MIDTERM (first 3 weeks) Flashcards
what is the role of dendrites
receptors pick up signals from other neurons (neurotransmitters)
what is the role of soma
takes info from dendrites and stores it at the axon hillock - if the signal is strong enough it is sent to axons
what are the three parts of a neuron
soma, dendrites and axons
define neuron
cells that are specialised for long distance electrical signalling and intercellular communication
what is the role of the axon
signal (action potential) travels down the axons which is covered in myelin (to help prevent the signal from degrading)
why is the myelin covering helpful
prevents the signal from degrading
what is the role of axon terminals
when the signals reaches the axon terminal it causes the release of neurotransmitters (delivers to the next neuron, repeating the process)
what is the role of glia
support the activity of neurons but do not themselves participate in electrical signalling
what are the threee types of glia
astrocytes, oligodendrocytes, microglialcells
what is the function of astrocytes
to maintain
- an appropiate chemical environment
- secrete substances that influence the construction of new synaptic connection
what is the function of oligodendrocytes
oligodendrocytes lay down a laminated lipid rich wrapping called myelin around some axons - Myelin has important effects on the speed of transmission of electrical signals
- subsets of oligodendrocytes can retain neural stem cell properties and can generate new cells in response to injury or disease
what is the function of microglial cells
share properties ewith macrophages
secrete signalling molecules
can modulate local inflammation and influence whether other cells survive or die
what is the role of sensory systems
acquire and process info from the int. and ext. environments
what is the role of motor systems
respond to info by generating movements
what is the role of associational systems
mediate the most complex and least well characterised brain functions
cns
brain and spinal cord
what is grey matter
accumulation of cell bodies and neuropil in the brain and spinal cord
what is white matter
axon tracts and commissures
directional term: superior
above
directional term: inferior
below
directional term: anterior
in front of
directional term: posterior
behind
directional term: sagittal plane
separating left and right brain
directional term: coronal plane
across front of brain
what is the point of a semipermeable membrane
keeps everything thats needed inside, everything unwanted outside
what does the intracellular micro-electrode do
measures the electrical potential across the neuronal plasma membrane
what is the membrane potential
the difference in electrical charge between the inside and outside of a neuron
when at rest what ion is more prevalent inside the cell
K+
what is the resting membrane potential
-70mV
what does the sodium potassium pump do
transport protein that uses energy to constantly pump 3 Na+ ions out of the cell while pumping two potassium ion s into the cell
- more positive ions going out than in, membrane potential is kept negative
is resting mem. pot. + or -
-
what are the three types of electrical signalling
receptor potentials
synaptic potentials
action potenitals
what are receptor potentials due to?
the activation of sensory neurons by ext. stimuli e.g. light, sound, heat
- these neurons respond to touch w a receptor pot. that changes the resting pot. for a fraction of a second
what determine the amplitude of receptor potentials
the magnitude of sensory stimulus
what do synaptic potentials allow for
the transmission from one neuron to another
how do amplitudes vary in synaptic potentials
amplitudes vary to the number of synapses activated, the strength of synapses, the previous amount of synaptic
what are action potentials responsible for
long range of transmission of info. within the nervous system and allow the nervous system to transmit info to its target organs
what are the 4 phases of action potentials
rising phase
overshoot phase
falling phase
undershoot phase
what occurs in the rising phase
when threshold is reached na+ channels open allowing na+ into the cell = massive depolarisation of neuron
what occurs in the overshoot phase
reaches peak
Na+ channels close
K+ channels open
what occurs in the falling phase
repolarization (as K+ is coming back into cell)
what occurs in the undershoot phase
hyperpolarization - refractory period
what the two proteins associated with ion movement
active tranporters
ion channels
what do active transporters so
which actively move ions into or out of cells against their concentration gradients
what does ion channels do?
( proteins that allow only certain kinds of ions to cross the membrane in the direction of their concentration gradients
if the outside is increasingly positive, is it more or less attractive to positively charged K+?
less attractive
what is the electrochemical equilibrium
- where net movement stops when equilibrium is reached
- exact balance of two opposing forces
what does the balance of chemical and electrical forces at equilibrium mean?
The balance of chemical and electrical forces at equilibrium means that the electrical potential can determine ion fluxes across the membrane, just as the ion gradient can determine the membrane potential
if membrane potential is set at the equilibrium potential for K+ is there movement?
no net flux
if membrane potential is more negative than K+s equilibrium potential what occurs?
K+ to flow against its concentration gradient
how can the electrical potential across the membrane at equilibrium be predicted by?
Nernst equation
what is equilibrium potentials dominated by?
the ion with the greatest permeability
if the membrane was more permeable to K+, the membrane would approach _____?
-58mV
if the membrane was more permeable to Na+, the membrane would approach _____?
+58mV
- If K+ and Na+ were equally permeant, then the potential would be ______?
0mV
hodgkin hypothesised: the action potenital arises because _____________?
and how did they test this?
the action potential arises because the neuronal membrane becomes temporally permeable to Na+
- by removing Na_ from the external medium
what did Hodgkin and Katz find when lowering Na+ ?
by lowering the ext. Na+ the rate of rise and and the action potential and its peak amplitude all reduce
does lowering Na+ have any effect on resting membrane pot.?
no
what does the voltage clamp technique provide?
- voltage clamp technique: permits details characterisation of permeability changes asa function membrane potential and time
what does the transient increase in the permeability of the neuronal membrane to Na+ intitate?
action pot.
what must action potentials reach in order to occur?
threshold
what is the result of the early influx of Na+ ?
transient inward current
what is the result of the delayed efflux of K+ ?
sustained outward current
who developed the critical staining technique?
camillo golgi
what do gap junctions allow for?
for cytoplasmic continuity and the direct transfer of electrical and chemical signals between cells in the nervous system
what is the most important additional function of glia?
repairing nervous system damage - acting as stem cells - where they promote regrowth
what are dendrites primary targets for>
synaptic input from the axon terminals of other neurons
if a neuron has less elaborate dendritic branches do they transmit more or less info.?
less
what is the synaptic cleft?
the site of extracellular proteins that influence the diffusion, binding and degradation of the molecules
what provides the axon with structural integrity?
its distinct cytoskeleton
what is synaptic transmission?
the process by which the information encoded by action potentials is passed on at synaptic contacts to a target cell
what constitute a neuropil
a dense tangle od dendrites, axon terminals, and glacial cell processes
what fo afferent neurons do?
carry info from the periphery toward the brain or spinal cord
what do efferent neurons do
nerve cells that carry info away from the brain
what do interneurons participate in?
only in the local aspects of a circuit, based on the short distances over which their axons extend
within white matter, what are axons gathered into?
tracts that are more of less analogous to nerves in the periphery
what is a receptive field
the region in sensory space within which a stimulus elicts action potential response
