BIOH111 o Cell Module o Tissue Module o Integumentary system o Skeletal system o Muscle system o Nervous system o Endocrine system Endeavour College of Natural Health endeavour.edu.au 1
TEXTBOOK AND REQUIRED/RECOMMENDED READINGS o Principles of anatomy and physiology. Tortora et al; 14 th edition: Chapter 12 Endeavour College of Natural Health endeavour.edu.au 2
BIOH111 NERVOUS SYSTEM MODULE o Session 15 (Lectures 23 and 24) Organisation and histology of the nervous system o Session 16 (Lectures 25 and 26) Function of neurons: conduction of nerve impulses o Session 17 (Lectures 27 and 28) CNS: Brain anatomy and function o Session 18 (Lectures 29 and 30) Sensations and special senses o Session 19 (Lectures 31 and 32) Spinal cord anatomy and physiology o Session 20 (Lectures 33 and 34) Spinal nerves and somatic sensory and motor pathways o Session 21 (Lectures 35 and 36) Autonomic nervous system: anatomy and function Endeavour College of Natural Health endeavour.edu.au 3
BIOH111 Lectures 23 and 24 Organisation and histology of the nervous system Department of Bioscience endeavour.edu.au
PREPARATION FOR NEXT SESSION o NO MISSING CONCEPTS OR LINKING WORDS from Session 13 o Review: animal cell components plasma membrane tissue types o Think about cells as immature and specialised (mature) why is there a difference? Endeavour College of Natural Health endeavour.edu.au 5
OBJECTIVES Lecture 23: Divisions and structure of nervous system Describe structure and functions of nervous system Understand interactions between different components of the nervous system Neuron Describe structure and function of neuron parts and understand axonal trafficking Lecture 24: Supporting neuronal cells Describe structure and function of all neuronal supporting cells Discuss the process and function of myelination in both CNS and PNS neurons Endeavour College of Natural Health endeavour.edu.au 6
FUNCTIONS OF NERVOUS SYSTEM Overall: control and integration of all body activities within limits that maintain life. 1. Sensing changes with sensory receptors e.g. fullness of stomach or sun on your face; afferent neurons 2. Interpreting and remembering those changes - association or interneurons 3. Reacting to those changes with effectors e.g. muscular contractions (efferent neurons) and glandular secretions Endeavour College of Natural Health endeavour.edu.au 7
NERVOUS SYSTEM DIVISIONS o Central nervous system (CNS) consists of the brain and spinal cord o Peripheral nervous system (PNS) consists of cranial and spinal nerves that contain both sensory and motor fibers connects CNS to muscles, glands & all sensory receptors 3 subdivisions: 1. Somatic (voluntary) nervous system (SNS) 2. Autonomic (involuntary) nervous systems (ANS) sympathetic and parasympathetic divisions 3. Enteric nervous system (ENS) Endeavour College of Natural Health endeavour.edu.au 8
NERVOUS SYSTEM DIVISIONS Endeavour College of Natural Health endeavour.edu.au 9
STRUCTURES OF THE NERVOUS SYSTEM DIVISIONS - CNS o Brain: central part of nervous system o The spinal cord connects to the brain through the foramen magnum of the skull and is encircled by the bones of the vertebral column. Endeavour College of Natural Health endeavour.edu.au 10
STRUCTURES OF THE NERVOUS SYSTEM DIVISIONS - PNS o 12 pairs of cranial nerves: emerge from the base of the brain through foramina of the skull. o 31 pairs of spinal nerves: emerge from the spinal cord; each serves a specific region of the body o Ganglia: located outside the brain and spinal cord; small masses of nervous tissue containing primarily cell bodies of neurons o Enteric plexuses: help regulate the digestive system o Sensory receptors: found on neurons or specialized cells that monitor changes in the internal or external environment Endeavour College of Natural Health endeavour.edu.au 11
ORGANIZATION OF THE NERVOUS SYSTEM Sensory component of the PNS Motor component of PNS Effectors (muscles and glands) Endeavour College of Natural Health endeavour.edu.au 12
NERVOUS TISSUE - REVISION Composed of only two principal cell types: 1. Neurons (nerve cells) - convert stimuli into nerve impulses and conduct nerve impulses to other neurons, muscle fibers or glands. Red - glia; green - neurons 1. Neuroglia - protective and supporting cells Endeavour College of Natural Health endeavour.edu.au 13
