Transcript Chapter 18 Senses - Fullfrontalanatomy.com

Senses
I. General Sense
A. “General sense” refers to: temperature, pain, touch, pressure, vibration &
proprioception.
B. Receptors & receptor specificity
- type of sense detected depends on anatomy of receptor
1. free nerve endings (unencapsulated)
2. modified dendritic endings for particular sense eg) encapsulated endings
C. Receptive field
Area monitored by a single receptor cell. The larger the receptive field, harder
it is to pinpoint the stimulus eg) skin: light touch 2.5 in. field. VS tongue field 1mm
D. Types of receptors:
1. nociceptors: stimulated by a variety of stimuli, cause the sensation of pain
Referred pain: pain originating at visceral organs can be sensed as originating
from superficial areas served by same spinal nerve. Mechanism unknown.
2. thermoreceptors: stimulated by change in temperature
3. mechanoreceptors: stimulated or inhibited by physical distortion
a) Tactile receptors: touch & pressure
b) Baroreceptors: stretch receptors monitor changes in stretch of walls
of organs eg) blood vessels
c) Proprioceptors: monitor position of joints, tendons & ligaments.
4. chemoreceptors: stimulated by chemicals (require specific receptors for
chemicals)
Figure 18.3a
Tactile Receptors in the Skin Free Nerve Endings vs.
Encapsulated ones
Hair
Merkel cells and Tactile
tactile discs corpuscle
Free nerve
ending
Ruffini corpuscle
Lamellated corpuscle
Root hair plexus
Free nerve endings
Sensory
nerves
Figure 18.1 Receptors and Receptive Fields
Receptive
field 1
Receptive
field 2
Receptive fields
Figure 18.2 Referred Pain
Heart
Liver and
gallbladder
Stomach
Small
intestine
Appendix
Colon
Ureters
Figure 18.3
Tactile Receptors in the Skin
Merkel cells
Tactile disc
Merkel cells and tactile discs
Merkel cells and Tactile
tactile discs corpuscle
Hair
Free nerve endings
Free nerve
ending
Free nerve endings
of root hair plexus
Tactile
corpuscle Epidermis
Ruffini corpuscle
Lamellated corpuscle
Root hair plexus
Dermis
Dendritic process
Accessory cells
(specialized fibrocytes)
Dermis
Concentric layers (lamellae)
of collagen fibers
separated by fluid
Lamellated corpuscle
Sensory
nerves
Tactile corpuscle
LM  125
Concentric layers (lamellae)
of collagen fibers
separated by fluid
Collagen Sensory
fibers nerve fiber
LM  550
Capsule
Accessory
cells
Dendritic
process
Dendrites
Sensory
nerve fiber
Ruffini corpuscle
Lamellated corpuscle
Tactile corpuscle; the capsule
boundary in the micrograph is
indicated by a dashed line.
Figure 18.4 Baroreceptors and the Regulation of Autonomic Functions
Baroreceptors of Carotid
Sinus and Aortic Sinus
Provide information on blood
pressure to cardiovascular and
respiratory control centers
Baroreceptors of Lung
Baroreceptors of Digestive
Tract
Provide information on volume of
tract segments, trigger reflex
movement of materials along tract
Provide information on lung
stretching to respiratory
rhythmicity centers for
control of respiratory rate
Baroreceptors of Colon
Baroreceptors of Bladder
Wall
Provide information on volume of
urinary bladder, trigger urinary reflex
Provide information on volume
of fecal material in colon,
trigger defecation reflex
Figure 18.5 Chemoreceptors
Chemoreceptive
neurons
Blood vessel
Chemoreceptors in and
near Respiratory Centers
of Medulla Oblongata
Trigger reflexive
adjustments in
depth and rate of
respiration
Sensitive to changes in pH
and PCO2 in cerebrospinal
fluid
Chemoreceptors
of Carotid Bodies
Sensitive to changes in pH,
PCO2, and PO2 in blood
Chemoreceptors
of Aortic Bodies
Sensitive to changes in
pH, PCO2, and PO2 in blood
Carotid body
LM  1500
Via cranial
nerve IX
Via cranial Trigger reflexive
nerve X
adjustments in
respiratory and
cardiovascular
activity
Which of the following types of receptors are
especially common in the superficial portions
of the skin, in joint capsules, within the
periostea of bones, and around the walls of
blood vessels?
a. proprioceptors
b. nociceptors
c. tactile receptors
d. chemoreceptors
• II. Special Senses
•
These are all special senses: Hearing, Vision, Taste,
Equilibrium, Olfaction.
