Anatomy Chapter 13: Nervous Tissue Flashcards Table View


What two organ systems are decidated to maintaining homeostasis? nervous and endocrine systems
How does the endocrine system communicate? chemical messengers secreted into the blood
What are these chemical messengers more commonly known as? hormones
How does the nervous system communicate? electrical and chemical means to send messages very quickly from cell to cell
What is the study of the nervous system? neurobiology
What are the primary subdisciplines of neurobiology? neuroanatomy (study of structure) and neurophysiology (study of function)
What are the 2 major anatomical subdivisions of the nervous system? Central Nervous System (CNS) and Peripheral Nervous System (PNS)
What does the CNS consist of? brain and spinal cord
What protects the brain? the spinal cord? cranium, vertebral column
What makes up the PNS? all the nervous system except the brain and spinal cord; composed of nerves and ganglia
What is a nerve? a bundle of nerve fibers (axons) wrapped in fibrous CT
What is a ganglion? a knotlike swelling in a nerve where the cell bodies of neurons are concentrated
The PNS is divided into ___ and ___ which are each divided into ___ and ___ divisions. sensory and motor divisons; somatic and visceral
The sensory (afferent) division functions to: carry signals from various receptors to the CNS; the pathway that informs the CNS of stimuli in and around the body
The somatic sensory divison carries signals from receptors in: the skin, muscles, bones, and joints
The visceral sensory division carries signals from receptors in: the viscera of the throacic and abdominal cavities
The motor (efferent) division functions to: carry signals from the CNS to the gland and muscle cells that carry out the body's responses
Cells and organs that respond to commands from the nervous system are called: effectors
The somatic motor division carries signals to: the skeletal muscles
This divison produces muscular contractions that are under voluntary contral, as wella s involuntary muscle contractions called: somatic reflexes
The visceral motor division (autonomic nervous system) carries signals to: glands, cardiac muscle, and smooth muscle
The reponses of this system and its effectors are ___ ____. visceral reflexes
The ANS further divides into: the sympathetic division and the parasympathetic division
The sympathetic divsion tends to: arouse the body for action but inhibits digestion
The parasympathetic divsion tends to: adapt the body for energy intake and conservation, stimulates digestion but slows down heartbeat
The functional unit of teh nervous system is the: nerve cell or neuron
What are the 3 fundamental physiological properties of neurons that are necessary to communicate: Excitability, Conductivity, Secretion
What is excitibility/irritability? ability to respond to stimuli, nerurons have developed this to the highest degree
What is conductivity? respond to stimuli by producing traveling electrical signals that quickly reach other cells at distant locations
What is secretion? when electrical signal reaches end of nerve fiber, neuron usually secretes a neurotransmitter to stimulate next cell
What are the 3 general classes of neurons? sensory (afferent) neurons, interneurons, and motor (efferent) neurons
How are sensory/afferent neurons specialized? sepcialized to detect stimuli (light, heath,pressure, chemicals) and to transmit info. about them to CNS
What function do interneurons serve? lie entirely in CNS, recive signals so they process, store, and retrieve info and "make decisions" about how body responds to stimuli
About ___% of human neurons are internuerons. 90
What role do motor/efferent neurons play? send signals to muscle and glad cells, carry out body's responses to stimuli
The control center of the neuron is its: soma or cell body
The soma has __ nucelus/nuclei. 1
The cytoskeleton of the soma consists of a dense mesh of _____ and ____. microtubules and neurofibrils
These compartmentalize the rough ER into dark-staining regions called ____ ____, unique to neurons. Nissl bodies
Nissl bodies are helpful to: identify neurons in tissue sections with mixed cell types
The major cytoplasmic inclusions in a neuron are: glycogen granules, lipid droplets, melanin, and lipofuscin (pushes nucleus to one side)
Soma of neuron usually gives rise to a few thick process that branch into a vast number of ____. dendrives
The dendrites function to; receiving signals from other neurons
How many dendrites does a neuron have? some have one, others have thousands
on one side of teh soma is a mound called the __ ___. axonal hillock
What does the axonal hillock do? axon orignates from
The axon hillock adn the nearby portino of the axon (initial segment) are collectively the: trigger zone b/c this is where teh neuron first generates action potentials
What is an action potential? electrical changes that constitute the nerve signal
What is an axon specialized to do? rapid conductino of nerve signals to points remote from the soma
The axon may give rise to a few branches called __ ___. axon collaterals
The cytoplam in an axon is called ____. The membrane is called the ___. axoplasm, axolemma
A neuron always/can/never has more than one axon. Never has more than one, some neurosn in retina and brain have none.
