hths Mod 13

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  1. motor system of the brain
    • *recall motor functions are the only outputs of the nervous system
    • therefore, it includes all parts of the brain and spinal cord that are devoted to the output of the nervous system
  2. 2 divisions of motor output
    • Visceral motor
    • Somatic motor
  3. Recall what happens in the frontal lobe in cerebral cortex
    All consciousness is here; therefore all conscious movements come from here
  4. Areas of the brain responsible for producing conscious, planned movement
    • All in the frontal cortex:
    • Area 4
    • Area 6
    • Area 8
    • Area 44 & 45
  5. Area 4
    • in frontal lobe
    • precentral gyrus or primary motor cortex
    • sending axons to the α-motor neurons of the spinal cord (located in ventral horn); therefore all signals with controlled movement originate from here
    • Executing movement
  6. Area 6
    • in frontal lobe (duh)
    • supplementary motor area: Planning or imagining movement

    ☼ Imagine the 6 turned: 6 = ?  --- Hummm, your thinking
  7. Area 8
    • in frontal lobe (duh)
    • frontal eye fields
    • eye movements

    ☼ Turn 8 sideways to look like binoculars = ∞
  8. Area 44 & 45
    • in frontal lobe (duh)
    • Broca's area 
    • In most people, Broca's area on the left side is responsible for the production of speech (movements of the throat and tongue)
    • ☼ You say out loud to Seth "If you ride that bronc, I'll french kiss you"
  9. homunculus
    • "little man"
    • is the orderly map on motor and sensory parts of the body (Area 4 and Areas 3,1,2)
    • neurons which control movement form an "orderly map of the body surface" within the brain
  10. the motor homunculus
    • very similar to sensory homunculus
    • face areas are found in most lateral part of precentral gyrus, leg movements most medially
    • As we move towards midline, it goes: hand, arm, shoulder, trunk, hip, leg, toes
  11. *recall infarction
    • stroke; loss of blood supply to part of the brain
    • *different parts of the precentral gyrus (face vs leg controls) receive different blood supply. That's why some stroke victims can have facial paralysis, others may not be able to move limbs
    • ☼ "brain fart" - cause it happens IN the brain
  12. pyramidal system
    • Motor pathways:
    • An important CNS tract comprised of the cell axons which carry info about conscious, willed movement, that's planned 
    • Cell bodies are in precentral gyrus, send info (through axons) down spinal cord
    • Pathway changes names 4 or 5 times. (YAY) but still same axons
  13. Pathway of Motor info FROM brain: pyramidal system
    • Cell bodies in precentral gyrus; Send axons down to spinal cord
    • *pathway changes names, but still same axons
    • internal capsule near thalamus- starts here, changes names 2x before pyramids.
    • (medullary) pyramids - then decussates (crosses like x) @ pyramids
    • decussation of the pyramids - at level of foramen magnum
    • lateral corticospinal tract - finally, in the spinal cord
  14. internal capsule
    • where pyramidal system begins, near the thalamus
    • changes names 2x before it reaches the pyramids
    • ☼ Think of phentermine "capsule" - makes me start thinking of moving. And I start working...
  15. pyramids
    • where the axons for the pyramidal system emerge on the ventral surface of the medulla
    • *medullary pyramids
  16. decussation of the pyramids
    • after leaving the ventral surface of the medulla, (at the bottom of medulla) the axons of the pyramidal system decussate (cross in X form) at level of foramen magnum 
    • Where the "wiring" from the brain is crossed, so that the L brain controls the R side of body, and vise versa
  17. lateral corticospinal tract
    • Where the pyramidal system axons end up finally in the spinal cord
    • the pathway of the motor information (from the motor region of the cortex) W/IN THE SPINAL CORD
    • When axons reach the "right" level, they enter the anterior horn and make synapses on the motor neurons there
    • *this tract is to the lateral sides of the posterior part of the H, or butterfly wings, in the spinal cord.
    • Cort = cortex, spinal = spinal ☺
  18. upper motor neurons
    • all the neurons in the brain and spinal cord that influence movement, but do not make direct contact w a skeletal muscle fiber
    • Ex: the neurons w axons in the pyramidal system
  19. corticospinal tract
    the overall name for the pathway from the motor cortex to spinal cord
  20. decussation of the pyramids
    where the info crosses from the left side of the brain to the right side of the body, and vice versa
  21. AChE
    • acetylcholinesterase
    • the enzyme which removes ACh (acetylcholine) to stop the action potential
  22. lower motor neuron
    • term used to refer to the neuron that makes the final contact btwn the nervous system and effector organ
    • those in spinal cord that directly innervate skeletal muscle
    • Ex: alpha motor neuron (α-motor) - cell bodies in ventral horn of spinal cord, axon travels as part of nerve to neuromuscular junction on skeletal muscle
  23. motor neuron
    All neurons which cause or regulate movement
  24. Recall neurotransmitter and receptors of the somatic nervous system
    • Neurotransmitter is acetylcholine
    • Acts on nicotinic acetylcholine receptors (nAChRs) which are excitatory, cause they allow both sodium and potassium ions to pass when activated
  25. excitation-contraction coupling
    the process triggered by nAChRs (nicotinic acetylcholine receptors - which are excitatory)
  26. motor end-plate
    • also called neuromuscular junction
    • special name for the synapse btwn muscle and nerve
  27. At the neuromuscular junction of SMOOTH OR CARDIAC MUSCLE, if acetylcholine is the neurotransmitter, the receptors are:
    muscarinic acetylcholine receptors (either inhibitory or excitatory)
  28. At the neuromuscular junction of SMOOTH OR CARDIAC MUSCLE, if norepinephrine is the neurotransmitter, the receptors are:
    α- or β- adrenergic
  29. relevant stimulus
    • environmental energy (or stimulus) that is capable of being transduced by a receptor
    • each type of sensory receptor has it's own type of relevant stimulus it responds to
    • Can be quite narrowly defined... as in only certain wavelengths of light can trigger a response; only certain types of sound wavers can activate receptors in hearing, etc.
