Sistem Saraf

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Transcript of Sistem Saraf

Sistem SarafTerminologi Saraf Tisu Neural Neuroglia Neuron

NeurofisiologiSistem Saraf Pusat Sistem Saraf Pinggir Otak Saraf Tunjang Saraf Kranial Saraf Spinal Saraf Refleksi

Kajian tentang saraf. Sistem saraf tersusun oleh berjutajuta sel saraf yang mempunyai bentuk bervariasi. Sistem ini meliputi sistem saraf pusat dan sistem saraf tepi / pinggir.

Organization of the Nervous SystemCentral nervous system - CNS

Brain and Spinal Cord (in dorsal body cavity)Integration and command center interprets sensory input and responds to input Peripheral nervous system - PNS Paired Spinal and Cranial nerves

Carries messages to and from the spinal cord and brain links parts of the body to the CNS

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

Divisions Nervous System

Nervous SystemFunctions:

Sensory Input monitoring stimuli occurring inside and outside the bodyIntegration interpretation of sensory input

Motor Output response to stimuli by activating effector organs

Motor Division: two subdivisionsSomatic Nervous System (voluntary) Somatic motor nerve fibers (axons) that conduct impulses from CNS to Skeletal muscles allows conscious control of skeletal muscles Autonomic Nervous System (ANS) (involuntary) Visceral motor nerve fibers that regulate smooth muscle, cardiac muscle, and glands Two functional divisions sympathetic and parasympathetic

Levels of Organization in the Nervous System

Levels of Organization in the Nervous System

Divisions of Peripheral Nervous SystemSensory Division picks up sensory information and delivers it to the CNS

Motor Division carries information to muscles and glandsDivisions of the Motor Division Somatic carries information to skeletal muscle Autonomic carries information to smooth muscle, cardiac muscle, and glands

PNS - Two Functional DivisionsSensory (afferent) Division Somatic afferent nerves carry impulses from skin, skeletal muscles, and joints to the CNS Visceral afferent nerves transmit impulses from visceral organs to the CNS Motor (efferent) Division

Transmits impulses from the CNS to effector organs, muscles and glands, to effect (bring about) a motor response

Histology of Nerve TissueTwo principal cell types in the nervous system: Neurons excitable nerve cells that transmit electrical signals Supporting cells cells adjacent to neurons or cells that surround and wrap around neuronsCell Types of Neural Tissue neurons neuroglial cells

Supporting Cells: NeurogliaSix types of Supporting Cells - neuroglia or glial cells 4 in CNS and 2 in the PNS. Each has a specific function, but generally they: Provide a supportive scaffold for neurons

Segregate and insulate neurons Produce chemicals that guide young neurons to the proper connections Promote health and growth

Supporting Cells: NeurogliaNeuroglia in the CNS Astrocytes Microglia Ependymal Cells Neuroglia in the PNS Satellite Cells Schwann Cells

OligodendrocytesOutnumber neurons in the CNS by 10 to 1, about the brains mass.

Types of Neuroglial CellsSchwann Cells peripheral nervous system myelinating cell Oligodendrocytes CNS myelinating cell Microglia CNS phagocytic cell Astrocytes CNS scar tissue mop up excess ions, etc induce synapse formation connect neurons to blood vessels Ependyma CNS ciliated line central canal of spinal cord line ventricles of brain

Types of Neuroglial Cells

AstrocytesMost abundant, versatile, highly branched glial cells Cling to neurons, synaptic endings, and cover nearby capillaries

Support and brace neuronsAnchor neurons to nutrient supplies

Guide migration of young neuronsAid in synapse formation

Control the chemical environment (recapture K+ ions and neurotransmitters)

Star Shaped Many functions Control the chemical environment around neurons by buffering K+ and NT

Supporting Cells in the CNS Astrocytes

Exchanges between capillaries and neurons (blood-brain barrier) Nutrient transfer

MicrogliaMicroglia small, ovoid cells with long spiny processes that contact nearby neurons

When microorganisms or dead neurons are present, they can transform into phagocytic cells

Supporting Cells in the CNS Microglia Small oval cells with long thorny processes Monitor the health of neurons Specialized immune cells that phagocytize microorganisms and debris Immune system cells do not have access to CNS

Ependymal CellsEpendymal cells range in shape from squamous to columnar, many are ciliated

Line the central cavities of the brain and spinal column

OligodendrocytesOligodendrocytes branched cells that line the thicker CNS nerve fibers and wrap around them, producing an insulating covering the Myelin sheath

