Nervous system

•Stabilizes intrinsic conditions

-blood pressure

-O2 and CO2 content

-pH

-blood glucose levels

-hormone levels


•Regulates behavioral patterns

-feeding, reproduction, defense, interaction with others

afferent = periphery to CNS

efferent = CNS to periphery

• neurons
• glial cells
• vasculature

• vary in length
• numerous long processes
• receive stimuli and conduct electrical impulses

neuroglia

shwann cells or satellite cells

• severl types
• short processes
• non conducting cells
• support aand protect neurons

blood brain barrier

• sensory neurons: Somatic afferent - pain, temperature, touch, pressure, proprioperception
• Visceral afferent - pain and other sensations (mucous membranes, glands and blood vessels

motor neurons: somatic efferent: voluntary impulses to skeletal muscles, visceral efferent: involuntary impulses to smooth muscle, cardiac conducting cells and glands

internuerons: network between sensory and motor neurons, greater than 99% of neurons, mammalian evolution

axon ( receives and transmits info)

dendrites

snypatic endings of other neurons

processes of glial cells

- stack of rough ER in the cell body

collection of nerve cell bodies outside CNS

• 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!)

perikaryon - contains nucleus and organelles

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

a presynaptic knob - end

• synaptic vesicles
• v snare
• t snare
• synaptotagmin

vesicle bound proteins

post synaptic membrane bound proteins

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

they act like a zipper zipping the two membranes together

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

• enzymatic breakdown
• diffusion
• endocytosis

na channels open up!! depolarization (gradient set up by the NAK ATPase pump

normally it is at -65 mV but then sodium rushes into the cell all the way up to 30mv (action potential!) and then stops

voltage gated Na close and potassium channels open up (K moves OUT of the cell)

hydrophobic molecules that bind to sodium channels, bind to open sodium channels (ones where neurons are firing)

it is reversible

• GABA
• glycine

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

• produced by:
• - oligodendrocyes (CNS)
• - shwann cells (PNS)

myelin = 80% lipid, provides electrical insulation of neurons, makes impulse travel down axon quicker

• 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

growth factor secreted by axon that regulaes thickness of myelin sheath (on axolemma)

Node of Ranvier!! (where 2 shwann cells meet)

voltage reversal jumps from node to node

lots of K and Na channels so ACTION POTENTIALS OCCUR HERE!

otherwise myelin sheath would be covering it up

shwan cell takes it and hugs it once, doesnt wrap around a ton

no nodes! na channels alll along the neuron

• 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

- 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

swhann wrap around one axon, oligodendrocytes wrap around multiple axons

Proteins= PO and MBP and PMP 22

hold membranes together

• 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)

• small elongated cells with short irregular processes
• involved in inflammation and repair in adult CNS
• act like immune system cell!

• aids dementia complex is caused HIV infection of the CNS
• evidence indicates the microglia are infected by HIV

• 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

• by IF protein (glial fibrillary acid protein)
• bundles of intermediate filaments

• 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

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

cell bodies in CNS, peripheral nerves travel to target skeletal muscle

• single neuron
• somatic efferetn
• ventral!

presynapic neuron (CNS to peripheral ganglia)

postsynaptic neuron (ganglia to target system (smooth muscle, cardiac muscle, and glands)

• 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

• grey matter on inside
• white matter on outside
• dura mater, arachnoid, pia mater
• dorsal root vs. ventral root

• grey matter on outside, white in middle
• grey on outside forms CORTEX

• white = myelinated axons (functionally related bundles of axons, not randomly distributed
• grey = cell bodies

nuclei!!

functionally related clusters of cell bodies in CNS (diff from ganglia

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

• 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

Tight junction, really complex in epithelia of capillaries

• Association
• of basal lamina of endothelial cells with end foot processes

channel proteins for water, all alon blood brain barrier