Human Physiology BIOL3205 Nervous System 1 PDF

Human Physiology BIOL3205 Nervous system I - Structure Prof. Chi Bun Chan...

Human Physiology BIOL3205 Nervous system I - Structure Prof. Chi Bun Chan School of Biological Sciences 5N10 Kadoorie Biological Sciences Building (http://www.buzzle.com/articles/organs-of-the-nervous-system.html) [email protected] 39173823  Lecture outline Organization of the central nervous system (CNS) and peripheral nervous system (PNS) Cellular components of CNS and PNS Protection of CNS Functions of CNS Regeneration of CNS and PNS  Organization of the nervous system 3 nervous systems – central, peripheral and enteric Central nervous system (CNS) – brain and spinal cord Peripheral nervous system (PNS) – afferent vs efferent Somatic nervous system (voluntary actions) Autonomic nervous system – sympathetic vs parasympathetic (involuntary actions) Enteric nervous system – digestion (controlled by the autonomous system)  Neurons, glial and ependymal cells Glial cells (90%, half the volume of the Cells in the CNS brain) – support the neurons structurally and metabolically Astrocytes (star-like shape) glue of the CNS – proper spatial relationship Formation of the Blood-brain barrier (BBB) Transfer nutrients from the blood Degrade neurotransmitter Clearing toxic byproducts from the brain – “brainwashing” Oligodendrocyte Myelin sheath Microglia Inactive – release of growth factor Active – remove foreign invaders or tissue debris Involved in neurodegenerative diseases Ependymal cells Cerebrospinal fluid (CSF)  Gray and white matters Grey matter – densely packed cell body (non-myelinated) White matter – myelinated axons Brain – superior grey matter and interior white matter Spinal cord - superior white matter and interior gray matter Speed of transmission  Protection of CNS Bony structure – cranium and vertebral column Protective membranes (meninges) - dura mater, arachnoid mater, pia mater Cushioning fluid – cerebrospinal fluid (CSF) Selective entry – blood-brain barrier (BBB) (http://teachmeanatomy.info/neuro/structures/meninges/) (https://legacy.owensboro.kctcs.edu/gcaplan/anat/Notes/API%20Notes%20L%20Central%20Nervous%20System-Brain.htm)  The blood brain barrier (BBB) (https://www.reddit.com/r/pics/comments/3vr386/surface_of_a_living_human_brain/) Astrocytes form the walls of a brain capillary that are joined by tight junctions Material exchange: blood → endothelial cells → astrocyte → neuron Lipid soluble substances (O2, CO2, alcohol, steroids) are freely diffused across the BBB Pituitary and a portion of the hypothalamus are not protected by BBB Functions protects the chemical frustrations in the blood Limits access of blood-borne materials into brain tissue Limits the drug penetration Blood brain barrier (http://hplusmagazine.com/tag/blood-brain-barrier/)  Protection of CNS Bony structure – cranium and vertebral column Protective membranes (meninges) - dura mater, arachnoid mater, pia mater Cushioning fluid – cerebrospinal fluid (CSF) Selective entry – blood-brain barrier (BBB) (http://teachmeanatomy.info/neuro/structures/meninges/) (https://legacy.owensboro.kctcs.edu/gcaplan/anat/Notes/API%20Notes%20L%20Central%20Nervous%20System-Brain.htm)  The brain is hollow Embryo CNS begins as a hollow tube (neural tube) and remains (http://www.lsic.ucla.edu/classes/lifesci/central/ps107/lectures/ns-slide_7.html) hollow as the brain regions are formed Brain contains 4 interconnected ventricles (Left lateral, right lateral, 3rd, and 4th) Continued as a central canal in spinal cord Filled with cerebrospinal fluid (CSF)  Cerebrospinal fluid (CSF) Contains ~ 150 ml CSF Same density of the brain – Float or suspend in a fluid environment Formed by the choroid plexuses (specialized structure of the wall of ventricles, ependymal cells) Flows through the ventricles and spinal cord Reabsorbed by the subarachnoid space Protect the brain from bumping against the skull during sudden/jarring movement  Brain injury Car crash Shaken baby syndrome (https://sites.google.com/site/brookelindseysped/chapter-2)  Cerebral spinal fluid (CSF) Exchange materials with the interstitial fluid of neural cells (buffering) Composition is different from blood Lower K+ Trace amount of protein Facilitate ion transport for impulse formation (http://howmed.net/wp-content/uploads/2010/12/human-csf-ws-plasma.bmp)  Organization of the brain