Biology 1002H Exam 2

Skeletal Muscles (function)

1. generally attached to the skeleton of an animal. Stimulated by signals from the nervous system that lead to contraction of the muscle. Are voluntarily controlled and produce movements required for locomotion.

Explain how sensory receptors pass along the intensity of a stimulus.

A sensory receptor is in some cases a neuron. In other cases, it may be a specialized epithelial cell that synapses with a neuron referred to as a sensory neuron. i. In both cases, the sensory receptor recognizes internal or external stimulus and initiates sensory transduction by creating graded potentials. Stronger stimuli lead to action potentials that are sent to the CNS.

Cardiac Muscle (function)

1. - Physical and electrical connections between individual cells enable many cells to contract almost simultaneously. Cannot be contracted voluntarily. Found only in the heart where it provides force that generates enough pressure to pump blood through an animal's body.

Smooth Muscle (Function)

1. - Surround hollow tubes and cavities inside the body's organs, so their contraction can move the contents of those organs. Also surrounds and forms part of small blood vessels and airway tubes. (Contraction in those regions reduces blood or air flow and this helps direct blood flow to regions of the body that most require it at a given time. In the airway it helps direct air to the healthiest part of a lung). Contraction of smooth muscles is involuntary and occurs without conscious control.

Describe the composition of vertebrate bone.

Bone is a living, dynamic tissue with both organic and mineral components. Two types of cells form bones: i. Osteoblast and Osteocytes c. Osteoclast= cells that break down bone. d. Bone cells consist primarily of the protein collagen, whose structure helps give the bone strength and flexibility. i. The mineral part of the bone is made up of a crystalline mixture of primarily calcium, and phosphate and other ions that provide rigidity. 1. Must be obtained through diet, absorbed in blood, and deposited in bone. 2. Bone lacking in minerals is easily fractured. e. Bone is continuously broken down and reformed.

List the major functions of the vertebrate skeleton.

Bones are connected in ways that allow for support, protection of internal structures, and movement. Two parts: i. The axial skeleton= composed of the bones that form the main longitudinal axis of an animal's body, including the skull, vertebrae, sternum and ribs. ii. The appendicular skeleton= Consist of the limb bones and the bones that connect them to the axial skeleton. A joint is formed where two or more bones come together. i. 3 different types of joints for movement: 1. Pivot 2. Hinge 3. Ball-and-socket joints ii. Other joints do not allow movement (fused joints) and some allow limited movement (vertebral column). Other functions of the skeleton are to make blood cells and platelets (help blood clot). i. Also participates in homeostasis of Ca2+ and PO4^2- 1. If there is not enough of these ions in the blood, they will take them from the bones to ensure certain cell activities are performed.

List the three types of muscle found in vertebrates and describe where they are found in the body.

Cardiac Muscle: found only in the heart and provided the force required for the heart to pump blood. Smooth muscles: Surrounds and forms part of the lining of hollow organs and tubes, including those of the digestive track, urinary bladder, uterus, blood vessels, and airways. i. Contraction of the smooth muscles in such organs may propel contents forward or churn them up. ii. In other cases, smooth muscles regulate the flow of substances by changing tube diameter. iii. Not under voluntary control, controlled by the automatic nervous system, hormones, and local chemical signals. Skeletal Muscles: Found throughout the body and is directly involved in locomotion. In vertebrates only, skeletal muscle is electrically excitable (it can generate action potentials in response to a stimulus—invertebrates only have graded action potentials). i. Action potentials of vertebrate's skeletal muscle cells result in an increased concentration of Ca2+ in the cytosol, which triggers force generation.

Muscle Tissues

Consist of specialized cells that shorten or contract generating the mechanical forces that may produce body movement, decrease the diameter of a tube, or exert pressure on a fluid-filled cavity. b. Skeletal, smooth, and cardiac

Distinguish between exoskeletons and endoskeletons.

Exoskeleton: an external skeleton that surrounds and protects most of the body surface. i. Provide support for the body, protection from the environment and predators, and protection for internal organs. ii. Made of Chitin, and in occasionally (in crustaceans—lobsters and shrimp) it is strengthened with calcium and other minerals. iii. Tough, durable, and segmented to allow for flexibility and movement. 1. Trade off= Does not allow growth (must shed and regrown skeleton—molting). Endoskeleton: Provide support and protection, are internal structures and do not protect the body surface, but most do protect internal organs. i. Minerals including calcium, magnesium, phosphate and carbonate supply the hardening material that gives the skeleton its firm structure.

Outline the anatomical organization of the human nervous system.

In vertebrates, the CNS and PNS are anatomically and functionally connected. i. CNS receives information about the internal or external environment in the form of neuronal signals from the PNS. 1. Interprets that info and may initiate a response that is then preformed by the PNS. 4 Steps of Sensory Systems i. Stimulus (electrical or chemical/ligand/ions) ii. Transduction of stimulus into receptor potential in sensory receptor. iii. Transmission of action potential in sensory neuron. iv. Interpretation of stimulus in central nervous system.

List the classes of sensory receptors and the stimuli to which they respond.

Mechanoreceptors: transduce mechanical energy such as touch, pressure, stretch, movement, and sounds. Thermoreceptors: detect cold and heat. Nociceptors: or pain receptors, detect extreme heat, cold, and pressure, as well as certain potentially damaging molecules such as acids. Electromagnetic receptors: sense radiation within a portion of the electromagnetic spectrum, including visible, UV, and infrared light, as well as electrical and magnetic fields in some animals. Photoreceptors: are a type of electromagnetic receptor that detect visible light. Chemoreceptors: recognizes specific chemical compounds in the air, water, body fluids, or food.

List the different categories of animal tissue

Muscle Nervous Epithelial Connective

Describe how antagonistic muscles function at a joint.

Muscle Fibers: skeletal muscles are composed of cells called muscles fibers—bound together in bundles (called fascicles) by a succession of connective tissue layers. i. Skeletal muscles are usually linked to bones by bundles of collagen fibers known as tendons. When a great enough force is applied, a bone moves as the muscles shortens. A contracting muscle exerts only a pulling force, so the muscles attached to it via tendons shortens, the attached bones are pulled toward or away from each other. Muscles that bend a limb at a joint are called flexors. Muscles that straighten a limb are called extensors. Two or more muscles that produce opposites directed movements at a joint are known as antagonist.

Identify the structural components of a muscle down to the level of the sarcomere.

