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97 Cards in this Set
- Front
- Back
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Describe the structure of a neuron
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A neuron is a cell consisting of a cell body or soma with nucleus, dendrites, an axon that may or not have Schwann cells covering it (myelin sheath), and axon terminals.
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Neuron doctrine
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Santiago Ramon y Cajal said that neurons are the functional unites of the nervous system.
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What are the three main characterizations of neuron shapes?
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unipolar, bipolar, multipolar
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Describe the composition of nervous tissue
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1. Glial cells (up to 90%) of composition
2. Neurons |
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Identify four types of glial cells
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1. Oligodendrocytes
2. Microglia 3. Astrocytes 4. Ependymal cells |
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Which cells buffer K+ and neurotransmitters, as well as provide myelin for the axons in the CNS?
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Oligodendrocytes
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Which cells regulate the formation of extracellular fluid in the CNS, stimulate the formation of tight junctions between endothelial cells that comprise capillaries (forming the blood-brain barrier) and may secrete nerve growth factors?
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Astrocytes
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What cells are derived from hematopoetic stems cells and are a type of macrophage in the nervous system?
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Microglia
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Which cells line the brain & spinal cord and regulate the production of cerebral spinal fluid?
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Ependymal cells
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What are Nodes of Ranvier?
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Sections of the axon between Schwann cells, participate in saltatory conduction.
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Describe the structure of a neuron
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A neuron is a cell consisting of a cell body or soma with nucleus, dendrites, an axon that may or not have Schwann cells covering it (myelin sheath), and axon terminals.
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Neuron doctrine
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Santiago Ramon y Cajal said that neurons are the functional unites of the nervous system.
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What are the three main characterizations of neuron shapes?
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unipolar, bipolar, multipolar
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Describe the composition of nervous tissue
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1. Glial cells (up to 90%) of composition
2. Neurons |
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Identify four types of glial cells
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1. Oligodendrocytes
2. Microglia 3. Astrocytes 4. Ependymal cells |
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Which cells buffer K+ and neurotransmitters, as well as provide myelin for the axons in the CNS?
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Oligodendrocytes
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Which cells regulate the formation of extracellular fluid in the CNS, stimulate the formation of tight junctions between endothelial cells that comprise capillaries (forming the blood-brain barrier) and may secrete nerve growth factors?
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Astrocytes
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What cells are derived from hematopoetic stems cells and are a type of macrophage in the nervous system?
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Microglia
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Which cells line the brain & spinal cord and regulate the production of cerebral spinal fluid?
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Ependymal cells
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What are Nodes of Ranvier?
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Sections of the axon between Schwann cells, participate in saltatory conduction.
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What are telodendria?
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The ends (short branches) of axons and axon collaterals, slightly enlarged to form synaptic bulbs
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What are afferent neurons?
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Sensory neurons which carry impulses from peripheral sense receptors to the CNS.
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What are efferent neurons?
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Motor neurons which carry impulses from the DNS to effector organs such as muscles and organs.
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What types of cells in the CNS are most likely to become cancerous?
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glial cells
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How many types of neurotransmitters can one axon produce?
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Only one
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What is a resting membrane?
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Cell membrane of a nonconducting neuron. It is impermeable to the passive diffusion of Na+ and K+ ions, leading to a concentration of sodium ions outside (in the extracellular fluid) and potassium ions inside the cell.
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Describe resting membrane potential.
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Difference in charge inside and outside a resting neuron, with a more negative charge inside the cell (k+ concentration) and more positive charge outside the cell (Na+ concentration). Roughly -70 mV.
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What are the functional characteristics of neurons?
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1. Excitability
2. Conductivity |
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What happens during stimulation of a neuron?
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a physical, chemical or electrical event alters the membrane and briefly reduces polarization. If the stimulation is strong enough, a response will be initiated.
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What are the steps of the action potential?
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Depolarization
Reverse Polarization Repolarization |
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What is the threshold stimulus?
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A.k.a. Liminal stimulus, the minimum stimulus necessary to initiate an action
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What is the term for a stimulus that does not elicit an action potential?
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Subthreshold (subliminal) stimulus
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What happens in spinal cord injuries that slows or stops nerve impulses?
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Oligodendrocytes are destroyed by "crush" injuries which causes demyelinization of axons.
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What is a growth cone?
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Tip of a growing axon - guided by glial cell it finds its way to a specific target, where it will form the synapses.
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What's another name for Nerve Growth Factor and what are they?
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Neurotrophic factors. Proteins secreted into extracellular fluids, usually by glial cells.
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Describe neurulation.
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The embryological development of the nervous system.
