Lecture 2: Neural tissue and membrane potentials Flashcards
What are neural tissue?
they are the structure and the maintenance of neurons.
They are a functional classes of neurons
Presence of glial cells
Membrane potentials
Basic principles of electricity
the resting membrane potential
how many neurons and synapses are induced in the brain?
100 billions neurons and 1000 millions more than stars synapses
What are the major divisions of the nervous system?
it include two main part the central and the peripheral nervous system. IN the peripheral nervous system there is sensor that are body movement and autonomic which includes involentory system heart beat. Parasympathic is relax and sympathic is actif.
What are the differents functional parts of the neuron?
the dendrites are extending the branch and are forming a tree it is a mini computer; theyr receive information via neurotransmitters.
The axons conducts action potentials by sending signals towards axon terminal
Initial segment (axon hillock)= AP trigger zone
what are the different function of Glial cells?
Glia = glue so they are supporting cells of CNS and the PNS. there is 90% of cell in CNS with a 50 % volume
They are mirror support cell that hold the nervous system together by providing support and metabolims support. They surround the soma, axon and dendrites
What are astrocytes?
They are a type of glial cell of a star shape with ionic homeostasis it enveloppe synapses, they have a plasma neuron transporter like glutamamte release. It promote myelinated activity of oligodendrocytes; mediated neurovascular coupling; nervous system repairs
What are oligodendrocytes?
Myelinate multiple CNS axons by providing trophic support it is composed of myelin composed of highly compacted layers (20-200) of modified PM. THey form individual myeline sheet on one axon where the compact myelin speed up conduction (electrical insulator)
NOdes of ranvier
spaces between adjacent section of myelin- axon PM exposed to ECF saltatory conduction
What are schwann cells
myelinate PNS axons
Nuclei closely apposed to axon
Pain and temperature fibers are unmyelinated
Non-myelinating SCs can myelinate if triggered by neurons
What is the decsription of microglia?
microphage-like cells that reside in the CNS; proliferate and activate in response to injury
The ependymal cells line the fluid filled cavities of the brain; by producing CSF
what are the axonal transport doing?
anterograde transport=move cargo toward axon terminal
while the retrograde= toward cell body where the cytoplasm glimia goes from axons back to cell.
Two class exist A= microtube 1 min/day and B=divers protein 6m/day
Anterograde
synaptic proteins
Neurotransmitters
Certains mRNAs
retrograde
growth factors
Functional classes of neurons
groups of efferent and afferent neurons form the nerves of the PNS (they are bundled together)
A nerve fiber is a single axon, and nerve is a bundle of axons
the interneuron connects neuron within the nervous system (200 thousands). there is three classes of neurons
what do the synaptic inputs include?
Axo-dendritic, axo-somatic ansd axo-axonic = not contribute to action potetial in post synaptic neuron inhibitory or excitatory
Presynaptic= a neuron that conduct a signal towards a synapses
Post synaptic= One that conducts signal away from the synapse
A single neuron can be post synaptic to one cell and presunaptic to another cell
insulator
substance with high electrical resistance
conductor
substance with low electrical resistance
Ohm’s Law
Current proportional to the potential difference and inversely proportional to the resistance (hindrance to charge flow)
basic principles of electricity
opposite charges attract each other and will move toward each other if not seperated by some barrier. in biological systems the charges seperation is small(mV)
electrical potential
seperate charges have the ability to do work
potential difference
difference in charge between two points measured in volts(v)
what is the concept of Na+/K+ ATPase
it establishes concentration gradients of Na+ and K+ accross the plasma membrane (high Na+ outside and high K+ inside)
recall that the pump uses up to 40% of the ATP produced by cell
At a steady state, ion fluxes through leak channels and the activity of the pump balance each other
what distribution of ions in a nerve cell?
Na+, K+ and Cl- are present in the highest concentration membrane permeabilit to each is independently determined
Na+ and Cl- are out and K+ in
Other protein like ions of Mg2+, Ca2+, H+, HCO3-, amino acids and protein in ICF and ECF
equilibrium potential consider a membrane that is permeacble only to K
no potential difference because (+) and (-) ions are equal and channels are closed. If K+ channels open K+ wil diffuse from C2 to C1. THe C1 will have an excess of (+) charges and C2 an excess of (-) charges. Additional charges seperation. The build up of (+) charges in C1 and (-) charges in C2 produce an electrical potential that exactly offsets the K+ gradient. The memebrane potential at which the K+ k+ flux due to concentration diff become equal but opposite
in a equilibrium potential considering membrane that is permeable to Na+
the initail chanel close to transfer more positive charge right more negative charge on the left the value depend on the sodium ion concentration
what happens if we increase concentration of Na+ in C1
it will be a bigger downhill
what happens if we increase concentration of K+ in C2
ions flow down to its concentration gradient
Nernst equation
describe the equilibrium potential for any ion species
it needs to know the concenration outside and inside log less than one gave negative value
resting memebrane potential
-70 mV inside membrane slightly more negative than the outside. it represent the cells at rest depending it can be -65.Where the membrane is said to be polorized
charge separation across the plasma membrane
voltage occurs only at membrane surface. The tiny excess of (-) ions along the inner surface of the PM and (+) ions around the outside. THe excess x=charges collect at plasma membrane and are attracted to ech other. THe bulk of the ECF and ICF remains electrically neutral.
Leak channels generate the resting potential
membrane potenial depends on the difference permiability of the plasma membrane to these ions . the difference in K+ and Na+ concentration inside and outside cells. They are integral memebrane proteins that are selective ion channels- some always open. In an actual neuron they are more open K+ leak channels than Na+ leak channels the PM is 25 times more permeable to K+ than to Na+
force influencing Na+ and K+ at rest
because it is more permeable to potassium it open sodium channels. The Na+ go inward while the K+ goes outward. The greater permability and movement of K+ maintains the resting memebrane potential at a value near Ek.
Goldman-Hodgkin-Katz equation
use to calculate cell to know the membrane potential will be . Chloride is in the numerator instead of the denominator. This is because it is a negatively charged ion.
