the basic structural unit of the nervous system is a nerve cell, or neuron. it consists of the...

The basic structural unit of the nervous system is a nerve cell, or neuron. It consists of the following parts: 1.The cell body or soma, which contains the nucleus and other cellular organelles. 2.The dendrite, which is typically a short, branched, slender extension of the cell body that receives stimulus. 3. The axon, which is typically a long, slender extension of the cell body that sends nerve impulses. A nerve impulse begins at the dendrite, passes through the dendrites to the cell body, then through the axon, and finally terminates at the branches of the axon.

Neurons are classified into three general groups by their functions. Sensory Neurons Motor Neurons Association Neurons AKA Afferent neurons, receive the initial stimulus. Sensory neurons embedded in the retina are stimulated by light, while sensory neurons in the hand are stimulated by touch. AKA efferent neurons, stimulate effectors, or target cells that produce some kind of response. They may stimulate muscles which create movement to help maintain balance, or to avoid pain AKA interneurons neurons are located in the spinal cord or brain (CNS) and receive impulses from sensory neurons or send impulses to motor neurons. They are integrators, evaluating impulses for appropriate responses.

The transmission of a nerve impulse along a neuron from one end to the other occurs as a result of electro-chemical changes across the membrane of the neuron. The membrane of an unstimulated neuron is polarized. There is a difference in electrical charge between the outside and inside of the membrane. The inside is negative, with respect to the outside. This differential is established by the cell maintaining and excess of Na + ions on the outside and an excess of K + ions on the inside. A certain amount of Na + and K + is always leaking across the membrane, but Na+/K+ pumps in the membrane actively restore the ions to the appropriate side. The large negatively charged protein, and nucleic acids also account for overall negative charge of the inside of the cell. The sodium potassium pump is an active transport mechanism, and as such, it requires the addition of energy. It receives this energy from a phosphate group donated by ATP, which bonds to a portion of the transport channel.

Three sodium ions (Na+) bind to the protein channel and an ATP provides the energy to change the shape of the channel that in turn drives the ions through the channel.

The phosphate group donated by the ATP remains bound to the protein channel. The Na+ ions are released on the other side of the membrane outside of the cell, and the new shape of the channel has a high affinity for potassium ions and two of these ions now bind to the channel.

This binding of potassium (K+) again causes a change in the shape of the protein channel, and this conformational change releases the phosphate group on the cytoplasm side. This release allows the channel to revert to its original shape and as a result, the potassium ions are released inside the cell. Now, in its original shape, the channel again has a high affinity for Na + ions, and when these bind again, they initiate another cycle. The important thing about the Na + /K + pump, is that the ions in both cases are moving from an area of low concentration, to an area of high concentration. This movement is against the concentration gradient, which is why the process requires the input of energy from the ATP molecule.

The graph below characterizes the transmission of a nerve impulse. Resting Potential: describes the unstimulated, polarized state of a neuron (at about -70 millivolts) Action Potential: In response to a stimulus, gated ion channels in the membrane suddenly open and permit the Na+ on the outside to rush into the cell. As the positively charged Na + rush in, the charge on the cell membrane becomes depolarized, or more positive on the inside. If the stimulus is strong enough-that is, if it is above a certain threshold level- more Na + gates open, increasing the inflow of Na + even more, causing an action potential, or complete depolarization. This stimulates neighboring Na + gates to open down the entire length of the neuron (thus sending the message). The action potential is an all-or- nothing event. When the stimulus fails to produce a depolarization that exceeds the threshold value, no action potential results, but when threshold potential is exceeded, complete depolarization occurs.

Repolarization: in response to the inflow of Na +, another kind of gated channel opens, this time allowing the K + on the inside to rush out of the cell. The movement of K + out of the cell causes repolarization by restoring the original membrane polarization. Unlike the resting potential, however, the K + are on the outside and the Na + are on the inside. Soon after the K + gates open, the Na + gates close. Hyperpolarization: by the time the K+ gate channels close, more K+ have moved out of the cell than is actually necessary to establish the original polarized potential. Thus the membrane becomes hyperpolarized (about -80 millivolts)

Refractory Period: with the passage of the action potential, the cell membrane is in an unusual state of affairs. The membrane is polarized, but the Na + and K + are on the wrong sides of the membrane. During this period, the neuron will not respond to a new stimulus. To reestablish the original distribution of these ions, the Na + and K + are returned to their resting potential location by Na + /K + pumps in the cell membrane. Once these ions are completely returned to their resting potential location, the neuron is ready for another stimulus.

