Nervous System Intro PDF - Module 1

Module 1: Introduction to the Nervous System Afferent vs Efferent Afferent (sensory) information is carried from the bodies tissues, about its internal and external environments to the central nervous system. Efferent (motor) transmission of directive signals from the CNS to effector...

Module 1: Introduction to the Nervous System Afferent vs Efferent Afferent (sensory) information is carried from the bodies tissues, about its internal and external environments to the central nervous system. Efferent (motor) transmission of directive signals from the CNS to effectors in the body tissues. CNS vs PNS vs ENS Central Nervous System (CNS) - Includes the brain and spinal cord. Peripheral Nervous System (PNS) - Includes everything else within the nervous system. Split into the sensory and motor division. The sensory division carries afferent signals from sensory neurons to the CNS. The motor division carries efferent signals from the CNS to effectors. Motor division can be further split into two more divisions; The somatic nervous system is also known as the voluntary nervous system because it controls voluntary movement. The autonomic nervous system monitors and controls body activities such as cardiac, smooth muscle, glands etc) automatically. Autonomic nervous system can be split to two more subdivisions; Module 1 1  The sympathetic nervous system is also known as the fight or flight system, and activity can come from being excited, scared, and threatened. Parasympathetic nervous system is also known as the rest and digest system. Used to conserve and restore energy systems, and increased digestive and urinary functions. Comparing Sympathetic and Parasympathetic Function Module 1 2 Enteric Nervous System (ENS) The enteric system is the largest and most complex unit of the peripheral nervous system, with ~600 million neurons releasing a multitude of neurotransmitters to facilitate the motor, sensory, absorptive, and secretory functions of the gastrointestinal tract. Module 1 3  The Cranial Nerves There are 12 pairs of cranial nerves that arise from the brain stem and mostly innervate the head. Some are part of the CNS and most are part of the PNS. The Nerves and important functions are as follows: 1. Olfactory: Sensation of smell 2. Optic: Sensation of vision 3. Oculomotor: Movements of the eye and eyelid. Parasympathetic control of pupil size 4. Trochlear: Movements of the eye 5. Trigeminal: Sensation of touch to the face. Movement of muscles of mastication (chewing) 6. Abducens: Movements of the eye 7. Facial: Movement of the muscles of facial expression. Sensation of taste in anterior two thirds of the tongue. 8. Auditory-Vestibular: Sensation of hearing and balance 9. Glossopharyngeal: Movement of muscles in the throat. Parasympathetic control of the salivary glands. Sensation of taste in posterior one-third of the tongue. Detection of blood pressure changes in the aorta 10. Vagus: Parasympathetic control of the heart, lungs, and abdominal organs. Sensation of pain associated with viscera. Movement of muscles in the throat 11. Spinal Accessory: Movement of muscles in the throat and neck 12. Hypoglossal: Movement of the tongue Module 1 4 Module 1 5 Cranial Nerve V: Trigeminal The trigeminal nerve supplies sensations to the face and other structures of the head. It has 3 divisions; - Ophthalmic - Maxillary - Mandibular. This division is motor for the muscles of mastication which includes the masseter and temporals. Trigeminal neuralgia is one of the most painful afflictions known. The typical form causes extreme, sporadic, sudden shock-like (paroxysmal) facial pain in the areas of the face where the branches of the nerve are distributed. The pain episodes last from a few seconds to as long as two minutes. These attacks can occur in quick succession lasting as long as two hours. Trigeminal neuralgia is often called "tic douloureux" because of muscle tics that accompany the pain. Usually the precipitating cause is idiopathic (unknown). Module 1 6 Cranial Nerve VII: Facial The Facial Nerve is efferent to the muscles of facial expression, lacrimal (tear) glands and two salivary glands. Paralysis (palsy) is a complete or partial loss of function especially when involving motion, often accompanied by weakness and the loss of sensation. Flaccid paralysis is paralysis in which muscle tone is lacking in the affected muscle. Spastic paralysis is paralysis with sustained tone (spasm) in the affected muscles. Bell’s palsy is a form of flaccid paralysis of CN VII. Bell’s Palsy develops suddenly and is usually unilateral. It may be due to edema, viral infections, trauma, or pressure from a tumor. Many people start recovering in about 3 weeks, even without treatment. Facial synkinesis is a voluntary muscle movement causing simultaneous involuntary contraction of other facial muscles or glands. It is caused by faulty CN VII regeneration. Examples include eye closure with contraction of mouth muscles, midfacial movements with eye closure and crocodile tears - excessive lacrimation provoked by eating. Treatment: facial retraining aka Mime Therapy includes massage, stretching