Sensation Exam 1Part 1: Neurons and Neurophysiology-What are the parts of a neuron? Could you label those parts of a neurons? Could you draw & label a neuron.-There are two kind of brain cells: neurons and glia.-Neurons are postmitotic-Be able to draw-What is a synapse? Terms: presynaptic, postsynaptic, synaptic gap (ie synaptic cleft)-Neurons forms synapses with each other where a neurotransmitter is relayed from one neuron to another.-The postsynaptic region is the side containing the soma and the dendrites-The presynaptic cell is at the end of the axon.-Where the postsynaptic and presynaptic part of the neuron meet they form a synaptic gap.-What are the 3 main types of neurons (think __polar)?-Most neurons are multipolar (many dendrites and almost always an axon)-Bipolar: 2 processes off of soma –soma just keeps neuron alive. Bipolar neurons are typically found in the sensory system.-Unipolar: 1 process off of soma. Are mainly in the skin to detect stimulus like touch, pain, and temperature.-How can you connect neurons? What would be the functional significance of such connections?-You can have a 1:1 ratio, which is never the case when discussing neurons.- Many:1 ratio.- 1:many ratio, which are important in aspects of arousal.-BTW, what are glial cells?- Form the myelin on the axon, which speeds up the energy potential of action potentials down an axon.-What is the difference between an inhibitory neuron and an excitatory neuron?-Excitatory-When the neurotransmitter excites the postsynaptic region (side with soma and dendrites.)-Inhibitory-When a neurotransmitter inhibits the postsynaptic region.-What is a neurotransmitter?-They are contained at the terminal end of the axon and is for chemical transmission between neurons.-Can either excite or inhibit the receiving neuron.-Where does the action potential occur? -An action potential travels down the axon of the neuron causing the release of the neurotransmitter into the synaptic cleft. The action potential is simply the movement of ions into and out of the axon-What ions are involved?-There is a lot of Na, Cl outside of the cell, with just a little bit inside.-And there is a lot of K inside the cell & just a little outside.-Understand the terms Polarization, Depolarization, Hyperpolarization-Depolarization-Is when the neuron becomes less negative.-Depolarization=excitatory! -Hyperpolarization is when the neuron becomes more negative. An example would be Cl- entering the cell-What forces act on the ions?-Concentration gradient-Ions flow from an area of high concentration to low concentration.-Electrical gradient- Ions flow to areas of opposite charges.-What is a voltage-gated channel? -This is the channel where ions flow in the membrane of the axon. -Starting w/ threshold being reached at the axon hillock, what happens during an action potential?-When a threshold of -50mV is reached at the axon hillock(control center) voltage-gated sodium channels open up à sodium rushes into cell à cell becomes depolarized.-Then voltage gated potassium channels open up & voltage-gated sodium channels close à potassium rushes out of cell à cell becomes hyperpolarized.-Voltage-gated potassium channels close…that part of the membrane is back to -70 mV.-Think about the size and rate of action potentials. Which one can vary, and which is constant?-Action potentials have an “all or nothing policy” -Meaning its size remains undiminished as it travels down the axon.-The size of each action potential is always constant.-What is the role of calcium?-When an action potential is reached at the axon terminal, it opens voltage gated calcium channels. When calcium enters the terminal it allows the synaptic vesicles full of neurotransmitters to bind to the terminal membrane and release these NT into the synaptic cleft, relaying the message to other neurons.-What is the function of myelin? What are nodes of Ranvier, and what do they have that myelinated segments of the axon do not have?-Myelin increases the speed and energy efficiency of the action potential down the axon. -Node of ranvier- Is the unmyelinated segment of axon between the myelinated segments.-What is an IPSP? EPSP? What is the big difference b/t an action potential and an EPSP?-EPSP (excitatory post synaptic potential)- Is a depolarization in the postsynaptic cell caused by the flow of positively charged ions into the post synaptic cell. They increase the probability that a postsynaptic action potential will result because of the depolarization in the cell.-IPSP (inhibitory post synaptic potential)- results from the flow of negative charged ions into the cell.-What determines if threshold is reached at the axon hillock?-If a threshold of -50mV is reached it will cause an action potential to occur.-Also synaptic activity on the dendrites and soma on the neuron.-What is the difference between voltage-gated channels and ligand-gated channels (both in terms of their location and how they open)?-Ligand-gated channels are receptor channels. So during synaptic potential they open.-Voltage gated channels open during an action potential in response to a change in membrane potential.-What are the 2 types of ligand-gated receptors? How do they differ from one another? -A receptor is a protein in the membrane that a neurotransmitter binds to.-2 kinds: Ionotropic & Metabotropic.-Ionotropic receptors - are also called channels. Here a NT binds to the protein, and the channel will open allowing the ion to pass through.-Metabotropic receptors do not have channels. Neurotransmitter binds à things (G-protein) are activated on the receptor inside the cell à ‘ second messenger’ is used to open ion channels an/or do other things inside the cellPart 2-What are the components of the CNS? What are the components of the PNS? What are the divisions of the PNS?-The central nervous system consists of the brain and spinal chord.-The PNS=Autonomic NS+ Somatic NS-Automatic controls heart rate, sugar levels, ect.-Somatic-processes nerves from sense organs to the CNS and from CNS to other muscles and glands.-The autonomic NS is divided further into the Sympathetic& parasympathetic NS.-Sympathetic-fight or flight. Ex: running away from a tiger.-Parasympathetic- is for nonemergency responses. Ex: salvation.-What aspects of the brain differ between species? What is highly evolved in humans?-Humans have larger cortex. So we are more conscious and able to filter more complex information.-What are the
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