Communication within the Nervous Service Flashcards
What is the nervous system made of?
- Neuroscientist Santiago Ramon y Cajal identified that the nervous system was composed of distinct cells using various strains
~ Nissl stain: only labels cell bodies
~ Golgi stain: labels cell bodies AND dendrites/axons - “The Neuron Doctrine”
What are the 3 main parts of a neuron?
dendrites, soma (cell body), and axon
What are dendrites?
- receive signals from other neurons
What is a soma (cell body)?
- contains normal cellular stuff (nucleus, etc)
What are axons?
- transmit (sends) signals to other neurons
What is unipolar?
- contains one axon
What is bipolar?
- contains one axon and one dendrite
What is multipolar?
- contains one axon and multiple dendrites
Sensory neurons
- directly receive information from the world around us
Interneurons
- the “middleman”
- processes incoming sensory information and plans/executes the response
Motor neurons
- connects to muscles and leads to movements/behaviors
Other types of neurons
- pyramidal and stellate neurons
What are the two types of signals in the nervous system ?
electrical and chemical
What does electrical signals do?
- action potentials
- typically used within a neuron ~ one side to another
What does chemical signals do?
- neurotransmitters
- typically used between neurons
What are the main players in the electrical signal?
- Ions (something that has a charge)
~ Sodium (Na+)
~ Potassium (K+)
~ Chloride (A-) - other anions (A-)
A cell at rest, what is the cell membrane?
- it is a fence with gates around the cell
- gates in cell membrane are called channels
A cell at rest, what is it resting potential?
- a voltage difference between the inside and outside of the neuron
~ - 70 mV, will always be negative in the inside
What are the two main forces at work with resting potential?
- concentration gradient (more goes to less)
- electrostatic force (opposites attract, like charges repel)
What is the starting arrangement in resting potential?
- Na+ is outside
- Cl- is outside
- K+ is inside
- A- is inside
What does the stimulus do when at rest?*
- opens Na+ channels
- Excitatory Post- Synaptic Potential (EPSP)
- Na+ enters the cell
What is threshold?
- usually set at approximately -55mV
- action potentials are all or none
- once it reaches threshold, an action potential is guaranteed
What are voltage gated channels?
- triggered by a change in voltage
- Na+ channels open and Na+ floods the cell called depolarization
When at the peak, how does K+ feel?
- Na+ channels close
- K+ channels open and leaves the cell called repolarization
- it overshoots the -70 mV resting potential called hyperpolarization
What happens when the cell is getting back to rest?
- the Na+/K+ pumps 3 Na out and 2 k in
- helps to “reset” conditions to the original resting potential state so that the neuron can have another action potential
What are the three other parts of an axon?
1) axon hillock
2) Myelin Sheath
3) Nodes of Ranvier
What does the axon hillock do?
- the beginning of the axon
- where the action potential begins
What does the Myelin Sheath do?
- fatty tissue for insulation
What does the Nodes of Ranvier do?
- breaks in the myelin (VERY important)
What does the saltatory conduction do?
- impulse moves down the axon
- passively moves through myelinated axons
- regenerated at the voltage channels in each node of Ranvier
What is at the end of an axon?
- terminal buttons
What is terminal buttons?
- contain vesicles of neurotransmitters
- when the action potential arrives at the end of the axon, Ca2+ is released
Ca2+ leads to exocytosis of the vesicles
What happens in the synapse?
- neurotransmitters cross the synaptic gap and bind to channels on receiving neuron dendrites
~ ligand gated channels - if the input is enough to reach threshold, the process repeats
What does the neurotransmitter also do?
- instead of opening Na+ channels, neurotransmitters can also open K+ or Cl- channels
- brings the voltage of the receiving neuron further away from threshold called an Inhibitory Post-Synaptic Potential (IPSP)
What is Temporal Summation?
- the combination of postsynaptic events that leads to an action potential or not
- each receiving neuron receives input from multiple presynaptic neurons
- if one synaptic is repeatedly stimulated, that can get the receiving neuron passed threshold
What is Spatial Summation?
- if multiple synapses together stimulate a neuron, the combination of them can get the receiving neuron passed threshold
What are Ionotropic receptors?
- single step receptor
- fast acting
- neurotransmitter binds and opens channel
- ions flow through the open channel
What are Metabotropic receptors?
- multi- step receptors
- slow acting
- uses second messengers
~ longer lasting impacts than ionotropic receptors
