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The Nervous System Medical Term “Neuro” Different parts of the Nervous System Central Nervous System (CNS) Network of nerve tissue (neurons) found in the brain and spinal cord Peripheral Nervous System (PNS) All nerve tissue (neurons) outside the brain and spinal cord. They include: 12 Cranial (head) nerves that enervate the head/senses 31 pairs of spinal nerves that enervate the arms, trunk, and legs. Nerves can regenerate in the PNS but not in the CNS Also the nervous system boasts the Autonomic Nervous System (ANS) The ANS regulates involuntary actions such as: Thirst Appetite Heart Rate Temperature Respiration. Overview The entire nervous system relies on the 1- way transmission of electrical impulses These impulses are done by neurons, the operating cells of the brain and spinal cord A collection of neurons is called a nerve. Nerves, like blood vessels, reach every organ, every inch of our body. Electrical impulses travel from neuron to neuron as they send information from one area of the body to another. Motor vs Sensory All neurons are either: 1. Sensory Nerves (“you sense”) These nerves receive sensory info from the body and transmit it TO the brain. Also known as Afferent Nerves A=“At the brain” e.g. smell, taste, touch, sight Breeze against your face Most impulses are sent from the nerves in your body to your brain via the spinal cord 2. Motor Nerves (“you move”) These neurons originate from the brain and send impulses to muscles for movement Also known as Efferent Nerves E= “Exit the body” e.g. You move your arm You blink e.g. Burning your hand on the stove. Most nerve bundles in the PNS contain both sensory and motor nerves. Quick Assignment You may work as a group if you like. On a piece of paper write down, 10 feelings a sensory (afferent) neuron would detect. 10 actions a motor (efferent) neuron would do. Neurons Neurons Cells responsible for electrical transmission The brain, spinal cord, and nerves are all comprised of neurons 100 billion neurons just in brain. 3 Major Parts of the Neuron 1. Cell Body Contains nucleus and organelles. 2. Dendrites Short, stubby branches that carry impulses to the cell body from another neuron They are the “receiving” part of neuron 3. Axons Long extension that carries impulses from the cell body Some neurons have axons that are several feet long! Axons transmit impulses to dendrites of the next neuron. They are the “giver” part of a neuron. Axons are surrounding by fat which helps accelerate the electrical impulse. These fat pads are called Myelin Muscular Dystrophy (MS) is the condition in which myelin deteriorates. Neurons (cont) Synapse Open area where the axon of one neuron communicates with the dendrite of the next one. Neurotransmitter The Chemical released at the synapse which allows the electrical impulse to jump across the synapse to reach the next neuron. Famous neurotransmitters Epinephrine (Adrenaline) Dopamine (pleasure) Serotonin (mood) Most depression meds attempt to increase the amount of serotonin at synapse. Excito-toxins Neurotransmitters that destroy the synapse by over stimulating it until it explodes Monosodium Glutamate (MSG) Glial Cells Glial cells is the collective name for a group of cells that care and protect neurons Also called neuroglia They are not responsible for electrical impulse Their job is to: 1. Surround the neurons to anchor them in place (“Glia” means “glue” in Greek) 2. Produce the fat (myelin) of the axon to speed electrical transmission 3. Supplies nutrients to neurons. Schwann Cells are a type of Glial Cells that do this. They also destroys pathogens Astrocytes are a type of Glial Cells that do this. Cell phone radiation The Brain Meninges (sing. Meninx) 3 layers of matter that serve as a protective barrier between the cranium (bone) and the brain. 1. Dura mater (Outermost) 2. Arachnoid Matter Hard, fibrous material Beneath it is the Sub-Archnoid Space Web-like space full of Cerebro-spinal fluid (CSF) 3. Pia mater(Innermost) Thin, transparent layer actually on the brain The Brain Responsible for every physical and mental activity of the body Memory, emotion, thought, judgment, reasoning, consciousness, etc. It is made of white and grey matter Comprised of mostly fat Protected by the cranium Weighs 3 pounds The four major structures of the brain 1. Cerebrum 2. Cerebellum 3. Diencephalon 4. Brain Stem 1. Cerebrum Largest part of the 4 main sections of the brain Outermost layer of the cerebrum is called the Cerebral Cortex It is made of Great Matter The Cortex is divided into 4 regions called Lobes. Most higher-level thinking of the brain occurs in the cortex. 