exam 2 Flashcards
What is the CNS?
made of the brain & spinal cord
What is the PNS?
everything outside of the brain & spinal cord
How long is the spinal cord?
about 18 inches in adults
How big is the diameter of the spinal cord?
about the size of a pinky finger
What shape is the spinal cord?
cylindrical but flat on its anterior & posterior surfaces
What is the foramen magnum?
a hole in the skull where the spinal cord begins
What does the spinal cord run continuous with?
the medulla oblongata
What is the spinal/vertebral canal?
a hole within the vertebra where the spinal cord is located
What is the spinal cord protected by?
bones (vertebrae), membranes called meninges, spaces & their contents, and dendiculate ligaments
What bones protect the spinal cord?
vertebrae
What are the meninges that protect the spinal cord?
pia mater, arachnoid mater, & dura mater
What is pia mater?
delicate, thin connective tissue that is anchored onto the cord; it’s the deepest layer
What is the arachnoid?
delicate web-like connective tissue
What is the dura mater?
tough fibrous connective tissue; it’s the most superficial layer
What do all the meninges surround?
the spinal cord & brain
What is the epidural space?
between the dura mater & the bones; cushions the cord
What does the epidural space contain?
adipose (fat) which is shown as a yellow color, connective tissue, fibers, lots of blood vessels
What is the subdural space?
deep to the dura mater; between the dura mater and the arachnoid; cushions cord
What does the subdural space contain?
serous fluid which is thin, clear, & watery with lots of ions & salts
What is the subarachnoid space?
deep to arachnoid; between the arachnoid & the pia mater
What does the subarachnoid space contain?
CSF (cerebrospinal fluid) which is a straw-colored fluid that contains water, ions, salts, some nutrients, & some cellular waste
What are dendiculate ligaments?
thin bands of connective tissue that extend laterally, anchoring the cord in its left & right sides
What is the cervical enlargement?
wide part in the spinal cord at the base of the neck; accommodates many nerves that innervates the neck, upper back, arms, & face
What is the thoracic region?
narrow part of the spinal cord through the chest area
What is the lumbar enlargement?
wide area of the spinal cord between the 9th & 12th thoracic vertebra; accommodates the nerves that innervate the legs
What is the conus medullaris?
part of the spinal cord past the lumbar enlargement that becomes narrower on one end
What is the filum terminale?
1 strand of pia mater extending from the tip of the conus medullaris; non-nervous; anchors cord inferiorly
What is the cauda equina?
group of nerves extending from the conus medullaris
What is the spinal cord made of?
an area of gray matter surrounded by white matter
What is the gray matter area of the spinal cord made of?
dendrites, cell bodies, & axons of association & motor neurons that are arranged in regions called horns
What is the anterior median fissure?
a deep split lined with pia mater
What is the posterior median sulcus?
a shallow depression
What is the gray commissure?
a narrow strip of gray matter that connects the right & left sides of the cord
What is the central canal?
small opening in the center of the gray commissure that holds CSF
What is the white matter area of the spinal cord made of?
tracts (bundles of axons in the CNS) that carry impulses up and down the cord & it is organised into columns
What are ascending tracts?
afferent; they carry sensory information into the CNS
What is the lateral spinothalamic tract?
ascending; carries information such as crude touch, pain, & temperature through the spinal cord to the thalamus
What is the spinocerebellar tract?
ascending; carries sensations of body position to the brain’s cerebellum
What is the spinotectal tract?
ascending; carries sensations from eyes that result in blinking & watering
What does the ascending tracts include?
lateral spinothalamic, spinocerebellar, & spinotectal
What are descending tracts?
efferent; carry motor impulses out of CNS to effectors (muscles & gland tissue)
What is the corticospinal tract?
descending; controls voluntary movement of small muscle groups such as those that move the fingers
What is the reticulospinal tract?
descending; controls the muscles of posture when the body is moving
What is the rubrospinal tract?
descending; controls the coordinated muscle action of body movement
What is the tectospinal tract?
descending; controls movement of the head in response to vision
What are roots?
bundles of nerve axons & dendrites attached to the lateral edges of the cord; named by their location; serve as attachments to the PNS
What are the anterior/ventral roots?
contain the axons of motor neurons
What are the posterior/dorsal roots?
contain the axons of sensory neurons
What is the dorsal root ganglion?
a swollen region lateral to the dorsal roots; it is a clump of sensory neuron cell bodies
What is a monosynaptic reflex?
1 sensory & 1 motor neuron; can be ipsilateral or contralateral; occurs within only 1 synapse
What is a polysynaptic reflex?
