Introduction to Nervous System PDF

ANATOMY OF THE NERVOUS SYSTEM MSPC 112 / BAHS 102 LECTURE DR. KEVIN ADUTWUM-OFOSU ANATOMY, CHS,UG INTENDED LEARNING OUTCOMES ▪ At the end of the lecture students should be able to: ▪ State the role and functional significance of the nervous system ▪ Identify the major parts of the nervous sys...

ANATOMY OF THE NERVOUS SYSTEM MSPC 112 / BAHS 102 LECTURE DR. KEVIN ADUTWUM-OFOSU ANATOMY, CHS,UG INTENDED LEARNING OUTCOMES ▪ At the end of the lecture students should be able to: ▪ State the role and functional significance of the nervous system ▪ Identify the major parts of the nervous system ▪ Outline the major structural and functional subdivisions of the nervous system ▪ Distinguish between sympathetic and parasympathetic systems ▪ Distinguish between neurons and neuroglia ▪ Describe the major receptors in the nervous system  ROLE OF NERVOUS SYSTEM ▪ Perceive & respond to changes in ▪ External environment ▪ Internal environment ▪ Transport information from periphery to the spinal cord and brain ▪ Integrate various activities of the body ▪ Process information for learning ▪ Respond to information to protect the organism ▪ Function within normal physiologic limits ▪ Normal growth; reproduction SUBDIVISIONS OF THE NERVOUS SYSTEM Peripheral nervous Central nervous system (PNS) system (CNS) Cranial & Spinal Brain & nerves, & associated Spinal cord ganglia Somatic nervous system (SNS) Autonomic nervous system (ANS) TERMINOLOGIES: CENTRAL VERSUS PERIPHERAL ▪ CNS  PNS ▪ Nucleus  Ganglion ▪ Tract  Nerve ▪ Ascending  Sensory/Afferent ▪ Descending  Motor/Efferent ▪ Connective tissue covering  Connective tissue covering ▪ Pia mater  Endoneurium ▪ Arachnoid mater  Perineurium  Epineurium ▪ Dura mater TERMINOLOGIES: SOMATIC VERSUS AUTONOMIC ▪ Somatic  Autonomic/Visceral ▪ Neurons  Neurons ▪ Afferent/Sensory  Preganglionic ▪ Efferent/Motor  Postganglionic ▪ Interneuron  CENTRAL NERVOUS SYSTEM (CNS)  Integration of sensory information and responding accordingly.  Two main components: brain & spinal cord  Spinal cord: conduit for signals between the brain and the rest of the body; control of simple reflexes.  Brain: integration of most sensory information; coordination of body function  Complex functions such as thinking, feeling and homeostasis are controlled by different parts. CENTRAL NERVOUS SYSTEM (CNS)  Brain  Forebrain  Midbrain  Hindbrain  Spinal cord  Cervical segments (C1-C8)  Thoracic segments (T1-12)  Lumbar segments (L1-5)  Sacral segments (S1-5)  Coccygeal (1) DEVELOPMENT OF NERVOUS SYSTEM  Begins early (third week of development) but completed after birth  Neurulation  Neural tube formation  Migration of neural crest cells  Development of brain vesicles  Primary and secondary  Prosencephalon (Forebrain)  Tel- & Di- encephalon  Mesencephalon (Midbrain)  Rhombencephalon (Hindbrain)  Met- & Myl- encephalon  Development of spinal cord ORGANIZATION OF SPINAL CORD  Simplest form of CNS  Inner grey matter  Dorsal horn (sensory)  Ventral horn (motor)  Lateral horn (T1-L1-2) sympathetic outflow  Outer white matter  Descending tracts  Ascending tracts PARTS OF THE BRAIN  Prosencephalon (Forebrain)  Telencephalon (Cerebrum)  Diencephalon (Thalamus, Epithalamus, Hypothalamus, Subthalamus, Metathalamus)  Mesencephalon (Midbrain)  Rhombencephalon (Hindbrain)  Metencephalon (Cerebellum and Pons)  Mylencephalon (Medulla oblongata) ORGANIZATION OF BRAIN  Cerebral hemispheres (telencephalon)  Recognition  Processing  Interpretation  Storage of information  Modification of information  Recall  Utilization  Cortex (gray)  Medulla (white) ORGANIZATION OF BRAIN  Diencephalon  Thalamus  Final sensory relay station to cerebral hemisphere  Hypothalamus  Regulation of  Autonomic nervous system  Endocrine system  Epithalamus  Metathalamus  Relay of vision (sight) and audition (hearing) ORGANIZATION OF BRAIN  Mid brain  Situated between fore and hind brains  Connects fore and hind brains functionally  Hind brain  Pons  Medulla oblongata  