1 Nervous System (1).ppt
- 1. PERCEPTION AND COORDINATION Prepared by: Mr. John Robert D. General, RN, RT, MSN
- 2. ANATOMY AND PHYSIOLOGY OF THE NERVOUS SYSTEM
- 3. The major division of the Nervous System: • Central Nervous System • Peripheral Nervous System Major components Of Central Nervous System: • Brain • Spinal Cord The Peripheral Nervous System is composed of: •12 pairs of cranial nerves • 31 pairs of spinal nerves •Somatic nervous system • autonomic nervous system which is further subdivided into sympathetic and parasympathetic fibers.
- 4. FUNCTION OF THE NERVOUS SYSTEM: • control of all motor, sensory, autonomic, cognitive and behavioral activities.
- 5. Neuron a.k.a nerve cells – convey electrical impulses Cell body – metabolic center of the neuron Projections – - dendrites – bring impulses to cell body - axon – carries impulses away from the body
- 6. The basic functional unit of the nervous system is the Neuron. It is composed of a dendrite, a cell body and an axon.
- 7. Neuroglia • Also called Glial cells • Cells that support, insulate and protect neurons • Cannot transport impulses • Have to ability to reproduce
- 8. CNS Neuroglia 1. Astrocytes – have numerous projections that anchor cells to capillaries - help form the blood brain barrier 2. Microglia – spider like cells that clear dead cells and bacteria in the CNS 3. Ependymal cells – ciliated cells lining the brain and spinal cord which help circulate the CSF 4. Oligodendrytes- provide myelin sheaths for CNS nerve cells
- 10. PNS Neuroglia 1. Schwann Cells – myelin sheath around nerve fibers in CNS. Contains neurolemma which is important in fiber regeneration. - separate therefore has gaps called nodes Ranvier which allows impulses to “jump” 2. Satellite cells – protective, cushioning cells
- 11. Nerve Impulse Transmission • Electrochemical process Electrical – within neuron’s membrane Chemical – from one neuron to another • Irritability – the ability to respond to a stimulus and convert it into a nerve impulse • Conductivity – the ability t0 transmit impulse
- 12. Irritability • Stimulus – opens sodium gates - can be light, sound, pressure or neurotransmitter from another neuron • Sodium enters cell via diffusion – DEPOLARIZATION • This initiates an ACTION POTENTIAL or NERVE IMPULSE, which is propagated through out the entire axon. • Sodium gates become impermeable. Potassium goes out of cell restoring negative charge inside of cell. REPOLARIZATION. • Sodium-Potassium Pump later returns the Na outside cells and K inside cell
- 13. Action Potential
- 14. Conductivity • From one neuron to another • Action Potential reaches axon terminal – vesicles release neurotransmitters • Neurotransmitters diffuse across synapse and travel to the dendrite of the receiving neuron. • Myelin sheath – allows for faster conduction • Nodes of Ranvier
- 16. NEUROTRANSMITTERS These are chemical substances that enhance or inhibit nerve impulses. • Acetylcholine (major transmitter of the parasympathetic nervous system) • Serotonin • Dopamine • Norepinephrine(major transmitter of the sympathetic nervous system) • Gamma–aminobutyric acid (GABA) • Enkephalin, endorphin
- 17. NEUROTRANSMITTER SITE FUNCTION ACTION ACETYLCHOLINE (major transmitter of the parasympathetic nervous system) Brain, brainstem, basal ganglia, autonomic nervous system Nerve muscle & muscle transmission. Parasympathetic and preganglionic sympathetic system Usually excitatory, parasympathetic effects sometimes inhibitory (stimulation of heart by vagal nerve) SEROTONIN Medial brainstem, hypothalamus, dorsal horn of the spinal cord Possible onset of sleep, mood control, pain pathway inhibitor in spinal cord Inhibitory, helps control mood and sleep, inhibits pain pathway DOPAMIN Substantia nigra to basal ganglia Complex movements, emotional response regulation, attention Usually inhibits, affects behavior (attention, emotion) and fine movements NOREPINEPHRINE (major neurotransmitter of the Sympathetic Nervous System) Hypothalamus, brainstem, reticular formation, cerebellum, SNS Maintenance of arousal reward system, dreaming sleep, mood regulation Usually excitatory, affects mood and overall activity GAMA- AMINOBUTYRIC ACID (GABA) Spinal cord, cerebellum, basal ganglia, some cortical areas Nerve and muscle transmission possibly 1/3 of brain neurons ENKEPHALIN, ENDORPHIN Thalamus, hypothalamus, spinal cord, pituitary gland Pleasure sensation, reward system, analgesia, released with ACTH (corticotrophin during stress) Excitatory, pleasurable sensation, inhibits pain transmission
- 18. I. CENTRAL NERVOUS SYSTEM ANATOMY OF THE BRAIN 3 Major Areas of the Brain: 1. CEREBRUM 2. BRAINSTEM 3. CEREBELLUM
- 19. 1. CEREBRUM • Consists of two hemispheres (Right and Left hemispheres) that are incompletely separated by the great longitudinal fissure called Sulcus. • The Cerebral Hemispheres are divided into pairs of Frontal, Parietal, Temporal and Occipital lobes.
