(8) Nervous System Flashcards
● Consists of the brain, the spinal cord, and the peripheral nerves, which connect various parts of the body to either the brain or spinal cord
Nervous System
primary functional cell of the nervous system
Neuron
other cells types that functions to maintain the cellular environment to support the activity of the neurons
Glia
this system is the control center consisting of the brain and the spinal cord
Central Nervous System
this system has all the nerve processes connecting to the CNS, consisting of cranial and spinal nerves
Peripheral Nervous System
conducts sensory (afferent) information from the periphery to the CNS
Sensory (afferent) system
sensory fibers in the spinal cord that travel toward the brain
Ascending tracts
consists of motor (efferent) nerves that conduct from higher to lower levels of the CNS and from the CNS to the periphery
Motor (efferent) system
extend from the brain down the descending tracts in the cord to synapse on lower motor neurons (LMN)
Upper motor neurons (UMN)
What motor neuron extend away from the spinal cord and brain to the muscles and glands of the body
Lower motor neurons (LMN)
bundles of upper motor neuron fibers that move caudally in the spinal cord
Descending tracts
This system carries conscious voluntary information from the CNS to the skeletal muscles along cranial and spinal nerves
Somatic nervous system (soma, body)
This system carries involuntary information (sensory and motor) to and from smooth muscle, cardiac muscle, and glands of the body along cranial and spinal nerves to the spinal cord and brain
Autonomic nervous system (ANS)
● An artificial classification because many of the nerves of the body are partly in both divisions
Structural Classification
● Takes into account the impulses (sensory or motor) carried by nerves and the directions they travel
Impulse Classification
● Takes into account the activities that are directed by the nervous system
Functional Classification
from nerves of the somatic nervous system to skeletal muscles; and from skin and deeper somatic structures
Somatic fibers (motor and sensory)
supply skeletal (somatic) muscles, no matter what the branchial arch origin
Somatic motor (efferent) fibers
carry sensory information from skin and deeper somatic structures (skeletal muscle, skin, tendons, joint capsules, bones, etc)
Somatic sensory (afferent) fibers
from nerves of the ANS
ANS fibers
These fibers are carried by branches of all spinal and most cranial nerves
Sympathetic fibers
These fibers are restricted to some sacral spinal nerves (pelvic nerve) and only a few cranial nerves
Parasympathetic fibers
these fibers can be further divided into sympathetic and parasympathetic fibers
ANS motor (efferent) fibers
These fibers carry sensory fibers from blood vessels and viscera throughout the body
ANS sensory (afferent) fibers
These fibers carry special sensory information of taste, smell, vision, hearing and vestibular function to the brain
Special sensory fibers
■ Nerve cells or neurons
■ Neuroglial cells
■ These are bathed in what fluid?
extracellular fluid
the supporting structure of nervous tissue consisting of neuroglial cells
Neuroglia
○ different portions of the neuron have different membrane properties and to a degree different internal organelles, therefore, making them functional and structural compartments
○ This concept explains how disease can affect only specific compartments
○ These specialized compartments communicate with each other by transport systems
Compartmentalization
nerve cells are grouped biochemically by their neurotransmitters, allowing each set to carry out specific functions
Biochemical specialization
lack the ability to divide
Non reproducible
distinguishes nervous tissue from other tissues and is central to the functioning of nervous tissue
Complex connections
are the information cells of the body
Information
○ Synthesizes enzymes and other molecules essential to the normal function and the survival of the other compartments of the neuron
○ If the cell body is damaged, the rest of the cell dies
○ On the other hand, if an axon in the periphery is damaged, it has possibility of regenerating
○ Neurofibrils form a network extending into the nerve fibers, functioning in support and transport of materials between the compartments of the neuron
Cell body (soma or perikaryon)
○ Well-defined with a prominent nucleolus and granular chromatin
○ After 4 years of age, it appears to be unable to undergo mitosis, therefore unable to increase or replace neurons
Nucleus
Two types nerve processes that extends from the cell:
dendrites and axons
○ Two types extend from the cell: dendrites and axons.
○ A cell usually has only one axon, but may have many dendrites
Nerve processes
○ The multiple processes acting as the receptor portion of the neuron that conduct information (electrical impulses) toward the cell body
○ They are usually multi-branched processes containing cytoplasmic organelles and Nissl bodies
Dendrites
○ Carries information (electrical impulses) away from the cell body to other neurons or tissue
○ A long cylindrical process, usually singular, that may have tiny side branches (axon collaterals)
○ It has neurofibrils, but no Nissl bodies
○ Their terminal branches (telodendrites) end in synaptic knobs
Axons
○ Form the presynaptic side of the synapse and contain synaptic vesicles that store chemicals for release at the synapse
Synaptic knobs
○ These neurons brings information from receptors in the periphery to the CNS
○ These neurons have their cell bodies located outside the CNS
Sensory (afferent) neuron
○ These neuros carries information from the CNS to peripheral muscles, glands, or other neurons
○ Their neurons have their cell bodies inside the CNS (brain or spinal cord) and their axons (motor, efferent) extending to the periphery
Motor (efferent) neurons
○ Carry sensory impulses from sensory neurons to motor neurons
Interneuron
The whole interneuron (cell body, dendrites and axon) is located inside what system?
