Nervous System Flashcards
The nervous system is composed of two major divisions:
the central nervous system (CNS)
the peripheral nervous system
(PNS).
The CNS includes the ___ and ____
Brain, spinal cord
the PNS includes all the ___ that conduct impulses to and from the CNS.
nerves
The ___ division includes nerves and tracts leading toward the CNS— the sensory nerves and sensory tracts.
afferent
The ___ division includes nerves and tracts leading away from the CNS— the motor nerves and motor tracts.
efferent
The nervous system can be instead subdivided into the somatic nervous system (SNS) and the autonomic nervous system (ANS).
The ___ is concerned mainly with pathways that monitor ___ sensors (general senses) and regulate ___ effectors (skeletal muscles).
SNS
The ___ mainly monitors and regulates subconscious visceral activities that involve cardiac muscle, smooth muscle, glands, and adipose tissue.
ANS
The ___ is the cell type that conducts impulses, or action potentials.
neuron
(those electrical impulses that send signals around your body) are nothing more than a temporary shift (from negative to positive) in the neuron’s membrane potential caused by ions suddenly flowing in and out of the neuron
Action potential
The ___ support the neurons in any number of ways.
neuroglia (glial cells)
Types of neurons
Unipolar
Bipolar
Multipolar
having a single projection from the cell body
Unipolar
Having two projections from the cell body;
Bipolar
Having many projections
Multipolar
It is a large region made up of the nucleus and surrounding cytoplasm
cell body, or soma
Packets of rough endoplasmic reticulum (ER) in the soma produce ___.
These packets are still sometimes called _____ after their discoverer, Franz Nissl.
neurotransmitters
Nissl bodies or Nissi substance
The soma forms a cone-shaped projection, or ____, as it projects to become the ____.
axon hillock
axon
The ___ is one of two types of neuron projections (fibers).
axon
The axon usually conducts action potentials ___ from the cell body.
away
The axon may be wrapped with a series of neuroglial cells called _____
Schwann cells
___ wrap like tape around the axons of some peripheral nerves, each spiraling around a fiber to form a multilayered coating.
Schwann cells
The inner layers of the Schwann cell are filled with the fatty white substance called ___.
Myelin
Because the Schwann cells are found in series, they form a segmented sheath of
Schwann, or ____
myelin sheath.
Myelin sheath is composed of?
Schwann cells
Myelin
Nodes of ranvier
The gaps between the Schwann cells are termed ___ (myelin sheath gaps).
nodes of Ranvier
The outer wrapping of each ___ is normal cytoplasm, with organelles and a nucleus.
Schwann cell
In the case described, the ___ is called a white fiber, or myelinated fiber.
axon
A group of white fibers together is called ____.
white matter
Schwann cells occur only in the __.
PNS
Within the CNS, myelinated axons are wrapped with extensions of ___, another type of neuroglial cell.
oligodendrocytes
Schwann cells (neurolemmocytes) or oligodendrocytes are also associated with unmyelinated axons, which together with cell bodies and dendrites form ___.
However, in this case, the neuroglia do not form multiple wrappings and are not partially filled with myelin.
gray matter
Collateral axons, or axon branches, can be observed in some cells. In addition, the distal ends of axons are often branched.
These smaller distal branches are termed ___.
telodendria
Multipolar neurons have many projections from the soma called ___.
dendrites
are branched extensions that are sensitive to stimuli from other cells.
Dendrites
Other neurons form an association, or synapse, at a bump on the dendrite or cell body (soma). Stimulation of a dendrite or the cell body results in a local change in ___.
potential
Have multiple projections from the cell body
Multipolar
Comprise most of the neurons in CNS
Multipolar neurons
Almost all motor neurons are
Multipolar neurons
have exactly two projections from the cell body
Normally, one process conducts impulses toward the cell body. Such a process is called the dendrite. The other process conducts impulses away from the cell body and is called the axon.
Bipolar neurons
Are most commonly found in the sensory tracts of the eye (for vision) and nasal epithelium (for smell).
Bipolar neurons
also called pseudounipolar neurons, have one extension from the cell body; however, the single process splits near the body to become two long branches. One branch has dendrite-like endings that receive stimulation for an impulse. The remainder of that branch and all of the other branches then conduct the impulse along. The two branches together function as a single axon.
