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 rec...
psych 115 midterm 1 ucla exam questions and answer
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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?
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