Reflexes - Exam 5 (ECL)
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207 terms
Terms | Definitions |
|---|---|
 Reflexes | Quick, involuntary, stereotyped reactions of glands or muscle to stimulation |
| 4 important properties of a reflex | 1. Require stimulation - not spontaneous 2. Quick - involve few, if any, interneurons & minimum synaptic delay. 3. Involuntary - without intent & difficult to suppress. 4. Stereotyped - same way every time. |
| Nature of Reflexes | - Reflexes include glandular secretion and contraction of all 3 types of muscle - Unlearned skeletal muscle reflexes mediated by brainstem & spinal cord - Involve the somatic nervous system |
| Pathway of reflex arc | 1. Somatic receptors (skin, muscles or tendons) 2. Afferent nerve fibers carry info from receptors to posterior horn of spinal cord or brainstem. 3. Integrating center - point of synaptic contact between neurons in gray matter of spinal cord or brainstem which determines whether efferent neurons issue signal to muscle. 4. Efferent nerve fibers carry motor impulses to skeletal muscle. 5. Effectors react |
| How are reflexes classified? | 1. By early development. 2. By type of motor response. 3. By complexity of neural circuit. 4. By site of information processing |
| Innate reflexes | Basic neural reflexes. Formed before birth. |
| Acquired reflexes | Rapid, automatic. Learned motor patterns. |
| Somatic reflexes | Involuntary control of nervous system |
| Visceral reflexes | Autonomic. Control systems other than muscular |
| Monosynaptic reflex | Sensory neuron synapses directly onto motor neuron. No interneuron. |
| Polysynaptic reflex | At least 1 interneuron between sensory & motor neuron. Have reverberating/repeating circuits which prolong reflexive motor response. Several reflexes cooperate to produce a coordinated, controlled response |
| Where do spinal reflexes occur? | Occur in spinal cord |
| Where do cranial reflexes occur? | Occur in brain |
| What are the two ways reflexes are developed? | Innate & Acquired |
| What are the two types of motor response? | Somatic & Visceral |
| What are the two sites of information processing? | Spinal & Cranial |
| Proprioceptors | Specialized sense organs to monitor position and movement of body parts. Help you to know where your body parts are, even with eyes closed. |
| Muscle spindle | Have stretch receptors embedded in skeletal muscles. Inform brain of muscle length and body movement. Especially abundant in muscles of hand and foot. Located in perimysium, near tendons. |
| Intrafusal fibers | Muscle fibers within spindle. Have no sarcomeres, so cannot contract. |
| Types of nerve fibers in muscle spindle | Primary afferent (group la) fiber Secondary afferent (group II) fibers Gamma motor neurons Alpha fibers |
| Primary afferent | Detect changes in muscle length, very fast |
| Secondary afferent | Slower, less responsive |
| Gamma motor neurons | Go from anterior horn to contractile end of intrafusal fiber |
| Alpha fiber | Innervate working part of muscle |
| Stretch reflex | (Myotatic) - when a muscle is stretched, it fights back and contracts, maintaining increased tone and making it stiffer than unstretched muscle. |
| What is the purpose of the stretch reflex? | Helps maintain equilibrium and posture. Stabilizes joints by balancing tension in extensors and flexors smoothing muscle actions. |
| What mediates the stretch reflex? | Brain, NOT strictly spinal |
| Patellar reflex arc | 1. Tap on patellar ligament excites nerve endings of muscle spindle in quad. 2. Stretch signals travel to spinal cord via primary afferent fiber and dorsal root. 3. Primary afferent neuron stimulates alpha motor neuron in spinal cord. 4. Efferent signals in alpha motor nerve fiber stimulate quads to contract, producing knee jerk. 5. At the same time, a branch of the afferent nerve fiber stimulates the inhibitory motor neuron in the spinal cord. 6. That neuron inhibits alpha motor neuron that supplies hamstring. 7. Hamstring contraction is inhibited so hamstrings do not antagonize quads. |
| Patellar Stretch reflex | Reflexive contraction of a muscle when tendon is tapped. Multiple oscillation may be a sign of cerebellar disease. Weak or absent may be sign of dorsal spinal lesions or interruption of femoral nerve. |
| Westphal's sign | Week or absent patellar stretch reflex |
| Withdrawal Reflexes | Flexor Reflex. Move body part away from stimulus. Strength and extent of response depend on intensity and location of stimulus. |
| Reciprocal inhibition | Reflex phenomenon that prevents muscles from working against each other by inhibiting the antagonist. |
| Flexor reflex | The quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus. Protective. Polysynaptic. Requires contraction of flexors and relaxation of extensors. |
