration of nervous tissue= brain.

Appetite Regulating Hormones

Ghrelin- secreted by stomach wall, triggers feelings of hunger. Insulin- rise in blood sugar levels after a meal stimulates pancreas to create insulin. Suppresses appetite by acting on the brain. Leptin- produced by fat tissue, suppresses appetite. When body fat decreases leptin levels fall and appetite goes up. PYY- secreted by small intestine after meals, acts as an appetite suppressant to counter ghrelin.

Homeostatic Control of Breathing

Homeostatic: Sensors detect pH of cerebrospinal fluid (reflecting CO2 concentration in blood), and a control center in brain adjusts breathing rate and depth to match metabolic demands. Additional input to control center is provided by sensors in the aorta and carotid arteries that monitor blood levels of O2 an CO2.

Single Circulation

In sharks, rays, bony fishes blood travels through body and returns to its starting point in a single circuit. Heart has two chambers: atrium and ventricle. Blood entering heart collects in atrium before transfer to ventricle. Contraction of ventricle pumps blood to a capillary bed in the gills, where there is a net diffusion of O2 into the blood and of CO2 out of the blood. As blood leaves the gills the capillaries converge into a vessel that carries oxygen rich blood to capillary beds throughout body. In single circulation blood that leaves the heart passes through 2 capillary beds before returning. Blood pressure drops when flowing through capillary bed (drop of pressure in gills limits rate of blood flow for entire body)

Lung Pigments

In the lungs, gradients of partial pressure favor the net diffusion of O2 into the blood and CO2 out of the blood. The opposite situation exists in the rest of the body. Respiratory pigments such as hemocyanin and hemoglobin bind O2, greatly increasing the amount of O2 transported by circulatory system. Evolutionary adaptations enable some animals to satisfy extraordinary O2 demands. Deep-diving mammals stockpile O2 in blood and other tissues and deplete it slowly.

4 Stages of Food Processing

Ingestion- act of eating Digestion- Food broken down into particles small enough for absorption. Mechanical (chewing/grinding of food) and chemical processes required. Chemical necessary because animals cannot directly use proteins, carbs, fats, phospholipids and nucleic acids in food. Molecules too large to pass through cell membrane. Breakdown and assemble into what's needed. Absorption- animal cells absorb small molecules Elimination- undigested material leaves digestive system.

Malpighian Tubules

Insects and other terrestrial arthropods have these. Remove nitrogenous waste and function in osmoregulation. Extend from dead end tips immersed in hemolymph to openings in digestive tract. No filtration step. Instead transport epithelium that lines tubules secretes solutes, including nitrogenous waste, from hemolymph into lumen of tubule. Water follows the solutes into tubule by osmosis. As fluid passes from tubules into rectum, most solutes are pumped back into hemolymph, water reabsorption by osmosis follows. Nitrogenous waste eliminated as insoluble uric acid (very dry to conserve water).

Digestive Compartments

Intracellular digestion= Food vacuoles (hydrolytic enzymes break down food via cellular organelles). Phagocytosis, or pinocytosis (liquid). Newly formed vacuoles fuse with lysosomes. Extracellular digestion= breakdown of food via hydrolysis in compartments that are continuous with the outside of the animal's body. Enables animal to devour much larger pieces of food than phagocytosis. Gastrovascular cavity- simple body plan animals have a digestive compartment with single opening. Digests/distributes nutrients throughout body. (Cnidarians called hydras). Alimentary canals- animals with complex body plans, 2 openings (mouth and anus).

Feedback Control

Maintains internal environment in many animals. Regulator- uses internal mechanisms to control internal change in the face of external fluctuation (ie. sea otter regulates internal temp in cold water). Conformer- allows its internal condition to change in accordance with external changes (bass in cold water) Homeostasis altered by acclimatization- animals physiological adjustment to changes in external environment (ie. altitude change).

Bone Tissue

Mineralized Connective Tissue. Osteoblasts deposit a matrix of collagen. Calcium, magnesium, and phosphate ions combine into hard mineral within the matrix.

