Counselling Psychology, School Counseling, Uncategorized

Urinary Incontinence (Enuresis) in Children – Bed Wetting

What is enuresis in children?

Urinary incontinence (enuresis) is the loss of bladder control. In children younger than age 3, it’s normal to not have full bladder control. As children get older, they become more able to control their bladder. Wetting is called enuresis when it happens in a child who is old enough to control his or her bladder. Enuresis can happen during the day or at night. It can be a frustrating condition. But it’s important to be patient and remember that it’s not your child’s fault. A child does not have control over enuresis. And there are many ways to treat it and help your child.

There are 4 types of enuresis. A child may have 1 or more of these types:

  • Nighttime (nocturnal) enuresis. This means wetting during the night. It’s often called bedwetting. It’s the most common type of enuresis.
  • Daytime (diurnal) enuresis. This is wetting during the day.
  • Primary enuresis. This happens when a child has not fully mastered toilet training.
  • Secondary enuresis. This is when a child has a period of dryness, but then returns to having periods of wetting.

What causes enuresis in a child?

Enuresis has many possible causes. The cause of nighttime enuresis often is not known. But possible causes and risk factors may include 1 or more of these:

  • Anxiety
  • Attention deficit/hyperactivity disorder (ADHD)
  • Certain genes
  • Constipation that puts pressure on the bladder
  • Delayed bladder development
  • Diabetes
  • Not enough antidiuretic hormone (ADH) in the body during sleep
  • Obstructive sleep apnea
  • Overactive bladder
  • Slower physical development
  • Small bladder
  • Structural problems in the urinary tract
  • Trouble feeling that the bladder is full while asleep
  • Urinary tract infection
  • Very deep sleep

Daytime enuresis may be caused by:

  • Anxiety
  • Caffeine
  • Constipation that puts pressure on the bladder
  • Stopping urine stream before finishing (dysfunctional voiding)
  • Not going to the bathroom often enough
  • Not urinating enough when going
  • Overactive bladder
  • Small bladder
  • Structural problems in the urinary tract
  • Urinary tract infection
  • Keeping legs too close together traps urine in the vagina and urine leaks out (vaginal voiding)

Which children are at risk for enuresis?

A child is more at risk for enuresis if he or she:

  • Is constipated
  • Doesn’t have regular bathroom habits
  • Has physical development problems
  • Has anxiety

What are the symptoms of enuresis in a child?

Symptoms can be a bit different for each child. The main symptom is when a child age 5 or older wets their bed or their clothes 2 times a week or more, for at least 3 months. But 1 in 10 children age 7, 1 in 20 children age 10, and 1 in 100 children older than 15 still have at least one episode of nighttime enuresis.

The symptoms of enuresis can seem like other health conditions. Have your child see his or her healthcare provider for a diagnosis.

How is enuresis diagnosed in a child?

Many children may have enuresis from time to time. It can take some children longer than others to learn to control their bladder. Girls often have bladder control before boys. Because of this, enuresis is diagnosed in girls earlier than in boys. Girls may be diagnosed as young as age 5. Boys are not diagnosed until at least age 6.

Your child’s healthcare provider will ask about your child’s health history. Tell the healthcare provider:

  • If other family members have had enuresis
  • How often your child urinates during the day
  • How much your child drinks in the evening
  • If your child has symptoms such as pain or burning when urinating
  • If the urine is dark or cloudy or has blood in it
  • If your child is constipated
  • If your child has had recent stress in his or her life

The healthcare provider may give your child a physical exam. Your child may also need tests, such as urine tests or blood tests. These are done to look for a health problem, such as an infection or diabetes.

How is enuresis treated in a child?

In most cases, enuresis goes away over time and does not need to be treated. If treatment is needed, many methods can help. These include:

  • Changes in fluid intake. You may be told to give your child less fluids to drink at certain times of day, or in the evening.
  • Keeping caffeine out of your child’s diet. Caffeine can be found in cola and many sodas. It is also found in black teas, coffee drinks, and chocolate.
  • Night waking on a schedule. This means waking your child in the night to go urinate.
  • Bladder training. This includes exercises and urinating on a schedule.
  • Using a moisture alarm. This uses a sensor that detects wetness and sounds an alarm. Your child then gets up to use the bathroom.
  • Medicines. Medicines can boost ADH levels or calm bladder muscles.
  • Therapy (counseling). Working with a therapist can help your child cope with life changes or other stress.

Work with your child’s healthcare provider to find out the best choices that may help your child.

