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What is the charge inside of the neuron compared to the outside and what is this state called ?
Resting Membrane Potential: Inside the neuron is NEGATIVE (-70mV)
What are the four ions that contribute to the neuron and where are they placed ?
- Sodium (Na+) Outside
- Chloride (Cl-) Outside
- Potassium (K+) Inside
- Negative Proteins Inside (these are always stuck within the neuron)
What factors contribute to EVEN distribution wihtin the ionic basis of the resting potential ?
- Random Motion: particles that are in areas of high concentration want to move to areas with low concentration
- Electrostatic Pressure: like forces repel, opposites attract
What factors contribute to UNEVEN distribution within the ionic basis of the resting potential ?
- Selective Permeability: Membrane allows selective ions in
- Sodium-Potassium Pumps: Constantly working (3 NA+ out / 2 K+ in)
The Sodium-Potassium Pumps are a what process ?
Where does the Postsynaptic Potentials (PSP) occur ?
- Integrated near the Axon Hillox
- Summation occurs over time and space (adding or combining a number of individual signals into one overall signal)
The Postsynaptic Potentials (PSPs) cause ?
- Depolarization: making the membrane potential LESS negative (-70 to -67 mV). This is EXCITATORY (more likely a neuron will fire) (EPSP)
- Hyperpolarization: making the membrane potential MORE negative (-70 to -73 mV). This is INHIBITORY (less likely a neuron will fire) (IPSP)
EPSP and IPSP are ? (Like a rock thrown in the pond with ripples, need more then one small pebble)
- Graded: the greater the stimulus, the greater the response
- Decremental: they get smaller as they travel
To fire an Action Potential there needs to be a reach of ?
- Threshold of Activation (-65 mV)
- More than one EPSP
The Action Potential is a what name ?
- All-or-None: when threshold is reached the neuron 'fires' and the Action Potential either occurs or does not
- When threshold is reached, voltage-activated ion channels are opened (-70 to +50 mV)
What are the two aspects of the Refractory Periods (x1000/sec) ?
- Absolute: IMPOSSIBLE to initiate another action potential
- Relative: HARDER to initiate another action potential (High/Supra can cause action potential)
What is the faster conduction than in unmyelinated axons ?
- Saltatory Conduction: Passive conduction along each myelin segment to next node of Ranvier
- New action potential generated at each node
What does the Nurotransmitters release when Calcium comes into the cell and the NTs are dumped ?
What are the two classes of Receptors for a given NT ?
- Ionotropic Receptors: open and close ion channels
- Metabotropic Receptors: effect function of neuron & open and close channels
What happens within the Ionotrpoic Receptor ?
- NT binds->associated ion channel opens or closes->PSP
- NA+ channels open->NA+in->EPSP
- K+ channels opened->K+ out->IPSP
What happens within the Metabotropic Receptors ?
NT binds->G protein breaks away->Ion channel opened/closed & 2nd messenger synthesized
What are two ways that the activity in the synaptic cleft is turned off ?
- Reuptake: scoop up and recycle NT
- Enzymatic Degradation: NT broken down by enzymes
What are the seven NT and what are their functions ?
- Serotonin: Mood, temperature regulation
- Dopamine: Pleasure, reward, motor movement
- Acetylcholine: Memory, muscle contraction
- Anandamido: Pain reduction, increase appetite
- Norepinephrin: Stress hormone, mood, sleep, brain arousal
- GABA: Main inhibitory NT
- Glutamate: Main excitory NT, sensory neuron
What are the two classes of NT molecules ?
- Small: Synthesized in the terminal button and packaged in synaptic vesicles
- Large: Assembled in the cell body, packaged in vesicles, and then transported to the axon terminal
What are considered the Small-Molecule NT ?
- Amino Acids
- Monoamines:DA, NE, EPI, Seretonin
- Acetylcholine (Ach)
- Unconventional NT (soluble gases, endocannabinoids)
What Amino Acid NT are Excitatroy and Inhibitory ?
- Glutamate: Excitatory in CNS
- GABA: Inhibitory in CNS
What is the Monoamines ?
- Synthesized from a single amino acid (Tyrosine OR tryptophan)
- Effects tend to be diffuse
What are the two procedures of Monoamines ?
- Catecholamines: synthesized from tyrosine (Tyrosine->Dopamine->Norepinephrine->Epinephrine)
- Indolamines: synthesized from tryptophan (milk, turkey) creates serotonin
Where is Dophamin located and what does it involve ?
- Basal Ganglia: involved in motor movement
- Limbic System: involved in reward & pleasure
- Frontal Lobe: involved in STM & planning
What is the impact of Acetylcholine ?
- Only NT released at neuromuscular junction (NMJ)
- Can help with learning and memory
- In Alzheimer's can be used during low stages to help
What are the different effects on Synaptic Transmission ?
- Agonists: Increase OR facilitate NT activity
- Antagonists: Decrease OR inhibit NT activity
- Drugs may alter NT activity at any point in its 'life cycle'
What are some examples of Agonists drugs ?
- Cocaine - Dopamine: Blocks reuptake- preventing the activity of the NT from being turned off
- Benzodiazepines - GABA: binds to the GABA molecule and increases the binding of GABA (glue)
What are some examples of Antagonist drugs ?
- Atropine - ACH: Binds and blocks muscarinic receptors in CNS (metabotropic)
- Botox - ACH: Blocks releach of Ach at nicotinic receptors at NMJ (ionotropic)