Sensory Organs and Nervous System

Lesson 2 Overview

In this lesson, you'll learn the basic components, functions, and diseases of sensory organs and the nervous system. Sensory organs include general sensory receptors as well as special organs, such as the eyes, ears, nose, and tongue. Sensory organs enable you to see, hear, smell, and taste. General sensory receptors throughout your body enable you to feel pressure, pain, touch, vibration, and changes in temperature.

The nervous system comprises the brain, the spinal cord, and a vast network of nerves. The nervous system controls all of your bodily functions as well as all voluntary and involuntary movements in your body. This lesson will help you gain knowledge of various diseases and treatment options related to sensory organs and nervous system diseases, including psychiatric disorders. While discussing treatment of these disorders, you'll learn about the medications used to treat each disorder. Medications listed throughout this unit are listed as generic names with brand names provided in parenthesis. 

 

Lesson Objectives

• Illustrate various sensory organs, common diseases, and treatment options
• Explain the basic anatomy and physiology of the nervous system
• Describe common nervous system diseases and psychiatric disorders along with treatment options

 

Introduction

The senses are divided into two groups: general sense organs and special sense organs. Sensory organs include general sensory receptors as well as special organs, such as the eyes, ears, nose, and tongue. Sensory organs enable you to see, hear, smell, and taste. General sensory receptors throughout your body enable you to feel pressure, pain, touch, vibration, and changes in temperature.

 

General Sense Organs

The general sense organs are the tactile receptors, the temperature receptors, the pain receptors, and the proprioceptors. General sense organs enable you to experience touch, pressure, vibration, pain, changes in temperature, and muscle stretch. The receptors for these senses are spread throughout the integumentary system of your body and within some of its internal organs.

Tactile Receptors 

Tactile receptors bring you information about pressure, touch, and vibration. They're located throughout your skin but are more abundant in areas such as the fingertips and the lips.

Temperature Receptors

Temperature receptors enable you to sense changes in temperature. Although they're found throughout the body, they're concentrated in the lips, the mouth, and the anus.

Pain Receptors

Pain receptors are located throughout the skin and within certain internal organs. Some organs, however, are poorly supplied with pain receptors, making it difficult for you to determine where it actually hurts. An example of that is a headache; headaches can be felt due to the pain in the brain, the skull, the neck, or the blood vessels.

Proprioceptors

These enable you to sense the position of various body parts without looking and to sense whether the body parts are moving and in what direction. This sense of positioning is called proprioception, or kinesthesia. The receptors are located within muscles, joints, and tendons. Once the receptors detect a stimulus such as pain, pressure, or touch, the stimulus is converted into an electrical signal or a nerve impulse. The signal then travels the nerve pathways to the brain, where the sensation is interpreted. After the brain interprets the stimulus, it sends orders back along the nerve pathways to the organs and/or other muscles to react appropriately to the receptor.

 

Special Sense Organs

The special sense organs are the eyes, the ears, the nose, and the taste buds. The special senses are touch, vision, hearing, smell, and taste. Touch is mediated through the integumentary system. The remaining senses are mediated by the eyes, the ears, the nose, and the tongue. 

These organs receive sensory signals and transmit to the brain by way of the cranial nerves. Although sensory organs don't appear to be similar to nerves, they can be considered appendages of the nervous system. Each of these organs has unique sensory cells that pick up data and then transmit it to the brain for decoding of the collected data. (5 senses: smell, sight, hearing, taste, touch)

 

The nose can detect about 10,000 different smells. A highly specialized connection of nervous tissue, the olfactory bulb, or olfactory epithelium, enables your nose to smell. The part of the brain that analyzes scents works closely with memory and emotion. That's why the sense of smell can evoke powerful feelings and memories. Olfactory nerves are never replaced; once they're damaged, the sense of smell is impaired forever. They also tire quickly, which explains why a pungent odor seems to dull after it has been sensed for a while.