What are possible complications of enuresis in children?

Possible problems from enuresis can include:

  • Emotional stress and embarrassment
  • Skin rash from wet underwear

How can I help my child live with enuresis?

  • Remember that your child can’t control the problem without help. Don’t scold or blame them.
  • Make sure your child is not teased by family or friends.
  • Keep in mind that many children outgrow enuresis.
  • Protect your child’s mattress bed with a fitted plastic sheet.
  • Have a change of clothes on hand while out and about.

When should I call my child’s healthcare provider?

Call the healthcare provider if your child has:

  • Symptoms that don’t get better, or get worse
  • New symptoms

Key points about enuresis in children

  • Urinary incontinence (enuresis) is the loss of bladder control. In children under age 3, it’s normal to not have full bladder control. As children get older, they become more able to control their bladder.
  • It can happen during the day or at night.
  • It has many possible causes. These include anxiety, constipation, genes, and caffeine.
  • In many cases, it goes away over time and does not need to be treated.
  • If treatment is needed, many methods can help. These include changes in fluid intake, reducing caffeine, and urinating on a schedule.

Next steps

Tips to help you get the most from a visit to your child’s healthcare provider:

  • Know the reason for the visit and what you want to happen.
  • Before your visit, write down questions you want answered.
  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you for your child.
  • Know why a new medicine or treatment is prescribed and how it will help your child. Also know what the side effects are.
  • Ask if your child’s condition can be treated in other ways.
  • Know why a test or procedure is recommended and what the results could mean.
  • Know what to expect if your child does not take the medicine or have the test or procedure.
  • If your child has a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your child’s provider after office hours. This is important if your child becomes ill and you have questions or need advice.
Counselling Psychology, School Counseling, Uncategorized

Tic disorders

Tics are irregular, uncontrollable, unwanted, and repetitive movements of muscles that can occur in any part of the body.

Movements of the limbs and other body parts are known as motor tics. Involuntary repetitive sounds, such as grunting, sniffing, or throat clearing, are called vocal tics.

Tic disorders usually start in childhood, first presenting at approximately 5 years of age. In general, they are more common among males compared with females.

Many cases of tics are temporary and resolve within a year. However, some people who experience tics develop a chronic disorder. Chronic tics affects about 1 out of 100.

Types of tics disorders

Tic disorders can usually be classified as motor, vocal, or Tourette’s syndrome, which is a combination of both.

Motor and vocal tics can be short-lived (transient) or chronic. Tourette’s is considered to be a chronic tic disorder.

Transient tic disorder

mother and child drawing together

Transient tic disorder occurs for less than 1 year, and are more commonly motor tics.

According to the American Academy of Child and Adolescent Psychiatry, transient tic disorder or provisional tic disorder affects up to 10 percent of children during their early school years.

Children with transient tic disorder will present with one or more tics for at least 1 month, but for less than 12 consecutive months. The onset of the tics must have been before the individual turned 18 years of age.

Motor tics are more commonly seen in cases of transient tic disorder than vocal tics. Tics may vary in type and severity over time.

Some research suggests that tics are more common among children with learning disabilities and are seen more in special education classrooms. Children within the autism spectrum are also more likely to have tics.

Chronic motor or vocal tic disorder

Tics that appear before the age of 18 and last for 1 year or more may be classified as a chronic tic disorder. These tics can be either motor or vocal, but not both.

Chronic tic disorder is less common than transient tic disorder, with less than 1 percent of children affected.

If the child is younger at the onset of a chronic motor or vocal tic disorder, they have a greater chance of recovery, with tics usually disappearing within 6 years. People who continue to experience symptoms beyond age 18 are less likely to see their symptoms resolved.

Symptoms

The defining symptom of tic disorders is the presence of one or more tics. These tics can be classified as:

  • Motor tics: These include tics, such as head and shoulder movements, blinking, jerking, banging, clicking fingers, or touching things or other people. Motor tics tend to appear before vocal tics, although this is not always the case.
  • Vocal tics: These are sounds, such as coughing, throat clearing or grunting, or repeating words or phrases.

Tics can also be divided into the following categories:

  • Simple tics: These are sudden and fleeting tics using few muscle groups. Examples include nose twitching, eye darting, or throat clearing.
  • Complex tics: These involve coordinated movements using several muscle groups. Examples include hopping or stepping in a certain way, gesturing, or repeating words or phrases.

