BI231 Lecture Exam #2 PDF

1. What do osteoblasts and -clasts do? How do these relate to bone and blood? How does activity of these cells affect bone mass? - Osteoblasts: create new bone tissue and add growth to existing bone. They also secrete molecules that can improve bone repair and development....

1. What do osteoblasts and -clasts do? How do these relate to bone and blood? How does activity of these cells affect bone mass? - Osteoblasts: create new bone tissue and add growth to existing bone. They also secrete molecules that can improve bone repair and development. - Osteoclasts: dissolve old and damaged bone tissue so it can be replaced by new bone. They break down bone on the inner surface of the bone, which allows the bone to thicken without becoming too heavy. - Relationship between bone/blood: this dynamic balance between the two cell types is crucial for maintaining healthy bone mass and regulating blood calcium levels by releasing calcium from bone when needed. - Bone mass: when osteoblasts are more active, bone mass increases, and when osteoclasts are more active, bone mass decreases. 2. What are two main ways to build a bone? What are the basic steps of each? When and where in your body do these occur? - Intramembranous ossification: 1) mesenchymal cell condensation, 2) differentiation into osteoblasts, 3) osteoid secretion and calcification, 4) formation of trabecular bone and periosteum. This process occurs in the embryo and continues into adolescence. It forms bones from mesenchymal connective tissue in the skull, clavicles, and flat bones of the face. - Endochondral ossification: 1) cartilage model formation, 2) blood vessel invasion and cartilage breakdown, 3) bone collar formation, 4) primary ossification center development, 5) secondary ossification center development (in epiphyses) and remodeling. This process occurs in adolescence and continues into young adulthood. It forms bones by replacing hyaline cartilage in the long bones, the ends of flat and irregular bones, and the base of the skull. 3. How do diet, sun, and exercise relate to bone mass? - Diet: - Calcium: the primary mineral needed for bone building, found in dairy products, leafy greens, and fortified foods. - Vitamin D: essential for calcium absorption, primarily obtained through sunlight exposure but also found in certain foods. - Protein: supports bone health and repair. - Sun Exposure: - Vitamin D synthesis: when skin is exposed to sunlight, the body produces vitamin D, which is crucial for calcium absorption and bone health. - Exercise: - Weight-bearing activities: exercises like walking, running, and stair climbing put stress on bones, stimulating bone formation and increasing density.  - Resistance training: strength training exercises further enhance bone density by adding stress to the bone structure. 4. Specifically, know how Vitamin D is made and how it affects calcium levels. - Sunlight exposure: The skin produces vitamin D3 when exposed to ultraviolet B (UVB) radiation from sunlight. The amount of vitamin D produced depends on the amount of UVB radiation that reaches the skin, as well as the amount of 7-dehydrocholesterol in the skin. - Liver processing: vitamin D3 is transported to the liver, where it's hydroxylated to become 25-hydroxyvitamin D3, also known as calcidiol. - Kidney processing: 25-hydroxyvitamin D3 is then transported to the kidneys, where it's hydroxylated again to become 1,25-dihydroxyvitamin D3, also known as calcitriol. Calcitriol is the most potent form of vitamin D. - Calcium levels: calcium is actively absorbed from the small intestine in the presence of vitamin D. Calcium and phosphorus form hydroxyapatite crystals to mineralize and strengthen bones. Thus, a diet containing both optimal vitamin D and calcium is important for proper mineralization of bone. 5. What are the hormones that affect bone mass? What is the action of each one? How do conditions such as menopause affect these? - Estrogen: helps maintain bone formation and breakdown balance in both men and women. Estrogen levels drop during menopause, which can lead to osteoporosis due to dropped estrogen levels. - Testosterone: promotes bone formation and reduces bone breakdown in men. Testosterone levels decrease with age, which can lead to bone loss. 6. Explain osteoporosis, rickets, and paget’s disease and relate it to the things above. - Osteoporosis, rickets, and Paget's disease are all bone disorders that can weaken bones and increase the risk of fractures: - Osteoporosis: A common condition that occurs when bones lose mineral density and become brittle. It's especially common in older people, and is often caused by exposure to high levels of glucocorticoids. - Rickets: A childhood condition that occurs when bones don't mineralize properly. Symptoms include delayed growth, bow legs, and muscle weakness. It's treated with vitamin D or calcium supplements, medications, or surgery. - Paget's disease: A chronic condition that occurs when the body builds new bone faster than it breaks down old bone. This results in thickened, misshapen bones that are weaker than normal. Symptoms include bone pain, and complications can include broken bones, hearing loss, and pinched nerves. It's most common in people over 50, and is more common in men than women. 7. What are the joints of the body in terms of structure and function? Give examples of each. - Fibrous joints (immovable/synarthrosis): the sutures between skull bones. - Cartilaginous joints (slightly movable/amphiarthrosis): the intervertebral discs between vertebrae in the spine and the pubic symphysis in the pelvis. - Synovial joints (freely movable/diarthrosis): the knee joint, shoulder joint, elbow joint, and hip joint. 8. What tissues make up the join types? Can you identify a joint type from characteristics given? - Cartilage: a connective tissue that covers the articular surfaces of joints - Ligaments: tough bands of connective tissue that connect bones together, providing stability and limiting joint movement. - Tendons: strong cords of connective tissue that attach muscles to bones, enabling movement. - Synovial membrane: a thin lining inside the joint capsule that produces synovial fluid, a lubricating substance that helps joints move smoothly. 