Nervous Tissue and Physiology I: Lecture 18 Flashcards
human nervous system
physically connected network of cells, tissues, and organs that allow us to communicate with and react to the environment and perform life activities
brain nerve cells
100 billion by adulthood
speed of message transmission
180 mph
nervous system
controls perception and experience of world;
voluntary movement, consciousness, personality, learning, memory, homeostasis
CNS main components
brain- billions of neurons
spinal cord- millions of neurons; enables brain to communicate with body
PNS main components
all nerves outside protection of skull and vertebral column
nerves- bundled axons of neurons, blood, CT
cranial- 12 pairs
spinal- 31 pairs
ganglia- neuron cell bodies
primary functions of the nervous system
sensory input, integration, motor output
functional divisions of nervous system
sensory (afferent) -> somatic and visceral
motor (efferent) -> somatic and autonomic
autonomic -> sympathetic/parasympathetic
sensory/afferent division
touch, pain, pressure, vibration, temp, proprioception, chemical changes, stretch
motor/efferent division
motor innervation of muscles
nervous tissue makeup
80% cells- neurons and neuroglia
20% ECM- ground substance and glycoproteins
main functional regions of neurons
receptive- dendrites and cell body
conducting- axon
secretory- axon terminal
cell body
contains nucleus and maintains cytoplasm, mitochondria, organelles
nissal bodies
neuron specific; dark staining associations of ribosomes and rough ER
neurofibrils
intermediate filament cytoskeleton
dendrites
receptive region; short, highly branched processes
generate local potentials only (NOT action potentials)
axons
processes that can generate and conduct action potentials (conduct signals)
-AP turn into chemical signals
wrapped in myelin sheath
neuron function
generates and transmits nerve impulse along axolemma, initiated at trigger zone, conducted to terminals
anterograde transport
away from cell body
retrograde cell body
towards cell body
kinesin or dynein transport
transport that uses ATP-dependent motor proteins
myelin sheath
protein-lipid extension of glial plasma membrane
acts as insulation, increases transmission speed
Nodes of Ranvier
gaps in myelin sheath
white matter
myelinated cell bodies
gray matter
unmyelinated cell bodies
slow axonal transport
anterograde only
1-3 mm/day ‘stop and go’
cytoskeletal
fast axonal transport
anterograde and retrograde
200-400 mm/day
vesicles containing substances and membrane bound organelles
rabies
uses retrograde transport to infect the CNS
multipolar neurons
3+ processes (one axon, many dendrites)
most common
bipolar neurons
2 processes
rare- special sensory neuron
unipolar neurons
one process (T shaped)
receptive endings instead of dendrites
primarily found in ganglia of PNS
sensory neurons
transmit impulses from receptors to CNS; mostly unipolar
motor neurons
carry impulses away from CNS
cell bodies located in the CNS
interneurons
connect sensory and motor neurons
mostly confined to the CNS
primarily multipolar
neuroglia
hold neurons together; maintain extracellular fluid, assist neural function, repair damaged tissue
CNA neuroglia types
astrocytes
oligodendrocytes
microglial cells
ependymal
PNS neuroglia types
schwann cells
satellite cells
astrocytes
anchor neurons and blood vessels in place, maintain EC environment, assist in blood-brain barrier formation, repair damaged tissue
oligodendrocytes
flattened end processes form myelin sheaths around some CNS axons
microglia
act like macrophages in CNS tissue
ependymal cells
line brain ventricles, produce cerebrospinal fluid, circulates cerebrospinal fluid with cells
schwann cells
wrap around some PNS axons to form myelin sheath
satellite cells
surround and support cell bodies
myelin sheaths
electrical insulators (numerous phospholipid bilayers)
myelin sheaths in CNS
oligodendrocytes, no neurolemma, myelination begins after birth
myelin sheaths in PNS
schwann cells wrap around part of single axon, outer layer forms neurolemma, myelination begins in early fetal period
regeneration of nervous tissue
CNS: nearly non-existent
PNS: limited
-can regenerate only if cell body remains intact
