THE NERVOUS SYSTEM 4 Right vs Left Hemisphere

THE NERVOUS SYSTEM 4. Right vs. Left Hemisphere - Hemispheres are separate brains which “talk” to each other through commissural fibers a. Corpus callosum b. Anterior and posterior commissures Ø Left brain (hemisphere) - 90% - language - speaking - writing - personality: logical, realistic, analytical

THE NERVOUS SYSTEM Ø Right brain (hemisphere) - 10% - tactile - visual - auditory - personality: intuitive, nonverbal, creative Ø Split brain - congenital - surgery—cure major motor seizures If left hemisphere damaged in children, language center often can be transferred to right hemisphere

THE NERVOUS SYSTEM H. Cranial Nerves - How the brain communicates with the body without using the spinal cord 1. 12 pairs 2. Differ from spinal nerves - no plexuses - no dorsal or ventral roots 3. Transmit afferent impulses - from special senses (equilibrium, vision, hearing, taste, and smell) and proprioceptors 4. Transmit efferent impulses - to eyes, face, jaw, tongue, pharynx, larynx, and parasympathetic to viscera

Plexus

Roots

THE NERVOUS SYSTEM 5. Order: Know order. Know functions for I, II, V, VIII, X On I Occasion Our olfactory II III optic oculomotor Trusty IV trochlear Truck V trigeminal Acts VI Funny Very abducens VII facial VIII vestibulocochlear Good IX glossopharyngeal Vehicle X vagus Any XI accessory How XII hypoglossal

THE NERVOUS SYSTEM 6. Olfactory nerve (I) - smell - terminates in olfactory bulb at base of frontal lobe 7. Optic nerve (II) - vision - afferent fibers terminate in primary visual area of occipital lobe 8. Trigeminal nerve (V) - afferent impulses from scalp, mouth, cornea - efferent impulses to muscles of mouth (chewing) & soft palate (swallowing)

THE NERVOUS SYSTEM 9. Vestibulocochlear nerve (VIII) - two separate nerves from inner ear a. vestibular = semicircular canals - Function: equilibrium b. cochlear = cochlea - Function: hearing 10. Vagus nerve (X) - afferent = taste, abdominal & thoracic organs - efferent = soft palate, pharynx, larynx, heart, and smooth muscles, and glands

THE NERVOUS SYSTEM SENSORY AND MOTOR SYSTEMS Transfer of information between the brain and the body Occurs through the spinal cord A. Sensory pathways - Resulting in sensory perceptions - All ascending - Require 3 neurons a. receptor medulla or spinal cord b. medulla or spinal cord c. thalamus cerebral cortex (1 st order neuron) (2 nd order neuron) (3 rd order neuron)

THE NERVOUS SYSTEM 1. Spinothalamic tracts - two types a. Anterior - tickle, itch, localized touch, pressure b. Lateral - pain and temp 1) Adjacent sensory impulses - Can block pain transmission 2) Enkephalins & endorphins - brain’s own pain killers

THE NERVOUS SYSTEM B. Motor pathways - Resulting in response at effector organ - All descending - Require 2 neurons a. cerebral cortex b. spinal cord muscle (upper motor neuron) (lower motor neuron) 1. Corticospinal tracts (pyramidal) - Impulses result in voluntary skeletal muscle movement - 90% of fibers cross over at medulla

THE NERVOUS SYSTEM AUTONOMIC NERVOUS SYSTEM (ANS) - Consists of motor neurons to smooth muscle, cardiac muscle, and glands. - Depending on the type of receptor, the neurotransmitter released may either excite or inhibit the effector. Two neurons 1. Preganglionic - cell body located in brain and spinal cord 2. Postganglionic - completely outside of CNS

THE NERVOUS SYSTEM Comparison Chart Sympathetic Parasympathetic adrenergic* thoracolumbar cholinergic* craniosacral fight or flight rest & digest prepare for emergency (stress) recovery 4. Heart Rate increase decrease 5. Lung Bronchi dilation constriction 1. CNS Division (outlet) 2. General Response 3. Function 6. Adrenal Medulla (Adrenalin) 7. Efferent secretion --------- preganglionic postganglionic

THE NERVOUS SYSTEM Adrenergic fibers - Release norepinephrine - All sympathetic postganglionic neurons (axons) - Long-lived impulse Cholinergic fibers - Release acetylcholine - All parasympathetic postganglionic neurons (axons) - All (sympathetic and parasympathetic) preganglionic neurons (axons) - Short-lived impulse