9. What makes a synovial joint unique? - Synovial joints are unique because they have a joint cavity, articular cartilage, and synovial fluid, which allow them to move freely and with minimal friction. 10. How does the sodium-potassium pump (Na/K pump) work? What ions move in that way, in what number? What is the purpose of this pump? - Transports three sodium ions (Na+) out of a cell and two potassium ions (K+) into the cell for every cycle, using energy from ATP, thereby maintaining a concentration gradient across the cell membrane with a higher sodium concentration outside and a higher potassium concentration inside. This is crucial for establishing and maintaining the cell's resting membrane potential, particularly important for nerve impulse transmission. 11. What is a resting membrane potential (RMP)? What is its value? What are the ions involved? - It’s the electrical voltage difference across a cell membrane when the cell is at rest, typically around -70 millivolts (mV), and is primarily maintained by the unequal distribution of ions like sodium (Na+) and potassium (K+) across the membrane. 12. Explain the steps to formation of an action potential (AP) “in word and deed” meaning in writing and in pictures. - Depolarization (sodium ions rapidly influxing the cell), followed by an overshoot, then repolarization (potassium ions leaving the cell), and finally a hyperpolarization phase where the membrane potential briefly becomes more negative than the resting state. 13. Regarding an AP: Can you identify the net charge, movement of ions, and state of the channels at a given point during an AP? When is the neuron depolarized, repolarized, or hyperpolarized? Specifically label a graph of an AP with the above. 14. What are the glial cells and their functions? Where is each located? - Astrocytes/CNS: most abundant glial cells, providing structural support, regulating blood flow to the brain, maintaining ion balance, and participating in the blood-brain barrier. - Oligodendrocytes/CNS: responsible for forming the myelin sheath around axons, which insulates and speeds up signal transmission. - Microglia/CNS: act as the immune cells, engulfing debris, damaged cells, and pathogens. - Ependymal cells/CNS: line the ventricles of the brain and central canal of the spinal cord, producing cerebrospinal fluid. - Schwann cells/PNS: responsible for forming myelin sheaths around axons. - Satellite cells/PNS: located in the peripheral ganglia, they surround neuronal cell bodies and provide structural support and maintain a stable chemical environment. 15. How is a nerve signal propagated down an axon? How does continuous and saltatory conduction differ in this process? How does myelin affect this process? - Action potentials travel down a single neuron cell as an electrochemical cascade, allowing a net inward flow of positively charged ions into the axon. - Continuous conduction involves signal propagation along an unmyelinated axon and is relatively slow due to continuous opening of voltage-gated channels. Saltatory conduction, by contrast, involves rapid signal propagation along a myelinated axon due to the 'leaping' action potential across myelinated areas. - Myelin acts as an insulator, significantly speeding up this process by forcing the signal to "jump" between gaps in the myelin called nodes of Ranvier, a phenomenon known as saltatory conduction. 16. What is a refractory period and when does it occur? - Its a brief time period immediately following a nerve impulse or muscle contraction where a cell is unable to respond to further stimulation, essentially a recovery phase where the cell cannot generate another action potential, occurring right after an action potential has been fired; this is due to the inactivation of voltage-gated sodium channels involved in the depolarization process. 17. Know the steps to crossing a synapse. Be able to identify something as pre- or postsynaptic. 18. Know how neurotransmitters, receptors, and “reuptake” all relate. How would changing one affect the others? - Neurotransmitters are chemical messengers released by neurons that bind to specific receptors on other neurons to transmit signals. "Reuptake" is the process where the released neurotransmitter is actively taken back up by the original neuron, allowing for the recycling and reuse of the neurotransmitter, while the receptors on the receiving neuron are the specific sites where the neurotransmitter binds to initiate a signal. 19. Know the table of neurotransmitters-name, type, location. 20. Know what makes a postsynaptic potential an EPSP or an IPSP physiologically. - Intuitively, this rule can be understood by realizing that an EPSP will tend to depolarize the membrane potential so that it exceeds threshold, whereas an IPSP will always act to keep the membrane potential more negative than the threshold potential. 21. Know the anatomical and physiological differences in the ANS between sympathetic and parasympathetic responses. (Know the chart.) - The sympathetic system originates in the thoracic and lumbar regions (thoracolumbar outflow), while the parasympathetic originates in the brainstem and sacral region (craniosacral outflow) 22. State how organs will function during sympathetic or parasympathetic innervation, and why this response makes sense. - During sympathetic innervation, organs generally function in a "fight-or-flight" mode, increasing heart rate, blood pressure, and alertness while inhibiting digestion, whereas parasympathetic innervation promotes "rest-and-digest" functions by slowing the heart rate, stimulating digestion, and facilitating relaxation; this response makes sense because it prepares the body for immediate action in stressful situations with the sympathetic system and conserves energy during calm periods with the parasympathetic system.