Myofibrils: Skeletal muscle fiber arises from several cells that fuse to form a single mature cell with multiple nuclei. Each fiber contains numerous cylindrical bundles known as myofibrils. i. They extend from one end of the fiber to the and are linked to the tendons at the end of each fiber. Myofibrils contain two functional structures called thick and thin filaments. i. One complete unit of this repeating pattern is known as a sarcomere. ii. Thick= Composed almost entirely of the protein myosin (a motor protein that hydrolyzes ATP as a source of energy). iii. Thin= about half a diameter thinner than thick and contain cytosol protein actin and associated proteins. Components of Sarcomeres: i. A Band: formed by the thick filaments located in the middles of each sarcomere, where their openly parallel arrangement produced a wide, dark band. A portion of the thin filament overlaps the thick in this band. ii. Z line: a network of proteins to which thick filaments are attached. Two Z lines define the boundaries of one sarcomere. iii. I band: lies between the A and two adjacent sarcomeres. Contains the portions of thin filament that do not overlap the thick filament. Each I band is bisected by a Z line. iv. H Zone: narrow region in the center of the A band. It corresponds to the space between the two sets of thin filaments in each sarcomere. v. M Line: center of the H zone and is composed of proteins that link the central regions of the adjacent thick filaments. Cross-Bridges: Space overlapping thick and thin filaments are bridged by these. They are regions of myosin molecules that extend from the surface of the thick to the thin.

Describe the structural features of a neuromuscular junction and the role of acetylcholine in mediating skeletal muscle excitation.

Neuromuscular Junction: The site where a motor neuron's axon synapses with a muscle fiber is called the neuromuscular junction. Near the surface of the muscle fiber, the axon divides into several short processes, or terminals, containing synaptic vesicles filled with neurotransmitter acetylcholine (Ach). The region under the muscles plasma membrane that lie directly under the axon terminal is called the motor end plate. i. Motor end plate: folded into junctional folds to increase SA and is where the ACh receptors are located. The extracellular space between the axon terminal and the motor end plate is called the synaptic cleft. Acetylcholine: is the neurotransmitter that is received by the muscle fiber presynaptic, causes depolarization which leads to the release of Ca2+.

Explain how olfactory receptors respond to the binding of odor molecules.

Olfactory sensory receptors cells are neurons that are located in the epithelial tissue at the upper part of the nasal cavity. The cells are surrounded by two additional cell types. i. Supporting cells: located between the receptor cells and provide physical support for the olfactory receptors. ii. Basal cells: Differentiates into new olfactory receptors every 30-60 days, replacing those that have died after prolonged exposure of their cell endings. Olfactory sensory receptors have dendrites from which long, thin extensions called cilia extend into a mucous layer that covers the epithelium. i. Receptors have receptor proteins within the plasma membranes of the cilia, which provides an extensive surface area. 1. Airborne molecules dissolves in the mucus and bind to these olfactory receptor proteins. When an odor molecule binds to its receptor protein, it initiates a signal transduction pathway that ultimately opens Na+ channels in the plasma membrane. a. Depolarization results in action potential beings transmitted to the next series of dells located in the olfactory bulbs of the brain.

Describe the steps involved in the mechanisms by which photoreceptors respond to light the eye.

Photoreceptors differ from other sensory receptor cells because at rest in the dark their membrane is slightly depolarized, whereas in response to a slight stimulus, it becomes hyperpolarized. In the dark the cell membranes of the outer segments of resting cells are highly permeable to Na+ ions. i. Na+ diffuses into the cytosol through open Na+ channels in the outer segment membrane. Channels are gated by cGMP. 1. In the dark cGMP concentrations are high, keeping Na+ channels open and depolarizing the cell which results in a continual release of neurotransmitter glutamate from eh synaptic terminal of the photoreceptor. Which then sends a signal to the CNS. In the light the cell membrane the Na+ ion channels close because cGMP concentrations block the Na+ channels. This leads to a hyperpolarized state in the cell that causes glutamate to stop being released. This is interpreted by the brain as a visual image.

Describe the relationship between sensory transduction and perception.

Sensory Transduction: the process by which incoming stimuli are converted into neutral (electrical) signals. i. Involves cellular changes, such as opening of the ion channels, which cause either graded potentials or action potentials in neurons. Perception: an awareness of sensations that are experienced. (Perceived by brain). i. The brain processes sensory information in areas that do not generate conscious though.

Explain the sliding filament mechanism of muscle contraction.

Skeletal muscle shortens when thin filaments slide past thick filaments. Structure of thin filaments are closely associated with the protein's tropomyosin and troponin, which have important functions in regulating contractions. i. Myosin proteins have a 3-domain structure= two intertwined tails, two hinges, and two heads. Each head contains two binding sites, one for actin and one for ATP. ii. Hydrolysis of ATP gives energy for the cross-bridges to move via bending motion at the hinges. The sliding filament mechanism= the sarcomere shorten, but neither the thick nor thin filaments change length. Instead, the thick filaments remain stationary while the thin filaments slide, pulling on the Z-lines and shortening the sarcomere. i. It is propelled by myosin cross-bridges because each cross-bridge attaches to an actin molecule on the thin filament and moves in a bending motion. 1. Due to opposite orientation of the thick filaments, the movement of a cross-bridge forces the thin filament toward the center of the sarcomere, therefore shortening it.

Outline the general characteristics of the three types of skeletal muscle fibers.

Slow fibers: Fibers containing myosin with low ATPase activity. Fast Fibers: Fibers containing myosin with high ATPase activity. Glycolytic Fiber: have fewer mitochondria but possess a high concentration of the proteins involved in glycolysis. The 3 major types: i. Slow-oxidative Fibers= low rates of myosin ATPase activity, but have the ability to make large amounts of ATP due to oxidative phosphorylation. 1. Useful for prolonged, regular types of movement (standing or sitting upright). 2. Muscles that do not fatigue easily. ii. Fast-Oxidative Fibers= High rates of myosin ATPase activity and can make large amount of ATP due to oxidative phosphorylation. 1. Do not fatigue easily and can be used for long-term actions. They are particularly suited for rapid actions. iii. Fast-Glycolytic Fibers= high myosin ATPase activity, but can make large amounts of ATP due to relying on glycolysis. 1. Best suited for rapid, intense actions (short sprinting). 2. Fatigue very rapidly

Identify the differences between the somatic and autonomic nervous systems.

Somatic Nervous System: major functions are to sense the external environment and control skeletal muscles. i. The afferent sensory neurons of the somatic nervous system receives stimuli, such as heat, light, odors, chemicals, sounds, and touch, and transmit signals to the CNS. ii. The efferent motor neurons of the somatic nervous system control skeletal muscles (Cell bodies are located within the CNS). iii. Many responses of the somatic nervous system can be controlled consciously (voluntarily). Not all though. Autonomic Nervous System: Regulates homeostasis and organ function. i. Predominantly composed of efferent motor neurons. 1. Efferent pathways involved two motor neurons- the cell body is within the CNS and synapses on the second neuron in ganglia outside spinal cord (ganglia are part of the PNS). 2. Control smooth muscles, cardiac muscles, and glands. ii. Not voluntary- cannot control heartbeat or blood pressure. iii. Efferent nerves are subdivided. 1. Sympathetic divisions: responsible for rapidly activating systems that prepare the body for danger or stress. (Flight or fight response). 2. Parasympathetic division: involved in maintaining and restoring body functions. (Rest or digest response).

