psych 115 midterm 1 UCLA Exam Questions and Answers 100% Pass

psych 115 midterm 1 UCLA Exam Questions and Answers 100% Pass What is the role of Dorsal root ganglion cells? • DRG = unipolar neurons in peripheral nervous system • Job is to relay somatosensory info from skin to spinal cord Describe a touch stimulus. • Touch to skin generates a receptor potential by opening mechanoreceptor Na channels • Receptor potential passively propagates (flows) to the integration zone • Receptor potential is attenuated (becomes smaller) as it propagates due to cytoplasm being a resistive electrical conductive • If the receptor potential depolarizes the axon hillock's membrane from its resting potential of -75mV up to spike threshold ( ~ -55mV)then action potential occurs • Na+ voltage-gated channels will allow sodium to enter and depolarize membrane (this happens again, called positive feedback cycle) What are the three states of an active Na+ channel? • Closed - Na+ ions cannot pass through pore • Open - Na+ ions can pass freely through pore • Inactive - Na+ cannot pass through pore and channel cannot be opened, even if membrane is depolarized above spike threshold What are three types of action potential conduction? • Passive - axon without active channel propogates the spike very fast, but not far • Active - unmyelinated axon with active channels propogates very far, but not fast • Saltatory - myelinated axon with active nodes propogates the spike very fast and very far How are neurons classified? List the three principal types. • "how many things" sticking out of a soma/ how many branches • Multipolar • Bipolar • Unipolar What are the differences between white and gray matter? Cortical regions that contain lots of myelin are called white matter. Cortical regions that contain little myelin are called gray matter. What is myelin sheath made from? glial cells. Schwann cells in PNS Oligodendrocytes in CNS When does an AP propagation stop? The action potential propagates until it reaches the DRG neuron's axon terminals in the spinal cord... What happens when the presynaptic cell fires a spike? vesicles fuse with the cell membrane to release their contents into the synaptic cleft (thin space between the presynaptic cell and postsynaptic cell). What is the the neurotransmitter release cycle? 1) Neurotransmitter molecules are manufactured by the neuron 2) The neurotransmitter molecules are pumped into the vesicles through vesicular transporters 3) The filled vesicle moves toward the cell membrane and waits for an action potential to come along 4) When the action potential occurs, calcium enters synaptic bouton and causes the vesicle to fuse with the cell membrane and dump its contents into the synapse 5) A "clathrin coat" forms on the inner surface of the membrane and pinches a new empty vesicle from the cell membrane 6) The new vesicle sheds its coat and starts filling up with transmitter to start the cycle over again What are Ionotropic Receptors? Ionotropic receptors are ligand-gated channels They form cation (Na+, K+, Ca++) or anion (Cl-) channels. Neurotransmitter binding to a specific location on the channel results in opening of the channel. What are Metabotropic G-protein coupled Receptors? What are the three subunits of a G-protein complex? What does alpha do? The G-protein complex is an assembly of three subunits: alpha (a), beta (b), and gamma (g) The alpha (a) subunit of the G-protein floats through the cytoplasm and attaches to the intracellular domain of an ion channel to open or close it (this is still a ligand-gated ion channel, but the ligand is a second messenger molecule that binds the channel inside the cell rather than outside the cell What are other things Metabotropic receptors do beside opening channels? G-proteins that unbind from the metabotropic receptor can activate intracellular second messenger pathways and trigger many other events inside the postsynaptic cell, such as: - Release of calcium from intracellular storage - Gene regulation Describe a S-R reflex. What is a feedforward circuit? Step 1: Sensory neuron fires and excites zero or more interneurons Step 2: Interneurons fire and excite one or more motoneurons Step 3: Motoneurons fire and excite muscle fibers Step 4: muscle fibers fire (yes they do!) and contract to move the body feedforward circuit (so called because information flows in a single "forward" direction): What is a neuron? • Neurons are cells that generate fast electrical impulses called action potentials • Fast signaling allows interconnected networks of neurons to rapidly sense and react to the environment What is the goal of systems neuroscience? • To identify functional systems in the brain (often by localizing them within specific anatomical regions) that perform distinct cognitive or behavioral tasks 3. Describe fMRI. Is fMRI invasive or non-invasive? • Compares levels of activity across different brain regions by using a powerful magnetic field to measure B.O.L.D. (blood oxygen level dependent) signals • Non-invasive method. 