Loose Connective Tissue

Most widespread connective tissue. Binds epithelia to underlying tissues and holds organs in place. Loose weave of fibers (all 3 types). Found in skin/throughout body

Negative/Positive Feedback

Negative: Production of heat (ie. working out) reduces the stimulus. Nervous system detects and increases sweating to cool body via evaporation of sweat. Return to normal= elimination of stimulus. Plays a MAJOR role in homeostasis. Positive: Amplifies stimulus, not a major player in homeostasis. Drive processes to completion (ie. pressure of baby's head against sensors near opening of mother's uterus stimulates contraction)

Tracheal Systems in Insects

Network of air tubes that branch throughout body. Largest tubes, called tracheae, open to the outside. At the tips of the finest branches a moist epithelial lining enables gas exchange by diffusion. 1.) Air sacs formed from enlarged portions of tracheae are found near organs that require a large supply of oxygen. 2.) Rings of chitin keep tracheae open, allowing air to enter and pass into smaller tubes called tracheoles. Delivering air directly to cells throughout the body. Tracheoles have closed end filled with fluid. When animal is active and using more O2, most of the fluid is withdrawn into the body, increasing surface area of tracheoles in contact with cells.

Neuron Structure and Function

Neuron's organelles including nucleus are located in cell body. Cell body studded with numerous highly branched extensions called dendrites (greek for trees). Dendrites receive signals from other neurons. Neuron also has a single axon, an extension that transmits signals to other cells. Axons are often much longer than dendrites, and some, such as those that reach from giraffe spinal cord to feet are over a meter long. Cone shaped base of an axon= axon hillock (where signals that travel down axon are generated). Branched end of axon transmits information to another cell at a junction called a synapse. Part of each icon branch that forms this specialized junction is a synaptic terminal. Neurotransmitters (at most synapses)- chemical messengers pass information from neuron to receiving cell

Epithelial Tissue

Occurring as sheets of cells, epithelial tissues cover the outside of the body and line organs and cavities within the body. Closely packed with tight junctions, they function as a barrier against mechanical injury, pathogens, and fluid loss. Also form active interface with environment (i.e. epithelia in nose allows for smell). Epithelia are polarized- two different sides. Apical surface faces the lumen (cavity) or outside of organ, exposed to fluid or air. Opposite side is basal surface.

Heartbeat Signals

Originates with impulses at SA (sinoatrial) node (pacemaker)of the right atrium. They trigger atrial contraction, are delayed at the AV (atrioventricular) node, and are then conducted along the bundle branches and purkinje fibers, triggering ventricular contraction. Nervous system, hormones, and body temperature affect pacemaker activity.

Osmoregulators & Osmoconformers

Osmoconformer- to be isosmotic with surroundings. ALL osmoconformers are marine animals. Internal osmolarity same as external environment, no need to gain or lose water. Osmoregulator- Control internal osmolarity independent of external environment. Enables animals to live in environments that are uninhabitable for osmoconformers (freshwater/terrestrial habitats). In a hypoosmotic environment an osmoregulator must discharge excess water. In a hyperosmotic environment an osmoregulatory must take in water to offset loss.

Regulation of Fluid Retention in Kidney

Osmoreceptors in hypothalamus monitor blood osmolarity via its effect on net diffusion of water into or out of receptor cells. When blood osmolarity increases, signals from the osmoreceptors trigger release of ADH from posterior pituitary and generate thirst. Water reabsorption in collecting duct and water intake restore normal blood osmolarity, inhibiting further ADH secretion.

Respiratory Surfaces: Gills

Outfoldings of body surface that are suspended in water. Movement of respiratory medium over respiratory surface is a process called VENTILATION. Ventilation maintains partial pressure gradient of oxygen and CO2 across gill that are necessary for gas exchange. Most gill bearing animals move water over gills or move their gills through water. (ie. fish- current of water passes through mouth, passes through slits in pharynx, flows over gills and exits body due to motion of swimming). Countercurrent exchange- exchange of substance or heat between two fluids flowing in opposite direction. In a fish gill, the two fluids are blood and water. Blood flows in direction opposite of water passing over the gills, at each point in its travel blood is less saturated with O2 than the water it meets (high O2 diffuses across water lower O2 concentration of blood).

