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The Nervous System

The Nervous System. Functions. Sensory Detects changes that occur inside and outside of the body Integrative Sensory inputs are put together to create sensation, produce thought, create memory Motor Sends signals to glands or muscles to produce an action. Organization.

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The Nervous System

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  1. The Nervous System

  2. Functions • Sensory • Detects changes that occur inside and outside of the body • Integrative • Sensory inputs are put together to create sensation, produce thought, create memory • Motor • Sends signals to glands or muscles to produce an action

  3. Organization • Divisions of the Nervous System • Central Nervous System (CNS) • Receives and processes information and regulates body activity • Consists of brain and spinal cord • Peripheral Nervous System (PNS) • Carries information to and from the CNS • Consists of cranial and spinal nerves, plexuses, and peripheral nerves

  4. Nerve Cells • Neurons • Base cell of the nervous system • Carry impulses throughout the body in a particular direction Dendrites Cell Body Axon • CNS neurons do not replicate – not replaceable

  5. Nerve Cells • Neuron structure • Cell body • Central portion where the nucleus is located • All processes extend from it • Dendrites • Root-like processes that receive impulses and conduct them to the cell body

  6. Neuron structure (con’t) • Axon • Process that conducts impulses away from the cell body • Can be more than 3 feet long • Sometimes covered in a myelin sheath • Ends in Terminal End Fibers

  7. Neurons

  8. Nerve Cells • A synapseis the space between the terminal end fibers of one neuron and the dendrites of another OR the space between the terminal end fibers of one neuron and a receptor organ • Each neuron can have any number of synapses with other cells

  9. Nerve Cells • Neurotransmitters are chemicals that carry information across a synapse from the neuron to the target receptor • Ex endorphins, serotonin, dopamine, epinephrine

  10. Nerves • Nerves (neur/o) are bundles of neurons, joined end-to-end, that travel together like strands of rope • Two types of nerves are defined according to function and the direction of impulse • Afferent nerves (Sensory) • Efferent nerves (Motor) • Nerves and neurons are the parenchymal tissues of the Nervous System

  11. Nerves • Tract– bundle of nerve fibers located within the brain or spinal cord • Ganglion– cluster of nerve cell bodies outside of the CNS • Plexus– network of intersecting nerves

  12. Nerve Cells • Stromal Tissues of the Nervous System • Glial Cells • AKA neuroglia • supportive and connective cells of the nervous system • Do not conduct impulses • Can replicate • -glia comes from the Greek word that means glue

  13. Nerve Cells • Myelin sheath • White protective covering along the axons of some neurons • Functions to provide insulation and to make signal transmission more efficient

  14. Nerve Cells • White matter is the name given to the portion of nerve cells that have a myelin sheath • Most peripheral nerves, and portions of the nerves in the spinal cord and brain • Grey matter is the name given to the portion of nerve cells that do not have a myelin sheath • Portions of the nerves in the spinal cord and brain

  15. Nerves • Innervation is the supply of nerves to a body part • Receptors are sites that receive sensory stimulation and send messages through the sensory neurons to the brain • Stimulus– anything that excites a nerve and creates an impulse • Impulse – wave of excitation transmitted through a nerve

  16. Central Nervous System • Brain • Encephal/o means brain • Located within the cranial vault • Parts of the brain • Cerebrum • Thalamus • Hypothalamus • Cerebellum • Brainstem

  17. Central Nervous System • Cerebrum • Largest and uppermost portion of the brain • Responsible for thought, memory, sensation, language, intelligence, etc • Cerebr/o means cerebrum (and sometimes brain)

  18. The outer layer of the cerebrum is a sheet of grey matter called the cerebral cortex • Arranged in folds called gyri separated by grooves called sulci

  19. Central Nervous System • Cerebrum is divided into two hemispheres • Referred to as the left and right brain • Connected by the corpus callosum - thick band of nerve fibers • Each hemisphere is further divided into lobes

  20. Central Nervous System • Frontal Lobe • Skilled motor functions, memory, behaviour, personality • Parietal Lobe • Sensation (tongue, skin, muscles) • Occipital Lobe • Vision • Temporal Lobe • Hearing, smell, ability to create, store and access new information, language

  21. Central Nervous System • Inside the cerebrum are four spaces called ventricles which produce and contain cerebrospinal fluid

  22. Central Nervous System • Thalamus (thalam/o) • Relays information from the sense organs and cerebellum to the cerebrum • Controls perception of pain • Located below the cerebrum • Together with the hypothalamus, make up the diencephalon

  23. Central Nervous System • Hypothalamus • Located below the thalamus • Seven major functions • Regulates the autonomic nervous system • Regulates emotional response • Regulates body temperature • Controls hunger sensation • Regulates water balance and thirst • Regulates sleep-wake cycle • Regulates endocrine system function

  24. Central Nervous System • Cerebellum • Cerebell/o means cerebellum • Located at the back of the brain below the cerebrum • Motor center of brain – produces smooth, coordinated movement, maintains balance and posture

  25. Central Nervous System • Brainstem • Connects cerebral hemispheres with the spinal cord • Three parts: • Midbrain • Pons • Medulla Oblongata • Provide conduction pathways and basic life functions like breathing, heart rate, blood pressure, coughing and sneezing, swallowing, vomiting

  26. Central Nervous System • Meninges (mening/o, meningi/o) • Three layers of connective tissue membrane that enclose the brain and spinal cord

  27. Meninges • Dura Mater – tough, outermost covering located just inside the cranial vault and spinal column • Arachnoid Membrane – connected with thin attachment strands that resemble spider webs (arachn/o means spider) • Pia Mater – very thin, adhered to the surface of the brain and spinal cord (rich supply of blood vessels) • Thec/o (sheath) can also be used to refer to the meninges