CNS
○ Receive many dendrites and has one axon
Multipolar
○ Receive one common trunk formed by its dendrites and sends out one axon
Bipolar
○ Receive one common trunk formed by the axon and dendrite
Unipolar or pseudounipolar
● The second cellular component of nervous tissue
● They are about 10-50 times more abundant than nerve cells
● Function as a binding agent to maintain the form of the nervous system
● Provide metabolic support for nerve cells and play a role in repair of damaged nervous tissue
● Unlike neurons, they are able to divide, therefore, are the primary source of intrinsic tumors
Neuroglia
Neuroglia of the CNS:
● Ependymal cells
● Astrocytes
● Oligodendrocyte
● Microglia
Neuroglia of the PNS:
● Schwann cells
○ Star-shaped cells that supply support to nervous tissue
○ The processes extend to form a membrane around the capillaries of the CNS
○ They bring nutrients from the capillaries to the neurons, thus, providing nutritional support
Astrocytes
○ Smaller and less branched than astrocytes, they wrap around the axons of nerve cells to form myelin
Oligodendrocyte
It increases the speed of conduction along the axon, resulting in faster information transfer
Myelin
○ The smallest neuroglial cells of the CNS
○ They migrate and act to phagocytize waste products in nerve tissue
Microglia
○ Neuroglia of the PNS
○ Form myelin sheaths by winding around nerve processes
○ Equivalent of the oligodendrocyte of the CNS
Schwann cells
○ Unmyelinated gaps between segments of the myelin sheath
Nodes of Ranvier
○ Lipoprotein forming a sheath around nerve processes
○ Axons and dendrites can have both myelin sheaths (myelinated) or remain naked (unmyelinated)
○ Increases the speed of impulse conduction and insulates the nerve process
Myelin
The remaining portion of the Schwann cell encircling the sheath is known as the ?, which assists in regeneration of injured axons
neurolemma
● A specialized site of apposition where information passes from one nerve cell to another cell
Synapse
the neuron that is transferring information to the postsynaptic cell
○ The first cell
○ Always a nerve
Presynaptic cell
the neuron, muscle or from the gland receiving information presynaptic cell
○ The second cell
○ Can be a nerve, muscle or gland
Postsynaptic cell
an electrical event that travels down an axon
Nerve action potential (NAP)
the terminal end of the presynaptic nerve that is in apposition synaptic cell
Synaptic button
membrane-bound organelles containing neurotransmitters located in the synaptic button
Synaptic vesicle
a chemical substance within the synaptic vesicle that mediates information transfer between nerve cells and other cells at synapses
Neurotransmitters
integral proteins inserted in the membrane of the postsynaptic cell
○ They bind with a neurotransmitter, resulting in a change in the membrane of the postsynaptic cell
Receptors
the synaptic connection between a neuron and muscular tissue where electrical impulses pass from the neuron to the muscle cell
○ This can result in contraction of the muscle
Neuromuscular junction
If the postsynaptic cell is a nerve, it can ? another nerve action potential in the postsynaptic nerve
initiate or inhibit
● The simplest impulse pathway
Reflex Arc
is an involuntary response to a sensory stimulus
reflex
This pathway involves sensory neuron, an interneuron, and a motor neuron
reflex arc (pathway of a reflex)
Specialized receptors at the end of sensory neurons receive a stimulus, resulting in an?
impulse
What travels through the dendrite, body, and axon of the sensory neuron into the spinal cord?
impulse
a change in the environment
Stimulus
the end of a sensory neuron’s dendrite that responds to change (stimulus) by developing a nerve impulse
Receptor
This neuron sends sensory impulses to the CNS
Sensory (afferent) neuron
located in the spinal cord, connect a sensory neuron with a motor neuron
Interneuron, association (internucial) neurons
This neuron carries an impulse to an effector organ
Motor (efferent) neuron
muscle or gland innervated by a motor neuron to react to the stimulus
Effector (target) organ
aggregations of nerve cell bodies (perikarya) located in the brain
Nucleus
a group of nerve cell bodies outside the CNS, manifested as a swelling of a nerve
Ganglion
This matter is part of the nervous tissue consisting mainly of neuronal cell bodies
Gray matter
This matter is part of the nervous tissue consisting mainly of myelinated nerve fibers
White matter
a bundle of nerve processes outside the CNS
Nerve
nerve fiber bundles of common origin in the brain and spinal cord
○ They are usually named for their origin and destination
Nerve tracts or Fasciculi
● The portion of the CNS contained within the skull
Brain
Brain can divided into three major parts:
the cerebrum, the cerebellum, and the brain stem
is the basis of the many medical terms relating to the brain
Encephalon (Gr. enkephalos, brain)
● Forms the bulk of and performs the higher functions of the brain
● Largest part of the brain, divided by the median fissure into two cerebral hemispheres
● Interprets sensory inputs from the sense organs, initiates voluntary skeletal muscle movements, and stores memory
Cerebrum (or Telencephalon)
Cerebrum (or Telencephalon)
● Forms the bulk of and performs the higher functions of the brain
● Largest part of the brain, divided by?