AT LEAST 1 sensory, 1 motor, & 1 association neuron; can be ipsilateral or contralateral; occurs within 2 or more synapses
What is the withdrawal reflex?
allows us to withdraw from pain by stimulating some muscles & inhibiting opposing muscles; polysynaptic; can be ipsilateral or contralateral
What is the crossed extensor reflex?
crosses cord from one side to the other; contralateral
What is the intersegmental reflex?
uses white matter tracts to send an impulse up & down cord; may involve the brain; can be ipsilateral or contralateral
What does ipsilateral mean?
stays only on 1 side of the cord
What does contralateral mean?
crosses from 1 side of the cord to the other
What would occur if the mixed spinal nerve area was severed?
sensory neurons could not come in & motor neurons could not go out
What would occur if the dorsal root ganglion area was severed?
sensory neurons could not come in
What would occur if the ventral root was severed?
motor neurons could not go out
What is a reflex?
a programmed predictable response to a stimulus; most of the time it only involves the spinal cord
How can reflexes be grouped?
the type of response & their processing site
What are the types of response in reflexes?
somatic & autonomic
What are the processing sites in reflexes?
spinal & cranial
What is a somatic reflex?
involuntary control of skeletal muscles (coughing, sneezing, blinking, etc.)
What is an autonomic reflex?
controls/adjusts ANS effectors which are smooth muscle, cardiac muscle, & gland tissue (sweat, chill bumps, digestion, etc.)
What are spinal reflexes?
occur in the spinal cord only
What are cranial reflexes?
involves the brain
What parts does each mixed spinal nerve branch into?
dorsal ramus, rami communicantes, & ventral ramus
What is the dorsal ramus?
innervates the skin & muscles of the back
What is the rami communicantes?
2 small branches that connect to the ANS
What is the ventral ramus?
large; innervates the rest of the body that the dorsal ramus & rami communicantes do not
What is a plexus?
a “tangle” formed from adjacent ventral rami
What are the different plexus groups?
cervical, brachial, lumbar, sacral, & coccygeal
What is the cervical plexus?
inferior to the base of the skull; innervates the neck, diaphragm muscle, & parts of the face and shoulders
What is the brachial plexus?
near cervical enlargement; innervates the arms, fingers, & shoudlers
What is the lumbar plexus?
near lumbar enlargement; innervates the hips & legs
What is the sacral plexus?
arises from the superior part of the conus medullaris; innervates the hips & legs
What is the coccygeal plexus?
arises from the inferior part of the conus medullaris; innervates the skin around the coccyx (tailbone)
How many pairs of mixed spinal nerves are there?
31; they each pass between vertebra & can be organized in a very specific manner
Mixed spinal nerves are organized into layers; what is the first layer?
each axon is wrapped in connective tissue called endoneurium
Mixed spinal nerves are organized into layers; what is the second layer?
groups/bundles of axons called fascicles are held together by connective tissue called perineurium
Mixed spinal nerves are organized into layers; what is the third layer?
many fascicles are held together in one large group by connective tissue called epineurium
How much does the brain weigh?
about 3.5 pounds
Why is the brain folded?
to allow ample surface area for neurons/neuroglia while still fitting in our skull
Does the brain require continuous oxygen?
yes; it gets 20% of the blood flow from each heartbeat
What is the brain protected by?
skull bones, meninges, CSF, astrocytes, acidic (low) pH, & other neuroglia such ependymal cells & microglia
How do the skull bones protect the brain?
they form a “brain case” called the cranium that has foramina that allow blood vessels & nerves to pass in/out
How is the dura mater in the brain different from the dura mater in the spinal cord?
it is divided into 2 layers
What is the meningeal layer?
soft, deeper part of the brain’s dura mater; contours around the brain’s folds (gyri & sulci)
What is the dural sinus?
space between the 2 layers of the brain’s dura mater; contains serous fluid and dural sinus blood vessels
What is the periosteal layer?
superficial part of brain’s dura mater; tough fibrous connective tissue that adheres to the inner surface of the skull
What is cerebrospinal fluid?
a straw-colored, sticky fluid made of water, ions, salts, white blood cells, proteins, amino acids, etc. in a specific composition with a specific pH
What structure continually secretes CSF?
the choroid plexus
What is the choroid plexus?
a combination of blood vessels & ependymal cells; produces more CSF than our body even needs
Where does CSF flow from after being produced by the choroid plexus?
the 2 C-shaped lateral ventricles in each half of the brain
What does CSF flow through after the lateral ventricles?
the interventricular foramen of Monro (2 small holes; 1 in each lateral ventricle)
What structure does CSF fill after the interventricular foramen of Monro?
the 3rd ventricle (in space of diencephalon)
What structure does CSF travel down after the 3rd ventricle?
the cerebral aqueduct of Sylvius (long passageway near brain stem)
Where does the CSF flow after the cerebral aqueduct of Sylvius?
the 4th ventricle which is a triangular cavity near the cerebellum
What structure does the CSF exit through after flowing through the 4th ventricle?
