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A series of answers to neuroanatomical and biochemical questions related to neurophysiology and homeostasis. Topics covered include the primary mechanism of maintaining homeostasis, the production of myelin sheaths around neuron axons, the function of second messenger systems, neurotransmitters, and their receptors, the electrochemical forces acting on sodium and potassium ions, and the role of myelin in increasing action potential conduction velocity.
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Which of the following statements about homeostasis is FALSE? a.) Homeostasis is the maintenance of the internal environment b.) The organ systems work together to maintain homeostasis c.) Illness can result if homeostasis is disrupted d.) The primary mechanism to maintain homeostasis is positive feedback e.) The extracellular fluid is maintained in a state compatible for life - ANS>> d.) The primary mechanism to maintain homeostasis is positive feedback What type of cell produces myelin sheaths around axons of neurons in the central nervous system? - ANS>> oligodendrocyte In a neuron, where are voltage-gated calcium channels located? - ANS>> axon termnial The body fluid compartment with a high potassium and protein concentration is _________. - ANS>> intracellular fluid In most homeostasis mechanisms, a ________ detects a change in a regulated variable and sends that information to a(n) _________ which relays signals to a(n) _________. - ANS>> sensor; integrating; center; effector The function of a second messenger system is to - ANS>> amplify the response of the first messenger Parasympathetic preganglionic neurons release the neurotransmitter _______; sympathetic preganglionic neurons release the neurotransmitter ______. - ANS>> acetylcholine; acetylcholine The electrochemical gradient for sodium across the membrane is such that the net flux for sodium movement is directed ________, thereby causing the cell's membrane potential to become more _______. - ANS>> inward; positive Which of the following cells would have a greater electrical attraction for sodium ions to enter the cell? a.) cell with membrane potential =-70mV b.) cell with membrane potential = 0mV c.) cell with membrane potential =-90mV d.) cell with membrane potential =+20mV e.) cell with membrane potential =-50mV - ANS>> c.) cell with membrane potential =- 90mV As the number of receptors on the cell membrane decreases, the response of the target cell will ________. - ANS>> decrease
Page | 2 Which of the following transport mechanisms requires energy? - ANS>> both primary and secondary active transport True or False. Synaptic communication to a skeletal muscle cell via a somatic motor neuron can be excitatory or inhibitory - ANS>> False Based solely upon its negative electrical charge, the inside of a typical cell will tend to attract extracellular _____ to move inward - ANS>> cations Parasympathetic postganglionic neurons release the neurotransmitter ________; sympathetic postganglionic neurons release the neurotransmitter ________. - ANS>> acetylcholine; norepinephrine Much evidence suggests that clinical depression is associated with deficiencies in the biogenic amines serotonin and norepinephrine. If this is true and the body has reduced concentrations of these amines, one might predict the body would _____ in order to adapt to these lowered levels. - ANS>> up-regulate receptors for these messengers What is a molecule that is similar in structure to a messenger and binds with that messenger's receptor to stimulate a similar response from the target cell? - ANS>> agonist Which of the following best describes the function of myelin? - ANS>> increase action potential conduction velocity When molecules are passively transported across a membrane, the direction of their movement is dictated by the molecule's tendency to move ________. - ANS>> from higher concentration to lower concentration Which of the following endocrine glands is innervated by sympathetic preganglionic neurons? a.) anterior pituitary b.) thyroid gland c.) adrenal medulla d.) adrenal cortex e.) pancreas - ANS>> c.) adrenal medulla Which of the following compartments contain most of the water found in the human body? - ANS>> intracellular fluid What two divisions of the autonomic nervous system have opposite effects on the organs they innervate? - ANS>> parasympathetic and sympathetic Where do the preganglionc neurons of the sympathetic nervous system emerge from the spinal cord? - ANS>> thoracic and lumbar regions
Page | 4 The potassium equilibrium potential is - 94mV. What does this mean? - ANS>> At - 94 mV, the chemical force for potassium movement is opposed exactly by the electrical force Extracellular fluid is composed of - ANS>> interstitial fluid and plasma A carrier is a transmembrane protein that moves across the membrane and through - ANS>> conformational changes in the protein shape The affinity of a receptor for its messenger is a measure of the - ANS>> strength of bind between messenger and receptor The bulk of ATP production is performed in which organelle? - ANS>> mitochondria With respect to their innervation, individual skeletal muscle cells are innervated by________. - ANS>> a single motor neuron Which of the following best describes the electrochemical forces acting on sodium and potassium ions across the membrane? a.) Forces on both sodium and potassium ions are to move into the cell b.) The force on sodium ions is to move out of the cell, and the force of potassium ions is to move into the cell c.) The