Outline how receptor cells within taste buds respond to the binding of food molecules.

Taste buds are structures containing chemosensory cells that detect particular molecules in food. i. Papillae on surface collect food molecules in taste pores that are filled with many taste buds with sensory receptors. The sensory receptor cells, along with several other supporting cells, form a complex structure that is organized like wedges of an orange. i. Microvilli are hairlike structures that extend into the taste pore from the receptor to increase surface area. ii. Molecules dissolve into saliva and bind to receptor proteins. iii. These binding triggers intracellular signals that alter ion permeability and membrane potentials. iv. The sensory receptor cells then release neurotransmitters onto underlying sensory neurons. v. Action potentials travel from these neurons to the thalamus and other regions of the forebrain, where taste is perceived.

Describe the organization of the peripheral nervous system.

The PNS in vertebrates is subdivided into two major functional and anatomical components: the somatic nervous system and the autonomic nervous system. Both systems have afferent (sensory) nerves and motor (efferent) nerves.

1. Explain how the concept of homeostasis as it applies to the internal environment of animals.

The external environment of animals is always changing (temperatures, nutrients, water supply, pH, and oxygen availability), so animals use homeostasis to respond to changes and counteracting them to maintain a stable, unchanged internal environment. If animals were unable to maintain their internal environment, they would die

Core Skills » Predict how skeletal muscle contraction would be affected by changes in electrical activity in motor neurons.

The propagation of action potentials causes an increase in Ca2+ ions in the cell which triggers a muscle contraction. This is called excitation-contraction coupling—The electrical activity in the plasma membrane does not act directly on the contractile proteins but instead acts as a stimulus to increase cytosolic Ca+2 concentrations . The increase of Ca2+ allows in to diffuse down its gradient into the cell and activate the contractile apparatus. Sarcoplasmic Reticulum is the Ca2+ reservoir. It is a specialized form of the ER. T-tubules= are invaginations of the plasma membrane that lie close to the sarcoplasmic reticulum. They conduct action potentials from the outer surface of the muscle fiber to the myofibrils.

Describe the structure of the mammalian ear and explain how mechanical forces move through it.

Three main compartments i. The outer: consist of the external ear, and the auditory canal. Separated from middle ear by the tympanic membrane (eardrum). ii. The middle: Contains 3 small bones called ossicles that link movements of the eardrum with the oval window. 1. The oval window is another membrane similar to the eardrum that separates the middle ear from the inner ear. iii. The inner: composed of cochlea (a coiled chamber of bone containing hair cells and the membrane-like round window) and the vestibular system, which functions in balance. Structures in inner ear generate the signals that travel via the auditory nerve to the auditory cortex of the brain

Describe how pressure is determined for touch and hearing.

Touch: Several types of receptor in the skin of many animals detect touch, deep pressure, or the bending of hairs on the skin. Some receptors consist of neuronal dendrites covered in dense connective tissue. i. In mammals, these receptors are located at different depths below the surface of the skin, which makes them suitable for responding to different types of stimuli. Sound: Called audition, is the ability to detect and interpret sound waves. i. Hari cells contain ion channels that open or close when the hair bends certain directions. This causes the membrane to depolarize and calcium voltage-gated channels to open, resulting in the release of neurotransmitter molecules from the hair cells. Then an action potential is created and sent to the CNS. 1. Bending of hair cells is stimulated by change in wavelengths or pressure.

Explain how tropomyosin and troponin help regulate muscle contraction.

Tropomyosin: a rod-shaped molecule composed of two intertwined protein subunits. They are arranged end to end along the thin filament. In the absence of Ca2+ they partially cover the myosin- binding site on each actin molecule, thereby preventing cross-bridges from contacting actin. Troponin: A smaller, globular-shaped protein with 3 subunits that are bound to both tropomyosin and actin. It holds tropomyosin in blocking position when the muscle is relaxed. i. One of its subunits binds to Ca2+, which produces a shape change in the protein that causes tropomyosin to stop blocking the cross-bridges. This allows cross-bridge cycling to occur.

Outline the neural pathway by which visual signals travel to reach the brain.

When it is dark the cell membrane is depolarized because of the release of glutamate. Glutamate is released from the synaptic terminal of the photoreceptor, which then synapses with a postsynaptic cell that is the next neuron in the pathway. This initates a series of events within the retina that is interpreted by the brain as an absence of light. In contrast when exposed to light, the Na+ channels in the outer segment membranes of the photoreceptor close. The resulting decrease in Na+ concentrations lead to a hyperpolarization of the cell. In response, the release of glutamate is stopped. This results in a series of cellular activations within the retina and brain that is interpreted as a visual image.

1. Core Skills » Analyze the results of Agre and explain how they indicated the presence of a water channel.

a. Algre won the noble peace prize in 2003 for discovering the proteins that make it possible to transport water so rapidly across the plasma membranes. (named them aquaporins).

1. Core Skills » Make predictions about the function of parts of the alimentary canal based on their structural adaptations.

a. Alimentary Canal has an opening at both ends through which food passes from one end to the other. Contains smooth muscle and occasionally has contraction muscles that help churn up the ingested food so that it is mechanically broken into smaller fragments. b. Canal is lined on interior by a layer of epithelial cells. These cells synthesize and secrete digestive enzymes and other factors into the hollow cavity of the alimentary canal, and they secrete hormones into the blood that help regulate digestive processes. i. Also involved in transporting digestive material out of canal and to rest of body. c. Along length, canal has several specialized regions that vary according to species. These specializations can be segregated from one another due to pH value, varying from acidic for one digestive process (stomach) to neutral in another process (small intestine). i. Ability for animals to store food in stomach allows them to eat less frequently.

1. Compare and contrast uniporters, symporters, and antiporters.

a. All types of transporter proteins b. Uniporters- bind a single ion or molecules and transport it across membrane. c. Symporters- bind two or more ions or molecules and transport them in the same direction across the membrane. d. Antiporters- Bind two or more ions or molecules and transport them in opposite directions across the membrane.