cells tissue organ NEURONS o Functional unit of nervous system; no mitosis o Structure: Cell body: single nucleus with prominent nucleolus; Nissl bodies (chromatophilic substance); neurofilaments give cell shape and support; microtubules move material inside cell; lipofuscin pigment clumps (harmless aging) Cell processes: dendrites & axons o Function: capacity to produce action potentials (electrical excitability) Endeavour College of Natural Health endeavour.edu.au 14
DENDRITES o Structure: several per cell body; short, highly branched & unmyelinated; contain neurofibrils & Nissl bodies o Function: surfaces specialized for contact with other neurons; conduct impulses towards the cell body Endeavour College of Natural Health endeavour.edu.au 15
AXONS o Structure: only one per cell body; long, thin cylindrical process of cell; arises at axon hillock; impulses arise from initial segment (trigger zone) and are propagated via node of Ranvier; axon terminals are end branches with synaptic end bulbs filled with synaptic vesicles o Function: conduct impulses away from cell body Why are neuronal cell processes structured in this way? Endeavour College of Natural Health endeavour.edu.au 16
AXONAL TRANSPORT Notice movement of vesicles. How fast are they going? What is their direction? What do they carry? Why difference in speed? Endeavour College of Natural Health endeavour.edu.au 17
DIVERSITY IN NEURONS o Both structural and functional features are used to classify various neurons in the body. 1. Structural: based on number of processes found on cell body; 3 types 2. Functional: based on the function they perform; 3 types Endeavour College of Natural Health endeavour.edu.au 18
STRUCTURAL CLASSIFICATION Multipolar Bipolar Unipolar several dendrites & one axon most common cell type one main dendrite & one axon Retina, inner ear, olfactory one process only (develops from a bipolar) Sensory neurons Endeavour College of Natural Health endeavour.edu.au 19
COLLECTIONS OF NEURONAL TISSUE o Neuronal bodies grouped together are named: ganglion- cluster of cell bodies in PNS nucleus- cluster of cell bodies in CNS o Axons are grouped together: bundle group of axons located in PNS; connect brain to the periphery (cranial nerves) tract group of axons in CNS; interconnect neurons in spinal cord and brain Endeavour College of Natural Health endeavour.edu.au 20
FUNCTIONAL CLASSIFICATION 1. Sensory (afferent) neurons transport sensory information from skin, muscles, joints, sense organs & viscera to CNS 2. Motor (efferent) neurons conduct motor nerve impulses to muscles & glands 3. Interneurons (association) neurons connect sensory to motor neurons 90% of neurons in the body Endeavour College of Natural Health endeavour.edu.au 21
NEURONAL CIRCUITS o Neural networks are neurons organized into circuits. Neural circuit is a functional group of neurons that process specific types of information. o Function: circuit can be responsible for one or more functions; e.g. breathing; short-term memory; waking up o Structure: neuronal network may contain thousands or even millions of neurons and are arranged in several ways: simple series, diverging, converging, reverberating and parallel after-discharge circuits Endeavour College of Natural Health endeavour.edu.au 22
OBJECTIVES Lecture 23: Divisions and structure of nervous system Describe and understand interactions between different components of the nervous system Neuron Describe structure and function of neuron parts and understand axonal trafficking Lecture 24: Supporting neuronal cells Describe structure and function of all neuronal supporting cells Discuss the process and function of myelination in both CNS and PNS neurons Endeavour College of Natural Health endeavour.edu.au 23
cells tissue organ NEUROGLIA o Structure: Smaller cells than neurons; half of the volume of the CNS; 50x more numerous; undergo mitosis (tumour formation); 6 types: 1. CNS: 4 cell types astrocytes, oligodendrocytes, microglia & ependymal 2. PNS: 2 cell types Schwann and satellite cells o Function: protection and support for neurons Endeavour College of Natural Health endeavour.edu.au 24
