BIO Ch. 17 Sensory Organs

Question 1

Sensory Receptor Adaptation

Answer 1

Receptor potential decreases over time > decrease rate of impulse conduction & intensity of sensation

Question 2

Receptor Classification (by location)

Answer 2

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

Question 3

Receptor Classification (by stimulus detected)

Answer 3

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

Question 4

Receptor Classification (by structure)

Answer 4

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

Question 5

Encapsulated Nerve Endings (6)

Answer 5

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

Question 6

Stretch Receptors

Answer 6

Stretch receptors: operate to provide body with information concerning muscle length and strength of muscle contraction

• Muscle Spindle
• Golgi Tendon Organs

Question 7

Muscle spindle (proprioceptors)

Answer 7

“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

Question 8

Golgi tendon organs

Answer 8

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

Question 9

Olfactory Sensory Neurons

Answer 9

Chemoreceptors

Extremely sensitive, but adapt easily /rapidly

Question 10

Taste Buds

Answer 10

Chemoreceptors
Respond to gustatory (taste) stimuli; associated with papillae
Highly sensitive but adapt quickly

Question 11

External Ear Structures

Answer 11

Divisions:

• Auricle (pinna) - visible portion of ear
• External Acoustic Meatus - tube

Question 12

Middle Ear Structures

Answer 12

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)

Question 13

Inner Ear Structures

Answer 13

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

Question 14

Sense of Hearing

Answer 14

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

Question 15

Cochlear Duct Structures

Answer 15

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

Question 16

Pathway of Sound Waves

Answer 16

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

Question 17

Neural Pathway of Hearing

Answer 17

Choclear n impulse > brainstem > nuclei relay in the medulla,pons,midbrain, thalamus > auditory are of temporal lobe

Question 18

Sense of Balance

Answer 18

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

Question 19

Static Equilibrium

Answer 19

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

Question 20

Dynamic Equilibrium

Answer 20

Depends on cristae ampullaris (containing hair cells): doesn’t respond to gravity

Question 21

Muscles of the Eye

Answer 21

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)

Question 22

Structural Layers of the Eyeball (3)

Answer 22

Fibrous Layer (outer coat)
Vascular Layer (middle coat)
Inner Layer (incomplete innermost coat)

Question 23

Fibrous Layer of the Eye

Answer 23

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

Question 24

Vascular Layer of the Eye

Answer 24

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

Question 25

Inner Layer of the Eye

Answer 25

Innermost Coat
Retina: outer layer of pigmented epithelium and an inner layer of nervous tissue
Optic Nerve (CNII): extent from eyeball > brain

Question 26

Neuron Layers of Sensory Retina (3)

Answer 26

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)

Question 27

(2) Conditions for the process of seeing

Answer 27

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

Question 28

Formation of Retinal Image (3 processes)

Answer 28

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)

Question 29

Rods

Answer 29

Only one Rhodopsin type (photopigment)

Brain only perceives info from rods as intensity of light, not color

Question 30

Cones

Answer 30

Three rhodopsin types (photopigments):

• blue/green/red
• color blindness - photopigments abnorm
• less sensative to light

Question 31

Neural Pathway of Vision

Answer 31

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