| Polysynaptic reflex arc | Pathway in which signals travel over many synapses on their way back to the muscle |
| Crossed extension reflex | Contraction of extensor muscles in the limb OPPOSITE of the one withdrawn. This stabilizes the opposite limb. |
| Ipsilateral reflex arc | One in which the sensory input and motor output are on the same sides of the spinal cord (ex. flexor) |
| Contralateral reflex arc | One in which the input and output are on opposite sites (ex. crossed extension) |
| Intersegmental reflex | One in which the input and output occur at different segments of spinal cord resulting in multiple movements. (ex. bee sting) |
| Tendon Reflex | Golgi Tendon Reflex. Response to excessive tension on the tendon. Prevents skeletal muscles from developing too much tension, tearing or breaking tendons, & promotes muscle relaxation and lengthening. Sensory receptors not like muscle spindles |
| Tendon Organs | Proprioceptors in a tendon near its junction with a muscle. Nerve fibers entwined in collagen fibers of tendon. |
| How are spinal reflexes integrated & controlled? | Behaviors are automatic, but processing centers in brain can facilitate of inhibit reflex motor patterns based in spinal cord. |
| How are voluntary movements and reflex motor patterns integrated and controlled? | Higher centers of brain incorporate lower reflexive motor patterns. Automatic reflexes can be activated by the brain as needed. They use few nerve impulses to control complex motor functions - running, walking, jumping |
| What is the order of a somatic reflex? | -Somatic receptor -Afferent nerve fiber -Interneuron -Efferent nerve fiber -Skeletal Muscle |
| Is smooth muscle ever in the somatic reflex pathway? | NO |
| Which of the following have most muscle spindles? | Muscles of the hand |
| These are properties of reflexes except: | Reflexes are spontaneous actions of the nervous system |
| The tendon reflex: | Prevents over-contraction of a muscle |
| Vision | Sight - perception of objects in the environment by means of the light that they emit or reflect |
| Light | Visible electromagnetic radiation. Light must cause a photochemical reaction to produce a nerve signal. |
| Human vision is limited to the following wavelengths: | 400 nm to 750 nm |
| Ultraviolet radiation | <400 nm - has too much energy and destroys macromolecules |
| Infrared radiation: | >750 nm - too little energy to cause photochemical reaction, but does warm tissues |
| Eyebrows | Provide facial expression. Protect eyes from glare and perspiration |
| Eyelids | Palpebrae. Block foreign objects, help with sleep, blink to moisten |
| Eyelashes | Help keep debris from eye |
| Sclera | Dense, collagenous white of the eye |
| Cornea | Anterior transparent region of sclera that admits light into the eye |
| Iris | Adjustable diaphragm |
| Pupil | Central opening of iris |
| Conjunctiva | Transparent mucous membrane that lines eyelids and covers anterior surface of eyeball, except cornea. Richly innervated & vascular. Heals quickly. Secretes a thin mucous film that prevents the eyeball from drying. |
| Tears | Flow across eyeball to help wash away foreign particles, deliver O2, and nutrients and prevent infection with a bactericidal lysozyme |
| Where do tears flow? | Through lacrimal punctum to the lacrimal sac, into the naso-lacrimal duct emptying into nasal cavity |
| How do you resolve a naso-lacrimal duct obstruction? | Lacrimal sac massage |
| What are the 6 extrinsic muscles attached to the exterior surface of the eyeball? | Superior, inferior, lateral and medial rectus muscles, superior and inferior oblique muscles |
| Which nerves innervate the extrinsic eye muscles? | Cranial nerves III, IV & VI |
| What are the 3 principal components of the eyeball? | 1. 3 tunics that form wall of eyeball. 2. Optical component admits and focuses light. 3. Neural component: retina and optic nerve |
| What are the 3 tunics of the eye? | 1. Tunica fibrosa. 2. Tunica vasculosa (uvea). 3. tunica interna |
| What is the tunica fibrosa? | The outer fibrous layer of the eye? |
| What are the two parts of the tunica fibrosa? | 1. Sclera. 2. Cornea |
| Where is the tunica vasculosa? | The middle vascular tunic layer |
| What are the 3 parts of the tunica vasculosa? | 1. Choroid. 2. Ciliary body. 3. Iris |
| Ciliary body | forms a muscular ring around the lens. Supports the lens and iris. Secretes aqueous humor |
| Iris | Colored diaphragm controlling size of pupil, its central opening. Melanin in chromatophores makes brown or black eyes. Reduced melanin makes green, blue, gray eyes |
| What is in the tunica interna? | 1. Retina. 2. Beginning of optic nerve |