Tics are usually preceded by an uncomfortable urge, such as an itch or tingle. While it is possible to hold back from carrying out the tic, this requires a great deal of effort and often causes tension and stress. Relief from these sensations is experienced upon carrying out the tic.

child in his mothers arms

Anxiety, anger, and fatigue may make the symptoms of a tic disorder worse.

The symptoms of tic disorders may:

  • worsen with emotions, such as anxiety, excitement, anger, and fatigue
  • worsen during periods of illness
  • worsen with extreme temperatures
  • occur during sleep
  • vary over time
  • vary in type and severity
  • improve over time

Causes and risk factors

The exact cause of tic disorders is unknown. Within Tourette’s research, recent studies have identified some specific gene mutations that may have a role. Brain chemistry also seems to be important, especially the brain chemicals glutamate, serotonin, and dopamine.

Tics that have a direct cause fit into a different category of diagnosis. These include tics due to:

  • head injuries
  • stroke
  • infections
  • poisons
  • surgery
  • other injuries

In addition, tics can be associated with more serious medical disorders, such as Huntington’s disease or Creutzfeldt-Jakob disease.

Risk factors for tic disorders include:

  • Genetics: Tics tend to run in families, so there may be a genetic basis to these disorders.
  • Sex: Men are more likely to be affected by tic disorders than women.

Complications

Conditions associated with tic disorders, especially in children with TS, include:

  • anxiety
  • ADHD
  • depression
  • autism spectrum disorder
  • learning difficulties
  • OCD
  • speech and language difficulties
  • sleep difficulties

Other complications associated with tic disorders are related to the effect of the tics on self-esteem and self-image.

Some research has found that children with TS or any chronic tic disorder experience a lower quality of life and lower self-esteem than those without one of these conditions.

In addition, the Tourette Association of America say that people with TS often experience difficulties with social functioning due to their tics and associated conditions, such as ADHD or anxiety.

Diagnosis

Tic disorders are diagnosed based on signs and symptoms. The child must be under 18 at the onset of symptoms for a tic disorder to be diagnosed. Also, the symptoms must not be caused by other medical conditions or drugs.

The criteria used to diagnose transient tic disorder include the presence of one or more tics, occurring for less than 12 months in a row.

Chronic motor or vocal tic disorders are diagnosed if one or more tics have occurred almost daily for 12 months or more. People with a chronic tic disorder that is not TS, will experience either motor tics or vocal tics, but not both.

TS is based on the presence of both motor and vocal tics, occurring almost daily for 12 months or more. Most children are under the age of 11 when they are diagnosed. Other behavioral concerns are often present, as well.

To rule out other causes of tics, a doctor may suggest:

Treatment and coping

Treatment depends on the type of tic disorder and its severity. In many cases, tics resolve on their own without treatment.

Severe tics that interfere with daily life may be treated with therapies, medications, or deep brain stimulation.

Therapies for tic disorders

man speaking to a therapist

Some types of cognitive behavioral therapy can help people manage the discomfort of a tic disorder.

Some therapies are available to help people control tics and reduce their occurrence, including:

  • Exposure and response prevention (ERP): A type of cognitive behavioral therapy that helps people become accustomed to the uncomfortable urges preceding a tic, with the aim of preventing the tic.
  • Habit reversal therapy: A treatment that teaches people with tic disorders to use movements to compete with tics, so the tic cannot happen.

Medication

Medication can be used alongside therapies or on its own. Medication typically reduces tic frequency, but does not completely get rid of the symptoms. Available medications include:

  • anti-seizure medications
  • Botox injections
  • muscle relaxants
  • medications that interact with dopamine

Other medications may help symptoms associated with tic disorders. For example, antidepressantscan be prescribed for symptoms of anxiety and OCD.

Deep brain stimulation

Deep brain stimulation (DBS) is an option for people with TS whose tics do not respond to other treatments and impact someone’s quality of life.

DBS involves the implantation of a battery-operated device in the brain. Certain areas of the brain that control movement are stimulated with electrical impulses with the aim of reducing tics.