  30. transduction
    • the process through which the environmental energy (picked up by a receptor) is transformed into nervous system energy - which is then processed
    • Therefore, is the first step in any sensory system
  31. Sensory system pathways
    • *all but olfaction is relayed through thalamus
    • First transduction happens
    • then info must be taken to cortex to reach consciousness
    • there is a region of cortex responsible for perception of each kind of sensation
    • If it does not reach cortex, it's not perceived
  32. importance of thalamus
    • the master switchboard which is responsible for deciding which stimuli reaches consciousness.
    • Therefore, all sensory systems (except olfactory) are routed through the thalamus before they reach cortex
    • *if we sensed everything in our environment, we would be overwhelmed w stimuli. Thalamus takes care of that
  33. three basic types of sensory receptors
    • exteroceptors
    • interoceptors
    • proprioceptors
  34. exteroceptors
    • receive stimuli from external environment
    • includes 5 senses + 1:
    • touch, sight, sound, taste, smell, balance
  35. vestibular sense
    a 6th sense that could be added to the 5 senses: the force of gravity, either as a steady pull or in movement
  36. interoceptors
    • receive their energy from the internal environment
    • Ex: O2 levels in blood, glucose level in blood, COlevel in blood, stretch of stomach and bowel
  37. proprioceptors
    • receptors that integrate info about the state of stretch of skin, muscles and tendons, w info about gravity, in order to produce a perception of where our joints are in space
    • *Position of joints, muscles and tendons
  38. 6 types of Sensory receptors in another classification scheme
    • Mechanoreceptors
    • Thermoreceptors
    • Nociceptors
    • Photoreceptors
    • Chemoreceptors
    • Osmoreceptors
    • "My Tits Need Pleasing Caresses Only"
  39. Mechanoreceptors
    • detect movement, such as pressure of clothing on skin, a finger touching you, muscles being stretched, or pressure waves of air (sound)
    • Movement of small rocks in the inner ear produce sensation of balance
    • *axon terminals in medulla
    • FOUND IN: somatosensory, proprioception, auditory and vestibular (balance) systems
    • ☼Mechanics Sometimes Prop Anally & Vaginaly
  40. Thermoreceptors
    • detect temps btwn 4°C (40° F) and 50°C (122° F)
    • Below 40° and above 122°, tissue damage and pain results
    • axon terminals in dorsal horn of spinal cord
    • It's believed one set of thermoreceptors operates for temps below body temp and another for those above body temp
    • FOUND IN: Somatosensory system
  41. Nociceptors
    • "pain receptors" - detect harmful or damaging stimuli
    • When tissue is damaged, a # of chemical factors are released from damaged cells, which stimulates receptors on free nerve endings in skin
    • Axon terminals in dorsal horn of spinal cord
    • *derive name from same root as noxious and obnoxious
    • FOUND IN: Somatosensory system
  42. Photoreceptors
    • detect photons (particles/waves of light energy)
    • different wavelengths of light correspond to different hues: one photoreceptor type for each of the primary colors (red, yellow, blue)
    • FOUND IN: visual (sight) system - duh
  43. Chemoreceptors
    • detect chemicals in the internal or external environment
    • Ex's are found in senses of taste, smell, and O, CO2, and pH receptors which monitor the bloodstream
    • FOUND IN: Olfactory, gustatory (taste), O, CO2, pH receptors in blood
  44. Osmoreceptors
    • located in hypothalamus, detect the salt levels in blood and respond by secreting chemicals that regulate water retention or loss
    • relevant stimulus: osmotic pressure
    • FOUND IN: hypothalamus, endocrine system
    • ☼"Ocean has Salt Water"
  45. generator potential
    • the voltage change in a sensory neuron that results from the relevant stimulus being applied to the sensory nerve ending and activating on ion channel --> mechanically-gated channel
    • arises in dendritic tree
    • *triggered by the relevant stimulus; which is defined by the type of receptors the sensory neuron has
    • *equivalent of an EPSP (excitatory postsynaptic potential but in a sensory neuron)
  46. Relevant stimulus for skin
    • chemicals released from damaged skin cells = picked up by chemoreceptors & becomes a generator potential
    • temperature = picked up by thermoreceptors = generator potential
    • pressure = mechanoreceptors = generator potential
  47. Mechanoreceptors & generator potentials
    • Mechanoreceptors receive info from the environment, not other neurons
    • Therefore, they must start with a generator potential which begins w a mechanically-gated channel opening
    • *recall mechanically-gated channel opens when you deform the cell membrane (ex: being touched by someone, deforms cell membrane)
  48. *recall unipolar neurons
    • have a dendrite which picks up info, a long axon which starts at the base of the dendritic tree and extends into the CNS, and a cell body shoved off to one side somewhere in btwn
    • *Ex: sensory cells in the skin
  49. The unipolar somatosensory neuron
    • Receptor - (modified dendrite) in skin. This is where generator potential is set up
    • Axon from skin to posterior root ganglion - trigger zone where receptor meets axon
    • Cell body in posterior root ganglion - also called DRG
    • Axon terminals in CNS - some travel to brain, others make synapse in spinal cord
  50. Somatosensory Neurons
    • MECHANORECEPTORS: Meissner corpuscle (corpuscle of touch); Merkel disc (tactile disc); Pacinian corpuscle (lamellated corpuscle)
    • NOCICEPTOR: Nociceptor (pain receptor)
  51. Recall where action potentials start
    in the trigger zone
  52. Recall definition of unipolar neuron
    • also called pseudounipolar neuron
    • cell body off to the side, so info can bypass the cell body and not be processed or transformed
    • picks up info from sensory surfaces of skin and sends it, w/o processing or transformation, to be dropped off in the spinal cord