 

The tongue is the only skeletal muscle that also has sensory capability. Your tongue helps you speak, moves food around as you chew, and molds food into a ball—or bolus—for swallowing. Its surface is covered with visible, bumpy, hair-like projections called papillae. Clusters of taste buds surround the papillae and also cover the roof of your mouth. The taste buds themselves aren't visible. For a taste to be stimulated, the food must be solubilized. The mouth does this by providing saliva through the salivary ducts. The stimulus of food prompts the ducts to release saliva so the food can start to be dissolved. Specialized cells in the taste buds, gustatory cells, then detect the basic sensations of sour, salty, bitter, and sweet. The information is then converted to impulses and transmitted to the brain. The sweet and salty tastes are sensed mainly at the tip of the tongue. The sour taste is sensed at the sides of the tongue, and the bitter taste is sensed at the back of the tongue.

 

Common Eye Disorders and Treatments

- Glaucoma is a diseased caused by increased pressure in the eye, which results in a damaged optic nerve. Increased pressure may be caused by factors such as high blood pressure, obesity, migraines, and heredity. Since there are usually no symptoms until there's a decrease in vision, annual eye exams are extremely important to detect this disease during the early stages. If untreated, glaucoma can lead to blindness. The most common form of glaucoma is called open-angle glaucoma. Open-angle glaucoma is treatable with medications, Lasik, and surgery. 

The following eyedrops are commonly used to treat glaucoma:

• Pilocarpine (Isopto Carpine)
• Carbachol (Isopto Carbachol)
• Latanoprost (Xalatan)
• Travoprost (Travatan)
• Timolol (Timoptic)
• Dorzolamide (Trusopt)
• Betaxolol (Betoptic)
• Acetazolamide (Diamox)

- A cataract is a cloudiness of the eye's lens due to increased age. This disease may be caused by trauma or radiation exposure. Symptoms include blurred vision, faded colors, and sensitivity to light. Common risk factors include increased age, diabetes, smoking, prolonged exposure to sunlight, and alcohol. A mainstay of the cataract treatment is the surgical removal of the cataract lens and replacement with a new lens. Cataract surgery is a minor outpatient surgery performed routinely to treat cataracts. Medicated eyedrops are normally used prior to surgery to dilate the pupils and post-surgery for inflammation and infection. Eyedrops that dilate pupils are called mydriatic medications. The following is a list of mydriatic medications:

• Tropicamide (Mydriacyl)
• Atropine (Isopto Atropine)
• Cyclopentolate (Cyclogyl)
• Phenylephrine (Mydfrin)

The following eyedrops are used for inflammation and infection:

• Bacitracin, Neomycin, and Polymyxin B (Polysporin)
• Ketorolac (Acular)

- Conjunctivitis, or the inflammation or irritation of the conjunctiva, is the most common infection of the eye. Conjunctivitis is also referred to as "pink eye." The infection can be caused by a virus, bacteria, or an allergen. The common cold, an upper respiratory infection, or a sore throat may lead to conjunctivitis. Symptoms include swollen, scratchy, red, and extremely watery eyes.

The following antibiotic eyedrops are commonly used to treat "pink eye" or conjunctivitis:

• Ciprofloxacin (Cipro)
• Ciprofloxacin and dexamethasone (Ciprodex)
• Tobramycin (Tobrex)
• Trimethoprim/polymyxin (Polytrim)

 

Common Ear Disorders and Treatments

Ear infections 

Outer ear infections are called external otitis, and middle ear infections are called otitis media. External otitis is often referred to as "swimmer's ear." Otitis media is a common type of ear infection in children that's often treated with oral antibiotics.

Earwax

If your ear produces too much cerumen or earwax, it can collect in the auditory canal. When this happens, the cerumen absorbs or blocks the passage of sound waves. This blockage impairs hearing. Treatment for this includes irrigation of the ear canal and the use of lubricating drops. Carbamide peroxide (Debrox), over-the-counter (OTC) eardrops, is commonly used to remove excess earwax. 

