Intro/Neurons/Neuroglial Cells Flashcards
Central Nervous System
Brain and spinal cord
lie in midline of body
Nuclei
collection of cell bodies in CNS
tracts
collection of nerve axons in CNS
peripheral nervous system
cranial nerves and spinal nerves
includes all nerves not in the brain or spinal cord
brainstem
midbrain, pons, and medulla
Cranial nerves
project from the brainstem
generally innervate the face, head, and neck
spinal nerves
project from either side of the spinal cord
innervate the rest of the body, including the trunk and extremities
ganglia
cell bodies inside the peripheral nervous system
part of a single nerve
nerves
collection of nerve axons in the peripheral nervous system
a sensory (or afferent division) and motor (or efferent division)
peripheral nervous system receives impulses from the sensory organs via the afferent division, and then relays signals or impulses from the central nervous system to muscles and glands via the motor or efferent division
somatic nervous system -efferent
generally under conscious (voluntary) control
IE: movements of skeletal muscles, skin, and joints
autonomic nervous system (ANS)- efferent
control the glands and smooth muscles of the internal organs
not under conscious control
sympathetic nervous system- autonomic
activates and prepares the body for vigorous muscular activity, stress, and emergencies
parasympathetic nervous system
generally operates during normal situations, permits digestion, and conserves energy
Neurons
nerve cells that conduct electrical impulses and relay information throughout the body
Parts of Neuron
dendrites, cell body, and axon
Neuron facts
do not undergo mitosis (cell division)
can survive a person’s entire lifetime, which is why brain and spinal cord damage is so serious
Any neurons that die due to brain damage cannot be replaced.
can survive just minutes without oxygen.
neuron cell body
synthesizes all nerve cell products
consists of a large nucleus with surrounding cytoplasm containing the normal organelles
Information is received and sent in the same direction within a neuron
dendrites
receiving end of a neuron
numerous short extensions that emanate from the cell body, which receive information from other neurons and conduct those nerve impulses toward the cell body
axon
conducts nerve impulses away from the cell body to its axon terminals
axon facts
can vary in length, being very short or very long, up to three feet
composed of cell components like the cell body but lack rough endoplasmic reticulum
depends upon the neuron’s cell body to send the necessary proteins down the length of the axon
Cell body facts (neuron)
contains the nucleus and other organelles typically found in cells, except for centrioles, which are not capable of mitosis.
One of the main functions of the cell body is to manufacture neurotransmitters
Neurotransmitters
chemicals stored inside secretory vesicles (axon terminal vesicles) at the end of the axon terminals
When neurotransmitters are released by the axon terminal vesicles, they carry the transmission of the nerve impulse from one neuron to another
synapse
gap between two neurons, as neurons do not physically touch one another
presynaptic/postsynaptic
means before the synapse/after the synapse
Multipolar neurons
three or more extensions from the cell body
neurons have one axon and many dendrites
Can be called motor neurons
Bipolar neurons
central cell body with two extensions
found within the body as special receptor cells in the visual and olfactory systems
Unipolar neurons (pseudounipolar)
have one extension off the cell body that branches into two: one central process running to the CNS and another peripheral process running to the sensory receptor
sensory neurons in the peripheral nervous system
Sensory neurons (afferent)-neuron type
unipolar and function to carry information from the peripheral to the central nervous system
Interneurons- def and neuron type
association neurons, are found only in the central nervous system
typically multipolar neurons and transmit impulses within different parts of the central nervous system
Motor neurons (efferent)- neuron type
multipolar neurons, which send messages from the central nervous system to the peripheral
nerve
consists of hundreds of thousands of axons wrapped together in a connective tissue
Neuroglial cells
support cells for neurons
Neurons require highly specific environment to survive and conduct electrical impulses efficiently. Neuroglial cells help to support neurons to enable them to thrive in their needed environment.
Schwann cells
short sections peripheral nerve axon is coated in
type of neuroglial cell found in the peripheral nervous system (PNS) and composed of a white fatty layer called the myelin sheath
also unmyelinated fibers, which are common in the gray matter of the brain and spinal cord, in which the Schwann cells do not wrap around the axon but are just loosely associated with the axon
myelin sheath
rolled around the axon, insulating the nerve fiber from others and increasing the speed of nerve impulses
Nodes of Ranvier
gaps between Schwann cells
saltatory conduction
nerve impulse is forced to jump to the next node
greatly increases the nerve impulse transmission along the axon
Satellite cells
surround the cell bodies of peripheral neurons, helping to regulate the cell body environment
Axonal Regeneration
process where peripheral nerve axon is severed in an injury, the Schwann cells grow ahead of the axon, creating a path for the axon to follow as it grows. It is possible in many cases for axons to regrow after an injury to a peripheral nerve; although, the growth is very slow
Ependymal cells (CNS)
circulate cerebrospinal fluid and allow fluid exchange between brain, spinal cord, and cerebrospinal fluid (CSF
cerebrospinal fluid (CSF)
clear fluid that only circulates in the brain and spinal cord
Oligodendrocytes
act as the insulation for central nervous system axons
Astrocytes
control the chemical environment of neurons by wrapping around the blood capillaries
blood brain barrier
allowing the passage of only certain substances into the central nervous system
Microglial cells
protect the CNS by scavenging dead cells and infectious microorganisms
