A&P Lab 11: Nervous System: Histology Flashcards
Neurons
primary functional units of the nervous system; highly specialized to conduct action potentials along great distances at high speeds
Neuroglia
supporting cells of nervous tissue; protect, nourish, and promote the function of neurons
Central cell body
AKA soma; part of the neuron containing the nucleus and most of the cell’s organelles (doesn’t have centrioles; rough ER sometimes called Nissl bodies or chromatophilic substances)
Nissl bodies
AKA chromatophilic substances; stain differently than the typical rough ER
Neurofibrils
cell body contains these; help maintain the cell shape and integrity of the cell; receives action potentials from numerous dendrites
Dendrites
appear like branches of a tiny tree extending away from the cell body
Axon
usually longer than any of the dendrites; a single process in all neurons
Axon hillock
at the junction between the axon and the cell body is this cone-shaped region
Myelin sheath
in some neurons, the axon is wrapped with this external coating
Axon collaterals
the axon may include these side branches
Axon terminals
small processes located at the end of the axon and its axon collaterals; where neurotransmitters are released
Neurotransmitters
stimulators of adjacent neurons, muscle cells, or glands
Synaptic cleft
neurotransmitters diffuse across this small space
Sensory (afferent) neurons
a change in the environment, such as a change in temperature or pressure against the skin, is detected by receptors associated with the dendrites of these neurons, which carry the information of this change in the form of an action potential to the CNS
Interneuron (associated neuron)
within the CNS, an impulse is often passed to this neuron, which may carry the impulse to others like it for integration
Motor (efferent) neuron
neuron that carries an impulse away from the CNS
Effector
a muscle cell or gland that receives an impulse
Multipolar neurons
neurons with numerous processes, including a single axon and many dendrites; ex. motor neurons & interneurons
Bipolar neurons
a neuron with 2 processes, 1 axon & 1 dendrite on either side of the cell body; ex. organs of special sense ~ the retina of the eye & olfactory cells of the nose
Unipolar neuron
a neuron with just 1 process (axon); sensory neurons that form part of peripheral nerves
Astrocytes
located throughout the brain and spinal cord, these CNS neuroglia anchor neurons to capillaries, guide neurons during development, & control the chemical composition of cerebrospinal fluid
Oligodendrocyte
located throughout the brain and spinal cord, these CNS neuroglia form a protective and insulating covering around axons in the CNS, called a myelin sheath
Microglia
mobile cells in the brain and spinal cord that phatocytize invading microorganisms and dead nervous tissue
Ependymal cell
lines the ventricles in the brain and the central canal in the spinal cord; forms cerebrospinal fluid and generates a current by their ciliary action
Schwann cell
wraps around certain axons of neurons in the PNS; forms the myelin sheath, which increases nerve impulse speed; aids in the regeneration of axons
Satellite cell
surrounds neuron cell bodies in PNS ganglia; helps nourish neurons and regulates the chemical environment
Neurolemma
most of the cytoplasm and the cell’s nucleus are pushed to the outermost layer of the myelin sheath, forming this small bulge
White matter
an area of nervous tissue that is dominated with myelinated axons that is white in color
Gray matter
when the area of nervous tissue is dominated with axons lacking the myelin sheath; appears slightly gray in color
Node of Ranvier
in peripheral neurons, the Schwann cells form the myelin sheath in segments, one cell per segment; between each segment is this gap, in which the axon is exposed to the extracellular space
Myelinated fibers
axons that are covered with the myelin sheath; fastest conductors in the body
Unmyelinated fibers
axons that are not covered with the myelin sheath; Schwann cells or oligodendrocytes present, but form a thin, single-layer covering over the axon
Central Nervous System (CNS)
brain & spinal cord; receives info from sensory receptors, coordinates & integrates the info, and initiates & transmits a response
Peripheral Nervous System (PNS)
nerves/ganglia, which channel impulses to and from the CNS; includes sensory nerves, which carry impulses from sensory receptors to the CNS and motor nerves, which transmit impulses from the CNS to effector organs such as neurons, muscles, and glands
Cerebrum