Some neurons possess a myelin sheath, which consists of a series of Schwann cells that encircle the axon. The Schwann cells act as insulators and are separated by gaps of unsheathed axon called nodes of Ranvier. Instead of traveling continuously down the axon, the action potential jumps from node to nod, thereby speeding the propagation of the impulse. A synapse, or synaptic cleft, is the gap that separates adjacent neurons. Transmission of an impulse across a synapse, from presynaptic cell to postsynaptic cell, may be electrical or chemical.

In electrical synapses, the action potential travels along the membranes of gap junctions, small tubes of cytoplasm that connect adjacent cells. In most animals, however, most synaptic clefts are traversed by chemicals. This chemical process occurs as follows: 1. Calcium (Ca 2+ ) gates open: When an action potential reaches the end of an axon, the depolarization of the membrane causes gated channels to open and allow Ca 2+ to enter the cell. 2.Synaptic vesicles release neurotransmitter: The influx of Ca 2+ into the terminal end of the axon causes synaptic vesicles to merge with the presynaptic membrane, releasing molecules of a chemical called a neurotransmitter into the synaptic cleft. 3. Neurotransmitter binds with postsynaptic receptors: the neurotransmitter diffuses across the synaptic cleft and binds with proteins on the postsynaptic membrane. Different proteins are receptors for different neurotransmitters.

4. The Postsynaptic membrane is excited or inhibited: Depending upon the kind of neurotransmitter and the kind of membrane receptors, there are two possible outcomes for the postsynaptic membrane: (Excited) If Na+ gates open, the membrane becomes depolarized and results in an excitatory postsynaptic potential. If the threshold potential is exceeded, and action potential is generated, and the signal continues. (Inhibited) If K+ gates open, the membrane becomes more polarized (hyperpolarized) and results in an inhibitory postsynaptic potential. As a result, it becomes more difficult to generate an action potential on this membrane.

5. The neurotransmitter is degraded and recycled: After the neurotransmitter binds to the postsynaptic membrane receptors, it is broken down by enzymes in the synaptic cleft. For example, a common neurotransmitter, acetylcholine, is broken down by cholinesterase. Degraded neurotransmitters are recycled by the presynaptic cell. Some common neurotransmitters and the kind of activity they generate are summarized below: Acteylcholine is commonly secreted at neuromuscular junctions, the gaps between motor neurons and muscle cells, where it stimulates muscles to contract. Epinephrine, norepinephrine, dopamine, and serotonin are derived from amino acids and are mostly secreted between neurons of the CNS Gamma aminobutyric acid (GABA) is usually an inhibitory neurotransmitter among neurons in the brain.

The two parts of the nervous system are: 1.The CNS (Central Nervous System) Or the brain and spinal cord 2. The PNS (Peripheral Nervous System) This contains sensory neurons that transmit impulses to the CNS and motor neurons that transmit impulses from the CNS to the effectors. The motor neuron system can be divided into two groups as follows: The somatic nervous system directs the contraction of skeletal muscles. The autonomic nervous system controls the activities of organs and various involuntary muscles, such as cardiac and smooth muscles.

To make things even more complicated, the autonomic nervous system is divided as well: The sympathetic nervous system: involved in the stimulation of activities that prepare the body for action, such as increasing the heart rate, increasing the release of sugar from the liver into the blood, and other activities generally considered as fight-or-flight responses (responses that serve to fight off or retreat from danger) The parasympathetic nervous system activates tranquil functions, such as stimulating the secretion of saliva or digestive enzymes into the stomach.

Both sympathetic and parasympathetic tend to target the same organs, but often they work antagonistically. For example, the sympathetic system accelerates the cardiac cycle, while the parasympathetic slows it down. Each system is stimulated as is appropriate to maintain homeostasis. A reflex arc is a rapid, involuntary response to a stimulus. It consists of two or three neurons-a sensory and motor neuron and, in some reflex arcs, an interneuron. Although neurons may transmit information about the reflex response to the brain, the brain does not actually integrate the sensory and motor activities. Example: Sneeze reflex Interneuron

There are two animal body systems that are responsible for releasing the chemical signals that regulate bodily functions. These are the endocrine, and the nervous systems. While the nervous system releases neurotransmitters, the endocrine releases hormones. Hormones produced in ductless glands, moving through blood to specific target tissue or organs. Notice that some of these endocrine glands are also part of other systems! Go to my webpage calendar for a complete list of all the hormones, sources, targets, and actions that youll need to know for the test!

The two types of hormones are Lipid (steroid) hormones Protein (peptide) hormones Diffuse directly through the plasma membrane and bind to a receptor inside the nucleus that triggers the cells response Cannot diffuse through the plasma membrane, so they bind to a receptor on the surface. This triggers secondary messenger inside cell, converting the signal to a response.

