Lecture 6 part one (SECOND MIDTERM) Flashcards
How is the nervous system fast acting?
It uses electrical impulses
The nervous system is derived from what germ layer?
Ectoderm
The CNS is derived from…
The PNS is derived from…
CNS = neural ectoderm PNS = neural crest
Unlike the CNS, the PNS is always…
paired; spinal nerves and cranial nerves come out from the left and from the right
Somatic refers to the things you do _________ and visceral refers to the things you do __________.
consciously, unconsciously
Somatic sensory name:
Visceral sensory name:
Somatic afferent: skeletal muscle, joints, skin sensations
Visceral afferent: internal organ sensations
Somatic motor name:
Visceral motor name:
Somatic efferent: voluntary contractions
Autonomic Nervous System (ANS): controls itself
Somatic motor nerves send messages where?
Musculature of body wall (somatopleure)
Visceral sensory nerves receive signals from where?
Organs of splanchnopleure
examples: hunger, discomfort, full bladder, etc.
afferent:
efferent:
afferent: toward
efferent: away
4 divisions of the nervous system:
Somatic sensory
Somatic motor
Visceral sensory
Visceral motor
The way we refer to the visceral efferent division:
Autonomic Nervous System
2 divisions of the Autonomic Nervous system,:
Parasympathetic
Sympathetic
Basic component of the nervous system:
Neurons
Other cells that serve as supporting cells:
Glial cells
Neurons abilities:
- Can respond to stimuli
- Can conduct an electrical signal
Anatomy of a motor neuron Cell body: Dendrites: Axon: Telodendria: Synaptic terminals:
Cell body: expanded portion
Dendrites: processes that come off the cell body
Axon: longer process
Telodendria: axon divides into these
Synaptic terminals: at the end of telodendria
Where is the nucleus located?
The cell body
Where is the stimulus received?
Either by the dendrites or on the cell body itself; “On or near the cell body”
The axon is covered by a cell membrane. What is it called?
Axolemma
Direction of impulse:
Cell body > Axon > Telodendria > Synaptic terminals > next cell
What is used to communicate with the next cell?
Synaptic terminals
4 different types of neurons:
Anaxonic: no axon (in brain)
Bipolar: 2 axons (special senses, like in nose)
Unipolar: cell body, but just one axon in which the cell body is offset (looks like 2)
Multipolar: one cell body but many dendrites; one axon
What kind of neuron is typical for a motor neuron?
Multipolar neuron
What kind of neuron is typical for a sensory neuron?
Unipolar neuron
Proper name for unipolar neurons:
pseudounipolar neurons
IMPORTANT CONCEPT (in Noriega's words) Communication happens.....
ON OR NEAR CELL BODY
Stimulus:
Change in property of neuron cell membrane
What is myelin? What is it used for?
it is a fat that insulates & causes repression of signal degradation
How does the electrical signal usually enter?
via dendrites
How does the electrical signal usually leave?
via axon
What does myelin prevent?
- prevents the electrical charge from leaking out; “short circuit” (electrical barrier)
- it is a PHYSICAL barrier
In the PNS, myelin is produced by ________ cells called ___________.
neuroglial, Schwann
In the CNS, myelin is produced by _________ cells called ______________.
neuroglial, Oligodendrocytes
Where there is no myelin and the axolemma is exposed, there is a:
Node (of Ranvier) or Neuralfibro nodes
Another difference between Schwann cells in the PNS and Oligodendrocytes in the CNS is…
One single Schwann cell will only cover one portion of a single axon
Several processes coming off an Oligodendrocyte will cover multiple segments of multiple axons
*Both have insulating function!
A bundle of axons (neurons) in the PNS? In the CNS?
PNS: nerve
CNS: tract
What is a ganglion? Where is it?
A collection of cell bodies
PNS
What is a collection of cell bodies in the CNS?
Nucleus
Define a resting membrane potential.
Electrical charge across a cell membrane when the cell is at rest
If one side has a different charge than the other, it is said to be…
polarized
What is the electrical charge at rest?
-70mV
What does it mean to have an electrical charge of -70mV?
It is the different between the inside of the membrane and the outside of the membrane
(The inside is 70mV more negative than the outside)
What is the charge difference due to?
The differential distribution of charged ions on either side of the membrane
Sodium is actively pumped out of the cell, leaving more sodiums on the outside than on the inside. The pump that does this is:
the sodium potassium-exchange pump
What is the sodium-potassium exchange pump powered by? When doesn’t it work?
ATP
It’s always working (unless you’re dead)
Ratio of potassium that go in and sodium that goes out:
2 potassium in, 3 sodium out
What is the net movement?
1 positive charge gets pumped out; this is how you build a positive charge on the outside of the cell
The inside of the cell is ________ more negative than the _________.
-70mV, outside
Leak channels work to do what?
they establish a normal resting membrane potential; sodium is able to “leak” back into the cell or the potassium is able to “leak” back out of the cell
If the pump is always working, what will happen to the charge difference?
It will get bigger and bigger; -70 to -80 to -90 and so on
The sodium-potassium pump and leak channels work to reach…
equilibrium
The chemical gradient is what?
the concentration gradient
Despite its desire to go back out of the cell, potassium will want to stay in the cell because of:
the electrical gradient
What is stronger, chemical gradient or electrical gradient? What does this mean?
Chemical gradient
This means if you let potassium do what it naturally wants to do, it will leave the cell
If you combine the two gradients, you will get…
the electrochemical gradient
If the membrane were freely permeable to potassium ions, the outflow of potassium would continue until what was reached? What’s the value?
equilibrium potential; -90mV
If the membrane were freely permeable to sodium ions, the influx of sodium would continue until what was reached? What’s the value?
equilibrium potential; +66mV
Will become more positive on the inside
Learning catalytics:
Where is the sodium concentration higher?
If it’s just concentration gradient, which way will sodium want to go?
Based on electrical gradient, where will sodium want to go?
- Outside the cell
- Inside of the cell
- Inside the cell
What usually triggers an impulse?
A change in the electrical potential (the -70mV charge)
The change in the electrical potential is usually caused by…
A change in the cell membrane permeability
What factors can cause the permeability change of the plasma membrane?
- Can be cause by a stimulus
- Signal from neighboring cell
- Deformation of receptor cell of a special sense
Different gated-channels:
- Chemically gated (ligand-gated) channels
- Voltage gated channels
- Mechanically gated channels
Chemically gated…
open or close when they bind specific chemicals
example: the receptors that bind acetylcholine at the neuromuscular junction
Voltage gated…
open or close in response to changes in the membrane potential
If a stimulus is strong enough to trigger an impulse, it is called a:
threshold stimulus
A threshold stimulus is for what kind of channel?
Voltage gated channel
it is an electrical value
A graded potential just means…
as you move away from the center (the strongest change), the difference gets “smaller and smaller”
For voltage-gated channels at what mV do these events occur?
Opening of inactivation gate:
Opening of activation and inactivation gate:
Close of inactivation gate:
Opening of inactivation gate: -70mV
Opening of activation and inactivation gate: -60mV
Close of inactivation gate: +30mV
Spread of sodium ions inside plasma membrane produces a local current that does what?
depolarizes adjacent portions of the plasma membrane
