what are the 2 parts of the nervous system?
- central nervous system:
- brain and spinal cord - peripheral nervous system:
- everything else
what are the 2 types of cells in the nervous system?
- neurons:
- 100 billion of them
- allow for communication with each other through electrical signals - glia:
- 1 trillion of them but 1/10th the size
- form the myelin sheath of neurons
what are the components of the neuron?
- cytoplasm (liquid inside cell)
- nucleus (holds DNA)
- membrane (border of cell)
- mitochondria (make energy through metabolism)
- ribosomes (making of new protein)
- lysosomes
- golgi complex: secretion of waste
what is the definition of metabolism, catabolism, and anabolism
metabolism: creation or breakdown of molecules
catabolism: (breaking down bigger molecules into smaller one)
anabolism: (building bigger molecules from smaller ones)
what are the 2 reasons that there a membrane potential for all cells? (Voltage/Electrical Difference between IN and OUTside of cell)
- large and charged negative molecules trapped inside the cell (small, uncharged molecules (h20, O2, CO2) pass freely across membrane)
- depending on where ion concentrations are (Na+, K+, Cl-) inside vs. outside the cell creates an electrical difference from inside and outside
- all cells have ion channels embedded in membrane
- they allow ions to pass in and out of cell (Na+, K+, Cl-) and change the membrane potential (electrical difference between inside and outside)
- can only happen if the ion channel is open
What makes the Neuron different from other cells of the body?
they are excitable, their membrane potential can change very quickly and sharply with is a signal/information
Components unique to NEURONS:
- soma (cell body)
- dendrites (receive signals from another neuron)
- axon (sends signal to next neuron)
- presynaptic terminal (before the synapse)
- synapse (space in between 2 neurons)
- myeline sheath - wrapping around axon (glial cell forming myeline sheath, help move signal faster down axon)
- nodes of ranvier - help move signal faster down axon
do only vertebrates or invertebrates have myeline sheath?
vertebrates
what to know about glial cells?
- they form the myelin sheath
- in CNS: Oligodendrocytes wrap around axons
- in PNS: Schwann Cells wrap around axons
- Axons in invertebrates are not myelinated
- some, but not all, neurons in vertebrates are myelinated
how does the body cope with injury?
- mitosis - make new neurons with cell division
- regeneration - repair axons that have been cut
what happens after development with mitosis (as adult)?
neurons in both the CNS and PNS
lose their ability to undergo mitosis
which cells in both the CNS and PNS undergo mitosis?
Glial cells
In most animals what can only occur in the PNS, not the CNS
regeneration (natural repairing of cut axons)
- in PNS there are mechanisms for creating collagen around the injury to act as a “bridge” for axons to grow along
how is the electrical signal sent?
from one neuron to the next
(from the “presynaptic” -> “postsynaptic”
neuron)… or a muscle cell
space between neuron and muscle isn’t synapse it is called neuromuscular junction
do myelinated neurons have faster or slower speed of transmission?
faster (myelinated: 100 m/sec)
what is the membrane potential at rest (when nothing is happening)?
-70mV (inside of the neuron is more NEGATIVE than outside bc large, negatively-charged molecules trapped inside)
what are the concentration differences of electrically charged IONS across the membrane
Na+ outside > inside
K+ inside > outside
Cl- outside > inside
how do we balance the concentration of of Na+ K+ and C- ions across the membrane
pull for Na+ and C-
move inside and K+
to move outside…. “down” the concentration gradient (DIFFUSION)
How/why do Na+ ion channels open?
the process of neurotransmitters binding to receptors on dendrites end up opening ion channels for Na+
what is depolarization
membrane potential gets less negative or more positive
what happens if the depolarization brings the Membrane Potential to -55 mV
action potential occurs, and membrane potential changes from -55mV to +30 mV (more positive inside than outside)
what is hyper polarization?
membrane potential becomes more negative (harder to create action potential)
what is the nodes of ranvier?
it is in between chunks of myelin sheath and allows action potential to jump from ion channel to ion channel skipping the myelin sheath
what is the purpose of blood brain barrier?
to keep out viruses, bacteria in CNS
