E3 Ch. 12 Flashcards
what are the 3 overlapping functions of the nervous system (NS)
- sensory receptors monitor changes inside/outside the body
- processes and interprets sensory input
- dictates a response by activating effector organs
stimulus
changes detected inside or outside the body
sensory input
information gathered by receptors
integration
term for interpreting input
motor output
the response
what is the CNS composed of
brain and spinal cord
function of the CNS
integrating and command center
what does the PNS consist of
nerves extending from brain and spinal cord (cranial nerves, and spinal nerves)
ganglia
clusters of neuronal cell bodies
sensory
(afferent) signals picked up by sensory receptors, carried by nerve fibers of PNS to the CNS
motor
(efferent) signals carried away from CNS, innervates muscle and glands
what are the main divisions of sensory input and motor output
somatic and visceral body regions
what are the 4 main subdivisions of sensory input and motor output
somatic sensory, visceral sensory, somatic motor, and visceral motor (autonomic nervous system)
where do somatic sensory receptors spread to
receptors spread throughout outer tube of body
types of sense somatic sensory receptors receive
touch, pain, vibration, pressure, tempt.
proprioceptive senses
detect stretch in tendons and muscles, body senses position and movement of body in space
what are special somatic senses
hearing, balance, vision, smell
what are the general visceral senses
stretch, pain, tempt, nausea, and hunger, widely felt in digestive and urinary tracts, and reproductive organs
what are some special visceral senses
taste and smell
what do general somatic motor signal
contraction of skeletal muscles, under our voluntary control
brachial motor
typical skeletal muscles derived from somitomeres
what does visceral motor regulate
contraction of smooth and cardiac muscles, makes up autonomic NS
what are the two main cell types found in nervous tissue
neurons and support cells (neuroglial cells in CNS)
function of neurons
transmit electrical signals
function of support cells
surround and wrap neurons
describe the neuron
basic structural unit of the NS, specialized cells conduct electrical impulses along the PM (nerve impulse)
list the special characteristics of neurons
longevity, do not divide, high metabolic rate
chromatophilic bodies (nissl bodies)
clusters of rough ER and free ribosomes, function to renew membranes of the neurons
neurofibrils
bundles of intermediate filaments, form network b/t chromatophilic bodies
where are most neuronal cell bodies located
w/ in the CNS
what are the neuronal cell bodies in the PNS called
ganglia
dendrites
extensively branching from the cell body, transmit electrical signals toward the cell body
where do chromatophilic bodies extend to
into the basal part of dendrites and to the base of the axon hillock, function as receptive sites for receiving signals from other neurons
axon
impulse generater/conductor, transmits impulses away from cell body
what type of filaments are found in the axon and what do they provide
neurofilaments, actin microfilaments, and microtubules, provide strength along length of axon aid in axonal transport
axonal transport
transport of substances to and from the cell body
terminal arboration (telodendria)
multiple branches at end of axon
terminal boutons (axon terminals)
end knobs found at the ends of terminal arboration
where are nerve impulses generated
at the initial segment of the axon, conducted along axon to the terminal boutons
what is released at the terminal boutons
neurotransmitters from vesicles
synapses
site at which neurons communicate, most info. passed though chemical messenger
presynaptic neuron
conducts signal toward a synapse
postsynaptic neuron
transmits electrical activity away from a synapse
axodendritic
b/t axon terminals of one neuron and dendrites of another, most common type of synapse
axosomatic
b/t axons and neuronal cell bodies
synaptic vesicles on presynaptic side
membrane-bound sacs containing neurotransmitters, mitochondria abundant in axon terminals
synaptic cleft
separates PM of the two neurons
what are the 3 structural classifications of neurons
multipolar, bipolar, unipolar
multipolar neurons
possess more than two processes, numerous dendrites and one axon
bipolar neurons
possess two processes, rare neuron, found in some special sensory organs
unipolar (pseudounipolar)
possess one short, single process, start as bipolar neurons during development
what is the functional classification for neurons
according to the direction the nerve impulse travels relative to the CNS
what are 3 types of neurons
sensory, motor, interneurons
function of sensory neurons
transmit impulses toward CNS
what do the short, singles process of sensory neurons divide into
central process: runs centrally into the CNS, most are unipolar
peripheral process: extends peripherally to the receptors
function of motor (efferent) neurons
carry impulses away from CNS to effector organs, most are multipolar
interneurons
multipolar, lie b/t motor and sensory neurons, confined to the CNS
where are the 6 types of neuroglia found and what is their function
4 in CNS
2 in PNS
provide supportive functions for neurons and cover non synaptic regions of the neurons
function of astrocytes
keeps capillaries and neurons close, wraps around each and regulates which substances get released to neurons
what are microglia
smallest and least abundant glial cell, phagocytes-macrophages of CNS, engulf invading microorganisms/dead neurons.
