BSC 2085 Lab 9: Nervous System PDF

BSC 2085 Lab 9 NERVOUS SYSTEM Hernan Aviles ◼ ORGANIZATION  central nervous system (CNS) ◼ brain and spinal cord ◼ integration and command center  peripheral nervous system (PNS) ◼ cranial and spinal nerves ◼ somatic and autonomic...

BSC 2085 Lab 9 NERVOUS SYSTEM Hernan Aviles ◼ ORGANIZATION  central nervous system (CNS) ◼ brain and spinal cord ◼ integration and command center  peripheral nervous system (PNS) ◼ cranial and spinal nerves ◼ somatic and autonomic ◼ carries messages to and from the spinal cord and brain 2 ◼ PERIPHERAL NERVOUS SYSTEM  somatic nervous system ◼ spinal and cranial nerves ◼ receives sensory information and respond to skeletal muscles ◼ sensory nerves: transmit the information from sensory receptors located in the periphery to the CNS ◼ motor nerves: transmit the commands from CNS to skeletal muscle  autonomic nervous system ◼ autonomic nerves (sensory and motor) ◼ receives sensory information and respond to cardiac muscle, smooth muscle and glands 3 4 ◼ DEVELOPMENT  begins as a tube (neural tube)  cephalic portion: brain  caudal portion: spinal cord  Forebrain ◼ telencephalon (olfactory bulbs, cerebrum, ventricles I, II) ◼ diencephalon (thalamus, hypothalamus, pineal and pituitary glands, optic nerves, III ventricle)  Midbrain ◼ mesencephalon  Hindbrain ◼ metencephalon (cerebellum, IV ventricle) ◼ myelencephalon (medulla oblongata 5 ◼ NEURONS  Nerve cells that conduct impulses (~100 billion in brain, ~100 million in spinal cord)  cell body or soma: nucleus, Nissl bodies (RER)  dendrites: conduct impulses toward the cell body.  axon hillock: portion of the axon that connects to the cell body  axon: conducts impulses away from the cell body to other neurons or effectors ◼ axoplasm: cytoplasm of axon ◼ axolemma: cell membrane of axon  synaptic knobs: terminal ends of axons that form junctions (synapse) with the next cell 6 ◼ AXONS  covered by lipid material (myelin), myelin is formed by oligodendrocytes in the CNS and Schwann cells in the PNS  Schwann cell spirals repeatedly around a single nerve fiber (100 layers), these layers are the myelin sheath.  neurilemma: outermost layer of a Schwann cell  endoneurium: thin sleeve ofconnective tissue surrounded the schwann cell  nodes of Ranvier: gaps between the segments of axons not covered by myelin 7 Neuron Model 8 Neurons (Nerve Cells) 9 Figure 11.4b  MYELINATED AXON NODE OF RANVIER MYELIN 10 ◼ NEURON FUNCTIONAL CATEGORIES  sensory (afferent) neurons: conduct impulses from sensory receptors to the CNS.  motor (efferent) neurons: conduct impulses from CNS to effectors  association neurons (interneurons): conducts impulses from one area of CNS to another Spinal cord (in cross-section) Stimulus 2 Sensory neuron 3 Integration 1 Receptor center 4 Motor neuron 5 Effector Interneuron Skin  motor and association are multipolar neurons (one axon and several dendrites)  sensory are unipolar (one fiber that serves as axon and dendrite)  bipolar (one axon and one dendrite)  anaxonic (many dendrites but no axon) 11 ◼ MYELINATED AND UNMYIELINATED NEURONS  myelinated: organized into bundles called nerve tracts in the CNS and nerves in the PNS  myelinated axons form the white matter (myelin is white) and unmyelinated axons appear gray in color  sensory nerves contain sensory neurons, motor nerves contain motor neurons and mixed nerves contain both 12 ◼ MYONEURAL JUNCTION  contraction of muscles requires the stimulation by motor neurons  cell bodies reside in brain or spinal cord, axons travel to muscles they serve  axon branches, each branch serves one single muscle cell  motor unit: motor neuron and all muscle cells served by the branches of that motor neuron  axon end is separated from the muscle cell (motor end plate) by a small gap (synapse)  binding of acetylcholine (released by the axon) to the motor end plate initiates the contraction  myoneuronal or neuromuscular junction: junction formed by the axon branch and the motor end plate 13 14  NEUROMUSCULAR JUNCTION MOTOR END PLATE MOTOR END PLATE 15 NEUROMUSCULAR JUNCTION 16 17