Nervous Sys Review Flashcards
- Sensory input
- integration
- motor output
functions of the nervous system
Info gathered by sensory receptors about internal and external changes
sensory input
interpretation of sensory input
integration
activation of effector organs (muscles and glands) produces a response
motor output
this system includes: brain and spinal cord, integration and command center
Central Nervous System
paired spinal and cranial nerves carrying msgs to and from the CNS
PNS : peripheral nervous system
- sensory_(afferent) division
- Somatic afferent fibers—convey impulses from skin, skeletal muscles, and joints
- Visceral afferent fibers—convey impulses from visceral organs
- motor_(efferent) division
* Transmits impulses from the CNS to effector organs
2 functional divisions of the PNS
- Somatic (voluntary ) nervous system
* Conscious control of skeletal muscles - Autonomic (_involuntary ) nervous system (ANS)
- Visceral motor nerve fibers
- Regulates smooth muscle , cardiac muscle, and glands
- Two functional subdivisions
- sympathetic
- parasympathetic
motor divison of PNS
- neurons- excitable cells that transmit signals
- neuroglia- supporting cells
- astrocytes (CNS)
- microglia (cNS)
- ependymal (CNS)
- oligodendrocytes(CNS)
- satellite cells (PNS)
- schwann cells (PNS)
2 principal cell types
- Most abundant , versatile , and highly branched glial cells
- Cling to neurons , synaptic endings, and capillaries
- Support and brace neurons
- Help determine capillary permeability
- Guide migration of young neurons
- Control the chemical environment
- Participate in information processing in the brain
astrocytes
- Small, ovoid cells with thorny processes
- Migrate toward injured neurons
- Phagocytize microorganisms and neuronal debris
microglia
- Range in shape from squamous to columnar **
- May be ciliated
- Line the central cavities of the brain and spinal column
- Separate the CNS interstitial fluid from the cerebrospinal fluid in the cavities
ependymal cells
- Branched cells
- processes wrap CNS nerve fibers, forming insulating myelin sheaths
oligodendrocytes
- surround neuron cell bodies in the PNS
satellite cells
- Surround peripheral nerve fibers and form myelin sheaths
- Vital to regeneration of damaged peripheral nerve fibers
schwann cells (neurolemmocytes)
- Electrical signaling
- Cell-to-cell interactions during development
plasma membrane functions of neurons
- biosynthetic center of a neuron
- Spherical nucleus with nucleolus
- Well-developed golgi_ apparatus
- rough ER called nissl bodies (chromatophilic substance)
- axon hillock
- clusters of cell bodies are called nuclei in the CNS, ganglia in the Pns
cell body (soma)
cone shaped area from which axon arises
axon hillock
- tracts in the CNS
- nerves in the CNS
these are bundles of processes
- Short, tapering, and diffusely branched
- receptive(input) region of a neuron
- Convey electrical signals toward the cell body as graded potentials
dendrites
- long axon - nerve fibers
- occasional branches -axon callaterals
- numerous terminal branches - telodendria
- knoblike axon terminals - synaptic knobs or boutons
- secretory region of neuron
- release neurotransmitters to excite or inhibit other cells
the axon
- conducting region of neuron
- generates and transmits nerve iimpulses(action potentials) away from the cell body
axons functions
molecules and organells are moved along axons by motor molecules in 2 directions :
- anterograde- toward axonal terminal
- ex.mitochondria, membrane components, enzymes
- retrograde- toward cell body
- ex. organelles to be degraded, signal molecules, viruses, adn bacterial toxins
segmented protien lipoid sheath around most long diameter axons functioning to
- protect/insulate the axon
- increase speed of nerve impulse transmission
myelin sheath
peripheral bulge of Schwann cell cytoplasm
neurilemma
- myellin sheath gaps between adjacent Schwann cells
- Sites where axon collaterals can emerge
nodes of ranvier
- Formed by processes of oligodendrocytes , not the whole cells
- Nodes of ranvier are present
- No neurilemma
- Thinnest fibers are unmyelinated
myelin sheaths in CNS
- schwann cells
- neurilemma
- nodes of ranvier
myelin sheaths in PNS
Dense collections of myelinated fibers
