Exam 1 Flashcards
What comprises the PNS?
Spinal (sensory and motor) nerves
Sensory ganglia
Schwann cells
Autonomic nervous system
Sympathetic
Parasympathetic
EntericWhat are the cell types in the CNS?
Nerve cells (neurons)
Supporting cells (glia)
Astrocytes, oligodendrocytes, microglia
Capillaries
Ependymal cellsWhat makes up a neuron?
A nerve cell has one or more dendrites, a cell body (soma), at most, one axon
How are microtubules organized in the cell body and dendtites of the neuron?
In both of these structures the microtubules are organized any which way they like.
How are microtubules organized in the axon?
All in the same direction. The negative side is towards the cell body and the positive side is towards the end terminal of the axon.
What is one reason for the structural/functional polarization of neurons as a whole?
The unified polarization of microtubules within the axon.
What are the three subtypes of neurons by structure?
Multipolar neuron- dendrites on cell body and one axon coming off. (most abundant)
Bipolar neuron- Cell body in middle with processes protruding out on either side. One end is the receiving end and the other end is the signalling or information transfer end. These are found in the retina and the 8th cranial nerve (auditory vestibular).
Unipolar neurons- Cell body looks like a flower sticking up from the ground. These are found in the sensory ganglia.
What are the output cells of the cerebral cortex?
Pyramidal cells.
How can you break down neurons based on branching shape?
ie. pyramidal and stellate
How can you break down neurons based on axon size?
Long axon projection neurons
to other neurons
to effectors (muscles, glands)
Short axon interneurons (aka local circuit neurons)
Amacrine cellsWhere are amacrine cells primarily located?
The retina. They have no axon.
What is an LCN?
A local circuit neuron or short axon neuron.
What is the end of an axon called?
The telodendron. At the end of each terminal branch in this telodendronic region, there is a button called the terminal bouton.
What is contained within the terminal boutons?
2 main things= mitochondria and synaptic vessicles containing neurotransmitters.
What are the 3 basic ingredients in a synapse?
Axon terminal (presynaptic), gap in between called the synaptic cleft, and receiving portion of dendrite (PSD)
What distinguishes motor neurons histologically?
They stain nice with a silver stain but are most known for their clumps of nissle bodies (rough ER)
What neurons are vulnerable to the polio virus?
Motor neurons in the spinal cord
What are lower motor neurons?
Motor neurons in the spinal cord. As opposed to motor neurons further up in the nervous system that are the commanders of these.
How does Parkinson’s manifest on a histological slide?
Neuromelanin is a biproduct of dopaminergic signaling and appears black on the section. A healthy brain will show black in the substantia nigra while this coloring will diminish or disappear in a Parkinson’s patient’s section.
How does Huntington’s manifest on a histological slide?
Huntington’s is characterized by a regional degeneration and subsequent expanding of the nearby ventricles.
How does Alzheimer’s manifest on a histological slide?
Marked hippocampal degredation initially and utlimately global degredation. (am beta plaques and phos tau tangles)
What are the 3 types of cell death?
Apoptosis, necrosis, autophagy
What do astrocytes do?
They provide structural and metabolic support, contribute to the blood-brain barrier, form CNS scars, provide scaffolding for neuronal migration and axon guidance, may participate in signal processing and memory encoding
What do oligodendrocytes do?
They form CNS myelin
What do microglia do?
They’re the macrophages of the CNS
What is one key function of astrocytes?
The BBB
How do astrocytes contribute to the BBB?
Astrocytic endfeet make a wall around the outer wall of the capillary. Endfeet are the outermost covering of the BBB.
What is the point of the Nodes of Ranvier?
Electrical conduction jumps from node to node vastly speeding up conduction down the axon. Sultatory conduction. The electrical signal doesn’t have to change the membrane potential at every point, only the nodes of ranvier.
What myelinates PNS cells?
Schwann cells.
How does schwann cell myelination differ from regular?
Schwann cell throws its whole body into it. It then extrudes the cytoplasm.
What is one place shwannomas are very common?
The point of entry of the 8th cranial nerve into the brainstem.
Where are action potentials initiated?
The spike initiation zone is usually located near the axon hillock, where the axon emerges from the cell body.
What are granule cells?
Granule cells are smaller, and are often star-shaped (stellate) because the dendritic tree radiates out in all directions from the soma. Granule cells provide much of the local (regional) information processing.
What are pyramidal cells?
Pyramidal cells vary in size, but have a stereotypical shape: a pear-shaped soma, several dendrites (called basal dendrites) emerging from the base of the soma, a large and highly branched dendrite emerging from the apex of the soma (called the apical dendrite), and an axon that issues from the base of the cell body. The dendrites of most pyramidal cells have structural embellishments called dendritic spines
What’s another name for long axon neurons?
Projection cells
Many interneurons are?
Inhibitory
Describe the neuromuscular junction.
Motor neurons innervate skeletal muscles at neuromuscular junctions, which are a specialized version of a synapse. These contacts form a motor end plate consisting of an enlarged axon terminal containing synaptic vesicles, junctional folds, an enlarged synaptic cleft, and the muscle sole plate.
What are the two types of activated microglia?
Activated microglia exist in two forms: non-phagocytic microglia are immediately responsive to CNS inflammation, while activated phagocytic microglia comprise the most immune-responsive form of the cell.
How do axtivated phagocytotic microglia work?