Supporting Cells in the CNS Oligodendrocytes Oligodendrocytes produce the myelin sheath which provides the electrical insulation for some neurons in the CNS25

Schwann Cells and Satellite CellsSchwann cells - surround fibers of the PNS and form insulating myelin sheaths

Satellite cells - surround neuron cell bodies within ganglia

Supporting Cells in the PNS Schwann Cells

Form the myelin sheath around axons in the PNS

Schwann Cell

Regeneration of A Nerve Axon

Neuron Fascicle

Axon Myelin Sheath Node of Ranvier

PerineuriumEpineurium

Neuron

Neurons (Nerve Cells)Highly specialized, structural units of the nervous system conduct messages (nerve impulses) from one part of the body to another Long life, mostly amitotic, with a high metabolic rate (cannot survive more than a few minutes without O2) Structure is variable, but all have a neuron cell body and one or more cell projections called processes.

Generalized Neuron

Neuron Structure

Classification of NeuronsSensory Neurons afferent carry impulse to CNS most are unipolar some are bipolar Interneurons link neurons multipolar in CNS Motor Neurons multipolar carry impulses away from CNS carry impulses to effectors

Neuron ClassificationFunctional Sensory (afferent) transmit impulses toward the CNS

Motor (efferent) carry impulses away from the CNSInterneurons (association neurons) lie between sensory and motor pathways and shuttle signals through CNS pathways

Classification of NeuronsBipolar two processes eyes, ears, nose Unipolar one process ganglia Multipolar many processes most neurons of CNS

Classification of NeuronsStructural Multipolar three or more processes

Bipolar two processes (axon and dendrite)Unipolar single, short process

Unipolar NeuronDendrite (trigger zone) Cell Body Axon

All are sensory afferent Cell bodies are located in the dorsal root ganglia

Bipolar Neuron

Dendrite (trigger zone)

Cell Body

Axon

Location: special senses (smell, vision, hearing)

Multipolar NeuronCell Body Axon Dendrites (trigger zone)

Most common type of neuron Interneurons and motor neurons

Nerve Cell Body (Perikaryon or Soma)Contains the nucleus and a nucleolus

The major biosynthetic centerHas no centrioles Has well-developed Nissl bodies (rough ER) Axon hillock cone-shaped area where axons arise

Clusters of cell bodies are called Nuclei in the CNS and Ganglia in the PNS

ProcessesExtensions from the nerve cell body. The CNS contains both neuron cell bodies and their processes. The PNS consists mainly of neuron processes. Two types: Axons and Dendrites Bundles of neuron processes are called Tracts in the CNS and Nerves in the PNS

DendritesShort, tapering, diffusely branched processes The main receptive, or input regions of the neuron (provide a large surface area for receiving signals from other neurons) Dendrites convey incoming messages toward the cell body These electrical signals are not nerve impulses (not action potentials), but are short distance signals called graded potentials

AxonsSlender processes with a uniform diameter arising from the axon hillock, only one axon per neuron

A long axon is called a nerve fiber, any branches are called axon collateralsTerminal branches distal ends are called the axon terminus (also synaptic knob or bouton)

Generate and transmit action potentials (nerve impulses), typically away from the cell body

Axons: Function

As impulse reaches the axon terminals, it causesneurotransmitters to be released from the axon terminals Movement of substances along axons: Anterograde - toward axonal terminal (mitochondria,

cytoskeletal, or membrane components) Retrograde - away from axonal terminal (organelles

for recycling)

Retrograde

Myelin Multilayered lipid and protein covering formed by Schwann cells around axons Oligodendrocytes in the CNS The covering is the plasma membrane of the Schwann Cell The Schwann Cell can cover more than one axon Insulates axon

Myelin SheathWhitish, fatty (protein-lipoid), segmented sheath around most long axons dendrites are unmyelinated Protects the axon Electrically insulates fibers from one another Increases the speed of nerve impulse transmission

Myelin SheathFormed by Schwann cells in the PNSA Schwann cell envelopes and encloses the axon with its plasma membrane. The concentric layers of membrane wrapped around the axon are the myelin sheath Neurilemma cytoplasm and exposed membrane of a Schwann cell

Myelination of AxonsWhite Matter contains myelinated axons Gray Matter contains unmyelinated structures cell bodies, dendrites

Nodes of Ranvier Areas between Schwann Cells that do not co