Identify four groups of essential nutrients, listing several examples of each.

a. Amino Acids (9): nine amino acids are required in the diet of humans and many, but not all animals. These amino acids are required for building proteins but cannot be synthesize by an animal's cells, unlike the other 11 amino acids. i. Animals do not store amino acids so they must be taken in regularly through diet. ii. Carnivores and omnivores regularly take in the essential amino acids because meat contains all 20 amino acids. (Vegans must find another way to get amino acids) b. Fatty Acids: certain unsaturated fatty acids, such as linoleic acid, that cannot be synthesized by animals' cells need to be taken in through diet. Linoleic acid is vital to an animal's health because it is converted in cells to another fatty acids, called arachidonic. i. Function for pain , blood clotting, and smooth muscle contraction ii. Found primarily in plants which provide for herbivores and omnivores. 1. Herbivores gain theirs through fish or adipose tissues of birds/mammals c. Vitamins: important organic nutrients that serve as coenzymes for many metabolic and biosynthetic reactions. i. Two categories 1. Water-soluble: not stored in body and must be regularly ingested 2. Fat-soluble: stored to some degree in adipose tissue. ii. Not all animals require the same vitamins. 1. Primates and guinea pigs cannot synthesize their own vitamin C. d. Minerals: inorganic ions required by animals for normal functioning of cells. Minerals such as iron and zinc are required as cofactors of constituents of some enzymes and other proteins. i. Calcium required for bones, muscle and nervous system function. ii. Sodium and Potassium iii. Many minerals are only required in trace amounts, but still needed regularly.

1. Describe the mechanisms of digestion and absorption of carbohydrates, proteins, and fats in vertebrates, and explain the importance of enzymes in some of these processes.

a. Carbohydrates: Digested by amylase and brush border enzymes and absorbed by small intestine. i. Most start out as polysaccharides; very small amount gets digested in mouth by salivary amylase but almost all get digested in the small intestine due to the action of amylase secreted into the intestine by the pancreas. ii. Monosaccharides are then absorbed into the epithelial cells where facilitated diffusion or secondary active transport with Na+ gets them into the blood stream. b. Proteins: Digested by proteases in the stomach and small intestine and amino acids are absorbed into the small intestine. i. The pancreas secretes enzymes as inactive precursor, which prevents the active enzymes from digesting the pancreas itself. Once the inactive form of trypsin enters the small intestine it is cleaved into active molecule by another enzyme and then goes and activates the pancreas secreted enzymes. ii. The polypeptide fragments are further digested into individual amino acids, which through secondary active diffusion with Na+ then diffuse into the epithelial cells and go into the blood steam. 1. Like carbohydrates they are almost completely absorbed in duodenum of small intestine. c. Lipids: Digested by lipases and absorbed by lymphatic system in small intestine. i. Start as triglycerides. Digestion occurs almost entirely in small intestine. Major digestion enzyme is lipase which is secreted by the pancreas into the small intestine. The lipase splits the triglyceride into 2 free fatty acids and 1 monoglyceride.

1. List the major categories of nutrients consumed by animals and some of their general functions.

a. Carbohydrates: come from all major food sources, energy source, components of some proteins, source of carbon. Without them they cause muscle weakness and weight loss. b. Proteins: all major food sources (meat, legumes, cereals, roots), provide amino acids to make new proteins, build muscle, some used as energy source. Without them you get weight loss, muscle loss, weakness, weakened immune system, increased likelihood of infections. c. Lipids: All major food sources (fatty meats, dairy products, plant oils), major component of cell membranes, energy source, thermal insulator, building blocks of some hormones. Without them you get hair loss, dry skin, weight loss, hormonal and reproductive disorders. d. Nucleic Acids: All major food sources, provides sugars, bases and phosphates that can be used to make DNA, RNA, ATP. Without them no components of nucleic acids can be synthesized by cells from amino acids and sugars.

1. Core Skills » Identify the different parts of a typical neuron and explain how the structure of each relates to its function.

a. Cell Body- Contains nucleus and other organelles. Cell body functions like any other cell and receives the signals from the dendrites and sends them to the axon. b. Dendrites- They are treelike structures extending from the cell body with numerous branching extensions. This structure provides a large surface area for contact with other neurons. They receive the electrical and chemical messages from other neurons and move towards the cell body, hence their structure. c. Axon- Can be very small or large in shape depending on the size of the animal. A typical neuron has one axon that may have branches and is usually wrapped in a layer of glia called myelin. i. Axon hillock= closest to cell body and is important in the generation of signals that travel along axon. ii. Axon Terminals= at the end of axon, can have one or more. They convey the electrical or chemical messages to other cells.

Outline the functional differences between channels and transporters.

a. Channel: a transmembrane protein that forms an open passageway for the facilitated diffusion of ions or molecules. Solutes move directly through a channel to get to other side. i. Faster than transporters ii. Example- Aquaporins a. Transporters: Transmembrane proteins bind one or more solutes in a hydrophilic pocket and undergo a conformational change that switches the exposure of the pocket from one side of the membrane to the other. i. Slower than channel

Connective Tissue

a. Connective: Connect, surround, anchor, and support the structures of an animal's body. i. Include blood, adipose (fat-storing) tissue, bone, cartilage, loose and dense connective tissue. ii. An important function of some connective cells is to from part of the ECM (extracellular membrane) around cells by secreting a mixture of fibrous protein and carbohydrates. 1. General functions of ECM: a. Providing scaffold to which cells attach and organize themselves into tissues. b. Protecting and cushioning parts of the body c. Providing mechanical strength d. Cell signaling

Describe the general structure of the vertebrate digestive system

a. Consist of alimentary canal (gastrointestinal track- GI), plus several accessory organs. i. Alimentary canals consist of oral cavity (mouth), pharynx (throat), esophagus, stomach, small and large intestines, and anus. b. Accessory organs, not found in all, are the salivary glands, liver, gallbladder, and pancreas.

1. Distinguish between ligand-gated and voltage-gated ion channels.

a. Depolarization: Occurs when the cell membrane become less polarized, that is, less negative inside the cell relative to the surrounding fluid. i. Often this occurs when channels are opened to allow Na+ to diffuse into the cell making it more positive. b. Hyperpolarization: Occurs when the cell membrane becomes more polarized, that is, more negative on the inside relative to the extracellular fluid. i. Often this occurs when channels are opened to allow K+ to diffuse out of the cell making it more negative. c. Voltage-gated Channels: open and close in response to changes in voltage across the membrane, i. Changes in voltage across the membrane is cause by the opening of ligand-gated channels. d. Ligand-gated Channels: Open or close when ligands, molecules such as neurotransmitters, bind to them. i. When ligands are close however, they are just deactivated. To get them to go back to the regular closed shape the membrane must return to its resting membrane potential.

