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Nervous System Part Three Sec 1: Peripheral NS Name: ___________________________ Sec 2: Autonomic NS Section 1: PNS Peripheral Nervous System (PNS) A. All neural structures outside the brain o Includes: Sensory ____________________ Peripheral Nerves and associated Ganglia Motor Endings B. Sensory Receptors o Specialized to respond to changes in their ______________________ (stimuli) o Activation results in graded potentials that trigger nerve impulses o Sensation (___________________ of stimulus) and perception (interpretation of the meaning of the stimulus) occur in the brain C. Classification of Sensory Receptors o Stimulus Type Mechanoreceptors- respond to ___________, pressure, vibration, stretch, and itch Thermoreceptors- sensitive to changes in _________________________ Photoreceptors- respond to light energy (retina) Chemoreceptors- respond to chemicals (smell, taste, changes in blood) Nociceptors- sensitive to _________- causing stimuli (extreme heat or cold, excessive pressure, inflammatory chemicals o Location External: Exteroceptors- receptors on skin Internal: Interoceptors (visceroceptors)receptors in internal viscera and blood vessels Proprioceptors- receptors in bones and ________________ o Structural Complexity Complex receptors- for special sense organs in localized areas Sight, smell, taste, hearing & equilibrium Simple receptors- for _____________ senses Widely distributed receptors Somatic senses (pain, temp, muscle distortion, chemical) Sec 3: Special Senses D. Sensory Integration o Input comes from exteroceptors, proprioceptors, and interceptors Input is relayed toward the head, but is ___________________ along the way Levels of neural integration in sensory systems o Receptor Level – The sensory receptors In General Receptors In Special Sense Organs stimulus receptor potential in receptor cell release of neurotransmitter generator potential in first-order sensory neuron action potentials (if threshold is reached) o Circuit level- ascending pathways Pathways of ___________ neurons conduct sensory impulses upward to the appropriate brain regions First-order neurons- conduct impulses from the receptor level to the second-order neurons in the CNS Second-order neurons- transmit impulses to the thalamus or cerebellum Third-order neurons- conduct impulses from the thalamus to the somatosensory cortex (perceptual level) o Perceptual level- neuronal circuits in the cerebral cortex Identification of the ____________________ depends on the specific location of the target neurons in the sensory cortex Aspects of Sensory Perception: o Perceptual detection- ability to detect a stimulus (requires summation of impulses) o Magnitude estimation- intensity is coded in the ____________________ of impulses o Spatial discrimination- identifying the site or pattern of the stimulus (studied by the two-point discrimination test) Main Aspects of Sensory Perception o Feature abstraction- identification of more complex aspects and __________________ stimulus properties o Quality discrimination- the ability to identify submodalities of a sensation (sweet or sour) o Pattern recognition- recognition of familiar or significant __________________ in stimuli (melody in a piece of music) E. Transmission Lines o Nerves and associated ganglia Structure of a nerve o Cordlike organ of the PNS o Bundle of myelinated and unmyelinated peripheral axons enclosed in connective tissue Connective coverings: o Endoneurium- loose connective tissue that encloses axons and their myelin sheaths o Perineurium- _______________ connective tissue that bundles fibers aka fascicles o Epineurium- tough fibrous sheath around a nerve o Ganglia Contain neuron cell bodies associated with nerves Dorsal root ganglia (sensory, somatic) Autonomic ganglia (motor, visceral) o Regeneration of nerve fibers Mature neurons are ______________ If the soma of a damaged nerve is intact, ___________ will regenerate Involves coordinated activity among: o Macrophages- remove debris o Schwann cells- form regeneration tube and secrete growth factors o Axons- regenerate damaged parts CNS oligodendrocytes bear growthinhibiting proteins that prevent CNS fiber regeneration Spinal nerves o 31 pairs of mixed nerves named according to their point of issue from the spinal cord 8 cervical (although only 7 vertebrae) 12 thoracic 5 lumbar 5 sacral 1 coccygeal Spinal nerve roots o Each spinal nerve connects to the spinal cord via two roots Ventral roots- fibers ________________ skeletal muscles Dorsal roots- conduct impulses from peripheral receptors Dorsal and ventral ____________ unite to form spinal derives, which emerge from the vertebral column via the intervertebral foramina Each spinal nerve branches into mixed rami (ramus) Rami form plexus Innervation of Nerves o Hilton’s law- any nerve serving a muscle that produces movement at a joint also innervates the joint and the __________ over the joint F. Motor Endings and Activity o Peripheral _____________ Endings are PNS elements that activate effectors by releasing neurotransmitters o Levels of Motor Control Segmental level- _______________ level of motor hierarchy, controls locomotion and specific, oft-repeated motor activity Projection level- projection motor pathways keep higher command levels informed of what is happening Pre-command level- regulate motor activity G. Reflex Activity o Inborn (intrinsic) reflex: a rapid, involuntary, predictable motor response to a stimulus o Learned (acquired) reflexes: result from practice or repetition o The Reflex Arc Components of a reflex arc (neural path) 1. Receptor- site of stimulus action 2. Sensory neuron- transmits afferent impulses to the CNS 3. Integration center- either monosynaptic or polysynaptic region within the CNS 4. Motor neuron- conducts efferent impulses from the integration center to an effector organ 5. Effector- muscle fiber or gland cell that responds to the efferent impulses by contracting or secreting o Spinal Reflexes Spinal _________________ reflexes Integration center is in the spinal cord Effectors are skeletal muscle Testing of somatic reflexes is important clinically to assess the condition of the nervous system Types of reflexes o 1. Stretch reflexes- maintain muscle tone in ______________ postural muscles o 2. Golgi tendon reflexes- help to prevent damage due to excessive _____________ o 