1. Notochord induces ectoderm to differentiate into neural crest 2. Neuropores close and forms a sealed tube, from which the entire nervous system will develop. 3. Nerves & neuroglia develop from neuroblasts within the neural tube. |
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What is the neural tube?
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Formed from the ectoderm in a developing embryo. Induced by notochord to differenciate into a neural plate which then forms a neural tube. The brain, spinal cord and spinal nerves derive form the neural tube.
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What is the neural crest?
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Primitive nerve cells from the neural tube and overlying ectoderm - cells move from here into developing organs. Forms the autonomic nervous system (ANS).
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What are three derivations of the neural crest?
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1. Parasympathetic division (cranial-sacral region)
2. Enteric division (intestines) 3. Sympathetic division (thoraco-lumbar region) |
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What is an absolute refractory period?
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Period after an action potential in which the membrane is not yet polarized and no stimulus will produce another action potential. Sodium gated ion channel is still open or inactvated and must be repolarized before action potential can occur.
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How do local anesthetics work?
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Block sodium-gated ion channel, blocking action potential from occuring in afferent neurons.
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What is a relative refractory period?
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"After-hyperpolarization" - some sodium channels have closed and may be reactivated by a very strong simulus.
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What is the term for a neuron that transmits a signal toward a synapse?
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Presynaptic neuron
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What does a postsynaptic neuron do?
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Conduct a signal away from a synapse
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Define neurotransmitter
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substances released by one neuron into the synapse in order to initiate a chemical or electrical change into the receiving neuron
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What is a neuromodulator?
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A chemical messenger that acts on neurons to alter the response of a neuron to a neurotransmitter
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What are three steps in the release of neurotransmitters?
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1. Nerve signals arrive at terminal axon button trigger the release of a NT into the synaptic cleft. Vesicles containing the NT line the inside of the presynaptic membrane)
2. Arrival of action potential stimulates opening of calcium ion channels. Ca2+ floods cell, vesicles fuse with presynaptic membrane, contents released into synaptic cleft. 3. NT's bind to membrane receptors on postsynaptic clef, usually triggering an action potential in that neuron, which passes the signal/process on. |
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What is an excitatory post-synaptic potential?
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Induced by stimulatory signals, bringing the postsynaptic membrane close to threshold, usually by influx of sodium ions.
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What is an inhibitory post-synaptic potential?
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Induced by inhibitory signals, hyperpolarizes the post-synaptic membrane, usually by influx of Cl- ions.
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Name five common excitatory neurotransmitters.
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1. Glutamate
2. Dopamine 3. Norepinephrine 4. Epinephrine 5. Acetylcholine |
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Name four common inhibitory neurotransmitters
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1. GABA
2. Serotonin 3. Glycine 4. Endorphines 5. Enkephalins |
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What are the primary functions of the nervous system?
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Sensory function
Integrative function Motor function |
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The somatic and visceral sensory systems are part of which division?
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The afferent sensory system, which sends information to the CNS.
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Where do motor signals go (to which divisions of the nervous system)?
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To the somatic and autonomic motor divisions (part of efferent nerve system)
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What are the layers of the meninges?
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Pia-closest to the brain (thin, delicate)
Dura- outer, tough white fibrous layer. Arachnoid-middle, cobweb-like |
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Which of the meninges contains channels or sinus that collect venous blood to return it to the cardiovascular system?
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Dura mater. Includes the superior sagittal sinus.
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Which of the meninges has threadlike strands for attachment and a sub-layer that is filled with CSF and blood vessels?
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Arachnoid (and subarachnoid space)
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Which of the meninges is in direct contact with the brain?
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Pia mater.
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What is the all-or-none principle?
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A stimulus must be threshold or greater in order to induce an action potential and conduct an impulse
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What is a synapse? What are the three main parts?
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The region of communication between two neurons. Three parts include: synaptic knob, synaptic cleft, postsynaptic membrane.
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What are neuronal pools?
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Functional groups of billions of neurons in the CNS that receive information, process and integrate it, and transmit it to other destinations. Arranged in pathways or circuits.
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What is a reflex arc?
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A type of conduction pathway, the functional unit of the nervous system.
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What are the component of a reflex arc?
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Receptor, sensory neuron, integration center, motor neuron, and effector.
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What is the name for drugs that bind and inhibit a receptor?
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Antagonists
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What do agonists do?
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Bind to receptors and produce a response similar to the normal activation of the receptor.
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What is enzymatic degradation?
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The breakdown of NT's by enzymes. products diffuse into blood and eliminated by liver and kidneys.
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What is re-uptake?
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Transmitting neuron has a re-uptake pump that takes the NT back up. When it is blocked by drugs such as seratonin re-uptake inhibitors, for example), it increases the amount of serotonin present at the synapse and allows it to remain there longer, hence potentiating the effect of naturally released serotonin
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What are three major divisions of neurotransmitters?