3 holes called aperatures: median aperature, & 2 lateral aperatures
What is the median aperature?
hole that connects to the central canal of the spinal cord for the flow of CSF
What are the 2 lateral aperatures?
holes that send CSF into posterior part of the subarachnoid space
After exiting through the aperatures, where does CSF travel?
down the posterior side of the cord & up the anterior side; flows around the brain in the subarachnoid space
What are arachnoid villi?
finger-like extensions that reabsorb CSF while in the subarachnoid space; they allow CSF to be picked up by dural sinus blood vessels
What are the functions of CSF?
distributes nutrients & absorbs cell waste from CNS, cushions brain & spinal cord, & keeps the brain suspended in the skull because CSF has the same density as the brain
How do astrocytes protect the brain?
they help form the blood-brain barrier which only allows small molecules to pass from brain blood vessels into brain tissue
Why is it important for the blood-brain barrier to allow small molecules in?
small molecules include oxygen, carbon dioxide, sodium ions, potassium ions, & glucose which are vital in our body
Why is it important for the blood-brain barrier to keep big molecules out?
it keeps big molecules such as proteins out which limits bacteria from entering the brain and spreading infection
What is the downside to the blood-brain barrier keeping big molecules out?
it also prohibits most beneficial drugs from entering the brain
What happens when oxygen levels are low?
carbon dioxide levels are high & CO2 combines with H2O which produces carbonic acid
Carbonic acid lowers pH; why does this help protect our brain?
it dilates specific blood vessels especially in the brain & it stimulates breathing centers in the brain so we breathe deeper & faster
How do ependymal cells help protect the brain?
they secrete & circulate cerebrospinal fluid (CSF)
How do microglia help protect the brain?
they engulf & destroy harmful materials in the CNS
What are the 3 main brain regions?
telencephalon, diencephalon, & brainstem
What are characteristics of the telencephalon (cerebrum)?
highly folded due to rapid growth; divided into 2 “layers”
What is the cortex?
outer region of the cerebrum made of neuron cell bodies, dendrites, & axons; gray matter
What are the brain’s white matter tracts?
found in the cerebrum; bundles of mostly myelinated axons that connect brain areas; include association, projection, & commissural tracts
What are association tracts?
connect within 1 hemisphere of the brain
What are projection tracts?
connect vertically, ultimately connecting the cerebrum & the spinal cord
What are commissural tracts?
connect left & right hemispheres (ex. = corpus callosum)
What can be found scattered in all 3 white matter tracts of the cerebrum?
clumps of neuron cell bodies called nuclei
What is the basal nucleus?
controls subconscious skeletal movement
What are sulci & gyri?
sulci = grooves, gyri = ridges
What does the frontal lobe control?
skeletal muscle movement, personality, & judgement
What is Broca’s area?
housed in the left frontal lobe; translates thought into speech
What does the parietal lobe do?
receives sensations from the body & allows us to identify an object by its shape & texture
What is the temporal lobe?
receives & processes auditory sensations; houses auditory memory & correlation
What is Wernicke’s area?
housed in the left temporal lobe; translates speech to thought
What is prosody?
housed in the right temporal lobe; adds emotional context to spoken words
What is the occipital lobe?
receives & processes visual sensations; houses visual memory & correlation
What is the insula?
it is hidden; deep to the temporal lobe; believed to be involved in short-term & emotional memory
What does the diencephalon include?
thalamus, hypothalamus, & pineal body/gland
What is the thalamus?
oval masses of gray matter (1 per hemisphere); routes impulses from brain stem to telencephalon
What is the hypothalamus?
makes & transports hormones; regulates hunger, thirst, rage, aggression, & body temperature
What is the pineal body/gland?
small cluster of neurons that release hormones which control cyclical behavior (sleep patterns)
What are the 3 regions of the brainstem?
mesencephalon, metencephalon, & myelencephalon
What is the mesencephalon?
midbrain; contains corpora quadrigemina; has nuclei that maintain muscle tone & consciousness
What are corpora quadrigemina?
4 round bumps through which auditory & visual reflexes are contained in the mesencephalon
What are the 2 parts of the metencephalon?
the pons & the cerebellum
What is the pons?
oval-shaped; connects brain areas & houses respiratory centers that control breathing (stimulated by acidic blood pH)
What is the cerebellum?
highly folded with many gyri & sulci; adjusts the muscles relative to body position & allows appropriate force from muscle contraction
What are Purkinje cells?
housed in cerebellum; highly branched neurons
What is the myelencephalon?
medulla oblongata; continuation of spinal cord’s ascending & descending tracts
What is decussation of tracts?
tracts that cross from one side to the other; there are many found in the myelencephalon
What brainstem region contains nuclei that control blood pressure, heart rate, contraction force, blood vessel diameter, breathing, & alertness?
myelencephalon
