A&P Chapter 16: Sense Organs

Nature of sound

* sound is audible vibration of molecules -loudness (decibals) -Pitch: frequency (Hz)

Referred Pain

*Misinterpreted pain: -brain "assumes" visceral pain is coming from skin -heart pain felt in should or arm because both send pain to spinal cord segments (during heart attack)

Dark adaptation

*turns lights off -dialation of pupils occurs -20 to 30 minutes required for regeneration of rhodopsin

Light adaptation

*walk out into sunlight -pupil constriction and pain from over stimulated retinas -color vision and acuity below normal for 5-10 minutes

Inner Ear

-Cochlear duct: endolymph -Scala duct: perilymph

Spiral Organ

-Contains hair cells (mechanoreceptors for hearing)

Distribution

-General senses: employ widely distributed receptors in the skin, muscles, tendons, joints, and viscera. These include touch, pressure, stretch, heat, cold, and pain, as well as many stimuli that we do not perceive consciously, such as blood pressure and composition. Their receptors are relatively simple. -Special senses: are limited to the head, are innervated by the cranial nerves, and employ relatively complex sense organs. The special senses are hearing, equilibrium, taste and smell.

Pain

-Nociceptors: allow awareness of tissue injuries (found in all tissues except the brain) *injured tissues release chemicals that stimulate pain fibers (bradykinin, histamine, prostaglandin)

Chemical Sense of Smell

-Olfaction: sense of smell *chemoreceptors (olfactory cells) in mucous membranes on roof of nasal cavity *olfactory glands produce moist mucous coating to dissolve chemicals *much more sensitive than those in taste buds

Vision (key points)

-Phototransduction: transforming light -> electrical signal -photoreceptors at back of retina. connected serially go bipolar and ganglion cells -fovea: part of retina, for high acuity vision (high density of photoreceptors) -ganglion cell- axons from optic nerve. visual info leaves retina through ganglion cells

Sense Organs

-Sensory systems: converting energy into information --organisms must be able to detect various forms of environmental energy for survival *forms of energy detected by humans: sound waves, light, mechanical, chemical, (magnetic waves- no scientific evidence)

fovea centralis

-The center of macula; finely detailed images due to packed receptor cells

Stimulus Modality

-Thermoreceptors: respond to heat and cold. -Photoreceptors: the eyes, respond to light. -Nociceptors: are pain receptors (they respond to tissue injury or situations that threaten to damage a tissue) -Chemoreceptor: respond to chemicals, including odors, tastes, and body fluid composition. -mechanoreceptors: respond to physical deformation of a cell or tissue cause by vibration, touch, pressure, stretch, or tension. They include the organs of hearing and balance and many receptors of the skin, viscera, and joints.

Fungiform papillae

-are shaped like mushrooms -each contain about three taste buds -located mainly on the tip and sides of tongue *taste salty, sweet, and sour

retina

-attached at the optic disc (blind spot) and ora serrate --pressed against rear of eyeball by vitreous humor

Taste (gustation)

-begins with the chemical stimulation of sensory cells clustered in about 4,000 taste buds. The chemical stimuli are called tastants.

Detached retina

-blow to head to lack of vitreous -blurry areas in field of vision -disrupts blood supply, leads to blindness

Macula lutea

-cells on visual axis of eye -direct evaluation of blood vessels

cataract

-clouding of the lens *causes: aging, diabetes, smoking, UV light

Outer segment of rods and cones

-contains light transducting apparatus -disks contain light absorbing pigment (photopigment) *disks capture light and transform -> electrical signals

Inner segment of rods and cones

-contains the cell body, mitochondria, and nucleus *function: biosynthesis (proteins, ATP, etc.)

Cones

-day vision, sense bright light *color vision

glaucoma

-death of retinal cells due to elevated pressure within the eye --colored halos and dimness of vision

Angular acceleration

-detected by semicircular ducts 2. Rotational head movement ex. spinning around

Linear acceleration

-detected by vestibule 1. Linear acceleration forces -ex. jumping up or down move back and forward move side to side

Static Equilibrium

-detects body (head) position -also detected by vestibule

Eyebrow

-enhance facial expression and nonverbal communication, may also protect the eyes from glare and keep perspiration from running into eye

Origin of Stimuli

-exteroceptors: sense stimuli external to the body. They include the receptors for vision, hearing, taste, smell, and cutaneous sensations such as touch, heat, cold, and pain. -interoceptors: detect stimuli in the internal organs such as the stomach, intestines, and bladder, and produce feelings of stretch, pressure, visceral pain, and nausea. -proprioceptors: sense the position and movements of the body or its parts. They occur in muscles, tendons, and joint capsules.

Tarsal plate

-extra protection, resistant medium

Palpebrae

-eyelashes -block foreign objects from eye, prevent visual stimuli from disturbing one's sleep, and blink periodically to moisten the eye with tears and sweep debris from surface.

