The Nervous System

1. The Nervous System

2. The Divisions of the NervousSystem • The Central Nervous System • Brain • Spinal Cord • The Peripheral Nervous System • Mixed Sensory and Motor Nerves • Sensory Nerves • Motor Nerves • Voluntary Somatic Nerves • Involuntary Autonomic Nerves • Sympathetic Nerves • Parasympathetic Nerves

3. The Divisions of the Nervous System • Somatic v Autonomic • Somatic: voluntary motor neurons; cell body in CNS with axon connecting to skeletal muscle • Autonomic: (internal body organs) Involuntary motor neuron; two neurons with one cell body in CNS and one in PNS 1. Sympathetic - speeds up heart, constricts vessels 2. Parasympathetic - controls body under normal conditions

4. The Neuron The Basics • The cell body: contains the nucleus and dendrites • The Dendrites: carry impulses to the cell body • The Axons: carry impulses away from the cell body • * The Myelin sheath provides insulation for the axon and speeds impulse conduction from the cell body to the axon terminals (white fiber) • * Lose the Myelin sheath and lose control over skeletal muscle (multiple sclerosis)

5. The Neuron The Basics • Schwann cell are supporting cells that wrap themselves tightly around the axon forming the myelin sheath • Neurilemma: outer most part of the Schwann cell • Nodes of Ranvier: exposed membrane at regular intervals • Receptor ending: peripheral nerve ending specialized for response to particular types of stimuli • Synapse: * region of communication between the axons of one neuron and the dendrites of another • Acetylcholine: chemical transmitter substance released by nerve endings

6. The Neuron The Basics • Nerve fiber: axon or dendrite of a neuron • Nerve: bundle of axons outside of the central nervous system • Ganglion: group of nerve-cell bodies in the PNS • Tract: collection of nerve fibers in the CNS having the same origin, termination, and function

7. Types of Neurons • Sensory Neurons (Afferent)Carry impulses to the CNS • Motor Neurons (Efferent)Carry impulses from the CNS to muscles and glands *instructs muscles to contract • Inter-NeuronsCarry impulses from one neuron to another • Mixed NeuronsComposed of both sensory and motor fibers (e.g. Cranial nerve V – Trigeminal: clenches jaw/chewing, sensation of forehead, cheeks, and jaw)

8. Types of Neurons • Myoneural JunctionAlso known as neuromuscular junction; Axon terminal of a motor neuron, synaptic cleft, and sarcolemma of a muscle cell

9. The Central Nervous System Protected by: • *Bones: cranium and spinal vertebrae, encase the brain and spinal cord • *Meninges: cover the brain and spinal cord, tough membranes composed of three layers 1. dura mater 2. arachnoid 3. pia mater • *Ventricles: cavities within the skull that act as safety valves to relieve pressure • *Cerebrospinal Fluid: surrounds the brain and spinal cord, transfers impacts over a greater surface area acting as a shock absorber

10. The Central Nervous System • Encephalon or Interbrain • Sits on top of brain stem • Includes cerebrum, cerebellum, medulla oblongata, pons, and midbrain

11. The Central Nervous System The Brain • The Cerebrum (largest part) • Frontal Lobe • Personality (logic, emotions, memory, consciousness, etc.) • * Motor area • * Thought processes • Parietal Lobe • Somatic Sensory area • Temporal Lobe • Speech (Broca’s Area) • Auditory area • Occipital Lobe • Visual area

12. The Central Nervous System • The Cortex • * Outermost layer of Cerebrum • * Gray matter of the brain • Contains most of the convolutions (folds) of the brain

13. The Central Nervous System The Brain (cont.) • Cerebellum • * Balance • * Equilibrium • * Coordination

14. The Central Nervous System The Brain (cont.) • Hypothalamus • * Regulates body temp • * Regulates water homeostasis • * Regulates metabolism

15. The Central Nervous System • Hemispheres • Connected by cerebral nerves to opposite sides of the cerebrum • Right Side • Controls left side of body • Controls speech, calculation, and writing • Main language center • Left Side • Controls right side of body • Controls spatial abilities, simple language, comprehension, nonverbal ideation

16. The Central Nervous System The Brain (cont.) • Thalamus • Relay station for sensory impulses passing up to the sensory cortex • Encloses 3rd ventricle of the brain

17. The Central Nervous System The Brain-stem (joins spinal cord to brain) • Medulla oblongata: *controls vital body functions • Heart rate • Blood pressure • Breathing • Swallowing • Vomiting

18. The Central Nervous System The Brain-stem • Pons • “Bridge” area, mostly fiber tracts • Does have important nuclei involved in controlling breathing

19. The Central Nervous System The Brain-stem • Midbrain • Anteriorly composed of two bulging fiber tracts which convey ascending and descending impulses • Posteriorly, composed of four bulging nuclei which are reflex centers involved with vision and hearing

20. The Central Nervous System • Meninges • *Dura mater: double layered membrane, outermost covering, very strong, fused to inner surface of skull (periosteal layer) and covers brain (meningeal layer) • *Arachnoid mater: middle layer, web like • Subarachnoid space: area where cerebrospinal fluid • *Pia mater: innermost layer, very delicate, clings to brain and spinal cord following every fold

21. The Central Nervous System • Brain matter: • Gray: composed of neuron cell bodies; concentrated in cerebral cortex • White: composed of fiber tracts (bundles of nerve fibers); connects various parts of the brain with each other and the spinal cord

