WEEK ONE: ACTION POTENTIAL Flashcards
Membrane
surrounds the cell
nucleus
structure that contains the cells genetic material in the form of DNA
mitochondrion
structure that performs metabolic activities
ribosomes
protein synthesis
motor neurons
neurons that carry outgoing information from the brain and spinal cord to the muscles and glands
sensory neuron
neurons that carry incoming information from the sensory receptors to the brain and spinal cord
dendrites
branchlike parts of a neuron that are specialized to receive information
dendritic spines healthy vs intellectual disability
healthy: consistent branches,
intellectual disability: not many, inconsistent sizes
dendritic spines
short outgrowth that increase the surface area available for synapses
axon
the neuron extension that passes messages through its branches to other neurons or to muscles or glands
cell body
contains nucleus
myelin sheath
insulating membrane surrounding the axon in some neurons
increase speed
presynaptic terminal
end bulb or bouton point where an axon releases chemcials
afferent axon
brings info into a structure
efferent axon
carries information away from a structure
glia
cells found throughout the nervous system that provide various types of support for neurons
astrocytes
star shaped glia that synchronize the activity of the axons
play a role in nutrition, can withdraw nutrients form blood vessels to neurons
Shcwann cells
mylenate axons in PNS
microglia
cleaners
act as phagocytes, eating damaged cells and bacteria, act as the brains immune system
oligodendrocytes
form myelin sheath in CNS
mylonite more than one neuron at a time
radial glia
guide the migration of neurons and their axons and dendrites during embryonic development
blood brain barrier
blood vessels (capillaries) that selectively let certain substances enter the brain tissue and keep other substances out
BBB advantage
disadvantage:
ADV: keeps out viruses
DIS: keeps out nutrients
what chemicals cross BBB passively
small uncharged molecules (ie, oxygen)
what chemicals cross BBB by active transport
large molecules such as glucose, AA
purkinjie cells
found in the cerebellum
kenyon cells
from a honeybee
bipolar cells
found in retina of the eye
Santiago Ramón y Cajal was responsible for which of these discoveries?
The nervous system is composed of separate cells.
Which part of a neuron has its own genes, separate from those of the nucleus?
The mitochondria
What is most distinctive about neurons, compared to other cells?
Their shape
Which do dendritic spines do?
They increase the surface area available for synapses.
What does an efferent axon do?
It carries output from a structure.
Which of the following is a function of astrocytes?
Astrocytes synchronize activity for a group
of neurons.
Which of the following is a function of microglia?
Microglia remove dead cells and weak synapses.
Which of these can easily cross the blood–brain barrier?
A. Fat-soluble molecules
Which chemicals cross the blood–brain barrier by active transport?
Glucose and amino acids
What is the brain’s main source of fuel?
glucose
For the brain to use its main source of fuel, what does it also need?
Thiamine
MS
the glial cells in the central nervous system (CNS), particularly oligodendrocytes, are damaged, and the body’s immune system attacks the CNS.
brain matter
grey matter is on the outer layer (the cortex), and white matter is located deeper, inside the brain
spine: matter
Grey matter is in the center, forming a butterfly or “H” shape, while white matter surrounds it
Blood brain barrier
border
protection of CNS against viruses and dangerous chemicals
regulation of brain metabolism
polarization
difference in electrical charge between the inside and outside of the cell
selective permeability
some substances cross a membrane more easily than other substances do
sodium-potassium pump
a carrier protein that uses ATP to actively transport sodium ions out of a cell and potassium ions into the cell
concentration gradient
A difference in the concentration of a substance across a distance.
