CNS Pharmacology Dr. Pond Flashcards
(73 cards)
Where is the nucleus located?
Neuron cell
Cell body
What are the Processes (extensions) of a neural cell?
Dendrites: receive signals
Axon: send signals to other cells (communicate)
What is the part of the neuron where the action potential originates?
-sending signals through the axon starts with the action potential
-the action potential is elicited in the “Initial segment” or axon hillock
What are breaches of the axon called?
-Axon collateral
At which part of the neuron do chemicals get released to communicate with other neurons?
Axon terminals
Different forms of Neurons in reference to axon and dendrites?
-Multipolar: 3 or more processes coming off the cell bodies
-> Motor neuron (muscle), but many others
-Bipolar: 2 processes: 1 axon, 1 dendrites
-> retina, olfactory cortex
-Pseudounipolar: 1 process coming off the cell body, but it branches in two different directions: 1 axon, 1 dendrite
-> dorsal root ganglion, sensory (afferent) neurons (pain neurons)
What are the different Glia cells?
-Astrocytes: regulate neuronal microenvironment, since neurons are very excitable (through ions), the concentration of ions and chemicals must be regulated, part of the BBB
-Microglial cells: resident immune cells in the CNS, since the BBB exclude leucocytes, these cells act as immune cells in the brain
-Myelinating cells: Oligodendrocytes (myelinate axons in the CNS (brain and spinal cord) and Schwann cells (myelinate cells in the periphery)
What is the purpose of myelinating cells?
-lipid region that doesn’t conduct electrical signal
-the signal skips myelinated part -> fast conduction
Which cells form and circulate cerebrospinal fluid?
Ependymal cells
they have beads that circulate the fluid in the ventricular space
Function of the ATP pump
takes 3 Na(+) from inside to the extracellular space
-> thereby using ATP (hydrolyze to ADP)
takes potassium from outside to inside
inside: net negative
outside: net positive
-the pump is constitutive (always on) - creating a gradient: a lot Na outside and lots of potassium inside
-Primary active transporter
Which channels transport ions through facilitated diffusion?
Ion channels (ions can’t cross the membrane since the membrane is lipophilic and nonpolar)
-transport down the gradient
-no energy required
What are the different typed gated channels?
-mechanical
-chemical/ligand: opens when a ligand binds to the channel
-voltage-gated: net positive outside and net negative inside -> when the charge of the membrane changes -> opening of the gate
How do ion channels transport specific ions?
Because they are charge-specific (consisting of amino acids), depending on the charge they will transport specific chemicals
-either cation channel (+) or anion channel (-)
or size-specific:
-they may conduct sodium but not potassium
What does it mean when the membrane is polarized?
-net charge inside is more negative than outside
-Depolarization: movement of membrane potential back to 0
-Overshoot: membrane potential moves beyond 0 to the positive
-Repolarization: bringing the membrane potential back to resting (negative membrane potential = -70mV)
-Hyperpolarization: taking membrane potential more negative than resting -70 mV
Why do we see over-repolarization?
K channels are slow to close
Which ion channels cause depolarization?
Na (+) channels (Na moves inside)
also overshoot
Which channels cause Repolarization?
-Potassium channel (moves out)
-Chloride channel (moves in?)
Which channels are involved in the action potential?
-voltage-gated Na-channel
open - inactivate rapidly - shut closed
-voltage-gated K-channel
open - close slowly
What is the purpose of the deactivated state of the Na channel?
-as the membrane depolarizes the Na channel opens and the inside of the membrane becomes positive
-after inactivation, the Na channel stays shut for a while: to make sure the membrane potential stays positive and the action potential doesn’t spread but move from axon hillock to axon terminal in one direction;
-and to ensure the refractory period
What is the Equilibrium potential?
The potential that is desired by specific ions
E(Na): +72 mV - when Na channel open, it tries to get the membrane potential to +72 mV by Na moving in - during depolarization
E(K): -89.7 by K moving out - during repolarization
E(Cl-): -89.2 by Cl moving in - during repolarization
What is the absolute (ARP) and relative refraction period (RRP) phase?
absolute: no action potential can fire no matter how strong the stimulus is, bc there are no enough open Na channels
relative: some Na channels open again, it is still hard to elicit the action potential -> the action potential is weak
Which channels are located in the terminal axon?
high-treshhold Ca2+ channels (strong depolarization (+) needed)
How does signal transduction in the synapsis work?
action potential moves from axon hillok to axon terminal -> open Ca2+ channel -> Ca2+ binds to proteins on the vesicles that contains neurotransmitter
it facilitates the fusion of vesicles and the axon membrane -> release of NT at synaptic cleft
What are the receptors on the postsynaptic neuron that receive Neurotransmitter?
-ionotropic receptors (ligand-gating ion channels)
-> the Neurotransmitter is the ligand -> causes opening of the ion channel and ions to move through the channel
-Metabotropic receptors (G-protein-coupled)
NT binds -> alpha subunit of the G-protein (alpha, beta, gamma) cleaves and binds to:
effector protein -> opening/close ion channel
OR
ion channels for -> opening/close ion channel
