PSIO 201 Human Anatomy & Physiology I Lecture 4.1 - DRAFT PDF

PSIO 201 – Human Anatomy & Physiology I 1 http://assets.transductions.net/2010/02/neurons.jpg  Where We’re Going Nervous System Intro Organization Neuroglia Neurons The Brain Meninges...

PSIO 201 – Human Anatomy & Physiology I 1 http://assets.transductions.net/2010/02/neurons.jpg  Where We’re Going Nervous System Intro Organization Neuroglia Neurons The Brain Meninges Cerebrospinal fluid Blood-brain barrier https://www.art.com/products/p22109264058-sa-i7587847/robert-mcneil-hippocampal-neuron-fluorescent-micrograph.htm Ch. 12, 14 3  Lecture 4.1 Learning Objectives 1.Describe the general functions of the nervous system. 2.List and describe the divisions of the nervous system and describe how the different divisions interact with each other. 3.Describe the role of neurons and neuroglia in the nervous system and their interdependence in terms of function. 4.Describe the difference between nucleus/ganglion and tract/nerve in the context of the nervous system. 5.Describe the organization of the cerebrum in terms of gyri, sulci, hemispheres, lobes, and gray and white matter. 6.Describe the function of the meninges, their arrangement around the brain, and the spaces formed between the layers of the meninges. 7.Describe the composition, functions, and location of cerebrospinal fluid. 8.Describe the blood-brain barrier (BBB) and its components.  The Nervous 1 1 i 11 System Major function: coordinate activity to maintain homeostasis brain Ynal cord i bones joints guts Fig. 12.1, 12.2 5  The Nervous System Fig. 12.1, 12.2 6  Nervous Tissue issue Dense tissue made of two special cell types: Neurons Respond to stimuli canfunction Transmit electrical signals w neurogliacells Neuroglia Support cells Critical and necessary for normal function 7  Neuroglia Support staff of the nervous system regulatory physically 10X as many neuroglia as neurons Provide physical & regulatory support Communicate with neurons onhowtocarryoutfunction 8 http://4.bp.blogspot.com/_RBGUNdIcn0o/SacYIv8orLI/AAAAAAAAAJs/md1LB5siebk/s400/hippocampus.jpg  Oligodendrocytes forms myelin sheath multiple hf nglff from Cytoplasmic extensions wrap around axons → myelin sheath Insulates axon Greatly increases speed of electrical signals Key part of white matter critical Fig. 12.6, Table 12.1 http://tesarlab.case.edu/sites/default/files/styles/me 9 dium/public/news/image/Oligos.png?itok=nceYyikQ  Ependymal Cells Lines cavities of brain (ventricles) and central canal of spinal cord Separates fluid cavities filled with cerebrospinal fluid (CSF) fromotherdensetissue Branched extensions monitor & adjust composition of CSF Fig. 12.6, Table 12.1 10  Microglia doesn'tleavebrain spinalcord Smallest neuroglial cells exceptionally numerous CNS security force Immune cells keepseverythingouttobesafe Act like macrophages Destroy debris, waste, pathogens via phagocytosis betheydoittoowell Fig. 12.6, Table 12.1 red http://faculty.sites.uci.edu/kimgreen/files/2012/03/Lesion-mouse-NeuN-Iba-cool-DG.jpg 11  Astrocytes helpsregulateoverall process Largest and most numerous Cytoplasmic extensions Functions Regulate interstitium Blood-brain barrier formation on Yingnervous Structural framework Repair damaged tissue Neuron development Fig. 12.6, Table 12.1 12 http://www.conncad.com/gallery/cultured%20motor%20neuron%20on%20a%20monolayer%20of%20astrocytes.gif  CNS Neuroglia 4 big types Fig. 12.6, Table 12.1 13 PNS Neuroglia outside of brain spinal cord Peripheral nervous system Satellite cells similarto astrocytes Support neurosomas in ganglia (clusters of nerve cell bodies in the PNS) structuralsupport 14  PNS Neuroglia Peripheral nervous system Satellite cells Support neurosomas in ganglia (clusters of nerve cell bodies in the PNS) Schwann cells (neurilemmocytes) Cover all PNS neurons Can form myelin