3. Flexor withdrawal reflex - initiated by a painful stimulus o 4. Crossed extensor reflex- flexor reflexes in weight-bearing limbs to maintain balance o 5. Abdominal reflexes- contraction of abdominal muscles from touching of __________ (varies between person) o 6. Plantar reflexes- stroking lateral aspect of the sole of the foot causes toes to have downward flexion Babinki’s sign- if toes fan _________, common in infants. In adults indicates corticospinal or motor cortex damage Section 2: ANS Autonomic Nervous System (ANS) A. The ANS consists of motor neurons that: o Innervate smooth and cardiac muscle & glands o Make adjustments to ensure _______________ support for body activities o Operate via subconscious control (involuntary nervous system) B. Differences between Somatic Nervous Sys. (SNS) and Autonomic Nervous System (ANS): o Effectors SNS is __________________ muscles ANS is cardiac and smooth muscles & glands o Efferent pathways SNS- thick heavily myelinated somatic motor fiber makes up each pathway from the CNS to the muscle ANS- two neuron chain (preganglionic neuron and ganglionic neuron) C. Division of the ANS o Divisions of the ANS Sympathetic division- mobilizes the body during activity. (fight or flight system) Parasympathetic division- promotes maintenance activities and conserves body energy. Illustrated in a person who relaxes, is reading, and after a meal D. Control of ANS Functioning o Hypothalamus- main integrative ____________ of ANS activity o Subconscious cerebral input via limbic lobe connections influences hypothalamic function o Other controls come from the cerebral cortex, the reticular formation, and the spinal cord E. Developmental aspects of ANS o During youth, ANS impairments are usually due to injury o In old age, ANS efficiency declines, partially due to structural changes at preganglionic axon terminals Section 3: Special Senses A. Eye and Vision o 70% of all sensory receptors are in the _______ o Nearly half of the cerebral cortex is involved in processing visual information o Most of the eye is protected by a cushion of fat and the bony orbit o Structure of the eye Eyebrows- shade the eye and protect it from perspiration (____________) Eyelids (palpebrae)- protect the eye anteriorly, eyelashes initiate reflex blinking Conjunctiva- transparent membrane that produces a lubricating mucous secretion Lacrimal apparatus- lacrimal glands and ducts that connect to the nasal cavity and produce _____________ Extrinsic eye muscles o 6 strap-like extrinsic eye muscles that enable the eye to follow moving objects 4 rectus muscles provide movement to the eye 2 oblique muscles move the eye laterally and rotate the eye o Structure of the eyeball Wall of eyeball contains three layers o 1. Fibrous- __________ most layer that contains the sclera and cornea o 2. Vascular- middle pigment layer and contains three regions1. choroid (supplies blood) 2. ciliary body (controls lens shape) 3. iris (colored part of the eye). (Pupil controls amount of light entering the eye.) o 3. Sensory- the retina Pigmented layer absorbs __________ and stores vitamin A Neural layer has photoreceptors and transmits signals Optic disc is your ____________ spot due to lack of photoreceptors Photoreceptors (rods: operate in _____ light and provide indistinct, fuzzy, non-color peripheral vision, cones: operate in bright light and provide a high-acuity color vision) Internal cavity is filled with humors fluid Lens separate internal cavity into anterior and posterior segments B. Taste o Receptor organs are taste _________ o Taste sensations Sweet- sugars, saccharin, alcohol, and some amino acids Sour- hydrogen ions Salt- metal ions Bitter- alkaloids such as quinine and nicotine Umami- amino acids glutamate and aspartate o Taste is 80% _______________ o Thermoreceptors, mechanoreceptors, nociceptors in the mouth also influence taste o Temperature and texture enhance or detract from taste C. Smell o Organ of smell is the olfactory epithelium in the roof of the ___________ cavity o Olfactory receptor cells-bipolar neurons with radiating olfactory cilia o Bundles of axons of olfactory receptor cells form the filaments of the olfactory nerve (cranial nerve 1) o Supporting cells surround and cushion olfactory receptor cells o Basal cells lie at the base of epithelium D. Hearing and Balance o Three Parts to the Ear: o External ear (hearing)- composed of the auricle (pinna), external acoustic meatus (auditory canal) and tympanic membrane (eardrum) o Middle ear (hearing)- composed of a small airfilled, mucosa-lined cavity in the temporal bone, and the pharyngotympanic (auditory) tube equalizes pressure in the middle ear cavity with the external air pressure o Internal ear (hearing and ________________) Composed of three parts: vestibule, semicircular canals, and cochlea Three bones (ossicles) in the inner ear: malleus, incus, and stapes o Receptors for hearing and balance Respond to separate ___________________ Are activated independently o Properties of sound Sound is the pressure disturbance produced by a vibrating object Pitch is the perception of different frequencies Loudness is _______________________ to interpretation of sound intensity o Transmission of sound to the inner ear Sound waves vibrate the tympanic membrane Ossicles vibrate and amplify the pressure at the oval __________________. Pressure waves move through perilymph of the scala vestibule Waves of frequencies below the threshold of hearing travel through the helicotrema and scali tympani to the round window Sounds in the hearing range go through the cochlear duct, vibrating the basilar membrane at a specific location, according to the frequency of sound o Auditory pathways to processing Impulses from the specific __________ cells are interpreted as specific pitches ________________ is detected by increased numbers of action potentials that result when the hair cells experience larger deflections Localization of sound depends on relative intensity and relative timing of sound waves reaching both ears o Equilibrium and orientation Vestibular apparatus consists of the equilibrium receptors in the semicircular canals and vestibule o Vestibular receptors monitor static equilibrium o Semicircular can receptors monitor dynamic equilibrium Three modes of input for balance and orientation o Vestibular receptors o Visual _________________ o Somatic receptors Diagrams