| Optical Components | Transparent elements that admit light rays, refract them, and focus images on the retina |
| What are the optical components? | Cornea, aqueous humor, lens, vitreous body |
| Aqueous humor | Serous fluid posterior to cornea, anterior to lens. Released by ciliary body into posterior chamber. Passes through pupil into anterior channel. Reabsorbed by scleral venous sinus. Produced and reabsorbed at the same rate. |
| Scleral venous sinus | Canal of Schlemm |
| Lens | Lens fibers - flattened, tightly compressed, transparent cells that form lens. Suspended by suspensory ligaments from ciliary body. Changes shape to help focus light. |
| Vitreous body | Fills vitreous chamber. Transparent jelly fills space between lens and retina. |
| How does lens become more convex? | Ciliary body contracts, suspensory ligaments stretch, lens flattens. |
| What doe the neural components include? | Retina and optic nerve |
| Retina | Forms as an outgrowth of the diencephalon. Pressed against rear of eyeball by vitreous humor. |
| What does a detached retina cause? | Blurry areas in field of vision. Can lead to blindness. |
| What tool is used to examine the retina? | Opthalmoscope |
| Macula lutea | Patch of cells on visual axis of eye |
| Fovea centralis | Pit in center of macula lutea blood vessels of retina |
| Optic disc | Blind spot |
| Cataract | Clouding of lens. Lens fibers darken with age, fluid-filled bubbles and clefts filled with debris appear between fibers. |
| What are risk factors for cataracts? | Diabetes, smoking, drugs, ultraviolet radiation and certain viruses |
| How are cataracts repaired? | Replace natural lens with plastic one |
| Glaucoma | Elevated pressure within the eye due to obstruction of scleral venous sinus and improper drainage of aqueous humor. Death of retinal cells due to compression of blood vessels and lack of oxygen |
| What are symptoms of glaucoma? | Early: illusory flashes of light. Late: colored halos around lights |
| Can vision lost due to glaucoma be restored? | No |
| What is the tool used to measure intraocular pressure? | Tonometer |
| How is an image formed? | - Light passes through the lens to form a tiny inverted image on the retina. - Iris diameter controlled by two sets of contractile elements: pupillary constrictor and pupillary dilator |
| Pupillary constrictor | Smooth muscle encircling the pupil. Parasympathetic stimulation narrows the pupil |
| Pupillary dilator | Spoke-like myoepithelial cells. Sympathetic stimulation widens pupil. |
| Refraction | - Light passing through center of cornea is not bent. - Light striking off-center is bent toward center. - Aqueous humor and lens do not greatly alter the path of light. - Cornea refracts light more than lens does - lens fine-tunes image and becomes rounder to increase refraction for near vision |
| Where does the most significant refraction take place? | Cornea |
| Emmetropia | State in which the eye is relaxed and focused on an object more than 20 ft away. Light rays coming from that object are parallel. Rays focused on retina without effort. |
| What are the 3 processes required to adjust close-range vision? | - Convergence of eyes - Constriction of pupil - Accommodation of lens |
| Constriction of pupil | Blocks peripheral light rays and reduces blurry edges |
| Accommodation of lens | Change in the curvature of the lens that enables you to refract rays to focus on nearby objects. Ciliary muscle contracts, lens takes convex shape, light refracted more strongly and focused onto retina |
| Near point of vision | closest an object can be and still come into focus |
| Hyperopia | Nearsightedness. Eyeball is shorter than normal, so rays hit past back of eye |
| Myopia | Farsightedness. Eyeball is longer so rays converge before the fovea centralis |
| Astigmatism | Imperfections in shape of cornea or lens |
| Presbyopia | Loss of elasticity of lens which doesn't permit thickening of lens for near vision |
| Where does conversion of light energy into action potentials occur? | In the retina |
| How does conversion of light energy take place in retina? | -Pigment epithelium - rod & cone cells - rods and cones synapse on bipolar cells - bipolar cells - bipolar cells synapse on ganglion cells |
| structure of retina | From rear forward: photoreceptor cells bipolar cells ganglion cells |
| Photoreceptor cells | Rods, cones absorb light and generate a chemical or electrical signal and produce visual images |
| Bipolar cells | synapse with rods and cones and are first-order neurons of visual pathway |
| Ganglion cells | Largest neurons in retina and are second-order neurons of the visual pathway. Axons form optic nerve |
| From where are rods & cones derived? | From same stem cells as ependymal cells of brain |
