Unit 9 - Neural Tissue Flashcards
What does the central nervous system do?
Integrates information
What does the peripheral nervous system do?
Transmits sensory and motor signals between the central nervous system and the rest of the body
What are 3 general functions of the nervous system?
Sensory, integrative, motor
What does a sensory function of the nervous system mean?
It detects stimuli and transmits information to the nervous system
What does an integrative function of the nervous system mean?
Receives signals from many neurons and carries out integrative function
What does a motor function of the nervous system mean?
Sends signals out to muscles and gland cells
What are neurons?
Highly specialized nerve cells that generate and conduct nerve impulses
What are neuroglial cells?
Supporting cells that provide physical sport, remove debris, and provide electrical insulation
Describe the primary components of a neuron.
The soma
The axon
Dendrites
Synapses
What is the soma?
The cell body of a neuron
What is the axon?
A long slender projection that conducts electrical impulses away from the cell body
What are dendrites?
Tree-like structures that receive messages from other neurons
What are synapses?
Specialized junctions between neurons
What are myelin?
A mixture of proteins and phospholipids forming a whitish insulating sheath around many nerve fibers, increasing the speed at which impulses are conducted
What is the advantage of an axon being myelinated?
An axon covered with myelin (myelinated) increases the speed of action potentials
What is the most common neuron?
Multipolar neuron
Function of sensory (afferent) neurons
Detect stimuli
Transmit to the CNS
Conducts signals towards CNS
Function of interneurons (association)
Receive signals from many neurons and carry out integrative function
90% of all neurons are…?
Interneurons
Function of motor (efferent) neurons
Sends signals out to muscles and gland cells
Name the 6 types of neuroglial cells
Oligodendrocytes Ependymal cells Microglia Astrocytes Schwann cells Satellite cells
Describe how an injured nerve fiber may regenerate.
After peripheral nerve injury, axons readily regenerate. The distal portion of the axon, which is disconnected from the cell body, undergoes Wallerian degeneration. This active process results in fragmentation and disintegration of the axon. Debris is removed by glial cells, predominantly macrophages.
Explain how a membrane may become polarized.
A cell becomes polarized by moving and storing different types of electrically-charged molecules on different sides of its membrane
Define resting potential.
Charge difference across the plasma membrane
What is depolarization?
Membrane voltage shifts to a less negative value
What is repolarization?
The change in membrane potential that returns it to a negative value just after the depolarization phase of an action potential which has changed the membrane potential to a positive value
What is hyperpolarization?
When the membrane potential becomes more negative at a particular spot on the neuron’s membrane
List the changes that occur during an action potential.
Resting membrane potential, local potential, threshold, depolarization, spike, repolarization, hyperpolarization
Explain the difference between action potentials and nerve impulses.
A nerve impulse is a sudden reversal of the electrical gradient across the plasma membrane of a resting neuron. The reversal of charge is called an action potential.
Define refractory period.
Period of resistance to stimulation
Define saltatory conduction.
The propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials
Define synapse.
Nerve signal reaches the end of axon which triggers the release of a neurotransmitter
Explain how a nerve impulse is transmitted from one neuron to another.
Nerve impulses begin in a dendrite (there can be many dendrites), then move to the cell body, then down to the axon tip. There is only one axon, but it can have many tips. When a nerve impulse is transferred is called a synapse.
Explain the role of calcium in the release of neurotransmitters.
Nerve impulse causes Calcium ions to enter presynaptic neurone. Entry of calcium ions causes fusion of vesicles with presynaptic membrane and the neurotransmitter is released by exocytosis.
Define neuropeptide
Chemical messengers made up of small chains of amino acids that are synthesized and released by neurons. Neuropeptides typically bind to G protein-coupled receptors to modulate neural activity and other tissues like the gut, muscles, and heart.
What do excitatory postsynaptic potentials (EPSP) do?
Bring the neuron’s potential closer to its firing threshold
What do inhibitory postsynaptic potentials (IPSP) do?
Change the charge across the membrane to be further from the firing threshold
Describe the “trigger zone” of a neuron.
Where action potential is generated
Define facilitation.
A process in which one neuron enhances the effect of another one
What does divergence allow?
One neuron to communicate with many other neurons in a network
What does convergence allow?
A neuron to receive input from many neurons in a network
Explain how nerve impulses are amplified.
Converging nerve fibers amplify nerve impulses. In convergence, two or more incoming fibers contact a single neuron, whereas in divergence, impulses leaving a neuron pass into several output fibers. Several nerve fibers converging onto one nerve fiber amplifies nerve impulses.
