med phys e3

Question 1

somesthetic receptor

Answer 1

• aka somatosensory
• a sensory end organ concerned with reception of stimuli producing one of the generalized sensations such as temp, pressure, position or movement

Question 2

sensation

Answer 2

• signals transmitted by receptors to brain in form of light, sound, tactile, thermal, pain, etc
• receptors respond specifically to one form of energy more than any other but may respond to other forms (photoreceptors may respond to pressure; we might see “stars”
• unconscious processing/at subcortical level
• ex. nociception is sensation; pain is perception

Question 3

perception

Answer 3

• refers to how sensory information is organized, interpreted and consciously experienced
• conscious processing/at cortical level
• ex. nociception is sensation; pain is perception

Question 4

Meissner’s corpuscles

Answer 4

• mechanoreceptors present in highly sensitive areas like fingertips, palms, soles, tongue, lips & genital skin
• have small receptive fields to allow two-point discrimination
• respond to low frequency stimuli (flutter)

Question 5

Pacinian corpuscles

Answer 5

rapidly adapting mechanoreceptors for pressure and vibration

Question 6

Merkel’s disks

Answer 6

slow adapting mechanoreceptor that respond to pressure and touch

Question 7

hair follicle receptors

Answer 7

rapidly adapting mechanoreceptors that respond to movement across surface of skin

Question 8

Ruffini’s corpuscles

Answer 8

slow adapting mechanoreceptors that respond to stretch found in dermis & joints

Question 9

thermal receptors

Answer 9

• free nerve endings that respond to temp changes

- divided in cold and warm slow adapting receptors

Question 10

nociceptors

Answer 10

• free nerve endings found in skin, muscle, joints, periosteum and visceral organs capsules
• respond to noxious (harmful/unpleasant) chemicals, mechanical stimuli (stretch) and temp

Question 11

muscle spindles (in muscles) and golgi tendon (in tendons)

Answer 11

• important in proprioception & coordination of motor activity

Question 12

sensory receptive fields

Answer 12

• region of skin that elicits a response in somatic sensory neuron (2 pt discrimination)
• vary in diameter (1-2 mm on fingertips [high precision]; 5-10 mm on palms; larger in abd & back [lower precision]) and may overlap

Question 13

ascending (afferent) tracts - anterior column

Answer 13

ventral spinothalamic tract (pressure and crude touch - can’t localize)

Question 14

ascending (afferent) tracts - lateral column

Answer 14

lateral spinothalamic tract (pain and temperature); ventral & dorsal spinocerebellar tracts

Question 15

ascending (afferent) tracts - posterior column

Answer 15

fasciculus cuneatus & gracilis (vibration, proprioception, fine touch - can localize)

Question 16

descending (efferent) tracts - anterior column

Answer 16

ventral corticospinal/pyramidal tract (voluntary mvoements, reflexes)

Question 17

descending (efferent) tracts - lateral column

Answer 17

lateral corticospinal/pyramidal tract (voluntary movements, reflexes)

Question 18

thalamus

Answer 18

• awareness of nociceptive stimuli (non-discriminative form)
• subjective response to sensation
• activation and arousal with reticular formation
• modification of affective component of behavior with limbic system

Question 19

reticular formation

Answer 19

• network of neurons located throughout brainstem
• reticular activating system (RAS)
• conscious awareness and behavioral responses to stimuli
• maintain wakefulness
• muscle tone & posture
• respiratory centers (rhythm, depth, pattern)
• BP, CO & blood distribution to organs

Question 20

limbic system

Answer 20

• hippocampus, amygdala, anterior thalamic nuclei, limbic cortex
• emotion, behavior and long term memory

Question 21

wernicke’s area

Answer 21

comprehension of written and spoken language

Question 22

broca’s area

Answer 22

production of language

Question 23

somatosensory cortex

Answer 23

part of brain in parietal lobe that processes sensation

• somatic sensory cortex (sensory homunculus, skin sensation, proprioception, stereognosis, integrates info w/ visual & auditory signals)
• sensory association area (complex sensory information processing, spatial relationships, two-point discrimination, graphesthesia)

Question 24

stereognosis

Answer 24

mental perception of depth or 3D by senses, usually in reference to ability to perceive form of solid objects by touch

Question 25

graphesthesia/graphagnosia

Answer 25

ability to recognize symbols when they're traced on skin

Question 26

pain

Answer 26

free nerve endings detect damage to tissues - group A fibers (bigger) = sharp, shooting, intense pain - group C fibers (smaller) = steady, slow, constant pain - visceral pain = produced by distension, spasm, contraction, torsion, ischemia, chemical irritation or inflammation of viscera

Question 27

ascending pain pathways

Answer 27

- spino-thalamic-somatosensory cortex = sensation of pain | - spino-thalamic-frontal cortex/anterior cingulate gyrus = subjective psychological and physiological effects of pain

Question 28

descending pain pathways

Answer 28

- inhibitory fibers modulate pain sensation (gate control) - modulation by fibers from periaqueductal grey matter, nucleus raphe & RF to dorsal horn - neurotransmitters - Serotonin, Adrenaline, GABA, Endorphins (opioids)

Question 29

gate control theory of pain

Answer 29

- explains how non-painful sensation can override & reduce painful sensations - substantia gelatinosa at tip of dorsal horn - gate controlling - painful, nociceptive sitmulus stimulates primary afferent fibers → to brain via transmission cells → increased perceived pain

