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functions of nervous system
•Stabilizes intrinsic conditions
-O2 and CO2 content
-blood glucose levels
•Regulates behavioral patterns
-feeding, reproduction, defense, interaction with others
afferent and efferent?
afferent = periphery to CNS
efferent = CNS to periphery
what are the cells in the nervous system?
- glial cells
- vary in length
- numerous long processes
- receive stimuli and conduct electrical impulses
glial cells in CNS?
glial cells in PNS?
shwann cells or satellite cells
fxn of glial cells?
- severl types
- short processes
- non conducting cells
- support aand protect neurons
blood brain barrier
break neurons down functionally:
- sensory neurons: Somatic afferent - pain, temperature, touch, pressure, proprioperception
- Visceral afferent - pain and other sensations (mucous membranes, glands and blood vessels
: somatic efferent: voluntary impulses to skeletal muscles, visceral efferent: involuntary impulses to smooth muscle, cardiac conducting cells and glands
: network between sensory and motor neurons, greater than 99% of neurons, mammalian evolution
which part of neuron has clear cytoplasm
axon ( receives and transmits info)
what part receives stimuli?
what are dendrites covered in?
snypatic endings of other neurons
processes of glial cells
what is a nissl body?
- stack of rough ER in the cell body
what is ganglia?
collection of nerve cell bodies outside CNS
main types of neurons (structural)?
- bipolar - 1 axon, 1 dendrite (limited to certain neurons in eye and ear)
- multipolar - lots of dendrites and one axon (motor neurons)
- pseudounipolar- 2 axonal branches - one goes to the CNS and one extends to the PNS (sensory neurons!)
other name for cell body?
perikaryon - contains nucleus and organelles
what are the 2 types of synpases?
1) chemical - bind to receptors at postsynaptic cleft, so then ion channels open up, somtimes secondary messengers,
2) electrical - found in invertebrates, direct movement of ions from one to another
what is a bouton terminal?
a presynaptic knob - end
which molecules are involved in a synapse?
- synaptic vesicles
- v snare
- t snare
vesicle bound proteins
post synaptic membrane bound proteins
mechanism of how neurotransmitters fuse with membrane
presynaptic membrane depolarization - brief opening of Ca channels - exocytosis of synapic vesicles - release of neurotransmitter - neurotransmitter reacts with receptors - promotes postsynaptic depolarization - membrane retrieval by coated vesicles
binds calcium and helps membranes come together
what do v snare, t snare, and synaptotagmin do?
they act like a zipper zipping the two membranes together
explain how botox works
and what is the neurotoxin?
bochilism neurotoxin = bacterial protein causes paralysis and death
- there are 2 polypeptides:
- 1) binds to membrane protein of synapse of motor neurons (muslce) allowing protein 2 to get into the cell. 2 is a protease that chews up VSNARE (so neurotransmitters cant release) causing paralysis
what are the 3 ways that neurotransmitters are removed?
- enzymatic breakdown
what happens to sodium gated channels when neuron is stimulated?
na channels open up!! depolarization (gradient set up by the NAK ATPase pump
what are the voltages that occur?
normally it is at -65 mV but then sodium rushes into the cell all the way up to 30mv (action potential!) and then stops
how do you get back to -65?
voltage gated Na close and potassium channels open up (K moves OUT of the cell)
how do local anesthetics work?
hydrophobic molecules that bind to sodium channels, bind to open sodium channels (ones where neurons are firing)
it is reversible
what are some inhbitory neurotransmitters?
how do they work?
THEY OPEN ANION CHANNELS (make it negative) - they HYPERPOLARIZE the cell (make it go lower than -65 mV
increases effects of GABA, also may block sodium channels... how michael jackson died :( thrillller
How is myelin produced?
what is it and its function?
- produced by:
- - oligodendrocyes (CNS)
- - shwann cells (PNS)
myelin = 80% lipid, provides electrical insulation of neurons, makes impulse travel down axon quicker
how do shwann cells wrap around axon?
- modified plasma membrane of shwann cell winds and wraps around the neuron a bunch of times
- membrane has more lipids than normal
diff neurons have diff thicknesses
what is neuregulin?
growth factor secreted by axon that regulaes thickness of myelin sheath (on axolemma)
what is the name of the location with no myelin?
Node of Ranvier!! (where 2 shwann cells meet)
voltage reversal jumps from node to node
what is important at node of R's?
lots of K and Na channels so ACTION POTENTIALS OCCUR HERE!
otherwise myelin sheath would be covering it up
what about unmyelinated neurons?
nodes or R's?
shwan cell takes it and hugs it once, doesnt wrap around a ton
no nodes! na channels alll along the neuron
what are glia? and what are the 4 types that are in the CNS?
- oligodendrocytes: myelination in CNS
- astrocytes - morphologically heterogeneous, physical and metabolic support for neurons, most numerous!