sheath Secrete neurotrophic factors to direct growth and connections wrapseach axon Fig. 12.9 15  Myelin milk drinkingwhole Primarilymadeof lipids solittlekidsneedtobe Protects & insulates nerve fibers (axons) Increases transmission speed one Oligodendrocytes (CNS) & Schwann cells (PNS) Doesthisbymaintainingmembrane potential severelywrapsaround neuron Minimizes ion leakage by minimizing Axon contact with ECF cellmembrane Increases thickness by as much as 100X nearlyimpossibletogetthrough thick membrane Fig. 12.8 16  Neurons Functional unit of the nervous system Special functional characteristics: Excitability – respond to stimuli Conductivity – respond to stimuli via electrical signals Secretion – electrical signal → secretion of signaling molecules Other notable features: Extreme longevity (your lifetime, >100 years) Amitotic – Most lose the ability to divide most divide High metabolic rate re it Require continuous supply of glucose & O2 https://analyticalscience.wiley.com/do/10.1002/was.00020482/full/rapidflim-1-2- 2022image2lr.jpg exeTyYantdepend 19  Generic Neuron Structure Dendrites Thin, branched extensions extendingoffof neurosomes Contain most types of organelles (no nucleus) Point of connection with other neurons cell body Receive signal, pass along toneuron neurosoma onwhattodo Fig. 12.4 20  Generic Neuron Structure Neurosoma (AKA soma, cell body) Contains nucleus, mitochondria, lysosomes, golgi, rough ER, ribosomes singlenucleus insinglecell 1/10 or less of cell volume Notthatbig Extensive cytoskeleton into axon & dendrites Fig. 12.4 21  Generic Neuron Structure Axon (AKA nerve fiber) Axon hillock – origin point of axon Vary in length (1 micrometer – 1 meter) Transmits signal from cell bodyput to axon terminal Extensive cytoskeleton Fig. 12.4 22  Generic Neuron Structure Terminal arborization Multiple branches that end in axon terminals Each axon terminal forms a synapse with the target cell Lots of synaptic vesicles filled with signaling molecules Can instead use varicosities (autonomic neurons) Extensive cytoskeleton but no ER or ribosomes can'tmakemanythingsin proteinproduction HRNA the periphery so'ma Fig. 12.4 23  Generic Neuron Structure Actual proportions Example: somatic motor neuron Neurosoma = tennis ball Dendrites = bushy mass that would fill most of the classroom Axon = 1 mile long and narrower than a garden hose Fig. 12.4 26  Neuron Classification - Function Sensory (afferent) neurons Detect & transmit info about stimuli From sensory receptors towards the CNS Info approaches the CNS Stimulus examples: temperature, light, smell, body position, pressure, etc. Typical structure: bipolar or unipolar neurons Fig. 12.3 28  Neuron Classification - Function Interneurons Most numerous type of neuron (90%) Completely within CNS Interconnect sensory & motor pathways Receive info from sensory neurons Integrate (process, store, & retrieve) information Dictate motor response by stimulating motor neurons Typical structure: multipolar neurons Fig. 12.3 29  Neuron Classification - Function Motor (efferent) neurons Carry info away from CNS Info exits the CNS Reach to effectors/target tissues (mostly muscle and glandular tissues) Enlarged axon terminals or varicosities to generate specific responses Typical structure: multipolar neurons Fig. 12.3 30 Neuron Classification Connection between neuron structure & function Motor (efferent) & interneurons Sensory (afferent) neurons 31  Variation in Neuron Structure Touch receptor Pyramidal & Purkinje cells in CNS Bipolar neuron in retina & olfactory neuron Amacrine cell in retina Fig. 12.5 32  The Central Nervous System Fig. 13.1, 14.1 34  Nervous System Organization Nucleus = a cluster of neuronal cell bodies in the CNS (plural = nuclei) Ganglion = a cluster of neuronal cell bodies in the PNS (plural = ganglia) 8 Tract = a bundle of axons in