Core SKILLS » Predict problems that might arise if saliva or acid could not be secreted into the mouth or stomach, respectively

a. Digestion would not occur. b. Saliva has several functions: i. Moisten and lubricate food to facilitate swallowing. ii. To dissolve food particles to facilitate the ability of specialized chemical-sensing structures called taste buds to taste food. iii. Kill ingested bacteria with a variety of antibacterial compounds. iv. Initiate digestion of carbohydrates through the action of a secreted enzyme called amylase. c. Stomach produces hydrochloric acid. i. Partially digests some of the macromolecules in food and regulates the rate at which its contents empty into the small intestine. ii. Glands secrete HCl and an inactive protein called pepsinogen into the stomach lumen. Acid converts protein into pepsin which begins the digestion of proteins. iii. HCl also kills off any microorganisms that may have been digested with food. No significant digestion of carbohydrates or lipids occurs in the stomach.

1. Distinguish between two types of potentials produced in postsynaptic cells: excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs).

a. EPSP= When neurotransmitters are called excitatory it is because they depolarize the postsynaptic membrane. i. Called excitatory because the depolarization of the postsynaptic cell membrane brings the membrane potential closer to the threshold potential that would trigger an action potential. ii. A graded potential b. IPSP= When a neurotransmitter is inhibitory it is because it usually hyperpolarizes the postsynaptic membrane. This reduces the likelihood of an action potential by moving the membrane farther from the threshold. i. A graded potential ii. An example is the opening of Cl- channels. iii. Most common way neurons are inhibited.

Epithelial Tissue

a. Epithelial: Consist of sheets of densely packed cells that cover the body or individual organs and line the interiors of various cavities inside the body. Specialized to protect structures and to secrete and absorb ions and organic molecules. i. Come in various shapes: 1. Cuboidal (think cubes) 2. Squamous (Flattened) 3. Columnar (Elongated) ii. Arrange in various forms/layers: 1. Simple= one layer of cells 2. Stratified= multiples layers 3. Pseudostratified= one layer, but with nuclei located in such a way that it appears stratified 4. Transitional= multiple layers with the ability to expand and contract

Identify the primary cause of ulcers.

a. Erosion of any portion of the wall of the alimentary canal due to any cause is called an ulcer. b. Primary cause of ulcers is bacterial infection. Idea was not popular at first because scientist believed that bacteria could not live in such acidic conditions in the stomach. However, Marshall and Warren were able to provide support for their claim.

Describe the steps in exocytosis and endocytosis.

a. Exocytosis: material inside the cell is packaged into vesicles and then excreted into the extracellular environment. i. Vesicles usually derive from the Golgi apparatus. ii. Steps 1. Vesicle forms and cargo is loaded into the interior. 2. The budding process involves the formation of a protein coat around the emerging vesicle. 3. Bud separates from the membrane, vesicle is formed. 4. Vesicle is released and the protein coat is shed. 5. Vesicle fuses with plasma membrane and releases cargo into the extracellular environment. a. Exocytosis: material inside the cell is packaged into vesicles and then excreted into the extracellular environment. i. Vesicles usually derive from the Golgi apparatus. ii. Steps 1. Vesicle forms and cargo is loaded into the interior. 2. The budding process involves the formation of a protein coat around the emerging vesicle. 3. Bud separates from the membrane, vesicle is formed. 4. Vesicle is released and the protein coat is shed. 5. Vesicle fuses with plasma membrane and releases cargo into the extracellular environment.

1. Describe the events in the propagation of an action potential.

a. Experimentally, if an axon is stimulated in the middle of the axon, action potentials can travel in both directions (toward the cell body or towards the terminals). The reason why this does not ordinarily happen is the inactivation state of the Na+ channel. b. Speed of propagation depends on two factors: the axon diameter and the presence or absence of myelin.

1. Describe the structure and function of pumps.

a. Function is to produce an electrochemical gradient. i. Transport of ions and molecules 1. Symporters and antiporters use H+ and Na+ gradient to take up nutrients and export waste products. ii. Production of energy intermediates 1. In the mitochondria and chloroplast H+ gradients are used to synthesize ATP iii. Osmotic regulation 1. Animal cells control their internal volume by regulating ion gradients between the cytosol and extracellular fluid. iv. Neuronal Signaling 1. Na+ and K+ gradients are involved in conducting action potentials, the signals transmitted by neurons. v. Muscle Contraction 1. Ca 2+ gradients regulate the ability of muscle fibers to contract. vi. Bacterial Swimming 1. H+ gradients drive the rotation of bacterial flagella.

1. Name three major hormones important for the regulation of digestion in vertebrates and describe the role of each.

a. Gastrin: Chemical substances in chyme stimulate cells in the stomach epithelium to release the hormone gastrin which reaches all parts of the stomach through the blood stream. The presence of gastrin stimulates smooth muscle contraction in the stomach, which helps move chyme into small intestine. Gastrin also stimulates acid production in stomach. b. Cholecystokinin (CCK) and Secretin: Arrival of chyme in small intestine stimulates release of CCK and Secretin from intestinal epithelial cells. Cells of the pancreas respond to CCK by secreting digestive enzymes and to secretin by secreting acid-neutralizing bicarbonate ions. CCK also stimulates contraction of the gallbladder and therefore bile release.

1. Compare and contrast graded potentials and action potentials.

a. Graded Potential: any depolarization of hyperpolarization that varies depending on the strength of the stimulus. (Can differ in size!) i. A large change in the membrane potential occurs when a strong stimulus opens many channels, whereas a weak stimulus causes a small change due to only opening a small number of channels. ii. Occur locally on a particular area of the plasma membrane, such as on dendrites or the cell body, where an electrical or chemical stimulus opens ion channels. iii. Rapidly returns to resting membrane potential because ion pumps restore the ion concentration gradient and the channels close. b. Action Potential: The electrical events that carry a signal along an axon. It is always a large depolarization and never varies in size. i. When action potential is triggered it as an all-or-nothing reaction. (Cannot be graded). ii. Travel rapidly down the axon from hillock to terminals where they initiate a response at a junction with another cell. c. Depolarization phase of an Action Potential: An action potential begins when the graded potential is large enough to spread to the axon hillock without dying out and depolarizes the membrane there to a value called the threshold potential. i. Threshold potential= typically around -55 to -50 mV 1. Sufficient enough to open a large number of Na+ voltage-gated channels, triggering action potential. 2. Na+ channels open extremely rapidly, but K+ channels are delayed allowing for there to be change in the electrical potential of the membrane. d. Repolarization phase of an Action Potential: action potential approaches but does not reach equilibrium potential for Na+ due to and inactivation gate that swings into the channel pore blocking any further movement of Na+. i. Inactivation gate does not swing out of channel until membrane returns to resting potential. ii. Then the K+ voltage-gated channels open 1ms later and helping to return the membrane to resting potential. 1. Exhibits a brief period of hyperpolarization K+ reaches equilibrium potential.