largest part of the brain; integrative center of the brain, receiving and interpreting sensory info, drawing upon memory and learning, and initiating motor responses; conscious thought also resides within the layers of neurons; prominent; fills the superior, anterior, and posterior parts of the cranial cavity
Convolutions
cerebrum contains numerous of these wrinkle-like foldings
Gyri
upfoldings of the convolutions of the cerebrum
Sulci
shallow downfoldings of the convolutions of the cerebrum
Cerebral hemispheres
a deep downfold separates the cerebrum into 2 parts, the right & left ___ _____
Longitudinal fissure
the separation of the cerebrum into right and left hemispheres
Transverse fissure
deep downfolding separating the cerebrum from the cerebellum
Cerebral lobes
superficial areas of the cerebrum corresponding to the bones of the cranium (frontal, parietal, temporal, occipital)
Central sulcus
downfold that divides the frontal lobe from the parietal lobe
Precentral gyrus
upfold anterior to the central sulcus
Postcentral gyrus
upfold posterior to the central sulcus
Lateral sulcus
downfold that divides the parietal lobe from the temporal lobe
Parieto-occipital sulcus
shallow groove (downfold) that divides the parietal and occipital lobes
Cerebral cortex
outermost fringe of the cerebrum; roughly 2-3mm thick, consists of several layers of neuron cell bodies that integrate sensory info, participate in intellectual activities/emotions, and generate motor responses; entirely composed of gray matter (neuron cell bodies, dendrites, and unmyelinated fibers)
White matter types of fiber tracts
association fibers, commissural fibers, projection fibers
Association fibers
fibers which extend to areas within the same hemisphere
Commisural fibers
fibers which extend between the 2 hemispheres; includes a prominent tract that connects the 2 hemispheres (corpus callosum)
Projection fibers
fibers that ascend or descend through the brain
Corpus callosum
prominent tract that connects the 2 hemispheres
Basal ganglia
clusters of gray matter embedded within the white matter of each hemisphere; control semiconscious muscle movements and participate in the limbic system (emotional functions of the brain)
Folia
upfolds of the cerebellum, closely fitted to resemble the pages of a book
Cerebellar hemispheres
right and left portions of the cerebellum
Vermis
central area separating the cerebellar hemispheres
Cerebellar cortex
outer layer of gray matter of the cerebellum
Arbor vitae
inner area of white matter of the cerebellum that is organized into narrow branches that resemble that of a tree
Cerebellar peduncles
cerebellum is attached to the rest of the brain by the inferior, middle, and inferior ___ ____
Diencephalon
located within the center of the brain, inferior to the cerebrum; contains the thalamus, hypothalamus, and epithalamus
Thalamus
largest part of the diencephalon, forming 80% of its total mass
Intermediate mass
thalamus includes 2 egg-shaped structures connected by this small bridge of tissue
Hypothalamus
located inferior to the thalamus; small, roughly triangular region containing important nuclei, which are centers for control for necessary body functions, including temperature regulation, hunger, thirst, emotions/behavior, many hormonal activities, and the autonomic functions (heart rate, blood pressure regulation)
Mammillary bodies
2 of the nuclei of the hypothalamus appear as small swellings on the ventral side of the brain
Pituitary gland
pea-shaped gland connected to the hypothalamus
Infundibulum
narrows stalk that connects the pituitary to the hypothalamus
Optic chiasma
anterior to the infundibulum is this landmark structure on the ventral side of the brain; where optic nerves from each eyeball meet and cross before continuing to the occipital lobe of the cerebrum
Epithalamus
located superior to the thalamus; small area dominated by the pineal gland
Pineal gland
endocrine gland that dominates the epithalamus
Brain stem
inferior stem-like part of the brain, which connects the higher parts of the brain with the spinal cord; consists of the midbrain, pons, and the medulla oblongata
Midbrain
superior part of the brain stem; located inferior to the diencephalon; contains the cerebral peduncles
Cerebral peduncles
bundle of myelinated fibers that connect the upper and lower brain regions
Corpora quadrigemina
composed of 2 superior colliculi and 2 inferior colliculi
Superior colliculi
clusters of gray matter that regulate reflexes in eye, head, and trunk movements associated with vision
Inferior colliculi
house reflexes associated with auditory stimuli
Pons
