Notes

Nervous System Functions Coordinate body functions Maintain homeostasis Respond to changing conditions internally and externally Made of 2 parts –Neurons –Neuroglial cells

Neurons (nerve cells) Transmit information in the form of a nerve impulse Different parts of a neuron –Cell body-round area/has nucleolus –Dendrites-branches that receive the signal –Axon-sends the single to the next neuron Nerves-bundles of axons

Neuroglial Cells Provide physical support, insulation, and nutrients for the neurons Protection devices

Organs of nervous system are in 2 groups. Central Nervous System (CNS) –Made of brain and spinal cord Peripheral Nervous System (PNS) –Made of neurons that connect to CNS Have 3 general functions: Sensory Motor Integrative

3 general functions Sensory-sensory receptors are at the end of peripheral neurons –Gather information about changes in and out of the body Example: temperature, light, sound, oxygen levels Integrative-bring all the information together to create perceptions from sensations

3 general functions (cont.) Motor –Effectors-responsive structures that receive impulses Are found outside the nervous system Example: muscle, glands –2 categories Somatic-conscious control (skeletal muscles) Autonomic-unconscious control (heart and smooth muscle)

Neuroglial cells Produce myelin (fat that surrounds the axon) Fills space Framework There are different types of neuroglial cells.

Types of neuroglial in CNS Microglial-support neurons –Phagocytosis of bacteria and cell debris Oligodendrocytes-found along nerve fibers –Provide myelin for myelin sheath (around axon within brain and spinal cord) Astrocytes-between neurons and blood vessels –Support, join parts, help regulate ion and nutrient levels, form scar tissue when injury occurs to the CNS Ependymal cells-cover special brain parts and close spaces between the brain and CNS

Neuroglial in the PNS Schwann cells-create myelin for neurons in the PNS Too many neuroglial cells-cause brain tumors (fast growing gliomas)

Neuron Structure Cell body –Cytoplasm, organelles, cell membrane –Neurofibrils-fine threads –Chromatophilic substance (Nissl bodies)-like rough ER –Nucleolus Dendrites –Short, highly branched, receptors

Neuron structure (cont) Axons –Axon hillock-elevated portion leading into the axon from the cell body –May have side branches –PNS axons-made of Schwann cells that make myelin –Neurilemma-covering that surrounds myelin sheath –Nodes of Ranvier-gaps in between myelin sheath of axon Myelinated in CNS are called white matter Unmyelinated in CNS are called gray matter –Axons can regenerate in PNS because of neurilemma –CNS are myelinated by oligodendrocytes-no neurilemma so can’t regenerate

Label the picture on your notes.

Groupings-Structural trigger point-sensitive region of axon;where nerve impulse begins to be sent down axon Multipolar-one axon and many dendrites (brain and sc) Bipolar-1 axon, 1 dendrite (eyes, nose, ears)

Structural Differences (cont) Unipolar neuron-one axon, no dendrites –Dendrite near peripheral body –Other part connected to brain or spinal cord –Cell bodies of these are bunched to form ganglia Outside the brain or spinal cord

Functional Groupings Sensory (afferent)-carry impulse from peripheral into CNS –Specialized receptor ends on dendrite tips –Dendrites are closely associated with receptor cells in skin or in sensory organs –Unipolar, some bipolar Interneurons-in brain and spinal cord –Transmit impulses from 1 to another by forming links with other neurons –multipolar

Functional groupings (cont) Motor neurons-efferent –Multipolar –Carry impulse out of CNS to the effectors –Stimulate muscle and glands to respond