Nerv. System Basics and Action potential Flashcards
homeostasis
process by which biological systems maintain a stable internal environment despite external changes.
How does the nervous system respond?
via electrochemical messages relayed from the brain
How does the endocrine system respond?
via chemical messengers relayed through the bloodstream (hormones)
What are the two main types of cells found in the nervous system
Glial cells and Neurons
Glial Cells
comes from “glue” in latin
used for structural and nutritional support
Neurons
conduct nerve impulses throughout the body
supported by glial cells
basic unit of the nervous system
Dendrites
branches which accept nerve impulses from other neurons or sensory receptors and carry them towards the cell body
Cell Body
contains nucleus
site of metabolic reactions
processes nerve inputs
Axons
longer branches which carry nerve impulses away from the cell body
terminate in branched fibers
Myelin Sheath
A fatty layer surrounding each axon
insulates the neuron
speeds up rate of impulse transmission
Schwann Cells
Type of glial cell
Responsible for producing the myelin sheath around the axon
Nodes of Ranvier
Gaps between Schwann Cells
Electrical Impulses travel from node to node (saltatory conduction)
Axon Terminal
passes on electrical signals to the dendrites of an adjoining neuron
Myelinated Neurons
make up white matter
conducting nerve impulses
can regenerate after injury
Unmyelinated Neurons
make up the grey matter
processing information and generating nerve impulses
cannot regenerate after injury
Sensory Neurons
afferent
gather information from sensory receptors
transmits these impulses to the brain and spinal cord
Interneurons
found in brain and spinal cord
process and integrate incoming sensory info from sensory neurons
relay info to motor neurons
Motor Neurons
efferent
transmit info from brain and spinal cord ro muscles (effectors), glands, and other organs
What is the order of neurons in a typical Nerve Impulse
- Sensory Neurons (Input)
- Interneurons (processing)
- Motor Neurons (output)
Reflex Arc
A sudden, unlearned, involuntary response to stimulus
Immediate response (passes through interneurons in spinal cord) about 50ms
bypasses the brain
Summation
sum of multiple neurons leading to greater stimulation
Components of Action Potential/Nerve Impulse
has both chemical and electrical component (electrochemical impulse)
What are the four stages of a nerve impulse (in order)
- Polarized/Resting State
- Depolarization
- Repolarization
- Refractory Period
Polarized/Resting State
slight negative (-70mV) charge inside
slight positive outside
Sodium-Potassium pump maintains this charge, as well as large negative proteins inside
Sodium-Potassium Pump
3 Sodium ions out
2 Potassium ions in
creates ion gradient, with higher Na concentration outside and higher K concentration inside
Depolarization
Na+ gates open, Na diffuses freely across membrane, rushes in
membrane potential goes from -70 to +40mV
gates close when equilibrium reached
Threshold Potential
at -55 mV
impulse has to reach this in order to be depolarized
all or nothing, so it wont go if it doesn’t reach -55mV
What changes the intensity of a stimulus
increased frequency or number of nerve impulses
never increase the strength
Repolarization
K+ gates open, rushes out of axon ( or terminal check later)
brings charge back to negative, but now there is higher [Na+] inside the membrane
Hyperpolarization/Refractory Period
“overdone” repolarization brings charge to -90mV
can’t have another action potential until the charge goes back up to 70mV after hyperpolarization
the sodium-potassium pump restores to -70 mV after hyperpolarization
which neurons are faster at conducting nerve signals
Myelinated ( 120m/s) - because of Nodes of Ranvier
Unmyelinated (0.5 m/s)