Coping and self-help tips

Some lifestyle changes can help reduce the frequency of tics. They include:

  • avoiding stress and anxiety
  • getting enough sleep

It can be helpful to:

  • join a support group for people with TS and other tic disorders
  • reach out to friends and others for help and support
  • remember that tics tend to improve or disappear with age

Parents of children with tics may wish to:

  • inform teachers, caregivers, and others who know the child, about the condition
  • help boost the child’s self-esteem by encouraging interests and friendships
  • ignore times when a tic occurs, and avoid pointing it out to the child
Basic Psychology, Biology of Psychology, Uncategorized

Types of Sensations

1.Gustation (Taste)

Gustation is the special sense associated with the tongue. The surface of the tongue, along with the rest of the oral cavity, is lined by a stratified squamous epithelium. Raised bumps called papillae(singular = papilla) contain the structures for gustatory transduction. There are four types of papillae, based on their appearance (Figure 2): circumvallate, foliate, filiform, and fungiform. Within the structure of the papillae are taste buds that contain specialized gustatory receptor cells for the transduction of taste stimuli. These receptor cells are sensitive to the chemicals contained within foods that are ingested, and they release neurotransmitters based on the amount of the chemical in the food. Neurotransmitters from the gustatory cells can activate sensory neurons in the facial, glossopharyngeal, and vagus cranial nerves.

The left panel shows the image of a tongue with callouts that show magnified views of different parts of the tongue. The top right panel shows a micrograph of the circumvallate papilla, and the bottom right panel shows the structure of a taste bud.

Figure 2. The Tongue. The tongue is covered with small bumps, called papillae, which contain taste buds that are sensitive to chemicals in ingested food or drink. Different types of papillae are found in different regions of the tongue. The taste buds contain specialized gustatory receptor cells that respond to chemical stimuli dissolved in the saliva. These receptor cells activate sensory neurons that are part of the facial and glossopharyngeal nerves. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

 

Once the gustatory cells are activated by the taste molecules, they release neurotransmitters onto the dendrites of sensory neurons. These neurons are part of the facial and glossopharyngeal cranial nerves, as well as a component within the vagus nerve dedicated to the gag reflex. The facial nerve connects to taste buds in the anterior third of the tongue. The glossopharyngeal nerve connects to taste buds in the posterior two thirds of the tongue. The vagus nerve connects to taste buds in the extreme posterior of the tongue, verging on the pharynx, which are more sensitive to noxious stimuli such as bitterness.


2.Olfaction (Smell)

Like taste, the sense of smell, or olfaction, is also responsive to chemical stimuli. The olfactory receptor neurons are located in a small region within the superior nasal cavity (Figure 3). This region is referred to as the olfactory epithelium and contains bipolar sensory neurons. Each olfactory sensory neuron has dendrites that extend from the apical surface of the epithelium into the mucus lining the cavity. As airborne molecules are inhaled through the nose, they pass over the olfactory epithelial region and dissolve into the mucus. These odorant molecules bind to proteins that keep them dissolved in the mucus and help transport them to the olfactory dendrites. The odorant–protein complex binds to a receptor protein within the cell membrane of an olfactory dendrite. These receptors are G protein–coupled, and will produce a graded membrane potential in the olfactory neurons.

The axon of an olfactory neuron extends from the basal surface of the epithelium, through an olfactory foramen in the cribriform plate of the ethmoid bone, and into the brain. The group of axons called the olfactory tract connect to the olfactory bulb on the ventral surface of the frontal lobe. From there, the axons split to travel to several brain regions. Some travel to the cerebrum, specifically to the primary olfactory cortex that is located in the inferior and medial areas of the temporal lobe. Others project to structures within the limbic system and hypothalamus, where smells become associated with long-term memory and emotional responses. This is how certain smells trigger emotional memories, such as the smell of food associated with one’s birthplace. Smell is the one sensory modality that does not synapse in the thalamus before connecting to the cerebral cortex. This intimate connection between the olfactory system and the cerebral cortex is one reason why smell can be a potent trigger of memories and emotion.

The nasal epithelium, including the olfactory cells, can be harmed by airborne toxic chemicals. Therefore, the olfactory neurons are regularly replaced within the nasal epithelium, after which the axons of the new neurons must find their appropriate connections in the olfactory bulb. These new axons grow along the axons that are already in place in the cranial nerve.

The top left panel of this image shows the side view of a person’s face with a cup containing a beverage underneath the nose. The image shows how the aroma of the beverage passes through the nasal cavity. The top right panel shows a detailed ultrastructure of the olfactory bulb. The bottom panel shows a micrograph of the nasal cavity.