where are microglia derived from
blood cells called monocytes
ependymal cells
line central cavity of spinal cord and brain, bear cilia-help circulate cerebrospinal fluid
oligodendrocytes
wrap their cell processes around axons in CNS, produce myelin sheaths in CNS
what are the different types of neuroglia in the CNS
astrocytes, microglia, ependymal cells, and oligodendrocytes
what are the different types of neuroglia in the PNS
satellite cells, and schwann cells
satellite cells
surround neuron cell bodies w/in ganglia
schwann cells (neurolemmocytes)
surround axons in the PNS, form myelin sheath around axons of the PNS
describe myelin sheaths
segmented structures composed of lipoprotein myelin, surround thicker axons forming an insulating layer that prevents leakage of electrical current, and increases speed of impulse conduction
myelin sheaths in the PNS are formed by what?
schwann cells
neurilemma
outer collar of perinuclear cytoplasm, material external to myelin layers
which types of axons (thin or thick) is myelinated and non-myelinated
thick= myelinated
thin=non-myelinated
where do oligodendrocytes form myelin sheaths
CNS
nerves
cable like organs in PNS consisting of numerous axons wrapped in connective tissue, most contain myelinated/nonmyelinated sensory and motor axons, which are surrounded by schwann cells
endoneurium
layer of delicate connective tissue surrounding the axon
perineurium
connective tissue wrapping surrounding a nerve fascicle
nerve fascicles
group of axons bound into bundles
epineurium
whole nerve is surrounded by tough fibrous sheath
what is gray matter composed of
primarily of neuronal cell bodies, dendrites, non-myelinated axons, surrounds white matter of CNS in cerebral cortex and cerebellum
what is what matter composed of
myelinated axon, lies external to gray matter of CNS, consists of axons passing b/t specific regions of CNS
tracts
bundles of axons traveling to similar destinations
what do afferent PNS fibers respond to
sensory stimuli
what do efferent PNS fibers do
transmit motor stimuli from CNS muscles and glands
what re the nerves of the CNS composed of and function
composed of interneurons that receive sensory info, direct/transport info to specific CNS regions, and initiate appropriate motor responses
reflex arcs
simple chains of neurons, responsible for reflexes, determine structural plan of the NS
reflexes
rapid, autonomic motor responses that can be visceral or somatic
what are the 5 parts to the reflex arcs
- receptor- site where stimulus acts
- sensory neuron- transmits afferent impulses to CNS
- integration center-consists of one or more synapses in the CNS
- motor neuron-conducts efferent impulses from integration center to affecter
- effector-muscle or gland cell
monosynaptic reflex
“knee-jerk reflex” simplest and fastest of all reflexes, has just one synapse
polysynaptic reflex
one or more interneurons part of pathway, w/drawl reflexes, interneurons signal motor neuron to contract muscles involved
diverging circuit
one presynaptic neuron synapses w/ several other neurons
converging circuit
many neurons synapse on a single postsynaptic neuron
reverberating circuit
circuit that receives feedback via a collateral axon from a neuron in the circuit
list the different types of neuronal circuits
diverging, converging, and reverberating
list the different types of processing
serial and parallel processing
serial processing
neurons pass a signal to a specific destination along a single pathway from one to another
parallel processing
input is delivered along many pathways; a single sensory stimulus results in multiple perception
multiple sclerosis
autoimmune disease where immune system attacks myelin around axons in CNS, cause incompletely understood
neuronal regeneration
injuries may cause permanent dysfunction if axons alone are destroyed, cell bodies often survive and can regenerate axons
neuronal regeneration in the PNS
macrophages invade and destroy axon distal to injury, axon filaments grow peripherally from inured site, partial recovery sometimes possible
neuronal regeneration in the CNS
neuroglia never form bands to guide regrowing axons and may hinder axon growth w/ growth-inhibiting chemicals, no effective regeneration after injury to the spinal cord and brain
where does nervous system develop from
dorsal ectoderm, invaginates to form neural tube and neural crest, tube walls being as neuroepithelial cells which later divide and become neuroblasts
