Week 8 Flashcards
What are the two types of cells in the Nervous System?
- Neurons (Nerve cells)
- Glia (Glial Cells)
What is the major difference between glial cells and neurons?
Neurons are excitable cells, which means they are able to generate an transmit electrical signals.
Describe the glial cells
They do not conduct action potential but they support neurons. They can release neurotransmitters.
How do glial cells support neurons?
- Physically
- Metabolically
- Immunologically
What are the 4 body components of a neuron?
- Cell Body
- Dendrites
- Axon
- Axon terminals
Describe the function of cell body of the neurons:
It contain nucleus and most organelles
Describe the function of dendrites of the neurons:
They receive information from other neurons or cells
Describe the function of the axon in the neurons:
It conduct the action potential away from the cell body
What’s the main function of the axon hillock?
It’s where the action potential is generated
What are the main characteristics of the neuron?
It generate and transmit the action potential
What are the three different types of neural networks:
- Afferent Neurons
- Efferent Neurons
- Interneurons
Describe Afferent Neurons:
They carry information from sensory cells to the Central Nervous System
Describe Efferent Neurons:
They carry comands to physiological and behavioral effectors.
Describe Interneurons:
They integrate and store informations and communicate between the afferent and efferent neurons.
What is the membrane potential?
A difference in electrical charges between the inside and the outside of the membrane
Why is there a difference in electrical charge between the inside and the outside of the membrane?
Because there is:
- A difference in the distribution of ions across the membrane
- A difference in terms of permeability to those ions
What’s action potential?
A rapid change in the membrane potential
What are the three different types of changes of the membrane potential?
- Depolarization
- Repolarization
- Hyperpolarization
What’s Depolarization?
A decrease in the membrane potential, the membrane become less negative
What’s Repolarization?
The membrane potentiale return to its resting state after depolarization
What’s Hyperpolarization?
An increase in the membrane potential, which become even more negative
What’s the value of Em in human neurons?
-70 mV
What are the two main characteristics of Action Potential?
- It’s one-or none
- It’s self regenerating
Describe the speed of conduction of the action potential in invertebrates:
The speed of conduction in invertebrates is directly proportional to the diameter of the fibre
Describe the speed of conduction of the action potential in vertebrates?
In vertebrates neural axons are sheated in myelin resulting in saltatory conduction and speed up whitout an increase of the fibre diameter.
What are the two types of glial cells?
- Oligodendrocytes (CNS)
- Schwann Cells (PNS)
What are the nodes of Ranvier?
Regularly spaced gaps in the myelin coat of the acons that speeds up the conduction of the action potential.
What’s a synapse?
It’s the region where neurons communicate with each others or with other cells and the axon terminals are in close proximity with the target cell.
What are the two types of synapses?
- Chemical synapse
- Electrical synapse
Describe chemical synapse:
Chemical synapse release a neurotransmitter that results in change of the postsynaptic cell
Describe electrical synapse:
In electrical synapse the Action Potential spread directly from the presynaptic cell to the postynaptic cells via gap junctions.
Synapses can be of two differen kinds (based on the change they fire):
- Excitatory
- Inhibitory
Describe inhibitory synapses:
They cause the hyperpolarization of the posynaptic cell membrane
Describe spatial summation:
The summation of simultaneous influences of synapses at different sites on the postsynaptic cells.
Describe temporal summation:
The summation of postsynaptic membrane potential generated at the same site in a rapid sequence
What’s a nerve?
It’s a boundle of axons that come from many different neurons
What are ganglia?
High number of neurons organized into clusters
What are the two components of the central nervous system?
- The brain
- The spinal cord
What’s Peripheral Nervous System?
Is the totality of neurons that reside outside the brain or the spinal cord
Describe oligodendrocytes
They are the glial cells in the Central Nervous System and they wrap around the axons covering them with concentric layers of insulating plasma membrane.