Figure 3. The Olfactory System. (a) The olfactory system begins in the peripheral structures of the nasal cavity. (b) The olfactory receptor neurons are within the olfactory epithelium. (c) Axons of the olfactory receptor neurons project through the cribriform plate of the ethmoid bone and synapse with the neurons of the olfactory bulb (tissue source: simian). LM × 812. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)


3.Audition (Hearing)

Hearing, or audition, is the transduction of sound waves into a neural signal that is made possible by the structures of the ear (Figure 4). The large, fleshy structure on the lateral aspect of the head is known as the auricle. Some sources will also refer to this structure as the pinna, though that term is more appropriate for a structure that can be moved, such as the external ear of a cat. The C-shaped curves of the auricle direct sound waves toward the auditory canal. The canal enters the skull through the external auditory meatus of the temporal bone. At the end of the auditory canal is the tympanic membrane, or ear drum, which vibrates after it is struck by sound waves. The auricle, ear canal, and tympanic membrane are often referred to as the external ear. The middle ear consists of a space spanned by three small bones called the ossicles. The three ossicles are the malleusincus, and stapes, which are Latin names that roughly translate to hammer, anvil, and stirrup. The malleus is attached to the tympanic membrane and articulates with the incus. The incus, in turn, articulates with the stapes. The stapes is then attached to the inner ear, where the sound waves will be transduced into a neural signal. The middle ear is connected to the pharynx through the Eustachian tube, which helps equilibrate air pressure across the tympanic membrane. The tube is normally closed but will pop open when the muscles of the pharynx contract during swallowing or yawning.

This image shows the structure of the ear with the major parts labeled.

Figure 4. Structures of the Ear. The external ear contains the auricle, ear canal, and tympanic membrane. The middle ear contains the ossicles and is connected to the pharynx by the Eustachian tube. The inner ear contains the cochlea and vestibule, which are responsible for audition and equilibrium, respectively.

Equilibrium (Balance)

Along with audition, the inner ear is responsible for encoding information about equilibrium, the sense of balance. A similar mechanoreceptor—a hair cell with stereocilia—senses head position, head movement, and whether our bodies are in motion. These cells are located within the vestibule of the inner ear. Head position is sensed by the utricle and saccule, whereas head movement is sensed by the semicircular canals. The neural signals generated in the vestibular ganglion are transmitted through the vestibulocochlear nerve to the brain stem and cerebellum.

The utricle and saccule are both largely composed of macula tissue (plural = maculae). The macula is composed of hair cells surrounded by support cells. The stereocilia of the hair cells extend into a viscous gel called the otolithic membrane (Figure 10). On top of the otolithic membrane is a layer of calcium carbonate crystals, called otoliths. The otoliths essentially make the otolithic membrane top-heavy. The otolithic membrane moves separately from the macula in response to head movements. Tilting the head causes the otolithic membrane to slide over the macula in the direction of gravity. The moving otolithic membrane, in turn, bends the sterocilia, causing some hair cells to depolarize as others hyperpolarize. The exact position of the head is interpreted by the brain based on the pattern of hair-cell depolarization.

This diagram shows how the macula orients itself to allow for equilibrium. The top left panel shows the inner ear. The bottom left panel shows the cellular structure of the macula. In the top right panel, a person’s head is shown in the side view along with the orientation of the macula. In the bottom right panel, a person’s head is shown with the head tilted forward and depicts the orientation of the macula to account for the tilt.

Figure 10. Linear Acceleration Coding by Maculae. The maculae are specialized for sensing linear acceleration, such as when gravity acts on the tilting head, or if the head starts moving in a straight line. The difference in inertia between the hair cell stereocilia and the otolithic membrane in which they are embedded leads to a shearing force that causes the stereocilia to bend in the direction of that linear acceleration.

The semicircular canals are three ring-like extensions of the vestibule. One is oriented in the horizontal plane, whereas the other two are oriented in the vertical plane. The anterior and posterior vertical canals are oriented at approximately 45 degrees relative to the sagittal plane (Figure 11). The base of each semicircular canal, where it meets with the vestibule, connects to an enlarged region known as the ampulla. The ampulla contains the hair cells that respond to rotational movement, such as turning the head while saying “no.” The stereocilia of these hair cells extend into the cupula, a membrane that attaches to the top of the ampulla. As the head rotates in a plane parallel to the semicircular canal, the fluid lags, deflecting the cupula in the direction opposite to the head movement. The semicircular canals contain several ampullae, with some oriented horizontally and others oriented vertically. By comparing the relative movements of both the horizontal and vertical ampullae, the vestibular system can detect the direction of most head movements within three-dimensional (3-D) space.

The left panel of this image shows a person’s head in a still position. Underneath this, the ampullary nerve is shown. The right panel shows a person rotating his head, and the below that, the direction of movement of the cupula is shown.