Question 30

therapeutic use of gate control theory

Answer 30

- pain is lessened when area is rubbed because activation of non-nociceptive fibers inhibits firing of nociceptive one - transcutaneous nerve stimulation (TENS): use of electrodes to selectively stimulate non-nociceptive fibers to lessen pain - stimulation of central areas (periaqueductal grey matter) produces analgesia (not total numbness) by activating descending pathways (opioid neurons in spinal cord)

Question 31

referred pain

Answer 31

- brain is unable to distinguish visceral signals from more common signals that arise from somatic receptors - theories - --- nociceptive sensory fibers from different viscera (pericardium) can use same set of 2nd order neurons (neck, arm, jaw muscles) - --- visceral nociceptors may activate somatic nociceptive 2nd order neurons

Question 32

hyperalgesia

Answer 32

- enhanced sensitivity and responsivity to stimulation of area around damaged tissue that may be caused by sensitization of nociceptors (lower threshold to respond) - sensitization to local signals (prostaglandins, leukotrienes from damaged cells, substance P from afferent nerve fibers, etc)

Question 33

taste

Answer 33

- mediated by taste receptor cells (rapidly adapting) which are bundled in clusters called taste buds within tongue papillae - food MUST BE DISSOLVED IN SALIVA to reach receptors - taste sensation can change according to body's specific nutritional needs

Question 34

taste modalities and how taste gets in

Answer 34

- taste ligands (molecules) dissolve in saliva → reach taste pores (surrounded by taste hairs) → bind to chemoreceptors on taste buds → receptor-ligand interaction increases intracellular calcium → release of NT → graded potentials → AP in sensory neurons - sweet = sugars; G protein, coupled - bitter = alkaloids; G protein, coupled - sour = H+; ion channel - salty = Na+; ion channel - umami = glutamate; both

Question 35

anterior 2/3rd of tongue nerve innervation

Answer 35

- trigeminal nerve (CN V) = somatosensation (touch, pain, pressure) - facial nerve (CN VII) = taste sensation

Question 36

posterior 1/3rd of tongue nerve innervation

Answer 36

- glossopharyngeal nerve (CN IX) = taste and somatosensation

Question 37

root of tongue nerve innervation

Answer 37

- vagus nerve (CN X)

Question 38

how smell gets in

Answer 38

- odorant molecules bind to G protein coupled receptors on cilia of olfactory neurons → activation triggers graded potential → AP → signal to olfactory cortex - molecules MUST BE DISSOLVED IN MUCUS to activate receptors - -- proteins in mucus help keep it dissolved & transport odorants to olfactory dendrites - axons from olfactory bulb project to limbic cortex, amygdala, hippocampus (temporal lobe - long term memory formation) - NO THALAMUS - intimate connection w/ brain cortex & reticular formation - smell neurons replaced every 60 days

Question 39

structures involved in olfaction

Answer 39

- olfactory bulb contains mitral cells that receive info from olfactory cells - olfactory cells found within nasal epithelium & pass their info thru cribriform plate of ethmoid bone

Question 40

how light gets in

Answer 40

- light detected by retina receptors (cones and rods) → retina changes shape → activating photopigment, rhodopsin → if light, present → rods & and cones hyperpolarize → activate neurons → stimulate ganglion cells which sent APs via optic nerve to lateral geniculate nucleus (thalamus) → visual cortex in occipital lobe - if light is not present, neurons are inhibited by rods and cones - horizontal cells can create lateral inhibition, which enhances light & dark contrast in images - tonic activity - when photoreceptors become slightly active even when not stimulated by light - rhodopsin - a light-sensitive pigment in rod cells of retina; consists of opsin protein bound to carotenoid retinal

Question 41

visual system

Answer 41

- higher cortical areas process & integrate visual inputs, supporting coherent visual perception what & where (retinal sensation/image converted to our personal view/percept of outside world) - optic nerve can be considered part of CNS (axons have oligodendrocytes & surrounded by meninges) - macula - part of retina where we process a high-definition visual information (shapes, colors)

Question 42

anatomical structures involved in visual system

Answer 42

- cornea & lens - bend to focus image on retina - iris & pupil - regulate amount of light entering eye - aqueous humor - maintains convex shape of cornea - vitreous humor - supports lens & maintains shape of entire eye - presbyopia occurs because image focuses behind retina - -- hyperopia (farsightedness) = eyeball that is too short - -- myopia (nearsightedness) = eyeball is elongated - rods - rod-shaped cell located in outer retina of eye that is sensitive to light; used for peripheral and nighttime vision - retina - thin layer of cells at back of eyeball where light is converted into neural signals sent to brain - cone - cell located near center of retina that is weakly photosensitive & is responsible for color vision in relatively bright light; used for daytime and color vision - fovea - acute vision because it has high density of cones

Question 43

retinal receptors

Answer 43

Rods: high sensitivity to light, and scattered light, specialized in night vision, more sensitivity to movement, low resolution, monochromatic Cones: low sensitivity to light, more sensitive to direct light rays, high acuity, concentrated in fovea, polychromatic (3 types of cones)

Question 44

types of cones

Answer 44

- trichromatic system - color is a result of ratio of activity of three types of cones - S cones = respond to short waves - M cones = respond to medium waves - L cones = respond to light to long waves

Question 45

fovea

Answer 45

- special area where cells are displaced to allow light to be directly absorbed - focal point of image & region where most cone cells are concentrated - constantly move our eyes to view the foveal image - at optic dis, fibers leave the eye - no photoreceptors here (blind spot)