Where can we found the Schwann cells?
In the peripheral nervous system
What are astrocytes?
They are glial cells that contribute to the blood-brain barrier protecting brain from toxic chemicals that ca be found in blood.
The inside of the cells is ____ compared to the outside
Negative
Describe sodium-potassium pumps:
They expels Na ions from inside the cell and bring K+ ions inside to keep their concentrations stable.
How is the Potassium Equilibrium reached?
When we reach the balance between the tendency of K+ to flow out the plasma membrane and the attraction that negative charges inside the membrane have on K+ that pulls it back.
What are the four different types of channels?
- Leak channels
- Voltage-Gated Channels
- Chemically-Gated Channels
- Mechanically-Gated Channels
Describe Voltage-Gated Channels
They open or close in response to a change in the voltage across the plasma membrane
Describe Chemically-Gated Channels
They opern or close depending on the presence or absence of a specific chemical molecule
Describe Mechanically-Gated Channels:
They open or close in response to a mechanical force applied to the plasma membrane.
What is a graded membrane potential?
Is a change from the resting potential that is then converted in the action potential at the axon hillock
Why is the action potential considered all-or-none?
Because the interaction between the voltage-gated Na+ channels and the membrane potential cause it to always the maximum level
Why is the action potential considered self-regenerating?
Because it spreads by local current flow to adjacent region of the plasma membrane resulting in continuos depolarization.
Why is the action potential spreading only in one direction?
Because the voltage-gated Na+ channels are in refractory period.
Why do action potential moves faster in myelinated axons?
Because it move through small jump in what is called saltatory conduction
Where are ion channels along the axon concentrated?
In the nodes of Ranvier
What is the main characteristic of myelin?
It reduces the leakage of ions so electric current can spread faster along the axon
What are neuromuscolar junction?
Synapses between neurons and skeletal muscle cell
What is acetylcoline?
Is the neurotransmitter used by all vertebrates
What’s synaptic cleft?
It’s the space between the presynaptic and the postsynaptic cell
What are the two types of receptor?
Ionotropic recepetors and Metabotropic receptors
Describe ionotropic receptors:
They are themselves ion channels and cause a direct change in the ion movement
Describe metabotropic receptors:
They are not ion channels but they induce signaling cascade in postsynaptic cell that change the ion distribution across the membrane. They affect the ion channels indirectly through G-proteins.
Describe the nervous systems of he flatworms:
You have chepalization and most neurons are organized into clusters called ganglia which are in pairs and connected by transverse nerves.
Describe the nervous systems of the earthworm:
Anterior ganglia are connected to a ventral nerve cord that expand in each segment to form ganglion.
What are sensory receptors cells?
Cells that convert physical and chemical stimuli into neural action potential.
What are the three types of ionotropic receptors?
- Mechanoreceptors
- Thermoreceptors
- Electroreceptors
Describe mechanoreceptors:
They respond to mechanical forces.
Describe Thermoreceptors:
They are influenced by temperature
Describe electroreceptors:
They’re opened by an electric charge
What are the two types of Metabotropic receptors?
- Chemoreceptors
- Photoreceptors
Describe Chemorecepetors:
a molecule binds to a recepetor initiating a signal that controls the ion channels
Describe photoreceptors:
Light alters a receptor protine initiating a signal cascade that controls the ion channels
What’s a receptor potential?
It’s a change in the membrane potential of a sensory receptor cell.
What are the two different ways by which a receptor may generate Action Potential?
It can do generate Action Potential directly in the receptor cell or trigger the release of neurotransmitters that indues a change in the postsynaptic cell Em.
Why we perceive sense in different ways?
Because the Action Potential arrive at different points of our Central Nervous System and it’s therefore processed in different ways.
How is the sensation intensity coded?
It’s coded depending on the frequency of Action Potentials.
What is adaptation?
Some sensory cells gradually diminish response to a mantained or repeated stimulus.
