NURSE-UP INTRODUCTION TO THE NERVOUS SYSTEM

FUNCTIONS OF THE NERVOUS SYSTEM Body s primary communication and control system. Integrates and regulates body function Collects information specialized nervous structures, receptors monitor changes in external and internal environment, stimuli Processes and evaluates information then determines if response required Initiates response to information initiate response via nerves to effectors include muscle tissue and glands

SUBDIVISIONS OF NERVOUS SYSTEM Two major anatomical subdivisions Central nervous system (CNS) brain and spinal cord enclosed in bony coverings Peripheral nervous system (PNS) Everything outside the spinal cord Fig 11.2

CNS AND PNS Central nervous system includes brain and spinal cord brain protected in the skull spinal cord protected in the vertebral canal Peripheral nervous system includes nerves, bundles of neuron processes includes ganglia, clusters of neuron cell bodies

DIVISIONS OF THE NERVOUS SYSTEM Central nervous system

FUNCTIONAL DIVISIONS NERVOUS SYSTEM

TYPES OF NERVE CELLS Neurons Consist of three parts Cell body (soma) of neuron - main part Dendrites branching projections that conduct impulses to cell body of neuron Axon elongated projection that conducts impulses away from cell body of neuron

TYPES OF NERVE CELLS Neurons (cont.) Neurons classified according to function or direction of impulse Sensory neurons: conduct impulses to the spinal cord and brain; also called afferent neurons Motor neurons: conduct impulses away from brain and spinal cord to muscles and glands; also called efferent neurons Interneurons: conduct impulses from sensory neurons to motor neurons; also called central or connecting neurons

CHARACTERISTICS OF NEURONS Excitability responsive to stimulation type dependent on its location most respond only to binding of molecules, neurotransmitters Conductivity electrical charges propagated along membrane can be local and short-lived or self-propagating Secretion release neurotransmitters in response to electrical charges given neuron releasing only one type of neurotransmitter may have excitatory or inhibitory effect on target Extreme longevity most formed before birth still present in advanced age Amitotic mitotic activity lost in most neurons

TYPES OF NERVE CELLS Glia (neuroglia) Types of Glia cells Astrocytes - star-shaped cells that anchor small blood vessels to neurons Microglia - small cells that move in inflamed brain tissue carrying on phagocytosis Ependymal cells help from and circulate cerebrospinal fluid. Oligodendrocytes - form myelin sheaths on axons in the CNS Schwann cells - form myelin sheaths in PNS Satellite cells supply nutrients and support to neurons in PNS

NERVES & TRACTS Nerve - bundle of axons in the PNS Tract - bundle of axons in the CNS White matter brain or cord tissue composed primarily of myelinated axons (tracts) Gray matter brain or cord tissue composed primarily of cell bodies and unmyelinated fibers

NERVES & TRACTS Nerve coverings - fibrous connective tissue Endoneurium - surrounds individual fibers within a nerve Perineurium - surrounds a group (fascicle) of nerve fibers Epineurium - surrounds the entire nerve

ACTION POTENTIALS

SYNAPSES The space between a neuron and where it functionally connects to either another neuron or effector (muscle or gland). The two most common neurotransmitters are Acetylcholine and Norepinephrine

COMPARISON OF NERVES Where a neuron meets another neuron in the PNS its called a ganglion.

Nicotinic CHOLINERGIC RECEPTORS Located in Postsynaptic neurons in ANS ganglia Adrenal medulla Always excitatory Muscarinic Located in All glands, smooth muscle, and cardiac muscle that receive cholinergic innervation Excitatory or inhibitory depending on subclass ADRENERGIC RECEPTORS α (alpha) adrenergic Usually excitatory β (beta) adrenergic Usually inhibitory

Questions Compiled by: D. Leonard Learning Specialist The Academic Support Center @ Daytona State College http://www.daytonastate.edu/asc/ascsciencehandouts.html