Sem. 1 - Unit 2 Flashcards
neuron
nerve cells
cell body
the cell’s life-support control center
soma
cell body
dendrites
receive messages from other cells
axon
passes messages away from the cell body to other neurons, muscles, or glands
myelin sheath
covers the axon of some neurons and helps speed neural impulses
glial cells
“glue cells” - provides nutrients and insulating myelin, guides neural connections, and mop up ions and neurotransmitters
action potential
a neuron sends a message by firing an impulse, called the action potential
threshold (of excitation)
if excitatory signals exceed the inhibitory signals by a minimum intensity, or threshold, the combined signals trigger an action potential
resting potential
1.) Inside of the neuron is more negative compared to the outside.
2.) This negative charge is due to uneven distribution of ions (charged particles) like sodium (Na⁺) and potassium (K⁺).
3.) Sodium-potassium pumps move 3 Na⁺ ions out of the neuron and 2 K⁺ ions in, helping maintain this charge difference.
4.) The resting potential is typically around -70 millivolts (mV).
This electrical difference is crucial for the neuron to be ready to send signals when triggered.
In short, the resting potential keeps the neuron “charged” and ready to fire.
refractory period
Neurons need short breaks (a tiny fraction of an eyeblink). During a resting pause called the refractory period, subsequent action potentials cannot occur until the axon returns to its resting state. Then the neuron can fire again.
all-or-none response
a neuron’s reaction of either firing (with a full-strength response) or not firing.
How do we distinguish a gentle touch from a big hug? A strong stimulus can trigger more neurons to fire, and to fire more often. But it does not affect the action potential’s strength or speed.
depolarization
The loss of the inside/outside charge difference, called depolarization, causes the next section of axon channels to open, and then the next, like falling dominos. This temporary inflow of positive ions is the neural impulse—the action potential.
synapse
The junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron. The tiny gap at this junction is called the synaptic gap or synaptic cleft.
neurotransmitter
Chemical messengers that cross the synaptic gaps between neurons. When released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether that neuron will generate a neural impulse
Acetylcholine (Ach)
Enables muscle action, learning, and memory
With Alzheimer’s disease, ACh-producing neurons deteriorate.
Adrenaline/Epinephrine
Dopamine
Influences movement, learning, attention, and emotion
Oversupply linked to schizophrenia. Undersupply linked to tremors and decreased mobility in Parkinson’s disease.
GABA
A major inhibitory neurotransmitter
Undersupply linked to seizures, tremors, and insomnia.
Glutamate
A major excitatory neurotransmitter; involved in memory
Oversupply can overstimulate the brain, producing migraines or seizures (which is why some people avoid MSG, monosodium glutamate, in food).
Norepinphrine
Helps control alertness and arousal
Undersupply can depress mood.
Oxytocin
Oxytocin is a hormone and neurotransmitter that plays a key role in social bonding, emotional regulation, and certain physiological processes.
Serotonin
Affects mood, hunger, sleep, and arousal
Undersupply linked to depression. Some drugs that raise serotonin levels are used to treat depression.
Substance P
involved in pain perception and inflammation