Foliate Papillae

-form parallel ridges on the sides of tongue about 2/3 of the way back from the tip

Color blindness

-heredity lack of one photopsin -- red-green is common (lack either red or green cones) *incapable of distinguishing red from green *sex-linked recessive (8% of males)

CNS modulation of pain

-intensity of pain: affected by state of mind (mediation can help make migraine less painful) -endogenous opiods (enkephalins, endorphins, and dynorphins) -- produced by CNS and other organs under stress --indorsal horn of spinal cord (spinal gating) --act as neuromodulators to block transmission of pain

Conductive deafness

-interferes with transmission of sound waves to inner ear *damage to eardrum *blockage of auditory canal *fusion of ossicles

Vallate papillae

-large bumps at the back of the tongue, arranged in a V -each is surrounded by a deep circular trench. -contain up to half of all taste buds *taste bitter

Sensorineural deafness

-loss of hair cells -damage to vestibulocochlear (auditory) nerve

Physiology of Taste

-molecules must dissolve in saliva *five primary sensations throughout tongue: 1. sweet: concentrated at tip 2. Salty: lateral margins 3. Sour: lateral margins 4. Bitter: posterior 5. umami: taste of amino acids (MSG) -influenced by foot texture, aroma, temperature, and appearance -No receptor for spicy-> hot pepper stimulates free nerve endings (pain)

Rods

-night vision, sense dim light *achromatic (black and white)

Filiform Papillae

-not actually taste buds *mechoreceptors-> sense texture -- dispersed all over, but they are more dense at the tip of the tongue

Anatomy of Smell

-olfactory epithelial cells -olfactory hair cells (20 cilia per cell) -glomerulus: each one is different, they smell something unique (most smells are a combination) -Nerve cells: live 60 days (must be replaced because they are so exposed) *nerve cells are replaced by basal cells *supporting cells (provide nerve cells with energy) -Brain can send signals back (turn signals up or down) --pregnant women have sensitive smell --when sick have little or no smell

Olfactory Pathway

-output from bulb forms olfactory tracts --end in primary olfactory cortex and thalamus --identify odors --integrate taste and smell into flavor --travel to hippocampus, amygdala, and hypothalamus *memories, emotional and visceral reactions

Somatic pain

-pain from skin, muscles, and joints

Vision and light

-see electromagnetic energy --visible light (in wavelength) **humans can only see a small range

Gustation

-sensation of taste -chemical receptors within taste buds on tongue -some mechanoreceptors for texture

Brain is hard wired for sensory info

-sensory neuron must transmit information to the brain -brain must interpret incoming sensory information -brain is hard wired -sensory maps

Properties of receptors

-sensory transduction: converts stimulus energy into nerve energy -receptor potential: local electrical charge in receptor cell -adaptation: conscious sensation declines with continued stimulation

Conjunctiva

-transparent mucous membrane over top of sclera, secretes mucous -has tons of nerves (this is what hurts when you feel pain in the eye) -blood vessels *pink eye-> conjunctivitis

Fast Pain

-travels in myelinated fibers at 30 m/s *sharp, localized, stabbing pain perceived with injury

Slow pain

-travels unmyelinated fibers at 2 m/s *longer lasting, dull, diffuse feeling

Receptors transmit 4 kinds of information

1. Modality: refers to the type of stimulus or sensation it produces. (ex. vision, hearing, and taste are examples of sensory modalities) 2. Location: encoded by which nerve fivers issue signals to the brain. -each sensory receptor receives input from its receptive field -sensory projection: brain identifies site of stimulation *in a sense of touch, a single sensory neuron may cover many cover an area of skin as large as 7 cm in diameter. No matter where the skin is touched within that receptive field, it stimulates the same neuron. The brain may be unable to determine whether the skin was touched at point a or some other point 1.5 cm away. 3. Intensity: refers to whether a sound is loud or soft, a light is bright or dim, a pain is mild or excruciating. --frequency, number of fibers, and which fibers (weak stimuli activate only the most sensitive nerve fibers, whereas strong stimuli can activate a less sensitive group of fibers) 4.Duration: how long a stimulus lasts, encoded by changes in firing frequency over time. -phasic receptor: generate a burst of action potentials when first stimulated, then quickly adapt and sharply reduce or stop signaling even if the stimulus continues. (ex. smell and hair receptors) -tonic receptor: adapt more slowly and generate signals more steadily. (proprioceptors- are among the most slowly adapting tonic receptors because the brain must always be aware of body position, muscle tension, and joint motion)

Transmission of Sound

1. Sound -> airwaves arrive at tympanic membrane 2. Vibration of tympanic membrane causes the ossicles to vibrate 3. Movement of stapes at oval window-> creates pressure waves in perilymph of vestibular duct 4. Waves distort "wiggle" basilar membrane on way to round window of tympanic duct 5. Vibration of basilar membrane -> vibration of hair cells against tectorial membrane (stiff) 6. Info about region and intensity of stimulation is relayed to CNS via cochlear branch of Nerve 8

Ways to classify receptors

1. Stimulus Modality: what we perceive after a stimulus. 2. Origin of the stimulus: location 3. Distribution: of receptors in the body

Sensory receptors

Nerve cells detect and transmit info. -axon with cell body in dorsal root ganglion with end going into CNS -

Ear structure

Outer Ear: -Pinna or Auricle -Auditory canal (auditory meatus) ear through to the skull -tympanic membrane (ear drum) sound waves hit and it vibrates Middle Ear -Auditory ossicles (ear bones) *malleus *incus *stapes (plugs oval window, pulls fluid) Inner Ear: -oral window *cochlea

dynamic equilibrium

Perception of motion or acceleration

Ears

Two special senses: -hearing (sound waves) -equilibrium (gravity) which way is down *both involve mechanoreceptors called hair cells

Lingual papillae

Visual bumps on the tongue (not taste buds) There are four types: 1. Filiform 2. Foliate 3. Fungiform 4. Vallate

Visceral pain

pain from stretch, chemical irritants or ischemia ( poorly localized) (lack of oxygen)

Static equilibrium

perception of the orientation of the head when body is stationary