Anatomy&Physiology Ch 12- Nervous Tissue
how the spinal cord connected to the brain?
through the foramen magnum of the occipital bone and encircled by the bones of the vertebral column
both the nervous and endocrine systems have the same objective, which is?
to keep controlled conditions within limits that maintain life
what are newly synthesized proteins produced by nissl bodies are used for?
to replace cellular components, as material for growth of neurons, and to regenerate damaged axons in the PNS.
what are the examples of sensory receptors?
touch receptors in the skin, photoreceptors in the eye, and olfactory (smell) receptors in the nose.
In most neurons, nerve impulses arise at the junction of the axon hillock and the initial segment, an area called the ________ _____, from which they travel along the axon to their destination.
trigger zone
is part of the PNS action voluntary or involuntary?
voluntary
twelve pairs of ________ _______ emerge from the brain and thirty-one pairs of ______ _____ emerge from the spinal cord
cranial nerves spinal nerves
the receiving or input portions of a neuron.
dendrites
The plasma membrane of dendrites, like the cell body, contains numerous receptor sites for binding chemical messengers from other neurons called
dendritic spines
the ability to respond to a stimulus and convert it into an action potential
electrical excitability
what does neurons posses?
electrical excitability
an extensive network of over 100 million neurons confined to the wall of the digestive canal.
enteric plexuses
are cuboidal to columnar cells arranged in a single layer that possess microvilli and cilia. -produce, possibly monitor, and assist in the circulation of cerebrospinal fluid.
ependymal cells
which is capable of moving materials a distance of 200-400 mm per day, uses proteins that function as "motors" to move materials along the surfaces of microtubules of the neuron's cytoskeleton.
fast axonal transport
how are substances that enter the neuron at the axon terminals are also moved by?
fast retrograde transport
have many long unbranched processes and are located mainly in white matter
fibrous astrocytes
A collection of neuron cell bodies outside the CNS is called a
ganglion
Brain tumors derived from glia
gliomas
function of the enteric plexuses
help regulate the activity of the smooth muscle and glands of the digestive canal
the part of the axon closest to the axon hillock is the
initial segment
The nervous system processes sensory information by analyzing it and making decisions for appropriate responses- an activity known as integration.
integrative function
neurons are mainly located within the CNS between sensory and motor neurons. integrate (process) incoming sensory information from sensory neurons and then elicit a motor response by activating the appropriate motor neurons.
interneurons
the action of ANS is
involuntary
a pigment that occurs as clumps of yellowish-brown granules in the cytoplasm
lipofuscin
These neuroglia are small cells with slender processes that give off numerous spinelike projections. -function as phagocytes
microglial cells
remove cellular debris formed during normal development of the nervous system and phagocytize microbes and damaged nervous tissue.
microglial cells
assist in moving materials between the cell body and axon
microtubules
Once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating effectors (muscles and glands) through cranial and spinal nerves. Stimulation of the effectors causes muscles to contract and glands to secrete.
motor function
convey nerve impulses away from the CNS to effectors (muscles and glands) in the periphery (PNS) through cranial or spinal nerves. -multipolar in structure
motor neurons or efferent neurons
conveys output from the CNS to effectors (muscles and glands)
motor or efferent division
most neurons have two kinds of processes:
multiple dendrites, single axon
usually have several dendrites and one axon. Most neurons in the brain and spinal cord are of this type , as well as all motor neurons.
multipolar neurons
a multilayered lipid and protein covering around some axons that insulates them and increases the speed of nerve impulse conduction. Such axons are said to be myelinated
myelin sheath
axons surrounded by a multilayered lipid and protein covering, called the myelin sheath, are said to be
myelinated
a bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord.
nerve
a general term for any neuronal process (extension) that emerges from the cell body of a neuron
nerve fiber
an electrical signal that propagates (travels) along the surface of the membrane of a neuron
nerve impulse
What begins and travels due to the movement of ions (such as sodium and potassium) between interstitial fluid and the inside of a neuron through specific ion channels in its plasma membrane?
nerve impulses
Components of the PNS include
nerves and sensory receptors
one of the smallest and most complex of the 11 body systems
nervous system
composed of bundles of intermediate filaments that provide the cell shape and support
neurofibrils
What does the cytoskeleton consist of?
neurofibrils and microtubules
make up about half the volume of the CNS.
neuroglia
neuroglia are smaller than neurons, and they are 5 to 25 times more numerous. In contrast to neurons, glia do not generate or propagate nerve impulses, and they can multiply and divide in the mature nervous system.
neuroglia
a physician who diagnoses and treats disorders of the nervous system
neurologist
deals with normal functioning and disorders of the nervous system
neurology
nervous tissue comprises two types of cells-
neurons and neuroglia
What do synaptic vesicles store?
neurotransmitters
Neuronal cell bodies also contain free ribosomes and prominent clusters of rough endoplasmic reticulum, termed
nissl bodies
what is the nervous system also responsible for?
our perceptions, behaviors, and memories, and it initiates all voluntary movements.
