DO NOW: ANSWER ON PG 73 1. Name 1 neurotransmitter that we have learned about. 2. Draw a basic graph of a neuron action potential. Label resting potential, threshold, depolarization, and repolarization
NERVE PATHWAYS How and where impulses travel. Nerve pathways must cross the synaptic cleft Auditory Nerve Pathway
SYNAPSE The junction between any 2 communicating neurons. The neurons at a synapse are not in direct physical contact, but are separated by a gap called a synaptic cleft
NEUROTRANSMITTERS A chemical substance that is released at the end of a nerve fiver by the arrival of a nerve impulse and, by diffusing across the synapse or junction, causing the transfer of the impulse to another nerve fiber, muscle fiber or some other structure.
RESTING POTENTIAL The potential difference between the region inside the membrane and the region outside the membrane
THRESHOLD POTENTIAL If neurons are depolarized sufficiently, the membrane potential reaches a level called the threshold potential, wich is approx. -55 millivolts
ACTION POTENTIAL When threshold is reached, an action potential results, which is the basis for the nerve impulse
EXCITATORY Neurotransmitters that increase postsynaptic membrane permeability to sodium ions and bring the postsynaptic membrane closer to threshold and possibly trigger nerve impulses
INHIBITORY Neurotransmitters that make it less likely that threshold will be reached
NEURONAL POOLS In the CNS, groups of neurons that make hundreds of synaptic connections with each other and work together to perform a common function
FACILITATION A state where the net effect is excitatory but subthreshold, and an impulse is not triggered, but the neuron is more excitable to incoming stimulation than before
CONVERGENCE When axons originating from different parts of the nervous system and leading to the same neuron make it possible for impulses to have an additive effect on the neuron
DIVERGENCE When impulses leaving a neuron of a neuronal pool pass into several other output neurons; can amplify an impulse
YOUR BRAIN ON DRUGS: MARIJUANA HTTPS://WWW.YOUTUBE.COM/WATCH?V=OEF6 RFN9ORG 1. What are the most common substances humans use to alter their state of mind? 2. How long does it take for neurons to communicate? 3. How do marijuana molecules differ from alcohol molecules in our brain? 4. Name 1 effect marijuana has on your brain.
YOUR BRAIN ON DRUGS: ALCOHOL HTTPS://WWW.YOUTUBE.COM/WATCH?V=VKPZ 7XFTWJO 1. What does alcohol do quickly and well? 2. neurons use glutamate and neurons use GABA 3. Name 1 less thing your body does when introduced to alcohol. 4. Alcohol makes you think clearly about almost
BOOKWORK 20 MINUTES TO COMPLETE (Pg 73 in Journals) Pg 225 # 17-19 Pg 226 # 20-22 Pg 227 # 23-24
1. What are the 2 major types of cells that form nervous tissue? Neurons and neuroglial cells 2. What are the 2 major subdivisions of the nervous system? CNS and PNS 3. How do sensory receptors collect information? Detect changes inside and outside the body; monitor external environmental factors, such as light and sound intensities, and conditions of the body s internal environment, such as temperature an oxygen level 4. How does the CNS integrate incoming information? Sensory receptors convert environmental info into nerve impulses, which are then transmitted over peripheral nerves to the CNS. There, the signals are integrated creating sensations, adding to memory, or helping produce thoughts that translate sensations into perceptions.
5. What are the 2 types of motor functions of the nervous system? somatic nervous system (controls skeletal muscle) Autonomic nervous system (controls involuntary effectors) 6. List the functions of the cells that support neurons. provide structural framework, produce the components of the electrical insulator myelin, and carry on phagocytosis. 7. Distinguish among the types of neuroglial cells in the central nervous system. Microglial, Oligodendrocytes, Astrocytes, Ependymal Cells 8. What is the function of Schwann cells in the peripheral nervous system? Form a myelin sheath around axons
9. Distinguish between a dendrite and an axon. Dendrite: cytoplasm-filled, conduct nerve impulses to the neuron cell body Axon: conducts impulses away 10. Describe the components of a neuron cell body: cytoplasm, cell membrane, organelles dendrites: short and highly branched axon: single structure, may give off side branches 11. Describe how a myelin sheath forms. produced by Schwann cells, wind tightly around axons, many layers of cell membrane, little to no cytoplasm 12. Explain why axons of peripheral nerves can regenerate, but axons of the CNS nerves cannot. PNS nerves contain a neurilemmal which make regeneration possible.
13. Name 3 groups of neurons based on structure and 3 groups based on function Structure: Multipolar, bipolar, unipolar Function: Sensory, Interneurons, motor neurons 14. Describe the events that occur at the synapse. Nerve impulses cross the synaptic cleft between neurons; the synapse is between an axon and dendrite or axon and cell body. Sender = presynaptic neuron receiver = postsynaptic neuron. Synaptic transmission is a one-way process carried out by neurotransmitters. Neurotransmitters diffuse across the synaptic cleft and react with specific receptors on the postsynaptic neuron membrane. 15. Summarize how a nerve fiber becomes polarized. More sodium ions outside the membrane and more potassium ions inside 16. List the major events of an action potential. a) at rest, the membrane potential is negative b) When the membrane reaches threshold, sodium channels open, some sodium diffuses in, and the membrane is depolarized c) soon afterward, potassium channels open, potassium diffuses out, and the membrane is repolarized
17. What is the relationship between action potentials and nerve impulses? A wave of action potentials along nerve axons constitute the nerve impulse 18. Explain how impulse conduction differs in myelinated and unmyelinated nerve fibers. Myelin insulates and prevents almost all ion flow through the membrane it encloses. A nerve impulse traveling along a myelinated axon appears to jump from node to node; many times faster than an unmyelinated axon. 19. Define all-or-none response as it relates to nerve impulse conduction. If a neuron responds at all, it responds completely. A greater intensity of stimulation does not produce a stronger impulse, but rather, more impulses per second. 20. Distinguish between the actions of excitatory and inhibitory neurotransmitters Excitatory neurons increase postsynaptic membrane permeability to sodium ions, bringing the membrane closer to threshold. Inhibitory neurons make it less likely that threshold will be reached.
21. What types of chemicals function as neurotransmitters acetylcholines, monoamines, amino acids, and neuropeptides 22. What are possible fates of neurotransmitters? decomposed by enzymes, transported back into the synaptic knob that released them or into nearby neurons or neuroglial cells 23. Define neuronal pool. Groups of neurons in the CNS that make hundreds of synaptic connections with each other and work together to perform a common function 24. Distinguish between convergence and divergence. convergence: axons originating from different parts of the nervous system and leading to the same neuron. Create an additive effect on a neuron divergence: neurons of a neuronal pool that pass into several other output neurons. Amplifies an impulse