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UNC-Chapel Hill BIOL 252 - Homework 1

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Homework 1 (Lessons 1-3) Q1. The condition hypothyroidism is characterized by a decrease in the synthesis and secretion of the chemical thyroid hormone from the thyroid gland, an organ in the neck that is part of the endocrine system. Which level(s) of organization describe this condition (select all that apply)? [X] The thyroid gland is regulated by other hormones from the glands in the body at an organ system level. [X] At the tissue level groups of follicular cells that make the thyroid hormones form a spherical structure with a hollow interior called a follicle. [X] The endocrine system works with the cardiovascular system to allow transporting the hormones throughout the body functions at the organism level. [ ] The plasma membrane of follicular cells that are found in the thyroid gland is made up of phospholipid bilayer at the tissue level. Q2. A scar located on the ankle of the left leg would be considered _____ to the knee of the same leg. ( ) Anterior ( ) Superficial (X) Distal ( ) Inferior Q3. If body temperature increased above its normal range but was regulated by a positive feedback loops, what would likely occur? ( ) Decreased core body temperature ( ) Increased temperature in upper limbs only ( ) Decreased temperature in the torso only (X) None of the above Q4. What would occur in the skin of the desmosomes stopped functioning? (X) The skin would not be able to resist mechanical stress and break down easily ( ) The skin would not show any wrinkles ( ) The skin would become tougher and less likely to tear ( ) The skin would no longer be able to protect against bacterial infectionsQ5. Marfan syndrome is a genetic disorder resulting from an autosomal recessive mutation in the FBN1 (fibrilin) gene, which is involved in elastin fiber formation. Patients with Marfan syndrome have characteristic long limbs, often suffer from scoliosis (curvature of the spine) and are at an increased risk of an aortic rupture (the aorta is the major artery supplying oxygenated blood to the rest of the body). Why would abnormal elastin fibers cause the life-threatening risk of an aortic rupture observed in patients with Marfan syndrome? ( ) Abnormal elastin fibers result in adjacent cells not being able to form tight junctions, which is essential for aortic tissue formation. ( ) Abnormal elastin fibers alter the shape of a cell, automatically creating a stratified epithelium within the aorta. (X) Abnormal elastin fibers result in excessive tensile strength within the extracellular matrix, causing rigidity of the aortic tissue. ( ) Abnormal elastin fibers result in the disorientation of cells, resulting in the apical membrane of aortic cells making contact with the basement membrane. Q6. What component of ground substance adheres cells to each other and to their places within the extracellular matrix (ECM)? (X) Glycoproteins ( ) Glycoaminoglycans (GAGs) ( ) Hyaluronic acid ( ) Proteoglycans Q7. Where would you expect to observe stratified squamous epithelial tissue? (X) Anus ( ) Colon ( ) Lungs ( ) Trachea Q8. Ella has a neurological abnormality where she does not move or flinch when a ball is thrown in her direction. Doctors have confirmed that the abnormality does not have to do with the afferent division. This suggests that Ella has an abnormality in which division of the nervous system? ( ) Visceral motor division (X) Somatic motor division ( ) Somatic sensory division ( ) Visceral sensory divisionQ9. How many of the statements below are TRUE? A. Neurons myelinated by Schwann cells propagate action potentials at a faster rate than neurons myelinated by oligodendrocytes B. Astrocytes play an essential role in maintaining the blood brain barrier by anchoring blood vessels and neurons in place C. Satellite cells support the cell body of neurons present in the central nervous system D. Microglial cells produce cerebrospinal fluid and ependymal cells phagocytose dead neurons ( ) 0 of the above statements are true (X) 1 of the above statements are true ( ) 2 of the above statements are true ( ) 3 of the above statements are true ( ) 4 of the above statements are true [One statement above is true: B – Astrocytes play an essential role in maintaining the blood brain barrier by anchoring blood vessels and neurons in place. All other statements are false.] Q10. Which of the following statements is FALSE? (X) Neurons and neuroglial cells both fire action potentials ( ) Neurons and neuroglial cells are both found in the CNS and PNS ( ) Neurons and neuroglial cells physically interact in the CNS and PNS ( ) Neuron bundles in the PNS are called ganglia Q11. The dendrite of a neuron is capable of propagating an action potential. ( ) True (X) FalseQ12. How many of the following would be characterized as a facilitated diffusion transport mechanism? A) Leak channel B) Voltage-gated ion channel C) Ligand-gated ion channel D) Na+/K+ ATPase ( ) 0 ( ) 1 ( ) 2 (X) 3 ( ) 4 [Three of the above would be considered facilitated diffusion transport – leak channels, voltage-gated ion channels, and ligand-gated ion channels. The Na+/K+ ATPase would be considered primary active transport.] Q13. A hypothetical ion has an equilibrium potential of -45 mV. What should the voltage across the membrane be for there to be no net movement of the ion, even when the membrane is permeable to the ion? ( ) +90 mV ( ) +45 mV ( ) 0 mV (X) -45 mV ( ) – 90mV Q14. Which would best describe the resting membrane potential of a cell if we increased the intracellular concentration of Na+? ( ) The resting membrane potential would become more negative (e.g., -100 mv) because there would be a greater negative charge across the membrane (X) The resting membrane potential would become less negative (e.g., -50 mV) because there would be a smaller negative charge across the membrane ( ) The resting membrane potential would not change because the Na+/K+ ATPase is still active ( ) The resting membrane potential would not change because the equilibrium potential of Na is constant regardless of changes to concentrationQ15. If the resting membrane potential of a cell is -80 mV, which would best describe the membrane potential of the cell when it is hyperpolarized? ( ) -60 mV ( ) -80 mV (X) -100


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