Brain stem (vegetative functions) Cerebellum (subconscious coordination of motor activity) Forebrain Diencephalon Hypothalamus (homeostasis of the internal environment) Thalamus (sensory processing) Cerebrum Basal nuclei (coordination of movement) Cerebral cortex (decision making) https://www.brainfacts.org/3d-brain#intro=false&focus=Brain-basal_ganglia-putamen&zoom=false  Characteristic of cerebral cortex Highly convoluted (gyrus and sulcus) Corpus callosum Organized into 6 layers based Gyrus on the distribution of Suclus distinctive neurons Different layering patterns and neural connections define the functional difference of Left cerebral Right cerebral various cortical areas (not hemisphere hemisphere from the presence of a unique cell type) Divided into left and right hemispheres that are connected by the corpus callosum Longitudinal fissure  Types of neurons Structural classification Number of the process (axon and dendrites) Pseudounipolar (unipolar) neurons – single axon (dendrite and axon are fused) Stimuli Bipolar neuron Multipolar Anaxonic Functional Motor Sensory Inter (99%) Action  Functional areas of the cortex Divided into lobes Frontal lobe, Parietal lobe, Occipital lobe, Temporal lobe Further divided according to specific functions Primary motor cortex Somatosensory cortex  Homunculus Depicts the location and relative amount of cortex area devoted to sensation input /motor output Uneven distribution Degree of sensitivity and movement prevision Unique for each individual Subject to constant subtle modification (plasticity of the brain)  Interaction of different brain parts Language involves expression and (?!) comprehension Wernicke’s area – language comprehension Broca’s area – govern speaking ability Damage to the specific area caused aphasia (most were caused by stroke) Wernicke’s area → cannot understand a word but speak fluently Broca’s area → cannot speak the word but understand the spoken and written word Dyslexia (reading disorder) - trouble with reading despite normal “Honorificabilitudinitatibus” intelligence  How do we identify the brain region for specific activity? Correlation of a MRI damaged brain part and impaired functional outcome Functional magnetic resonance imaging X-ray (fMRI) vs MRI Measures brain activity MRI by detecting changes associated with blood flow The 2003 Nobel Prize in fMRI Physiology or Medicine  Spinal cord A long, cylinder of nerve tissue that extends from the brain stem Protected by the vertebral column 31 pairs of spinal nerves emerge from the spinal cord through space Named according to the region of the spinal column from which they emerge – Cervical (neck), thoracic (chest); lumbar (abdominal), sacral (pelvic), and coccygeal (tailbone) Functions Serving as a link for the transmission of information between the brain and the rest of the body Integrating reflex activity without involving the brain  Structure of spinal cord (pseudounipolar neuron) Ascending tracts (spinal to brain) and descending tracts (brain to spinal) of spinal nerve Afferent fibers (from peripheral tissues) enter the spinal cord through the dorsal root The cell bodies of the afferent neurons are clustered in dorsal root ganglion Efferent fibers carrying outgoing signals to tissues exist through the ventral root Ascending and descending tracks  Nerve vs neuron Nerve is a bundle of peripheral neuronal axons enclosed by connective tissues following the same pathway Does not contain complete neuron Nerve Fibers within nerve do not influence the another E.g. telephone cable No nerves in CNS (but called Fiber tracts) (http://www.emedmd.com/content/diseases-peripheral-nerves)  Renewal of neurons Most of the neurons are produced during embryonic development and survive the life of the individual (irreplaceable) Ependymal cells serve as neural stem cells New neurons are produced in the hippocampus New neurons formed actively in this region, then died, and are exchanged for new neurons (neurogenesis) Neurogenesis vs neuroregeneration (https://www.guwsmedical.info/blood-vessels/regeneration-of-nerve-axons.html)  After the lecture, you should be able to explain Organization and structure of CNS and PNS Cellular composition of CNS and PNS and their functions Protection mechanism of the nervous system How does the BBB work? Definition of brain area and how does it work? Nerve vs tract (Re)generation of neuron