22. The Central Nervous System • Spinal Cord Matter • Gray matter: • located in center of cord in an H-shapeconsists of cell bodies and dendrites • Anterior or ventral horns contain motor neurons of the somatic (voluntary) NS • Posterior or dorsal horns contain association neurons, interneurons, and sensory neurons • Sensory nerves that enter the cord via the dorsal root have their cell bodies in the dorsal root ganglion • Motor nerves exit the cord via the ventral root • The dorsal and ventral roots make up the spinal nerve

23. The Central Nervous System • Spinal Cord Matter • White matter: • surrounds gray matter • Consists of myelinated fiber tracts (axons) that transmit impulses to or from the brain or from one side of the cord to the other • Afferent tracts: Fiber tracts that carry sensory impulses to the brain are sensory tracts • Efferent tracts: Fiber tracts that carry impulses from the brain to skeletal muscle are motor tracts

24. The Central Nervous System • Spinal Cord • *Is the pathway for messages to get from the body to the brain and vice versa via • *It is the reflex center and allows reflex impulses to bypass the brain and go directly to the motor neurons to protect the body

25. Peripheral Nervous System • Link between CNS and the rest of the bodyConsists of all nerves outside of the CNS • Cranial Nerves • Spinal Nerves • Autonomic Nervous System • Sympathetic Nerves • Parasympathetic Nerves • Cranial Nerves

26. Cranial Nerves • On I - OlfactoryOld II - OpticOlympus III - OculomotorTowering IV - TrochlearTops V - TrigeminalA VI - AbducensFinn VII - FacialAnd VIII - AcousticGerman IX - GlossalpharyngealViewed X - Vagus (abdominal viscera, longest nerve)Some XI – Spinal AccessoryHops XII - Hypoglossal • Cranial Nerve Testing Video

27. Cranial Nerve Assessment - Neurological Examination of the Nervous System • Cranial Nerve I • Olfactory: Test sense of smell with spirits of ammonia • Cranial Nerve II • Optic: Test for visual acuity • read printed material • count fingers at distance • distinguish light from dark • read eye chart

28. Cranial Nerve Assessment • Cranial Nerve II and III • Optic and Oculomotor • Inspect size and shape of pupils • pupils equal & round • Test pupillary response to light • pupils constrict when a light is shined into eye • opposite eye should reflexively constrict (consensual reaction) • record normal response as “PERL” - pupils equal and reactive to light

29. Cranial Nerve Assessment • Cranial Nerve III, IV, VI • Oculomotor, Trochlear, Abducens • Test extraocular movements (EOM) by asking patient to look to the extreme left and then up and down; to the extreme right then up and down with no head movement • movements referred to as the six cardinal • directions of gaze • Oculomotor: pupillary reaction, Trochlear: eye movement, Abducens: lateral eye movement

30. Cranial Nerve Assessment • Cranial Nerve V • Trigeminal • Test motor movement by asking patient to clench teeth while palpating temporal muscle (in front of ear) and masseter muscles (muscles used to raise/lower jaw and assists in mastication or chewing) • Test sensation by touching forehead, cheeks, jaw on each side

31. Cranial Nerve Assessment • Cranial Nerve VII • Facial • Inspect the face at rest and during conversation, noting symmetry, tics, or abnormal movements • Ask patient to raise the eyebrows, frown, show both upper and lower teeth, smile, and puff out both cheeks • Assess strength of facial muscles by asking patient to close eyes tightly so they cannot be opened, and gently attempt to raise the eyelids • Observe for weakness or asymmetry

32. Cranial Nerve Assessment • Cranial Nerve VIII • Acoustic: Assess hearing acuity cover one ear at a time and ask patient to repeat short test words spoken softly and then louder by examiner

33. Cranial Nerve Assessment • Cranial Nerve IX and X • Glossopharyngeal and Vagus • Assess patient’s ability to swallow with ease; to produce saliva; and produce normal voice sounds • Instruct patient to hold breath, and assess for normal slowing of the heart rate • Testing for the gag reflex also will test the cranial nerves • Innervates abdominal viscera • Vagus is the longest cranial nerve

34. Cranial Nerve Assessment • Cranial Nerve XI • Spinal Accessory • Ask patient to raise and lower shoulders and to turn head • Cranial Nerve XII • Hypoglossal • Ask patient to stick out tongue and to move it in several directions

35. Peripheral Nervous System • Spinal Nerves – 31 pairs • Innervate muscles and organsBoth sensory and motor nerves • Autonomic Nervous System • Governs internal organs • Peripheral Nervous System • Sensory Nerves • Dermatomes: areas of sensation on the skin that innervated by different spinal nerve levels • Peripheral Nervous System • Motor Nerves • Myotomes: motor nerves that innervate muscles allowing certain muscle actions

36. Peripheral Nervous System • Sensory Nerves • Dermatomes: areas of sensation on the skin that innervated by different spinal nerve levels • Motor Nerves • Myotomes: motor nerves that innervate muscles allowing certain muscle actions

37. Peripheral Nervous System • The ANS is the self governing division of the nervous system • Comprised of the Parasympathetic and Sympathetic Nervous Systems which are antagonistic to each other but balance each other out • Parasympathetic NS • Carries out normal functions • Sympathetic NS • Takes over in times of stress; works with adrenaline