Download Nervous System PPT - Old Saybrook Public Schools

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Molecular mimicry wikipedia, lookup

Adoptive cell transfer wikipedia, lookup

Transcript
Neurons, Synapses and
Signaling
A peek inside the nervous system
Peripheral vs Central Nervous System
Neural Networks
Neurons
Nerve - bundle of axons
Supporting Cells
Glial Cells
Functions of
Supporting Cells
Schwann Cells - surround axons of PNS, form myelin sheaths
Oligodendrocytes - form myelin sheaths around axons in CNS, white matter of CNS
Microglia - phagocytose pathogens and cellular debris in CNS
Astrocytes - cover capillaries, create blood-brain barrier
Ependymal cells - epithelial lining of ventricles (brain cavities) and
central canal of the spinal cord
Neurons are excitable
neurons and muscle cells are excitable
transmit signals 20-100 meters/second
cell membrane generates impulses or action
potentials
Resting Potential
voltage - measures the electrical charge difference between 2 points
(potential energy), produce currents
ions carry electric current (Na+, K+, Ca2+, Cl-)
membrane potential - different ion concentrations across a membrane ->voltage
inactive neuron -60 to -70 mV
due to many negatively charged proteins the inside of the cell is more negatively
charged compared to the outside
maintained by K+ leak channels
+
+
Na -K Pump
(ATPase)
plasma membrane impermeable to ions
channels and ion transporters, glycoproteins, all animal cells
uses ATP to pump 3 Na+ outside and pumps 2 K+ inside against the
gradient
creates concentration gradients
generates resting potential
[Na+] higher outside the cell while [K+ ] is higher inside the cell
+
K Leak
Channels
always open, K+ diffuses out due to concentration gradient
leaves behind an overall negative charge
negative charges want to pull K+ back in
the tug-and-pull created is the resting potential
maintains the resting potential
Gated Channels
voltage-gated - open or close due to changes
in membrane potential
stretch-gated - open or closed to due to tension
applied to the cell membrane
ligand-gated - ligand binding sites, open and
closed based on the binding of the matching
ligand (neurotransmitter)
Action Potential
Brief, rapid changes in membrane potential
Originates in the axon hillock, after
-50mV or greater membrane potential
reached
Voltage gated Na+ channels open, depolarizing
the membrane
Na rushes into the axon, briefly creating a positive
charge within the axon, from -65mV to +40 mV
Each region stimulates the next region of the axon
K+ channels open restoring the membrane potential
Depolarization - charge on inside of membrane
becomes less negative relative to the outside
Hyperpolarization - charge on inside becomes
more negative
Positive feedback
Synapses
signal transmission via cell-to-cell contact
points
synaptic cleft is 20-30 nm (human hair 20,000 nm)
chemical synapse - neurotransmitters
electrical synapse - gap junctions that spread
the action potential
Chemical Synapse
Neuromuscular Junction
Neurotransmitters
Acetylcholine -muscle stimulation, memory, learning; nicotine binds to
receptor, sarin (nerve gas) blocks enzymatic breakdown of, botulinum
toxin inhibits release of
Glutamine - long term memory
GABA - amino acid in brain, inhibitory synapse; Valium reduces anxiety
by binding to a GABA receptor
Biogenic amines - dopamine, serotonin: LSD binds to receptors leads
to hallucinations; Parkinson’s due to lack of dopamine; Prozac inhibits
reuptake of serotonin
Neuropeptides - endorphins- relieve pain, produce euphoria; opiates
bind to same receptors
Multiple Sclerosis
Loss of myelin in the CNS - demyelinating
immune mediated response
damage to nerve fibers
most common autoimmune disorder
Lou Gehrig’s
Amyotrophic lateral sclerosis
5-10% inherited, autosomal dominant
Death of neurons that control voluntary
muscles
Neurotransmitter Glutamate may be involved
potentially many causes
Parkinson’s