  53. In what 2 ways are action potentials in Unipolar neurons different than in multipolar neurons?
    • *recall a unipolar neuron is sensory, which aren't postsynaptic to anything
    • 1. the action potential in unipolar is triggered by summation of generator potentials (where multipolar is triggered by summation of EPSPs or IPSPs at trigger zone)
    • 2. The trigger zone for unipolar neurons is at the junction btwn the dendritic tree and the axon. Info bypasses cell body (where multipolar trigger zone is at junction btwn cell body and axon)
  54. adaption
    • the special property of sensory receptors in the skin
    • While the initial stimulus produces a burst of action potentials, the number of action potentials is reduced if the stimulus continues
    • *refers to how the response of receptors change, even when the stimulus does not
  55. Different types of skin sensory receptors
    • Are found in modified dendrites of unipolar neurons
    • 1. Meissner (touch) corpuscles - light touch
    • 2. Merkel (tactile) disks - light touch
    • 3. Free nerve endings - pain, temp, itch, hair movement
    • 4. Pacinian (lamellated) corpuscle [onion shaped]  - deep pressure, vibration 
    • Also sensation from nerve network around hair roots in thin skin
  56. Examples of Mechanoreceptors & Nociceptor
    • *Mechanoreceptors:
    • Meissner corpuscle
    • Merkel disc
    • Pacinian corpuscle
    • *Nociceptor:
    • Nociceptor - appears as free nerve endings
  57. How are skin receptors classified?
    as rapidly-adapting or slowly-adapting
  58. Which skin receptors are classified as rapidly-adapting
    • Meissner corpuscles and Pacinian corpuscles
    • When a stimulus is applied, they fire quick burst of action potentials and then shut up
    • Are vibration sensors
    • *if you want to perceive a vibration, you want a stimulus that cycles btwn on and off - not a steady stream.
  59. Which skin receptors are classified as slowly-adapting
    • Merkel corpuscles and Ruffini endings
    • These detect light touch
    • fire an initial burst of action potentials when a stimulus is applied (ex: when you put on your clothes)
    • they continue to fire at a low but steady rate for as long as the stimulus is there
  60. dermatomal map
    a map pairing regions of skin surface with the corresponding dorsal root (spinal nerve)
  61. dermatomes
    • the skin slices on a dermatomal map
    • an area of skin that is innervated by a single spinal nerve
  62. Landmark dermatomes for C6/C7
    thumb and index finger ("six-shooter")
  63. Landmark dermatomes for T4
    Nipple line
  64. Landmark dermatomes for T10
  65. Landmark dermatomes for L1 - L5
    lower extremities ("L for Legs")
  66. column
    a bunch of tracts running together
  67. posterior columns
    • carry info about light touch, vibration, and two-point discrimination directly to medulla
    • comprised of receptor axons
    • found in posterior (dorsal) part of spinal cord
    • *stays on same side of spinal cord as where it entered (ipsilateral) & goes straight to medulla (lowest part of brainstem)
  68. Division of posterior column
    • divided into 2 equal halves down center, then each side divided again
    • medial section is gracile fasciculus
    • lateral section is cuneate fasciculus
    • ☼Guts & Cutaneous (skin)
  69. recall tract
    a bundle of axons running together in CNS
  70. ALS
    • anterolateral system - also called spinothalamic tract 
    • carries info from spinal cord to thalamus
    • carries pain and temp, which is picked up by free nerve endings in skin, is carried on spinal nerves to dorsal roots.