median fissure
What are the two structures created by the longitudinal fissure dividing the cerebrum
Cerebral hemispheres
Cerebral hemispheres are connected deeply by the?
corpus callosum
the thin, superficial layer of gray matter made up of nerve cell bodies
Cerebral cortex
the myelinated nerve axons connecting the cortex with other parts of the cortex, brain and spinal cord
White matter
axons connecting nerve cells in different parts of the same cerebral hemisphere
Association fibers
axons passing between nerve cells of both hemispheres and from the corpus callosum
Commissural fibers
axons connecting the cerebral cortex to other parts of the brain and the spinal cord
Projection fibers
masses of nerve cell bodies located deep in the white matter of the cerebrum
Basal ganglia
the numerous folds on the surface of the cerebral hemispheres greatly increasing its surface area
Convolutions or gyri
the depressions between the gyri, divided into two groups according to their dept
Grooves
deep grooves
Fissure
shallow grooves
Sulci
the deep groove separating the cerebrum into two cerebral hemispheres
Longitudinal fissure
the deep groove separating the cerebellum from the cerebral hemispheres
Transverse fissure
named for the bones overlying the cerebrum
Lobes and functional areas
mapped for sensory and motor areas
Cortex
What hemisphere controls skeletal muscle movements on the body’s left side, and vice versa
right
the rostral part of each cerebral hemisphere.
Frontal lobe
the caudal part of each cerebral hemisphere where the centers for vision are located
Occipital lobe
the lateral side of the cerebrum caudoventral to the lateral fissure
■ This is the location of the hearing centers
Temporal lobe
dorsal part of the cerebrum
Parietal lobe
the centers for smell (cerebrum)
Ventral cerebrum
the areas next to the sensory and motor areas
■ They analyze sensory input and are concerned with memory
Association areas
The rostral brainstem between the cerebrum and the midbrain, surrounding the third ventricle composed primarily of the ?, both gray matter grouped into nuclei
thalamus and the hypothalamus
the two oval masses , mainly gray matter, connected by the interthalamic adhesion
○ Functions as a central relay center for sensory impulses to the cerebral cortex, and contains some motor fibers from the cortex to other brain centers
Thalamus
Thalamus - the two oval masses , mainly gray matter, connected by the?
interthalamic adhesion
the floor of the diencephalon
○ Seen in a ventral view of the brain, located beneath the thalamus
○ Communicates with the cortex, thalamus and other parts of the brain, as well as with the pituitary gland via infundibular stalk
○ Regulates the viscera by controlling and integrating the ANS
○ Through the ANS, it controls heart rate, blood pressure, body temperature and GI secretions and motility
Hypothalamus
The two hormones hypothalamus produces that are sent to the posterior pituitary gland for storage and release
antidiuretic hormone (ADH) and oxytocin
○ The small gland of internal secretion attached to the hypothalamus by the infundibulum
Pituitary gland or hypophysis
Pituitary gland or hypophysis consists of two main parts:
■ Anterior lobe (adenohypophysis)
■ Posterior lobe (neurohypophysis)
○ Stalk attaching the pituitary gland to the hypothalamus
Infundibulum
● Located between the diencephalon and the pons, it connects lower brain centers and the spinal cord with higher brain centers
Midbrain and Mesencephalon
What part of the midbrain is composed of four colliculi (corpora quadrigemina)
roof (tectum)
functions as a motor reflex center in coordinating subconscious and conscious skeletal muscle movements
cerebellum
located in muscles, tendons, and joints, sense the relative position of one body part to another
Proprioceptors
the central part of the cerebellum
Vermis
the parts on either side of the vermis
Lateral masses
the thin, outer layer of gray matter
Cerebellar cortex
the white matter tracts branching into the cerebellum
Arbor vitae
bundles of fibers connecting the cerebellum to the brain stem
Cerebellar peduncles
The caudal cerebellar peduncles connect the?
medulla, spinal cord and the cerebellum
The middle cerebellar peduncles connect the?
cerebellum and the pons
The rostral cerebellar peduncles connect the?
midbrain and the cerebellum
This lobe is the area of temperature, pressure, touch and pain sensations
rostral lobe