expanded portion of the brain stem inferior to the midbrain and anterior to the cerebellum; contains reflex centers that assist the medulla in regulating respiration; also relays info to other parts of the brain by way of connections to the diencephalon and cerebellum
Medulla oblongata
inferiormost part of the brain, connecting the spinal cord as it exits the cranial cavity through the foramen magnum; contains the respiratory and cardiovascular control centers; also contains reflex centers involved in coughing, sneezing, and vomiting
Cranial meninges
membranes of the brain, deep to the cranial bones
Dura mater
outermost meningeal layer; “hard mother”
Periosteal layer
tough, outer layer of the dura mater, attached to the cranium
Meningeal layer
inner, thin layer of the dura mater
Dural sinuses
periosteal and meningeal layers of the dura mater split to form these spaces that collect blood before it drains into the jugular veins for recirculation
Superior sagittal sinus
larges dural sinus; lies on top of the longitudinal fissure
Falx cerebri
1 of 2 major extensions of the dura mater; dip down into the longitudinal fissure
Tentorium cerebelli
1 of 2 major extensions of the dura mater; extends into the transverse fissure
Arachnoid
deep to the dura mater is this 2nd meningeal layer, which resembles a spider; consists of numerous protein fibers forming a matrix that resembles a spider’s web
Subarachnoid space
between the arachnoid fibers is this space filled with cerebrospinal fluid
Pia mater
final meningeal layer; thin, vascular; adheres to the outer surface of the cerebral cortex
Cerebrospinal fluid (CSF)
in addition to the bones of the cranium and the meninges, the brain receives protection from physical injury by the presence of this liquid, which provides a cushion that absorbs jarring movements of the head; also supports neurons of the brain and spinal cord with a continuous flow of oxygen, nutrients, and other important chemicals; initially formed from blood plasma leadking out of capillary networks
Choroid plexus
capillary networks form this “pleated membrane”, which is located within 4 cavities within the brain commonly called the brain ventricles
Lateral ventricles
2 large brain ventricles, 2 in each cerebral hemisphere
Septum pellucidum
lateral ventricles are separated by this thin partition
Third ventricle
smaller ventricle located between the 2 masses of the thalamus
4th ventricle
very small ventricle located between the cerebellum and pons
Interventricular foramen
channel segment between the lateral ventricles and the 3rd ventricle
Cerebral aqueduct
segment between the 3rd & 4th ventricle
Arachnoid villi
CSF is recycled back into the bloodstream by reabsorption through these small, fingerlike projections located in the superior sagittal sinus
Spinal nerves
31 pairs of nerves extending from the lateral sides of the spinal cord, passing through the intervertebral foramina, and continuing to the body area they innervate
Spinal cord gray matter
looks like a butterfly or the shape of the letter H in the center of the cord
Anterior gray horns
part of the gray matter of the spinal cord that contain somatic motor neuron cell bodies
Posterior gray horns
part of the gray matter of the spinal cord that contain terminal endings of peripheral sensory neurons and their synapses with association neurons
Lateral gray horns
part of the gray matter of the spinal cord that contain visceral motor neuron cell bodies
Gray commissure
gray matter of the spinal cord contains this part, which connects the right and left sides of the gray matter
Central canal
surrounded by the gray commissure; channels CSF
Spinal cord white matter
surrounds the gray matter of the spinal cord
Anterior median fissure
deep groove of the white matter of the spinal cord
Posterior median sulcus
narrow groove of the white matter of the spinal cord
White columns (white funiculi)
anterior, lateral, and posterior; regions of white matter of the spinal cord
Posterior (dorsal) root & anterior (ventral) root
external to the spinal cord, the spinal nerves divide into these roots; dorsal contains sensory fibers; ventral contains motor fibers
Posterior (dorsal) root ganglion
near the division of the spinal nerves into posterior & anterior roots, the posterior root bulges to form this, which is the location of the cell bodies of sensory neurons
Plexus
in 4 regions of the body, numerous spinal nerves formed a branched network; cervical, brachial, lumbar, and sacral on each side of the vertebral column
Cervical plexus
formed from the anterior rami of spinal nerves C1-5, innervates muscles of the shoulder and neck
Phrenic nerve
from the cervical plexus, this nerve arises from spinal nerves C3-5 to pass into the thoracic cavity to innervate the diaphragm for the control of breathing
