nerves 2 Flashcards
neuron classification
-interneurons (association neurons)
interneurons
- located mostly within the CNS
- Interconnect among nerve cells
- function in processing
nerve cells (neurons)
electronically active cells that process and conduct information in the form of electrical cells
neuroglia (glial cells)
several kinds of support cells
PNS glial cells
satellite cells, schwann cells
CNS glial cells
oligodendrocytes, astrocytes,
Satellite cells in the PNS
surround neuron cell bodies within ganglia
Schwann cells in the PNS
- ensheath axons and dendrites in the PNS
- unmyelinated axons- Schwann cell ensheathe sections of many axons
- myelinated axon- Schwan cell ensheathe a section of a single axon
- Nodes of Ranvier-gaps between Schwann cells
oligodendrocytes
surround myelinated and unmyelinated CNS axons
Astrocytes
- largest and most numerous
- structural support; scar tissue formation
- regulate interstitial fluid components
- blood brain barrier
Blood brain barrier
-isolates neural tissue from general circulation
-restricts migration of cells and diffusion of molecules out of capillaries of brain
- -tight junctions between endothelial cells
-astrocytes cover capillary surfaces
-restricts diffusion of CSF out of ventricles
–tight junctions between ependymal cells
-incomplete barrier in areas
parts of the hypothalamus, pituitary gland, pineal gland
microglia
phagocytic cells- remove debris, pathogens, etc.
ependymal cells
- line chambers w/in CNS
- circulate CSF
- produce CSF in choroid plexus regions
Damage repair mechanisms of the CNS and PNS
- Damage to nerve cell soma -> neuron death
- few if any germinative cells in adult brain
- damage to nerve cell axon in CNS
- Oligodendrocytes reabsorb myelin
- astrocytes fill in area forming scar tissue
- growth inhibiting factors secreted by oligodendrocytes and astrocytes
- Damage to nerve cell axon in PNS
- Schwann cell myelin pathway can guide regenerating axons and sensory dendrites
electricity
flow of electrons
-force is an electrical gradient
bioelctricity
flow of ions
-force is chemical gradient and electrical gradient combined
active transport
maintain concentration gradients,
-sodiums ions out of cell and potassium ions into cell
gated ion channels
pathway for ion flow across the cell membrane
- chemically gated
- voltage gated
- mechanically gated
gated channels open in response to various signals (stimuli)
- ions flow across membrane by diffusion down their concentration gradient
- typically stay open only briefly
local current
- driving force is concentration gradient created by ions coming across membrane through open channels
- ions trave a short distance through cytoplasm or interstitial fluid
- happens anytime an ion channel is opened
local current and interstitial fluid
- cytoplasm and interstitial fluid have high resistance to ion flow
- depolarization or hyperpolarizaiton effect decreases with distance from open channel.
bioelectricity of local currents
- Local currents (graded potentials) transmit bioelectric signals over short distances
- Typical of dendrites & cell bodies in NS
bioelectricity of action potentials
Action potentials needed to transmit bioelectric signals over long distances
- Typical of axons
- Typical of long dendrites of unipolar and bipolar sensory neurons
- Unique to “excitable” cells
