Human Nervous System and Sensory Perception Explained

1. Interaction and Coordination

The basic path of a nerve impulse from stimulus to response is:

1. A stimulus occurs.
2. Sensory receptors detect the stimulus.
3. Sensory neurons receive the information and transmit it to the central nervous system (CNS).
4. The CNS receives the information and a response is decided.
5. Motor neurons transmit the response to the effectors.
6. Effectors carry out the response. An effector can be a muscle or a gland.
7. The response is given. There are two types: motor responses, which are carried out by muscles, and secretory responses, which are carried out by glands.

Coordination Systems

• Nervous system: Receives and transmits information rapidly via electrical impulses through sensory neurons and processes them in the CNS. Responses are short-lived.
• Endocrine system: Consists of glands that secrete hormones. Hormones are carried in the blood to target tissues or organs. Responses are slow but long-lasting.

2. Sensory Receptors

Sensory receptors capture information from internal and external environments.

Types of Sensory Receptors

• Interoceptors: Located within the body, in muscles and organs. They are sensitive to general body conditions and sensations like thirst or the need to urinate.
• Exteroreceptors: Located in the sense organs at or near body surfaces. They are sensitive to external stimuli.

Classification by Stimuli

3. The Eye

4. The Sense of Touch

• Epidermis: The outer layer, made up of several layers of cells. The surface cells are dead.
• Dermis: The inner layer, which contains the touch receptors.

5. The Senses of Smell and Taste

Smell: Involves the olfactory nerve, olfactory bulb, olfactory membrane, respiratory mucous membrane, and nasal cavity.

Taste: