1 OrgansOrgans –Brain, Spinal Cord (CNS), and Nerves (PNS) FunctionFunction –Integration of all parts – organs - tissues - cells –Allows control of parts to enable unification: communication - control - integration - homeostasis - survival Chapter 10 Nervous System

2 Cell Types of Neural Tissue Neurons Neuroglial cells

3 Divisions of the Nervous System Central Nervous System brain spinal cord Peripheral Nervous System nerves cranial nerves spinal nerves

4 Neuron Structure Soma

5 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) Neurons

6 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

7 Divisions Nervous System

8 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

9 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

10 Myelination of Axons White Matter contains myelinated axons Gray Matter contains unmyelinated structures cell bodies, dendrites

11 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 Myelination of Axons

12 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 No known cure Multiple Sclerosis

13 Reflex Arc

14 Conduction of an impulse to and from the brain and spinal cord. –Types –Types : Two neuron arc -Two neuron arc - simplest form –Consists of afferent and efferent neurons Three neuron arc -Three neuron arc - must common –Consists of afferent, interneurons, and efferent Reflex Arc

15 Two Neuron Arc

16 Three Neuron Arc

17 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).

18 Synaptic Transmission Neurotransmitters are released when impulse reaches synaptic knob

19 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 Brain and Cord Coverings

20 Meninges

21 Meninges

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23 Spinal Cord

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) Spinal Cord

25 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 are very painful Spinal Nerves

26 Spinal nerves

27 Dermatomes

28 Spinal nerves Broken neck at 3, 4, or 5 vertebrae = damage to phrenic nerve –This nerve controls the diaphragm –Without artificial respiration, patient will die. Spinal Nerves

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30 Size –3 pounds –Larger in men than women brains-compare/ brains-compare/ –Larger in young than old –Full size by age 18 –Contains 100 billion neurons Brain

31 Brain

32 Divisions of the Brain Brainstem –Midbrain –Pons –Medulla oblongata Cerebellum Diencephalon Cerebrum

33 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. Divisions of the Brainstem

34 Pons –Above the medulla oblongata –Function Helps regulate respiration gases, chewing, saliva secretion, hearing Divisions of the Brainstem

35 Midbrain –Located above the pons and below the cerebrum –Function Reflex center: eye movements, hearing Divisions of the Brainstem

36 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 Cerebellum

37 Located between the midbrain and cerebrum Consists of the hypothalamus and thalamus –Hypothalamus –Hypothalamus: regulator of autonomic activities; mind-body link (tears); maintains water balance, waking state, appetite, and body temperature –Thalamus –Thalamus: recognizes sensations of pain, temp., and touch; relays sensory impulses to cerebrum; associates sensory impulses to emotions, arousal or alerting mechanism Diencephalon

38 Cerebrum

39 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 Cerebrum

40 Five Lobes –Frontal - forehead –Parietal - posterior top –Temporal - temples –Occipital - posterior base –Insula - hidden from view Cerebrum

41 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 Emotions Cerebrum

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