Nervous System Lecture: Grey Matter and Brain PDF

Nervous System, Cont. Chapter 14 Grey matter – SC, Brain; Structures of the Brain 1 Objectives Describe anatomical and physiological differences of white vs grey matter. List and describe components of midbrain and hindbrain De...

Nervous System, Cont. Chapter 14 Grey matter – SC, Brain; Structures of the Brain 1 Objectives Describe anatomical and physiological differences of white vs grey matter. List and describe components of midbrain and hindbrain Describe the types of tracts in cerebral white matter Describe the composition and organization of the cerebral cortex Describe the functions of the limbic system Explain the process of memory processing and storage Describe the properties behind EEGs and their significance 2 Grey Matter vs White Matter Grey matter Neurosomas Dendrites Synapses Cortex, integration centers White matter Tracts of axons Myelinated axons Relay signals 3 Cerebral Cortex Surface layer of brain Grey matter of telencephalon Two major types of neurons 1. Stellate cells Spherical, short dendrites & axons Receive input from afferent fibers 2. Pyramidal cells Synapse with other cortical neurons Output neurons Some axons leaving cortex Different thicknesses based on function of area 4 Cerebral White Matter Largest volume Glia and myelinated fibers Transmit signal between & within areas Three types of tracts 1. Projection tracts Vertical tracts 2. Commissural tracts Bridges b/t hemispheres Corpus callosum 3. Association tracts Connect regions in same hemisphere 5 Hindbrain Medulla oblongata Myelencephalon Pyramids Axons of gracile & cuneate fasciculi (nuclei) –sensory GF Decussate  medial lemniscus CF Thalamus  cortex Corticospinal tracts – motor (anterior) ML Inferior olivary nucleus ION Relay center Brain & SC to cerebellum Corticospinal tract 6 Hindbrain Pons Metencephalon Cerebellar peduncles Connecting pons & mesencephalon to cerebellum Transverse & longitudinal tracts Cerebellum to cerebellum, sensory up Hearing, equilibrium, facial sensation, chewing, salivation, urination, etc. Cranial nerves 5 – 8 Facial sensation Motor Taste Equilibrium Hearing Trigeminal –facial sensory & mastication Abducens – eye abduction Facial – taste, expressions Vestibulocochlear – hearing and equilibrium 7 Midbrain Mesencephalon Corpora quadrigemina Tectum Circled by grey matter Cerebral peduncles Oculomotor nucleus CN III & IV Reticulospinal tracts - pain Red nucleus Blood vessels Tracts w/ cerebellum Involvement w/ fine motor control’ 8 Midbrain Mesencephalon Cerebral peduncles Corpora quadrigemina Oculomotor nucleus CN III & IV Reticulospinal tracts - pain Red nucleus Substantial nigra Inhibitory motor to thalamus Cerebral crus Corticospinal tracts 9 Reticular formation (RF) RF Found in brainstem Midbrain, pons, medulla oblongata 1. Somatic motor control Reticulospinal tracts Posture and balance during movement Networks of CPGs for breathing/throat RF muscles 2. Pain control Pain signals and pain inhibitory neurons RF Damage to RF can lead to coma 10 Reticular formation (RF) RF Found in brainstem Midbrain, pons, medulla oblongata 1. Somatic motor control 2. Pain control 3. Sleep & Consciousness Projections into thalamus RF Controls signals reaching cerebrum Help regulate alertness Damage  irreversible coma RF 4. Habituation Learning what signals are important or not Damage to RF can lead to coma 11 12 Cerebellum 10% mass of cerebellum Yet…. 60% as much surface area & > 50% of all brain neurons Muscle coordination Evaluate sensory input with muscle movement Equilibrium, balance Tactile exploration 3D aspect of objects Time coordination Sound interpretation & language output 13 Thalamus Diencephalon Gateway to cerebral cortex Input to cerebrum passes through here Smell, vision, taste, touch, pressure , temp. Filtering out the unimportant Motor control pathways Receives information from basal nuclei Refines and modulates  sends info to cortex Control descending motor pathways Memory functions 14 Hypothalamus Diencephalon Beneath thalamus Endocrine control center 1. Homeostatic regulation of organs 2. Secretes hormones  control anterior pituitary 3. Integrates with autonomic regions Mapping aggression in the 4. Thermoregulation brain | Science News - YouTube 5. Regulates hunger and thirst 6. Part of memory pathways (b/t hippocampus & thalamus) 15  Optogenetics from photosynthetic Optogenetics: Use of green algae Light-gated ion channels to control the activity of genetically modified neurons in a living animal. Mapping aggression in the brain | Science News - YouTube These Fighting Fruit Flies Are Superheroes of Brain Science | Deep Look - YouTube Figure 12–44a Light-gated ion channels can control the activity of specific neurons in a living animal. (A) In this experiment, the gene encoding channelrhodopsin was introduced into a subset of neurons in the mouse hypothalamus. Ch 12: Ion Channels & APs  Light-gated Ion Channels Figure 12–44b Light-gated ion channels can control the activity of specific neurons in a living animal. When the neurons are exposed to blue light using a tiny fiber-optic cable implanted into the animal’s brain, channelrhodopsin opens, depolarizing and stimulating the channel-containing neurons. Ch 12: Ion Channels & APs  When light is switched ON the mouse becomes aggressive Figure 12–44c Light-gated ion channels can control the activity of specific neurons in a living animal. When the light is switched on, the mouse immediately becomes aggressive; when the light is switched off, its behavior immediately returns to normal. (From D. Lin et al., Nature 470:221–226, 2011.) Ch 12: Ion Channels & APs Hypothalamus 1. Paraventricular nucleus Oxytocin 2. Supraoptic nucleus ADH 3. Anterior nucleus Thirst 4. Ventromedial nucleus Hunger 5. Preoptic nucleus Reproductive function, hormones 6. Suprachiasmatic nucleus Biological clock, reproductive cycles 7. Mammillary nucleus Long term memory 19 20 Limbic System Paired - hemispheres Loop of fiber tracts Feedback loops Emotion, learning, memory 21 Memory Hippocampus Integrates sensory & cognitive experiences Learns from sensory input during an experience Short term memory Memory relayed repeatedly during sleep To cortex Long term memories formed (memory consolidation) Memory storage E.g., Vocabulary, memory of faces & objects Superior temporal lobe E.g., plans and social roles, etc. Prefrontal lobe 22 Memory Hippocampus Lesions  anterograde amnesia ”Experiments” Surgical removal of hippocampi No effect on intelligence No effect on retrograde memory Could not form new memories of people & experiences Could form new motor skills Memory stored in different parts of brain 23 Electroencephalogram (EEG) Rhythmic voltage changes Postsynaptic potentials Superficial cortex layer Study brain function (e.g., sleep, consciousness) Diagnose brain diseases, tumors, trauma Patterns of voltage fluctuations Normal vs abnormal 24 Electroencephalogram (EEG) 1. Alpha waves: awake & resting (parietal-occipital) 2. Beta waves: Mental activity & sensory stimulation (frontal- parietal) 3. Theta waves Children & tired adults Abnormal amounts in adults  stress or disorder 4. Delta waves Deep sleep (adults) If dominant when awake  major brain damage 25 Electroencephalogram (EEG) 26 Next: Nervous System, Cont. Chapters 14 & 15 Meninges, CSF formation & flow, autonomic nervous system 27