*Nerve Tissue

Description:	*Nerve Tissue
Category:	Biology
Created by:	Shyanne on 2009-09-22

Question	Answer
Nerve tissue	Controls and integrates all body activities within limits that maintain life
3 Basic Functions 1)	Sensing changes with sensory receptors; internally and externally
3 Basic Functions 2)	Integration (interpreting, remembering) of those changes in the internal & external environment
3 Basic Functions 3)	Respond (reacting) to those changes/problem with effectors: by muscular contractions (smooth, cardiac & skeletal) and glandular secretions
Major Structures of the Nervous System	Brain, cranial nerves, spinal cord, spinal nerves, ganglia, enteric plexuses, sensory receptors
Nervous System Divisions	CNS, PNS
CNS consists of	Brain & Spinal Cord
PNS consists of	Cranial & spinal nerves that contain both sensory and motor fibers; connects CNS to muscle, glands, and all sensory receptors
Subdivisions of the Peripheral Nervous System	Somatic,Autonomic, Enteric
Somatic NS	Voluntary NS, SNS: Neurons from cutaneous and special sensory receptors to the CNS and motor neurons to skeletal muscle tissues
Autonomic NS	Involuntary Nervous System, sensory neurons from visceral/gut organs to CNS: Motor neurons to smooth and cardiac muscles and glands (starts an action potential)Sympathetic and Parasympathic
Divisions of the Autonomic NS	Sympathetic and Parasympathic
Enteric NS	Involuntary sensory and motor neurons control GI tract: Neurons function independently of ANS & CNS
Nerve Tissue/2 cell types	1. Neurons - propogate action potential2. Neuroglial cells - provide structural and chemical/nutriant support for neurons
Neuron Structure	neurons composed of 3 cell parts; 1) cell body with 2 cellular extentions called processes 2) axon process 3) dendrite process
Neurons propagate action potentials =	Nerve Impulses
Nerve Impulses =	Flow of Ions (sodium and potassium)
Action Potention Flows....	from the dendrite to the cell body to the axon and then to a 1) muscle 2)gland or 3) another neuron (dendrite)
Synapse	Space between axon and effector
Neuron facts	1) Functional unit of nervous system2) Most do not divide/limited number/Die from Disease or Injury3) Have capacity to produce action potential
Neurons are made up of these two things	cell body & cell processes (dendrites and axons)
Nerve fiber	axon or dendrite(cellular process)
Tract	bundle of nerve fibers in central nervous system
Peripheral Nerve	bundle of nerve fibers in peripheral nervous system covered with connective tissue (myelin sheath)
Myelin Sheath	is a lipid(fat) forms the white matter of the brain and spinal cord
Functional Classification of Neurons	1)Sensory/Afferent Neurons2) Motor/Efferent Neurons3) Interneurons/Association Neurons
Sensory/Afferent Neurons	ASCENDING! transport sensory information from skin, muscles, joints, sense organs & viscera to CNS
Motor/Efferent Neurons	DESCENDING!! send motor nerve impulses to muslces & Glands & other neurons
Interneurons/Association Neurons	MORE THAN ANY OTHER!! Connect sensory to motor neurons - 90% of neurons in the body
Neuroglial Cells 6 facts	1) Do not produce action potentials2) half of the volume of the CNS3) Smaller cells than neurons4) 50 times more numerous5) Cells can divide6) rapid mitosis (division) in tumor formation (called gliomas)
Gray matter	nerve cell bodies, dendrites, axon terminals, bundles of un-myelinated axons and neuroglia (gray color)
White matter	myelinated processes (white in color) inside or under the gray matter
cortex =	outer covering
2 places gray matter found	1) in the spinal cord: gray matter forms an H shaped inner core surrounded by white matter2) in the brain: a thin outer shell of gray matter covers the surface & is found in clusters called nuclei inside the CNS
Propagation of Action Potential	An action potential spreads (propagates) over the surface of the axon membrane
2 phases of Action Potential	1) Depolarizatin (influx) - Na(sodium) flows into the neuron2)Repolarization (removal)- K+(potassium) leaves the neuron
What happens when the action potential reaches the end of the neuron?	A neurotransmitter is released (from axon bulb)
The traveling Action Potential is called	Nerve Impulse/AP
Pre-synaptic Neuron	the neuron delivering the neurotransmitter to the next neuron: Action potential reaches the end bulb and Ca channels open. Ca(Calcium) flows inward triggering the release of neurotransmitter.
Post-synaptic Neuron	Neurotransmitter crosses synaptic cleft & binding to receptors on another neuron (more neurotransmitter released = greater effect)One way information transfer!