At the distal end an axon usually has a ____ ____ which is an extensive complex of fine branches. terminal aborization
Each branch of the terminal arborization ends in a __ __. synaptic knob
What is a synaptic knob? a little sweeling that forms a junction/synapse with a muscle cell, gland cell, or another neuron
Neurons are classified structurally into 4 categories: multipolar, bipolar, unipolar, anaxonic
Describe multipolar neurons. 1 axon, 2+ dendrites most common type of neuron, most neurons in brain/spinal cord
Describe bipolar neurons. 1 axon, 1 dendrite
Describe unipolar neurons. one process leading away from soma
Where are unipolar neurons found? carry sensory signals to spinal cord
What are these neurons also called, why? pseudounipolar b/c they start out as bipolar neurons in embryo but processes fuse into 1
What are the names of the two fibers, where do they lead? peripheral fiber-from sources of sensation central fiber- continue to spinal cord
Describe anaxonic neurons. multiple dendrites, no axon communicate over short distances through dendrites, don't produce action potentials
What are the supportive cells of neurons? neuroglia or glial cells
What are their function? protect the neurons and aid their function
What are 6 different kinds of glia? oligodendrocytes. ependymal cells. microglia. astrocytes. schwann cells. satellite cells.
What are oligodendrocytes? resemble octopus. wrap around nerve fiber with their processes. in CNS
What is the spiral wrapping of an oligodendrocyte called? function? myelin sheath, insulates nerve fiber from extracellular fluid and speeds up signal conduction
What are ependymal cells? resemble cuboidal epithelium lining internal cavities of brain/spinal cord, produce quite a bit of CSF
What is CSF? clear liquid that pathes CNS and fills its internal cavities
What are microglia? small macrophages that deveop from monocytes, wanter trhrough CNS and phagocytize foreign matter
Where are microglia highly found? areas damaged by infection, trauma, or stroke
Where are astrocytes found? most abundant glia cells in CNS, cover entire brain surface and most nonsynaptic regions of neurons in gray matter of CNS
What is the function of astrocytes? form supportive framework for NT, form blood/brain barrier, convert blood glucose to lactate and supply to neurons for nourisment
What is the function of astrocytes? (part 2) secrete protein called nerve growth factors, communicate electrically with neurons and my influence future synaptic signaling between neurons
What is the function of astrocytes? (part 3) regulate chemical composition of tissue fluid, form hardened scar tissue adn fill space formerly occupied by neurons (sclerosis)
Where are Schwann cells found? in nerve fibers of PNS
What is the function of Schwann cells? form a sleeve around fibers called neurilemma, also assist in regeneration fo damaged fibers
What are satillate cells? surround neuon cell bodies in ganglia of PNS. little is known about their function
What is a myelin sheath? an insulating layer around a nerve fiber
What makes up in myelin sheath in the CNS? in PNS? CNS - oligodendrocyte PNS - Schwann cell
What is it composition? 20% protein, 80% lipid (phospholipids, glycolipids, cholestrol)
Myelin imparts a __ color to certain regions of nervous tissue. white, like the white matter of the brain and spinal cord
Production of the myelin sheath is called: myelination
The outer layer of the myelin sheath in a Schwann cell is the ____ neurolemma
what are the gaps between the segments of Schwann cells or oligodendrocytes? nodes of ranvier
what are the myelin-covered segments from one gap to the next called? internodes
Many nerver fibers in CNS and PNS are unmyelinated. In the PNS even the unmyelinated fibers are enveloped in Schwann cells. yes
What 2 factors affect the speed of the signal along a nerve fiber? dimater of fiber prescense/abscense of myelin
Singal conduction occurs along surface or deep within axoplam? along surface
What 2 things are required for regeneration of an axon? neurilemma and endoneurium
Schwann cells of neurilemma secret __ ___ ___ that stimjulate regrowth of axon. nerve growth factors
