* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download lecture - McLoon Lab - University of Minnesota
Environmental enrichment wikipedia , lookup
Apical dendrite wikipedia , lookup
Neural engineering wikipedia , lookup
Neural coding wikipedia , lookup
Mirror neuron wikipedia , lookup
Subventricular zone wikipedia , lookup
Metastability in the brain wikipedia , lookup
Multielectrode array wikipedia , lookup
Electrophysiology wikipedia , lookup
Central pattern generator wikipedia , lookup
Caridoid escape reaction wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Premovement neuronal activity wikipedia , lookup
Activity-dependent plasticity wikipedia , lookup
Optogenetics wikipedia , lookup
Holonomic brain theory wikipedia , lookup
Node of Ranvier wikipedia , lookup
End-plate potential wikipedia , lookup
Axon guidance wikipedia , lookup
Neuroregeneration wikipedia , lookup
Single-unit recording wikipedia , lookup
Neuromuscular junction wikipedia , lookup
Nonsynaptic plasticity wikipedia , lookup
Channelrhodopsin wikipedia , lookup
Molecular neuroscience wikipedia , lookup
Neuropsychopharmacology wikipedia , lookup
Biological neuron model wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Development of the nervous system wikipedia , lookup
Neurotransmitter wikipedia , lookup
Stimulus (physiology) wikipedia , lookup
Synaptic gating wikipedia , lookup
Nervous system network models wikipedia , lookup
Neuroanatomy wikipedia , lookup
Neuroscience 101 Steven McLoon Department of Neuroscience University of Minnesota 1 Coffee Hour Monday, Sept 12, 8:30-9:30am at Caribou Coffee 917 Washington Ave. SE 2 Major Cell Types of the Nervous System Neurons Macroglia o Oligodendrocytes & Astrocytes (CNS) o Schwann Cells & Satellite Cells (PNS) Microglia Cells associated with blood & vessels 3 Anatomy of a ‘Typical’ Neuron Soma (cell body) Dendrites Axon (only one, but can branch) Synapses 4 Anatomy of a ‘Typical’ Neuron Neurons come in many shapes and sizes (i.e. there is no ‘typical neuron’). 5 Anatomy of a ‘Typical’ Neuron Neurons have large amounts of rough endoplasmic reticulum (rER) or Nissl substance in their somas and larger dendrites. Many neurotransmitters as well as various vesicle and structural proteins are synthesized in the soma and delivered to the axon and synaptic terminals via axoplasmic transport. Axoplasmic transport goes anterograde and retrograde. 6 Neurons communicate with other cells via synapses. • Flow of information: dendrite > soma > axon > synapse • Neurotransmitter is released from the presynaptic cell at the synapse. • The transmitter diffuses across the synaptic cleft to the postsynaptic cell. 7 Neurons communicate with other cells via synapses. Neurons communicate via synapses with: Neurons o Axodendritic synapses o Axonsomatic synapses o Axonaxonic synapses o Dendrodendritic synapses Other cell types (e.g. muscle, gland, blood vessel) o Neuromuscular synapses 8 Neurons communicate with other cells via synapses. Structure of a typical synapse: Presynaptic terminal o Synaptic vesicles containing neurotransmitter o Presynaptic density Synaptic cleft Postsynaptic element o Neurotransmitter receptors o Postsynaptic density 9 Neurons communicate with other cells via synapses. An individual neuron can have one to thousands of synapses. 10 Neurons communicate with other cells via synapses. Many neurons have dendritic spines for receiving synapses. 11 Neurons communicate with other cells via synapses. Different types of neurons release different neurotransmitters. Some common neurotransmitters: class transmitter biogenic amines acetylcholine dopamine norepinephrine (noradrenaline) epinephrine (adrenaline) serotonin amino acids γ-aminobutyric acid (GABA) glutamate glycine peptides vasoactive intestinal polypeptide substance P enkephalin endorphin 12 Neurons communicate with other cells via synapses. Neurochemical communication requires the postsynaptic terminal to have the proper receptor for the neurotransmitter. The transmitter-receptor pair determines whether the active synapse will excite (depolarize) or inhibit (hyperpolarize) the postsynaptic cell. 13 Electrical Properties of Neurons A neuron at rest, that is a neuron receiving no synaptic input, maintains a higher concentration of K+ and a lower concentration of Na+ and Cl- in its cytoplasm than outside the cell. A sodium-potassium pump maintains this ion differential. A ‘resting membrane potential’ can be measured with electrodes on the inside and outside of the cell; this is typically -65mV. 14 Electrical Properties of Neurons Activation of neurotransmitter receptors causes changes in the ion conductance in the dendrites and soma. Inhibitory synaptic activity hyperpolarizes the neuron (i.e. the membrane potential becomes more negative). Excitatory synaptic activity depolarizes the neuron (i.e. makes it more positive). 15 Electrical Properties of Neurons The graded effect of all the synapses is summed at the initial segment of the axon. When the initial segment becomes sufficiently depolarized, voltage-gated sodium channels open and an action potential is generated. The influx of Na+ into the axon is followed by an outflow of K+. 16 Electrical Properties of Neurons The influx of Na+ into one segment of the axon results in opening of the sodium channels in the next part of the axon. The action potential is self propagated down the axon. When an action potential reaches the synapse, it initiates release of neurotransmitter into the synaptic cleft. 