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86 Cards in this Set
- Front
- Back
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Reticular Theory vs Neuron Doctrine
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-reticular theory: no breaks- everything was one network of unbroken fibers- no idea that cells had to communicate across gaps. Held on because people liked to think of the brain, mind, and behavior was based on hydraulic theory
-neuron doctrine: cells in the nervous system were discrete units. Had gaps that you had to navigate |
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Golgi Stains
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-made it possible to study the the fine details of nervous system anatomy
-only a small fraction of the neurons take up the stain so you can actually see the size/shape of specific neurons -need a powerful microscope- no obvious gaps between the fibers and dendrites -initially thought it was in favor of reticular theory -Cajal proposed neuron doctrine afterwards |
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Tay Sachs Disease
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caused by disorder in lysosomes (digestion and recycling of cellular components)
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Transcription/Translation
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-DNA-mRNA
-After splicing mRNA leaves nucleus through nuclear membrane pores -mRNA associates with ribosomes (free or those associated with ER) -mRNA directs assembly of amino acids into proteins-signal sequences in the protein target it to nucleus, mitochondria, rough ER, etc. transcription and RNA splicing occur with the nucleus -genes inside the nucleus -transcription occurs when you unwind double helix and spit out message RNAs -message RNAs go through some post processing (splicing) -every gene has both exons and introns |
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Andreas Vesalius
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Paid particular attention to the ventricles
-hydraulic of brain function -Prevailing notion was that fluids forced out from the -Ventricles could "pump you up" |
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Descartes
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believed that the mind and body were separate entities, that the sense organs supplied the mind with information and the mind acted through the pineal to control the body. Felt that the movements were controlled by pressurized fluid flowing from the ventricles into the peripheral nerves, directed by the pineal that acted as a directional valve.
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Luigi Galvani
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-Electricity to nerves can make muscles twitch, even when separated from the brain and spinal cord-this effectively refuted the hydraulic view of nervous system function
-frog experiment -nerves conduct electricity |
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Cajal
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-suggested direction of information flow
-cell theory -principle of dynamic polarization |
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Loewi
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-experiment with cardiac muscle demonstrating release of diffusible chemical messenger
-hearts in two different chambers- chambers connected by a pump -stimulate the vagus nerve of one heart causes stimulation in the other heart -electrical signal changed into a chemical signal |
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Chemical Synapses
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-3 components: presynaptic, synaptic cleft (200-300 angstrom), postsynaptic
-Subcellular structure presynaptic - vesicles, dense projections (release sites), mitochondria postsynaptic - receptors on the membrane, postsynaptic density (anchors receptors and other molecules involved in signal transduction); -Principle of dynamic polarization is a generalization (axo-axonic synapses, dendro-dendritic synapses. |
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Electrical Synapses
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-gap junctions
-no such asymmetry -information transfer is bidirectional (through connexions) -information transfer is fast -often present among cells whose responses must be synchronized ( e.g neurons that secrete hormones |
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Dendritic Spines
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-sites of synaptic contact-allow for localized changes in ion concentrations in response to signaling
-Also can change their shape rapidly so as to affect the electrical signal generated through synaptic transmission -also sites of local protein synthesis (Synapse associated PolyRibosome Complex) -many times preferred place of contact is on the dendritic spines -spines are sites of excitatory synaptic contact -spines are motile (they can move around, twitch, move around dendritic shaft) -spine shape/structure relate to learning impairments |
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Cytoskeleton
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-filaments that give cells its structure
-made of microfilaments, neurofilaments, and microtubules |
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Microfilaments
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-smallest
-composed of two braided strands of actin polymers -particularly abundant in neurites, especially in areas of shape change -cell movement |
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Neurofilaments
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-medium sized
-provide structure to cell -most rigid (related to the intermediate filaments that exist in other cells) -found in main axon and dendrite shafts -keratin |
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Microtubules
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-largest
-column of dimers of a protein called tubulin -beaded strands of tubulin woven around a hollow core -help facilitate transport of materials up and down chain -involved in transport of materials within the cell |