- microglia- phagocytosis
- ependymal cells : line ventricles of brain and central canal in spinal cord
whats different about myelin sheaths in the CNS?
- unmyelinated - naked!!
- the ones that are: are wrapped around by oligodendrocytes (which can myelinate several axons)
- organization of myelin sheath is much more complicated
- larger nods of ranvier - more efficient saltatoy conduction
difference between oligodendrocytes and swhann cells?
swhann wrap around one axon, oligodendrocytes wrap around multiple axons
what are the proteins involved in myelin sheath? fxn?
Proteins= PO and MBP and PMP 22
hold membranes together
what is multiple sclerosis?
- demyelinating disease
- results in neuro defecits, loss of cutaneous sensation, lack of muscle coordination and movement, loss of bladder and bowel control
myelin sheath destroyed by an unknown mech
production of irregular multiple plaques
possibly an autoimmune disorder - increased antibodies against MBP (myelin basic protein)
what is shape of phagocytic cells?
- small elongated cells with short irregular processes
- involved in inflammation and repair in adult CNS
- act like immune system cell!
microglial cells and HIV?
- aids dementia complex is caused HIV infection of the CNS
- evidence indicates the microglia are infected by HIV
what are astrocytes?
2 classes? and how do the classes differ?
- largest, most numerous of neuroglial cells
- star shaped
- 2 types: similar in fx, diff shape
- 1) protoplasmic astrocytes
- - many short branched processes
- more prevalent in grey matter
- 2) fibrous astrocytes
- - few long straight skinny processes, white matter, GFAP more numerous, 80% of adult primary brain tumors are this
how is star shape maintained
- by IF protein (glial fibrillary acid protein)
- bundles of intermediate filaments
what are the function of astrocytes?
- support and bind neurons
- controls movements of molecules to and from neurons
- regulates (buffers) K+ concentrations in brain
- influence neuronal activity
- blood brain barrier
- forms a network
- they fully cover everything!!!
- control chemical environment (eat up old neurotransmitters)
- line the ventricles of brain and spinal cord
- it is an epithelial layer
- some can become secretory - choroid plexus - makes cerebral spinal fluid
look at figure in the book (slide 36) to see how it all fits together
peripheral nerves - where can cell bodies be found?
how many neurons and where does it go?
which kind of root?
which kind of axon?
cell bodies - in CNS or peripheral ganglia
1 neuron (pseudounipolar) connects receptor through a sensory ganglion to the spinal cord of brain (dorsal roots)
foudn in DRG (dorsal root ganglia), otuside each nerve root of spinal cord
how many neuron?
ventral or dorsal?
cell bodies in CNS, peripheral nerves travel to target skeletal muscle
- single neuron
- somatic efferetn
visceral efferent (autonomic) neurons?
how many neurons?
presynapic neuron (CNS to peripheral ganglia)
postsynaptic neuron (ganglia to target system (smooth muscle, cardiac muscle, and glands)
what are the 3 types of connective tissue that surround nerves?
- endoneurium - around nerve fibers (collagen is parallel to axon)
- perinurium - specialized CT, around each nerve fascile, active diffusino barrier has controlling transporters
- epinurium - dense irregular connective tissue, surrounds a nerve
structure of spinal cord
- grey matter on inside
- white matter on outside
- dura mater, arachnoid, pia mater
- dorsal root vs. ventral root
structure of brain?
what does grey matter on outside form?
- grey matter on outside, white in middle
- grey on outside forms CORTEX
diff between white matter and grey matter?
- white = myelinated axons (functionally related bundles of axons, not randomly distributed
- grey = cell bodies
whats the equivalent of ganglia (PNS) in the CNS?
functionally related clusters of cell bodies in CNS (diff from ganglia
what are meninges? function?
meninges = 3 membranes (connective tissue) surrounding brain and spinal cord
starting from outside:
- dura mater - tough mother, dense CT, continuous with perostium of skull!
- arachnoid - sheet like extensions, web like, in subarachnoid space is like an extra cushion - thespaces is cerebral fluid,
- pia mater - right on top o CNS (tender mother), continuous with perivascular sheath (blood vessels go down into brain and the pia mater lines those sheaths also) pia mater also lies on endfoot processes of astrocytes
explain blood brain barrier:
- Blood brain barrier = physical barrier between blood vessels
- and vast majority of CNS, stops many substances from crossing!
- Blocks all molecules except those can cross by lipid diffusion
- (O2 can cross, steroids can cross, alcohol, CO2, drugs, heavy metals
- All sorts of active transport proteins – everything that gets
- to neurons have to be transported (glucose! Amino acids, vitamins, and even)
- across endothelial cells, into astrocytes, then to neuron
what makes it tight?
Tight junction, really complex in epithelia of capillaries
- of basal lamina of endothelial cells with end foot processes
channel proteins for water, all alon blood brain barrier