ch 12 - nervous tissue Flashcards
what does the nervous system include?
brain
spinal cord
receptors
nerves
basic functional units of the nervous system are called
neurons
cells in the nervous tissue
neurons: for intercellular communication
neuroglia: support and protect neurons
central nervous system
brain and spinal cord
CNS function
peripheral nervous system (PNS)
all nervous tissue outside the central nervous system
PNS function
delivers sensory info to the CNS
nerves
bundles of axons w/ associated connective tissues and blood vessels
cranial nerves
connect to brain
spinal nerves
connect to spinal cord
subdivisons of PNS
somatic and autonomic nervous system
functional divisions of nervous system
afferent and efferent
afferent (to bring toward) division
carries sensory info to the CNS from receptors in peripheral tissues and organs to the CNS
receptors
structures that detect stimuli
efferent division
carries motor commands from the CNS to effectors
effectors
muscles, glands, and adipose tissue which respond to motor comands
somatic nervous system (SNS)
controls skeletal muscle ontractions
autonomic nervous system (ANS)
controls smooth muscle, cardiac muscle, adipose tissue, and glands
- involuntary
enteric nervous system
-part of ANS
- initiates and coordinates local visceral reflexes
4 general regions of neuron
cell body
dendrites
axon
telodendria
perikayron
cytoplasm of neuron
cytoskeleton contains
neurofilaments
neurotibules
neurofibrils
axolemma
plasma membrane of axon
initial segment
1st segment of axon
axon hillock
thick region that attachs the initial segment to the cell body
collaterals
branches of the axon
telodendria
fine branches of distal axon or collaterals
axon terminals
expanded tips of the telodendria
axonal transport
movement of materials between the cell body and axon terminals
structural classification of neurons
anaxonix, bipolar, unipolar, and multipolar
anaxonic neurons
small, with many dendrites and no obvious axon
bipolar neurons
have one dendrite and one axon
unipolar neurons
the axon and the dendrites are continuous, and the soma is off to the side
multipolar neurons
have one long axon and 2 or more dendrites
functional classifications of neurons
sensory/afferent
motor neurons
interneurons
sensory (afferent) neurons
carry info from receptors to CNS
- somatic sensory neurons
- visceral sensory neurons
types of sensory receptors
interoceptors - give information about the internal organs
exteroceptors - detecting information from outside the body (5 senses)
proprioceptors - awareness of joints
motor neurons
carry instructions from the CNS to peripheral effectors via efferent fibers
- somatic and visceral motor neurons
interneurons
neurons located between sensory and motor neurons which integrate the sensory information and coordinate motor commands
types of neuroglia in CNS
astrocytes
ependymal cells
oligodendrocytes
microglia
types of neuroglia in PNS
satellite cells
schwann cells
astrocytes
- most numerous neuroglia in the CNS
maintain blood brain barrier
create 3D framework
repair damaged tissue
microglia
Phagocytosis of cell debris and wastes
ependymal cells
Line ventricles and produces CSF
oligodendrocytes
- produces myelin/myelinates CNS axons
white matter vs gray matter
W: regions of CNS w/ many myelinated axons
G: regions of CNS that contains unmyelinated axons
microglia
smallest and least numerous neuroglia with many fine branched processes
- remove debris, wastes, and pathogens by phagocytosis?
satellite cells
surround neuron cell bodies in ganglia and regulate interstitial fluid
schwann cells
form myelin sheath or indented folds of plasma membrane
demyelination
progressive destruction of myelin sheaths in the CNS or PNS
diptheria
a bacterial disease that damages Schwann cells and destroys myelin sheaths in the PNS.
multiple sclerosis
autoimmune disease that destroys myelin in the CNS and leads to problems w/ speech etc
membrane threshold
the membrane potential value at which an action potential is triggered
Exocytosis and the release of acetylcholine into the synaptic cleft are triggered by
calcium ions flooding into the synaptic terminal
An excitatory postsynaptic potential (EPSP) is
a graded depolarization produced by the arrival of a neurotransmitter
An inhibitory postsynaptic potential (IPSP) is a
graded hyperpolarization of the postsynaptic membrane
the most excitatory neurotransmitter in the brain and functions in learning and memory?
glutamate
interneurons are responsible for
analysis of sensory inputs and coordination of motor outputs
Schwann cells are glial cells responsible for
producing a neurilemma around peripheral axons
what are 2 ways that a neuron will hyperpolarize?
- allow more potassium to leave the cell
- allow more chloride ions in
electrochemical gradient for potassium?
The chemical gradient moves potassium out of the cell, while the electrical gradient keeps potassium in the cell.
absolute refractory period
absolute: the period when the voltage-gated sodium channels are open and the membrane cannot respond to a new stimulus, even a strong one
relative refractory period
enough ions have redistributed across the membrane that a BIG stimulus will cause another action potential to be generated.