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Axoplasmic Transport
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-axons do not synthesize protein (no ribosomes)
-Slow axoplasmic flow: 1-2 mm/day; movement of structural and soluble proteins (e.g.actin and tubulin) -Fast anterograde; 400-1000 mm/day kinesin, movement of products that are associated with membranous organelles(vesicles). The vesicles walk along microtubules in an ATP-dependent fashion utilizing the protein kinesin. -Fast retrograde; utilizes interactions between dynein (MAP 1C) and microtubules, recycling function, also transport of signaling molecules like some neurotrophic factors |
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Glia
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-Supporting elements
-Provide myelin sheaths to peripheral and central axons -Remove debris (e.g. degenerating cells) -Buffer ionic concentrations in the extracellular space, and take up neurotransmitters -Guidance during migration -Nutritive (e.g. supply some neurotrophic factors) -Participate in intercellular signaling |
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Schwann Cells
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-glial cells in the PNS
-forms myelin |
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Ependymal Cells
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-lines fluid-filled cavities
-forms gap junctions -create barriers between compartments -source of neural stem cells -CNS |
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Astrocytes
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-form support for the CNS
-helps form blood-brain barrier -secretes neurotrophic factors -take up K+ neurotransmitters -modulate synaptic transmission |
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Oligodendrocytes
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-forms myelin sheaths in CNS
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Microglia
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-proliferates in response to injury
-modified immune cells -acts as scavengers -CNS |
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Divisions of the CNS
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-cerebrum (bilaterally symmetrical cerebral hemispheres)
-diencephalon (thalamus and hypothalamus) -midbrain -pons -medulla -cerebellum -spinal cord |
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Somatic PNS
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-sensory neurons including dorsal root ganglia cells that convey sensory info from the muscles, skin, and joints
-motor neurons whose cell bodies actually reside in the ventral spinal cord -cranial nerves - originate in brainstem, mostly innervate head, all are part of the PNS except for the optic nerve which is part of the brain |
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Autonomic (Visceral) PNS
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-neurons innervating the smooth muscles of internal organs, glands, cardiac muscle, and blood vessels
-splits into sympathetic and parasympathetic nervous systems |
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Sympathetic Nervous System
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-part of the autonomic (visceral) PNS
-mediates fight or flight response |
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Parasympathetic Nervous System
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-part of the autonomic (visceral) PNS
-increased activity aids digestion, energy storage |
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Enteric System
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-part of the autonomic (visceral) PNS
-embedding in the linings of the esophagus, stomach, intestines, pancreas, and gall bladder -complete system that monitors tension and stretch of intestinal walls, chemical status of stomach and contents, and hormones levels--and responds to control smooth muscle motility, production of mucous and digestive secretions |
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Neural Induction
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-gastrulation brings mesoderm in contact with overlying ectoderm
-diffusible molecules from the mesoderm induce the ectoderm to begin differentiating as neural tissue |
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Neurulation
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-neural ectoderm forms neural plate
-then the neural groove develops the sides of which are called the neural folds -neural folds meet in the middle to form the neural tube (will be the central canal of the spinal cord and elaborate into the ventricular system of the brain) -some ectoderm pinches off of the neural folds to from the neural crest--this gives rise to the PNS (except the primary motor neurons) |
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Telencephalon
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-arises from the forebrain (prosencephalon)
-olfactory bulb -cerebral cortex -basal telencephalon (basal ganglia) -corpus callosum - commissure between cerebral hemispheres -internal capsule - connections with brain stem and thalamus -lateral ventricles |
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Diencephalon
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-arises from the forebrain (prosencephalon)
-thalamus - relay to cerebral cortex for sensory information -hypothalamus - control of bodily function via autonomic nervous system -third ventricle -retina and optic nerves - develop from optic vesicle that pouches off from diencephalon during development |
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Mesencephalon (Midbrain)
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-tectum (roof) - superior colliculus and inferior colliculus
-tegmentum (floor) - substantia nigra -cerebral aqueduct |
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Rhombencephalon (Hindbrain)
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Metencephalon
