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Afferent
(sensory) Carry impulses toward CNS
-
Efferent
carry impulses away from CNS
-
Somatic
to skeletal muscles - consciously controlled
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PNS consist of:
consists of the nerves and ganglia outside of the brain and spinal cord
-
Autonomic Nervous System:
to organs, smooth muscle, cardiac muscle, not consciously controlled.
-
ENS = _____
Digestive System
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Glial supporting cells:
____ brain cells.... occupy... ____
10% brain cells r neurons occupy 50% extns
-
List some glial cells
- Astrocytes
- Schwann cells
- Oligodendrocytes
- Microglia
- Ependymal cells
ASOME
-
ASTROCYTES (GLIAL CELL)
Forms blood brain barrier
Regulates extracellular fluid around neurons
-
Oligodendrocytes
Responsible for myelin formation in CNS.
-
Schwann Cells
Non-neural cell that forms myelin sheath in PNS.
-
Microglia
type of glial cell that acts as macrophage
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Ependymal cells
glial cell that lines internal cavities of the brain and produces cerebrospinal fluid
-
Type of neuroglia in CNS:
- Astrocytes
- Oligodendrocytes
- Ependymal Cells
- Microglia
-
Type of neurological in PNS:
Satellite cells & Schwann cells
1 axon may have as much as 500
-
Neural growth and regeneration steps:
- Precursor stem -->
- Differentiate ->become Neurons & Glial Cells
- Neurons Migrate ->
- Processes become dendrites & axon
- 50-70% Apoptosis
- Regeneration Occurs
-
Functional anatomy of neuron:
Dendrite
Axon (Nerve Fiber)
Axon Hillock
Collateral Axon
Node of Ranvier
Axon Terminal
BranchSchwann Cell
Oligodendrocyte
Neurilemma
Myelin Sheath
Soma
Terminal
End Knob
BulbTrigger Zone
- Dendrite
- Axon (Nerve Fiber)
- Axon Hillock
- Collateral Axon--Node of Ranvier--Axon Terminal Branch--Schwann Cell----Myelin Sheath--Soma--Terminal End Knob--Bulb--Trigger Zone
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Definition of Synapses
Chemical + Electrical
-
What is the synaptic cleft usually bridged by?
Neurotransmitters
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Functional Clasification of neurons (3)
sensory, motor, and interneurons
- sensory = afferent
- motor:
- interneurons:
-
What three broad classes of channels do the neural cell membrane contain?
- Ligand-gated channels
- Voltage-activated channels
- Leak Channels
-
Axoplasmic Flow
aka
Axonal Transport
The directed transport of organelles and molecules along nerve cell axons.
- can be from the cell body
- or
- towards the cell body
-
Grey Vs White Matter
- Grey Matter vs White Matter
- -Neural Cells *Axons connect 2 NeuralCells
- -Forms Cerebral Cortex *White kuz Myelin S.
- -Thalamus/Ganglia Also GM *Glia cells
- -Makes up Outer Surface * Inner Parts
-
-
Electrical potential is the difference.....
Measured in?
difference in charge and is measured in mV
-
The movement of electrical charge is called:
Hindrance of electrical charge movement is called:
-
Potential is the difference.......
Difference between two amount of charges influenced by # of charged particles and how close they are
-
Equilibrium potential for an ion is described by the
NERST EQUATION
E=RT/zF in Cout/Cin
-
Resting membrane potential
Uneven distribution of ions across the membrane caused by 3 things
-
What are some things that cannot pass out of the membrane?
- Negatively charged proteins
- Organic Phosphates
- Bicarbonates
- Glutamate
-
What is determined by permeability of the membrane?
- Electrical charge across membrane
- or
- Magnitude of resting membrane potential
-
What are the four channels in neurons we are most worried about in this class?
-
What is an action potential and what causes it?
A nerve impulse conducted on an excitable membrane, takes the movement of only a few ions to create large change in potential.
-
What causes an Action Potential?
- -Nerve impulse on excitable membrane
- -Stimulus that causes depolarization to threshold.
- -Takes generation potenrtial of ~15-30mV
- -~55-45mV, Stimulates opening NA+ gates
- (ions rush in aka influx)
- -Inside becomes positive so NA+ gates open
- (positive feedback loop)
- NA+ gates start closing(K/NA ATPase Pump)
- -K+ voltage gates open later
- (neg feedback loop)
- -Once threshold surpassed the AP full sized
- -Re polarization
- -K+ gates start closing
- -Hyperpolarization
- -Refactory Period
- -Resting Potential
-
Graded Potential are... that occur mostly in....
Characteristics include....
