The Nervous System

The Nervous SystemLab 8

Sensory Function - detect internal stimuli and external stimuli carried to brain and spinal cord through cranial and spinal nerves Integrative Function - processes sensory info by analyzing and storing and making decisionsperception is conscious awareness of sensory stimuliMotor function NS elicits appropriate motor response by activating effectors (muscles and glands) through cranial and spinal nerves

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Two main subdivisions:Central Nervous System brain and spinal cordPeripheral Nervous System all nervous tissue outside the CNS

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Neurons - nerve cells that provide most of the unique functions of the nervous system, length varies from very short to as long as the body Neuroglia - cells that support, nourish and protect the activities of neurons5

Neuron AnatomyCell body nucleus surrounded by cytoplasmDendrites - receiving or input portions of a neuronAxon - takes nerve impulses toward another neuron, muscle fiber, or a gland cell; joins cell body at axon hillock

6Neuron Classification

Multipolar neurons several dendrites and one axon most neurons in brain and spinal cordBipolar neurons one main dendrite and one axon Unipolar dendrites and one axon fused together to form continuous process

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6 types of Neuroglia8

Oligiodenrocyte - main function is the insulation of axons exclusively in the central nervous system of higher vertebrates (the same function is performed by Schwann cells in the peripheral nervous system).

Astrocytes (also known collectively as astroglia) are characteristic star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical support of endothelial cells which form the blood-brain barrier, provision of nutrients to the nervous tissue, maintenance of extracellular ion balance, and a principal role in the repair and scarring process of the brain and spinal cord following traumatic injuries

Microglia are a type of glial cells that are the resident macrophages of the brain and spinal cord, and thus act as the first and main form of active immune defense in the central nervous system

Satellite cells (syn: mantlecells or amphicytes) are flattened Schwann cells, a type of glial cell, lining the exterior surface of neurons in the peripheral nervous system. Satellite cells also surround neuron cell bodies within ganglia. They are thought to have a similar role to astrocytes in the central nervous system (CNS). They supply nutrients to the surrounding neurons and also have some structural function.

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Nerve Organization

11The Central Nervous System

Brain 12 pairs of cranial nervesSpinal Cord 31 pairs of spinal nervesGanglia (singular ganglion) are masses of neurons outide the spinal cord, usually including the first synapse outside of the spinal cord. A plexus is where several nerves join and branch out. For instance, the brachial plexus includes all the nerves that will be directed into the arm. Sensory receptors are either parts of neurons or specialized cells that monitor changes in the internal or external environment.

12Major Parts of the Brain

The Hypothalamus

Protective Coverings

The dura mater (also rarely called meninx fibrosa, or pachymeninx) is a thick, durable membrane

The pia or pia mater is a very delicate membrane. It is the meningeal envelope which firmly adheres to the surface of the brain and spinal cord. As such it follows all the minor contours of the brain (gyri and sulci). It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of flat cells thought to be impermeable to fluid. The pia mater is pierced by blood vessels which travel to the brain and spinal cord, and its capillaries are responsible for nourishing the brain.

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Oh Once One TakesThe Anatomy Final, Very Good Vacations Are Heavenly Cranial NervesNameNumberFunctionOlfactoryISpecial sensoryOpticIISpecial sensoryOculomotorIIIMotorTrochlearIVMotorTrigeminalVMixed (Both)AbduscensVIMotorFacialVIIMixed (Both)VestibulocochlearVIIISpecial sensoryGlossopharyngeal IXMixed (Both)VagusX Mixed (Both)Accessory XIMotorHypoglossalXIIMotor17Olfactory--sense of smellOptic--visionOculomotor--moves eyeball and upper eyelidTrochlear--controls eyeball movements. SmallestTrigeminal--largest. Three portions. Deals with touch pain and temperature as well as masticationAbduscens--originates in pons. Abduction of the eyeballFacial--taste buds, facial expressionVestibulocochlear--equilibrium and hearingGlossopharyngeal--taste, salivationVagus--proprioception and stretching, swallowing, vocalization, enervates heartAccessory--coordinates head movementsHypoglossal--speech and swallowingThe Spinal Cord

Runs from brain stem to coccyx

31 spinal nervesCervical (C1-C8)Thoracic (T1-T12)Lumbar (L1-L5)Sacral (S1-S5)Coccygeal

Distribution of Spinal NervesCervical plexus (C1-C5)Phrenic nerveBrachial plexus (C5-C8, T1)Radial, median, ulnar nervesLumbar plexus (L1-L4)Obturator and femoral nervesSacral plexus (L4-L5, S1-S4)Sciatic nerveCoccygeal plexus (S4-S5, coccygeal)

Cervical plexus supplies the neckBrachial plexus supplies the arm and upper shoulderLumbar plexus supplies the anterolateral abdomen, lower limbs, and external genitalsSacral plexus supplies the buttocks, perineum, and lower limbsCoccygeal plexus supplies a small area around the coccyx

24Reflex Arc

Reflex arc path followed by nerve impulses that produces a reflex

Sensory receptor--nociceptor, mechanosensor, etcSensory neuron--goes to spinal cordIntegrating center--spinal cordMotor neuronEffector--muscle effected25

Ipsilateral occurs on the same side as the stimulus, contralateral occurs on the opposite sideMonosynaptic--one sensory, one motor, polysynaptic--more than one interneuron--most reflexes are polysynapticPolysynaptic reflex pathways, one or more interneurons connect afferent (sensory) and efferent (motor) signals

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Exam Next WeekSame set up as all previous exams50 60 % Identification w/ matching, multiple choice, T/F and short answerToday in lab:A. Exercise 19-pre-lab activities & activities 1, 2, 3, 4, 5 & 6 and Reviewing your knowledge parts A&B.Activities 2-6 use a reflex hammer.

B. Exercise 21, Lab activity 2: Testing Cranial Nerve function & Reviewing Your Knowledge parts A& B. Record results in Table 21.3. Skip the nerve taste test with sugar &quinine Throw away used tongue depressors and cotton-tipped applicators.