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 Left brain (hemisphere) - 90% - language - speaking - writing - personality: logical, realistic, analytical
THE NERVOUS SYSTEM Right brain (hemisphere) - 10% - tactile - visual - auditory - personality: intuitive, nonverbal, creative 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 olfactory Occasion II optic Our III oculomotor Trusty IV trochlear Truck V trigeminal Acts VI abducens Funny VII facial Very 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 (1st order neuron) b. medulla or spinal cord thalamus (2nd order neuron) c. thalamus cerebral cortex (3rd 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 spinal cord (upper motor neuron) b. spinal cord muscle (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 CNS Division (outlet) adrenergic* cholinergic* thoracolumbar craniosacral 2. General Response fight or flight rest & digest 3. Function prepare for emergency (stress) recovery 4. Heart Rate increase decrease 5. Lung Bronchi dilation constriction 6. Adrenal Medulla (Adrenalin) secretion ------------------ 7. Efferent preganglionic preganglionic postganglionic 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