    • In spinal cord, it's processed by 1 or more interneurons b4 it crosses across the spinal cord & carried to contralateral (opp. side) anterolateral system. Most axons terminate in thalamus
  71. Pathway of somatosensory info to conscious perception
    info is relayed to thalamus, afterwhich a 3rd-order neuron carries the skin sensation to cortex
  72. sensory homunculus
    • an orderly map of sensory on cortex; motor is similar
    • *In sensory homunculus, man looks unhappy. Prob cause he's standing on his genitals
  73. reflex
    • a quick, inborn response to a stimulus that uses just a few neurons to get the job done
    • a combination of sensory input and motor output which probably never reaches conscious perception
    • Handled totally through spinal cord
  74. What are the components of a reflex arc?
    • 1. sensory receptor - responds to a stimulus by producing a generator or receptor potential
    • 2. Sensory neuron - axon conducts impulses from receptor to integrating center
    • 3. Integrating center - one or more regions within CNS that relay impulses from sensory to motor neurons 
    • 4. Motor neurons activated - axon conducts impulses from integrating center to effector
    • 5. Effector - muscle or gland responds to the motor nerve impulses
  75. What happens in a stretch reflex
    • also called the monosynaptic stretch reflex (cause there is only one synaptic contact) - it goes directly from a receptor to a motor neuron
    • can be tested by tapping on patellar tendon below kneecap
    • passively stretches quads, stretch signal carried to spinal cord where it makes one synapse on α motor innervating quads (*notice it skips a synapse with interneuron), so then quads contract
    • *At same time, the innervation of an interneuron it used to inhibit muscle action in the antagonist muscle
  76. components of stretch reflex
    • 1. sensory receptor is stimulated by stretching
    • 2. Sensory neuron is excited, sends impulse
    • 3. Within integrating center of spinal cord, sensory neuron activated motor neuron, but also inhibits antagonistic muscles
    • 4. Motor nerves are excited, sends impulse to effector organ/muscle
    • 5. Effector (same muscle) contracts and relieves the stretching
  77. What happens with a flexor reflex?
    • This is a withdrawal reflex
    • Ex: you step on a tack
    • pain signal is sent to lumbar spinal cord, a copy of the pain signal is sent to CNS so we do have conscious perception but it's also processed by interneurons, which activate α-motor neuron in flexor muscle
    • *recall flexor reduces the angle of a joint
    • This reflex is much slower than stretch reflex cause info must pass through several synapses and interneurons
  78. Components of flexor (withdrawal) reflex
    • 1. sensory receptors stimulated (ex: stepping on tack stimulates pain-sensitive neuron)
    • 2. Sensory neuron is excited, sends impulse
    • 3. Within integrating center, sensory neuron activates interneurons in several spinal cord segments
    • 4. Motor neurons are excited and sends impulse to effectors
    • 5. Effectors are stimulated and flexor muscles contract (and withdraw leg from tack)
  79. What happens in a crossed-extensor reflex arc?
    • is an "add-on" to the flexor (withdrawal) reflex that keeps us from falling over when we activate it
    • as a joint is flexed by a flexor reflex; at the same time the info is sent to the contralateral side of spinal cord and activates extensors and inhibits flexors
    • In example with tack, keeps us from falling over
  80. Components of a crossed-extensor reflex arc
    • 1. Sensory receptors activated, stimulates pain-sensitive receptors (ex: stepping on tack with RIGHT LEG excited dendrites in RIGHT LEG)
    • 2. Sensory neurons excited, send impulse
    • 3. Within integrating center, sensory neurons activate several interneurons (ascending & descending)
    • 4. Motor neurons are excited, sends impulses to LEFT LEG effectors
    • 5. Effectors in LEFT LEG receive impulse to contract and extend LEFT leg.
  81. explain the patellar reflex
    • type of stretch reflexes
    • tap on patellar tendon passively stretches the quads, the quads then contract
    • *same stretch reflex involving diff. muscles helps u hold a cup steady when someone puts more weight in it than you expect
  82. plantar reflex
    • Observed by the stroke of the metal end of the reflex hammer along the sole of the foot
    • In normal adults, response is plantar flexor: toes curl down, toward sole of foot
  83. Babinski Sign
    • An abnormal plantar reflex
    • instead of normal response of plantar flexor, response if plantar extensor: big toe moves upward, other toes fan out laterally, away from sole of feet
    • happens with spinal cord damage, brain damage or in babies less than 1 yr old
  84. General senses
    • located over the entire body surface, including the head
    • Ex: touch, vibration, pain, temp, and proprioception (sensing the position of a joint)
  85. Special senses
    • those senses ONLY located in the head
    • Vision, Olfaction, Gustation, Audition, Vestibular Sense
  86. How many extraocular muscles are there?
    6: medial rectus, lateral rectus, superior rectus, inferior rectus, superior oblique, inferior oblique
  87. palpebrae
    • sing: palpebra
    • eyelids
  88. palpebral fissure
    space btwn the eyelids - so space when they are open and the eye can see out
  89. conjunctiva
    a thin mucous membrane that covers the sclera and is also continuous with the internal surfaces of the upper and lower palpebrae
  90. Lacrimal caruncle
    • in medial corner of eye
    • remember it drains the tears
  91. medial commissure / lateral commissure
    • medial commissure = medial corner of eye, next to lacrimal caruncle
    • lateral commissure = lateral corner of eye
  92. conjunctivitis
    • often called "pink eye"
    • when the conjunctiva becomes inflamed
    • can be causes from either a bacterial or viral infection
  93. The three tunics of the eye
    • fibrous tunic
    • vascular tunic
    • nervous tunic
  94. tunics (of the eye)
    three tissue layers that are each continuous, like layers of an onion
  95. Fibrous tunic
    • the outermost tunic of the eye
    • consists of the sclera and cornea
  96. sclera
    • part of the fibrous tunic
    • is the "white of the eye"
    • provides shape and protects the inner part of the eye
  97. cornea
    • part of the fibrous tunic
    • is the clear covering over the pupil
    • admits and refracts (bends) light
  98. vascular tunic
    • the middle of the 3 tunics
    • also called the uvea
    • consists of the iris, ciliary body, and choroid
  99. iris
    • part of the vascular tunic
    • the colored part of the eye surrounding the pupil
    • regulates amount of light that enters the eyeball
  100. ciliary body
    • Part of the uvea
    • controls the shape of the lens
    • filters blood to secrete aqueous humor into anterior chamber of eye
    • alters shape of lens for near or far vision (accommodation)
  101. choroid
    • part of the uvea
    • provides blood supply to retina and other structures of the eye
    • absorbs scattered light
  102. uvetitis
    • when the entire vascular layer is inflamed
    • may threaten the pt's sight
  103. nervous tunic
    • the innermost tunic of the eye
    • consists of retina
  104. retina
    • makes up the nervous tunic
    • receives light and converts it into receptor potentials and nerve impulses
    • Output to brain is via axons of ganglion cells which form the optic (II) nerve
  105. Name accessory structures of the eye
    • palpebrae
    • eyelashes
    • eyebrows
    • lacrimal apparatus (lacrimal glands & ducts)