1. List ways in which water and ions move across cell membranes and between body fluid compartments.

a. Intracellular fluid: the fluid inside cells that contain most of the water in an animal's body. b. Extracellular fluid: the fluid outside cells that contains the rest of the water that is not in the intracellular fluid. c. Ion Movement i. Passive Transport: movement of a solute down a concentration gradient (high to low). No ATP is required. 1. Simple diffusion and Facilitated diffusion. a. Can be calculated by adapting Fick's Law: J= KA(C1-C2) i. J= simple diffusion ii. K is a constant iii. A is area iv. C is the change in concentration at one point compared to another. ii. Active Transport: movement of a solute up a concentration gradient (low to high). ATP required. 1. One function dependent of difference in ion concentration is the generation of electrical gradients across the membranes of muscle cells and neurons. d. Water Movement i. Moves readily between compartments. ii. Permeable to water due to aquaporins 1. Movement depends on pressure gradient (Fick's Law) iii. Crenation= shrinkage of cell iv. Hemolysis= When cell swells and burst i. Osmolarity= solute concentration of aqueous solution (millimoles/liter) b. Obligatory Exchanges of water and ions i. Many processes can disturb ion and h20 homeostasis. 1. Requires extra energy to minimize or reverse disturbance. ii. Called obligatory exchange because animal is obligated to make them.

1. Describe the two general types of postsynaptic membrane receptors.

a. Ionotropic Receptors: ligand-gated ion channels that open in response to a neurotransmitter binding. i. Binding of neurotransmitter causes a shape change, allowing ions to flow through the channels to cause an EPSP or IPSP. b. Metabotropic Receptors: G-protein-coupled receptors. They do not form a channel but instead are coupled to an intracellular signaling pathway that initiated changes in the postsynaptic cell.

1. Core Skills » Predict the direction of water movement in response to solute gradients.

a. Isosmotic: When the concentrations of solutes on both side of the membrane are equal so the water concentration must also be equal. b. Hyperosmotic: When the concentration of solutes outside the cell is higher. Cause water to move out of the cell and maybe cause a crenation cell (shrinkage). c. Hypoosmotic: When the concentration of solutes inside the cell is higher. Causes water to move into the cell and potentially lead to osmotic lysis (cell bursting).

1. Explain the meaning of membrane potential.

a. Membrane Potential= Neurons are said to electrically polarized. So the membrane potential is the difference in electric charges along the inside and outside surfaces of a cell membrane. b. Resting Membrane Potential= refers to the membrane potential of an unstimulated cell that is not generating action potentials. i. The resting potential for neurons is a -70mV charge inside the cells.

1. Explain how myelination influences the speed of an action potential.

a. Myelinated axons conduct action potentials at a faster rate than unmyelinated axons. This is because the myelin acts as insultation to the axon reducing charge leakage across the membrane of the axon. i. The axons of myelinated neurons have exposed areas knows as the nodes of Ranvier. These nonmyelinated regions are characterized by having many voltage-gated Na+ channels. Only places on myelinated axons that have the ability to create an action potential.

1. Core Skills » Contrast negative feedback, positive feedback, and feedforward regulation, and explain how they do or do not contribute to the maintenance of homeostasis in animals.

a. Negative Feedback: A mechanisms that controls the homeostatic response so that it does not overcompensate. a. Positive Feedback: Does not achieve homeostasis. It accelerates or amplifies a process and moves a system away from homeostasis. a. Feedforward Regulation: In animals with well-developed nervous systems, homeostasis is aided by feedforward regulation, the process in which an animal's body prepares for a change in some variable before it even occurs.

Nervous Tissues

a. Nervous Tissues: Composed of a complex network of cells called neurons that are specialized to receive, generate, and conduct electrical signals from one part of an animal's body to another. i. An electrical signal produced in one neuron may stimulate or inhibit other neurons to initiate new electrical signals, stimulate muscle cells to contract, or stimulate glandular cells to release chemicals into an animal's body fluids. ii. *Nervous tissue provides a critical means of controlling diverse activities of the cells in an animal's body. (Communication!)

1. List the cellular components of the nervous system and describe the function of each cell type.

a. Neurons: cells that send and receive electrical and chemical signals to and from each other and other types of cells throughout the body. i. Cell Body- (soma) which contains the cell nucleus and other organelles. Two extensions extend from the cell body: 1. Dendrites: may be single projections of the cell body but more commonly are elaborate treelike structures with numerous branching and extensions that provides a large surface area for contacts with other neurons. a. Electrical and chemical messages from other neurons are received by the dendrites, and electrical signals generated in dendrites move toward the cell body. 2. Axon: an extension of the cell body that transmits signals along its length and eventually to other cells. a. May be wrapped in an insulating layer of glia cell tissue called myelin. b. Axon Hillock: Important in the generation of the electrical signals that travel along an axon. c. Axon Terminals: Convey electrical or chemical messages to other cells, such as other neurons or muscle or gland cells. 3. Glia: cells that surround neurons and preform numerous functions. Main function is to protect and cushion the neurons. a. Myelin Sheath: Specialized glial cells that wrap around certain axons at regular intervals to form an insulating layer. b. Nodes of Ranvier: Sheath is periodically interrupted by noninsulated gaps called NOR. c. In vertebrate brain and spinal cord myelin-producing glial cells are called oligodendrocyte. (CNS) d. Schwann cells are the glial cells that form myelin on axons that travel outside the brain and spinal cord. (PNS)

1. Describe the process of osmosis and how it affects cell structure.

a. Osmosis: The movement of water across a membrane to balance solute concentrations b. Animals do not have a cell wall and therefore have to regulate the movement of water more critically to avoid cell death. Plants have cell walls that help them hold the structure of the cells when in unbalanced osmotic situations.

1. Explain the importance of paracrine and hormonal signaling to homeostasis and provide examples of each.

a. Paracrine Signaling: Molecules are released into the extracellular fluid and act on nearby cells. (For homeostatic responses that are highly localized, occurring only in the area of disturbance). i. Example: Damage to an area of skin causes cells in the injured area to release molecules that help contain the injury, prevent infections, and promote tissue repair. b. Hormone Signaling: Communication over long distances occurs by releasing chemical messenger molecules, hormones, into the blood. i. Example: The decrease of blood pressure sends out hormones through the circulatory system or in the blood.

Compare and contrast simple diffusion, facilitated diffusion, passive transport, and active transport.

a. Passive transport: Movement of substance with its concentration gradient which requires no ATP/ energy. i. Simple Diffusion: Occurs when substance moves across a membrane from an area of high concentration to one of lower by passing directly through the phospholipid bilayer. 1. Small, nonpolar molecules ii. Facilitated Diffusion: Transport protein provides a passageway for a substance to cross a membrane from an area of high to low concentration. b. Active transport: Moves a substance from an area of low to high concentration with the aid of a transport protein. Requires energy/ATP.