The function of many animal systems is to contribute toward homeostasis, or maintenance of stable, internal conditions within narrow limits. Such is the case with the endocrine system. In many cases, homeostasis is maintained by negative feedback. A sensing mechanism (a receptor) detects a change in conditions beyond specific range. A control center, or integrator (often the brain), evaluates the change and activates a second mechanism (an effector) to correct the condition.

In negative feedback, the original condition is negated, so that the conditions are returned to normal. (see below) Compare this with positive feedback, in which an action intensifies a condition so that it is driven further beyond normal limits. (Lactation is stimulated in response to increased nursing of an infant.

Drink a glass of milk or eat a candy bar and the following (simplified) series of events will occur: Glucose from the ingested lactose or sucrose is absorbed in the intestine and the level of glucose in blood rises. Elevation of blood glucose concentration stimulates endocrine cells in the pancreas to release insulin. Beta cells within the islets of Langerhans Insulin has the major effect of facilitating entry of glucose into many cells of the body - as a result, blood glucose levels fall. Liver and muscle cells convert the glucose to glycogen (for storage), and adipose cells which convert the glucose to fat. Either way, glucose is reduced. When the level of blood glucose falls sufficiently, the stimulus for insulin release disappears and insulin is no longer secreted. Alpha cells within the islets of Langerhans secrete glucagon into the blood, which stimulates the liver to release the stored glucose.

There are two types of skeletal systems. An exoskeleton can be found on many invertebrate arthropods, such as insects and crustaceans. It is a chitinous skeleton surrounding the exterior of the organism. It serves to anchor internal organs, and provide support and protection for body systems. The other type of skeleton is the one we are most familiar with, because we have one ourselves! It is an endoskeleton. This skeleton serves to protect and support us from within our bodies. All vertebrates (except some very primitive fishes) have a complex bony skeleton.

Provides a framework and support structure for the tissues of your body to attach to Protects your internal organs, including your heart, lungs, and brain Produces red blood cells, and some white blood cells A storehouse for minerals such as calcium and phosphorous Along with muscles, acts to help the body with locomotion and other movement The adult human skeleton has 206 bones, give or take. All bony tissue is not the same, however. Compact bone: the outer most dense bony material Spongy bone: inner porous less dense bone Marrow: soft material in the inner cavity of bone

They are long tubular systems which run the length of compact bone tissue, and contain nerves and tiny blood vessels Bone marrow is a special, spongy, fatty tissue that houses stem cells, located inside a few large bones. These stem cells transform themselves into white and red blood cells and platelets, essential for immunity and circulation. Anemia, leukemia, and other lymphoma cancers can compromise the resilience of bone marrow. Our skull, sternum, ribs, pelvis, and femur bones all contain bone marrow, but other smaller bones do not. Inside this special tissue, immature stem cells reside, along with extra iron. While they are undifferentiated, the stem cells wait until unhealthy, weakened, or damaged cells need to be replaced. A stem cell can turn itself into a platelet, a white blood cell like a T-cell, or a red blood cell. This is the only way such cells get replaced to keep our body healthy. Found inside compact bone

Humans and other vertebrates contain three types of muscle tissue: Skeletal muscle Smooth muscle Cardiac muscle Attached to bones and causes movements of the body. Lines the walls of blood vessels and digestive tract where it serves to advance the movement of substances. Contraction is controlled and slow, as it is formatted differently than the striated skeletal muscles. Responsible for the rhythmic contractions of the heart. These are striated as the skeletal muscles are, but it is highly branched with cells connected by gap junctions (very important for the rapid electrical synapses necessary to contract the heart muscle)

Consists of numerous muscle cells called muscle fibers. Muscle fibers are multifaceted and consist of: The Sarcolemma The Sarcoplasm The plasma membrane of the muscle cell, is highly invaginated by transverse tubules (or T tubules) that permeate the cell) The cytoplasm of the muscle cell, contains calcium-storing sarcoplasmic reticulum, the specialized ER of a muscle cell. Skeletal muscle cells are multinucleated. They lie along the periphery of the cell, forming swellings in the sarcolemma. The entire volume of the muscle cell is filled with numerous myofibrils.