    • extrinsic eye muscles
  106. How are the eyelids controlled?
    in part by smooth muscle and in part by skeletal muscle
  107. ptosis
    • the condition that results when the nerves that innervate the eyelids are damaged by trauma or disease
    • ☼When someone is high on POT, their eyelids are half closed
  108. epicanthal fold
    • epi = "near" ; canthus = "corner or eye"
    • skin fold in medial corner of eye
    • Normal in individuals of Asian decent & some other races
    • *BUT can be seen in persons w genetic abnormalities, such as Downs or chromosome 5p deletion (Cri du chat syndrome)
    • Commonly noted on pt charts
  109. Together, what do the eyelashes, eyebrows, and lacrimal apparatus do?
    • all work together to keep objects out of the eye
    • moisten and wash objects out of the eye if they do touch the surface
  110. In reference to the 4 "rectus" eye muscles, what does "rectus" mean?
    • rectus means straight
    • so the rectus muscles pull the eye straight; either medially, laterally, inferiorly, or superiorly
  111. lacrimal apparatus
    includes lacrimal glands and lacrimal ducts
  112. lacrimal glands
    • makes tears
    • are almond-shaped organs located along the lateral aspect of upper palpebra
  113. lacrimal ducts
    ducts which take tears from the lacrimal glands to the surface of the eye
  114. lacrimal canals
    drains accumulated tears from eye surface to the nasolacrimal duct in the nasal cavity
  115. nasolacrimal duct
    • the duct in the nasal cavity which is fed by the lacrimal canals
    • this is why your nose runs when you cry
    • You, obviously, have overactive lacrimal canals and nasolacrimal ducts
  116. recall the 3 chambers of the eye
    • anterior, then posterior, then
    • vitreous chamber
  117. anterior chamber of eye
    located btwn the lens and inside of the cornea
  118. posterior chamber of eye
    along the interior surface of the iris, btwn lens and iris
  119. vitreous chamber
    • contains the vitreous body that helps maintain shape of eyeball and keeps the retina attached to the choroid
    • filled with vitreous humor (not recyclable)
  120. aqueous humor
    • made & secreted by the ciliary body
    • fluid in anterior & posterior chambers of eye
    • is a filtrate of the blood that nourishes the lens and cornea (these structures have no blood supply, cause blood vessels would destroy the optical properties of these clear structures)
  121. Aqueous humor flow
    • made at ciliary body
    • flows along posterior surface or iris (in posterior chamber)
    • over surface of lens and passes through pupil into anterior chamber
    • flows along anterior surface of iris
    • passes into canal of Schlemm
    • returns to venous system
  122. iridocorneal angle
    • the junction btwn the iris and cornea
    • location of scleral venous sinus
  123. canal of Schlemm
    • also called scleral venous sinus
    • a structure (sinus - small hole) located in the sclera at the junction btwn the iris and cornea (iridocorneal angle
    • dumps aqueous humor back in the bloodstream
  124. glaucoma
    • the resulting disease when the drainage of aqueous humor is partially or completely blocked (commonly) OR the ciliary body overproduces aqueous humor (rarely)
    • the imbalance results in increased pressure in eye
    • blindness or loss of eye can result from pressure through vitreous humor to retina and cutting off blood supply to retina
    • drugs which scrunch up iris (such as epinephrine) may block scleral venous sinus and either cause glaucoma or make it worse
  125. lens
    • a clear structure shaped like an M&M
    • works with cornea to focus an image on near and far objects
    • refracts light
  126. ciliary muscles
    • part of ciliary body
    • muscles which pull on zonular fibers to flatten or relax lens in order to focus
  127. zonular fibers
    • those fibers attached to the lens &  the ciliary muscle
    • acts to flatten or relax lens
  128. What happens when the eye is focused on a distant object?
    the ciliary muscle pulls on the zonular fibers which flattens the lens (which is regularly a shape of an M&M)
  129. What happens when the eye is focused on a object that is near?
    The ciliary muscle relaxes, and the lens snaps back into a more spherical shape (like a peanut M&M)
  130. accommodation
    • the process which changes the shape of the lens to focus on objects near and far
    • Distance : lens flattens due to pull of zonular fibers connecting ciliary muscle to lens
    • Near: lens rounds passively because of it's elasticity
  131. presbyopia
    • a condition in which the elasticity of the lens is lost, along with the ability to focus on near objects
    • because lens never assumes the "peanut M&M" shape, it's impossible to focus on near objects, while the ability to focus on distant objects is preserved.