•
A. Olfaction- chemoreceptors in olfactory epithelium
•
B. Gustation (taste)- chemoreceptors (covered in digestive
system)
• III. Eye
•
A. Lacrimal Apparatus
•
1. lacrimal gland, lacrimal ducts, lacrimal punctum,
lacrimal canaliculi (sup. & inf.) lacrimal sac,
nasolacrimal duct nose
•
B. Conjunctiva
•
Clear mucous membrane on inner eyelid & white surface
of the eye.
•
Cornea does not have conjunctiva. It helps lubricate the
eye by producing mucus and some tears, although a
smaller volume of tears than the lacrimal gland. Helps to
prevent the entrance of microbes into the eye
•
Inflammation: Conjunctivitis
Figure 18.6a The Olfactory Organs
Olfactory
bulb
Olfactory nerve
fibers (N I)
Olfactory
tract
Cribriform plate
of ethmoid
Olfactory
epithelium
The distribution of the olfactory receptors
on the left side of the nasal septum is
shown by the shading.
Figure 18.6b The Olfactory Organs
To olfactory
bulb
Olfactory
nerve fibers
Regenerative basal cell:
divides to replace worn-out
olfactory receptor cells
Cribriform
plate
Olfactory
receptor cell
Olfactory
epithelium
Mucous layer
Olfactory cilia:
surfaces contain
receptor proteins
A detailed view of the olfactory epithelium
• C. Layers of the eye
•
1. Fibrous tunic
•
a) Sclera: white of the eye. Collagen & elastic fibers. Thicker at
the back of eye.
•
b) Cornea: made of transparent collagen in regular sheets (like
pages in a book.)
•
The cornea is avascular, getting oxygen via diffusion from air &
nutrients from aqueous humor in anterior chamber. It does
have lots of pain receptors & has high capacity for
regeneration.
•
2. Vascular tunic
•
a) Iris –
•
1) 2 layers of smooth muscle
•
i. Circularly arranged pupillary sphincter muscle
•
ii. radiating pupillary dilating muscles
•
2) pigmented epithium: various am’t of melanin & different
depths account for eye color
•
•
Conjunctiva
• b) Choroid – middle layer, pigmented &
vascularized. Contains lymphatics.
• Blood supply nourishes other layers of the eye.
(in animals: tapedum lucidum reflects light- in
cow/pig eye dissection)
Melanin absorbs light, so it doesn’t reflect within
the eye, causing confusion.
• c) Ciliary body= ciliary muscle (smooth muscle) +
suspensory ligaments that anchor to lens. Ring of
tissue that encircles the lens. Controls shape of
lens for focusing
Figure 18.21a Sectional Anatomy of the Eye
Fibrous Vascular Neural
tunic
tunic
tunic
(sclera) (choroid) (retina)
The three layers, or
tunics, of the eye
Fibrous tunic- Sclera & Cornea
• 3. Neural tunic
•
a) Retina: innermost layer of the eye. Retina itself has 2 layers•
i) outer pigmented layer with melanocytes
•
ii) thick neural layer 3 types of neurons:
•
1. Photoreceptors:
•
rods See light/dark, shades of gray. Rods are very
sensitive to light & suited to night vision. Peripheral
vision & perception of motion.
•
Cones: color vision. 3 types: blue, red & green. (needs
bright light)
•
2. Bipolar cells
•
3. Ganglion cells optic nerve
•
b) macula lutea (yellow spot), at the center of the
macula, there is a pit, called the fovea
centralis which only contains cones! The fovea is
where light is focused when you look directly at
something. Rods not found in fovea.
•
c) optic disc: optic nerve, artery & vein passes through
the retina. Blind spot.