Muscle Vocab: Myofibrils, the chief component in muscles. Actin: Thin Myosin: Thick Sarcomere: region between Z lines

Myofibrils consist of two types of filaments. Thin filaments composed of the globular protein actin arranged in a double helix. Troponin and tropomyosin molecules cover special binding sites on the actin. Thick filaments composed of myosin. Each myosin filament forms a protruding head at one end. Within a myofibril, actin and myosin filaments are parallel and arranged side by side. The overlapping filaments produce a repeating pattern that gives skeletal muscle a striated appearance. Each repeating unit of the pattern is called a sarcomere.

Each actin filament is attached to a Z-line, which is found at either end of the sarcomere. The thick myosin filaments lie between the Z-lines, but are not attached. When muscles contract, sarcomeres shorten, however, actin and myosin fibers remain the same length. They simply slide past one another. Z-Line

The action potential arrives at the nerve terminal and causes the release of a chemical called acetylcholine. Acetylcholine travels across the neuromusclualr junction and stimulates the sarcoplasmic reticulum to release its stored calcium ions throughout the muscle. As calcium is released it binds with a protein called troponin that is situated along the actin filaments. It is this binding that causes a shift to occur in another chemical called tropomyosin. Because these chemicals have a high affinity for calcium ions, they cause the myosin cross bridges to attach to actin and flex rapidly.

ATP binds to a myosin head and forms ADP + P i When ATP binds to a myosin head, it is converted to ADP and Pi, which remain attached to the myosin head. Ca 2+ exposes the binding sites on the actin filaments Calcium binds to the troponin molecule causing tropomyosin to expose positions on the actin filament for the attachment of myosin heads Cross bridges between myosin and actin form When attachment sites on the actin are exposed, the myosin heads bind to actin to form cross bridges. ADP and P i are released and sliding motion results Attachment of cross bridges causes release of ADP and P i, changing shape of myosin head, pulling the two Z-lines together, contracting fiber.

Large organisms require a transport system to distribute nutrients and oxygen and to remove wastes from cells. Two kinds of circulatory systems accomplish this: Open Circulatory System: pump blood into an internal cavity called a hemocoel, or sinuses, which bathe tissues with an oxygen-and nutrient-carrying fluid called hemolymph. The hemolymph returns to the pumping mechanism of the system, a heart, through holes called ostia. Open circulatory systems occur in insects and most mollusks.

Closed Circulatory Systems: the nutrient, oxygen, and waste-carrying fluid, known as blood, is confined to vessels. Closed circulatory systems are found among members of the phylum annelida, certain mollusks, (octopuses and squids) and vertebrates. In the closed circulatory system of vertebrates, vessels moving away from the heart are called arteries. Arteries branch into smaller arterioles, and then branch further into the smallest vessels, capillaries. Gas and nutrient exchange occurs by diffusion across capillary walls into interstitial fluids and into surrounding cells. Wastes and excess interstitial fluids move in the opposite direction as they diffuse into capillaries. The blood, now deoxygenated, remains in the capillaries and returns to the heart through venules, which merge to form veins. The heart then pumps the deoxygenated blood to the respiratory organ (gills or lungs), where arteries again branch into a capillary bed for gas exchange. The oxygenated blood then returns to the heart through veins. From here, the oxygenated blood is pumped once again, through the body.

KNOW the path of blood through the body, heart, and lungs!!! KNOW in which vessels it is deoxygenated and in which vessels it is oxygenated.

The pathway of blood between the right side of the heart, to the lungs, and back to the left side of the heart is called the pulmonary circuit. The circulation pathway throughout the body is the systemic circuit. The cardiac or heart cycle: refers to the rhythmic contraction and relaxation of heart muscles. It is regulated by specialized tissues in the heart called autorhythmic cells, which are self-excitable and able to initiate contractions without external stimulation by nerve cells. The cycle occurs as follows: The SA (sinoatrial) node, or pacemaker: found in upper wall of right atrium, spontaneously initiates the cycle by simultaneously contracting both atria and also sending a delayed impulse that stimulates the AV (atrioventricular) node. The AV node found in the lower wall of the right atrium sends an impulse through the bundle of His, nodal tissue that passes down between both ventricles and then branches into the ventricles through the Purkinje fibers. This impulse results in the contraction of the ventricles. When the ventricles contract (the systole phase), blood is forced through the pulmonary arteries and aorta. Also the AV valves are closed. When the ventricles relax (the diastole phase), backflow into the ventricles causes the semilunar valves to close. The closing of the AV valves, followed by the closing of the semilunar valves, produces the characteristic lub-dub sound of the heart. Systolic pressure is therefore controlled by the left ventricle, while diasotlic pressure is controlled by the semilunar valve in the aorta.

