Neurons and Synapses [W2] Flashcards
Location of Ogliodentrocytes
central nervous system (CNS)
location of Schwann Cells
peripheral nervous system (PNS)
Location of astrocytes
brain + spinal cord, CNS
location of microglia
brain + spinal cord, CNS
Function of ogliodentrocytes
Create myelin sheath for axons in the CNS (can do multiple instead of one just single axons like Schwann cells)
function of Schwann cells
Create myelin sheath for individual axons in the PNS; help with axon regrowth in PNS
Function of astrocytes
regulate blood brain barrier, provide structural support, maintain env’t around synapses; also, involved in uptake and release of transmitters, modulate synaptic transmission and help repair nervous system
function of microglia
brain’s immune cells, remove/repair damaged tissue, release anti-inflammatory agents
function of protein channels in cell membrane
regulate mvmt of substances in/out neuron
Function of axons
transmits signals across distances
function of synaptic terminals
neurotransmitter release
function of dendrites
receive inputs from other neurons
Explain Galvani (1791). Importance?
electricity made frog’s leg twitch. helped est. electrical properties of neurons
Explain Helmholtz (1850). Importance?
Measured speed of nerve impulse @ 90ft/sec. helped est. electrical properties of neurons
Explain Young (1936). Importance?
Recorded electrical impulses in the axon (1mm diameter) of a giant squid. Helped est. electrical properties of neurons
Explain Hodgkin & Huxley (1952). Importance?
negative resting potential in squid axon; found that applying electrical stimulus triggers an action potential–> trigger was voltage change from - to + (depolarization)
What 4 main ions contribute to resting potential?
Na+, Cl–, K+, negatively charged proteins
What are the steps/stages that occur in action potential?
Opens Na+ channels –> Na+ enters cell, changing membrane potential –> K+ channel opens, K+ exits cell –>Na+ channels close, K+ ions still exiting ==> Repolarisation –> K+ channel closes slowly==>hyperpolarisation from too much K+ outside cell –> all channels close, return to resting potential
What is the negative resting potential?
-70mV
all neurons have a _______resting potential
negative
Which part of a neuron receives input from other neurons?
dendrites receive information from other neurons via synapses
As an action potential passes along the axon, the interior of the axon is first depolarized by the entry of________ and then repolarized by the exit of ___________
sodium ions; potassium ions
The conduction of an action potential along an axon is mediated by __________
voltage-gated ion channels
What are the Nodes of Ranvier?
spaces along the axon where there is no myelin sheath
The process of neurotransmitter release is called ________
exocitosis
What is the most prevalent excitatory neurotransmitter in the nervous system?
glutamate
What is the most prevalent inhibitory neurotransmitter in the nervous system?
GABA
What is a direct agonist drug?
A drug that activates post-synaptic receptors
What is a direct antagonist drug?
A drug that blocks post-synaptic receptors
What is the endogenous neurotransmitter that acts at cannabinoid receptors in the brain?
anandamide
What is are vesicles?
spherical structures at the presynaptic terminal that contain neurotransmitters ready to send out
What causes the release of the neurotransmitter into the synapse?
Depolarisation from action potential opens calcium channels in the presynaptic membrane. Calcium then travels to presynaptic terminals where it interacts with the vesicle and triggers the vesicles to fuse with presynaptic membrane, releasing the neurotransmitters into the synapse.
What happens to excess neurotransmitters?
Either degraded by enzymes or removed via transporter proteins
what is the function of autoreceptors?
They feedback whether there is too much or too little of a neurotransmitter being produced/released
How are neurotransmitters made?
Synthesized in soma or presynaptic terminal; all required different “ingredients” based on which neurotransmitter is being synthesized
What are metabotropic receptors? Do they respond quickly or slowly to transmitters?
receptors that are opened through a sequence of chemical events; responds more slowly to transmitters because of intermediate step
Example of a ionotropic receptor
GABA receptor
what are ionotropic receptors? Do they respond quickly or slowly to transmitters?
receptor that is part of a ligand-gated ion channel, binding of neurotransmitter causes the channel to open so ions can flow through.
What is saltatory conduction? Why is it beneficial?
When action potential jumps from one Node of Ranvier to the next. Beneficial bc it speeds up impulse and requires less energy to restore resting potential
Explain the experiment by Otto Loewi (1921). What does this evidence?
simulated heart beat in heart in second chamber sharing same surrounding fluid but otherwise not touching. Is evidence that chemical exchange allows neurons to connect with each other.
What is the voltage change as action potential passes?
-70mV to +30mV
What is kiss and run fusion?
When transmitters are released through transient fusion with pore in cell membrane. Vesicle retains its shape, entire contents may not be released.
What is full fusion (vesicles)?
Vesicle and membrane merge and entire contents of vesicle spill into synaptic gap. Takes longer to regenerate a vesicle than reuse
Explain the ‘lifecycle’ of a neurotransmitter, from synthesis to release.
neurotransmitters are synthesised in the soma or the presynaptic terminal. They are packaged into vesicles and transported through microtubules to the presynaptic terminal, where they stay until they are released through fusion into the synaptic cleft.
what is the soma of a cell?
the cell body, contains nucleus and mitochondria
what are dendrites?
extensions from the cell that receive information from other cells
what are glia?
non-neuronal cells found in the CNS and PNS
What are the notable glia in the CNS?
astrocytes, microglia, oligodendrocytes, radial glial cells, and ependymal cells
what are microglia? Function?
small cells that act as the immune system for brain; repair and remove damaged tissue
What are astrocytes? Function?
star shaped cells that provide structural support in the CNS, and regulate the blood brain barrier
What are ogliodendrocytes? Function?
cells that provide myelin insulation for axons in the brain
What are Schwann cells? Function?
cells that provide myelin insulation for peripheral neurons
How does action potential move along axon?
Self-perpetuates
def: concentration gradient
unequal distribution of particles/ions between intra and extra cellular fluids
Explain the effects of voltage and concentration gradient on Cl- and Na+ re: cell membrane
Cl- channels allow Cl- to pass through the cell membrane, but it’s harder for Na+ to cross the membrane. Concentration gradient pulls Cl- ions through channels in cell membrane but voltage gradient draws them back until the ions are in balance
What ions are more concentrated outside the cell?
Na+ and Cl-
What ions are more concentrated inside the cell?
K+, but can move freely
Can proteins move freely through cell membrane? Why/Why not?
No; too large
Depolarisation allows ___ ions to flow through, ___________ polarisation.
Na+, enhances/increases
def: neutrons
neutral atoms; no pos or neg charge
def: electrons
negatively charged particles that orbit atoms
def; protons
positively charged atoms
def: ion
An atom that has either a positive or negative charge (not neutral)
def: phospholipids
two lipids (hydrophobic) and phosphorus heads (hydrophilic)
How do molecules pass through the cellular membrane?
protein channels in the phospholipid layer
Cl-
Chloride ion
Na+
Sodium ion