the CNS Nerve = a bundle of axons in the PNS 35 Nervous System Organization Gray vs. white matter Gray matter – neurosomas, dendrites, & synapses White matter – bundles of axons 36  The Brain 1350 cc & 3 lbs. of processing power Contains 20 billion neurons Key for complex responses Use 100% of your brain Fig. 14.1 37  Cranial Meninges Connective tissue coverings that surround the brain Functions: Protect underlying neural tissues Anchor the brain in the cranial cavity Three layers: Dura mater Subdural space Arachnoid mater Subarachnoid space Pia mater Fig. 14.5 38  Dura Mater Most superficial layer Periosteal layer = periosteum of skull (does not continue into spinal cord) Meningeal layer folds into parts of cranial cavity → separation of regions Falx cerebri – between R & L cerebral hemispheres Falx cerebelli – between R & L cerebrellar hemispheres Tentorium cerebelli – between cerebellum & cerebrum Dural sinuses form when space between layers gets larger for blood collection Fig. 14.5 39  Dura Mater Most superficial layer Periosteal layer = periosteum of skull (does not continue into spinal cord) Meningeal layer folds into parts of cranial cavity → separation of regions Falx cerebri – between R & L cerebral hemispheres Falx cerebelli – between R & L cerebrellar hemispheres Tentorium cerebelli – between cerebellum & cerebrum Dural sinuses form when space between layers gets larger for blood collection Fig. 14.5 40  Arachnoid & Pia Mater Arachnoid mater Contains spaces for blood vessels Subarachnoid space is filled with cerebrospinal fluid (CSF) Pia mater Thin protective layer of tissue Directly covers nerves and neuroglia Fig. 14.5 41  Cerebrospinal Fluid (CSF) 100-160 mL of clear, colorless fluid in ventricles & canals of CNS Composition: Filtrate from blood plasma Contains glucose, oxygen, Na+, Cl-, Mg2+, and other ions Functions: Cushioning and shock absorption Chemical protection Exchange nutrients and wastes Fig. 14.6 42  Ventricles of the Brain Fluid-filled chambers within the brain Location of CSF formation Numbered according to CSF flow From the 4th ventricle, CSF empties into the central canal of the spinal cord (or into subarachnoid space) Fig. 14.6 43  Don't need to know for exam CSF Formation & Pathway of Flow Secreted by choroid plexus in lateral ventricles (1 & 2) Ependymal cells also secrete CSF Flows into 3rd ventricle Choroid plexus adds more CSF Flows down cerebral aqueduct to fourth ventricle Choroid plexus adds more CSF Flows out of lateral apertures to fill subarachnoid space Also secretes some CSF Reabsorbed through arachnoid villi into venous sinuses Fig. 14.7 44  Blood Brain Barrier (BBB) Capillaries of the blood brain barrier are the least permeable capillaries in the body Maintains a stable environment for the brain Protects the brain from: Foreign substances in the blood Hormones and neurotransmitters that are traveling through the blood to the rest of the body Fig. 12.6 45  Blood Brain Barrier (BBB) O2, CO2, and small lipid-soluble molecules can cross the BBB Large lipid-soluble molecules (fatty acids) move slowly Negatively charged molecules cannot cross Glucose, amino acids, and other nutrients must be transported across the BBB Fig. 12.6 48  Blood Brain Barrier (BBB) Capillaries of the blood brain barrier are the least permeable capillaries in the body Endothelial cells form and maintain tight junctions between one another Astrocytes extend foot processes around capillary endothelial cells to form another barrier layer https://doi.org/10.1186/s12987-018-0117-2 47  Astrocytes Largest and most numerous Cytoplasmic extensions Functions Regulate interstitium Blood-brain barrier Structural framework Repair damaged tissue Neuron development Fig. 12.6, Table 12.1 46 http://www.conncad.com/gallery/cultured%20motor%20neuron%20on%20a%20monolayer%20of%20astrocytes.gif