What are the two major divisions of the nervous system? Name the three subdivisions of the PNS, and tell how they differ in functions. What are the two subdivisions of the Motor pathway system?
Central Nervous System (CNS) and Peripheral Nervous System (PNS)
Autonomic (involuntary). Within this, there are Sympathetic (Fight or Flight) and Parasympathetic (Rest and digest).
What is neuroglia? How do these cells compare (in structure, number, and function) to the neurons. What are the functions of each of the neuroglia? Which ones are in the CNS and which ones are in the PNS?
Neuroglia are cells that support and protect neurons
There are more neuroglia than neurons, they don't have dendrites or axons.
Astrocytes (CNS) - Forms blood brain barrier, protects neurons, allow the exchange of nutrients and waste
Oligodendricites - Mylinate the CNS
Epidymal (CNS) - Circulate the cerebral spinal fluid
Microglia - Eat debris in the CNS
Satellite and Schwann Cells are in the PNS.
Name the 3 types of neurons (based on structure).
Where are interneurons or association neurons located?
In the spinal cord
Describe the structure of a typical neuron. Identify as to structure and function: a cell body; dendrite; axon; microtubules; Nissl bodies; axon hillock.
Dendrites coming into cell body
cell body contains the nucleus goes into the axon starting with the axon hillock
the axon travels down to axon terminals
What is axonal transport? What is the primary function of slow axonal transport vs fast axonal transport?
Axonal transport is a cellular process responsible for movement of mitochondria, lipids, synaptic vesicles, proteins, and other cell parts (i.e. organelles) to and from a neuron's cell body, through the cytoplasm of its axon
Motor neurons are located where? Sensory neurons are located where?
Everywhere except the brain
You may recall that a muscle fiber is an entire muscle cell; is a nerve fiber an entire neuron? (explain)
No because the neuron consists of many other things that make up the neuron (dendrites, axons, cell bodies, axon terminals)
What is the role of the Schwann Cell in the formation of the myelin sheath. What is the neurilemma? What is a node of Ranvier? Are nodes of Ranvier in both the CNS and the PNS?
Schwann Cell wraps around the axon to form the myelin sheath.
Neurilemma is the plasma membrane of a neuron
Ranvier is the space between mylination
What advantage does having a myelin sheath give to a nerve fiber?
Means that action potential doesn't have to travel down the entire axon, just jumps from node to node.
Describe the importance of the Schwann cells in regeneration of the nerve fiber following injury.
Schwann cells can point the neuron in the right direction so it can regrow to the proper receptor sites.
What gives peripheral nerves their white appearance?
Exactly what is a nerve?
A bundle of neurons that travel to and from the same place.
Are nerve fiber in the CNS mylelinated? Do they have a neurilemma?
Do CNS nerve fibers generally regenerate?
What parts of neurons are found in gray matter? White matter? Why is it white?
Cell bodies found in gray matter
Because the tissue is composed of fatty tissue.
How are electrical potentials of cell membranes measured?
Describe two conditions that allow maintenance of the resting membrane potential. How are concentration gradients involved?
The fact that the cell membrane is relatively negative and they are charged ions inside and outside the cell.
Concentration gradients involved because K+ ions are inside, Na+ ions are outside. Keep polarity of cell in check.
What is an electrochemical gradient?
spatial variation of both electrical potential and chemical concentration across a membrane.
What is membrane permeability?
Only allows certain things through.
What are gated channel? There different gated channels, which channels are regulated by neurotransmitters?
Channels that are somehow opened to allow specific ions to enter and exit.
Is the resting membrane of a nerve fiber more permeable to sodium ions or to potassium ion?
Is the sodium-potassium pump and active or passive process?
How is the sodium-potassium pump related to the resting potential of the nerve fiber?
In order to get back to polarization, they have to pump in 3 Na out, 2 K in
What ions are pumped out the cell when the Na/K pump is activated?
3 Na out, 2 K in
What is the most immediate effect of application of a threshold stimulus to a nerve fiber membrane?
Define excitability. What kinds of cells possess excitability?
