BIO Ch. 17 Sensory Organs Flashcards
Sensory Receptor Adaptation
Receptor potential decreases over time > decrease rate of impulse conduction & intensity of sensation
Receptor Classification (by location)
Exteroceptors (cutaneous): on/near body surface- touch/pressure/pain
Interoceptors (visceroceptors): within body organs- pressure, stretch, hunger, thirst
Proprioceptors (type of visceroceptors): skeletal m, joints, tendons
- info on movement, stretch, orientation
- Tonic/Phasic
Receptor Classification (by stimulus detected)
Mechanoreceptors: activated when “deformed” to generate receptor potential
Chemoreceptors: activated by amount or changing concentration of certain chemicals (e.g., taste and smell)
Thermoreceptors: activated by changes in temperature
Nociceptors: activated by intense stimuli that may damage tissue (pain sensation)
Photoreceptors: found only in the eye; respond to light stimuli if the intensity is great enough
Osmoreceptors: hypothalamus; activated by changes in concentration of electrolytes (osmolarity) in extracellular fluids
Receptor Classification (by structure)
Free nerve endings
- Most widely distributed
- exteroceptors and visceroceptors
- Include pain, temperature and tactile
receptors
- Terminate in “free” dendritic knobs
Encapsulated nerve endings
- Connective tissue capsule surrounds their
terminal dendritic end
- Primary mechanoreceptors
Encapsulated Nerve Endings (6)
Mechanoreceptors (touch/pressure)
- (1) Tactile corpuscle (Meissner corpuscle):
touch, texture, and low-frequency
vibration
-(2) Bulboid corpuscles
-(3) Bulbous (Ruffini) corpuscles
- (4) Lamellar or Pacini corpuscles: deep
pressure, high-frequency vibration
Stretch Receptors
- (5) Muscle Spindles
- (6) Golgi Tendon Receptors
Stretch Receptors
Stretch receptors: operate to provide body with information concerning muscle length and strength of muscle contraction
- Muscle Spindle
- Golgi Tendon Organs
Muscle spindle (proprioceptors)
“Stretch”=Spindle
Parallel to regular m fibers
Carry messages to brain concerning changes in m length
Stretch reflex is initiated to shorten the m if it exceeds certain limits
Golgi tendon organs
Between muscle tissue and tendon
“Going the distance, length”=Golgi
Stimulated by excessive stretch of a tendon caused by excessive contraction of a m
They cause m to relax = protects m tears
Olfactory Sensory Neurons
Chemoreceptors
Extremely sensitive, but adapt easily /rapidly
Taste Buds
Chemoreceptors
Respond to gustatory (taste) stimuli; associated with papillae
Highly sensitive but adapt quickly
External Ear Structures
Divisions:
- Auricle (pinna) - visible portion of ear
- External Acoustic Meatus - tube
Middle Ear Structures
Ossicles (bones) - "MIS"
- Malleus (hammer): attach to tympani memb
- Incus (anvil): attach to malleus/stapes
- Spates (stirrup): attach to incus
Openings
- Oval window: stapes fits here
- Round window
- Opening to Auditory Tube (Eustachian
pressure equalization)Inner Ear Structures
Bony labyrinth: composed of the vestibule, cochlea, and semicircular canals
Membranous labyrinth
- saccule/cochlear ducts/membranous
semicircular ducts
Vestibule/semicircular canal organs (balance)
Cochlea: hearing
Sense of Hearing
Hair cells must be stimulated (pitch) enough to perceive sound via cochlear portion of CN VIII (vestibulochoclear)
High frequency - Oval Window
- “high office is the Oval office”=High=Oval
Low frequency - Cochlea
- “You are in a low state if you do
coke”=Low=Cochlea
Cochlear Duct Structures
Only part of inner concerned with hearing
Vestibular membrane: the roof
Organ of Corti (spiral organ): rests on the basilar membrane; consists hair cells
Basilar (spiral) membrane: the floor
Pathway of Sound Waves
Enter external auditory canal > tympanic memb (vibrations) > moves malleus/incus/stapes > oval window (fluid conduction of waves) > cochlea (vestibular memb/basilar memb/organ of corti) >against round window
Neural Pathway of Hearing
Choclear n impulse > brainstem > nuclei relay in the medulla,pons,midbrain, thalamus > auditory are of temporal lobe
Sense of Balance
Static equilibrium: ability to sense head position relative to gravity or acceleration/deceleration
- Static = Saccule/utricle
Dynamic equilibrium: maintain balance when the head/body is rotated/moved; detect changes in direction and rate of movement
- dynamic = circular cage = semicurcular
ducts
Static Equilibrium
Macula: contain hair cells that move by pressure (information of head position/acceleration to CNS)
Otoliths “ear crystals” within the matrix of the macula
Righting reflexes: m responses to restore normal body positioning
- stimulated by macula/proprioceptors/eyes
Dynamic Equilibrium
Depends on cristae ampullaris (containing hair cells): doesn’t respond to gravity
Muscles of the Eye
Extrinsic eye mm (voluntary): skeletal mm that attach to the outside of the eyeball and bones of the orbit
- the superior, inferior, medial, and lateral
rectus mm and superior and inferior
oblique mm
Intrinsic eye mm: smooth mm (involuntary) located within the eye
- iris (pupil size)
- ciliary mm (shape of lens)
Structural Layers of the Eyeball (3)
Fibrous Layer (outer coat) Vascular Layer (middle coat) Inner Layer (incomplete innermost coat)
Fibrous Layer of the Eye
Outer Coat
Sclera: tough, white, fibrous tissue
Cornea: transparent anterior portion that lies over the iris; no blood vessels found in the cornea or in the lens
Vascular Layer of the Eye
Middle Coat
Contains many blood vessels/pigment
Choroid: makes up most of its pigment layer
Anterior portion:
- Ciliary body (thick choroid), suspensory
ligaments (attach/hold lens in place)
- Iris (colored part): smooth/circular m
forming its doughnut shape
Inner Layer of the Eye
Innermost Coat
Retina: outer layer of pigmented epithelium and an inner layer of nervous tissue
Optic Nerve (CNII): extent from eyeball > brain
Neuron Layers of Sensory Retina (3)
Photoreceptor cells: visual receptors, sensitive to light rays
- Rods (night vision)
- Cones (bright light)
Bipolar Cells: transmit info from photoreceptor
cells > ganglion cells
Ganglionic Cells: fibers emerge to form the optic nerve (relay Rods/Cones info & non-image info for melatonin release)
(2) Conditions for the process of seeing
Retinal image must be formed to simulate the receptors (rods and cones)
Resulting image must be conducted to the visual areas of the cerebral cortex for interpretation
Formation of Retinal Image (3 processes)
Refraction: bending/deflection of light
- more convex = greater refractory power
Accommodation: allows normal eye to focus
on things closer than 20ft
- Ciliary mm contract = lens incr curvature
- Constriction of pupils
- Convergent of two eyes
Convergence of Eyes: inward movement
- Closer the object = greater convergence
- Strabismus: abnormal (crossed eye)
Rods
Only one Rhodopsin type (photopigment)
Brain only perceives info from rods as intensity of light, not color
Cones
Three rhodopsin types (photopigments):
- blue/green/red
- color blindness - photopigments abnorm
- less sensative to light
Neural Pathway of Vision
Fibers conduct impulses from rods/cones > visual cortex (occipital lobes) by way of the optic nerves, optic chiasma, & optic tracts
Optic nerve fibers (from only one retina)
Optic chiasma fibers (from the nasal portion of both retinas)
*explains visual abnormalities that sometimes occur
