Nervous System
What are the three stages of information processing?
sensory input, integration, motor input
What is hyperpolarization?
an increase in the magnitude of the membrane potential
What is resting potential?
the membrane potential of a neuron that is not sending any signals
What are the five major classes of neurotransmitters?
acetylcholine, biogenic amines, amino acids, neuropeptides, gasses
What is an electrical synapse?
where an electrical current flows from one neuron to another
What is the difference between the central nervous system and the peripheral nervous system?
CNS - is where integration takes place, is made up of the brain and spinal cord
PNS - brings info to the CNS, brings out commands from the CNS, is made up of all the parts that are not the brain and spinal cord
Why are action potentials considered all-or-none responses?
action potentials either happen or they don't: there are no big or small APs regardless of the strength of the stimulus
How is equilibrium potential calculated?
Nernst equation: 62mV (log ([ion outside] / [ion inside]))
How does GABA act as a neurotransmitter? Give an example.
GABA (an inhibitory amino acid) increases the permeability of a neuron to Cl- ions
Ex: Valium binds to GABA receptors to reduce the effectiveness of GABA, which also reduces anxiety
What is the difference between EPSPs and IPSPs?
EPSPs are depolarizations that make the membrane less negative as they bring the membrane potential toward threshold by opening channels for Na+ and K+ diffusion
IPSPs are hyperpolarizations that make the membrane more negative as they bring the membrane potential away from threshold by increasing the permeability to K+ moving out or Cl- moving in
What happens when you hear a scary sound?
1. sound is detected by your sensors and then signals are sent along sensory neurons that are part of the PNS
2. those signals reach the CNS and that info is integrated
3. signals are sent along motor neurons that are part of the PNS until they reach effectors (ex: signal reaches muscles so that you can run away)
What are the steps of generating an action potential?
1. Resting - gated K+ and Na+ channels are closed
2. Depolarization - stimulus opens some Na+ channels, which depolarizes the membrane, so that threshold is reached and an action potential is triggered
3. Rising Phase - Na+ enters the membrane, making it more positive
4. Falling Phase - most Na+ channels become inactive as K+ channels open, making the inside more negative
5. Undershoot - K+ channels close and Na+ channels become unblocked (still closed), so membrane returns to its resting state
Why is the inside of a neuron negative and the outside of a neuron positive?
Na+/K+ pumps maintain a high concentration of K+ inside the neuron and a high concentration of Na+ outside the neuron
When a neuron is resting, it has lots of open K+ channels and few open Na+ channels
K+ diffuses out of the cell as anions (Cl-) are trapped inside the neuron, which contributes to the negative charge inside the neuron
How are dopamine and serotonin involved in medical conditions?
dopamine: people with Parkinson’s disease experience a lack of dopamine in the brain
serotonin: Prozac helps people with depression because it inhibits the reuptake of serotonin so that serotonin can have an effect for longer in the brain
What are the steps of a signal crossing a chemical synapse?
1. the presynaptic neuron makes the neurotransmitter and packages it in vesicles (in synaptic terminal)
2. when an action potential arrives, the PreN lets in calcium (helps vesicles bind to cell membrane) and the neurotransmitter is released
3. neurotransmitter diffuses across the synaptic cleft to the postsynaptic cell.
4. neurotransmitter binds to ligand-gated ion channels on the postsynaptic membrane