1. Distinguish between passive and active absorption of food.

a. Passive: Small, hydrophobic molecules such as fatty acids diffuse down concentration gradients across the epithelium. b. Active: Ions and other molecules are transported by facilitated diffusion of active transport. i. Minerals are ion and do not readily cross the plasma membrane; transported actively across epithelial cells by ATP-dependent ion pumps. ii. In some cases, hydrophilic organic nutrients are transported by secondary active transport with the help of Na+.

1. Explain the difference between primary active transport and secondary active transport.

a. Primary Active Transport: involve the functioning of a pump- type of transporter that directly uses energy to transport a solute against its gradient. i. These pumps tend to establish a electrochemical gradient a. Secondary Active Transport: Process in which a pre-existing gradient drives the active transport of another solute. i. Example- an already established electrochemical gradient is used to move another molecule or ion across the membrane.

Outline how microorganisms can help digest cellulose in ruminants and other herbivores

a. Ruminants: Herbivores that lack the enzymes to break up cellulose but still can because of their microbiome. Microorganisms living within their digestive track break down the cellulose into monosaccharides that can be absorbed by the animal.

Core Skills » Describe the quantitative relationship between the surface area of an object and its volume and explain the importance of this relationship to animal form and function.

a. SA to Volume ratio: A high SA/V ratio is ideal for exchange of heat, solutes, gases, and water across a surface without contributing greatly to the mass or volume of the body part. i. However, a large increase of SA comes at the expense of a large volume if there is no shape change (bad). 1. Volume grows by a power of 3 and SA grows by a power of 2. ii. A large SA with a small volume is the most ideal SA/V ratio. It allows for sufficient gas exchange without exerting a large amount of energy. Low ratio is better!!

1. Describe the functional relationships among sensory neurons, motor neurons, and interneurons.

a. Sensory Neurons: Detect or sense information from the outside world, such as light, odors, touch, or heat. In addition, sensory neurons detect internal body conditions such as blood pressure or body temperature. i. Also called afferent neurons because they transmit information from the periphery to the CNS. (Long, single axon that branches allow for rapid transmission). b. Motor Neurons: Transmit signals away from the CNS and elicit some type of response that depends on the type of cell receiving the signal. Named because one type of response they cause is movement. In addition, they may cause other effects such as secretion of hormones from endocrine glands. i. Send signals away from the CNS= called efferent neurons. ii. Like sensory they have long axons, but do not branch into two main processes. c. Interneurons: Forms interconnections between other neurons in the CNS. The signals sent between interneurons are critical in the interpretation of information that the CNS receives, as well as the response that it may elicit. i. Tend to have many dendrites, and their axons are typically short and highly branched... Allows for complex connections with many cells.

1. Name the four components of a homeostatic control system and describe the importance of each to the regulation of an animal's internal environment.

a. Set point= the normal value for a controlled variable. b. Sensor= monitors the level or activity of a particular variable. c. Integrator= compares signals from the sensor with the set point d. Effector= compensates for any deviation between the actual value and the set point.

1. Describe smooth muscle to the extent it is covered in lecture - what it is, significance, similarities, and differences from skeletal muscle.

a. Smooth muscle cells make up smooth tissues. i. They surround hollow organs (maintain pressure and cause propulsion) ii. Have a contractile function (contractions are relatively slow and may be initiated without input of ions.) iii. Organ systems where it plays a significant role. 1. Circulatory, digestive, respiratory, lymphatic, muscular, reproductive, urinary, and skeletal. b. Different from skeletal muscles: i. Nonvoluntary ii. Do not need an action potential to contract.

1. Core Skills » Describe the difference between spatial summation and temporal summation and make predictions about postsynaptic potentials in a cell receiving multiple inputs from other cells.

a. Spatial Summation: When many EPSP's are open in many locations at one time (in the dendrites and the cell body) their depolarizations can sum together to reach threshold and cause an action potential. b. Temporal Summation: Two or more EPSP arrive at the same location in a quick succession causing the cell to reach threshold due to their depolarization sum and potentially action potential.

1. Provide an example of how the structure of an animal's tissues or organs can help predict their function.

a. Structure always determines function. b. Comparison between mammals and insects (similar functions and structure with only one major difference) i. Difference: mammals have lungs ii. Similarities: 1. Internal branching tubes composed of epithelial and connective tissues arises from one or more openings that connect with outside environment. a. Tubes become smaller (only one cell wide) i. How tissues or organs can predict function 1. Mammalian lungs are composed of a thin layer of epithelial cells that permits rapid diffusion of gases across them (diffusion would be slow if the layer were thick or scaly) 2. The extensive surface area of respiratory organs (gills/lungs) relates to their function of diffusing gasses quickly and great abundance.

1. Describe the structural features of a synapse.

a. Synapse: The junction where axon terminal meets another neuron, muscle cell, or gland cells. i. An electrical or chemical signal pass from axon terminal to the next cell. b. Includes: axon terminal of the neuron sending the signal, the nearby plasma membrane of the receiving cell, and in certain cases the synaptic cleft (extracellular space between the two cells. c. Presynaptic cell: sends signal. d. Postsynaptic cell: receives signal. e. Electrical Synapse: Directly passes electric current from the pre to the post (very rare). f. Chemical Synapse: A neurotransmitter is released from an axon terminal and acts as a signal from the pre to the post (more common).

1. Core Skills » Know how to use the Nernst equation to predict the direction in which different ions move across a plasma membrane.

a. The Nernst equations relates the electrical and concentration gradients to each other. It gives the calculated equilibrium potential for an ion at any given concentration gradient. b. E= 60mV log10 ([X (extracellular)]/[X (intracellular)]) c. Answer questions using the concept of Fick's equation and the Nernst Equation.

1. Describe how the resting membrane potential is established and maintained.

a. The RMP is determined by the ions located along the inner and outer surfaces of the plasma membrane because they are attracted to each other due to electric forces. b. The ions critical for establishing the resting membrane potential are Na+, K+ and to a lesser extent, Cl-. i. Na+ wants to move into the cell and make it more positive due to its concentration gradient. ii. K+ wants to move out of the cell to make it more negative due to its concentration gradient. c. Two factors are primarily responsible for determining the RMP. i. Establishment of ion concentration gradients: Na+ and K+ ATPase constantly pumps 3 Na+ into the cell and 2 K+ into of the cell. This establishes a concentration gradient. ii. Unequal membrane permeabilities to different ions: Plasma membrane contains ion-specific channels that affect the permeability of the membrane to Na+ and K+. An ungated channel that allows the passive movement of ions, sometimes referred to as a leak channel.

