electrical signaling by neurons part 2

what can affect the velocity of an action potential

- diameter: a larger axons means increased velocity] - insulation: myelinated axons conduct faster action potentials

what 2 potential changes could occur in the postsynaptic membrane after a synapse?

1. depolarizing potential change- excitatory postsynaptic potential 2. hyper polarizing potential change- inhibiting post synaptic potential

how can a NT action potential be terminated?

1. diffuse away in synaptic cleft 2. reabsorbed by presynaptic ending or glial cells 3. degraded by enzymes in the synaptic cleft

summarize steps of action potential

1. neuron membrane rests at -65 mV 2. neuron receives an excitatory input and membrane depolarizes slightly. change in voltage causes voltage-gated Na+ ion channels to open and let Na+ into the membrane, more positive cells come into cell, therefore... 3. threshold level (-55mV) is met where enough depolarization has occurred to allow a mass opening of Na+ channels into the membrane, more Na+ comes in 4. Na+ channels are open and sodium continues to descend into membrane (rising phase) 5. peak occurs at around +35mV. sodium channels close and K+ channels open. 6. K+ begins to fall out of membrane, membrane is becoming more negative, or repolarized. 7. lots of K+ leaving means that membrane potential dips below -65mV, but it will recover through sodium potassium pump

steps of synaptic transmission

1. neurotransmitters are packaged in vesicles at presynaptic element 2. action potential depolarizes presynaptic nerve terminal 3. voltage gated calcium channels open and calcium enters 4. vesicles bind to active zones on the membrane 5. NTs are released into synaptic cleft, called exocytosis 6. NTs bind to ion channels in post synaptic membrane; ligand-gated ion channels open or close (called post synaptic potential)

what happens in an inhibitory postsynaptic potential

NT binds to ion channels ion channels open, either anions flood into membrane or cations flood out membrane is hyper polarized, becomes more negative IPSP inhibits action potential from occurring in post synaptic cell

serotonin

NT involving mood and pain perception

dopamine

NT that affects cognition, motor movement, and behavior pleasure and reward NT

what happens in an excitatory postsynaptic potential

NTs bind to ion channels on postsynaptic membrane ion channels open, allowing many positive ions into the membrane membrane is depolarized (less negative)

saltatory conduction

Rapid transmission of a nerve impulse along an axon, resulting from the action potential jumping from one node of Ranvier to another, skipping the myelin-sheathed regions of membrane.

NT implication for cocaine and amphetamine use

affects norepinephrine and dopamine signaling by blocking reuptake and increasing their release into synapse

panic disorder

an anxiety disorder that consists of sudden, overwhelming attacks of terror associated with higher levels of norepinephrine

Parkinson's disease

associated with lower levels of dopamine, treated with L-dopa, synthetic drug that metabolizes into dopamine

myasthenia gravis

autoimmune disease where body produces antibodies that bind with nicotinic cholinergic receptors in motor end plates, preventing acetylcholine from binding to necessary ion channels severe muscle weakness

botulinum toxin (Botox)

bacteria causing widespread paralysis by inhibiting release of acetylcholine at neuromuscular junction

synaptic transmission

chemical signaling used to communicate between neurons

action potentials propagate with [blank] velocity

constant

concept of electrotonic spread

electrical inputs come at varying places in the neuron and passively spread this causes electrical current to leak out of the neuron over time, meaning that the signal could die out since it's being passively spread over a long distance with no reinforcement

role of the action potential in neurons

helping nerve signal travel along after electronic spread begins to fade away

endorphins

inhibits CNS neurons involved in perception of pain

substance P

involved in the perception of pain when tissue is injured

Gamma-aminobutyric acid (GABA)

major role in inhibitory CNS functions; at very low levels, could be indicated in seizures

acetylcholine

neurotransmitter with major role in excitatory PNS functions, allowing skeletal muscles to move regulates some ANS functions and CNS involvement with movement and attention

temporal summation

postsynaptic potentials are generated in the same neuron at slightly different times, adding up over time

spatial summation

postsynaptic signals add up continuously but at different sites on the neuron

glutamate

principal fast excitatory NT of the CNS; elicits neural changes associated with learning and development

norepinephrine

used by ANS, thalamus, and hypothalamus; associated with attentive functions and the fight or flight response