force on sodium ions is to move into the cell, and the force on potassium ions is to move out of the cell d.) Forces on both sodium and potassium ions are to move out of the cell e.) There is no force on either ion to move - ANS>> c.) The force on sodium ions is to move into the cell, and the force on potassium ions is to move out the cell The adrenergic receptors have the greatest affinity for what messenger? - ANS>> norepinephrine Heroin overdose is usually treated with an opioid ______, such as naloxone (Narcan) which prevents heroin from binding to opiate receptors and reverses the effects of heroin on the body - ANS>> antagonist What is the neurotransmitter released from somatic neurons? - ANS>> acetylcholine Tissues in the body are classified into which of the following broad types? - ANS>> Nervous, muscle, epithelial, and connective Ion channels are examples of what type of membrane protein? - ANS>> transmembrane protein Students who suffer from test anxiety often have some of the following symptoms: the need for frequent urination, dilated pupils, and elevated heart rate. What branch of their autonomic nervous system would cause these symptoms? - ANS>> sympathetic
Page | 5 What type of cell junctions allow the passage of small molecules and ions from the cytosol of one cell to that of a neighboring cell? - ANS>> gap junctions Which of the following cell membrane transport mechanisms is passive? a.) co-transport of glucose with sodium b.) movement of calcium via a Ca-ATPase (Ca pump) c.) transport of sodium and potassium across the membrane by the Na+/K+ pump d.) movement of sodium through ion channels e.) counter-transport of hydrogen ions with sodium - ANS>> d.) movement of sodium through ion channels Which of the following accurately represents the order of complexity for the body, from least to most complex? a.) organ systems, cells, tissues, organs b.) cells, tissues, organs, organ systems c.) tissues, cells, organs, organ systems d.) organ systems, organs, tissues, cells e.) cells, tissues, organ systems, organs - ANS>> b.) cells, tissues, organs, organ systems What type of ion channels in the membrane of neuron axons open in response to the membrane potential being depolarized to threshold? - ANS>> voltage-gated channels Chronic exposure to a chemical messenger ________ the receptor population for that chemical messenger on the target cell, thus reducing the cells response to the messenger. - ANS>> down regulates The neurotransmitter that is released from the presynaptic neuron must diffuse across the ______ to reach its receptor on the postsynaptic neuron. - ANS>> synaptic cleft Which of the following will NOT affect the magnitude of a target cell's response to a specific chemical messenger? - ANS>> molecular weight of the messenger Tissues in the body are classified into which of the following four primary types? - ANS>> nervous, muscle, epithelial, and connective tissues What is the primary mechanism for maintaining homeostasis? - ANS>> Negative feedback Molecules with a high lipid solubility are capable of crossing the membrane _________.
Page | 7 The influx of calcium into the axon terminal of a chemical synapse is responsible for which of the following? - ANS>> release of neurotransmitter from axon terminal What type of ion channel is directly responsible for generating action potentials on the axon of neurons? - ANS>> voltage-gated What is the mode of action of a chemical messenger that, when released, binds to receptors on the same cell that released the chemical messenger? - ANS>> autocrine What is a molecule that is similar in structure to a chemical messenger and binds with that messenger's receptor to stimulate a similar response from the target cell? - ANS>> agonist At the axon hillock of neurons, what happens to the resting membrane potential of - 72mV when voltage-gated sodium channels open? - ANS>> depolarization of the membrane potential In secondary active transport with sodium, which of the following is FALSE? - ANS>> the molecule being co-transported with sodium always moves from high to low concentration In passive diffusion, molecules tend to move spontaneously ______ their concentration gradient, from high concentration to low concentration. - ANS>> down Referring to a membrane as "selectively permeable" describes its ability to _________.
Page | 8 Homeostasis is a term which describes the process whereby the body ________________. - ANS>> maintains an internal environment compatible with life Regarding the transport of ions across cell membranes, what type of ion channels behave as though they are always open and constantly allows ions to move across the membrane? - ANS>> leak channels How can action potentials relay information about the intensity of a stimulus, such as distinguishing between a warm and hot skin temperature? - ANS>> due to the frequency of action potentials Which of the following components of the plasma membrane forms ion channels? - ANS>> transmembrane proteins Differences in the rate of opening between fast and slow gated ion channels is caused by _________. - ANS>> G protein activity For most homeostasis mechanisms _____________ detects a change in a regulated variable and sends that information to a(n) ___________ which relays signals to a(n) ___________, usually a muscle of a gland which returns the variable to the set point. - ANS>> sensor: integrating center: effector For facilitated diffusion, the carrier is a transmembrane protein that moves molecules across the membrane through ____________. - ANS>> changes in configuration of the transporter