4. Know how a neuron looks like and the four major parts of a neuron: Dendrite: treelike arborizations that receive signals from neurons Soma: Cell body containing the nucleus Axon: long branched cable that sends signals to other neurons, which is sometimes surrounded by a myelin sheath Axon terminals (synaptic boutons): tips of axon branches from which neurotransmitter is released onto target cells 5. What is a synapse? How does information flow? • Chemical junction where neurons connect with each other • Info flows MOSTLY in one direction, from the presynaptic neuron to the postsynaptic neuron 6. What is circuits neuroscience? What is the goal of circuits neuroscience? • ID functionally distinct populations of cells in the brain, and discover how these cell populations are interconnected with one another to form a circuit that performs a specific computational or behavioral function 7. What is a cell population? • Functionally distinct groups of cells or cell type • Two cells belong to the same population if they are similar to another, same conversely • Can be similar via connectivity, neurotransmitters, morphology, firing properties, and/or gene expression 8. What types of cells are the nervous system composed of? • Neurons • Glial cells (or glia) How do we classify neurons based on their connectivity? • Neural populations are often classified according to their efferent connections ( where they send their axons to make synapses onto other neurons • Can also be classified by their afferent connections ( which neurons they receive their synaptic inputs from) What is a neuron that sends long-range efferents called? What is a neuron that sends short-range efferents called? • Neurons that send short-range efferents ONLY to their local neighbors are called interneurons or local circuit neurons • Neurons that send long-range efferents to distant brain areas are called projection or principal neurons 11. There are three layers of protective membrane (meninges) what are they? • Dura Mater - Thick outside layer • Arachnoid - spongy middle layer • Pia Mater - thin inner layer 12. Where is CSF manufactured and where does that organ reside? • Manufactured by an organ called choroid plexus • Resides in hollow tubes and cavities called ventricles What is a positive ion called and a negative ion called? What does it mean to be monovalent? Divalent? • Cation = positive ion • Anion = negative ion • Monovalent = single surplus of proton or electron • Divalent = two surplus of proton or electrion What is voltage? Describe how a voltage meter works and how transmembrane voltage is measured. • Voltage = difference in electrical charge between two locations • Voltage meter uses two wires, one positive and one negative to compare the charge at TWO different locations and measure the voltage between them • To measure transmembrane (VM) voltage, we must measure the INSIDE AND OUTSIDE of the cell. • VOLTAGE OF CELL = CHARGE INSIDE - CHARGE OUTSIDE Understand how to measure transmembrane voltage for different cations and anions. • Potassium is large inside the cell, everything else is small inside • Sodium and Chloride are large outside the cell, everything else is small outside • A concentration gradient will ALWAYS FLOW FROM HIGH TO LOW List and explain the three different types of gradients. • Transmembrane gradient measures diferent sides of membrane (inside vs. outside) • Chemical gradient is a difference in density of ions ( NUMBER of ions) inside versus outside of the cell • Electrical gradient is the difference in the amount of charge inside versus outside of the cell 17. What are the three types of forces that act upon ions? Explain. • Electrical Force: ions with same charges repel, while ions with opposite charges attract with each other regardless of the concentration of ions • Chemical Force: particles move from high to low(second law of thermodynamics) pushing ions along their chemical gradient regardless of charge • Driving Force: sum of electrical and chemical force. The driving force determines which way an ion "wants" to flow. The direction will be determined based on the BIGGER force 18. What is electrochemical equilibrium? Can other ions be in equilibrium while others are not? • When an ion has a driving force of zero. • 1 ion can be at equilibrium while others are not 19. What determines the direction of the electrical force? • Membrane potential (positive or negative) • Ionic Charge (cation or anion)