Neuron And Action Potential Flashcards
What are the two parts of the Nervous system and their functions?
Central Nervous System:
- Integrates signals
- Sends signals to PNS
Peripheral Nervous system:
- Senses input
- Relays input to muscles
What are the two types of synapses in neurons?
- Electrical synapse/Gap junction
2. Chemical synapse
What is syncytium?
When an AP is elicited anywhere within a muscle mass, it generally travels in all directions in the muscle
Aka all cell act in synch
Which the cells are responsible for creating the myelin sheath?
CNS: Oligodenrocytes
PNS: Shwann cells
What are the roles of supporting cells of the CNS?
Ependymal cells: assist in producing and circulating CSF
Astrocytes: Maintain BBB
Oligodendrocytes: Increase conduction via myelin sheath
Microglia: Remveal of debris and waste via phagocytosis
Describe graded potential vs action potential.
In Graded Potential, there are a variable amounts of changes in charge; Cell body,dendrite
In action potential, Changes in charge are always identical; Axons
What is the resting potential of most neurons?
-80 to -60 mV
Differentiate Absolute Refractory period vs Relative Refractory period.
ARP: AP cannot be generated regardless of stimulus intensity. Due to closure of Na+ channel inactivation gate
RRP: Due to inactivated conformation of the voltage gated Na channels; Conductance of K+ is higher than the resting potential, so the membrane potential becomes more negative
Describe the pathology and symptoms of Multiple Sclerosis.
- Autoimmune disorder where immune cells attack myelin sheath
- Reduced conductance of neurons
- Loss of sheath leads to leakage of K+
- Partial loss of vision and problems with speech, balance,m and motor coordination
What are the types of propagation and where are they located?
Continuous -> Unmyelinated
Saltatory -> Myelinated
How are NTs transported down the axon?
In vesicles don microtubules via dynein and kinesin
What are the 3 types of ion channels on neurons?
- Stretch-gated
- Ligand gated
- Voltage gated
What determines Nt release?
- INC calcium into the presynaptic axon causes exocytosis of vesicle contents into synapse
- Concentration of Ca++ determines concentration of NT released
Describe Lambert-Eaton syndrome.
- Autoimmune
- Antibodies attack voltage-gated calcium channels on presynaptic axon terminal
- Impairs NT release
- Characterized by general muscle weakness
Describe Gillian-Barre Syndrome.
- Severe autoimmune disorder
- Immunologic destruction of Schwann cells, nerve roots, and ganglia
- Manifests as ascending weakness/paralysis
- Rapidly travels upward, and result in fatal respiratory paralysis
- prompt care to decrease inflammation can help recover normal function and demyelination of nerves
How does lidocaine work?
- Inhibits local Voltage-gated Na+ channels
What type of nerve fiber is the Dorsal root ganglia? What type of information do they send? Diameter?
Type C Fibers: Pain, Temperature; 0.4 - 1.2 micrometers
Which type of receptors are most sensitive to local anesthetic?
Unlyelinated Type C Fibres (Nociceptive)
How are ions distributed in terms of number between inside and outside of membrane At resting potential?
Total number of charged molecules and ions are distributed evenly
What would be the result of an inhibited Na/K ATPase?
Inhibition of NA/K ATPase —> INC Na+ —> DEC Na+ Gradient —> Inhibiting Na/Ca exchanger —> INC Intracellular Ca
INC Intracellular —> Inhibits SGLUT
What is the resting potential of a cardiac myocyte?
- 90 mV
What channels have the most significant impact on resting membrane potential?
Potassium and Chloride leak channels
What are the four gated ion channels?
- Voltage-gated
- Ligand-gated
- Messenger-activated
- Stretch-activated channels
How do Na voltage gated channels and K++ Chanel’s differ? (Besides ion duh)
1) The Na+ voltage-gated channels have two gates: an activation gate and a
deactivation gate.
2) The K+ channels only have one gate.