Local Regulators

Prostaglandins are modified fatty acids. Many other local regulators are polypeptides, including cytokines, which enable immune cell communication, and growth factors, which promote cell growth, division and development. Nitric Oxide (NO)- a gas, functions in the body as both a local regulator, and a neurotransmitter. When O2 in blood falls, endothelial cells in blood vessel walls release NO. NO releases enzyme that relaxes the cells, increasing blood flow to tissues (vasodilation).

Muscle Tissue

Responsible for nearly all types of body movement. All muscle cells consist of filaments containing the proteins actin and myosin, which together enable muscles to contract. There are 3 types of muscle tissue: skeletal, smooth, and cardiac.

Mammalian Cardiovascular System

Right ventricle pumps blood to the lungs where it loads O2 and unloads CO2. Oxygen rich blood from lungs enters the heart at the left atrium and is pumped to the body's tissues by the left ventricle. Blood returns to the heart through the right atrium. Cardiac cycle- complete sequence of heart's pumping and filling consists of a period of contraction (systole) and relaxation (diastole). Heart function can be assessed by measuring pulse (# of times heart beats per minute) and cardiac output (vol. of blood pumped by each ventricle per minute).

Endocrine Glands

Secrete hormones directly into surrounding fluid (thyroid, parathyroid, and gonads). Exocrine glands have ducts that carry secreted substances to body surfaces or cavities (sweat, saliva).

Information Processing

Sensory Neurons- like those in the snail's siphon, transmit information about external stimuli such as light, touch, or smell, or internal conditions such as blood pressure or muscle tension. Interneurons- form local circuits connecting neurons in the brain or ganglia. Interneurons are responsible for the integration (analysis and interpretation) of sensory input. Motor Neurons- Transmit signals to muscle cells, causing them to contract. Additional neurons that extend out of the processing centers trigger gland activity.

Simple Neuroendocrine Pathway

Sensory neurons respond to a stimulus by sending nerve impulses to a neurosecretory cell, triggering secretion of neurohormone. When reaching target cells neurohormone binds to receptor, triggering specific response.

Simple Columnar Epithelium

Simple columnar epithelium- large, brick shaped cells found where secretion or active absorption is important. (Lines intestines, secreting digestive juices and absorbing nutrients).

Basis of Membrane Potential

Sodium-potassium pump generates and maintains ionic gradients of K+ and Na+. Na+ gradient results in very little net diffusion of Na+ in a resting neuron because very few sodium channels are open. In contrast, many open potassium channels allow a significant net outflow of K+. Because membrane is only weakly permeable to chloride and other anions, this outflow of K+ results in a net negative charge inside cells.

Connective Tissue

Sparse population of cells scattered throughout extracellular matrix, holds many tissues and organs in place. Within matrix are fibroblasts- secrete fiber proteins, and macrophages- engulf foreign particles. 3 kinds- Collagenous fibers (strength and flexibility), Reticular fibers (join connective tissue to adjacent tissues), and Elastic fibers (make tissues elastic).

Adipose Tissue

Specialized loose connective tissue that stores fat in adipose cells.

Steroid Hormone Receptor

Steroid Hormone- located in cytosol prior to binding to hormone. Binding to cytosolic receptor forms complex that moves into the nucleus. There, receptor alters transcription of genes by interacting with specific DNA-binding protein. *estrogen/estradiol. Binds to cytoplasmic receptor in liver cells, activating transcription of vitellogenin gene (produces egg yolk) Following translation of mRNA, vitellogenin protein transported to reproductive system. Thyroxine, vitamin D, and other lipid soluble hormones that are not steroids typically have receptors that bind in nucleus. Once bound, stimulate transcription of specific genes.