-cerebellum (dorsal structure) -pons (ventral structure) -fourth ventricle Myelencephalon -medulla -fourth ventricle |
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Spinal Cord Divisions
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cervical, thoracic, lumbar, sacral
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Dorsal vs Ventral
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-dorsal horn is more concerned with sensory information
-ventral horn is more concerned with motor information |
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Dorsal Column Pathway
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-touch information
-axon comes in the dorsal root, makes synapse with neuron in medulla -cross over at medulla and ascend to the thalamus -then projects to the somatosensory cortex (contralateral) |
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Corticospinal Tract
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-emanatating from contralateral primary motor cortex, travels through the internal capsule, crossing at pyramidal decussation (in medulla) and projecting to the ventral motor neurons and neurons of the intermediate zone
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Rubrospinal Tract
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-modulates motor function
-originates from the red nucleus (in tegmentum) |
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Descending Motor Modulatory Pathways
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vestibular, tectospinal, and reticulospinal
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Spinothalamic Tract
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-ascending pain pathway
-crosses upon entering the cord medulla |
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Pons
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-contains several pontine nucelei that relay motor info from cortex to contralateral cerebellum (crossed) through cerebellar peduncles
-part of reticular formation |
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Cerebellum
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-consists of cortex and several deep nuclei
-wide areas of cortex project to pontine nuclei which in turn project into the cerebellum (a huge project - through cerebella peduncles), larger than corticospinal tract -also gets vestibular input and input about limb position via spinal cord -cerebellum then projects back to the motor cortex via the thalamus -it adjusts the course of ongoing movements, compensating for errors in movement by comparing intended with actual -cerebella lesions lead to loss of smoothness in the movements; actions become disjointed -also involved in motor learning |
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Midbrain
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-tectum (dorsal) superior and inferior colliculi (vission, audition)
-tegmentum (ventral) substantia nigra projects to the striatum (caudate-putamen) and degenerates in Parkinsons -red nucleus- origin of one of the descending motor modulatory systems (rubrospinal tract) -cranial nerves 3 and 4 -periaqueduatal gray: involved in stereotyped, species specific behaviors, and modulates pain perception -cerebral aqueduct -diencephalon |
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Thalamus
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-sometimes called the gateway to the cortex
-relay nuclei: for vision (lateral geniculate), audition (medial geniculate), somatosensation (ventral posterial lateral) -nuclei that project to cortex to relay info from basal ganglia and cerebellum that modulate planned motor movement |
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Hypothalamus
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-control of autonomic nervous system
-control of pituitary function -releases two hormones: oxytocin and vasopressin -releases substances that stimulate secretion from anterior pituitary -nuclei important for thirst and hunger, sex, temperature regulation, circadian rhythmicity |
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Basal Ganglia
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-involved in initiating planning movement, cognition, reinforcement based motor learning
-consists of caudate-putamen (striatum) globus pallidus, subthalamic nucleus, and substantia nigra -striatum receives large input from sensory and motor areas of cortex, as well as posterior parietal cortex -projection from substantia nigra (degenerates in Parkinson's) -striatum then projects to globus pallidus which projects to thalamus and then to motor related areas of the frontal lobe |
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Amygdala
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-receives input from the major sensory systems and projects to neocortex, basal ganglia, hippocampus, and hypothalamus
-involved in emotions and learned fear, analyzing the emotional or motivational significance of stimuli and organizing appropriate response |
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Hippocampus
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critically important for declarative memory (memory of facts, events, persons)
-also spatial navigation and learning |
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Basal Nuclei
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degenerate in Alzheimer's
-provide diffuse cholonger input to cortex |
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Localization of Function
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-Gall: phrenology
-Flourens: experimented with selective neural ablations -Hughlings Jackson: focal epilepsy -Fritsch and Hitzig: electrical stimulation (type of movement depended on where in the cortex they stimulated) -Broca/Wernicke: languation -fMRI as modern tool |
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Broca vs Wernicke
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Broca: unable to produce language, could comprehend
Wernicke: could speak but not comprehende |