white matter
Mostly neuron cell bodies and unmyelinated fibers
gray matter
3 types of structural classifcation of neurons
- multipolar
- bipolar
- unipolar (pseudounipolar)
- 1 axon and several dendrites
- most abundant
- motor neurons and interneurons
multipolar neuron
- 1 axon and 1 dendrite
- rare retinal neurons
bipolar neurons
- single, short process that has two branches:
- peripheral process—more distal branch, often associated with a sensory receptor
- Central process—branch entering the CNS
unipolar (pseudounipolar)
- sensory (afferent) -transmits impulses from sensory receptors toward the CNS
- motor(efferent)- carry impulses from the CNS to effectors
- interneurous(association)- shuttle signals thru CNS pathways
functional classifications of neurons
- NUERONS are highly irritable
- Respond to adequate stimulus by generating an action potential (nerve impulse; traveling action potential)
- Impulse is always the same REGARDLESS of stimulus
neuron function
Proteins serve as membrane ion channels
Two main types of ion channels:
- leakage(nongated) channels—always open
- Gated channels (three types):
- Chemically gated (ligand-gated) channels—open with binding of a specific neurotransmitter
- Voltage-gated channels—open and close in response to changes in membrane potential
- Mechanically gated channels—open and close in response to physical deformation of receptors
role of membrane ion channels
______ _______changes when:
- Concentrations of ions across the membrane change
- Permeability of membrane to ions changes
membrane potential
changes in emmebrane potential are signals used to receive, integrate, and send info
- 2 types of signals are:
- graded potentials -incoming short distance signals
- action potentials- long distance signals of axons
____ ____are classified according to:
- Diameter
- Degree of myelination
- speed of conduction
nerve fibers
Group _____ fibers
Large diameter, myelinated somatic sensory and motor fibers
Group ____ fibers
Intermediate diameter, lightly myelinated ANS fibers
Group ____ fibers
Smallest diameter,unmyelinated ANS fibers
A, B, C
a junction that mediates info transfer from one neuron to another or to an effector cell
- presynaptic neuron—conducts impulses toward the synapse
- postsynaptic neuron—transmits impulses away from the synapse
the synapse
- Axodendritic—between the axon of one neuron and the dendrite of another
- Axosomatic—between the axo_ of one neuron and the soma of another
Less common types:
- axoaxonic(axon to axon)
- Dendrodendritic (dendrite to dendrite)
- dendrosomatic_(dendrite to soma)
types of synapses
electrical synapses are less cmmon than chemical
- neurons are electrically couple joined by gap junctions
- communication is very rapid whetierh uni/bidirectional
- important in embryonic nervous tissue and some brain regions
chemical synapses sepcialized for release and reception of neurotransmitters and composed of
- presnpatic terminal of the presynaptic neurons containing synatpic vesicles
- postsynaptic region on the postynaptic neuron
difference between electrical and chemical synapses
- fluid filled space separating the presynaptic and postysynaptic neurons
- prevents nerve impulses from direectly passing form 1 neuron to the next
synaptic cleft
________ ______ is terminated by
- degradation by enzymes
- reuptake by astrocytes or axon terminal
- Diffusion away from the synaptic cleft
neurotransmitter effect
The rate-limiting step of neural transmission–neurotransmitter must be released, diffuse across the synapse, and bind to receptors (0.3-5.0ms)
synaptic delay
- Most neurons make two or more neurotransmitters, which are released at different stimulation frequencies
- 50 or more neurotransmitters have been identified
- Classified by chemical structure and by function
neurotransmitters
- Released at neuromuscular junctions and some ANS neurons
- Synthesized by enzyme choline acetyaltransferase
- degraded by the enzyme acetylcholinesterase (AChE)
acetycholine
- 3 to 40 amino acids
- Present in CNS and PNS; some function as hormones
- Excitatory and inhibitory; depending on receptor
- enkphalins, endorphins, dynorphins , substance P
- opioid peptides= thought to be natural painkillers
neuropeptides