depolarize
reduce its polarization toward zero
threshold
the level of stimulation required to trigger a neural impulse
action potential
messages sent by axons
hyperpolarization
The movement of the membrane potential of a cell away from rest potential in a more negative direction
all-or-none law
principle that the action potential in a neuron does not vary in strength; the neuron either fires at full strength or it does not fire at all
propagation of the action potential
transmission of an action potential down an axon
voltage gated channels
open and close in response to changes in membrane potential
refractory period
a period of inactivity after a neuron has fired
absolute refractory period
the membrane cannot produce an action potential, regardless of the stimulation
relative refractory period
a stronger than usual stimulus is necessary to initiate an action potential
local neurons
neurons without an axon
graded potential
a membrane potential that varies in magnitude in proportion to the intensity of the stimulus
sodium potassium pump
3 sodium out
2 potassium into the cell
*active transport
binary signal
fire or don’t fire
electrical conduction
electrical message is passed on along the axon
does not travel down the axon, but it regenerates, so it doesn’t not weaken
temporal summation
repeated stimulation at the same location
spatial summation
synaptic input from several locations can have a-cumulative effect and trigger a nerve impulse
inhibitory post synaptic potential (PPSP)
hyper-polarization
excitatory post synaptic potential (EPSP)
depolarization
otto loewis experiment (1921)
stimulating the vagus nerve inhibited heart rate, and stimulating the accelerator nerve released increased heart rate
realized he was collecting and transferring chemicals, not loose electricity
synapses
neurons communicate by transmitting chemicals at junctions called synapses
excitation nt
glutamate
inhibitory nt
GABA
NT SYNTHESIS TABLE
top are precursors can get from food (milk, nuts etc)
and in cascade brain can convert NT into other NT
Modified AA cascade
- acetly coenzme a + chline =
ACETYLCHOLINE
catechoalamines
- phenylalaine (from diet)
- tyrosine
- dopa
- DOPAMINE
- NOREPI
- EPI
Indoleamines
- tryptophan
- 5-hyrdoxy
- SERATONIN
contrasts
ionotropic effects
controlled by Nt,
LIGAND-GATED
METATROPIC
nt initating a sequence of metabolic rxns ) G protein activating a second messager
metabotropi are ___ than ionotropic synapes
slower and longer
*sequence of events and last longer
binding to NT receptors
LSD binds to seratonin receptors
stimulutating release
MDMA releases dopamine/seratonin
blocking reuptake
ampetamine/cocain block reuptake of dopamine and seratonin and norepi
negative feedback
cannabinoids excite negative feedback receptors on the presynaptic neuron
4 drug effects
- binding to NT receptors
- stimulating release
- blocking reuptake
- negative feedback
When the membrane is at rest, are the sodium ions more
concentrated inside the cell or outside? Where are the
potassium ions more concentrated?
sodium are more concentrated outside of the cell
and potassium is more concentrated inside the cell
When the membrane is at rest, are the sodium ions more
concentrated inside the cell or outside? Where are the
potassium ions more concentrated?
the membrane is at rest, the concentration gradient tends
to drive potassium ions out of the cell, and the electrical
gradient draws them into the cell. The sodium–potassium
pump also draws them into the cell.
What is the difference between a hyperpolarization and a
depolarization?
depol = closer to zero
hyper = more negative
What happens if the depolarization does or does not reach
the threshold?
no AP occur
Does the all-or-none law apply to dendrites? Why or why
not?
The all-or-none law does not apply t
dendrites, becaouse they do not have action potentials.
As the membrane reaches the peak of the action potential,
what brings the membrane down to the original resting
potential?
After the peak of the action
potential, potassium ions exit the cell, driving the mem-
brane back to the resting potential. Important note: The
sodium–potassium pump is NOT responsible for return-
ing the membrane to its resting potential. The sodium–
potassium pump is too slow for this purpose.
When the neuron’s membrane is at rest, where are the sodium ions and potassium ions most concentrated?
Sodium is mostly outside and potassium is mostly inside.
- When the membrane is at rest, what are the forces acting on sodium ions?
A. Both the concentration gradient and the electrical
gradient tend to move sodium ions into the cell.
When the membrane is at rest, what are the forces acting on potassium ions?
. The concentration gradient tends to move potassium
ions out of the cell, and the electrical gradient tends to
move them into the cell.
- Which direction does the sodium–potassium pump move ions?
It moves sodium ions out of the cell and potassium
ions into the cell.
Under what conditions does an axon produce an action potential?
B. Whenever the membrane’s potential reaches the
threshold
If a membrane is depolarized to twice its threshold, what happens?
The neuron produces the same action potential it
would at the threshold.
To which part or parts of a neuron does the all-or-none law apply?
A. Axons
During the rising portion of the action potential, which ions are moving across the membrane and in which direction?
Sodium ions move in.
After the action potential reaches its peak, the potential across the membrane falls toward its resting level. What accounts
for this recovery?
C. Potassium ions move out because their channels are
open and the concentration gradient pushes them out.
What does the myelin sheath of an axon accomplish?
It enables action potentials to travel more rapidly.
- What causes the refractory period of an axon?
The sodium channels are closed.