Thermogenesis

Stimulate heat via shivering. Non-shivering thermogenesis: endocrine signals released in response to cold cause mitochondria to increase metabolic activity and produce heat instead of ATP. (ie. brown fat specialized for rapid heat production, extra mitochondria give brown color).

Metabolic Rate

Sum of all energy an animal uses in a given time interval. Can be measured by observing animal's heat loss (nearly all energy used in cellular respiration dissipates as heat). Energy measured in joules, or in calories (Kilocalorie=1000 calories, or 4,184 joules). Rate of food consumption + energy content of food + chemical energy lost in waste products= metabolic rate over longer periods of time. Affected by many factors (age, size, sex, activity, temperature, and nutrition).

Sex Hormones

Testes synthesize androgens, main one is testosterone (development of testes in early development, puberty- voice dropping, hair/muscle/bone growth). Estrogens, most important is estradiol responsible for maintenance of female reproductive system and for development of female secondary sex characteristics. Progesterone maintains uterus tissue to support growth and development of a baby.

Chemical Digestion in Human Digestive System

Timing and location of breakdown are specific to each class of nutrients. Carbs- whole system Proteins- Stomach, small intestine Nucleic Acids/Fats- small intestine

Countercurrent Heat Exchanger

Transfer of heat (or solutes) between fluids that are flowing in opposite directions. 1.) Arteries carrying warm blood to animals extremities are in close contact with veins conveying cool blood in the opposite direction, back towards trunk of body. Facilitates heat transfer from arteries to veins along entire length of blood vessels. 2.) Near end of leg or flipper, where arterial blood has been cooled to far below the animals core temp, the artery can still transfer heat to the even colder blood in the adjacent vein. Blood in veins absorbs heat as it passes warmer and warmer blood traveling in opposite direction in arteries. 3.) As blood in veins approaches the center of the body, it is almost as warm as body core, minimizing heat loss resulting from body parts in cold water. Bird: Arteries carrie blood into leg and foot. Veins return it to the heart. Dolphin: Artery of flipper surrounded by veins in counter current arrangement, allowing heat exchange.

How Human Kidney Concentrates Urine

Two solutes contribute to osmolarity of interstitial fluid: NaCl and urea. Loop of Henle maintains interstitial gradient of NaCl, which increases continuously in concentration from the cortex to the inner medulla. Urea diffuses into interstitial fluid of medulla from collecting duct (most remains in duct to be excreted). Filtrate makes 3 trips between cortex and medulla: first down, then up, and then down again in the collecting duct. As filtrate flows in the collecting duct past interstitial fluid of increasing osmolarity, more water moves out of the duct by osmosis. Loss of water concentrates the solutes, including urea that will be excreted in urine.

Nutrient Absorption of Small Intestine

Villi- fingerlike projections in lining of small intestine. Within villi, each epithelial cell has many microscopic projections, microvilli that face the intestinal lumen. Enormous surface area (folds)= much faster rate of nutrient absorption. Across concentration gradient nutrients pumped into blood, converge into hepatic portal vein. HPV- blood vessel that leads directly to liver. Liver regulates distribution of nutrients in the body and removes toxic substances before circulating throughout the body.

Variation in Hormone Receptor Location

Water Soluble Hormone- Binds to receptor protein, triggers transduction. Lipid-soluble hormones- transducting occurs within target cell. Hormone activates receptor, which directly triggers cells response. Most cases response in lipid soluble hormones is a change in GENE EXPRESSION.

Open Circulatory System

the circulatory fluid (hemolymph) is also the interstitial fluid that bathes body cells. Arthropods (spiders, grasshoppers, lobsters, crabs), some mollusks (clams) have open circulatory systems. Contraction of heart pumps hemolymph through circulatory vessels into interconnected sinuses, spaces surrounding the organs. Within sinuses the hemolymph and body cells exchange gases and other chemicals. Relaxation of heart draws hemolymph back in through pores, which have valves that close when heart contracts. Some body movements periodically squeeze sinuses, helping to circulate lymph. Lower hydrostatic pressure means using less energy than a closed system. Spiders use hydrostatic pressure to extend legs.