| Rod cells | Night vision or monochromatic vision |
| Cone cells | Color, phototropic or day vision |
| What does the outer segment of cone cells contain? | Modified cilium specialized to absorb light and pigment |
| Rhodopsin | Visual pigment contained by rods. Visual purple. Has absorption peak at 500 nm. Cannot distinguish one color from another. |
| Photopsin | (Iodopsin). Retinal moiety same as in rods. Contains different amino acid sequences that determine wavelengths of light absorbed. |
| Kinds of cones | 3 kinds. Identical in appearance, but absorb different wavelengths of light to produce color vision: green, red, blue |
| How are visual signals generated? | -In the dark, rods steadily release the neurotransmitter glutamate from basal end of cell. -When rods absorb light, glutamate secretion ceases. -Bipolar cells are inhibited by glutamate and excited when secretion stops. -Bipolar cells stimulate ganglion cells. -Ganglion produce action potentials. -Via optic nerve, these changes provide visual signals to brain |
| What kind of animals have only rods and no cones? | Nocturnal animals |
| Short-wavelength cones | peak sensitivity at 420 nm |
| Medium-wavelength cones | peak at 531 nm |
| Long-wavelength cones | Peak at 558 nm |
| What percentage of men are color blind? | 8% |
| Color perception | Based on mixture of nerve signals representing cones of different absorption peaks |
| Color blindness | Have a hereditary alteration or lack of one photopsin or another. |
| What type of color blindness is most common? | Red-green |
| Red-green color blindness | Results from lack of either L or M cones. Causes difficulty distinguishing these related shades from each. |
| How does one test for color vision? | Pseudoisochromatic plate test |
| First-order neurons of visual projection pathway | Bipolar cells |
| Retinal ganglion cells | 2nd order neurons whose axons from optic nerve. |
| What combines to form optic chiasm? | 2 optic nerves |
| How is the optic chiasm formed? | Half of the fibers cross over to the opposite side of the brain and the chiasm splits to form optic tracts. |
| What does the right cerebral hemisphere see? | Objects in left visual field because their images fall on right half of each retina |
| What does each side of brain see? | What is on the side where it has motor control over the limbs. |
| Where does the optic tract end? | In the lateral geniculate nucleus of the thalamus |
| Where do 3rd order neurons project to? | Primary visual cortex of occipital lobe where conscious visual sensation occurs |
| ______ are responsible for photopic vision as well as trichromatic vision | Cones |
| Half of the fibers of each optic nerve decussate at the ___________ | optic chiasm |
| Hearing | response to vibrating air molecules |
| Equilibrium | sense of motion, body orientation and balance |
| Where do hearing & equilibrium reside? | In the inner ear - maze of fluid filled passages and sensory cells |
| What happens when the fluid in the inner ear is set in motion? | Sensory cells convert motion into an informative pattern of action potentials. |
| Sound | Any audible vibration of molecules. A vibrating object pushes on air molecules |
| Where is hearing most sensitive? | 1,500 to 5,000 Hz |
| What is a Hz? | Cycles per sound |
| At what frequency is speech? | 1,500 to 5,000 Hz |
| At what frequency is ultrasonic? | > 20,000 Hz |
| At what frequency is infrasonic? | < 20 Hz |
| What causes the eardrum to vibrate? | Air molecules hitting int |
| Loudness | Perception of sound energy, intensity, or amplitude of vibration |
| How is loudness expressed? | In decibles (dB) |
| Prolonged exposure to noice > ____ dB can cause damage to one's hearing? | 90 |
| How many sections does the ear have? | 3 |
| What are the outer and middle ear concerned with? | Only with transmission of sound to the inner ear |
| What happens in the inner ear? | Vibrations are converted to nerve signals |
| Outer ear | Funnel for conduction vibrations through the temporal bone to the tympanic membrane |
| What is another word for tympanic membrane? | Ear drum |
| Eustachian tube | AKA Auditory tube - connects middle-ear cavity to nasopharynx. Equalizes air pressure on both sides of tympanic membrane. |
| How is the eustachian tube usually shaped? | Flattened and closed |
| What opens the eustachian tube? | Swallowing and yawning |
| How do throat infections spread to middle ear? | Through the eustachian tube. |
| Components of outer ear | -Auricle - Auditory canal - Earlobe - Helix - Triangular fossa - Antihelix - Concha - External acoustic meatus - Antitragus - Tragus |
| Components of middle ear | -Auditory ossicles - Tympanic membrane - oval window - round window - Semicircular ducts |