Figure 11. Rotational Coding by Semicircular Canals. Rotational movement of the head is encoded by the hair cells in the base of the semicircular canals. As one of the canals moves in an arc with the head, the internal fluid moves in the opposite direction, causing the cupula and stereocilia to bend. The movement of two canals within a plane results in information about the direction in which the head is moving, and activation of all six canals can give a very precise indication of head movement in three dimensions.


4.Somatosensation (Touch)

Somatosensation is considered a general sense, as opposed to the special senses discussed in this section. Somatosensation is the group of sensory modalities that are associated with touch, proprioception, and interoception. These modalities include pressure, vibration, light touch, tickle, itch, temperature, pain, proprioception, and kinesthesia. This means that its receptors are not associated with a specialized organ, but are instead spread throughout the body in a variety of organs. Many of the somatosensory receptors are located in the skin, but receptors are also found in muscles, tendons, joint capsules, ligaments, and in the walls of visceral organs.

Two types of somatosensory signals that are transduced by free nerve endings are pain and temperature. These two modalities use thermoreceptors and nociceptors to transduce temperature and pain stimuli, respectively. Temperature receptors are stimulated when local temperatures differ from body temperature. Some thermoreceptors are sensitive to just cold and others to just heat. Nociception is the sensation of potentially damaging stimuli. Mechanical, chemical, or thermal stimuli beyond a set threshold will elicit painful sensations. Stressed or damaged tissues release chemicals that activate receptor proteins in the nociceptors. For example, the sensation of heat associated with spicy foods involves capsaicin, the active molecule in hot peppers. Capsaicin molecules bind to a transmembrane ion channel in nociceptors that is sensitive to temperatures above 37°C. The dynamics of capsaicin binding with this transmembrane ion channel is unusual in that the molecule remains bound for a long time. Because of this, it will decrease the ability of other stimuli to elicit pain sensations through the activated nociceptor. For this reason, capsaicin can be used as a topical analgesic, such as in products such as Icy Hot™.

If you drag your finger across a textured surface, the skin of your finger will vibrate. Such low frequency vibrations are sensed by mechanoreceptors called Merkel cells, also known as type I cutaneous mechanoreceptors. Merkel cells are located in the stratum basale of the epidermis. Deep pressure and vibration is transduced by lamellated (Pacinian) corpuscles, which are receptors with encapsulated endings found deep in the dermis, or subcutaneous tissue. Light touch is transduced by the encapsulated endings known as tactile (Meissner) corpuscles. Follicles are also wrapped in a plexus of nerve endings known as the hair follicle plexus. These nerve endings detect the movement of hair at the surface of the skin, such as when an insect may be walking along the skin. Stretching of the skin is transduced by stretch receptors known as bulbous corpuscles. Bulbous corpuscles are also known as Ruffini corpuscles, or type II cutaneous mechanoreceptors.

Other somatosensory receptors are found in the joints and muscles. Stretch receptors monitor the stretching of tendons, muscles, and the components of joints. For example, have you ever stretched your muscles before or after exercise and noticed that you can only stretch so far before your muscles spasm back to a less stretched state? This spasm is a reflex that is initiated by stretch receptors to avoid muscle tearing. Such stretch receptors can also prevent over-contraction of a muscle. In skeletal muscle tissue, these stretch receptors are called muscle spindles. Golgi tendon organs similarly transduce the stretch levels of tendons. Bulbous corpuscles are also present in joint capsules, where they measure stretch in the components of the skeletal system within the joint.


5.Vision

Vision is the special sense of sight that is based on the transduction of light stimuli received through the eyes. The eyes are located within either orbit in the skull. The bony orbits surround the eyeballs, protecting them and anchoring the soft tissues of the eye (Figure 12). The eyelids, with lashes at their leading edges, help to protect the eye from abrasions by blocking particles that may land on the surface of the eye. The inner surface of each lid is a thin membrane known as the palpebral conjunctiva. The conjunctiva extends over the white areas of the eye (the sclera), connecting the eyelids to the eyeball. Tears are produced by the lacrimal gland, located beneath the lateral edges of the nose. Tears produced by this gland flow through the lacrimal duct to the medial corner of the eye, where the tears flow over the conjunctiva, washing away foreign particles.

This diagram shows the lateral view of the eye. The major parts are labeled.

Figure 12. The Eye in the Orbit. The eye is located within the orbit and surrounded by soft tissues that protect and support its function. The orbit is surrounded by cranial bones of the skull.