Able to receive impulse from action potentials
Describe the ionic basis for an action potential (depolarization). What is the ionic basis for repolarization? What is hyperpolarization? What ions are involved?
Depolarization - Potential difference becomes smaller or less polar. If extracellular concentration of K+ increases, there is less gradient between inside and outside.
Hyperpolarization - Potential difference becomes greater or more polar. If extracellular concentration of K+ decreases, steeper gradient between inside and outside
What is the refractory period (absolute and relative)? What are the ligand gated channels doing at this time?
Absolute Refractory Period - complete insensitivity exists to another stimulus. Voltage gated Na+ Channels open and close.
Relative Refractory Period - follows the absolute period, membrane is more permeable to K+ because many voltage gated K+ channels are open.
Which channels are activated for depolarization in an action potential?
Voltage Gated Na+ Channels
What is a graded potential? Can it travel a long distance? Why or why not?
A change in the membrane potential that is localized to one area of the plasma membrane. Also known as local potentials.
Cannot travel long distances because they spread in a decremental fashion. They rapidly decrease in magnitude as they spread over the surface of the plasma membrane (teacher's voice in a large lecture hall)
What principle is applied to transmission of a nerve impulse (action potential)? What is a threshold stimulus? What is the ionic basis for threshold?
Threshold Stimulus is the all or none principle. Resting potential -55mv. Has to bring it positive with K+ ions.
Voltage Gated K+ Ions open up which allows K+ ions to enter the membrane.
What is salutatory conduction of an action potential? Does it occur in all nerve fibers? How does diameter of a nerve fiber affect speed of conduction?
Salutatory conduction of an action potential is when you jump from node to node.
Axons are classified into 3 groups according to the relationship between diameter, myelination and propagation speed: define Type A, B and C fibers.
Type A - large-diameter, myelinated. Conduct at 15-120 m/s. Motor neurons supplying skeletal and most sensory neurons
Type B - medium-diameter, lightly myelinated. Conduct at 3-15 m/s. Part of ANS
Type C - small-diameter, unmyelinated. Conduct at 2 m/s or less. Part of ANS
How are nerve impulses transmitted across synapses? Compare this to transmission of an impulse from nerve fiber to muscle fiber. Is transmission of the impulse across a synapse one-way? What role does calcium play in the release of a neurotransmitter?
Calcium has to go into the synapse to stimulate the vessels to open.
What is a presynaptic neuron? Postsynaptic neuron? Define converge, divergence of neurons.
Presynaptic - The neuron that sends the action potential to the next dendrite
Postsynaptic - Receives the message
Convergence of Neurons - First one neuron is influenced by many others, resulting in a convergence of input.
Divergence of Neurons - When the neuron fires, the signal is sent to many other neurons, resulting in a divergence of output.
What is the role of a neurotransmitter? What is Ach? What are cholinergic synapses? What kind of transmitters are dopamine and serotonin?
To travel across the synapse and get the action potential to the next neuron
Ach is acetylcholine
Cholinergic synapses -
What is an EPSP and a IPSP? Are these graded potentials, action potentials, or can they be both?
EPSP - Excitatory Post Synaptic Potential; potential of the cell to reach threshold again after it has been through a cycle.
IPSP - Inhibitory Post Synaptic Potential; Hyperpolarize on purpose to prevent a response to every stimulus.
If a neuron synapses on a second neuron and drives the resting membrane potential further from threshold, what is this called? Where does it occur?
IPSP, Inhibitory Post Synaptic Potential.
What is summation? Temporal and spatial summation result in what?
Certain stimulus happens repeatedly, and adds to threshold in order to get an action potential.
Results in threshold
What is a monosynaptic reflex? Name the elements necessary in a polysynaptic reflex arc.
Takes one neuron to affect the other neuron and dictate a response.
Receptor, sensory neuron, control center, motor neuron, effectors
How does nerve tissue respond to injury? What cells are responsible for the repair? Where can it occur?
In CNS, it doesn't heal.
In PNS, if mylineation cells are still in tact, they will reform a path for the neuron to grow.
Schwann Cells or Oligodendricites