Nervous Tissues Flashcards
Duchenne type
Becker type
Sensory
Integrates sensory information by analyzing and storing some of it and by making decisions for appropriate responses
Integrative
Once sensory information is integrated, the nervous system may elicit an appropriate motor response by activating effectors through cranial and spinal
nerves.
Motor
Parts of Central Nervous System
- Brain
- Spinal Cord
Parts of Peripheral Nervous System
- Cranial nerves (12 Pairs)
- Spinal nerves (31 Pairs)
- Autonomic Nervous System
* Sympathetic Nervous System
* Parasympathetic Nervous System
consists of nerves that
convey impulses to the CNS
Sensory (Afferent)
carries impulses from the
CNS to effector organs, muscles and glands.
Motor (Efferent)
allows voluntary movement of
skeletal muscles
Somatic
regulates events that are automatic
or involuntary (Sympathetic and
Parasympathetic)
Autonomic
- Active conducting elements
- Basic unit of the nervous system which conducts electrical impulses from one part of the body to
another
Neurons
- The supporting elements
- includes many types of cells that generally support, insulate, and protect the delicate neurons.
Neuroglia
- Group of short, unsheathed processes
arranged like branches of a tree that transmit
impulses toward the cell body
Dendrites
- Single, elongated sheathed process
conducting impulses away from the cell body
Axons
- perikaryon or soma, contains a nucleus
surrounded by cytoplasm that includes typical
cellular organelles such as lysosomes,
mitochondria, and a golgi complex.
Cell Body
usually have several dendrites and one axon.
Multipolar neurons
They are found in the retina of the eye, in the inner ear, and in the olfactory area of the brain.
Bipolar neurons
have a single process emerging from the cell body
Unipolar neurons
do not have axons; only dendrites. Only communicate
using graded portneials
Anaxonic neurons
- Contain sensory receptors at their distal ends / located just after sensory receptors that are separate cells.
- Conduct action potentials toward the CNS
Sensory of afferent neurons
- Convey action potentials away from the CNS to effectors in the periphery through
cranial or spinal nerves.
Motor or efferent neurons
- Are mainly located within the CNS between sensory and motor neurons.
- Conduct action potentials within the CNS from one neuron to another.
Interneurons or association neurons
- Insulating material covering axons in central
and peripheral nervous system - The electric impulse “jumps” from node to
node in myelin sheath instead of traveling
continuously along the nerve fiber. - Nodes of Ranvier
Myelin Sheath
- The process of forming a myelin sheath
around a nerve to allow .nerve impulses
move more quickly.
Myelination
- lacking a myelin sheath, unmyelinated
axons.
Unmyelination
- Points of connection between neurons
- Axon on one neuron make functional
contact with dendrites of another
neuron
Synapse
Main Neurotransmitters
- Epinephrine
- Norepinephrine
- Acetylcholine
- ** all are released by autonomic fibers
- abundant star-shaped cells that account for nearly half of the neural tissue.
- form a living barrier between capillaries and neurons and play a role in making exchanges between
the two.
Astrocytes
- spider like phagocytes that dispose of debris , include
deed brain cells and bacteria.
Microglia
- these glial cells line the central cavities of the brain and the spinal cord.
Ependymal Cells
- glia that wrap their flat extensions tightly around the nerve fibers , producing fatty insulating coverings called myelin sheaths.
Oligodendrocytes
- form the myelin sheaths around nerve fibers that are
found in the PNS.
Schwann cell
- act as protective , cushioning cells.
Satellite cells
is a localized reversal in the charge of cell membrane and spreads there like an electric current
Nerve Impulse
This sudden electric change in membrane is called
ACTION POTENTIAL
A resting (non-signaling) neuron has a voltage across its membrane called
Resting Membrane Potential
- The external surface of the membrane is slightly
positive and its internal face is slightly negative
Resting Membrane Electrical Conditions
A stimulus changes the permeability of a patch of
the membrane and sodium ions diffuse rapidly into
the cell
Stimulus initiates local depolarization
- If stimulus is strong enough, depolarization causes
membrane polarity to be completely reversed and
an action potential is initiated
Depolarization and generation of action
potential
- Depolarization of the first membrane patch
causes permeability changes in the adjacent
membrane and are repeated.
Propagation of action potential
Potassium diffuses out of the cell as the
membrane permeability changes again,
restoring the negative charge on the inside of
the membrane and the positive charge on the
outside surface
Repolarization
- Ionic conditions of the resting state are
restored later by the activity of sodium potassium pump.
