Most wide-spread excitatory transmitter in the CNS
- Funciotn on the motor end plate, neuromuscular synapse, and also a major NT in the CNS. In motoneurons between the pre- and post-synaptic
- Found in NT, CV system, also in CNSWhen released at heart, increase heart rate and force of contraction, costrict blood vessels
Neurotransmitter: alpha-aminobutyric acid(GABA)
- Widespread inhibitory transmitter in CNS
Why do stroke patients become rigid?
- Damage to the inhibitory neurons so activity goes upNormally, there is a balance/SUM between inhibitory and excitatory
- Repetitive firing of a single presynaptic cell.
- Summing the effect on AP
- Typical way to allow pre-synapse to affect the post-synaptic membrane
- Concentration of NT goes up
- AP goes down multiple pre-synptic neurons so the 2 AP will have affect on the post-synsptic membrane.
- Added in space
- Response is greater than either AP alone
- Result--post-synaptic membrane can depolarize
- TIMING important: need to be added in space. If one arrives earlier than will not depolarize enough to reach threshold
- Where the fast soidium channels are locatedGet end plate potentials to summate to get propagation of AP to peripheral.
- Even if membrane is partially depolarizes, if on post-synaptic membrane and not the initial segment, does NOT matter.
- NEED THE FAST SODIUM CHANNELS
How does Cl- inhibit without being hyperpolarized?
- Tranference Equation
- Excitationn when Cl- channels are open.
- now if activation of inhibitory synapses causes a large number of Cl- channels to open, so that TCl- =
- Calculate new membrane potential that must consider
- all ions.
- opening of the Na+ and K+ channels will not cause as much depolarization, as shown by the transference equation:
- Now have to split the transferences to 0.25 because all transferences must equal 1
- Em = TK+ EK+ + TNa+ENa+ + TCl- ECl-
= (0.25)(-90 mV) +(0.25)(60 mV) + (0.5)(-85 mV) = -50 mV