  28. Central Nervous System • Spaces between the meninges • Subdural space – located between the dura mater and the arachnoid (“potential space”) • Epidural space – located above the dura mater in the spinal column (contains fat and connective tissue to cushion) • Subarachnoid space – located between the arachnoid and the pia mater (contains cerebrospinal fluid)

  29. Central Nervous System • Cerebrospinal Fluid • Produced in the ventricles of the brain • Clear, colourless, watery • Nourishes, cools, and cushions the brain and spinal cord • Transports nutrients and chemical messengers throughout the brain and spinal cord • Blood-brain barrier*

  30. Central Nervous System • Spinal Cord (myel/o) • Pathway for impulses going to and from the brain • Surrounded by meninges and CSF • Inner portion is made up of grey matter and outer portion is white matter • Extends from the base of the skull to the first lumbar vertebra, then becomes the cauda equina

  31. Peripheral Nervous System • Consists of 12 pairs of cranial nerves and 31 pairs of spinal nerves plus branches • Cranial Nerves • Originate from the undersurface of the brain • One member of each pair serves one half of the body • Identified by roman numerals

  32. Smell • Vision • Eye movement • Eye movement • Sensory info from face and head, muscles for chewing • Eye movement • Taste, facial expression, sensory info from ear • Hearing, balance • Taste, swallowing • Sensation and control of organs • Head movement • Tongue movement

  33. Peripheral Nervous System • Spinal Nerves • 31 pairs – grouped together based on region they innervate • Cervical C1-C8 • Thoracic T1-T12 • Lumbar L1-L5 • Sacral S1-S5 • 1 Coccygeal

  34. Spinal Nerves

  35. Autonomic Nervous System • Controls involuntary actions of the body • Divided into two systems that work together to regulate homeostasis • Sympathetic Nervous System • Prepares the body for emergencies by increasing breathing and heart rate, and blood flow to muscles (fight-or-flight response) • Parasympathetic Nervous System • Returns the body to normal after a response to stress • Maintains normal body functions

  36. Medical Specialties • Anesthesiologist • Specializes in administering anesthetic agents before and during surgery • Esthesi/o means feeling or sensation • Anesthetist • Person trained in administering anesthetic agents, but is not necessarily a physician • Neurologist • Specializes in diagnosing and treating disorders of the nervous system

  37. Symptoms • Pain • -algiaand –dynia mean pain • -algesia means sensitivity to pain • Movement • Kines/o, kinesi/omean movement • Bradykinesia • Hyperkinesia • Dyskinesia • Akinetic

  38. Symptoms • Seizures • Electrical disturbance in the brain caused by high fever, brain injury or lesions • Loss of consciousness with twitching or shaking • Less observable staring spells • May be generalized (affect the whole body) or focal (only affect one part or side of the body) • -lepsy means seizure

  39. Symptoms • Weakness • -paresis means weakness or partial loss of movement • Due to nerve damage • Hemiparesis • Monoparesis • Paraparesis

  40. Symptoms • Paralysis • Loss or impairment of the ability to move parts of the body • -plegia means paralysis • Quadriplegia • Paraplegia • Hemiplegia

  41. Symptoms • Speech disorders • -phasia means speech • Aphasia • Motor aphasia • Sensory aphasia • Control of movement • -praxia means action • Apraxia • Tax/o means coordination • Ataxia

  42. Symptoms • Syncope • AKA fainting • Brief loss of consciousness • Caused by decreased flow of blood to the brain

  43. Symptoms • Levels of Consciousness • Conscious means being alert, aware • Unconscious is the state of being unaware – unable to respond to stimuli • Lethargy • Lowered level of consciousness characterized by listlessness, drowsiness, and apathy

  44. Symptoms • Stupor • Impaired awareness - mind and senses are dulled to stimuli • Coma • State of deep unconsciousness • Absence of spontaneous eye movement, no response to pain, no vocalization • Persistent Vegetative State • Type of coma • Patient exhibits a sleep-wake cycle, but is unconscious even when apparently awake

  45. Symptoms • Somnolence • Condition of unnatural sleepiness or semiconsciousness approaching coma • Usually can be aroused by verbal stimuli • Delirium • Sudden onset of confusion, anxiety and cloudiness • Associated with high fever, intoxication, shock • Potentially reversible • Dementia • Slowly progressing decline in mental abilities

  46. Congenital Disorders • Anencephaly • Occurs due to a defect in the first month of pregnancy • Most of the cerebrum does not form, and the rest of the brain is often not covered by bone or skin • Detectable with amniocentesis and prenatal ultrasound

  47. Congenital Disorders • Hydrocephalus • Abnormally increased amount of CSF within the ventricles of the brain • Due to blocked circulation, tumours, infection • Pressure may be relieved with a catheter or “shunt” • May also occur later in life

  48. Congenital Disorders • Spina Bifida • Occurs when vertebrae do not fuse (normally in lumbar region) • Originates in the first four weeks of pregnancy • Opening allows damage to spinal nerves • Defect may be covered over with skin (Occulta), or may be visible because the meninges and/or the spinal cord protrude through the opening • Meningocele, Myelomeningocele

  49. Congenital Disorders • Encephalocele • Herniation of the brain through a gap in the skull

  50. Congenital Disorders • Cerebral Palsy • Condition of poor muscle control, spasticity, speech defects, and other neurological deficiencies • Due to damage that affects the cerebrum • Occurs most often in premature or low-birthweight babies • Usually caused by an injury that occurs during pregnancy, birth or soon after

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