L1 Neurons And Action Potential Flashcards
Name the 2 types within the peripheral nervous system
Autonomic (level of arousal) and Somatic (control of body movements)
What are the 2 types of autonomic nervous system
Sympathetic and parasympathetic
Describe the 4 main parts of a multipolar neuron
Soma (cell body), dendrites (like tree branches), axon, terminal buttons
What do dendrites do?
Receive info from terminal buttons of other neurons
What is a synapse?
A junction between the terminal button of an axon and the membrane of another neuron.
What is an axon?
The long, thin, cylindrical structure that conveys information from the soma of a neuron to its terminal buttons.
What is the difference between a bipolar and a unipolar neuron?
Bipolar = A neuron with one axon and one dendrite attached to its soma. Is primarily found in sensory systems (for example, vision and audition) Unipolar = A neuron with one axon attached to its soma; the axon divides, with one branch receiving sensory information and the other sending the information into the central nervous system. found in the somatosensory system (e.g. touch, pain)
What is a synapse?
A junction between the terminal button of an axon and the membrane of another neuron. The connection from one neuron to another (they don’t touch).
What does the myelin sheath cover?
The axon(s).
What forms the myelin sheath in the CNS?
Oligodendrocytes. Has small gaps called “nodes of Ranvier”. Each Oligodendrocyte is attached to several axons.
What forms the myelin sheath in the PNS?
Schwann cells = same role as oligodendrocytes, but only 1 per axon.
What is the Action Potential?
A brief electrical message which travels down the neuron’s axon. “Transient change in electrical charge across a neuron’s membrane”.
What the the 3 ions in cell fluid?
Sodium (Na+), Potassium (K+), Chloride (Cl-)
What is the value of the resting potential within the neuron?
- 70 mv
During action potential what does the charge of the neuron change to?
+ 40 mv
What is the force of diffusion?
Ions move from area of higher concentration to area of lower concentration.
What is electrostatic force?
Two ions with the same charge repel each other. Two ions of different charge attract each other.
Which ion has both diffusion and electrostatic charge forces moving from outside to inside the neuron?
Na+ Sodium - concentration outside neuron is higher and it is +ve charged so attracted to the -ve chanrge of the neuron
Why doesn’t Na+ move into the neuron at rest?
- Neuron membrane (at rest) is not very permeable to Na+
2. Some Na+ which does leak into the neuron but is removed by sodium potassium transporter.
What happens to the Na+ (sodium) channels when the neuron receives a signal?
They open and Na+ enters the neuron.
How is the action potential initiated?
It reaches the threshold of excitation (-55 mv)
What 2 things happen when an action potential fires?
- Electrical signal goes down the axon, reaches the terminal button and becomes a chemical message (neurotransmitter)
- More Na+ channels open & Na + rushes into cell, causing the inside of the cell to become +40 mv relative to the outside of the cell.
How does the neuron move back to the resting potential?
K+ (potassium) exits the cell as the inside is now +vely charged and the K+ channels have opened. Electrostatic pressure and force of diffusion pushes it out of the neuron.
What is saltatory conduction?
Conduction of action potentials by myelinated axons. The action potential appears to jump from one Node of Ranvier (gaps in the myelin sheath where the neuron is exposed to extracellular fluid) to the next. Conduction is faster in myelinated axons vs unmyelinated.
What is the rate law?
The rate of firing determines the strength of a stimulus. The size of AP doesn’t vary - the frequency does.
What happens during the refractory period during the action potential?
Sodium channels do not allow any more sodium to enter the cell and cannot be stimulated again until they reset (when the potassium channels close).
How is action potential conducted in both myelinated and unmyelinated neurons?
The Na+ channels, just ahead of where the action potential is at, open.
What the the 2 advantages of myelin?
Speeds conduction (jumps using Nodes of Ranvier) and reduces interference from adjacent neurons (sodium can only enter at the Nodes of Ranvier)
What stain identifies a neuron?
Golgi stain
What do glial cells do?
Act like glue. Hold things in place
What do astrocytes do?
Star-like. Take away toxins, release nutritious chemicals.
What are -vely charged ions called?
Anions
What are +vely charged ions called?
Cations