10-14 billion neurons Frontal- Anterior aspect Parietal- Superior aspect Temporal- Lateral aspect Occipital- Posterior aspect Cortex is divided into Left and Right Hemispheres Longitudinal Fissure separates the two hemispheres 1. Cerebrum (cont) Corpus Callosum- joins hemispheres together and quickens communication b/t the two sides. Gyri (sing. gyrus) are the folds or mountains on the cerebral cortex Sulci (sing. sulcus) are the dips or cracks on the cortex. These peaks and dips are used expand the surface area of the cortex; therefore, allowing more higher level of thinking than more primitive mammals. The brain has no pain receptors. Grey vs White Matter The brain is comprised of Grey Matter and White Matter Grey Matter is made mostly of the cell bodies of neurons Cerebral Cortex is Grey Matter Beneath the Cortex the remainder of the Cerebrum and the Spinal Cord are White Matter White Matter Mostly comprised of Glial cells and the long axons of neurons connecting one part of the brain to another. In Short, Grey Matter Higher level thinking Mostly located in Cortex and Diencephalon (Hypothalamus) White Matter Comprises most of the brain as it is the axons of neurons in the cortex connecting to various parts of the brain. Axons are wrapped in white fat (called myelin) which gives white matter its color. Grey Matter more important than White. Mammal Comparison Temporal Lobe of Cerebral Cortex of Cerebrum Two (left and right) Most lateral lobe; located near the ear behind the temporal bone. Interpretation of sounds and language Responsible for processing auditory impulses Features the Hippocampus Main area for memory Occipital Lobe of Cerebral Cortex of Cerebrum Most posterior lobe Located behind the occipital bone Responsible for processing visual stimulus, colors, and understanding words Parietal Lobe of the Cerebral Cortex of the Cerebrum Located on top of brain underneath the parietal bones. Sensory Information, touch, and pain Frontal Lobe of Cerebral Cortex of Cerebrum Located behind the frontal bone; largest of all lobes. Responsible for emotions reason and will Higher level cognition Motor Skills Language Lobotomy Removal of piece of frontal lobe in an effort to “tame” a person who has emotional issues Diencephalon (Interbrain) 3 main parts Thalamus (Grey Matter) It is “The Relayer” for motor and sensory impulses Receives all sensory info from the body and sends it to the appropriate part of the brain for processing Regulates sleep and consciousness The Hypothalamus (Grey Matter) Regulates the Autonomic Nervous System (ANS), the “urges” system Heartbeat, body temperature, peristalsis appetite, et al. Pituitary Gland Master Gland of the Body Sits inferior to the Hypothalamus in the Sphenoid Bone Creates and controls many of the most important hormones in body. 3. Cerebellum “Baby Brain” 2nd largest part of the brain Sits in the posterior portion of the skull, next to occipital bone. Maintains balance and equilibrium Coordinates muscular movement 4. Brain Stem Anterior to Cerebellum, but inferior to Diencephalon and Cerebrum Along with Diencephalon, the brain stem is the oldest and most primitive part of brain. It is the pathway for communication b/t the brain and spinal cord. Comprised of (top to bottom): 1. Midbrain Sleep and temperature regulation 2. Pons- “bridge” in Latin Swallowing, urination, breathing 3. Medulla Oblongata Respiration Cerebro-spinal Fluid (CSF) Syrupy fluid that bathes and protects the brain and spinal cord. Ventricles Chambers full of CSF fluid that are inside the brain. There are 3 Lateral (2) 3rd Ventricle 4th Ventricle After 4th Ventricle CSF travels down spinal cord and around the brain in the Subarachnoid Space CSF is produced in the Choroid Plexus of the ventricle Blood-Brain Barrier Prevents harmful elements in the blood from reaching the blood Brain is normally sterile Cerebral Aqueduct connects the 3rd Ventricle with the: Spinal Cord It serves 2 main purposes: Transmits sensory impulses from the body to the brain, and Transmits motor impulses from the brain to the body The Spinal cord has 31 pairs of spinal nerves exiting it to enervate the trunk, arms, and legs. It runs down the arch of the Vertebra behind the Body Spinal cord ends near L1. The Spinal Cord ends there and becomes the Cauda Equina “Horse Tail” in Latin The Cauda are strands of nerves that run down the rest of the spinal cavity and exit the Sacrum to enervate the legs. BODY ARCH Spinal Cord has Meninges CSF Grey matter (in middle) and white matter Nerve Root coming off of each side with both sensory and motor neurons included in it. Peripheral Nervous System Nerves and Neurons Nerves are a tight collection of the very long axons of several neurons wrapped in a tight fiber No cell bodies are located in nerves Nerves are only located in the Peripheral Nervous System (PNS) In the CNS, there are only neurons and glial cells. Plexus A collection of nerve bundles that come off of spinal cord 3 main ones Brachial Plexus Lumbar Plexus Comes of the spine near lower cspine Enervates the upper extremity Comes off L-spine Enervates hips, groin, abdominal area Sacral Plexus These nerves come off of the Cauda Equina of the spinal cord and exit the Sacrum bone to: Enervates