Initial ionic conditions restored
- special mode of action potential propagation that occurs along myelinated axons,
occurs because of the uneven distribution of voltage - gate channels.
Saltatory conduction
- type of action potential propagation which involves step-by-step depolarization and
repolarization of each adjacent segment of the plasma membrane - occurs in
unmyelinated axons and in muscle fibers.
Continuous conduction
- Rapid, predictable and involuntary responses to stimuli
- Occurs over neural pathways called reflex arcs and involve both CNS and PNS
structures
Reflexes
reflexes that stimulate skeletal muscles
Somatic
regulate the activity of smooth muscles, heart and glands
Autonomic
5 Elements of Reflex Arcs
- Sensory receptor
- Effector organ
- Sensory neurons
- Motor neurons
- Integration center
called as such
because of its darker appearance and
preponderance of nerve cell bodies
Gray Matter
composed chiefly of myelinated nerve fibers
* In the spinal cord, an H-shaped central region of gray matter is surrounded by white matter
White Matter
- In a surface layer (cortex) of the cerebrum and
cerebellum. - Nucleus: designates a mass of gray matter in any
part of the brain or spinal cord - Ganglion: means cluster of nerve cell bodies and
dendrites, but usually refers to those cells located
outside the brain and spinal cord
Gray Matter
- Part of the nervous system contained within the skull
- Most complex and largest mass of nervous tissue in the body and contains billions of nerve cells
- The control center for registering sensations, correlating with stored information, making decisions and taking actions.
BRAIN
Embryological Divisions of the Brain
- Forebrain (Prosencephalon)
* Telencephalon: Cerebrum with Basal ganglia
* Diencephalon: Thalamus, Hypothalamus - Midbrain (Mesencephalon)
- Hindbrain (Rhombencephalon)
- Surface layer of gray matter (cerebral cortex)
greatly expanded by convolutions, or gyri. - Internal to which is the white substance made up
of nerve fibers - “Seat of Intelligence”
Telencephalon (Cerebrum)
- Memory stage, recall , learning and reasoning for
comprehension and execution of language - Perception of all sensations and sites where one
modality of sensation can be integrated with others - Initiation of movements
Telencephalon (Cerebrum)
- Runs from the posterior to the anterior
aspects almost completely dividing it into 2
hemispheres - The hemispheres are connected in the midline by the corpus callosum
Longitudinal Fissure
- Between the temporal from the parietal lobe
Lateral Sylvian Fissure
- Between frontal and parietal lobes
Central Sulcus (Rolandic Fissure)
- Between the parietal and occipital lobes
Parieto – Occipital Fissure
- Found in the occipital lobe perpendicular to parieto-occipital fissure around which is the visual center
Calcarine Fissure
- Includes all the cortex lying anterior to the central sulcus and above the lateral sulcus of Sylvius
- Center for motor functions and personality
Frontal Lobe
- Lies posterior to central sulcus and above
the lateral Sylvian fissure - Center for ordinary sensory functions
Parietal Lobe
- Lies beneath the lateral sulcus of Sylvius
- Center for hearing and olfaction
Temporal Lobe
- Occupies the posterior extremity of the
cerebral hemisphere behind parieto-occipital
fissure - Visual Center
Occipital Lobe
- Exposed when the lips of lateral Sylvian
fissures are separated
Insula (Island of Reil)
- Lies in the frontal lobe immediately anterior to the central sulcus
- Controls voluntary movements in the opposite side of the body
Primary Motor Area (Pre-central gyrus)
Primary Motor Area (Pre-central gyrus)
Pre-frontal Area
- Lies in the inferior frontal gyrus of dominant hemisphere
Motor speech area (Broca’s area)
- Lies behind the central sulcus in parietal lobe
- Ordinary sensations of pain, temperature,
pressure and touch, position and movement
sensation from opposite side of the body
Primary Sensory/Somesthetic Area/Post-central
gyrus
- Lies in temporal lobes posterior to the auditory
area of dominant hemisphere
Sensory Speech Area (Wernicke’s area)
- Lies below lateral sulcus within the temporal lobe
- Center for hearing
. Auditory or Hearing Area (Transverse gyri of Heschl)
- Cortex around the calcarine fissure
- Found in occipital lobe
Visual Area
- Within the temporal lobe
Olfactory or Smell Area
- Above lateral sulcus into the deep layers of the
sensory area
Taste Area
- Four paired masses of gray matter embedded in the white matter of the cerebral
hemispheres
Telencephalon (Basal Ganglia)
Include caudate nucleus (medial portion) and the putamen and globus pallidus
(lateral portion) collectively called
lentiform nucleus
- Located in the forebrain along with the cerebrum
Diencephalon
- Paired mass of gray matter situated below corpus
callosum - Highest subcortical sensory integrating center
- All sensory impulses (ordinary and special), passes the thalamus before going to cerebral cortex, except for
smell
Thalamus
- Involved in the regulation of body temperature, feeding activities, concentration and volume of extracellular fluid, autonomic nervous system responses and endocrine functions
- Where pituitary gland is attached to
Hypothalamus
- Located in the forebrain along with the
cerebrum
Diencephalon
- A small region superior and posterior to the
thalamus, consists of the pineal gland and
habenular nuclei
Epithalamus
- Connects the forebrain and hindbrain
Mesencephalon
- The constricted central portion is called vermis and the lateral expanded portion the hemispheres.