Blood contains each of the following: Red blood cells (erythrocytes) transport oxygen and catalyze the conversion of CO 2 and H 2 O to H 2 CO 3 (Carbonic acid). Mature red blood cells lack a nucleus, thereby maximizing hemoglobin content and thus their ability to transport O 2. White blood cells (leukocytes) consist of five major groups of disease-fighting cells that defend the body against infection. Platelets are cell fragments that are involved in blood clotting. Platelets release factors that are involved in the conversion of the major clotting agent, fibrinogen, into its active form, fibrin. Threads of fibrin protein form a network that stops blood flow. Plasma is the liquid portion of the blood that contains various dissolved substances. WBCs: Monocytes; Neutrophiles, Eosinophiles, Basophiles, and Macrophages. (each has its own function within the blood)

Animals are grouped loosely by how their body temperatures are maintained: Ectotherms Endotherms Animals that obtain body heat from the environment. They are sometimes referred to as poikilotherms. All invertebrates, fish, amphibians, and reptiles are ectotherms. They rely on warmth in their environment to help get their bodies going. Animals that are able to generate their own body heat, internally. They are also referred to as homeotherms, because they maintain a constant temperature, regardless of their external environment. Cooling by evaporation Warming by metabolism Adjusting surface area to regulate temperature In addition, animals have behavioral patterns that help them conserve, or release heat. huddling together hibernating fluffing feathers or hair moving to the shade

1.Which of the following would normally contain blood with the least amount of oxygen? a. The left ventricle b. The left atrium c. The pulmonary veins d. The pulmonary arteries e. The aorta The pulmonary arteries are the ONLY arteries in the body that carry blood that is oxygen poor, to the lungs. The pulmonary veins are the ONLY veins that carry blood rich in O2, from the lungs to the heart.

2.Body temperature can be increased by all of the following EXCEPT: a.Muscle contraction b.Alcohol consumption, which results in vasodilation c.Increasing metabolic activity d.Puffing up feathers or hair e.Reducing blood flow to the ears Alcohol actually works to cool your body, as vasodilation brings more blood to the capillaries close to the surface of your skin, to release heat energy.

3. Systolic blood pressure is maintained by the a. Left atrium b. Right atrium c. Left ventricle d. Right ventricle e. Semilunar valves in the aorta Left ventricle pumps blood through the body and maintains systolic blood pressure. The semilunar valves of the aorta maintains the diastolic blood pressure by preventing movement of blood back into the ventricle.

4. A nerve impulse is usually transmitted from a motor neuron to a muscle a. By acetylcholine b. By a hormone c. By an action potential d. By Ca 2+ e. Through a reflex arc Acetylcholine is the neurotransmitter that communicates across a neuromuscular junction.

5.What occurs in a neuron during the refractory period following an action potential? a.ATP is regenerated from ADP + P i b.Na+ moves across the neuron membrane from outside to inside c.K+ moves across the neuron membrane from inside to outside d.Na+ on the inside and K+ on the outside exchange places across the neuron membrane e.The outside of the membrane becomes more negative with respect to the inside The Na+/K+ protein pumps in the membranes of neurons exchange Na+ and K+ so the concentrations on each side of the membrane can reach resting potential.

6.If only K+ gates open on the postsynaptic membrane, then a.The postsynaptic membrane releases a neurotransmitter b.An excitatory postsynaptic potential (EPSP) is established c.The postsynaptic neuron is stimulated d.The postsynaptic neuron is inhibited e.Ca 2+ is released When K+ gates are opened on the postsynaptic membrane, an inhibitory postsynaptic potential (IPSP) is established. This makes the membrane more polarized, and it is more difficult to establish an action potential.

7.All of the following are involved in the contraction of muscle cells EXCEPT a.Actin b.cAMP c.Myosin d.Tropomyosin e.troponin cAMP triggers the activity of specific enzymes as a secondary messenger, such as transferring the effects of hormones like glucagon and adrenaline (which cannot pass through the plasma membrane) It is not involved in muscle contraction.

8. Which of the following is the last step leading up to muscle contraction that occurs just before a myofibril contracts? a. Tropomyosin exposes binding sites on actin b. ATP binds to myosin c. Sarcoplasmic reticulum releases Ca 2+ d. ATP is converted to ADP + P i e. Action potential travels throughout T- tubules 1 This is the order of events during muscle contraction 2435

9. All of the following are involved in the regulation of blood glucose concentrations EXCEPT a. Glucagon b. Insulin c. The liver d. Melatonin e. The pancreas Melatonin is secreted by the pineal gland and is involved in maintaining various bio-rhythms, such as circadian rhythm.

the basic structural unit of the nervous system is a nerve cell, or neuron. it consists of the...

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