Activated phagocytic microglia phagocytose apoptotic neurons during CNS development, and respond to trauma and toxic lesions/material in the adult CNS. To do so, the activated phagocytic microglia migrate to the site of injury, phagocytose the foreign material, and secrete pro-inflammatory factors that promote proliferation of additional microglia. As a part of this response, the activated phagocytic microglia can activate astrocytes and impact capillary endothelial cells, aiding the response to infection. However, prolonged microglial activation can directly or indirectly damage neurons through the chronic release of soluble factors associated with the inflammatory response. This is thought to occur in many neurodegenerative disorders such as Alzheimer’s disease and Parkinson’s disease, as well as viral (HIV, HSV), bacterial (Streptococcus pneumoniae) and parasitic (Plasmodium falciparum) infections.
What do astrocytes do?
Astrocytes provide structural and metabolic support for neurons, participate in the regulation of ions and molecules in the extracellular fluid, contribute to the blood-brain barrier, form CNS scars, provide scaffolding for neuronal migration and axon guidance during development, and may participate in signal processing and memory encoding. There are two subtypes: fibrous (found in white matter) and protoplasmic (found in gray matter)
Why is white matter white?
Because myelin has a very high lipid content, myelinated axons appear white. For this reason, myelinated fiber tracts are called white matter, in contradistinction to CNS regions with high concentrations of cell bodies, which are called gray matter.
What is a neurotransmitter?
In classic terms, neurotransmitters are small molecules that are synthesized within neurons, packaged into synaptic vesicles, and released by nerve terminals into the synapse in response to nerve impulses (or action potentials) invading the terminals. In reality, the distinction between such classic neurotransmitters and many other types of chemical signals is arbitrary, as will be seen.
What are the 7 steps in chemical synaptic transmission?
- Nerve impulse (action potential) invades presynaptic nerve terminal.
- Activation of Ca2+ channels and entry of Ca2+ into nerve terminal.
- Ca2+ triggers neurotransmitter release via exocytosis.
- Released neurotransmitter activates pre- and postsynaptic receptors.
- Receptor activation regulates ion channels to yield postsynaptic currents.
- Released neurotransmitter is removed from synapse.
- Vesicles involved in exocytosis are recaptured by endocytosis.
What role do astrocytes play in synaptic transmission?
Glial cells, in particular, astrocytes, play crucial roles in synaptic transmission. For example, most classic (glutamtergic) synapses are surrounded by astrocytes, which buffer extracellular levels of glutamate and thereby protect neurons from excessive excitation which can kill neurons through excitotoxicity.
What are the basic steps of exocytosis?
A neurotransmitter is packaged into synaptic vesicles via a vesicular transport protein present on the vesicle membrane. Vesicles are poised for release (docking and priming) by binding to the active zone on the nerve terminal plasma membrane. Ca2+ entry then triggers fusion, which allows neurotransmitter release. The vesicle is then recaptured via endocytosis, which is dependent on the protein clathrin.
What are the amino acid nts?
Glutamate
GABA (γ-aminobutyric acid)
Glycine
What are the monoamine nts?
Catecholamines Dopamine Norepinephrine (also known as noradrenaline) Epinephrine (also known as adrenaline) Indoleamines Serotonin Melatonin (in pineal gland only) Acetylcholine Histamine
What are some species that exert nt like properties but are not necessarily considered to be nts?
Nucleosides Adenosine
ATP
Many others (di-, trinucleosides, etc.)
Lipid-derived Anandamine, 2AG (2-arachidonoylglycerol)
Gases Nitric oxide (NO)
Neurotrophic factors Neurotrophins (e.g., BNDF [brain-derived neurotrophic factor])
Many other growth factors and cytokines
Hormones with Steroid hormones nuclear receptors Glucocorticoids Gonadal steroids Retinoic acids Thyroid hormone Vitamin D
Which nts activate ligand-gated channels that pass Na+ and what does this lead to?
Glutamate, acetylcholine, serotonin, and nucleosides. These lead to excitatory postsynaptic currents.
Which nts activate ligand-gated channels that pass Cl- and what does this lead to?
GABA and glycine. This leads to inhibitory postsynaptic currents.
What determines whether a channel passes anions or cations?
The charges of amino acids that face the pore determine whether the channel passes cations or anions.
What are the two main modes of neurotransmission?
Ligand-gated channels (“ionotropic receptors”) and G protein-coupled receptors or GPCRs (“metabotropic receptors”)
What are the differences in the transmembrane domains of ligand gated versus GPCRs?
Ligand-gated channels have 4 transmembrane domains while GPCRs have 7. G proteins interact with the GPCR’s C-terminus and 3rd cytoplasmic domain.
How do neurotrophic factors work?
Virtually all neurotrophic factors act by binding to plasma membrane receptors which lead, directly or indirectly, to the activation of protein tyrosine kinases (which phosphorylate substrate proteins on tyrosine residues only). In some cases, the neurotrophic factor receptors contain tyrosine kinase activities: the receptors are in essence ligand-activated tyrosine kinases.
How do steroid hormones and related signals work?
Steroid hormones and related signals diffuse passively into a neuron’s cytoplasm where they bind to cytoplasmic receptors (referred to nuclear hormone receptors). The binding triggers the transport of the receptor into the nucleus where the protein functions as a transcription factor. This can lead to the same types of long-lasting plasticity induced by classic neurotransmitters as noted above.
What is the resting membrane potential driven by?
K+ Channels.
