Read chapter 18 – senses and using your class notes answer:
1. Define a sensory receptor
A structre specialized to receive information from the environment and to generate nerve impulses
a. List the five distinct kinds of sensory receptors and explain the nature of each with an example
Sensory Receptor | Nature |
Chemoreceptor | Respong to chemical substances in immediate vicinity. Taste, smell, chemoreceptors in blood vessels monitoring O2, CO2, and pH |
Pain receptors (type of chemoreceptors) | Type of chemoreceptor. Naked dendrites that respond to chemicals released by damaged tissues give warning ie. appendicitis |
Mechanoreceptors | Stimulated by ...view middle of the document...
Rentinal blood vessels
xix. Optic nerve
b. State the main function for each part of the eye listed see page 350
Structure | Function |
Sclera | Protects and supports eyeball (becomes cornea) |
Cornea | Refracts light rays |
Choroid | Absorbs stray light (becomes iris) |
Retina | Contains receptors for sight (photoreceptors) |
Rods (in retina) | Black/white vision |
Cones | Colour vision |
Fovea centralis (contains cones) | Acute vision |
Lens | Refects and focuses light rays to retina |
Ciliary body | Holds lens in place/accomodation |
Iris | Regulates light entrance; regulates size of pupil |
Pupil | Admits light |
Humours | Transmit light rays and support eyeball |
Optic nerve | Transmit impulse to brain |
c. Describe the difference between rods and cones
Rods: more numerous, dim-light and peripheral receptors, more sensitive to light than cones, but do not provide sharp images or colour
Cones: operate in bright light and provide high-acuity colour vision, have one of three different pigments to give colourk
5. Explain the process of visioning (focusing)
When we look at an object light rays pass through the pupil and are “focused” on the retina. Focusing starts with the cornea and continues as light rays pass through the lens and the humours. The image produced is much smaller than the object due to refraction and is upside down (inverted) and laterally reversed (left to right). The lens provides additional focusing power as visual accommodation occurs for close vision controlled by the ciliary muscle within the ciliary body. When focusing on a distance object the lens is flat because ciliary muscle is relaxed. When focusing on a near object, the lens accommodates and becomes rounded because the ciliary muscle contracts. The optic nerve transmits the nerve impulse to the brain.
6. Since there are only three types of cones, how can you explain the fact that we see many more colours?
The three types of cones are B(blue), G (green), and R (red). Each pigment is made of rental and opsin but there is a slight difference in the structure of opsin in each. To see any color, the brain must compare the input from different kinds of cone cells and then make many other comparisons as well.
The lightning-fast work of judging a color begins in the retina, which has three layers of cells.
* Signals from the red and green cones in the first layer are compared by specialized red-green "opponent" cells in the second layer.
* Other opponent cells then compare signals from blue cones with the combined signals from red and green cones.
7. Explain why you often have to blow your nose after crying.
Because the lacriminal gland that produces tears empties through the excretory laciminal duct into the nasal cavity.
8. Describe the process of hearing
The process of hearing begins when sound waves enter the auditory canal. Sufficient...