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1. Monoamines (biogenic amines)-serotonin, histamine melatonin, catecholamines (norepinephrine, dopamine), tyramine, tyrptamine
2. Amino acids-gluatamate, GABA, aspartate, glycine 3. Peptides-endorphins, enkephalins *Gases such as carbon monxide and nitric oxide may participate in nervous system processes but are not considered NTs. |
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Which NT inhibits activity in the brainstem, spinal cord and retina?
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Glycine
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What NT is associated with learning, memory and long-term potentiation?
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Glutamate
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Describe the functions of GABA.
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Calmness, focus, relaxation.
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Insomnia, restlessness, irritability, anxiety, panic and seizures may be associated with a deficiency of what NT?
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GABA
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Which NT inhibits the release of catecholamines, stimulates GABA, down-regulates glutamate, and may be deficient in depression, anxiety, migraines, eating disorders, panic, insomnia and ADD, PMS, OCD?
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Serotonin
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What is the function of dopamine?
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Attention, focus, motivation. Associated with pleasure, reward, and motivation/drive.
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An excess of what NT may result in psychosis and schizophrenia?
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Dopamine
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An excess of what NT may result in anxiety, aggression, mania and irritability? A deficiency of this NT results in fatigue, hypersomnia and apathy.
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Norepinephrine
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What are the functions of norepinephrine?
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Mediate "fight or flight," mood, drive, learning, alertness, arousal.
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Which major NT is associated with obsessions, compulsions and memory?
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Serotonin
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What are the major classes of antidepressants?
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1. Tricyclic antidepressants
2. Monoamine oxidase inhibitors (MAO's) 3. Serotonin reuptake inhibitors 4. Serotonin-Norepinephrine reuptake inhbitors. |
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Which disorder appears to be related to increases in dopaminergic activity of the mesolimbic system?
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Schizophrenia
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Describe the effects of botulinum toxin
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Increases or blocks NT release into synaptic cleft, blocking the neuromuscular junction, leading to paralysis
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What does the tetanus toxin do?
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Increases or blocks NT release into the synaptic cleft, inhibits inhibitory neurons (GABA and glycine), leading to increased muscle contraction.
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What do MAO's do?
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Block the breakdown of serotonin and norepinephrine.
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What antidepressants interfere with the serotonin and/or norepinephrine uptake?
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tricyclic antidepressants
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What parts of the brain are associated with depression?
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Anterior cingulate cortex
Ventral tegmental area Suprachiasmatic nucleus (SCN) Raphe Nuclei Hypothalmic-Pituitary Adrenal Axis (HPA) |
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What happens in the Hypothalmic-Pituitary-Adrenal Axis in depression?
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Overactivity
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In depression, what occurs in the Ventral Tegmental Area?
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-shows lowered activity.
It is the area of the basal midbrain involved in reward circuit. Uses dopamine. Enhanced by cocaine and dopamine agonists. |
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What is the anterior cingulate cortex?
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The frontal part of the cingulate cortex, that resembles a "collar" form around the corpus callosum, the fibrous bundle that relays neural signals between the right and left cerebral hemispheres of the brain.
It includes both the ventral and dorsal areas of the cingulate cortex, and appears to play a role in a wide variety of autonomic functions, such as regulating blood pressure and heart rate, as well as rational cognitive functions, such as reward anticipation, decision-making, empathy and emotion. Activated by negative experiences. Deep brain stimulation in this area has helped in some cases of intractable depression. Higher activity in depressants. |
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Where is serotonin produced?
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In the Raphe nuclei (brain) and in the gut.
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What is the role of the suprachiasmatic nucleus?
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Control center of body's biological clock, determines sleep-wake cycles and temperature cycles. Dysregulation in depression. Communicates with raphe nuclei. Associated with REM.
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What is the role of serotonin?
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-Regulation of body temperature, mood, sleep, vomiting, sexuality, appetite.
-Produced in gut -Feelings of satisfaction -Decreased activity associated with depression, anxiety, compulsions, migraines, fibromyalgia, IBS. -Absent during REM sleep. -Major NT of the enteric nervous system -Excitatory effect on motor pathways |
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Which NT is synthesized from trytophan?
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Serotonin. Requires B6 as a co-enzyme.
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Where are serotonergic neurons found?
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Throughout brain, spinal cord, GI tract, blood platelets, immune cells.
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What is dysthmia?
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Chronic, low-grade depression
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Cyclothymia is also known as...
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Bipolar disorder
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Traits of major depressive disorder include:
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manic, atypical, melancholic, psychotic
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Antidepressants may stimulate neuronal regeneration in what part of the brain?
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Hippocampus
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