Chapter 9. Coordination and Response

Stimulus is a change in an organism’s environment which is detected by a receptor
Cell that detect stimuli are called receptor cells

The Eye

• Part of the eye that contains the cell receptor is the retina. Retina is sensitive to light
• The front of the eye is covered by a thin transparent membrane n Called the conjuctiva for protection functions. Conjunctiva is always wet or damp with resultant fluid by the lachrymal glands. Tears contain lysosomes who serves as an antibacterial
• Sclera is a very tough coat Surrounding the eye. Function for protection
• 2 kind receptor cells in the retina:
– Rods = quite sensitive to dim light, but only let you see in black n white
– Cones = give color vision, but only in bright light
• Optic nerve = carry messages to the brain for processing
• Fovea = The part of the retina where the receptor cells are packed most closely together
• Blind Spot = part of the eye the which do not have receptor cells
• Choroid = behind the retinal That is a black layer absorbs all the light after it has been through the retina
• Cornea = is Responsible for most of the bending of the light
• Lens = the make fine adjustment
• 2 kind of muscle in the eyes: suspensory ligaments and ciliary muscle
• Iris = adjust how much Light Enters the Eye
• In the middle of the iris is a space, Called the pupil. The Wider the pupil is, the more light can get through to the retina.
Accommodation = the adjustment in the shape of the lens, to focus light coming from different distances


• The part of the body of the which responds to a stimulus is Called an effector. Ex: muscle are effector, if you touch something hot, the contract the muscles in your arm, your hand is so That Quickly Pulled away.
• Most animal (human too) have a central nervous system (Central Nervous System). Central nervous system consists of the Brain (the brain) and Spinal Cord
Sequence of Action – Reaction
Stimulus –> receptors cell –> neuron receptor –> brain –> neuron motor –> effector –> reaction
• Human action can be voluntary or involuntary (motion in humans can be done consciously and unconsciously)

The Endocrine system
Endocrine glands produce hormone. A hormones can be defined as a chemical substance.

A comparison of the nervous and endocrine system in a mammal


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