BIOL 1107 1st Edition Exam 5 Study Guide Lectures 29 Lecture 29 April 18 1 Compare the two coordinating systems in animals The adjustment of an animal s response to changes in the environment and the complex linking if the various processes in the body that this response involves are called co ordination These two coordinating systems in animals are the nervous and endocrine systems 2 Describe the three major functions of the nervous system Sensory Input receptors within and near the body surface respond to stimuli and send nerve impulses to the CNS Integration the CNS receives processes and interprets sensory input then decides what to do with it Motor Output the CNS sends out sends out nerve impulses to effector organs muscles and glands in response to sensory input 3 List and describe the three major parts of a neuron and explain the function of each Dendrites pick up the electrical impulses and pass them to the cell body Cell Body contains the nucleus Axon receives the impulse from the cell body and passes it on the next neuron muscle via neurotransmitters crossing the synapse gap between them Axons have fatty layers myelin sheath around them to speed up the transmission of impulses 4 Explain how neurons can be classified by function Classified into three groups Sensory sensory afferent neurons sense changes inside or outside the body by means of receptors ends or nearby receptor cells They send impulses to the CNS in response to these changes Interneurons interneurons association neurons are found in the CNS and link with other neurons and send impulses from one part of the CNS to another Motor motor efferent neurons send impulses from the CNS to muscles or glands There are two types of motor neurons that control smooth or cardiac muscle Accelerator neurons increase muscle activity while inhibitory neurons decrease muscle activity 5 Describe the function and location of each type of supporting cell supporting cells are often referred to as glial cells they regulate the chemical environment around the neurons protect neurons from foreign invaders help neurons conduct impulses stabilize the position of neurons and help repair regenerate damaged neurons 6 Explain what a resting potential is and list four factors that contribute to the maintenance of a resting potential A resting potential is the potential difference between the two sides of the membrane of a nerve cell when the cell is not conducting an impulse Factors that contribute the Na K pump keeps a higher concentration of Na on the outside compared to the K on the inside This is accomplished because the pump expels three Na ions for every two K ions it brings in Thus the cell has a less positive or more negative interior than the extracellular environment This is counter intuitive however because both ions are positive Ion leak channels allow for K to follow outward but do not allow Na ions to flow inward This again contributes to the cell being less positive on the interior than the exterior Large negative anions as seen on many cellular proteins are essentially trapped within the cell and are not excreted contributing to the cell interior s negative potential 7 Define equilibrium potential and explain why the K equilibrium potential is more negative than the resting potential The system is then in electrochemical equilibrium where one side of the membrane may still have a more negative charge than the other The potential difference is then called the equilibrium potential The k equilibrium potential is more negative than the resting potential because K moves out down its concentration gradient passively via the leaky K channel negatively charges proteins are inside the membrane is barely permeable to Na when at rest so you primarily only get K leaving The Na K pump pumps the Na that manages to get through the membrane into the cell back out So you re also getting 3 K pumped back in but 2 Na out thus you still overall have more positive ions leaving than entering through the pump 8 Define graded potential and explain how it is different from a resting potential or action potential Graded potentials are charges in membrane potential that vary in size as opposed to being all or none They arise from the summation of the individual actions of ligand gated ion channel proteins and decrease over time and space They do not typically involve voltage gated sodium and potassium channels The difference between graded potential and action potential the magnitude of the charge of the membrane potential in a graded potential is dependent upon the strength of the stimulus The larger the stimulus the greater the change in potential Graded potentials are not the nerve signals that travel along an axon but do influence their generation 9 Describe the characteristics of an action potential and explain the role membrane permeability changes and ion gates play in the generation of an action potential Ionic disequilibrium due to difference in Na and K concentrations inside and outside the cell because of the action of the Na K ATPase pump 10 Explain how the action potential is propagated along a neuron 1 When Na enters a cell as the onset of an action potential positive charges in the cell are repulsed and negative charges are attracted This results in the charge spreading away from the sodium channels 2 As positive charges are pushed farther from the initial Na channel they depolarize adjacent portions of the membrane 3 Nearby voltage gated Na channels pop open in response to depolarization Positive feedback occurs and full fledged action potential results The action potential is continuously regenerated as it moves down the axon The signal does not diminish as it moves because the response is all or none The action potential does not propagate back up the axon because Na channels are refractory once they have opened and closed they are less likely to open again for a short period of time Sodium channels downstream of the site are not in the refractor state resulting in the one way propagation of the action potential 11 Describe two ways to increase the effectiveness of nerve transmission Myelin sheath Node of Ranvier 12 Describe synaptic transmission across as electrical synapse and a chemical synapse 1 the action potential arrives at the end of the axon 2 This triggers the entry of calcium ions into the presynaptic cell 3 In response synaptic vesicles fuse with the presynaptic membrane then release neurotransmitters into the synaptic