Brachial plexus
larger and more complex than the cervical plexus; formed from the anterior rami of C5-T1
Axillary nerve
from the brachial plexus, this nerve arises to innervate the muscles and skin of the shoulder
Radial nerve
large nerve that arises to extend down the posterolateral side of the arm and forearm, supplying all of the muscles and skin along its route
Median nerve
extends parallel to the radial nerve; passes down the anterolateral side of the arm
Lumbar plexus
located in the lumbar region; arises from the anterior rami of L1-4 (& T12 in some individuals); its nerves supply the lower abdominopelvic region and the anterior thigh
Femoral nerve
large nerve that arises from the lumbar plexus to innervate the anterior thigh muscles; includes smaller branches that supply the skin and muscles of the anteromedial side of the lower limb
Sacral plexus
arises from L4-S4; its nerves supply the rear pelvis, posterior side of the thigh, and all sensory and motor functions of the leg and foot
Sciatic nerve
the largest nerve of the body; arises from the sacral plexus; extends through its notch to continue down the posterior side of the thigh, supplying flexor muscles and skin along its path
Common fibular (peroneal) nerve
sciatic nerve divides into this and the tibial nerve in the popliteal region; along with the tibial nerve, supplies the remaining muscles and skin of the leg
Tibial nerve
sciatic nerve divides into this and the common fibular (peroneal) nerve in the popliteal region; along with the common fibular nerve, supplies the remaining muscles and skin of the leg
Olfactory nerve
carries sensory impulses from the olfactory center to the thalamus; most anterior nerve; = CN I
Olfactory bulbs
swellings at the base of the frontal lobes where the neurons of the cranial nerves form a synapse with 2nd order neurons
Reflex arc
simplest form of a reflex; involves a simple pathway with 5 components (sensory receptor & neuron, integration center, motor neuron, and effector)
Sensory receptor
triggers an action potential if the change in environment, or stimulus, is great enough to generate it
Sensory neuron
action potential is conducted by this to the CNS, which terminates at a synapse in the spinal cord (in a spinal reflex) or in the brain stem (in a cranial reflex)
Integration center
action potential is passed to 1 or more neurons in the spinal cord or brain stem by way of synapses to form this center
Motor neuron
from the integration center, the action potential passes to this, which conducts it to an effector
Effector
the action potential stimulates the effector to perform work, which may be a skeletal muscle (in a somatic reflex), or a cardiac muscle, smooth muscle, or gland (in a visceral reflex)
Patellar reflex
when the patellar tendon is stretched, the response is a rapid extension of the leg at the knee
Biceps reflex
rapid contraction of the biceps brachii in response to a sudden stretch of the biceps tendon
Achilles reflex
examines the 1st 2 sacral segments of the spinal cord; results in plantar flexion when the calcaneus tendon is stretched
Plantar reflex
common clinical test that examines the pyramidal tract of the brain, in addition to the peripheral nerves that are associated with the reflex arc; in adults, causes the toes to flex and move closer together
White communicating rami
preganglionic neurons exit the spinal cord in the anterior (ventral) root of the spinal nerves along with somatic motor neurons, then exit from the spinal nerve to form these myelinated parts
Sympathetic trunk ganglia
white communicating rami connect with this series of swellings extending alongside the vertebral column in the T1 through L2 region
Splanchnic nerves
without the trunk ganglia, the axons may synapse with postganglionic neurons or they may alternatively pass through the sympathetic trunk ganglia without synapsing to emerge to form these nerves near abdominopelvic organs
Gray communicating rami
postganglionic cell bodies are located within the sympathetic trunk ganglia & synapse with the preganglionic neurons; their axons may return to the spinal nerve by way of these unmyelinated parts
Terminal (intramural) ganglia
axons of the cranial preganglionic neurons emerge from the brain stem within cranial nerves III, VII, IX, and X; from there, they extend to their target organs in the head region, where they terminate at synapses within postganglionic neurons in ___ ___
Pelvic sphlanchnic nerves
axons of the sacral preganglionic neurons exit the spinal cord in the anterior (ventral) roots of S2-S4 via nerves known as ___ ___ ___
