chapter 3 Flashcards
cell type of nervous system
neurons and glia
Neuron
Responsible for communication; transmit, receive and integrate information
glia
support, nourish and protect cells, *they can be replaced unlike neurons
3 main parts of the neuron
dendrites, cell body or soma, axon
dendrite
branching region of neurons
cell body or soma
contains the nucleus, genetic blueprint that guides the cells functions or producing proteins and chemical messages
axon
“root” how it passes through (how its transmitted), moves along the axon, chemicals release at the end of the axon so the other cells get the message, covering the axon is a type of glia cell
Myelin Sheath
insulates axons and speeds transmission of signals, they are white, it is why we say “white matter” just glia cells , information and messages passed much quicker with the myeline sheath
multiple sclerosis
de-myelinating disease. auto immune disorders that attack the myeline sheath, problems with muscular movement, tend to come and go
hodgkin and huxley
1952, first ones to explain nerve impulse, won the nobel prize
hodgkin and huxley experiment
take squids (have large axons) can embed an electrode inside the neuron and outside to see what electro pulses are going on. fluid inside and outside the cell within the fluid there are electrically charged ions
resting potential
stable negative charge -70mV
neuron at rest
negative charge on inside compared to outside of cell
ions involved neural impulse
potassium (k+) inside of the cell, sodium (Na+) on the outside
Action Potential cause
spike caused by a change in the flow of the ions
action potential ion flow
little gates or channel all along the axon open when stimulated to create a change in ion concentration, Na rushed in, once it moves past K goes out, resetting the resting potential
What happens when the action potential moves along the axon
it reaches the terminal buttons which release neurotransmitters
threshold for action potential
-50 mV
Depolarization
Na+ ions rush into the cell making the inside of the cell positive
Repolarization
K+ ions rush out of the cell, resetting the charge making it negative
Hyperpolarization
during the time that so many k+ ions rush out of the cell it becomes more negative than the resting period, then the gates close and the concentration returns to resting potential
transmit action potential to other cells
the ion flow at one location creates a charge that affects the neighbouring regions that spark the action potential of the next region…
Speed of action potential
1 millisecond (100m/s)
Relative refractory Period
where you could create a new action potential but the cell needs more stimulation, during hyperpolarization. Extra work to generate another action potential, threshold is bigger because the cell is so negative, so you would need a lot of excitatory stimulation
Absolute Refractory period
depolarization refers to the fact that you cannot generate another action potential in the cell, no matter how strong the stimulus another action potential will not occur
all or none law
refers to the fact that if we get to the -50mV we will have an action potential if we dont we will get nothing
Characteristics of every action potential
same magnitude, same overall change is electrical energy were recording over the membrane, variable firing rate, travels extremely fast
Variable Firing Rate
different cells will fire action potential at different rates (how many times a second does this happen in a cell)
travels extremely fast
a myelin sheath allow for the information to move that fast 100m/sec, produce action potentials to code for different information. we need motor and sensory information to travel really quickly so that our body responds to prevent injury
Where are neurotransmitters stored
synaptic vesicles
Where are neurotransmitters released
into the synaptic cleft and binds to receptor sites, after action potential
Post-synaptic potential
neurotransmitter produces a change in voltage at receptor site–> Excitatory, inhibitory, not all or none, can have a small effect, doesn’t spread across the cell. NOT the same as action potential
Excitatory Post-Synaptic Potential (ESPS)
depolarizing effect, brings us closer to an action potential, if enough will cause an action potential
Inhibitory Post-Synaptic Potential (ISPS)
(hyper)polarizing effect, brings us further away from an action potential
Removal of neurotransmitter from the synapse
need to inactivate the neurotransmitter once its in the synaptic cleft; enzymes that will break down the neurotransmitter so it cant bind to the receptors on the post synaptic cell, take it back into the terminal buttoms and repackage them known as reuptake, because we want to retain that neurotransmitter
flow of neurotransmitters
- synthesis and storage of neurotransmitter molecule in synaptic vesicles
- Release of neurotransmitter molecules into synaptic cleft
- Binding of neurotransmitters at receptor sites on postsynaptic membrane
- Inactivation by enzyme or removal by drifting away
- Reuptake of neurotransmitters by the presynaptic neuron
Connection between neurons
pre-synaptic and the post-synaptic cells
long term potentiation (LTP)
once the cell has been stimulated there can be prolonged period of time when the connection is strengthened for hours, days, etc.
Pruning
refers the process by which excess neurons and synaptic connections are eliminated to increase efficiency of neuro transmissions
different classes of neurotransmitters
small molecule: developed and synthesizes using amino acids, fast acting, developed from our diet
Neuropeptide: protein developed by the cell that are synthesized and can be used as neurotransmitters
other: behave very differently, some that are gases, when neurotransmitters are needed they move along the cell
50 neurotransmitters
hard to figure out if a chemical is a neurotransmitter
Agonist
mimics neurotransmitter action. ex: Acetylcholine (agonist= nicotine)
Antagonist
opposes action of a neurotransmitter. ex: acetylcholine (antagonist= curare)
where do drugs have actions?
at neurotransmitter sites, some drugs will also bind at those receptor sites, act as a neurotransmitter (agonist), some will bind to the receptor site and oppose and prevent the action (antagonist)
Acetylcholine
alerting neurotransmitter, activates motor neurons controlling skeletal muscles. attention, arousal, memory. decrease as we get older, it is thought that this is why we get slower and memories are worse
Dopamine
pleasure transmitter, drugs that are abused usually related dopamine, voluntary movement , pleasurable emotions, decrease levels associated with parkinsons, overactivity at DA synapses associated with schiz
cocaine and amphetamines elevate activity at DA synapses
Serotonin
linked to depression, drugs prevent uptake of natural serotonin, involved in sleep/ tired/ eating/ aggression.
abnormal levels may contribute to depression and OCD
Norepinephrine
contributes to mood and arousal
cocaine and amphetamines elevate activity
What common neurotransmitters are linked to depression
norepinephrine, serotonin, dopamine