Biology Chapter 4: The Nervous System Flashcards
What are neurons?
Highly specialized cells responsible for conduction of impulses.
How do neurons communicate using electrical communication?
Via ion exchange and the generation of membrane potentials down the length of the axon.
How do neurons communicate using chemical communication?
Via neurotransmitter to the postsynaptic cell and the binding of these neurotransmitters to the postsynaptic cell
What are dendrites?
Appendages that receive signals from other cells
What is the soma?
location of the nucleus as well as organelles, including the ER and ribosomes
What is the axon hillock?
Where the cell body transitions to the axon and where action potentials are initiated
What is the axon?
It is a long appendage down which an action potential travels.
What is the nerve terminal or synaptic bouton?
End of the axon from which neurotransmitters are released.
What are nodes of ranvier?
exposed areas of myelinated axons that permit saltatory conduction.
What is the synapse?
nerve terminal of the presynaptic neuron, the membrane of the postsynaptic cell and the space between called the synaptic cleft
What is myelin?
It is an insulating substance that prevents signal loss. Prevents dissipation of the neural impulse and crossing of neural impulses from adjacent neurons.
What is myelin created by?
oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system
What are axons bundled into?
Nerves or tracts
What is the difference between nerves and tracts?
Nerve may carry multiple types of information - cell bodies of the same type cluster in ganglia in the PNS
Tracts contain only one type of information - cluster in nuclei in the CNS
What are neuroglia?
cells within the nervous system in addition to neurons
What are astrocytes?
nourish neurons and form the blood-brain barrier , which controls the transmission solutes from the bloodstream into the nervous tissue
What are ependymal cells?
line the ventricles of the brain and produce cerebrospinal fluid, which physically supports the brain and serves as a shock absorber.
What are microganglia?
phagocytic cells that ingest and break down waste products and pathogens in the CNS
What is the resting membrane potential of neurons?
-70 mV
What maintains the resting potential of neurons?
Maintained using selective permeability of ions as well as the Na+/K+ pump, which pumps three sodium ions out of the cell for every two potassium in
What are the two types of incoming signals?
Excitatory signals that cause depolarization of the neuron
Inhibitory signals that cause hyperpolarization of the neuron
What is temporal summation?
the addition of multiple signals near each other in time
What is spatial summation?
the addition of multiple signals near each other in space
What is an action potential?
It is used to propagate signals down the cell
What is the process of an action potential?
- Cell is depolarized when it reached a threshold voltage & sodium channels open
- Sodium flows into the cell
- At the peak, sodium channels are inactivated and potassium channels are opened
- K+ flows out to repolarize, overshoot resulting in a hyperpolarized neuron, then the K+ channels close
- The Na+/K+ pump beings the neuron back to resting potential and restores the gradient
What is the refractory period? absolute? relative?
refractory - when it is hyperpolarized
absolute - unable to fire another action potential
relative - needs a larger than normal stimulus to fire an action potential
What is the process of neurotransmitters activating?
- action potential arrives at the nerve terminal, voltage gated Ca2+ channels open
- Ca2+ causes vesicles with neurotransmitters with the presynaptic membrane, resulting in exocytosis into the synaptic cleft.
- N.T. bind to receptors on the postsynaptic cell, which may be ligand-gated ion channels or G protein-coupled receptors
What are 3 ways the neurotransmitters can be cleared out of the postsynaptic cleft?
enzymatically broken down.
absorbed back into the presynaptic cell
diffuse out of the cleft
What are the three types of neurons?
Motor (efferent)
Interneurons
Sensory (afferent)
In the CNS, what is white matter?
myelinated axons
In the CNS, what is grey matter?
unmyelinated cell bodies and dendrites.
What type of matter is deeper in the brain? spinal cord?
brain - white
spinal - grey
What is the PNS divided into?
somatic and autonomic
What is the autonomic split into?
parasympathetic (rest and digest)
sympathetic (fight or flight)
What are reflex arcs?
use the ability of the interneurons in the spinal cord to relay information to the source of stimuli while simultaneously routing it to the brain.
What is a monosynaptic reflex arc?
the sensory neuron fires directly into the motor neuron
What is a polysynaptic reflex arc?
sensory neuron may fire onto a motor neuron as well as interneurons that fire onto other motor neurons.
