Neurophys Flashcards
Is endocrine fast or slow control?
slow control
Is the nervous system fast or slow control?
fast control
2 major divisions f the nervous system?
Central and peripheral
Central nervous system
brain and spinal cord
Peripheral nervous system
nerves that connect the brain or spinal cord with the body’s muscles, glands, and sense organs.
Basic cell type of the nervous system
neuron
neurons are amitotic meaning…
they do not divide
Neurons have a very high what?
metabolic rate. they need a lot of glucose and have a lot of mitochondria
most numerous cells in the CNS
Glial (non-neuronal support)
Astrocytes
SOO diverse! Work in healing; regulate ion concentrations, synapse formations and more; Create a supportive framework for neurons.
Oligodendrocytes
form and maintain myelin in the CNS.
Microglia
CNS macrophages. Important immune system workers of the CNS.
Ependymal Cells
Create CSF in the CNS.
Schwann Cells
Create myelin in the PNS.
Afferent neurons
move from the muscle to the CNS
-affected by a stimulus
see slide 13
Efferent neurons
move from the CNS to the muscle
-cause an effect
see slide 13
Interneurons
- Lie entirely within the CNS
- account for > 99 percent of all neurons
If axons are severed, they can repair themselves and restore significant function only if….
the damage occurs outside the CNS and does not affect the neurons cells body
why is peripheral nerve injury healing so slow?
axon regrowth proceeds at a rate of only 1 mm per day
what happens to the axon segment that is separated from injury?
the cell body degenerates. The part of the axon still attached to the cell body then develops a new growth cone, which grows out toward the effector organ. Sometimes function is restored.
apoptosis=
cell death
what you need to know about generation and conduction of a nerve impulse:
- Resting Membrane Potential, generated by Active Transport
- Voltage Gated Na+ and K+ Channels
- Depolarization, repolarization, hyperpolarization
- Graded Potential
- Threshold Potential
- ALL-OR-NONE FIRING
- Action Potential
- Unidirectional signal conduction
- Delayed opening of K+ channels relative to Na+ channels
The resting membrane potential
difference in charge
- more positive outside
- more negative inside
what is the sodium potassium pump reliant on
ATP function
Depolarization
the potential moving from RMP to less negative values.
Repolarization
is the potential moving back to the RMP.
Hyperpolarization
the potential moving away from the RMP in a more negative direction.
Graded potentials
- little changes in membrane potential that are confined to a relatively small region of the plasma membrane.
- By definition, they can be of various sizes, but don’t reach threshold potential by themselves.
Two types of graded potentials
EPSP’s (excitatory)
IPSP’s (inhibitory)
7 steps of the nerve firing
1.RMP
2.threshold reached.
3.Na+ channels open in response to the depolarization beside them.
4.Na+ channels are inactivated while the slower K+ channels open to repolarize the cell.
Since the sodium channels are inactive, the signal can’t go backward here.
5.K+ channels cause enough + ions to leave the cell’s interior that the membrane repolarizes, and in fact…
6.Hyperpolarizes the cell, making it even harder for a signal to transmit backward.
7.K+ channels finally close and Na+ channels are reactivated, but by this time the signal is long gone.
action potential inhibition
Lidocaine, Procaine, Marcaine– block voltage-gated Na+ channels.
Absolute refractory period
another action potential cannot be sent at this time (step 5 of nerve firing)
relative refractory period
another can be sent only if it is big enough to overcome this hyperpolarization PLUS the normal amount of depolarization (step 6 of nerve firing)
what is Myelin?
an insulator that makes it more difficult for charge to flow between intracellular and extracellular fluid compartments.
-adds speed, reduces metabolic cost, and saves room in the nervous system because the axons can be thinner
What are the node of Ranvier?
Action potentials occur only there
-where the myelin coating is interrupted and the concentration of voltage-gated Na+ channels is high.
how do synapses pass information?
chemically or electronically
-they use neurotransmitters
are synapses inhibitory or excitatory?
inhibitory or excitatory depending on the signal/ neurotransmitter being transmitted
When the synapses signal is Electrical
Pre- and post-synaptic cells are connected by gap junctions
When the synapses signal is Chemical
- Pre-synaptic neurons release neurotransmitter from their axon terminals
- Neurotransmitter binds to receptors on post-synaptic neurons
neurotransmitter is released via what?
exocytosis
autoreceptors are
a built-in brake for the system
To terminate the signal in a chemical synapse, the neurotransmitter must be removed. This is accomplished by:
- Diffusion of the transmitter from the cleft
- Degradation of the transmitter by enzymes
- Reuptake into the pre-synaptic cells for reuse
- Removal of the receptors in the post-synaptic cell’s membrane.
ACETYLCHOLINE (Ach):
- This one is made by attaching acetyl CoA to choline.
- It’s ALWAYS the first signaler on efferent pathways to the peripheral nervous system.
- After being sent into the synapse, it gets broken back into AcCoA and Choline by acetylcholinesterase (AChE). The pieces then get recycled.
CATECHOLAMINES:
Dopamine, Epinephrine, Norepinephrine
(DA, Epi, NE):
- Made from the amino acid tyrosine
- NE and Epi are important in the Sympathetic Nervous System (more on that later)
- Once released into the synapse, they’re either taken back up into the pre-synaptic neuron or destroyed by monoamine oxidase (MAO).
Serotonin
a complicated one!
- Made from an essential amino acid, Tryptophan.
- Works slower than some neurotransmitters– more of a “modulator” than a true transmitter.
- Almost always there’s another transmitter being released along with it.
- It’s excitatory in muscle pathways, inhibitory in sensory pathways.