The Nervous System

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