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Chapter 10 Nervous System • Organs – Brain, Spinal Cord (CNS), and Nerves (PNS) • Function – Integration of all parts – organs - tissues cells – Allows control of parts to enable unification: communication - control 1 integration - homeostasis - survival Chapter 10 Nervous System Cell Types of Neural Tissue • Neurons • Neuroglial cells 2 Divisions of the Nervous System • Central Nervous System • brain • spinal cord • Peripheral Nervous System • nerves • cranial nerves • spinal nerves 3 Neuron Structure Soma 4 Neurons Structure: • Cell body - Soma • Axon - sends messages away from soma • Dendrite - receives messages from axon to soma. Types of Neurons: • Afferent (sensory) - to cord or brain • Efferent (motor) - away from cord or brain • Interneurons (synapse between 1 and 2) from afferent to efferent (from sensory to motor) 5 Classification of Neurons – Functional Differences Sensory Neurons • afferent • carry impulse to CNS Interneurons • link neurons • in CNS Motor Neurons •carry impulses away from CNS • carry impulses to effectors 6 Divisions Nervous System 7 Divisions of Peripheral Nervous System Sensory Division • picks up sensory information and delivers it to the CNS Motor Division • carries information to muscles and glands Divisions of the Motor Division • Somatic – carries information to skeletal muscle • Autonomic – carries information to smooth muscle, cardiac muscle, and glands 8 Functions of Nervous System Sensory Function • sensory receptors gather information • information is carried to the CNS Integrative Function • sensory information used to create • sensations • memory • thoughts • decisions Motor Function • decisions are acted upon • impulses are carried to effectors 9 Myelination of Axons White Matter • contains myelinated axons Gray Matter • contains unmyelinated structures • cell bodies, dendrites 10 Myelination of Axons • Unmyelinated fibers conduct impulses slower. • Myelinated fibers conduct impulses faster – Nodes of Ranvier (short region of exposed axon between Schwann cells on neurons) – The more myelin the faster the impulse 11 Multiple Sclerosis • • • • Most common disease of the nervous system Loss of myelin sheath Hard plaque lesions replace myelin Nerve conduction is impaired and weakened, loss of coordination, visual impairment and speech disturbances. • Most common in women between age 20-40 • No known cure 12 Reflex Arc 13 Reflex Arc • Conduction of an impulse to and from the brain and spinal cord. – Types: • Two neuron arc - simplest form – Consists of afferent and efferent neurons • Three neuron arc - must common – Consists of afferent, interneurons, and efferent 14 Two Neuron Arc 15 Three Neuron Arc 16 The Synapse •Nerve impulses pass from neuron to neuron at synapses •Under normal circumstances, the movement of the electrical impulse down the length of a nerve is very fast, on the order of 115–197 ft/sec (35–60 m/sec). 17 Synaptic Transmission Neurotransmitters are released when impulse reaches synaptic knob 18 Brain and Cord Coverings • Bone is outer cover – Brain - Cranium – Spinal cord - Vertebrae • Meninges - inner cover – Dura Mater - outer, white fibrous tissue – Arachnoid Membrane - cobwebby, middle – Pia Mater - adheres to brain, transparent • Meningitis is inflammation of meninges 19 Meninges 20 Meninges 21 22 Spinal Cord 23 Spinal Cord • 17 - 18 in. in length • Two bulges – Cervical region - sends nerves to upper limbs – Lumbar region - sends nerves to lower limbs • Gray Matter – Inner core, looks like an H in cross section, made of interneurons and motor neuron somas • White Matter – Surrounds gray matter, consists of nerve fibers in bundles (axons and dendrites) 24 Spinal Nerves • 31 pairs - they are numbered according to where they are located. • Emerge from cord through foramen of vertebrae. • Each nerve level attaches to a body section – Dermatone - patches of skin that correspond to each nerve. • Herpes Zoster - (causes chicken pox and shingles) lies dormant at the ends of nerves. – Causes eruptions of red swollen patches which are25 very painful Spinal nerves 26 Dermatomes 27 Spinal Spinal nerves Nerves • Broken neck at 3, 4, or 5 vertebrae = damage to phrenic nerve – This nerve controls the diaphragm – Without artificial respiration, patient will die. 28 29 Brain • Size – 3 pounds – Larger in men than women • http://www.cbsnews.com/2100-500165_162-6890474.html • http://www.cbsnews.com/news/size-matters-how-male-femalebrains-compare/ – Larger in young than old – Full size by age 18 – Contains 100 billion neurons 30 Brain 31 Divisions of the Brain • Brainstem – Midbrain – Pons – Medulla oblongata • Cerebellum • Diencephalon • Cerebrum 32 Divisions of the Brainstem • Medulla Oblongata – – – – Most vital part of the brain Injury or disease proves fatal Lowest part of brainstem Function • Vital centers - cardiac, dilates blood vessels (drops and increases blood pressure), respiratory • Nonvital centers - vomiting, coughing, sneezing, hiccupping, swallowing. 33 Divisions of the Brainstem • Pons –Above the medulla oblongata –Function • Helps regulate respiration gases, chewing, saliva secretion, hearing 34 Divisions of the Brainstem • Midbrain – Located above the pons and below the cerebrum – Function • Reflex center: eye movements, hearing 35 Cerebellum • Second largest part of the brain • Function – Maintains equilibrium – Helps control posture – Smoothes movements instead of being jerky, trembling or uncoordinated • Diseases (hemorrhage, tumor) – Cause ataxia – loss of muscle coordination • Diagnose with a finger to nose test – Tremors – Disturbances of walk and balance 36 Diencephalon • Located between the midbrain and cerebrum • Consists of the hypothalamus and thalamus – Hypothalamus: regulator of autonomic activities; mind-body link (tears); maintains water balance, waking state, appetite, and body temperature – Thalamus: recognizes sensations of pain, temp., and touch; relays sensory impulses to cerebrum; associates sensory impulses to 37 emotions, arousal or alerting mechanism Cerebrum 38 Cerebrum • Largest part of the brain • Consists of two halves and 5 lobes – Right hemisphere • Spatial abilities - see whole picture – ability to mentally manipulate 2-dimensional and 3-dimensional figures. – Left hemisphere • Analytical skills 39 Cerebrum • Five Lobes – Frontal - forehead – Parietal - posterior top – Temporal - temples – Occipital - posterior base – Insula - hidden from view 40 Cerebrum • Function – Sensory: visual and auditory – Motor ability: movement of muscles – Integrative ability: • Ability to receive sensory impulses and send motor impulses. • Consciousness: state of awareness • Memory: major mental activity • Use of language: ability to speak and write words and understand words 41 • Emotions 42