- 20. 1.A. FRONTAL LOBE • The largest lobe, located in front of the skull • Major functions: - concentration - abstract thought - information storage or memory and motor function - it also contains Broca’s area, critical for motor control of speech. It is also responsible in large part for a person’s affect, judgment, personality and inhibitions.
- 21. 1.B. PARIETAL LOBE • A predominantly sensory lobe located near the crown of the head. • This lobe analyzes sensory information and relays the interpretation of this information to the thalamus and other cortical areas. • It is also essential to a person’s awareness of the body in space, as well as orientation in space and spatial relations.
- 22. 1.C. TEMPORAL LOBE • Contains the auditory receptive areas located around the temple. • This is where Wernicke’s area is located and plays a significant role in higher-level brain function. • It enables processing of words into coherent thought and recognition of the idea behind written or printed words (language).
- 23. 1.D. OCCIPITAL LOBE • The posterior lobe of the cerebral hemisphere located at the lower back of the head. • Responsible for visual interpretation.
- 24. 2. BRAINSTEM • The brain stem is the lowest part of the brain. • It serves as the path for messages traveling between the upper brain and spinal cord but is also the seat of basic and vital functions such as breathing, blood pressure, and heart rate, as well as reflexes like eye movement and vomiting.
- 25. FUNCTIONS OF THE BRAINSTEM STRUCTURES: 2.A. Medulla Oblongata • Cardiac-slowing center • Respiratory center • Cranial nerves IX (Glossopharyngeal), X (Vagus), XI (Accessory), and XII (Hypoglossal) emerge from the medulla, as do portions of cranial nerves VII (Facial) & VIII (Accoustic)
- 26. FUNCTIONS OF THE BRAINSTEM STRUCTURES: 2.B. Pons • Cardiac acceleration and vasoconstriction centers • Pneumotaxic center helps control respiratory pattern and rate • Four Cranial nerves originate here: V (Trigeminal), VI (Abducens), VII (Facial) and VIII (Accoustic)
- 27. FUNCTIONS OF THE BRAINSTEM STRUCTURES: 2.C. Midbrain • contains the cerebral aqueduct or aqueduct of Sylvius • location of periaqueductal gray, which may abolish pain when stimulated • cranial nerve III (Oculomotor) and IV (Trochlear) are located here
- 28. Thalamus • located between the two cerebral spheres. - serves as a major relay center for all sensory information except sound - key area in sensing pain and pain relief.
- 29. Hypothalamus • – regulates the ANS. - controls heart rate, blood pressure, water and electrolyte balance, appetite, body temperature, intestinal motility and body weight. - plays a major part in metabolism.
- 30. Limbic System • has high levels of epinephrine, norepinephrine, and serotonin. • is believed to affect our emotions and impulses such as anger, motivation, stress, pleasure, etc. • has been a key in controlling mood disorders such as depression, mania, and anxiety.
- 31. Reticular Activating System • in charge of our sleep- wake cycle. • contains large amounts of serotonin, the chief neurotransmitter of sleeping. • Increased serotonin induces sleep • decreased serotonin induces wakefulness. • key area in alleviating sleep disorders.
- 32. 3. CEREBELLUM • Receives instantaneous and continuous information about the condition of the muscles, joints and tendons. • Largely responsible for coordination of movement. • It also controls fine movement, balance, position (postural) sense or proprioception, and integration of sensory input.
- 35. STRUCTURES PROTECTING THE BRAIN • The skull protects the brain from injury. Major bones: Frontal, Parietal, Occipital, Temporal • The meninges (fibrous connective tissues that cover the brain and spinal cord) provide protection, support, and nourishment to the brain and spinal cord. - Dura matter - Pia matter - Arachnoid matter
- 36. DURA MATTER • The outermost layer that covers the brain and spinal cord. It is tough, thick, inelastic, fibrous and gray.
- 37. ARACHNOID MATTER • The middle membrane • An extremely thin, delicate membrane that closely resembles a spider web. It appears white because it has no blood supply. This layer contains the choroids plexus, which is responsible for the production of CSF. This membrane also has unique finger-like projections, arachnoid villi, that absorb CSF.
