Brain Structure: Depolarization & Neurotransmitters

   
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  • Neurons: constructive unit of the nervous system; interconnected like electrical circuits
  • Made up of:
  • Soma (cell body): contains nucleus, keeps nerve cells alive (grey matter)
  • Dendrites: receiving portion of nerve cell- receiving end of cell
  • Axon: sends impulses away from the cell (white matter)
  • Dendrites and axons are all interconnected; vary in shape and size
  • Glial cells: hold neurons in place; make nutrients, absorb waste
  • Tripatite Synapse: synapse between dendrite , axons, synapse
  • Blood-brain barrier: glial cells that prevent waste from entering the brain
  • Neurons do two important things: generate electricity and release chemicals
  • Neurons= batteries; inner structure in salty solution encased in inner membrane; VERY CONDUCTIVE
  • Positive Na, more positive K on outside= resting potential: -70mV (polarized)
  • Action Potential: sudden reversal of voltage along neuron membrane to cause depolarization (-70mV – +40mV)
  • Graded potentials: incoming stimulation not strong enough to complete depolarize a cell
  • *MUST MEET ACTION POTENTIAL THRESHOLD to cause action potential -> depolarization
  • All-or-none law: neurons must fire at max intensities or not at all
  • Ion channels: graded potentials move ions through these channels (Na= +) which when done enough can depolarize the cell (action potential threshold: -55mV)

Depolarization Steps:

1) Negative charge inside of membrane (due to K ions) positive charge on outside (Na), more negative than positive.

2) Action potential causes the sodium channels to open and Na ions flow into inner membrane; K+ ions flow out.

3) Sodium-potassium pump depolarize cell during refractory period; 2:3 Na:K pumped into cell

  • Actions potential do not vary but the rate/ number of neuron stimulated will result in high-intensity stimulation
  • Axons covered by myelin sheath= insulation/ protective
  • Nodes of Ranvier: section of axon where myelin sheath are not present or absent. Impulses hope along these nodes to get better conductivity and speed.
  • Synapse: connection between neurons (axons and dendrites)
  • Neurotransmission occurs between axon and dendrites in synaptic cleft

5 steps

  • Synthesis- chemicals have made within the neuron
  • Storage- these chemicals are stored within the synaptic vesicles
  • Release- chemicals move across the synaptic cleft from presynaptic neuron (axon) to post synaptic neuron (dendrites)
  • Binding: the vesicle bind to the receptor sites on the neurons. These chemicals will (a) depolarize the neuron by exciting it or (b) hyperpolarize the neuron and inhibit it.
  • Deactivation: shuts off, is depolarized

nervous depolarization Brain Structure: Depolarization & Neurotransmitters

  • Exciting Chemicals: Glutamate, Acetylcholine, Norepinephrine, Dopamine
  • Inhibiting Chemicals: GABA, Serotonin, Dopamine
  • Acetylcholine -> (motor movement, sleep, dreaming, muscle) Alzheimer’s disease (lack of)
  • Botulism: blocked Ach, paralysis
  • Dopamine -> Parkinson’s disease (lack of) can be treated; also treats schizophrenia (overload)/ delusions
  • Serotonin (5HT) -> sensitivity to it linked to depression (due to undersupply of it)
  • Endorphins -> reduce pain
  • Neuromodulators -> widespread effect
  • Drugs can mimic some neurotransmitters (block uptake, bind at stop TP)
  • Sensory Neurons: sent info the brain/ spine
  • Motor Neurons: send impulses from brain/ spine to muscles/ organs
  • Interneurons: connective neurons

Neurotransmitters Brain Structure: Depolarization & Neurotransmitters

CNS: brain/ spine                         PNS: everything else

  • Somatic Nervous system: voluntary movements (muscles, senses)
  • Autonomic Nervous system: controls glands, heart, etc.
  • Fight-or-Flight: Sympathetic: arousal to stress Parasympathetic: recovery from stress [HOMOEOSTATIS]
 

Citation


St. Rosemary Educational Institution. "Brain Structure: Depolarization & Neurotransmitters." http://schoolworkhelper.net/. St. Rosemary Educational Institution, Last Update: 2014. Web. Retrieved on: Friday 18th April 2014. http://schoolworkhelper.net/brain-structure-depolarization-neurotransmitters/.
2 responses to “Brain Structure: Depolarization & Neurotransmitters”
  1. โมนาวี says:

    Thank you so much for sharing.

  2. stonco mthoxy says:

    thank you your web notes on neurotransmitter helped me alot

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