Transcript semicircular canals

Sensation
Overview
1. Specialized sensory cell (receptor) detects a
physical or chemical change.
2. The physical or chemical change causes action
potentials in sensory neurons.
3. Sensory neurons carry action potentials through
cranial nerves or spinal nerves to the CNS.
4. Typically the sensory information is carried to the
thalamus where synapses occur.
5. Neurons transmit sensory information from the
thalamus to a specific region of the cerebrum where
the sensation is experienced.
Example: vision
1. Light from the
environment enters
the eyes and strikes
the retina.
5. Neurons are stimulated
in the thalamus and
transmit action potentials
to specific locations in the
occipital lobe.
1. Rods and Cones
(receptors) in the
retina of the eye
detect light.
4. Optic nerve
enters the brain
and leads to the
thalamus.
2. Sensory
neurons in retina
begin producing
action potentials
3. Action
potentials are
carried out of the
eye through the
optic nerve.
Sensory Neurons
Receptors in retina
Synapse in Thalamus
Projection to
The Cerebrum
Types of Sensory Receptors (often modified nerve endings)
Chemoreceptors (tongue, nasal epithelium)
Pain Receptors (respond to chemicals released when tissue is damaged)
Thermoreceptors (temperature of skin and at the hypothalamus)
Mechanoreceptors (proprioceptors in muscles and joints, hearing, balance)
Photoreceptors (detect light - eye)
Visceral Pain
- referred pain
Lacrimal gland
Lacrimal sac
Nasolacrimal
duct
Eye video
Anterior chamber (aqueous humor)
iris
sclera
Posterior chamber
(vitreous humor)
Ciliary body
Optic disc
Retina
(fovea)
lens
conjunctiva
cornea
Choroid layer
Functions of Key Parts of the Eye
Iris: dilates and constricts thereby regulating the amount of light that
enters to posterior chamber of the eye.
Ciliary body: muscular – pulls on suspensory ligaments and causes
the lens to bend and change focus.
Fovea centralis: area having the densest amount of photoreceptors
Optic Disk (blind spot): area on retina where neurons leave and form
optic nerve. No photoreceptors are found here.
Structure of the Retina
Receptors in retina
Sensory Neurons
Synapse in Thalamus
Projection to
The
Cerebrum
HEARING: System that converts the pressure changes in air into
Changes in action potential frequencies.
When something vibrates, it causes the air to move back and forth.
This generates “sound waves” which are slight increases and decreases
Local air pressure.
Semicircular canal
Auricle
(pinna)
stapes
incus
malleus
cochlea
Auditory tube
(Eustachian tube)
tympanum
Auditory canal
The cochlea contains sensory cells that
provide our perception of hearing
Function of the Ear
When air waves strike
the tympanum, the
malleus, incus and
stapes move. The
stapes presses up
against the oval
window causing fluid
to move within the
cochlea. The
movement of the
fluids is eventually
detected by sensory
cells within the
cochlea.
Oval window
Hair cells in the
cochlea detect the
movement of
fluids in the
cochlea
tympanun
Round window
The cochlea contains receptor cells that detect sound.
At the base of the semicircular canals we find receptor cells
that detect dynamic equilibrium (changes in movement in the
sagittal, coronal and transverse plains)
In each case, “hair cells” are the receptor cells. These cells
detect fluid movements in the inner ear and transduce these
fluid movements into action potentials.
cilia
Current flow
Sensory nerve fiber
Hearing video
To detect motion, sensory cells (hair cells) detect
movement of fluids within the semicircular canals
The Sense of Smell
Olfactory bulb
Cribiform plate
of ethmoid bone
Olfactory cells
Nasal cavity