Zoology101: Animal Biology Exam #3 Study Guide Lectures 23-32Lecture 23 (October 24) How does the nervous system change as the animal becomes more complex?As the animal's complexity increase, so does the nervous system. For example, Cnidarians are very simple creatures, requiring an underdeveloped nervous system such as a nerve net. Humans on the other hand have 2 types of nervous systems and cephalization. Name the structures of a neuron and describe them.The dendrites are the finger-like projections at the top of the neuron that receive the signal; the cell body maintains the shape; The axon hillock is the point of summation in a cell in which the signal is generated; the axon sends the signal down to the terminal branches via the myelin sheath; the synaptic terminal sends the signal to the other cell.List the three types of glial cells, where they can be found, and what their function is.Schwann cells myelinate the axon to increase signal speed; these are found in the peripheral nervous system. Oligodendrites also myelinate the axon to increase signal speed, but are found in the central nervous system. Astrocytes are used in metabolic support and the blood-brain barrier; these are found in the central nervous system. If you wanted to increase signaling speed, what would you want to do to the axon?In order to increase speed of the signal, you would want to increase the axon diameter and the amount of myelin sheath. The nervous system has two components: the central nervous system and the peripheral nervous system. What comprises both systems?In the CNS, the brain and spinal cord make up the entire system. In the PNS, there are two subsections of nerves, afferent and efferent. Afferent neurons are the sensory system, taking in external cues, and the efferent nervous system is the motor system, signaling skeletal contractions, and the autonomic system, signaling involuntary muscles and smooth muscles. Explain the sympathetic and parasympathetic response.The sympathetic response regulates fight or flight, arousal and energy generation, secrets epinephrine, inhibits digestion, and increases heart rate. The parasympathetic system tries to bring the body back into order by decreasing the heart rate, promoting digestion, and promoting a calming effect over the body. Describe the length of neurons.Sensory and motor neurons need to be long and have fewer connections while interneurons are short but have several connections. What is membrane potential? Describe 'resting' potential of a neruon. Membrane potential is the electrical difference (voltage) across a plasma membrane; -70mV. In resting potential a neuron isn't transmitting a signal. The outside of the cell has a high sodium and chlorideion concentration and the inside of the cell has a high potassium and anion concentration. Potassium and sodium ion channels are responsible for resting potential of a neuron. What does active transport do?Active transport helps maintains resting potential. The ion channels are closed at rest. What is hyperpolarization? Depolarization?Hyperpolarization is when the cell becomes more negative on the inside relative to the outside. Depolarization of a cell occurs when sodium enters, making the cell more positive on the inside relative to the outside. Explain the process of action potential.First, the cell is at resting state in which the gated channels are closed. Second, depolarizing occurs in which a stimulus opens some of the sodium channels and the sodium ions move into the cell. Third, the rising phase, most of the sodium ion channels are open and the inside of the cell is the most positive. Fourth, falling phase, sodium ion gates close and potassium ion channels open, allowing potassium ions to rush out and make the cell the most negative. Fifth, undershoot, sodium gates are still closed and a few potassium channels are open, which will lead to hyperpolarization. Lecture 24 (October 24)Name some of the toxins and their effects.Tetrodotoxin, used by pufferfish, blocks sodium channels which leads to paralysis. Alpha-beta toxins, used by scorpions, shift the opening and closing of sodium channels, leading to scrambled signals of neurons. Apamin, used by bees, blocks potassium channels, leading to prolonged action potential. How does the conduction of action potentials flow? Why?Conduction of action potentials move in one direction, from dendrites to terminal branches, due to the region behind the action potential hyperpolarization and cannot respond (refractory period). The depolarization of one region of axon stimulates depolarization of the next region. What are synapses? What are the two types? What is involved in the chemical synapse? Synapses are the junctions where two neurons meet up between synaptic terminal and another cell. Two types are electrical (faster, direct signaling, not common) and chemical (slower, signaling via chemicals, most common). Both these lead to a change in polarization in post synaptic cell. Vesicles and neurotransmitters are highly involved in chemical synapse. What are the components of chemical synapse/what occurs?First, action potential arrives, depolarizing presynaptic membrane and opening calcium ion channels. Next, calcium ions move into the presynaptic neuron. Then, vesicles fuse to the presynaptic membrane, creating exocytosis to the synaptic cleft. After, the neurotransmitters bind to receptors in the post synaptic membrane. Finally, the binding triggers the opening of ion channels. Describe the two types of receptors that neurotransmitters bind to.Metabotropic receptors activate a signal transduction pathway and are slower, longer lasting. Ionotropic receptors (ligand-gated ion channels) move ions quicker and is short lasting. What is the difference between ESPs and ISPs?ESPs is the depolarization or when the cell becomes less polarized and ISPs is the hyperpolarization or when the cell becomes more polarized Lecture 25 (October 29)What is the brainstem responsible for? The brain stem contains the midbrain, pons, and medulla oblongata. This system is evolutionary conserved in which it is the same across species due to similar functions of heart beat, breathing, digestion, and sleep. What does the reticular formation do?The reticular formation controls arousal and sleep by filtering sensory information. This is responsible for input from touch, pain, temperature, and sound. Why is sleep essential?Sleep is an active process. Maintenance, repair, and
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