    • "elder vision" - happens with age
  132. Pathway of light through structures of eye
    • light rays pass first through cornea and are bent (refracted) by the lens
    • This focuses an image on the receptor surface (retina)
  133. emmetropia
    the condition of perfect focus
  134. myopia
    • the condition in which the lens and cornea focus the image internal to the retina (doesn't quite reach retina)
    • also called "nearsightedness"
    • images close to eye are in focus, images further away are not in focus
    • Can be corrected w concave lens: glasses, contact lenses, or Lasik surgery
    • *since Lasik only changes the shape of the cornea, does not alter properties of lens, so presbyopia still present after Lasik in older persons
  135. hyperopia
    • the condition in which the image is focused external (past) to the retina
    • Can focus on far away objects, can't focus on near objects
    • Convex lenses are used to correct
    • surgery may be used, but conventional lasik doesn't help
  136. electromagnetic radiation spectrum
    • electromagnetic radiation is energy in the form of waves that radiates from the sun. Many types: gamma rays, x-rays, UV rays, visible light, etc.
    • The electromagnetic spectrum refers to the range of electromagnetic radiation
    • All energy in the spectrum is carried by photons
  137. Wavelength
    • the distance btwn wave lengths
    • corresponds to hue/color
  138. Electromagnetic wave length vs amount of energy
    • Longer wavelength = lower energy : radio waves, microwaves
    • Little shorter is Visible spectrum = color corresponds to wavelength
    • Shorter wavelength = higher energy : UV, X-rays, Gamma rays
  139. amplitude
    • distance btwn the crest and trough of the wave
    • corresponds to the brightness of the light
    • ☼What's your "attitude" - are you bright and cheery or dark and moody?
  140. photoreceptors
    • transduce photons (particle-waves of light energy) into an electrochemical signal
    • 4 types: Rods, long-wavelength cones, medium-wavelength cones, and short-wavelength cones
  141. Long vs. medium vs. short wavelength cones
    • *Cones are specialized to code for color info
    • Long WL responds best to red colors
    • Medium WL responds best to yellow
    • Short WL responds best to blue
    • Thus the three primary colors
    • ☼A long weenie is hard and red (skin color), a medium (normal) weenie is yellow (skin color), a cold weenie is short n blue (skin color)
  142. retinal
    • a chemical made from Vit A
    • changes shape when struck by light
  143. opsin
    a protein which joins retinal in rods
  144. rhodopsin
    • the combination of retinal + opsin
    • the visual transducer in rods
    • *cones have a similar combination of retinal + cone opsin
  145. What happens when light hits rhodopsin (retinal + opsin)
    • Causes change in Na+ channels
    • In darkness, open Na+ channels keep rod depolarized
    • Glutamate is neurotransmitter, more glutamate is released in dark
    • When light hits eye, Photons cause Na+ channels to close
    • This hyperpolarized rod (more negative cause loss of + ion flow into rod)
    • Glutamate release is turned off in light
  146. Visual pathways to brain. Leaving eye
    • *job of these pathways is to move SOME info from left side of world to right side of brain
    • Visual info leaves retina on ganglion cell axons, which forms CR II (optic nerve)
  147. Why is SOME if the info from one eye transferred to the other part of brain?
    • Since both eyes have access to both the left and right side of the world, gotta split the info from one eye (for example, the info the R eye picked up of the L side of the world) send that info to left side of brain to process
    • Switches at optic chiasm
  148. Visual pathway for left side of world to brain
    • Photons from LEFT side of the world hit left retina nearest nose, and right retina nearest temples. 