17 Astrocytes Star-shaped glial cells in the CNS Most abundant cell type of the brain and spinal cord Surround most synaspes Functions of astrocytes: Contribute to the cellular scaffolding Secrete extracellular matrix molecules Provide trophic support for neurons Form external limiting membrane of brain & spinal cord During development, serve as progenitor cells & guide cell migration Following injury or disease, phagocytize cellular debris & form glial scar 18 Astrocytes Mediate exchange between capillaries and neurons; contribute to the blood-brain barrier Regulate local blood flow Contribute to neuronal metabolism via lactate shuttle & storing glucose as glycogen 19 Astrocytes Regulate the extracellular ionic environment, which modulates synaptic transmission & plasticity Remove & recycle neurotransmitter ‘Insulate’ synapses (i.e. prevent transmitter spillover) 20 Myelin Myelin or a wrapping of glial cell membranes around axons is formed by: Schwann cells in the PNS Oligodendrocytes in the CNS 21 Myelin 22 Myelin 23 Myelin Myelin allows saltatory conduction or rapid advance of the action potential down the axon. 24 Development of Myelin Glial cells wrap around the axons, synthesize the molecules associated with myelin-type membrane, and exclude cytoplasm from all but the mesaxon and soma 25 Development of Myelin • Some tracts myelinate as early as 14wks of gestation; myelination continues until mid-adolescence. • Babinski sign is present in newborns and disappears as pyramidal tract myelinates (4mos – 2yrs of age); also associated with upper motor neuron disease in adults. • Many factors can delay myelination including poor nutrition. 26 Nervous System Organization Peripheral nervous system (PNS) includes nerves and ganglia. o Nerves are bundles of axons. o Nerves connect to the brain (cranial nerves) or to the spinal cord (spinal nerves). o Ganglia are collections of neuronal cell bodies. Central nervous system (CNS) includes the brain, spinal cord and retina. o Tracts are bundles of axons (white matter). o Neuronal cell bodies are in nuclei or layered structures (grey matter). 27 Nervous System Organization Central nervous system (CNS) includes the brain, spinal cord and retina. o Tracts are bundles of axons (white matter). o Neuronal cell bodies are in nuclei or layered structures (grey matter). 28 Major Brain Regions 29 Systems Motor vrs sensory systems 30 Systems Sensory systems Motor systems o Somatosensory o Somatic motor o Visceral sensory o Special motor o Special sensory o Autonomic (visceral) Vision Sympathetic Auditory Parasympathetic Vestibular Gustatory (taste) Olfactory (smell) 31 Spinal Cord 32 Spinal Cord 33 Spinal Cord 34 Motor Neuron 35 Motor Neuron 36 Somatosensory Neuron 37 Somatosensory Neuron 38 Autonomic System (motor) Two neuron chain: o Preganglionic neuron in brainstem or spinal cord o Ganglion neuron in PNS ganglion 39 Autonomic System (motor) Parasympathetics o Cranial (brainstem) and sacral spinal cord preganglionic neuron o Axons exit via cranial nerves or ventral roots o Ganglion near target Sympathetics o Thoracic and lumbar spinal cord preganglionic neuron o Axons exit spinal cord via ventral roots o Ganglion along vertebral column 40 Spinal Cord 41 Spinal Cord sympathetic ganglion 42 What is PNS and what is CNS? 43 Somatic & Special Motor Systems Upper motor neuron in motor cortex (most axons cross to the opposite side of the body) -synapses with (Lower) motor neuron in a cranial nerve nucleus in the brainstem or the ventral horn of the spinal cord (axons exit CNS via a cranial nerves or ventral roots) -synapses with Muscle fiber (each muscle fiber has a single neuromuscular synapse; a single motor neuron can innervate multiple muscle fibers) 44 Somatic & Special Motor Systems Motor neuron activity is influenced by many pathways including sensory reflex arcs and diverse brain structures (e.g. basal ganglia, pons, cerebellum). 45 Sensory Systems General Plan 46 Somatosensory System Small primary afferent axons for pain, temperature, pressure and touch (spinothalamic pathway) dorsal root ganglion neuron (axon enters spinal cord) neuron in dorsal horn (axon crosses and ascends to thalamus) neuron in ventral posterior lateral nucleus (axon ascends to cortex) neuron in S1 (primary somatosensory) layer IV 47 Somatosensory System Large primary afferent axons for proprioception, movement, discriminative touch (dorsal column pathway) dorsal root ganglion neuron (axon ascends in spinal cord to medulla) neuron in gracile or cuneate nucleus (axon crosses and ascends to thalamus) neuron in ventral posterior lateral nucleus (axon ascends to cortex) neuron in S1 (primary somatosensory) layer IV 48 Visual System Parts of the eye Visual System Retina: - pigment epithelium - neural retina photoreceptor cells (rods & cones) synaptic layer inner nuclear cells (horizontal, bipolar & amacrine) synaptic layer ganglion cells optic fiber (axon) layer - light path - detached retina Visual System Optic nerve (CN II) blind spot / optic nerve head = 5-8° of arc of the visual field Visual System Optic nerve (CN II): - function: special sensory – vision retinal ganglion cell (in retina) optic fiber layer (in retina) optic nerve [optic foramen] optic chiasm (in brain) optic tract (in brain) < visual nuclei (in brain) suprachiasmatic nucleus (in hypothalamus for circadian rhythm) lateral geniculate nucleus (in thalamus for vision) pretectal nucleus (at junction of thalamus & midbrain for pupillary constriction & lens) superior colliculus (in midbrain for oculomotor & head control) Visual System Visual System Vision from each side of the visual field is carried to the opposite side of the brain.