Name Introduction to Mammalian Physiology Spring 2012 Exam II I Anatomy Label the following major parts of the nervous system 4 pts 1 Which is the most inferior part in the above diagram Which is the most anterior 2 pts Inferior Spinal cord Anterior Cerebrum or Forebrain 2 Label the following muscles of the body 10 pts Trapezius Pectoralis Major Biceps Brachii Deltoid Triceps brachii Rectus Abdominis Gluteus Maximus Rectus Femoris Biceps femoris Gastrocnemius Name II Resting Membrane Potential and Action Potentials 3 Calculate the equilibrium potential using the equation below for potassium K if the extracellular concentration outside the neuron is 3 mM and the intracellular concentration inside the neuron is 90 mM Show your work and don t forget units 8 pts E K 61 mV 1 x log 3mM 90mM E K 61 mV x log 0 033 E K 90 1 mV 4 A typical neuron at rest has a membrane potential of about 1 pt A B C D 0V 60 V 60 mV 60 mV 5 What single protein is responsible for generating the ion concentration gradients used to create the resting potential of the neuron and uses up to 70 of the brains energy in doing so 1 pt Na K ATP Pump 6 For a typical neuron at rest Circle the correct answer 4 pts Is the membrane more permeable to sodium or potassium Is the concentration of potassium outside the cell higher or lower Is the concentration of sodium inside the cell higher or lower Is the concentration of calcium inside the cell higher or lower 7 In myelinated nerve fibers where do action potentials occur 1 pt A cell body B nodes of Ranvier C Schwann cell D underlying myelin sheath E oligodendrocyte 8 a Draw an action potential on the axes below 2 pts Name b Label the axes of your graph giving numbers and units appropriate for initial resting membrane potential and the amplitude of an action potential 2 pts c Label the following on your graph 1 pt each Phase when sodium channels open Phase when potassium channels open Threshold 9 Why do many of the pharmacological treatments for inhibiting seizures target sodium channels What do most of these drugs do to sodium channels 4 pts Because epilepsy involves increases in the rhythmic firing of action potentials of large groups of neurons and sodium channels are an essential component to the action potential Most drugs bind to sodium channels and stabilize their inactivated state decreasing the amount of time they are open and limiting the number of action potentials neurons can fire III Synaptic Transmission and the Nervous System 10 Label the following figure of a neuromuscular junction 4 pts Name 11 Both alpha bungarotoxin and curare bind to the same neurotransmitter receptor Which receptor is involved Where in the body might you expect to find this receptor 4 pts They bind to the acetylcholine receptor at the neuromuscular junction You would expect to find this receptor expressed on muscle cells through the skeletal muscles of the body 12 List two functions of cerebral spinal fluid in the brain 4 pts Acts as a shock absorber to protects the soft nervous tissue which essentially floats in CSF Provides essential nutrients and removes waste products Maintains a normal ionic composition around neurons 13 The brain is so dependent on blood supply that disruption of blood flow i e a stroke for even a few minutes can result in irreversibly damage to the brain Describe one of the three reasons we discussed in class why the brain has a constant need for blood glucose other than a high metabolic rate 4 pts Neurons have very little glycogen Do not have access to fatty acids for energy Cannot use anaerobic metabolism 14 Afferent axons carry information from the periphery to the brain whereas efferent axons carry information from the brain to the periphery in the nervous system 4 pts IV Autonomic and Somatic Nervous System 15 2 pts Which autonomic branch is responsible for the following body functions Parasympathetic Rest and Digest Sympathetic Fight or Flight 16 You walk outside and see a cheetah chasing after you to eat you Explain which branch of the autonomic nervous system will increase in activity as a result What will it do through your adrenal gland and how will this help you run from the cheetah 8 pts Name The sympathetic nervous sytem will increase its activity and signal the adrenal gland to release epinephrine into the blood stream This has multiple effects on the body but one of the effects is it causes the constriction of blood vessels increasing blood pressure This helps you run from the cheetah by helping blood reached all the tissues of the body with oxygen as their demand increases through the increase in blood pressure 17 Briefly describe each of the following steps of the excitation contraction coupling that leads to muscle contraction 18 pts 1 Action potentials traveling down the axon cause opening of calcium channels and the release of Ach which then binds to receptors on the end plate which triggers and action potential in the muscle cell 2 The action potential propagates along the sarcolemma and down the T tubules 3 The action potential is detected by DHP receptors which causes calcium channels associated with ryodine receptors to open and release Ca2 from SR 4 Ca2 binds to troponin exposing myosin binding sites 5 Crossbridge cycle can begin so that myosin binds to actin completes the power stroke through the energy provided by ATP 6 Ca2 concentration is decreased as it is transported into the SR and the muscle fiber then relaxes 18 Do all motor neurons have a similar number of muscle fibers they are connected with Why is this important 4 pts Name No this is important because by having motor neurons with varying numbers of associated muscle fibers and strength of those fibers within a given muscle muscular tension can be varied over a wide range merely by varying the number of active motor units of differing sizes 19 You are a researcher studying the genetic basis for different muscle related disorders You discover a mutated gene in one individual which codes for a myosin protein which hydrolyzes ATP at a slower rate than the normal myosin protein What effect might this have on muscle contraction and why 4 pts You would expect muscle contraction on average to be slower This is because the rate limiting step of muscle contraction is in the hydrolysis of ATP during the crossbridge cycle by myosin If its ability to hydrolyze ATP is slower fewer crossbridge cycles can be completed in time making muscle contraction slower 20 Which muscle fibers fatigue