    • The axons from these areas join together at optic chiasm and form the right optic tract
    • The right optic tract ends on right side of thalamus, which sends axon through to optic radiations in right visual cortex in occipital lobe
  149. Visual pathway for right side of world to brain
    • Photons from RIGHT side of world hit the right retina nearest the nose and hit the left retina nearest the temples
    • The axons from these areas join together at the optic chiasm and for the left optic tract
    • The left optic tract ends on Left side of thalamus, which sends axons through left optic radiations to left visual cortex in occipital lobe
  150. olfaction
    the sense of smell
  151. olfactory receptors
    • found on superior surface of nasal sinuses
    • the olfactory receptor sheet in humans is about the size of a postage stamp
  152. odorants
    small molecules, carried by air, that are dissolved in mucus layer that covers the olfactory epithelium
  153. olfactory transduction
    • depends on a G protein pathway
    • Olfactory cells have cilia w protein receptor molecules that specifically bind a certain type of odorant
    • When an odorant binds to a olfactory receptor, it triggers the G protein biochemical pathway
  154. Olfactory pathways to brain
    after olfactory stimulus is analyzed by olfactory receptor, signal is passed via olfactory nerve through ethmoid bone to the olfactory bulb, which processes  the signal further, and then transfers signal via the olfactory tract to olfactory cortex in temporal lobe

    *This pathway is the only sensory pathway that IS NOT relayed through the thalamus - giving smells direct access to emotional centers in the brain)
  155. anosmia
    • a condition when a pt permanently loses the sense of smell
    • happens when the delicate nerve axons which pass through the cribriform plate of the ethmoid bone are torn by head trauma
  156. gustation
    • sense of taste
    • *taste and smell work together and are hard to separate
  157. 5 types of taste receptors (therefore, 5 primary tastes)
    • sweet
    • salty
    • bitter
    • acid
    • umami
    • *most taste receptors are found on tongue, but also found on lips, soft palate, and oropharynx
  158. Distribution of taste receptors
    • Receptors for things we "want" (sweet, salty) tend to be closer to front
    • Receptors for things we don't want tend to be closer to back (bitter, acid = gag)
  159. Taste "index" for sweet and salty
    • Sweet = sucrose (table sugar) in water
    • Salty = NaCl (table salt) in water
  160. Taste "index" for bitter and acid
    • Bitter = represented by quinine (as in tonic water)
    • Acid = measures concentration of H+ ions (pH)
  161. Umani
    • 5th primary taste
    • "tasty" or "meaty"
    • index taste of monosodium glutamate
  162. Filiform papillae
    • bumps, covers most of tongue surface
    • do not have any taste function
  163. taste buds
    • where gustatory receptor cells are clustered
    • scattered over the surface of oral cavity, but are found on tongue in three groupings
  164. Three groupings of taste buds found on tongue
    • Fungiform papillae
    • Foliate papillae
    • Vallate (or circumvallate) papillae
  165. Fungiform papillae
    • one  of 3 groups of taste buds on the tongue
    • look like little muschrooms
  166. Foliate papillae
    • one of 3 groups of taste buds on tongue
    • leaf-shaped; found along lateral surface of the posterior tongue
  167. Vallate papillae
    • or circumvallate papillae
    • form a V-shaped row along posterior tongue
    • usually 7 - 12 of these
  168. What 3 cranial nerves are involved with taste info & what area do they innervate?
    • CN VII (facial nerve)  - anterior 2/3 of tongue
    • CN IX (glossopharyngeal nerve) - posterior 1/3 of tongue
    • CN X (Vagus) - info from tonsils, palate, and oropharynx. *remember receptors for noxious chemicals most likely found here. Activation of Vagus likely to trigger gag reflex; damage to Vagus suppresses this reflex
  169. chorda tympani
    • a bundle of axons resulting from the combining of CR VII, CN IX, and CN X
    • carries information to the medulla
  170. What other CN have some authorities included in the CN's involved with taste info
    • CN V - trigeminal
    • stimulation of pain receptors by capsaicin produces a pain response, and the subsequent release of endogenous opiates
    • *this is why some people find spicy food pleasurable
  171. capsaicin
    • a chemical found in hot peppers, which stimulates pain receptors in CN V
    • this produces the pain response and release of opiates
  172. Gustatory Pathways to brain
    • Gustatory = sense of taste
    • 3 cranial nerves carry taste sensations to the medulla, which relays these sensations to the thalamus, which then sends the info to the primary gustatory cortex in the mouth area of the postcentral gyrus
  173. auditory sense
    • hearing (duh)
    • depends on the ear receiving pressure waves of air
  174. auricle
    • also called pinna
    • the external part of ear
    • collects and carries sound to external auditory meatus (canal) which directs the sound waves to tympanic membrane ("eardrum")
  175. tympanic membrane
    • eardrum
    • sound waves cause it to vibrate, which in turn causes the malleus to vibrate
  176. The auditory ossicles
    • Bones of the ear: 
    • Malleus - (the hammer) is vibrated by tympanic membrane
    • Incus - (the anvil) Hammer "hammers" on anvil. The incus has a lever on it which then moves the Stapes
    • Stapes (looks like stirrup) - hooks to oval window of cochlea
    • transmit and amplify vibrations from tympanic membrane to oval window
    • *the CN VII (facial) runs near the ossicles: can be damaged by middle in infections or surgery
  177. Inner ear structures
    • semicircular canals (balance)
    • cochlea (hearing)
  178. cochlea
    • a spiral-shaped structure which contains the spiral organ
    • has two fluid filled chambers: scala tympani and scala vestibuli
    • The fluid in these spaces are moved when the ossicles transmit energy from the tympanic membrane to the oval window
  179. organ of Corti
    • also called spiral organ
    • contained within the cochlea which is where auditory transduction occurs
    • Lays btwn the scala vestibuli (top) & scala tympani (bottom)
  180. basilar membrane
    • at the base of spiral organ, used in auditory transduction
    • *As the fluid within the spiral organ sloshes about, the membrane is pushed up and down in waves (these waves matching the frequency of pressure waves of air which reached ear) As this bobs up & down, cilia (hair) are bent back and forth against the tectorial membrane
  181. tectorial membrane
    • a flexible membrane which covers the hair cells of the spiral organ
    • When fluid makes the basilar membrane move, it moves the hair cells back and forth - this causes auditory transduction
  182. hair cells
    • auditory receptors cells which shift against tectorial membrane
    • Don't have axons... they synapse right away, which releases a neurotransmitter, on afferents whose cell body is in spiral ganglion and axons form the cochlear branch of the CN VIII (vestibulocochlear nerve)
    • In a single section of the spiral organ, there are usually 3 outer hair cells and 1 inner hair cell
  183. 2 accessory ear structures:
    ceruminous glands and auditory tube
  184. ceruminous glands
    • produce cerumen
    • line external auditory canal
  185. cerumen
    • ear wax
    • the waxy substance found within ear, helps trap dirt and insects
    • can even produce a protective earplug if ear is exposed to loud noises
  186. Eustachian tube
    • now called the auditory tube
    • doesn't directly aid w hearing, rather it connects the middle ear to nasopharynx
    • equalized the pressure on both sides of tympanic membrane unless tube becomes swollen or clogged w mucus
    • If tube is not patent (open), pressure builds and causes pain (released by "popping" ears)
