Download Sensory Cells and Transduction of Stimuli

The Brain
Central sulcus
Frontal
lobe
Parietal
lobe
Parietooccipital
notch
Occipital
lobe
Lateral
fissure
Temporal
lobe
Preoccipital
notch
Supplementary motor area
(programming of complex movement)
Primary motor cortex
(Voluntary movement)
Premotor cortex
Central
sulcus
(coordination of complex
movements)
Prefrontal association
cortex
Somatosensory cortex
(Somesthetic sensation and
proprioception)
Posterior parietal cortex
(integration of somatosensory and
visual input)
Parietal lobe
(planning for voluntary activity;
decision making;
personality traits)
Wernicke’s area
(speech
understanding)
Frontal lobe
Parietal-temporal-occipital
association cortex
Broca’s area
(speech formation)
(integraton of all sensory inputimp in language)
Primary auditory cortex
Occipital lobe
Limbic association cortex
(motivation, emotion, memory)
Temporal lobe
Primary visual cortex
Sensory
Motor
Cranial nerves
= Motor fibers
= Sensory fibers
I-Olfactory nerve
Retina
Mucosa of
nasal cavity
II- Optic nerve
III- Oculomotor
nerve
Olfactory
bulb
V- Trigeminal
nerve
IV - Trochlear nerve
Sensory—face
and head
Sensory—
taste buds on
anterior tongue
VII - Facial nerve
The Senses
Major Sensory Receptors in the Human Body
Table 12.1 p. 409
•
Category and type of receptor
Photoreceptors
vision
Chemoreceptors
taste
smell
internal senses
Mechanoreceptors
touch/pressure/pa in
hearing
balance
body position
Thermoreceptors
temperature
Examples of receptor
Stimulus
rods and cones in the eye
visible li ght
taste buds on the to ngue
olf actory receptors in the nose
osmoreceptors in the
hypothalamus
receptors in the carotid artery
and aorta
food particles in sali va
odour molecules
low blood volume
receptors in the skin
hair cell s in the inner ear
hair cell s in the inner ear
proprioceptors in the muscles
and tendons, and at the joints
mechanical pressure
sound waves
fluid movement
muscle contraction, stretching,
and movement
heat and cold receptors in the
skin
change in radiant energy
blood pH
Sensory Receptors
• When receptors are triggered, they open
up Na+ and K+ channels to trigger an
action potential
The Sense of Sight
• The Eye
Photoreceptors (eye)
• The image-forming eyes of vertebrates
focus detailed images of the visual field
onto dense arrays of photoreceptors that
transduce the visual image into neuronal
signals.
Eye structure
Focusing
Photoreceptors (eye)
• Vertebrates have two types of photoreceptors,
rod cells and cone cells. In humans, the fovea
contains almost exclusively cone cells, which are
responsible for color vision but are not very
sensitive in dim light.
• Color vision is based on the fact that different
cone cells contain different isomers of opsin,
which give them different spectral absorption
properties.
Photoreceptors (eye)
• Photosensitivity depends on the absorption of
photons of light by rhodopsin, a photoreceptor
molecule that consists of a protein called opsin
and a light-absorbing prosthetic group called
retinal.
• Absorption of light by retinal is the first step in a
cascade of intracellular events leading to a
change in the membrane potential of the
photoreceptor cell.
Overview animation
Photoreceptors (eye)
• The innermost layer of the retina consists
of the ganglion cells, which send their
axons in the optic nerve to the occipital
lobe of the brain.
• Between the photoreceptors and the
ganglion cells are neurons that process
information from the photoreceptors.
QuickTime™ and a
TIFF (U ncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (U ncompressed) decompressor
are needed to see this pi cture.
Photoreceptors (eye)
• When excited by light the photoreceptor
cells hyperpolarize and release less
neurotransmitter onto the neurons with
which they form synapses. They do not
fire action potentials.
Excellent overview animation
The Sense of Sound
• The auditory system for mammals involves
several specialized structures found in the ear
– pinna collect and funnels sound waves to the auditory
canal
– tympanic membrane (eardrum), vibrates in response
to sound waves.
– movements of the tympanic membrane are amplified
through a chain of ossicles that conduct the vibrations
to the oval window.
– Movements of the oval window create pressure
waves in the fluid-filled cochlea.
animation of the ear
QuickTime™ and a
TIFF (U ncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (U ncompressed) decompressor
are needed to see this picture.
The Ear
• The basilar membrane running down the center
of the cochlea is distorted by sound waves at
specific locations that depend on the frequency
of the sound. Animation
• These distortions cause the bending of hair cells
in the organ of Corti, which rests on the basilar
membrane. Animation basilar membrane
• Receptor potentials in hair cells cause them to
release neurotransmitter, which creates action
potentials in the auditory nerve
Good overview animation
Balance and equilibrium
Your sense of balance relies on the movement of fluid
In the sacule and utricle and semicircular canals
• Movement of the head in one plane (static) is
monitored by the sacule and the utricle
– nerve impulses triggered by movement of otoliths against
hair receptor due to gravity
Balance animation
Balance and equilibrium
• Rotation of the head is monitored by movement
of fluid in the 3 semicircular cells and their
ampulla
• Movement of fluid causes cillia on the hair cells
in the ampulla to move which will lead to the
membrane to depolarize and pass the signal
onto the brain
– Motion sickness is
caused by rapid
continuous movement
of these fluids
Rotation animation
Sensory Receptors
• Specialized ends of sensory neurons that
receive a specific type of stimulus
Types of Receptors
• General receptors found in the skin
Receptors in Skin
Touch
– Meissner’s copuscles (light touch)
– Pacinian corpuscle
• deep pressure, vibration, rapid
– Ruffini’s corpuscule (continuous pressure)
The Sense of Smell
• Odorant molecules enter the nasal cavity
and bind to specific chemoreceptors
called olfactory sensory cells
• The binding of these molecules trigger ion
channels to open, allowing ions to flow,
thus creating the depolarization of the
membrane
Animation
The Sense of Smell
The Sense of Smell
The Sense of Taste
• Chemicals found in foods bind with
specific chemoreceptors (taste buds) on
the tongue
Animation
Homeo & NS Unit Exam
• 39 M.C.
• 4 N.R.
• 1 S.A. (12) marks
• Lots of Structure and function
• Apply knowledge to new
situations/conditions