| Auditory ossicles | Hammer, anvil & stirrup |
| Components of inner ear | - Vestibular nerve - Cochlea - Tensor tympani muscle - Auditory (Eustachian) tube |
| Otitis media | Middle ear infection. Common in children b/c auditory tube is short and horizontal. Infections spread easily from throat to tympanic cavity and mastoid air cells |
| Symptoms of otitis media | Fluid accumulates in tympanic cavity producing pressure, pain and impaired hearing. Can spread, leading to meningitis. Can cause fusion of ossicles & hearing loss |
| Tympanostomy | Lancing tympanic membrane and draining fluid from tympanic cavity |
| Labyrinth | Vestibule and 3 semicircular ducts |
| Cochlea | Snail - organ of hearing. Winds 2.5 coils around a screw-like axis of spongy bone. Threads of the screw from a spiral platform that supports the fleshy tube of the cochlea |
| How many chambers does the cochlea have? | 3 - Scala vestibuli, Scala tympani, Scala media (cochlear duct) |
| What are the chambers of the cochlea filled with? | Fluid |
| Scala vestibuli | Superior chamber. Filled with perilymph. Begins at oval window and spirals to apex. |
| Scala tympani | Inferior chamber. Filled with perilymph. Begins at apex and ends at round window. Secondary tympanic membrane covers round window |
| Scala media | Cochlear duct. Triangular middle chamber. Filled with endolymph. Separated from scala vestibula by vestibular membrane and from scala tympani by basilar membrane. Does not connect to other scala |
| Which is thicker - vestibular or basilar membrane? | Basilar |
| Organ of Corti | Spiral organ contained by scala media. Acoustic organ that converts vibrations to nerve impulses. |
| Loudness | Amplitude - variations cause variations in intensity of cochlear vibrations. Soft sound produces relatively slight up & down motion of basilar membrane. Louder sounds make basilar membrane vibrate more vigorously, which triggers higher frequency of action potentials. Brain interprets this as louder. |
| Pitch | Depends on which part of basilar membrane vibrates. At basal end, membrane attached, narrow and stiff. Brain interprets signals as high-pitched. At distal end, it is 5 times wider and more flexible. Brain interprets as low pitched |
| Deafness | Hearing loss |
| Conductive deafness | Conditions interfere with transmission of vibrations to inner ear. Damaged tympanic membrane, otitis media, blockage of auditory canal, otosclerosis |
| Otosclerosis | Fusion of auditory ossicles that prevents free vibration |
| Sensorineural deafness | Nerve deafness. Death of hair cells or any nervous system elements concerned with hearing. |
| Who are most likely to develop sensorineural deafness? | Factory workers, musicians, construction workers |
| How many neurons are in Auditory Projection pathway? | 400 nm to 750 nm |
| Equilibrium | Coordination, balance and orientation in 3-dimensional space |
| Vestibular apparatus | Constitutes receptors for equilibrium. 3 semicircular ducts |
| Semicircular ducts | Detect only angular acceleration. Change in rate of rotation. |
| What are the 2 chambers of the vestibular apparatus? | Saccule & Utricle |
| What are the saccule & utricle responsible for? | Static equilibrium and linear acceleration. |
| Static equilibrium | Perception of the orientation of the head. When head is tilted, heavy otolithic membrane sags, bending the stereocilia and stimulating the hair cells. |
| Linear acceleration | Change in velocity in a straight line (elevator) |
| Macula | 2 x 3 mm patch of hair cells and supporting cells in saccule & utricle. |
| Macula sacculi | Lies vertically on wall of saccule. Because it lies vertically, it responds to vertical acceleration & deceleration |
| Macula utriculi | Lies horizontally on floor of utricle |
| Dynamic equilibrium | In car, linear acceleration detected as otoliths lag behind, bending the stereocilia and stimulating hair cells |
| Semicircular ducts | Detect rotary movements. Bony semicircular canals of temporal bone hold membranous semicircular ducts. Each duct is filled with endolymph and opens up as a dilated sac (ampulla) next to the utricle |
| What does each ampulla contain? | Crista ampullaris - mount of hair cells and supporting cells |
| What structure is responsible for angular acceleration? | Semicircular ducts |
| What structure is responsible for linear acceleration? | Utricle |
| What structure is responsible for vertical acceleration? | Saccule |
| Stimuli by sound waves reach the brain following this pathway: | -Auditory canal - Tympanic membrane - Ossicles - Oval window - Cochlear duct - Spiral organ fibers of cochlear nerve. |
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