Depolarizations or Hyperpolarizations that occur in dendrites,
- Characteristics of graded potential
- -Exitatory or inhibatory
- Excitatory=neurotrans+mem.recep. stimulate opening of NA+ ligand-dependent channels causing local current flow.
- Current flow --> Trigger Zone
- Opens Na+ Voltage-dep gates if threshold
-
Absolute Refractory Period
vs
Relative Refractory Period
- Absolute Refactory period:
- is the interval during which a second action potential absolutely cannot be initiated, no matter how large a stimulus is applied.
- Relative Refactory Period:is the interval immediately following during which initiation of a second action potential is inhibited but not impossible.
-
Xyclocaine or novacaine prevent....
Prevent NA+ gates from openning!
-
Propagation or conductance of AP
- -Depolarization in one area stimulates depolarization in adjacent area.
- -Direction is away from the area of stimulus
- (One way due to ARP)
-
What does velocity depend on?
Where do AP occur?
- Fiber Diameter
- &
- Myelination:Unmylinated: Slower
- Mylinated: Faster
AP occurs only at the axon/nodes of ranvier
-
Diferences between
Graded Potential and Action Potential
- Graded.P Action .P
- -Amplitude varies w/size -All or None
- -Can b Summed -Cannot B Summed
- -No refactory period -Has Refactory Period
- -Dec w/dist -Constant value deploarization
- -Duration varies -Duration is constant
- w/initiating cond
- -Depolari/Hyperpolari -Depolarization only
- -Initiated by receptor, -Initiated by G.P
- neurotr(synapse), or spontaneously.
- Mechan. depends on -Depend Voltage-gated
- Ligand-gated chans
-
What is resting membrane potential usually at?
-70mV
-
When does Hyperpolarization occur?
- When below resting membrane potential.
- (below -70 ex: -80)
-
If threshold is higher than -70mV in AP does that mean the peak will be higher as well?
- No!
- Peek is usually at around +60 mV and thats when inactivation gates close, K+ voltage gates open, and depolarization occurs.
-
Can another action potential occur in the midst of one occuring?
- NO!
- Only during the Absolute Refactory Period few mili seconds.
This is due to Na+ Gates that are closed & inactivation gates are not yet reset.
Assures one way travel of AP by preventing backward conduction.
-
Define Synapses
WHat are the two kinds?
Specialized junctions between neurons where electrical activity of the presynaptic neuron influences postsynaptic neuron
- Two Kinds:
- Chemical - Most common type
- Electrical - Called electrotonic
-
Receptors have two parts:
- Binding component - Binds 2 neurotransmitter.
- Ionophore component - Is inside &opens chans
-
Anatomy of synapse
- Presynaptic neuron->
- Synaptic Cleft ->
- Postsynaptic Neuron ->
Presynaptic neuron releases neurotransmitters which diffuse across synaptic cleft and attach to specific receptors in the post-synaptic membrane.
-
Metabotropic Receptor
- Allow for fast or inhibatory transportation in nervous system.
- Can take neuron away from threshold (hyperpolorization)
- Or take post synaptic neuron towards towards threshold
- (Depolarization)
- Neurotransmitter binds to metabotropic
- results in release of G-protein from receptor
-
Ionotropic:
- Post synaptic receptor on phospho lipid bilaye
- Neurotransmitter binds to Ionotropic receptor causing an openning of ion channel
- CHanges shape and allows Sodium ions in.
quickly depolarizes or hyperpolarizes post synaptic neuron.
-
Types of terminal end knobs
- Discrete synapses: One area of contact
- Diffuse: Several areas of contact
-
Synapses can be:
- Excitatory: produce brief action potential to +
- or
- Inhibatory:produce brief action potential to -
-
Functional Aspect of synapses:
How signal is transmitted neuron to neuron in ACH synapse.
Depolarization in pre-synaptic neuron causes opening of voltage-sensitive Ca2+ channels.
- Ca diffuses into terminal end knob -> -Calmodulin Activated
- -Protein Kinase
- -phosphorylates synapsins or SNARE -proteins which stimulate vessicles to attach to attachment sites or docking proteins
- -release contents into cleft = Exocytosis
- -Neurotr. diffuse across cleft/bind to proteins in post synaptic density neuron.
- -Achesterase: enzyme that brks down ACH
- -receptors open receptor-operated chan to allow in Na+
-
Postsynaptic ACH receptors may be....
-
What are the five major groups neurotransmitters can be divided into?
- Low Molecular Weight Neurotransmitter
- Biogenic Amines or Momoamines
- Amino Acid Transmitters
- Neuropeptides (Large molecules)
- Nitric Oxide Neurotransmitters
-
Iontropic vs Metbroactive
-
Ionotropic receptors form an ion channel pore.
Metabotropic: G-Protein coupled receptor
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