cellular neuroscience Flashcards

Question

what is axoplasmic transport

Answer 1

axons exhibit Wallerian degeneration when cut as they cannot survive separate from their cell body this is because the normal flow of materials from the soma to axon terminal - axoplasmic transport - is interupted. directly demonstrated by Weiss and colleagues (1940s). They found that if they tied a thread around an axon, material accumulated on the side of the axon closest to the soma. When the knot was untied, the accumulated material continued down the axon at a rate of 1-10mm per day. Too slow to account for all the transport The movement of protein molecules down the axon was tracked in the late 1960s by injecting the somata of neurons with radioactive amino acids which were then assembled into proteins. The arrival of radioactive proteins in the axon terminal were measured to calculate the rate of transport. Grafstein discovered that this fast axoplasmic transport occurs at a rate up to 1000mm per day Material is enclosed in vesicles which ‘walk down’ the microtubules of the axon on connections made up of the protein kinesin in a process fuelled by ATP Anterograde transport: material moved from the soma to the terminal Retrograde transport: material moved from the terminal to the soma - believed to provide signals to the soma about changes in the metabolic needs of the axon terminal facilitated by the protein dynein Can be exploited to trace connections in the brain.

Answer 2

branches from a single neuron that are covered with thousands of synapses the postsynaptic dendritic membrane has many specialised receptors that detect neurotransmitters in the synaptic cleft

Answer 3

they cover dendrites and are believed to isolate various chemical reactions triggered by some types of synaptic activation sensitive to type and amount of synaptic activity Steward discovered that polyribosomes can be observed in dendrites often under spines. T his suggests that synaptic transmission can direct local protein synthesis in some neurons - crucial for information storage.

Answer 4

number of axons and dendrites that extend from the soma unipolar, bipolar, mutlipolar (most cells) Dendrites - dendritic tree or presence of spines connections - sensory/motor/interneurons axon length - Golgi Type I neurons/ projection neurons: neurons that have long axons which extend from one part of the brain to the other. Golgi Type II neurons/ local circuit neurons: short axons that do not extend beyond the vicinity of the cell body. neurotransmitter - cholinergic

Answer 5

``` support neuronal functions critical roles in development and pathogenesis ependymal cells astrocytes satellite cells oligodendrocytes schwaan cells microglia ```

Answer 6

Line ventricles and central canal of spinal cord Cilia - direct movement of cerebral spinal fluid keeping it moving to deliver metabolised ions and removes waste products involved in directing cell migration during brain development Disturbances in flow of this fluid leads to hydroencephaly (Ventricle system linked to lymphatic system (which only operates when asleep) - help to clear amyloid toxins seen in Alzheimer’s)

Answer 7

CNS - astrocytes PNS - satellite cells Regulate the external chemical and physical environment of neurons Ionic homeostasis - Envelop synaptic junctions in the brain, restricting the spread of neurotransmitter molecules that have been released. Astrocytic membranes possess neurotransmitter receptors that can trigger electrical and biochemical events inside the glial cell. Tightly control the extracellular concentration of several substances that have the potential to interfere with pepper neuronal function Have many special proteins in their membranes that actively remove many neurotransmitters from the synaptic cleft. Neurovascular coupling Maintaining synaptic function - regulate what happens to neurotransmitters

Answer 8

myelinated glia Generate and maintain the myelin sheath surrounding axons Important for high speed conduction of action potentials The sheath is interrupted periodically leaving regions called nodes of Ranvier exposed. Myelin serves to speed the propagation of nerve impulses down the axon Oligodendroglia are found only in the CNS and will contribute myelin to several axons Schwann cells are found only in the PNS and only myelinates a single axon.

Answer 9

function as phagocytes to remove debris left by dead or degenerating neurons and glia Immune effector cells of the nervous system Largely inactive under physiological conditions Most pathogens can’t penetrate blood-brain barrier

cellular neuroscience Flashcards

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