• D. Cavities & Chambers of the Eye
•
1. Anterior Cavity- Filled with aqueous humor (clear, watery).
•
a. anterior chamber in front of iris
•
b. posterior chamber between iris and lens
•
ciliary body creates aqueous humor that moves to anterior
chamber via pupil& drains into Canals of Schlemm: improper
drainage: glaucoma
•
Aqueous humor: 1. Equilibrium of formation & drainage keeps
intraocular pressure constant. 2. Aqueous humor nourishes
cornea & lens (both avascular)
•
2. Posterior Cavity
•
Lens: separates eye into anterior & posterior compartments.
•
Filled with vitreous humor (clear, gelatinous material).
Keeps retina in place.
•
3. Lens : Thick, transparent & biconvex. Concentric layers of
cells that become fibers. Fibers are proteins folded in such a way that they
are transparent. Fibers added throughout life lens thickens with age, is
denser more convex & less elastic- ability to focus diminishes in old age.
Figure 18.21b Sectional Anatomy of the Eye
Ora serrata
Fornix
Palpebral conjunctiva
Posterior cavity
(Vitreous chamber filled
with the vitreous body)
Ocular conjunctiva
Ciliary body
Anterior chamber
(filled with aqueous
humor)
Lens
Pupil
Cornea
Iris
Posterior chamber
(filled with aqueous
humor)
Central retinal
artery and vein
Optic nerve
Optic disc
Fovea
Corneal limbus
Retina
Suspensory
ligaments
Choroid
Sclera
Major anatomical landmarks and features
in a diagrammatic view of the left eye
Figure 18.21c Sectional Anatomy of the Eye
Pupillary
dilator muscles
(radial)
Constrictors contract
Pupil
Pupillary
constrictor muscles
(sphincter)
Dilators contract
The action of pupillary muscles
and changes in pupillary diameter
Figure 18.23a
Retinal Organization
Rods & Cones
Horizontal cell
Cone
Rod
Choroid
Pigmented
part of retina
Rods and
cones
Bipolar cells
Amacrine cell
Ganglion cells
Nuclei of rods Nuclei of
Nuclei of
ganglion cells and cones bipolar cells
The retina
LM  70
LIGHT
Histological organization of the retina. Note that the
photoreceptors are located closest to the choroid
rather than near the vitreous chamber.
What nerve fibers make up the optic nerve?
a) photoreceptors
c) bipolar cells
b) ganglion cells
d) horizontal cells
Figure 18.23c Retinal Organization
-find your
blind spot.
Macula Fovea
lutea
Optic disc Central retinal artery
(blind spot) and vein emerging
from center of optic disc
A photograph taken through the pupil of the
eye showing the retinal blood vessels, the
origin of the optic nerve, and the optic disc
Which of the following is (are) a function(s) of
the vascular tunic of the eye?
a. regulating the amount of light entering
the eye
b. secreting and reabsorbing the aqueous
humor that circulates within the eye
c. controlling the shape of the lens
d. all of the above
Figure 18.22a
The Lens and Chambers of the Eye
Choroid
Posterior
cavity
Ciliary body Vascular
tunic
Iris
(uvea)
Anterior
cavity
Cornea
Neural
tunic
(retina)
Neural part
Sclera
Fibrous
tunic
Pigmented part
The lens is suspended between the posterior cavity
and the posterior chamber of the anterior cavity.
Figure 18.24 The Circulation of Aqueous Humor (Part 1 of 1)
Ciliary process
Posterior chamber
Suspensory
ligaments
Anterior chamber
Pigmented
epithelium
Posterior
cavity
(vitreous
chamber)
Lens
Pupil
Cornea
Canal of Schlemm
Body of iris
Retina
Conjunctiva
Choroid
Sclera Ciliary body
Anterior
cavity
Glaucoma
Glaucoma: drainage ducts are blocked, aqueous humor builds
up-> pressure builds-> compress arteries that serve nerves. If
nerves die, blindness (partial or total, depending on damage)
occurs.
Vision associated with
glaucoma.