and coordination exercises which aim to develop a conscious connection between the use of facial muscles and emotional expression. Therapists teach patients to limit unwanted synkinetic movements. If needed, Botox can be employed as well. Module 1 7 Cranial Nerve VIII: The Vestibulocochlear Nerve The vestibulocochlear nerve consists of 2 separate nerves the vestibular and cochlear nerves. The vestibular nerve is responsible for maintaining balance. The cochlear nerve is responsible for hearing. The vestibular system’s inner ear balance mechanism works with the visual system to stop objects blurring when the head moves. They also help maintain awareness of our position when lying down, walking, running or riding in a vehicle. The inner ear semicircular canals are filled with fluid. The inner ear also contains calcium carbonate crystals (aka ear crystals, otoliths) embedded in a membrane outside the semicircular canals. Both are involved in the detection of various motions of the head and body. If otoliths manage to end up in the semicircular canals, the result can be a misperception that the environment is spinning (vertigo). Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. Vertigo is the most common type of dizziness. This may be associated with nausea, vomiting, sweating, or difficulty walking. It is typically worse when the head is moved. Benign paroxysmal positional vertigo (BPPV) is a common problem. It is usually triggered by quick changes in head position often when turning over or sitting up quickly in bed (or on a massage table). It increases the chance of falls. It can be extremely disconcerting and sometimes debilitating. Epley maneuvers are a series of movements that attempt to remove the ear crystals out of the semicircular canals. Module 1 8 Cervicogenic dizziness is dizziness specifically related to neck issues including muscle tension. It usually does not involve vertigo. It is a controversial term; the diagnosis should be made after the many other possible causes of dizziness have been ruled out. The differential diagnosis includes BPPV, ear infections and rotational vertebral artery occlusion. This occlusion can be caused by osteophytes on the neck vertebrae that may pinch the artery during certain neck movements; treatment includes massage, physiotherapy, medications and surgery. Module 1 9 Cranial Nerve X: Vagus The vagus nerve supplies motor parasympathetic fibers to all the organs (except the adrenal glands), from the neck down to the second segment of the transverse colon. The vagus also controls a few skeletal muscles, including the mm. of the larynx. The vagus nerve is responsible for such varied tasks as heart rate, gastrointestinal peristalsis, sweating, and quite a few muscle movements in the mouth, including speech. Cranial Nerve XI: Accessory This nerve is motor to sternocleidomastoid (SCM) & trapezius. Patients with acquired torticollis (wry neck) present with the head twisted to the affected side and the chin pointed toward the opposite shoulder. Patients complain of pain, neck stiffness, and decreased range of motion. Onset is generally acute. Treatment of torticollis includes analgesics, heat, massage, and stretching exercises. Module 1 10  The Meninges Protects the CNS from the overlying bone (encases the CNS). They are as follows: - Epidural Space: The adipose and connective tissue filled space between the wall of the vertebral canal and the dura mater (no epidural space in the brain). - The Dura Mater: Outermost layer, a tough inelastic surrounding. - Subdural Space: Interstitial fluid- fulled space between the dura mater and arachnoid membrane - The Arachnoid Membrane: The middle layer. spiderweb consistency - Subarachnoid Space: CSF filled space between arachnid membrane and the pia mater - Pia Mater: Innermost layer. Thin membrane that adheres closely to the surface of the brain. There may be blood vessels that ultimately run into the brain Meningitis - Meningitis is an inflammation of the meninges. - The most common causes of meningitis are viral and bacterial infections. Symptoms include neck stiffness, vomiting, fatigue, and confusion. - Other causes of meningitis are CSF leaks that can cause the fluid to leak into the ears, nose, and spinal canal. - CSF leakage should be diagnosed and treated quickly and effectively to prevent meningitis. Module 1 11  The Ventricular System Are the fluid-filled caverns and canals inside the brain. The fluid that runs in this system is cerebral spinal fluid (CSF). CSF is produced by special tissue called choroid plexus, in the ventricles of the cerebral hemispheres Noteworthy Definitions Collections of Neurons - Grey Matter: A generic term for a collection of neuronal cell bodies in the CNS. - Cortex: Any collection of neurons that form a thin sheet, usually at the brains surface (Eg. cerebral cortex). - Nucleus: Mass of neurons in the CNS - Ganglion: Collection of neurons in the PNS Collections of Axons - Nerve: Bundle of axons in the PNS. - White Matter: A generic term for a collection of CNS axons. - Tract: A collection of axons having a common site of origin and a common destination in the CNS. Module 1 12