the lower extremity Cranial Nerves Most important nerves in the body. There are 12 All originate off the Brain Stem Always listed in Roman numerals Olfactory Nerve is CN I-Responsible for Smell Optic Nerve is CN II-Responsible for Eyesight Oculomotor Nerve is CN III Trochlear Nerve is CN IV Abducens Nerve is CN VI – All three are for Eye Movement Trigeminal Nerve is CN V-Responsible for Facial Sensation Facial Nerve is CN VII-Responsible for Facial Motor Vestibulocochlear Nerve is CN VIII-Responsible for Hearing and Balance Glossopharyngeal Nerve is CN IX- Responsible for Tongue Movement and Swallowing Vagus Nerve is CN X -Controls diaphragm, heartrate, and most organs in body Accessory Nerve is CN XI- Responsible for Neck Movement Hypoglossal Nerve is CN XII-Responsible for Speech and Swallowing Dermatones Every region of your body is enervated by a particular PNS Spinal Nerve Therefore, doctors are able to pinpoint the location of nerve damage by you telling them where your pain is located. Glans Penis Middle of Patella 3rd Toe Areola The Ears Medical Terms Meningitis – infection of meninges Encephalitis- infection of the brain Encephalopathy- chronic disease of the brain. Chronic Trauma Encephalopathy (CTE)the medical term for the cumulative effect concussions have on NFL players. Hydrocephalus- Increased amount of CSF causes ventricles to swell up. Parasthesia- tingling of skin with no apparent physical cause. Epilepsy- condition of periodic violent seizures. Bell’s Palsy- inability to move facial muscles due to damage to Facial Nerve (CN VII) Aphagia- Inability to swallow Dysphagia- Difficulty swallowing Aphasia- Inability to speak Dysphasia- Difficulty speaking Anosmia – Inability to detect odors Ataxia- inability to move muscles in a coordinated manner. Pathology MeningitisInflammation of the meninges Concussion-Bruising of brain tissue HydrocephalusSwelling of the brain due to increase amount of CSF fluid Encephalitis-Infection of the brain, typically Hydrocephalus “Water in the brain” Excess CSF fluid in the brain The choroid plexus of the ventricles, the cells responsible for producing CSF, either produce too much, or the venous system doesn’t absorb it fast enough It compresses (squeezes) the brain tissue which increases intracranial pressure. Etiology Mal-development in utero May develop during adulthood by a tumor, infection, etc Signs Disease occurs in infants Head swells as brain pushes unsutured cranial bones apart Scalp veins dilate Decreased mental abilities Hydrocephalus Diagnosis Lumbar tap CT/MRI Treatment Shunt A shunt is a tube inserted in the ventricles to move the excess fluid to the right atrium or abdomen. Seizures Uncontrolled, excessive discharge of neurons Multiple causes and types May be caused by external stimuli, drugs, secondary disease. Generalized seizure- loss of consciousness due to multiple parts of the brain seizing Partial- no loss of consciousness, normally only one part of brain seizes. Petit mal seizure (Generalized) Occurs in children Lasts a few seconds, twitches and lip smacking ensue Child returns to normal c no memory of it Grand mal seizure (Generalized) Begins with twitching, nausea, depression Aura-visual or auditory hallucination Loss of consciousness follows The tonic-clonic stage ensues of strong muscle contraction/relaxation as the body contorts itself into strange position. Foaming of the mouth, screaming, and incontinence may ensue. Contractions dissipate, patients wakes up achy and then Seizures Treatment Anti-convulsive and sedative drugs are given to lessen chance of seizure or to minimize outbursts. Huntington’s Disease Genetic disorder, 13 from House has it. Progressive atrophy (or deterioration) of neurons Ventricles swell Symptoms: Wild mood swings, wild jerky movements of extremities, gradual loss of cognitive and motor skills Prognosis: Death! Schizophrenia Chronic mental condition which features the following symptoms: Visual and auditory hallucinations Delusions of personal grandeur The belief that people are plotting against you. Detachment, increased drug use, and suicidal ideation. Dissociative Identity Disorder Formerly Multiple Personality Disorder. Person has at least 2 distinct personalities (alter egos) One personality controls the other Main personality has time of amnesia. Cause: Trauma (physical/sexual) Controversy: CIA Herniated Disc The intervertebral disc is comprised of two components: Nucleus pulposus- inner gelatinous filling Annulus fibrosis- tough outer layer Poor body mechanics, trauma, or degenerative condition cause the nucleus to leak out. It impinges or touches either the spinal cord or the nerve roots that go down the arm or leg Causes loss of motor or sensory sensation and intermittent pain in leg or arm (depending on which plexus it is impinging). Minor day surgery may fix it easily Assignment Identify the following terms: Neuron Dendrite Axon Synaptic Gap Cerebellum Corpus Callosum