•
•
•
•
•
E. Vision Pathway
Optic nerve optic chiasm optic tract
optic radiations occipital lobe
a) Some fibers synapse with thalamus. The
cells at the thalamus form optic radiations
to reach occipital cortex.
b) Other fibers from the optic tract synapse
at the superior colliculus of midbrain
c) other fibers synapse with hypothalamus
Figure 18.26
Anatomy of the Visual Pathways, Part II
Optic chiasm
Optic tract
hypothalamic
nuclei, pineal gland,
and reticular
formation
Hypothalamus
thalamus
thalamus
Superior
colliculus
optic
radiation
LEFT CEREBRAL
HEMISPHERE
RIGHT CEREBRAL
HEMISPHERE
Visual cortex of
cerebral hemispheres
Note the thalamus & superior colliculus are part of the pathway for optic fibers
Vision & the brain TED conference
Figure 18.25
Anatomy of the Visual Pathways, Part I
Cribriform plate
of ethmoid
Crista galli
Right eyeball
Levator palpebrae
superioris muscle
Left eyeball
Superior
rectus muscle
Medial rectus
muscle
Superior oblique
muscle
Branch of N V
Lacrimal
gland
Right optic
nerve (N II)
Superior rectus muscle
Levator palpebrae
superioris muscle
Trochlear nerve (N IV)
Cut ends of
optic nerve
(segment
removed)
Left optic
nerve (N II)
Cerebral arterial circle
Optic chiasm
Horizontal section, superior view
IV. Ear
Ear functions: hearing & equilibrium (balance).
A. Outer ear:
1. Auricle or pinna: “ear”. Shaped to funnel
& amplify sound waves as it enters the
external auditory meatus.
2. External auditory meatus: 2.5 cm long
opening, lined with fine hairs & modified
sweat & sebaceous glands produce
cerumen protects ear from foreign
materials & microbes.
Figure
18.9 Anatomy of the Ear (Part 1 of 1)
EXTERNAL EAR
MIDDLE EAR
INNER EAR
Auditory ossicles Semicircular Petrous part Facial nerve
of temporal
(N VII)
canals
bone
Auricle
External
acoustic
meatus
Bony labyrinth
of inner ear
Tympanic
membrane
Tympanic
cavity
Elastic
cartilage Oval window
Round window
Vestibule
Auditory tube
Cochlea
To
nasopharynx
B. Middle Ear
- The boundary of external to middle ear is the tympanic
membrane.
- Air filled space in the petrous portion of the temporal bone.
1. Ossicles: malleus, incus & stapes
Sound waves external ear vibrate tympanic
membrane malleus, which passes
vibrations to incus & then to stapes. Vibrations are
amplified 20 times by the time it
reaches stapes. Vibrations passed on to oval window of
cochlea.
2. Eustacian tube- links middle ear to superior pharynx,
behind the nasal cavity. About 4cm long.
Normally closed (flattened) but can open when yawning,
swallowing to equalize pressure with
outside. *important b/c eardrum doesn’t vibrate freely if
pressure is not equal
- route for middle ear infections (otitis media)
Figure 18.10b The Middle Ear
Temporal bone
(petrous part)
Stabilizing
ligament
Malleus
Incus
Base of stapes
at oval window
Chorda tympani
nerve (cut), a
branch of N VII
External acoustic
meatus
Stapes
Round window
Tympanic cavity
(middle ear)
Tympanic membrane
(tympanum)
Auditory tube
Structures within the middle ear cavity
C. Inner ear
- also lies in the petrous portion of temporal bone.
1.Cochlea
a) perilymph is found in the vestibular duct & tympanic duct (above &
below
cochlear
duct). The tympanic duct ends at the round window.
b) endolymph inside cochlear duct which also houses the spiral organ
of Corti
c) spiral organ of Corti.
i) Hair cells w/ stereocilia. Hair cells embedded in a basilar
membrane.
ii) tectorial membrane: stereocilia embedded.
iii) At the base, hair cells synapse with sensory fibers of
cochlear
nerve.