1. Explain the difference between the central nervous system (CNS) and the peripheral nervous system (PNS).

a. The central nervous system (CNS) consists of a brain and a nerve cord, which in vertebrates extends from the brain through the vertebral column and is called the spinal cord. b. The peripheral nervous system (PNS) consist of all neurons and projections of their plasma membranes that are outside of but connect with the CNS.

1. Describe how an electrochemical gradient determines the direction in which an ion will move.

a. The direction in which an ion diffuses depends on the electrochemical gradient for that ion, which is the combined effect of both an electrical and chemical (concentration) gradient. b. In living cells, the membrane potential at which this occurs for a particular ion at a given concentration gradient is referred to as that ion's equilibrium potential.

1. Explain why some nutrients do not require digestion prior to being absorbed.

a. They are absorbed into the small intestine in their complete form. This includes vitamins, minerals, and water. a. Vitamins, minerals, and water: Not digested and are absorbed mostly in small intestine. i. Do not require digestion and are absorbed in their complete form. ii. Most water-soluble vitamins are absorbed by diffusion or active transport in the small intestine. iii. Fat-soluble vitamins follow the pathway for lipid absorption (lymphatic pathway). iv. Water is the most abundant substance in chyme so small amounts of ingested water are absorbed in the stomach, and the great majority of water is absorbed in the small intestine. Epithelial cells in small intestine are very permeable to water.

1. Describe how food moves through regions of the alimentary canal and explain how each part contributes to the processes of digestion and absorption.

a. Three general sections: i. Anterior End: functions primarily in the ingestion of food. Contains mouth, pharynx, and esophagus. ii. Middle section: Functions in storage and initial digestion of food. Contains one or more food storage or digestive organs, including crop, gizzard, and stomach. 1. Contains upper part of small intestine where most of the digestion and absorption occurs. a. Accessory organs that connect with the intestine are the pancreas, liver and gallbladder. iii. Posterior End: Functions in final digestion and absorption and the elimination of nondigestible wastes. Consist of the remainder of the small intestine and the large intestine. 1. Undigested material is exposed of through the anus or cloaca.

1. List several variables that are regulated within a homeostatic range in vertebrate animals.

a. Variables have range because no physiological function can remain constant over a long period of time (why they are called variables). Some variables fluctuate around an average value and still be considered balanced. b. Variable Examples: i. Minerals- influenced by eating food and excreting waste 1. NA+ and K+= Establish resting membrane potentials across plasma membrane in all cells and transmit electrical signals in excitable tissues (muscle and nervous). 2. Ca 2+= Important for muscle contraction, neuron function, skeleton and shell formation. 3. Fe 2+= Binds and transports oxygen in blood or body fluids (some invertebrates use copper instead of iron). ii. Energy Sources- Eating food, expending energy. 1. Glucoses= broken down to provide energy for use by all cells, especially brain. 2. Fat= Provides an alternative source of energy, particularly for cells not in the nervous system, major component of plasma membrane. 3. ATP= Provides energy to drive most chemical reactions and body functions, modifies function of many proteins by transferring a phosphate group to proteins. iii. Body Temperature- Rate of energy expenditure, environmental temperature, behavioral mechanisms. 1. Determines rate of chemical reactions in the body. iv. pH of Body Fluids- Hydrogen ion transporters in cells, buffers in body fluids, rates of energy expenditure, breathing rate. 1. Affects enzymatic activity in all cells. v. Oxygen and Carbon dioxide- movement of air or water across respiratory surfaces, metabolic rate. 1. Oxygen circulates in body fluids and enters cells, where it is used in the production of ATP. Carbon dioxide is a waste product that is eliminated to the environment, but also is a key factory that regulates the rate of breathing. vi. Water- Drinking, eating, excretion of wastes, perspiration, osmosis across body surface. 1. Numerous biological functions including participating in chemical reactions, helping to regulate body temperature, acting as a solvent for biologically important molecules.

Addiction and sensitization/desensitization

a. When normal: Neurotransmitter is reabsorbed at a normal synapse. (Everything is normal). b. When on drugs: i. Drug molecules prevent reabsorption and cause overstimulation of the postsynaptic membrane. You experience overly happy and excited emotions. 1. To combat the lack of reabsorption the number of receptors decrease to prevent over stimulus of postsynaptic cell. c. Drug withdrawals: The synapse is less sensitive when the drug is removed, causing the postsynaptic cell to be under stimulated and you experience depressed emotions.

Organ System

different organs that work together to preform an overall function(s).

Circulatory (Organ System)

i. Circulatory- components are contractile element (heart or vessel), distribution network (blood vessels), blood or hemolymph. Function= Distributes solutes (nutrients, gases, wastes) to all parts of the animal's body

Digestive (organ system)

i. Digestive- components are ingestion structure (mouth), storage structure (Stomach), digestive and absorptive structures (Stomach, intestines), elimination structures (anus), accessory structures (pancreas, gallbladder). 1. Function= Breaks complex food into absorbable units, absorbs organic molecules, and eliminates solid waste.

Endocrine (organ system)

i. Endocrine- components are all cells, tissues, organs, or glands that secrete hormones. 1. Function= Regulates and coordinates growth, development, metabolism, mineral balance, water balance, blood pressure, behavior, and reproduction.

Excretory (Organ system)

i. Excretory- Components are respiratory structures that are involved in removing soluble waste from body; vertebrate urinary system is a part of this system (kidney, bladder, ureters, and urethra) 1. Function= eliminates soluble metabolic wastes, regulates body fluid volume and solute concentrations.

Immune and lymphatic (organ system)

i. Immune and lymphatic- circulating white blood cells, lymph organs, lymph vessels and nodes. 1. Function= Defends against pathogens

Integumentary- body surfaces (skin) (Organ Systems)

i. Integumentary- body surfaces (skin) 1. Function= Protects from desiccation and injury, defends against pathogens, in some animals it plays the role of regulation of body temp.

Muscular-Skeletal (organ system)

i. Muscular-skeletal- Force- producing structures (muscles), support structures (bones, cartilage, exoskeleton), connective structures (ligaments, tendons). 1. Produces locomotion, generates force, propels materials through body organs, supports body.

Nervous (Organ System)

i. Nervous- Processing (brain), sensory structures, signal delivery (spinal cord, peripheral nerves, and ganglia, sense organs) Function= Regulates and coordinates movement, sensation, organ functions, and learning

Reproductive- Gonads and associated structures (organ system)

i. Reproductive- Gonads and associated structures 1. Function= produces gametes, in some animals provides nutritive environment for embryo and fetus.

Respiratory (Organ System)

i. Respiratory- Gas-exchange sites (gills, skin, trachea, lungs) 1. Function= Exchanges oxygen and carbon dioxide with the environment, regulates blood pH.