the Schwann cells and endoneurium together form a ___ ___. regeneration tube
What is the function of the regeneration tube? guides growing axon to its destination
CNS neurons can/can't regenerate can't
Since CNS is enclose in ___ it sufferes less traume than the PNS bone
The meeting point betwen a neuron and any other cell is called a ____. synpase
Synapses make ____ ____ (information processing) possible. neural integration
Each synapse is a "decision-making" device that determines where a seconds cell with repons to signals from the first. yes
The nerve before the synapse is the: presynaptic neuron
The nerve after the synapse is the: postsynaptic neuron
A synapse where the presynaptic axon ends at teh dendrite of a postynaptic neuron axodendritic synapse
A synapse where the presynaptic axon ends on the soma of the next cell axosomatic synapse
A synapse where the presynaptic axon ends on the axon of the next cell: axoaxonic synapse
What is a chemical synapse: a junction at which the presynaptic neuron releases a neurotransmitter to stimulate the postsynaptic cell
What is a common neurotransmitter: acetylcholine
Some neurotransmitters are ___ and tend to cause the postsynaptic cell to generate a nerve signal. excitatory
Other neurotransmitters are ___ and suppress responses in the post-synaptic cell. inhibitory
The terminal branch of the presynaptic nerve fiber ends in a swelling call the ___ ___. synaptic knob
The knob is separated from the next cell by the __ __. synaptic cleft
The knob contains membrane-bounded secretory vesicles called ___ ___, which contain ___. synaptic vesicles, neurotransmitters
Neurotransmitters release through the process of ___. exocytosis
The membrane of of the postsynaptic neuron is ___. folded to increase surface area
Another type of synapse, an __ ___, connects some neurons, neuroglia and cardiace and single-unit smooth muscle cells. electrical synapse
What kind of junctions connect the adjacent cells of an electrical synapse? gap junctions
What is the advantage of an electrical synapse? quick transmission, no delay for release/binding of neurotransmitter
What is the disadvantage of an electrical synapse? can't integrate info and make decisions
Neurons function in ensembles called __ ___. neural pools
The interconnections btwn neurons are called: __ __ neural circuits
What are the 4 principle kinds of circuits? diverging circuit, converging circuit, reverberating circuit, parallel after-discharge circuit
What is a diverging circuit? one nerve fiber brances adn synapses with several postsynaptic cells, etc. 1 motor neuron => thousands muscle fibers
What is a converging circuit? input from many sources is funnel to one neuron or neural pool; contraol breathing rate, lots of sources
What is a reverberating circuit? neurons stimulate ea. other in line but one sends back to beginning; diapgraphm and intercostal muscle to make inhale; when stops fire exhale
What is a parallel after-discharge circuit? input neron diverges to stimulate several chains of neurons, eventually all reconverge. sontinued firing after stim. stops
Approximately _ in every 100 live-born infants exhibit major defects in brain development. 1
common among these are ___ ___ ___ such as ___ ___. neural tube defects; spina bifida
Spind bifida occurs when: 1 or more vertebrae fail to form a complete neural arch for enclosure of the spinal cord
The mildest form is called: spina bifida occulta
What is spina bifida occulta? involves only 1 to a few vertebrae and causes no functional problems
What are the external signs of spina bifida occulta? dimple or patch of hairy pigmented skin on lower back
What is a mroe serious kind of spina bifida? spina bifida cystica
What is spina bifida cystica? a sac protrudes from teh spine and may contain parts of the spinal cord and nerve roots, meninges and CSF
What is microcephaly? a neural tube defect where the face is of normal size but the brain and calvaria are abnormally small; mental retardation
What is anencephaly? failure of the rostral end of the neural tube to close, the brain is exposed to the amniotic fluid