As vibrations are transmitted to perilymph in the vestibular
duct, then
to tympanic duct “bounces” the basilar membrane
of the spiral
organbends the stereocilia of hair cells. The
bending causes the
neuron to fire impulses to the cochlear
nerve,  temporal lobe of
brain & inferior colliculus.
iv) pitch: different regions of organ of corti are sensitive &
deform at
different frequencies. Shorter the wavelength =
higher frequency
v) amplitude: size of deformation of basilar membrane
Figure 18.10d The Middle Ear
Malleus
Tendon of tensor
tympani muscle
Malleus attached
to tympanic
membrane
Inner surface
of tympanic
membrane
Incus
Base of
stapes at
oval window
Stapes
Stapedius
muscle
The tympanic membrane and auditory ossicles
as seen through a fiber-optic tube inserted along
the auditory canal and into the middle ear cavity
2. Semicircular canals
- rotational equilibrium.
- 3 canals at right angles to each other
3. Vestibule
- static equilibrium
Hair cells with stereocilia also vestibule & semicircular
canals & function the same (bending
impulse) but are embedded in different structures.
D. Auditory Pathway
1. Sound: cochlear branch vestibulocochlear nerve
inferior colliculus
 thalamus  temporal lobe for processing
2. Equilibrium: vestibular branch vestibulocochlear
nerve  olivary nucleus of
medulla(proprioception) other parts of brain dealing
with equilibrium & proprioception.
Figure
18.12a Semicircular Canals and Ducts
KEY
Semicircular
canal
Membranous
labyrinth
Bony labyrinth
Anterior
Semicircular
ducts
Lateral
Posterior
Vestibule
Cristae within ampullae
Maculae
Endolymphatic sac
Cochlea
Utricle
Saccule
Vestibular duct
Cochlear duct
Anterior view of the bony
labyrinth cut away to show the
semicircular canals and the
enclosed semicircular ducts of
the membranous labyrinth
Tympanic Organ of
duct
Corti
Figure 18.17a The Cochlea and Organ of Corti
Round window
Stapes at
oval window
Cochlear duct
Vestibular duct
Tympanic duct
Cochlear Vestibular
branch
branch
Vestibulocochlear
nerve (VIII)
Semicircular
canals
Structure of the cochlea in partial
section
KEY
From oval window
to tip of spiral
From tip of spiral
to round window
Figure 18.17b The Cochlea and Organ of Corti
Vestibular membrane
Tectorial membrane
Basilar membrane
Vestibular duct
contains perilymph
Organ of Corti
Cochlear duct (contains endolymph)
Tympanic duct
contains perilymph
Cochlear nerve
Vestibulocochlear nerve (VIII)
Structure of the cochlea within the temporal
bone showing the turns of the vestibular duct,
cochlear duct, and tympanic duct
Cochlea
Figure 18.17e The Cochlea and Organ of Corti
Cochlear duct (scala media)
Tectorial membrane
Vestibular membrane
Tectorial membrane
Outer
hair cell
Basilar membrane
Inner hair cell
Nerve fibers
Diagrammatic and histological sections through the
receptor hair cell complex of the organ of Corti
Tympanic duct
Basilar Hair cells Spiral ganglion
(scala tympani) membrane of organ
cells of
of Corti cochlear nerve
Organ of Corti
LM  125
Hair cells are what kind of receptor?
a)Chemoreceptor
d) baroreceptor
b) nociceptor
c) mechanoreceptor
Spiral organ & sound
• high pitch vs low pitch Each part of spiral
organ is sensitive to different frequencies
of waves.
• Amplitude (loudness) is the degree of the vibrations
of basilar membrane. Loud noise cause fluid in canal of
cochlea to exert more pressure on basilar membrane.
See animated
tutorial hearing
Auditory pathway
From spiral organ,
travel to synapse w/
vestibulocochlear
nerve (VIII)
that brings
impulse to synapse
with
medulla
Inferior colliculus
Thalamus
Temporal lobe
Figure 18.13a
The Function of the Semicircular Ducts, Part I
Vestibular branch (N VIII)
Semicircular
ducts
Anterior
Posterior
Lateral
Cochlea
Ampulla
Endolymphatic sac
Endolymphatic duct
Utricle
Anterior view of
the maculae and
semicircular ducts
of the right side
Saccule Maculae
Vestibule & Semicircular canals