- 38. PIA MATTER • The innermost membrane • A thin, transparent layer that hugs the brain closely and extends into every fold of the brain’s surface.
- 39. CEREBROSPINAL FLUID • A clear and colorless fluid with a specific gravity of 1.007. • It is produced in the Choroid Plexus of the lateral, third and fourth ventricles. • It is an approximately isotonic solution
- 40. CEREBROSPINAL FLUID • Acts as a "cushion" or buffer for the cortex, providing also a basic mechanical and immunological protection to the brain inside the skull. • The cerebrospinal fluid supports the brain and provides lubrication between surrounding bones and the brain and spinal cord.
- 41. CEREBRAL CIRCULATION • The brain receives approximately 15% of the cardiac output, or 750ml per minute. It does not store nutrients and has a high metabolic demand that requires the high blood flow.
- 43. BLOOD-BRAIN BARRIER • This barrier is formed by the endothelial cells of the brain’s capillaries, which form continuous tight junctions, creating a barrier to macromolecules and many compounds. All substances entering the CSF must filter through the capillary endothelial cells and astrocytes. The blood-brain barrier has a protective function but can be altered by trauma, cerebral edema, and cerebral hypoxemia.
- 45. II. PERIPHERAL NERVOUS SYSTEM CRANIALNERVES TYPE FUNCTION I (Olfactory) Sensory Sense ofsmell II (Optic) Sensory Visual acuity& visualfields III(Oculomotor) Motor Muscles thatmove theeye& lid, pupillary constriction,lens accommodation IV (Trochlear) Motor Muscles thatmove theeye(upward& downwardmovementof theeyeball) V (Trigeminal) Mixed Facialsensation,cornealreflex, mastication
- 46. VI (Abducens) Motor Muscles thatmove theeye(lateral movementofeyeballs) VII(Facial) Mixed Facialexpression andmuscle movement,salivation& tearing, taste, sensation inthe ear VIII(Acoustic) Sensory Hearing & equilibrium IX (Glossopha-ryngeal) Mixed Taste,sensation in thepharynx& tongue,pharyngealmuscles,swallowing X (Vagus) Mixed Muscles of pharynx,larynx,andsoft palate;sensation in external ear, pharynx,larynx, thoracic& abdominal viscera; parasympatheticinnervationof thoracicandabdominalorgans
- 47. Remember!!! “On old Olympus’ towering tops, a Finn and German viewed some hops” “Some say marry money but my brother said bad boys marry money” XI(SpinalAccessory) Motor Movementof Sternocleidomastoid& trapezius muscles XII(Hypoglossal) Motor Movementof thetongue
- 48. SPINAL NERVES There are 31 pairs of spinal nerves: • 8 Cervical • 12 Thoracic • 5 Lumbar • 5 Sacral • 1 Coccygeal Each spinal nerve is responsible for the muscle innervation and sensory reception of a given area of the body. It has a Ventral root and a Dorsal root.
- 50. Spinal Cord • is connected to the brain and extends from the foramen magnum to upper lumbar region of vertebral column. • contains 31 pairs of spinal nerve with each nerve having both a dorsal root (for sensation) and a ventral root (for motor). • primarily sends impulses to and from the brain.
- 51. Peripheral Nervous System • Somatic Nervous System – in charge of voluntary muscle movement • Autonomic Nervous System – in charge of involuntary muscle movement
- 52. AUTONOMIC NERVOUS SYSTEM Sympathetic Nervous System “FIGHT OR FLIGHT” “STRESS” Parasympathetic Nervous System “REST AND DIGEST” “PEACE”
- 53. Sympathetic NS Also Adrenergic system Thoracolumbar lumbar b(from T1-L2) Used to handle stress for short periods of time Main neurotransmitter: norepinephrine
- 54. Adrenergic System Beta Adrenergic Alpha Adrenergic Increases heart contraction increases HR Increases renin secretion increases BP mydriasis, constriction of arterioles, inhibits histamine release Decreases BP D/T inhibition of NorEpi release, decreases GI motility Alpha 2 Adrenergic Alpha 1 Adrenergic Beta 2 Adrenergic Beta 1 Adrenergic decreases GI tone and motility bronchodilation Uterine relaxation glycogenolysis Increased blood sugar
- 55. Parasympathetic NS > also called the craniosacral division > originate from CN III, VIII, IX,X and sacral segments S2-S4. > associated with conservation and restoration or energy stores. > Main neurotransmitter: acetylcholine > 2 Types of Receptors – Muscarinic and Nicotinic