 

Summary

Eye medications are available in various dosage forms including solution, suspension, ointment, or gel. Your eye is a sterile environment requiring sterile preparations that are instilled in the eye to treat various disorders. However, ear medications are non-sterile. It's very important to keep eye and ear medications separate. 

Do not use eardrops in eyes. You must label an eye medication with a 28-day expiration date once it has been opened and exposed to the non-sterile environment. Discard eyedrops after they've been opened for 28 days. Wash your hands before instilling eyedrops or eardrops. Eardrops may be painful if instilled as a cooled solution in the refrigerator. The Commonly Used Ear Medications and Commonly Used Eye Medications tables list the commonly used ear and eye medications.

 

                                                  Commonly Used Ear Medications

 

Generic Name                                                                  Brand Name                              Indication

Ciprofloxacin                                                                      Cipro                                             Antibiotic

Ofloxacin                                                                             Floxin                                            Antibiotic                                                                                  

Neomycin, Polymyxin B, and Hydrocortisone              Cortisporin OTIC                         Antibiotic and Inflammatory

Ciprofloxacin + dexamethasone                                     Ciprodex OTIC                             Antibiotic and Inflammatory

Carbamide Peroxide                                                         Debrox                                         Earwax removal

 

 

                                                             Commonly Used Eye Medications

 

Generic Name                                                                                    Brand Name                                                 Indication

Olopatadine                                                                                          Patanol                                                           Allergic conjunctivitis

Ciprofloxacin                                                                                         Cipro                                                               Antibiotic

Neomycin, Polymyxin B, and Gramicidin                                         Neosporin                                                      Antibiotic     

Bacitracin, Neomycin, and Polymyxin B                                           Polysporin                                                      Antibiotic

Neomycin, Polymyxin B, and dexamethasone susp./oint             Maxitrol                                                          Antibiotic and steroid anti-inflammatory

Diclofenac                                                                                              Voltaren                                                         Anti-inflammatory

Ketorolac                                                                                                Acular                                                             Anti-inflammatory

Bacitracin ointment                                                                                                                                                      Blepharitis                                                      

Polyvinyl alcohol + Providone                                                            Refresh Eyes                                                  Dry and itchy eyes

Polyvinyl alcohol                                                                                  Artificial Tears                                                Dry eyes

Brimonidine                                                                                          Alphagan                                                        Glaucoma

Dorzolamide + Timolol                                                                        Cosopt                                                            Glaucoma                                 

Dorzolamide                                                                                         Trusopt                                                           Glaucoma

Acetylcholine solution                                                                         Miochol-E                                                       Glaucoma

Pilocarpine                                                                                            Isopto Carpine                                               Glaucoma                                                     

Cyclosporine                                                                                         Restasis                                                         Immunosuppressant, increase tear production

Mineral Oil + Petrolatum                                                                    Lacri-Lube drops/ointment                        Lubricant

Atropine drops/ointment                                                                                                                                           Mydriasis (pre-procedure)

Tropicamide                                                                                         Mydriacyl                                                       Mydriasis (pre-procedure)

Tetrahydrozoline                                                                                 Visine                    Mydriasis (pupil dilation, vasoconstriction, and relieving inflammation

Oxymetazoline                                                                                    OcuClear              Mydriasis (pupil dilation, vasoconstriction, and relieving inflammation    

 

Key Points

• Your body's composed of general sense receptors spread throughout the integumentary system and other body organs to sense pain, temperature, vibration, and touch.
• The eyes, the ears, the nose and the tongue are special sensory organs that help you to see, hear, smell, and taste.
• Glaucoma and cataract are common eye disorders.
• Glaucoma is caused by increased pressure in the eye, and cataract is due to cloudiness of the eye's lens.
• It's important not to mix eye drops with ear drops.
• Anything going into the eyes must be sterile.
• Label opened vials of eye drops with a 28-day expiration date from the date it's opened.