Nervous System: Nervous System Basic Structure & Function


Functions:: Functions: Sensory – detect changes Integrate – make decisions Motor - respond


General Structure: General Structure


Structure - The Neuron: Structure - The Neuron Cell body – contains organelles Dendrite – receives information Axon – transmits information Difficult to culture Key to treatment of disease


Classifying Neurons: Classifying Neurons Structure Bipolar Unipolar Multipolar Function Sensory Interneurons motor


Bipolar: Bipolar One axon One dendrite Found in eyes, ears, nose


Unipolar: Unipolar One fiber extends from cell body Fiber then divides into Dendrite Axon Cell body found outside of CNS ganglia


Multipolar: Multipolar Many fibers arise from cell body One is an axon Many dendrites Cell bodies found within CNS


Neurons based on function:: Neurons based on function:


Neuroglia (glial cells): Neuroglia (glial cells) Central Nervous System Astrocytes Oligodendrocytes Microglia Ependymal cells Peripheral Nervous System Schwann cells


Schwann cells: Schwann cells Wrap around some axons Form myelin sheath Assists in transmission of impusles Found in PNS


Astrocytes: Astrocytes Star-shaped Connect neurons and blood vessels Transfer nutrients Support/scaffold Aid in metabolism of substances


Oligodendrocytes: Oligodendrocytes Star shaped Smaller than astrocytes Form myelin sheath around multiple axons Found in CNS


Microglia: Microglia Relatively small Few processes Support neurons in CNS Phagocytize bacteria and debris


Impulse conduction: Impulse conduction Movement of Na and K ions causes electrical current Stimulates adjacent membranes in wave-like fashion


Impulse conduction: Impulse conduction Myelinated faster than unmyelinated Increase in diameter increases speed High K+ = convulsions Low K+ = paralysis Anesthesia blocks flow of ions – no transmission of pain


The Synapse: The Synapse Impulse travels from dendrite To cell body To axon (presynaptic neuron) Releases neurotransmitters Neurotransmitters diffuses across synaptic cleft Influences the next neuron (postsynaptic) or effector


Neurotransmitters: Neurotransmitters Can have excitatory or inhibitory effects Summation of effects determines if impulse is triggered in next neuron Key to many nervous system disorders


The NerveIs it an organ?: The Nerve Is it an organ?


Types of Nerves: Types of Nerves Sensory Carry impulse to CNS Motor Carry impulse to effector (muscle or gland) Mixed Contains both types of fibers


Nerve Pathways: Nerve Pathways Reflex Arc Simple Components Receptor Sensory neuron Interneuron(s) Motor neuron Effector Nerve Tracts Bundles of nerve fibers Ascending (sensory) Descending (motor)


Nerve Tracts: Nerve Tracts


Reflexes: Reflexes Automatic response to stimuli Maintains homeostasis Heart rate, breathing rate, blood pressure, digestion, swallowing, sneezing, coughing, and vomiting Used for diagnosis


Reflexes: Reflexes


Meninges: Meninges Lie between bony coverings & nervous tissue Protect, nourish Dura mater Arachnoid Mater Pia Mater


Dura Mater: Dura Mater Outermost Tough fibrous connective tissue Blood vessels Nerves Forms partitions between lobes Continues into spinal canal


Slide29: Epidural space Subdural hematoma


Arachnoid Mater: Arachnoid Mater Thin Weblike No blood vessels Subarachnoid space Cerebrospinal fluid


Pia Mater: Pia Mater


Spinal Cord: Spinal Cord From foramen magnum To second lumbar vertebrae Cervical enlargement – to upper limbs Lumbar enlargement – to lower limbs


Spinal Nerves: Spinal Nerves 31 spinal cord segments = 31 pair of spinal nerves


Cross section of spinal cord: Cross section of spinal cord Core of gray matter Anterior, posterior and lateral horns Gray commissure Central canal (CSF) Some cell bodies of motor neurons Mostly interneurons Surrounded by white matter Mylenated nerve tracts


Function of Spinal Cord: Function of Spinal Cord Conducting nerve impulses Two way communication between brain and body parts Center for spinal reflexes


The Brain: The Brain 100 billion multipolar neurons Four portions Cerebrum Diencephalon Brainstem Cerebellum


Structure of cerebrum: Structure of cerebrum Cerebral hemispheres Corpus callosum Lobes (frontal, parietal, temporal and occipital) Surface Convolutions (gyri) Grooves (sulci and fissures) Cortex – gray matter (cell bodies) White matter – myelinated axons


Functions of Cerebrum: Functions of Cerebrum Provides higher brain functions Interprets sensory impulses Initiates voluntary movements Memory Reason Intelligence Personality


Functions of Cerebrum: Functions of Cerebrum Motor areas Sensory areas Association areas


Hemisphere Dominance: Hemisphere Dominance Controls the ability to use and understand language 90% left hemisphere dominant


Diencephalon: Diencephalon Thalamus Relay station for sensory impulses General awareness of sensations Hypothalamus Maintains homeostasis Visceral activities Endocrine system communication Limbic system (thalamus & hypothalamus) Controls emotional experience and expression (fight or flight)


Brainstem – connects cerebrum to spinal cord: Brainstem – connects cerebrum to spinal cord Midbrain Pons Medulla Oblongata


Cerebellum: Cerebellum