Central Nervous System Exam 3

Cerebrum

large region of brain responsible for conscious perception and high cognitive functions (ex. language)

forms 5 lobes in each hemisphere: frontal, parietal, occipital, temporal, and insular

Fissure

Longitudinal Fissure

deep groove on the surface of the brain

right and left hemispheres divided by deep groove 

Cerebral cortex

surface of brain organized into 6 layers containing the most superficial layers of gray matter

motor planning regions, sensory regions, association regulation

Gyri

elevated ridges on the surface of the brain separated by sulci (shallow grooves)

central sulcus

Separates the precentral gyrus of the frontal lobe from the postcentral gyrus of the parietal lobe

Tracts

white matter in the CNS

consists of bundles of myelinated axons and oligodendrocytes that produce ths myelin

Corpus callosum

largest white matter structure in the brain connects the left and right cerebral hemispheres

Basal nuclei

deep clusters of gray matter in the cerebrum

Frontal lobe

Primary motor cortex

most anterior, function is important for planning motor commands 

in the precentral gyrus is the location of upper motor neurons that send motor commands out of the brain 

Parietal Lobe

primary somatosensory cortex

most superior region posterior to the central sulcus, functions important for somatosensory processing

in the postcentral gyrus, first part of cerebrum that processes sensory info for the general senses

Occipital lobe

most posterior region

function is important for visual processing

contains primary visual cortex

Temporal lobe

contains:

large lateral region inferior to the lateral sulcus, function is important for auditory and olfactory processing, memory, and emotions.

HippocampusL medial region, imp for memory formation

amygdala: deep nucleus, imp for producing emotions

Insula

region of cerebral cortex located deep between temporal and frontal lobes, functions important for gustatory processing and emotions 

Diencephalon

brain region deep to the cerebrum and superior to the brain stem with 3 regions

Thalamus

largest region of diencephalon

relaying sensory pathways to cerebral cortex

Hypothalamus

controls autonomic nervous system and endocrine systems

feedings, fornication, fight or flight

emotional responses

hunger

water balance/thirst

controls body temp

Mammillary bodies

small round projections from the inferior surface of the diencephalon anterior to the brain stem

structures connect to the medial temporal lobe through the fornix

damage causes impaired memory

Pineal gland

Located along the midline in the posterior diencephalon

secretes melatonin at night and is regulated by visual input from the hypothalamus to regulate circadian rhythm (day-night cycles)

Cerebellum 

region posterior to the brain stem that has function important for posture, balance, learning and executing skilled movements.

Folia

folds of the cerebellar cortex (superficial gray matter) seperated by sulci

Arbor vitae

branching white matter structure deep to the cerebellar cortex

Brainstem

inferior region of the brain that has numerous nuclei of gray matter

functions as vital reflex control centers and tracts of white matter carrying information to and from the spinal cord 

divided into 3 regions

Midbrain

superior portion of brain stem directly inferior to diencephalon

Superior colliculi: visual reflexes

Inferior colliculi: auditory reflexes

Substantia nigra

contains neurons that produce dopamine to regulate the motivation and motor planning circuits

Pons

bulging middle region of brain stem between the midbrain and the medulla 

connects to the cerebellum on posterior with tracts

Medulla oblangata

base of the brain stem, contains vital reflex centers that regulate the cardiovascular, digestive, and respiratory centers

Structure of spinal cord

from the foramen magnum to L1/L2 through the vertebral foramen

Cervical enlargement

expanded superior end of spinal cord is larger because there are numerous nerves going to/from the upper limbs

Lumbar enlargement

expanded inferior end is larger because there are numerous nerves supplying the lower extremities

Conus medullaris 

cone shaped tapered end of the spinal cord located at the level of the L1/L2 vertebrae.

Cauda equina

“horse tail”

Lower lumbar & sacral spinal nerves travel inferior past the conus through vertebral foramen before exiting the spinal column

Dorsal (Posterior) root

axons of afferent (first-order sensory) neurons entering spinal cord

Ventral (anterior) root 

axons exiting the spinal cord from motor neurons in the lateral and anterior grey horns of the spinal cord.