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Frontal Lobe
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-anterior to central sulcus
-contains primary motor cortex -most anterior part is calledd prefrontal cortex -receives input from all sensory areas -important for working memory (delayed response task) -planning movement |
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Parietal Lobe
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-posterior to central sulcus extending to occipital lobe
-involved in processing touch, body position through stretch and join receptors -primary somatosensory cortex is here with 4 representations of the body surface -unilateral neglect syndrome typical after damage to the right parietal lobe -may fail to dress left side -fail to draw left side of objects |
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Temporal Lobe
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-below Sylvian fissure, under your temple
-primary auditory cortex is here -language area (Wernicke's) -also area involved in face recognition |
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Occipital Lobe
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-posterior part
-primary visual cortex (striate cortex) -damage causes blindness in the contralateral visual field |
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cingulate cortex
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-seen dorsal to corpus callosum in midsaggital section
-implicated in reward based learning and in attaching emotional tone to sensory stimuli |
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insular cortex
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forms medial aspect of the lateral fissure (sulcus)
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Layer I
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-acellular layer called the molecular layer
-occupied by dendrites of the cells located deeper in the cortex and axons that travel through or form connections in this layer |
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Layer II
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-comprised maily of small spherical cells involved in local processing called granule cells
-called the external granule cell layer |
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Layer III
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-external pyramidal cell layer
-contains a variety of cell types that project to subcortical regions or through the corpus callosum -many are pyramidally shaped -the neuron located deeper in layer III are typically larger than those located more superficially |
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Layer IV
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-received thalamic inputs
-like layer II, it is made up primarily of granule cells -internal granule cell layer |
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Layer V
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-internal pyramidal cell layer
-output layer containing many pyramidal cells with long range projections -innervate mostly subcortical targets |
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Layer VI
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-output layer containing many pyramidal cells with long range projections
-polymorphic/multiform layer (heterogenous layer of neurons) -blends into the white matter that forms the deep limit of the cortex and carries axons to and from the cortex |
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Ventricles
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-chambers in the brain filled with CSF
-CSF is made by the cells of the choroid plexus in the ventricles, circulates to the subarachnoid space and is absorbed into the blood -lateral ventricles - telencephalon (anterior forebrain) -third ventricle - diencephalon (posterior forebrain) -cerebral aqueduct - mesencephalon (midbrain) -fourth ventricle - metencephalon and myelencephalon (hindbrain) -spinal canal - spinal cord -hydocephalus - blockage of CSF circulation, swells heads of infants whose skulls are still elastic. In adults, very serious bc skull is rigid |
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Meninges
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-dura mater - outer tough layer
-subdural space - normally negligible, but subdural hematoma (fills with blood) -arachnoid membrane - next to dura mater -subarachnoid space - spongy layer filled with CSF and blood vessels -pia mater - membrane that covers the brain itself (surface blood vessels embedded in this layer) |
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Membrane Potentials
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-occur because ions flowing through channels generate electrical currents that create a voltage
-I (current) = V (voltage) / R (resistance) -magnitude of the current is directly proportional to the voltage across a membrane -magnitude of the current is inversely proportional to the membrane resistance to ion flow |
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Membrane Structure
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-phospholipid bilayer
-ion channels |
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Ion Channel Structure
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-polypeptides: chain of amino acids
-membrane-spanning segments of peptides composed of hydrophobic amino acids, which naturally coil into alpha-helices -peptide segments composed of hydrophilic amino acids lie outside or inside the membrane |
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Fundamental Properties of Channels
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-channels are gated: transition from open to closed
-ions move passively: no ATP required -channels are selective: selectivity arises from chemical properties (mainly charge state) and diameter of the pore when open |
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Channel Types
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-voltage gated: open or close depending on membrane voltage