Unipolar neurons
Most sensory neurons are
unipolar
are the most numerous kinds of cells in nerve tissue.
Neuroglia, or simply glia
The conducting cells are called ___.
neurons
are often associated with particular neurons and support the structure or function of the neurons.
Glia
look like tiny stars in many preparations.
They have a cell body with many elongated projections.
Astrocytes
projections have broad “feet” that cover ___ in the brain. Together with the vessel wall it-self, the layer formed by the astrocyte feet forms the blood-brain barrier.
Substances that pass in and out of the blood vessel wall must also move across the wall formed by astrocyte projections.
Astrocyte
Blood vessels
are small glial cells that develop from different tissue than other nerve tissue cells. Because of their location, they are considered along with other glial cells. ____ are able to move to sites of damage or infection to phagocytize harmful substances.
Microglia
processes form a layer over axons in the CNS. This layer, called a myelin sheath, affects the speed of conduction in an axon.
Oligodendrocyte
form myelin sheaths around axons in the PNS. Each ___ wraps entirely around a single axon, rather than projecting extensions to several axons.
Schwann cells
are found lining the fluid spaces of the brain and spinal cord. Some form cerebrospinal fluid (CSF), and some are ciliated and assist the movement of CSF through the fluid spaces.
Ependymal cells
What are the different types of glial cells
(Amy makes omelets seem easy)
Astrocytes
Microglial
Oligodendrocytes
Schwann cells
Ependymal cells
The __ is a bundle of axons that lies in the PNS.
nerve
is a fibrous membrane that forms a sheath around the entire bundle of structures that make up the nerve.
Epineurium
is a fibrous structure that is essentially an inward continuation of the epineurium.
Perineurium
Acting as a sort of “inner wrapping” or “packing material,” the perineurium segregates the nerve fibers (axons) within the nerve into groupings called ____.
fascicles
Just as the perineurium is an inward extension of the epineurium, the ___ is an inward extension of the perineurium. The ___ is a fibrous membrane that covers each individual axon (and its sheath of Schwann cells) within each fascicle
Endoneurium
FUNCTIONS OF THE NERVOUS SYSTEM
- Sensory Input
- Integration
- Homeostasis
- Mental activity
- Control of muscles and glands
conducts action potentials from sensory
receptors to CNS by sensory neurons
Sensory Division / Afferent Division:
conducts action potentials from the CNS to effector organs, such as muscles & glands by motor neurons
Motor Division / Efferent Division
innervates skeletal muscle; mostly under voluntary control
o Somatic Nervous System
innervates cardiac muscle, smooth muscle, and glands; mostly under involuntary control
1. Sympathetic Division
2. Parasympathetic Division
o Autonomic Nervous System
unique subdivision of PNS that has both sensory and motor neurons contained wholly within the digestive tract.
Enteric Nervous System (ENS)
- Constrict pupils
- Increases saliva production
- Reduces heart rate
- Contricts bronchia
- Stimulates activity in digestive organs and pancreas, gall bladder
- constricts urinary bladder
- stimulates erection of genitals of man and women
Parasympathetic
a network of nerves that helps the body relax and perform life-sustaining functions
Parasympathetic system
- dilates pupils
- inhibits saliva production
- dilates bronchia
- rises the heart rate
- inhibits activity in the digestive organs, gall bladder, pancreas
- stimulates the adrenal medulla to release adrenaline and noradrenaline
- relaxes urinary bladder
- stimulates orgasm
Sympathetic system
a network of nerves that controls the body’s “fight-or-flight” response
Sympathetic system
aka “Nerve Cells” – receive stimuli, conduct action potentials, & transmit signals to other neuron or effector organs;
THE NEURON
Contains a nucleus and processes stimulus
Cell Body
Extensions of the neuron cell body; receive stimulus from other neurons or sensory receptors
Dendrites
Single long process; transmits stimulus to a gland, muscle, organ, or other neuron
Axon
supportive cells of CNS & PNS; do not conduct action potentials; carry
out different functions that enhance neuron function and maintain normal conditions.
Glial Cells / Neuroglia