Gray matter

neuron cell bodies, dendrites, axon terminals

Dorsal (Posterior) Gray horns

contains axon terminals of afferent neurons and the soma/dendrites of interneurons that relay sensory information

Ventral (anterior) gray horns

contains somatic motor neuron cell bodies

Lateral gray horns

contains preganglionic autonomic motor neurons

White matter

located superficial to gray matter of spinal cord

tracts

bundles of axons in the CNS

white columns (funiculi)

structures containing multiple tracts within the spinal cord

Dorsal (Posterior) White columns

contains major ascending tracts carrying the tactile (discriminative, fine touch) and proprioceptive somatosensory information.

Located medial to the posterior (dorsal) gray horns

Anterior and lateral white columns 

contains the major descending tracts that regulate the motor neurons of the ventral gray horn. Also contains ascending tracts carrying the sense of pain, temperature, and nondiscriminative (course, crude touch) somatosensory information

Meninges

3 connective tissue membranes surrounding the brain and spinal cord

Dura mater

superficial layer of fibrous CT

2 layers are fused except for areas where they are separated to close dural sinuses

Dural septa: inner extension that limit/secure movement of brain

superior sagittal sinus: large dural sinus at the superior end of longitudinal fissure

Arachnoid mater

loose middle layer

subarachnoid space: controls cerebrospinal fluid and blood vessels

arachnoid granulations: projections of middle meningeal later that extends through dura mater into the dural sinuses

Pia mater

deepest, clings tightly to the brain following every sulcus

Separates the extracellular fluid of the brain from the cerebrospinal fluid but allows movement of solutes such as nutrients and waste

Epidural space

region of the vertebral cavity superficial to the spinal meninges containing adipose tissue that cushions the spinal cord

Ventricles of the brain

cavities within the brain lined with ependymal cells filled with cerebrospinalfluid 

third ventricle

cerebral aqueduct

fourth ventricle

formed by the medial walls of the thalamus

connects third and fourth ventricle, runs through the midbrain

inferior to third and continuous with the central canal of spinal cord

Cerebrospinal fluid

fluid found in and around brain and spinal cord

cushions brain and spinal cord, transports nutrients and waste

Choroid plexus

cluster of capillaries covered with ependymal cells found within the ventricles

responsible for the formation of CSF

Blood Brain Barrier

functional separation of the blood from the extracellular fluid of the brain and CSF

produced by the astrocytes and the endothelial cells of capillaries in the brain

Tight junctions

cell junctions that form between the endothelial cells of capillaries in the brain to prevent movement of fluid and solutes between the blood and the extracellular fluid of the brain. Astrocytes release chemical messages to stimulate endothelial cells to produce these cell junctions

Ascending tracts

Descending tracts

axons carrying sensory information of the brain

axons carrying motor commands from the brain to low motor neurons

Motor cortex

regions of the frontal lobe that contains upper motor neurons that send signals to the lower motor neurons

Corticospinal tracts

descending axons of the upper motor neurons carrying motor commands to the spinal cord

Spastic paralysis 

upper motor neurons are damaged, but lower motor neurons stay intact

no voluntary control of muscles, but intact spinal reflexes are exaggerated

Flaccid paralysis

damage to the ventral root or ventral horn prevents efferent fibers from sending action potentials to NMJs

no voluntary or involuntary control of muscles

Dorsal (Posterior) column system

Mechanoreceptors in the skin and joints detect tactile (discriminative fine touch) and proprioceptive (body position) somatosensory information.

Primary (1st-order) neurons- afferent fiber enters the dorsal root then travels up the dorsal white column (ascending tract) of the spinal cord to form a synapse in the medulla oblongata.

Secondary (2nd-order) – interneuron with its soma in the medulla oblongata extends its axon across the midline then up through the medial lemniscus tract in the pons and midbrain to form a synapse in a nucleus of the thalamus.

Spinothalamic tract 

Nociceptors and Thermoreceptors detect stimuli associated with tissue damage and heat to produce the modalities of pain, itch, and temperature sensation.

Primary (1st-order) neurons- afferent fiber extends from the receptor and enters the dorsal root to form a synapse with an interneuron in the dorsal horn of the spinal cord.

Secondary (2nd-order) – interneuron with its soma in the dorsal horn of the spinal cord extends its axon across the midline then up through the spinothalamic tracts in the spinal cord and brain stem to form a synapse in a nucleus of the thalamus