- Greatly aids the motor cortex of the cerebral hemispheres in the integration of voluntary movements
Cerebellum
- Lies anterior to the cerebellum and between the midbrain and medulla
- Bridge-like structure, consisting almost entirely of white matter linking the various parts of the brain
Pons
- Continuous with the spinal cord anteriorly and with the pons superiorly
- Lies ventral to the cerebellum
- Has a number of vital regulatory and reflex centers, including those controlling the circulatory system, breathing, swallowing, vomiting, coughing and sneezing.
Medulla Oblongata
- Spaces inside the brain filled with Cerebrospinal Fluid
Ventricles of the Brain
- found inside the cerebral hemispheres
- Communicates with the third ventricle by way of interventricular foramen (foramen of Monroe)
Lateral Ventricle
** Small, slit-like cavity in the center of the diencephalon in between the 2 thalami.
* Continuous with the cerebral aqueduct of Sylvius, a canal which passes through the midbrain
Third ventricle
- Lies between the cerebellum on the posteriorly side and the pons and medulla on the anterior side
- Communicates with the subarachnoid space through the Foramen of Luschka and Magendie
Fourth Ventricle
Provide protection to the brain and spinal cord
Meninges
Dura Mater
Pachymeninx
Arachnoid Mater
Pia Mater
Leptomeninges
- The outer meninx, is made of dense,
fibrous tissues.
Dura Mater
2 portions: Cranial and Spinal
- Epidural space:
- Subdural space:
- Delicate serous membrane located between the dura and pia mater.
- The subarachnoid space between the arachnoid ater and the pia mater is occupied by thin, delicate connective tissues trabeculae and intercommunicating channels in which CSF is contained
Arachnoid Mater
- A vascular membrane consisting of a plexus of fine blood vessels held together by areolar connective tissue
- The cranial portion invests the surface of the brain and dips down into the sulci
Pia Mater
- A colorless fluid circulating within the vesicles, the central canal of the spinal cord and also within the subarachnoid space
- Serves as a water cushion to guard the brain and spinal cord against injury
- Formed in ventricles by active secretion, principally from the capillaries of the choroid plexus
Cerebrospinal Fluid
CSF Pathway
CSF from choroid plexuses in lateral ventricles - intraventricular
foramen of Monroe- third ventricle- aqueduct of Sylvius-
fourth ventricle- foramen of Luschka and Magendie-
subarachnoid space- arachnoid villi- absorbed in
the venous circulation
- Elongated and almost cylindrical part of the
CNS - Continuous with the medulla oblongata above and extends from the level of foramen magnum to the lower border of first lumbar vertebra in adult and level of L3 vertebra in children
- A mass nerve tissue located in the vertebral canal from which 31 pairs of spinal nerves originate.
SPINAL CORD
- Where nerve supply of upper extremities arises
from
Cervical enlargement
- Where nerve supply of lower extremities arises
from
Lumbar enlargement
where it gives rise to the thread-like filum terminate
which terminates in the first coccygeal vertebra
conus medullaris
- Lumbar and sacral spinal nerves descend along
the filum terminate in a bundle known as the
cauda equina
- Composed of the least permeable capillaries in the whole body.
- Only water, glucose and essential amino acids pass easily through the walls of these capillaries
- Non-essential amino acids and potassium ions not only are prevented from entering the brain but also are actively pumped from the brain into the blood
Blood-Brain Barrier
