Download Ch 48: Nervous System – part 1

NOTES – UNIT 5 part 1: Nervous System Organization  The nervous system has three overlapping functions: 1) SENSORY: gather information from sensory receptors; detect changes in the external or internal environment 2) INTEGRATION: information from sensory receptors is interpreted and associated with appropriate responses (sensation, memory, perceptions, decisions) 3) MOTOR OUTPUT: conduction of signals from the integration center to effector cells (muscle cells or gland cells)

The Nervous System is Divided into: *CENTRAL NERVOUS SYSTEM (CNS)   *PERIPHERAL NERVOUS SYSTEM (PNS)  nerves communicate motor and sensory signals to and from CNS and rest of body  Made up of _____________________ (ropelike bundles of neurons)

Nervous Tissue- Two Main Classes of Cells:

1) NEURONS (nerve cells):  functional unit of the nervous system Specialized for nerve impulse (action potential) conduction Provide most of the unique functions of the nervous system: sensing, thinking, remembering, controlling muscle activity, regulating glandular secretions  transmit signals from one location to another  made up of:  DENDRITES (“little trees”): receiving/input parts of a neuron  CELL BODY: nucleus surrounded by cytoplasm and typical organelles (rough ER, mitochondria, lysosomes, golgi)  AXON: conducts nerve impulses toward another neuron, muscle fiber, or gland cell –Axons end by dividing into many fine processes called axon terminals –Axon terminals swell into synaptic end bulbs which contain synaptic vesicles storing neurotransmitters  many axons are enclosed by an insulating layer called the  Many-layered covering composed of lipid and protein  _____________________________________________________________ _______________________________________________________________  Schwann cells in the PNS and Oligodendrocytes in the CNS produce myelin sheaths by __________ ___________________________________________________________________________________  Axons with a myelin sheath: myelinated and axons without: unmyelinated  Gaps in the myelin sheath: nodes of Ranvier

3 Types of Neurons or Nerve Cells: 1.__________________________: detect many different types of stimuli & carry information to the brain 2._______________________________: integrates/processes sensory information; axons extend for only a short distance & contact nearby neurons in the brain or spinal cord 3._____________________________: carry information from the brain toward the spinal cord or out of the brain and spinal cord to muscles and glands

2) NEUROGLIAL CELLS (SUPPORTING CELLS)  10 to 50 times more numerous than neurons  provide structure; protect, insulate, nourish, & assist neurons  Even though glia do not generate or conduct nerve impulses, they are actively involved in nervous tissue  In contrast to neurons, ____________________________________________________________in the mature nervous system Example of neuroglial cells: SCHWANN CELLS and OLIGODENDROCYTES Example of neuroglial cell : ____________________________: form connections between neurons; protect neurons from harmful substances; responsible for blood-brain barrier

FUNCTIONS OF THE BLOOD-BRAIN BARRIER 1. Maintain ________________________________________________________for the brain. 2. __________________________________________________________in the rest of the body. 3. _____________________________________________________________that may injure the brain.