Exam review questions Flashcards
What are myosin and actin?
ACTIN is the major THIN filament protein, and MYOSIN is the major THICK filament protein. They interact inside myofibrils and produce muscle movement.
Describe briefly the three phases of pathway formation.
1) Pathway selection: The growing axon selects which path it takes at certain points of growth.
2) Target selection: The axon selects which component/nucleus to innervate.
3) Address selection: The axon finds the correct layer of the brain where it forms the connection.
What is a trigeminal nerve?
Trigeminal nerves (cranial nerve V) supply somatic sensation of the face to the brain.
What is an oval window?
The oval window is a hole in the bone of the skull, which is covered by a membrane.
The pictures represent the operation of G-proteins.
In the picture above, GDP (guanosine diphosphate) is exchanged for GTP (guanosine triphosphate). This happens when the G-protein-coupled receptor activates the alpha-subunit of the G-protein.
In the picture below, the activated G-protein splits, and both the G-alpha (GTP) subunit and the G-beta-gamma subunit become available to activate effector proteins.
What is retrograde transport?
It is the movement of molecules of organelles in the “opposite” direction of anterograde transport: away from the synapse or plasma membrane, and towards the cell body or soma.
What is a motor unit?
A motor unit is a combination of one alpha motor neuron and all the muscle fibers it innervates.
What is the function of a synaptic vesicle?
They store different neurotransmitters in the axon terminal. The neurotransmitters are released at the synapse. They are essential for propagating nerve impulses between neurons, and are constantly being regenerated by the neuron.
Name three sources of input to alpha motor neurons.
- Input from dorsal root ganglion cells (muscle spindle)
- Input from spinal interneurons
- Input from upper motor neurons in the motor cortex
The neuronal membrane is built on a double layer of phospholipids. What property of the phospholipid molecule makes it orient so that the tails are inside the membrane and the heads are in contact with water?
Hydrophobia / hydrophilia. The phospholipids contain long non-polar chains of carbon atoms, and a polar phosphate group. The polar “head” is hydrophilic and faces the outer and inner water environments, and the non-polar “tail” is hydrophobic and face each other.
What is the corticospinal tract?
Corticospinal tract, or pyramidal tract, is the most important component of the lateral pathways. It starts from the motor cortex, decussates at the junction between medulla and spinal cord, and terminate in the dorsolateral region of the ventral horn.
What is a gap junction?
Gap junctions are where electrical synapses occur. Gap junctions occur between cells in nearly every part of the body and interconnect many non-neural cells, e.g., epithelial cells, smooth and cardiac muscle cells, liver cells, some glandular cells, and glia. In neurons, gap junctions are also called electrical synapses.
The speciality of gap junctions is that thjey directly connect the cytoplasm of two cells, which allows various molecules, ions, and electrical impulses to directly pass through a regulated gate between cells.
How does the organ of Corti work?
It contains auditory receptor neurons; hair cells, rods of Corti, and various supporting cells. When the basilar membrane moves, the stereocilia bend, which generates a receptor potential that either hyperpolarizes or depolarizes the hair cells. Hair cells send action potentials to spiral ganglion cells, which provides all auditory information sent to the brain.
What is a simple cell in the visual cortex?
They are orientation-selective LGN cells with receptive fields that are aligned along one axis. The segregation of ON and OFF regions is a defining property of simple cells, and it is because of this receptive field structure that they are orientation sensitive.
What is a neuromuscular junction?
It is a chemical synapse that occurs between the axons of motor neurons of the spinal cord, and skeletal muscle. The transmission here is fast and reliable; an action potential in the motor axon always causes an action potential in the muscle cell it innervates.
Its specialities are its size: it is one of the largest synapses in the body. It is also of significant clinical significance, as diseases, drugs and poisons that interfere with this kind of junction have direct effects on vital bodily functions.
What is the function of gamma motor neurons?
They are activated when muscles contract and shorten, and they keep the muscle spindles stretched and providing information about muscle length.
Ion concentrations inside and outside a cell are given in the following table. What is the membrane voltage (potential inside minus potential outside of cell) if K+ channels are partially open for a long time but other channels remain closed? What happens to the membrane voltage if then all Na+ channels open?
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When a photon activates rhodopsin, a G protein is activated and a chemical sequence of events follows. What is the final effect of this chain of events on sodium channels on the cone or rod membrane?
The ion channel closes and Na+ conductance is reduced.
What is an excitatory postsynaptic potential?
It is a temporary depolarization of postsynaptic membrane potential, and makes the postsynaptic neuron more likely to fire an action potential. It is caused by the flow of positively charged ions into the postsynaptic cell.
What is an inner hair cell?
Inner hair cells are auditory receptors. They are the hair cells between the modiolus and the rods of Corti. They produce most of the cochlear output.
Which retinal cells send action potentials to the brain?
Ganglion cells and certain amacrine cells
What are the main types of cells in the retina?
1) Rod & cone photoreceptor cells
2) Bipolar cells
3) Ganglion cells
What is a trophic factor?
Trophic factors are life-sustaining substances that are provided in limited quantities by the target cells. They play a key role in cell death.
What are radial glial cells?
Radial glial cells are important in neurogenesis. They are neural progenitors that give rise to all the neurons and astrocytes of the cerebral cortex, and most neurons of the CNS.
- The two types of acetylcholine receptor are nicotinic and muscarinic. In the table below, indicate what each of the five molecules (Nicotine, Atropine, Ach, Muscarine, Curare) does to nicotinic receptor and muscarinic receptor, respectively. If the molecule activates the receptor, write “+” or “activates”; if the molecule blocks the activation, write “–“ or “deactivates”. If there is no effect, write nothing.
What is a stapes?
Stapes is a component of the middle ear whose footplate pushes inward at the oval window.
What is a dermatome?
A dermatome is a single spinal segment.
What is the role of the CEREBELLUM in movement control?
The cerebellum calculates the detailed sequence of muscle contractions required for a specific movement.
What is the role of the BASAL GANGLIA in movement control?
The basal ganglia, with its direct and indirect pathways, facilitates the initiation of willed movements by inhibition and facilitation of the thalamus.
Describe the olfactory pathway from the air to the cortex by naming the correct structures in the correct order. For example: 1) a structure in the nasal cavity, 2) a structure in the brain, 3) an area of the cortex.
- Olfactory epithelium (thin sheet of cells)
- Olfactory bulb
- Olfactory Cortex (Piriform cortex/Amygdala/Entorhinal cortex/etc.)
What is a motor neuron pool?
A motor neuron pool is all the alpha motor neurons that innervate one muscle.
Describe briefly the process of plasticity at Hebbian synapses.
It is a mechanism of synaptic segregation.
Only retinal terminals that are active at the same time as their postsynaptic LGN target neuron are retained: neurons that fire together, wire together.
Synapses that can be modified in this way are called Hebb synapses, and synaptic rearrangements of this sort are called Hebbian modifications.
