1. Sense Organs

2. Objectives
Examine how sensory organs and the nervous system work together to coordinate responses to stimuli.
Describe features of sensory receptors that allow it to receive information from the environment.

3. Sensory Receptors
Sensory receptors are specialized receptors capable of detecting changes in internal or external conditions and communicating that information to the CNS.
Sensory receptors have specialized protein receptors in their plasma membrane that are specific to a stimulus.

4. Initiating a Sensory Event
Every sense receptor generates the same type of impulse.
The brain is responsible for making “sense” of the signals it receives.
There are many sensory events that we are not aware of- if we become aware of it, it is a perception. Sensory adaptation is a decrease in responsiveness.
Amplification is the strengthening of a sensory signal during transduction.

5. Interoreceptors Interoreceptors receive stimuli from inside the body
Blood pressure
Blood pH
Visceroreceptors
Proprioceptors- mechanoreceptors responsible for maintaining muscle tone.

6. Exteroreceptors Detect information from the environment.
Chemoreceptors- transmit information about solute concentration or respond to individual molecules
Electromagnetic- detect light, electricity, and magnetism
Photoreceptors-detect light
Mechanoreceptors- detect physical deformation
Thermoreceptors- detect heat and cold
Nociceptors- detect noxious conditions

7. Sense of Taste 3000 taste buds
Molecules bind to receptor proteins on microvilli of receptor cells, generating a nerve impulse that is sent to the brain
Sweet, salty, sour, bitter, and umami

8. Sense of Smell Olfactory cells are responsible for smell.
There are million olfactory cells.
Each is has 1 of 1000 different receptors.
An odor can stimulate multiple receptor proteins.
Olfactory bulbs connect to the limbic system and its center for memory and emotions.

9. Sense of Vision
Photoreceptors detect light using light absorbing pigment molecules.
Rods- more light sensitive- black and white
Cones- color sensitive- red, green, blue

10. Sense of Hearing Mechanoreceptors are responsible for hearing.
The ear transduces pressure waves into nerve impulses.
Hair cells are responsible for detecting the motion.
Volume is detected by how much the hair bends.
Pitch is detected by the region of the basilar membrane that is vibrated.

12. Sense of Balance
The utricle and saccule perceive position according to gravity and linear movement.
Otoliths (calcium carbonate particles) shift positions when you change the angle of your head, stimulating hair cells to signal your brain of the change in angle.
Three semicircular canals connected to the utricle detect turning and rotational acceleration. The three occupy different spatial planes, so any direction can be detected