Chapter 12 - Neuron & Glia Flashcards
Excitibality
- Neurons & Muscle cells are excitable
- Ions move and changes in membrane potential conduct
Central Nervous System
Brain and Spinal Cord
Peripheral Nervous System
Nerves and Ganglia
Efference
Motor
Afference
Sensory
Tract
Bundle of axons
(CNS)
nucleus
group of cell bodies
(CNS)
nerve
bundle of axons (PNS)
ganglion
group of cell bodes (PNS)
Which glial cell type does the most different kinds of activities to support neurons?
Astrocytes
Schwann cells
wrap unmyelinated axons, but not multiple spiral wraps.
Ependymal cell
- Produce CSF
- Line the ventricles of the brain and central canal of the spinal cord and
- Tufts of ependymal cell tissue = choroid plexus.
- Creates barrier between these CSF filled spaces and the neural tissue.
- Source of neural stem cells
Choroid plexus
transport ions and nutrients from the blood into the cerebrospinal fluid.
Astrocyte
Regulate the ECF of neurons in the CNS:
Take up excess K+ to help neurons maintain their resting potential, “K+ sponges”
Take up excess neurotransmitter, prevent excess synaptic signalling, “NT sponges”.
Produce growth factors for neurons “nourish” and provide nutrition (fuel to make ATP).
Structural support:
Spatial support, “hold neurons in place” so they can maintain synapses
Guide migrating neurons during devel of brain
Cover brain surface
Cover nonsynaptic regions of neurons
Induce blood-brain-barrier to form.
Communicate electrically with neurons/influence synapses.
Form scar tissue after damage to the CNS.
Source of neural stem cells.
Microglia
Phagocytes
Scavengers of dead tissue (after injury to CNS)
Immune function against pathogens
Derived from Monocyte (white blood cell made in bone marrow)
oligodendrocytes
Myelinating cells of the CNS.
Resting Membrane potential
At Rest (unstimulated),A Neuron has a voltage
Initial Stimulation
the act of disturbing a neuron that was at rest
- Can be accomplished 3 ways: electrically, chemically or physically
Chemical Stimulation
Chemical (neurotransmitter, NT) binds to a receptor (ligand-gated channel shown) which allows for opening of an ion gate
and that changes the voltage
Resting membrane potential
-70, potassium would need to leave the cell and take its positive charge outside the cell so it becomes more negative.
threshold
-55, mV value at which the voltage gates will open
+35
peak of action potential
+62, ENa+
equilibrium potential for sodium
- sodium wants to bring as much positive charge as possible
- Sodium would want to bring in as many sodium ions as possible, to get the -70 mV all the way up to +62 mV
-90, Ek+
- Potassium balance is at -90
Depolarization
- brings cell closer to threshold later, EPSP
- Moving in the positive direction of our resting potential
- When sodium channels open
Hyperpolarization
- Brings cell away, more negative
- this is inhibitory, brings cell away from threshold later, IPSP
- When potassium channels open
At threshold
Voltage gated channels open
Repolarization
going back to its resting membrance potential
Absolute refactory period
wouldn’t get another action potential at all
Relative action potential
if we have a big enough stimulus we can stimulate another action potential with that voltage gated sodium channel
what is undirectional conducation
one way, can’t back up
Why does conduction occur
because of the refactory period
Saltatory conduction
jumps
Electrical synapses
rare in CNS but common in muscle. They make use ofGap Junction Proteins
Chemical Synapses
MUCH more prevalent – Adjustable!
When Action Potential reaches Axon Terminal it stimulates Voltage-gated Ca++ channels
The influx of Ca++ causes exocytosis of vesicles that contain Neurotransmitter (NT)
Transmitter binds to a receptor on the mb of the next neuron (or muscle cell, etc.)
There are 2 Different types of Receptors: Receptors associated w/ Ion Channels vs Receptors associated w/ 2nd Messenger Systems
There are over 100 different types of transmitters. The text gives three examples: Acetylcholine, GABA, & Norepinephrine
Acetylcholine
will bind to a receptor that is connected to a Na+ channel.
It lets Na+ enter to stimulate
the postsynaptic neuron… an
Excitatory Postsynaptic Potential (EPSP) which is a form of initial stimulation.
Neuromodulators
peptides released like small simple amino acid derived neurotransmitters, but they alter synapses.
Memory
due to “strengthened” synapses, when you form memorys its due to new synaptic connections
Temporal summation
Done in a timing kind of manner
Spatial summation
over space and area we’re looking at we see three separate inputs to one post - synaptic neuron.
anasthesia
makes it impossible for pain stimulus to transmit afferently, don’t sense pain because voltage gate channels are inhibited
