nervous tissue Flashcards
a bundle of axons (plus associated connective tissue and blood vessels) located outside the brain and spinal cord is called_
a nerve
small masses of nervous tissue, consisting primarily of neuron cell bodies, that are located outside the brain and spinal cord are called_
ganglia
what are the three major functions of the nervous system
- sensory input: the nervous system uses its millions of sensory receptors to monitor changes occuring both inside and outside the body. The gathered information is called sensory input
- integration: the nervous system processes and interprets sensory input and decides what should be done at each moment - a process called integration
- motor output: the nervous system activates effector organs-the muscles and glands-to cause a response, called motor output
networks of neurons located in the walls of GI tract organs and help regulate digestive system activities is called_
enteric plexuses
structures that monitor changes in the internal and external environment are called_
sensory receptors
what are the two parts the nervous system is divided into
the CNS (central nervous system): consists of the brain and spinal cord
the PNS (peripheral nervous system): consists of nerves that extend from the brain to the spinal cord
spinal nerves carry impulses to and from the _
spinal cord
cranial nerves carry impulses to and from the _
brain
what are the two functional subdivisions of the PNS
- sensory, or afferent division: consists of nnerve fibers that convey impulses to the central nervous system from sensory receptors located throughout the body
- motor, or efferent division: transmits impulses from the CNS to effector organs, which are the muscles and glands (they effect, or bring about a motor response)
what do somatic sensory fibers do?
convey impulses from the skin, skeletal muscles, and joints
what to visceral sensory fibers do?
transmit impulses from the visceral organs (within the ventral body cavity)
what are the two main parts of the motor (efferent) division
- somatic nervous system: composed of somatic motor nerve fibers that conduct impulses form CNS to skeletal muscles. VOLUNTARY NERVOUS SYSTEM (b.c. it allows us to consciously control our skeletal muscles)
- automonic nervous system (ANS): consists of visceral motor nerve fibers that regulate the activity of smooth muscles, cardiac muscles, and glands. INVOLUNTARY NERVOUS SYSTEM (b.c. it regulates activities such as the pumping of our heart, or the movement of food through our digestive tracts.)
what are the two functional subdivisions of the ANS
- sympathetic division: generally supports exercise and emergency actions, ie: “fight-or-flight” responses
- parasympathetic division: generally promotes “rest and digest” activites
what is the enteric nervous system?
involuntary, ENS, “brain of the gut;” consists of neurons in the enteric plexuses that extend the entire length of the GI tract. The sensory neurons monitor changes in the GI tract and the motor neurons help regulate digestive system activites
what two types of cells make up the nervous system
- neurons: nerve cells that are excitable (respond to stimuli), and transmit electrical signals
- neuroglia: support, nourish, and protect the neurons and maintain the interstitial fluid that bathes neurons
when neurons respond to a stimulus and convert it into a nerve impulse, this is called a_
action potential
what are the three major parts of a neuron
- a cell body: contains the nucleus surrounded by cytoplasm that includes typical organelles
- dendrites: usually short, tapering, unmyelinated, and highly branched processes that emerge from the cell body
- axon: a long, thin, cylindrical process that may be myelinated and transmits nerve impulses away from the cell body
what is the name of the structure that joins the cell body to the axon
axon hillock
the axon and its collaterals end at where?
at the end of many fine processes called axon termina lbranches (arborizations)
nerve impulses are generated at the junction of the axon hillock and axon, which is called_
the trigger zone
most axons are surrounded by a _____ sheath. The purpse of myelin is _
to protect and electrically insulate fibers, and increase the transmission speed of nerve impulses
myelinated axons have gaps in the myelin sheath called _
nodes of ranvier
what is the name of the cells that produce the myelin sheaths around the PNS axons
schwann cells
what is the name of the cells that surround the cell bodies of neurons in the PNS ganglia, provide structural support, and regulate the exchange of materials between neuron cell bodies and the interstitial fluid?
satellite cells
regions of the brain and spinal cord containing dense collections of myelinated fibers are referred to as _____ _____
white matter
regions of the brain and spinal cord that contain mostly nerve cell bodies and nonmyelinated fibers is _____ _____
gray matter
in the spinal cord, _____ matter surrounds a butterfly-shaped core of _____ matter.
white, gray
in the brain, a thin layer of _____ matter covers the cerebrum and cerebellum. Masses of this _____ matter called _____.
gray, gray, nuclei
most nerves and all tracts (bundles of axons in the CNS) are composed of _____ matter
white
the junction between two neurons is called a _
synapse
at a synapse between neurons, the neuron sending the signal is called the _____ neuron, and the neuron receiving the message is called the _____ neuron.
presynaptic, postsynaptic
the synapse between a motor neuron and a muscle fiber is called a _
neuromuscular junction
the synpase between a neuron and a glandular cell is called a _
neuroglandular junction
in which kind of synapse do nerve impulses pass directly from the presynaptic neuron to the postsynaptic cell
in an electrical synapse
in a chemical synapse, the small gap between cells at a synapse is called the _
synaptic cleft
neurons are classified functionally or structurally. When classified structurally, what does this mean and what are the 3 subcategories?
the structural classification is based on the number of processes that extend from the cell body:
- multipolar neurons: usually have several dendrites and one axon; most neurons in the brain and spinal cord are of this type
- bipolar neurons: have one main dendrite and one axon; these are located in the retina, inner ear, and olfactory area of the brain
- unipolar or pseudounipolar neurons: sensory neurons have just one process extending from the cell body; this process branches to form a peripheral process (which is essentially an axon with dendritic branches at its distal end) and a central process (which has synaptic end bulbs at its distal end)
where can we find purkinje cells
in the cerebrum
where can we find pyramidal cells
in the cerebral cortex
what are the four types of neuroglia in the CNS?
- astrocytes: star-shaped cells (with many processes) that perform several functions in support of neurons. They are the most numerous of the neuroglia. There are two types: protoplasmic (in gray matter) & fibrous (located in white matter)
- oligodendrocytes: have few processes and produce a myelin sheath; each oligodendrocyte can myelinate parts of several axons
- microglia: small, phagocytic neuroglia that protect the nervous system by engulfing microbes and removing debris of dead cells
- ependymal cells: line the brain ventricles and the central canal of the spinal cord; they secrete and aid in the circulation of cerebrospinal fluid and they form the blood-cerebrospinal fluid barrier
brain tumors derived from glia are called_
gliomas