ASTROCYTES (CNS) http://neuropathology-web.org/chapter1/chapter1bastrocytes.html o Structure: star-shaped cells o Functions: form blood-brain barrier by covering blood capillaries metabolize neurotransmitters regulate K+ balance provide structural support Brain staining astocyte around capillary In culture Endeavour College of Natural Health endeavour.edu.au 25
OLIGODENDROCYTES (CNS) o Structure: star-shaped cells; smaller then astrocytes with fewer processes o Function: form myelin sheath around the axons of CNS neurons (1 oligodendrocyte myelinates several neurons) http://vanat.cvm.umn.edu/neurlab1/glia.html Endeavour College of Natural Health endeavour.edu.au 26
o Structure: Small cells found near blood vessels in the brain; derived from cells that also gave rise to macrophages & monocytes MICROGLIA (CNS) http://bioweb.biology.uiowa.edu/daileylab/image-gallery.html Brain staining Brain staining (zoom) o Functions: phagocytic role (clear away dead cells) axonal regeneration Endeavour College of Natural Health endeavour.edu.au 27
EPENDYMAL CELLS (CNS) synapticplasticity.wix.com o Structure: columnar cells with apical cilia o Functions: form epithelial membrane lining cerebral cavities & central canal produce cerebrospinal fluid (CSF) Endeavour College of Natural Health endeavour.edu.au 28
SATELLITE CELLS (PNS) o Structure: flat cells surrounding neuronal cell bodies vanat.cvm.umn.edu o Functions: support neurons in the PNS ganglia provide nutrients and remove waste Green arrows point to satellite cells Endeavour College of Natural Health endeavour.edu.au 29
SCHWANN CELLS (PNS) http://synapse-web.org/atlas o Structure: flat cells surrounding neuronal cell axons; neurilemma is the outermost nucleated cytoplasmic layer of Schwann cells that surrounds the axon of the neuron. o Functions: produce myelin sheets Endeavour College of Natural Health endeavour.edu.au 30
MYELINATION o Structure: multilayered lipid and protein covering called the myelin sheath and produced by Schwann cells and oligodendrocytes surrounds the axons of most neurons o Function: electrical insulation of the axon increases the speed of nerve impulse conduction Endeavour College of Natural Health endeavour.edu.au 31
MYELINATION IN THE CNS o Oligodendrocytes myelinate CNS axons only o Broad, flat cell processes wrap about CNS axons, but the cell bodies do not surround the axons o Gray and white matter in CNS correspond to unmyelinated and myelinated processes of neurons Endeavour College of Natural Health endeavour.edu.au 32
MYELINATION IN THE PNS o Myelinated fibers appear white Myelin deposited by Schwann cells o Unmyelinated fibers slow, small diameter fibers Myelination process in vitro: https://www.youtube.com/watch?v=jkqvov84dcw only surrounded by neurilemma but no myelin sheath wrapping Endeavour College of Natural Health endeavour.edu.au 33
NODE OF RANVIER o Structure: gaps in axon myelin sheet; contains high concentration of ion channels; found in both CNS neurons (uncovered) and PNS neurons (covered with neurilemma) o Function: amplifies nerve impulse conduction (next session) Endeavour College of Natural Health endeavour.edu.au 34
NODE OF RANVIER o Structure: gaps in axon myelin sheet; contains high concentration of ion channels; found in both CNS neurons (uncovered) and PNS neurons (covered with neurilemma) o Function: amplifies nerve impulse conduction (next session) Na+ channel/neuron membrane Endeavour College of Natural Health endeavour.edu.au 35
Recap of Session 15 Nervous system is divided into Central Nervous system (CNS) and Peripheral Nervous System (PNS) Neurons receive and conduct information in a form of an electrical signal and have structure to support these functions. Neuronal support cells perform different functions in both CNS and PNS Endeavour College of Natural Health endeavour.edu.au 36
PREPARATION FOR NEXT SESSION o Complete missing concepts and linking words from Session 15 o Review: plasma membrane and ion channels electrical gradients across plasma membrane receptors regulated exocytosis Endeavour College of Natural Health endeavour.edu.au 37