  187. What CN in involved with hearing?
    • CN 8: vestibulocochlear nerve
    • Vestibular branch comes from the semicircular canal & deals with balance
    • Cochlear branch carries sound info to brain from cochlea
  188. sound conduction pathway:
    • 1 waves of air arrive in external auditory canal
    • 2 air moves tympanic membrane
    • 3 tympanic membrane moves ossicles (malleus bangs on incus, incus moves causing the stapes to move)
    • 4 Stapes moves oval window
    • 5 Oval window moves perilymph fluid in scala vestibuli
    • 6 Waves of fluid in scala vestibuli set up vibrations in basilar membrane, which moves hair cells
    • 7 Fluid can pass from scala vestibuli to scala tympani at helicotrema 
    • 8. Fluid in scala tympani
    • Round window is outlet for pressure
  189. helicotrema
    • the "u-turn" of the spiral organ
    • where the scala vestibuli becomes the scala tympani
  190. Pitch
    • is the frequency (interchangeable with wavelength) of sound waves 
    • *refers to the length between two "peaks" in the wave
    • measured in waves per second - Hertz (Hz)
    • the basilar membrane is "tuned" to vibrate the most at a certain frequency
    • -near helicotrema: low pitch - long wave length
    • -near oval window: high pitch - short wave length
  191. amplitude =
  192. What frequencies are outside the range of human hearing
    below 20 Hz and above 20,000 Hz
  193. place coding
    • refers to the fact that a particular place on the basilar membrane codes for a particular note/pitch/frequency, 
    • therefore, it's called "place coding" cause a place on the B membrane codes for each pitch
  194. Auditory pathways to brain
    • cranial nerve VIII
    • medulla
    • thalamus
    • Auditory cortices in temporal lobe
  195. superior olivary nucleus (superior olive)
    • located in the medulla
    • only place in brain that calculated the location of sounds
    • microsecond differences in the arrival of sound btwn the 2 ears are used to determine the source of sounds
  196. vestibular sense
    • sense of balance
    • balance depends on knowing where our bodies lie in relationship to gravity
    • two important features of that relationship that must be calculated: 
    • static equilibrium
    • dynamic equilibrium
  197. static equilibrium
    • used to measure the tilt of the heat, either side to side or front to back
    • referred to as linear acceleration by engineers
  198. dynamic equilibrium
    • used to measure head rotation or movement
    • called angular acceleration by engineers
  199. Maculae
    • the receptive organs which code for static equilibrium (head tilt)
    • found in utricle and saccule
    • contain hair cells which closely resemble those found in chochlea
  200. Utricle and saccule
    • "leather bag" and "little sack"
    • are the two enlargements at the junction btwn semicircular canals and cochlea
    • codes for Static equilibrium
    • like spiral organ, these also contain hair which are embedded in Otolith membrane with otoliths on top
    • "land slide"
  201. otolith membrane
    • a gelatin-like membrane where the cilia of macular hair cells are embedded
    • have otoliths on top like sprinkles of a frosted donut
  202. otholiths
    • "ear rocks"
    • crystals of calcium carbonate which slide on top of hairs and move them to and fro
    • As head tilts, otoliths slide & bends cilia, which causes ion channels to open and set up the potential changes that alter neurotransmitter release onto the primary afferent fiber
  203. Ampullae of the semicircular canals
    • Codes for Dynamic Equilibrium/angular acceleration (head rotation)
    • 3 semicircular canals/ 1 for each plane
    • As head swivels, fluid in semicircular canals sloshes around and activates ampullae (one on each canal)
  204. ampulla
    • located at the end of each semicircular canal
    • contains hair cells
    • as head swivels, fluid in s. canals sloshes and activates the hair cells
  205. roll, pitch, and yaw
    • what pilots call the X, Y, and Z axes
    • each semicircular canal is in an optimal position to detect movement in one of three cardinal planes
  206. compensatory eye movement
    • if the head rotates to the left, the eyes move right
    • in this way, the eyes stay fixed on one point in space
  207. nystagmus
    • a characteristic flickering movement pattern of the eyes is something unusual happens in vestibular system (like spinning on a barstool, or damage to vestibular division of vestibulocochlear nerve)
    • Is a sign of damage to vestibular nerve on one side, or a tumor of the nerve on one side
  208. pathways taken for vestibular sensation info from semicircular canals to brain
    • the vestibular system makes an important contribution to the sense of balance and body position in space (proprioception)
    • There is integration w other somatic senses:
    • -cell bodies of afferents in vestibular ganglion, whose axons form the vestibular division of CN8
    • -4 vestibular nuclei in pons and medulla
    • -relay in ventral posterior nucleus of thalamus
    • -cortical representation in somatosensory cortex
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hths Mod 13
2014-02-08 19:42:26
HTHS Mod 13

HTHS Mod 13
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