Takes care of "rest and digest" activities
parasympathetic division
consists of all nervous tissue outside the CNS
peripheral nervous system
Two types of astrocytes
protoplasmic and fibrous
have many short branching processes and are found in gray matte
protoplasmic astrocytes
function of central nervous system
relays messages, processes information, and analyzes information
moves membrane vesicles and other cellular materials from the axon terminals to the cell body to be degraded or recycled.
retrograde
These flat cells surround the cell bodies of neurons of PNS ganglia -providing structural support -regulate the exchanges of materials between neuronal cell bodies and interstitial fluid.
satellite cells
What is the PNS divided into?
sensory and motor divisions
Sensory receptors detect internal stimuli, such as an increase in blood pressure, or external stimuli. This sensory information is then carried into the brain and spinal cord through cranial and spinal nerves.
sensory function
either contain sensory receptors at their distal ends (dendrites) are located just after sensory receptors that are separate cells. Once an appropriate stimulus activates a sensory receptor, forms a nerve impulse in its axon and the nerve impulse is conveyed into the CNS through cranial or spinal nerves.
sensory neurons or afferent neurons
conveys input into the CNS from sensory receptors in the body
sensory or afferent division
refers to a structure of the nervous system that monitors changes in the external or internal environment
sensory receptor
detect a sensory stimulus such as touch, pressure, pain, or thermal stimuli.
sensory receptors
what do the dendrites of most pseudounipolar neurons function as?
sensory receptors
Three basic functions of the nervous system
sensory, integrative, motor
describe dendrites
short, tapering, and highly branched
propagates nerve impulses toward another neuron, a muscle fiber, or a gland cell
single axon of a neuron
The slower system, which moves materials about 1-5 mm per day, is called
slow axonal transport
conveys output from the CNS to skeletal muscles only.
somatic nervous system (SNS)
This division provides the CNS with sensory information about the
somatic senses (tactile, thermal, pain, and proprioceptive sensations) and special senses (smell, taste, vision, hearing, and equilibrium).
receptor sites that bind chemical messengers from other neurons
somatic spines
any change in the environment that is strong enough to initiate a nerve impulse
stimulus
help support exercise or emergency actions- the so-called "fight-or-flight" responses
sympathetic division
The site of communication between two neurons or between a neuron and an effector cell is called a
synapse
The tips of some axon terminals swell into bulb-shaped structures called
synaptic end bulbs
Both synaptic end bulbs and varicosities contain many tiny membrane-enclosed sacs called
synaptic vesicles
what is the two main subdivisions of the nervous system?
the central nervous system and the peripheral nervous system
Third branch of the Autonomic nervous system
the enteric plexuses
what electrically insulates the axon of a neuron and increases the speed of nerve impulse conduction?
the sheath
The autonomic nervous system is comprised of two main branches:
the sympathetic division and the parasympathetic division
functions of astrocytes
-contain microfilaments that give them considerable strength, which enables them to support neurons. -the endothelial cells create a blood-brain barrier, which restricts the movement of substances between the blood and interstitial fluid of the CNS. -secrete chemicals that appear to regulate the growth, migration, and interconnection among neurons in the brain. -help to maintain the appropriate chemical environment for the generation of nerve impulses. -also play a role in learning and memory by influencing the formation of neural synapses.
responsible for forming and maintaining the myelin sheath around CNS axons.
Oligodendrocytes
six types of neuroglia
Present in the CNS: - astrocytes - oligodendrocytes - microglia - ependymal cells Present in the PNS: - Schwann cells - satellite cells
have dendrites and one axon that are fused together to form a continuous process that emerges from the cell body
Pseudounipolar or unipolar neurons
form the myelin sheath around axons. participate in axon regeneration, which is more easily accomplished in the PNS than in the CNS.
Schwann cell
What is a neurotransmitter?
a molecule released from a synaptic vesicle that excites or inhibits another neuron, muscle fiber, or gland cell
What is the motor (efferent) division subdivided into?
a somatic nervous system and an autonomic nervous system
how are neurons functionally classified?
according to the direction in which the nerve impulse is conveyed with respect to the CNS.
How are neurons structurally classified?
according to the number of processes extending from the cell body
moves organelles and synaptic vesicles from the cell body to the axon terminals.
anterograde
these star-shaped cells have many processes and are the largest and most numerous of the neuroglia.
astrocytes
conveys output from the CNS to smooth muscle, cardiac muscle, and glands.
autonomic nervous system (ANS)
The cytoplasm of an axon, called axoplasm, is surrounded by a plasma membrane known as the
axolemma
An axon is a long, thin, cylindrical projection that often joins to the cell body at a cone-shaped elevation called the
axon hillock
The axon and its collaterals end by dividing into many fine processes called
axon terminals
The cytoplasm of an axon, called
axoplasm
how does the nervous system regulate body activities ?
by responding rapidly using nerve impulses
also known as the perikaryon or soma, contains a nucleus surrounded by cytoplasm that includes typical cellular organelles such as lysosomes, mitochondria, and a Golgi complex.
cell body
most neurons have three parts:
cell body, dendrites, axon
consists of the brain and spinal cord
central nervous system