-chemically-gated: open by binding to chemical messenger, extracellular messenger (neurotransmitter, intracellular messenger (second messenger) -chemically- AND voltage-gated: need chemical messenger to mind and membrane voltage has to be favorable -mechanically gated: "stretch channels", opened by membrane deformation |
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Concentration Gradient
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Concentration Gradient = 2.3 RT log(10) ([out]/[in])
R= gas constant (~8.3 joules) T= absolute temperature (273.16 + T Celcius) [out] = extracellular concentration [in] = intracellular concentration |
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Electrical Gradient
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Magnitude (strength) of electric gradient=zFE
z= valence of the ion F= charge carried by the ion E= voltage across the membrane |
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Nernst Equation
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-calculate equilibrium
-concentration gradient=electrical gradient -E(ion) = 61.5 mv log10 ([out]/[in]) |
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Ion Pumps
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-concentration gradients established and maintained by transport proteins called "ion pumps", most important of which are the Na/K and Ca pumps
-pumps expend energy from breakdown of ATP ("active transport") to exchange ions against concentration gradient -pumps are critical for long-term maintenance of the resting potential |
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Molecular Structure of Voltage-gated Channels
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-selectivity filter: loop segments located in the poor restrict channel to specific ions
-voltage sensor: membrane-spanning segments of each domain are charged, making them voltage-sensitive -subunits organize to form the channel pore |
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Cable Properties
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Membrane Conductance
-g(m) = 1/Rm -related to channel density and conductance -determines current flow across the membrane -leakage Cytoplasmic Conductance -g(i) = 1/Ri -related to fiber diameter/volume -affects current flow along the membrane Membrane Capacitance -related to the phospholipid bilayer -separates and stores charge -affects how fast membrane potential changes when ion channels open -if you're trying to get a lot of current from one end to the other, minimize current going ACROSS the membrane, maximize amount going ALONG the membrane |
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High vs low conductance membrane
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High:
-high density of membrane channels more current flows across, and less along the membrane -propagation is slow: reduces conduction velocity Low: -has low density of membrane channels -less current flows across, more flows along the membrane -propagation is faster: increases conduction velocity |
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Electrical Synaptic Transmission
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-direct electrical communication between neurons
-electrical synapses are low-resistance electrical junction that conduct electrical potentials directly from one cell to another -current flow is typically bi-directional (non-rectifying) but sometimes uni-directional (rectifying) Advantages: -reliable -fast: no synaptic delay -efficient: electrical coupling of cell networks for coordination of activity -tough: minimal susceptibility to endogenous or exogenous ligands Disadvantages: -poor efficiency: APs in one cell cause only membrane potential changes in coupled cells -little or no plasticity: difficult to modulate or alter the effect of the synapse |
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Chemical Synaptic Transmission
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-communication via chemical messengers
Advantages: -amplification: activity in small terminals can have big effects on postsynaptic neuron activity -integration: summation of inputs in time and space -plasticity: effectiveness can be modified by "experience", trophic factors, hormones |
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Classical Neurotransmitters
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-mediate fast synaptic transmission through postsynaptic ionotropic, or transmitter-gated, ion channels
-mediate slow transmission via metabotropic, or G protein-coupled postsynaptic receptors and intracellular second messengers |
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Importance of Refractory Period
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-affects the duration of the AP
-sets maximum firing rate -prevents the AP from reinvading membrane that has just discharged, so that AP propagates away from site of initiation |
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Classical Transmitter Release
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-synthesis: in nerve terminal, often involves specialized enzymes
-storage: in synaptic vesicles (protects NT from degredative enzymes) -release: vesicles bind to specialized release sites in presynaptic membrane -stimulus: depoloarization of the ending, typically by the arrival of an AP |
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Ionotropic receptors
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-transmitter (ligand)-gated receptors
-integral part of ion channel protein -NT binding directly opens channel and permits ion currents to flow -fast and short acting |
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Metabotropic receptors
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-g protein-coupled receptors
-receptor is a membrane protein, but not an ion channel -NT binding activates a gating protein (G protein) that... --acts directly on separate ion channel --acts on enzyme that generates an intracellular second messenger that acts on another enzyme (PK) to open/close channel from cytoplasmic side -slower and longer lasting response (modulatory) |