Regulation of heart & respiration  Cerebellum  Motor coordination & balance THE PERIPHERAL NERVOUS SYSTEM  Peripheral nervous system (PNS)  Somatic  12 pairs of cranial nerves  31 pairs of spinal nerves  Visceral (autonomic)  Sympathetic  Parasympathetic  Receptors PERIPHERAL NERVOUS SYSTEM  Receptors  Afferent neurons  Efferent neuron  Effector organ  Connection with the CNS ORGANIZATION OF PNS  Cranial nerves (12 pairs)  Olfactory  Optic  Oculomotor  Trochlear  Trigeminal  Abducens (Abducent)  Facial  Vestibulo-cochlear  Glossopharyngeal  Vagus  Accessory  Hypoglossal ORGANIZATION OF PNS  Spinal nerves  Dorsal roots (sensory)  Ventral roots (motor)  Spinal nerves (mixed)  Dorsal rami  Ventral rami  Plexuses  Cervical; brachial; lumbar; sacral AUTONOMIC NERVOUS SYSTEM (ANS)  Divided into two parts:  General characteristics  Sympathetic and  Ganglia Parasympathetic  Afferent and efferent fibres  Division based on  Pre-ganglionic fibres following: (myelinated)  Anatomical differences  Post-ganglionic fibres  Differences in (nonmyelinated) neurotransmitters  Differences in physiologic effects  ORGANIZATION OF ANS SYMPATHETIC PARASYMPATHETIC  Distributed widely throughout the body  Discrete supply (Smaller of the two divisions)  Efferent outflow from thoracic and upper two lumbar segments of spinal cord  Efferent outflow from brainstem in the (Thoraco-lumbar outflow) cranium and 2nd to 4th sacral segments of spinal cord (Cranio-sacral outflow)  Ganglia situated paravertebral or prevertebral  Ganglia are located near or within viscera (organs)  Postganglionic neurotransmitter is predominantly noradrenalin or adrenaline  Both pre-ganglionic and post-ganglionic  A few such as ending to sweat glands neurotransmitter is acetylcholine produce acetylcholine  Action is discrete and is directed at  Action is widespread and prepares the conservation and restoration of energy body to deal with emergency situations- (slows down the overall activity of the "fight or flight" response body) – “rest and digest” response ORGANIZATION OF ANS  THE NEURON  Basic unit of nervous system  Types (functional)  Sensory  Motor  Integrative  Types (morphology)  Unipolar  Bipolar  Multipolar  NEURONAL PARTS: SOMA & DENDRITES  Cell body /perikaryon/ soma (5-135m)  Nucleus, neuroplasm, neurolemma  Axon hillock  Dendrites  Receptive field  Peripheral process  NEURONAL PARTS: AXONS  Conducts impulse away  Myelination  Collaterals  Myelinated  Schwann cells (PNS)  Size (diameter)  Oligodendrocytes  0.2m – 20m  Nonmyelinated  Speed of conduction  Growth rate - 1mm/day  (M/sec) 5 x diameter  NEUROGLIA ▪ Also called Glial ▪ Functions cells/Supporting cells of the nervous system ▪ Physical support ▪ Nutrition ▪ Non-excitable ▪ Myelination ▪ Smaller in size but out number neurons ▪ Homeostasis  NEUROGLIA  CNS  Astrocytes  Oligodendrocytes  Microglia  Ependymal cells  PNS  Schwann cells  Satellite cells  RECEPTORS 1  Exteroceptors (associated with external environment)  Pain (free nerve endings)  Temperature (encapsulated & free nerve endings)  Pressure (encapsulated)  Vision (rods & cones in retina)  Hearing (hair cells in organ of corti in cochlea)  Olfaction (olfactory cells in nasal mucosa)  Taste (taste buds of tongue) RECEPTORS 2  Proprioceptors (locomotor system)  Position/ balance/ movement (vestibular apparatus)  Stretch (muscle spindles)  Tension (tendon organs)  Pressure/vibration (Pacinian corpuscles) RECEPTORS 3  Interoceptors  Associated with viscera (internal organs)  Connected to the autonomic nervous system  Located in  Mucous membranes  Walls of vessels/tubular structures  Connective tissue of viscera  Types  Free nerve endings  Encapsulated  Modified epithelial cells SUMMARY ▪ Role and functional significance of the nervous system ▪ Major parts of the nervous system ▪ Major structural and functional subdivisions of the nervous system ▪ Difference between sympathetic and parasympathetic systems ▪ Difference between neurons and neuroglia ▪ Major receptors in the nervous system