1. Sensory  Systems  

2. Learning Objectives
Nerve cells identify particular stimuli, depending on their type.
Neurons carry signal to brain where it is decoded. The brain uses information about which nerve cells are involved, the frequency of impulses (action potentials), and number of neurons in order to identify the stimulus.
What is referred pain?
For each sense, specialized receptors sense the stimulus and transmit information to the brain:
Skin – many types of receptors, including for pain, temperature, pressure
Taste and smell – chemical receptors
Hearing – vibrations of hair cells
Vision – rods and cones identify b/w light and colored light respectively, though rods are much more sensitive to low light than are cones.

3. Perception – understanding of what that stimulus
Sensory
Systems
• Sensation – conscious awareness of a stimulus •
Perception – understanding of what that stimulus
means

4. Sensory Receptors Mechanoreceptors: pressure, position, or
acceleration
Thermoreceptors:
temperature
Receptors • • •
Nocireceptors: damage
tissue (pain)
Chemoreceptors:
chemicals
Osmoreceptors: water
volume
Photoreceptors: visible to • • •
light

5. Nerve impulses are all the same – so how what’s going on? does the
brain
know •
Which nerves are
carrying the impulses?
What is the frequency
of the impulses?
How many neurons responded to the stimulus? • •

6. Somatic Sensations (“of the body”) Touch, pressure, • heat, cold,
pain,
movement
Free nerve
ending: “Naked” dendrites
Encapsulated
receptor: Enclosed in tissue

7. Nociceptors (pain receptors) are free•
Nociceptors (pain receptors) are free
nerve endings

8. Referred Pain Pain from internal organs may be wrongly
projected to parts of skin surface •

9. Taste
Gustation = sense of taste •

10. Smell •
Olfactory
receptors: detect water-soluble or easily vaporized substances
Communicate directly with •
olfactory bulbs
brain in

11. Hearing
Sounds are waves of compressed air •

12. Detecting Sound Waves
Pinnae -> Ear Canal -> Eardrum (vibrations) -> Ear Bones -> Oval Window -> Cochlea •

13. •
Cochlear duct -> Organ of Corti (hair cells)
Hair cells bend, release neurotransmitter to trigger action potential in auditory nerve

14. Hair cells are damaged with exposure to
Progressive Deafness
Hair cells are damaged with exposure to
loud noises •

15. Vision 3 layers of the eye: Outer • Sclera (“white”): protection
Cornea:
focus light •

16. Ciliary Muscle: 3 layers of the eye cont. Middle •
Iris: regulate light
Pupil: entrance for light
Lens: focus light
Ciliary Muscle:
bend lens • •
Inner •
Retina: light-
sensitive tissue

17. Focusing of Light • Cornea is curved – bends light rays •
Pattern on retina is upside-down &
backwards

18. Signals criss-cross as they travel from the •
Signals criss-cross as they travel from the
retina to the brain (corrects upside-down /
backwards issue)

19. Ciliary muscle adjusts the shape of the
Fine-tuning the Focus
Ciliary muscle adjusts the shape of the
lens = accommodation •

20. Common Vision Problems • Nearsightedness, Farsightedness, Astigmatism

21. Photoreceptors with visual pigments found
From visual signals to sight
Photoreceptors with visual pigments found
behind retina •

22. Colorblindness • If two kinds of cones missing = total color blindness
Red-green colorblindness = lack most or all cones
that respond to red or green