IUPUI N261 - The Nervous System (The Brain and Spinal Cord)

Where is most of the neural tissue in our body found?

in the brain (95% of neural tissue)

neurocoel

hollow neural tube with a fluid-filled internal cavity

ventricles

enlarged chambers

primary brain vesicles

Prosencephalon (forebrain)

Mesencephalon (midbrain)

Rhombencephalon (hindbrain)

posencephalon

forebrain

mesencephalon

midbrain

rhombencephalon

hindbrain

What are the secondary brain vesicles?

subdivisions of the prosencephalon and the rhombencephalon

What are the two subdivisions of the prosencephalon?

telencephalon and the diencephalon

What are the two subdivisions of the rhombencephalon?

metencephalon and myelencephalon

telencephalon

cerebrum. possesses the paired cerebral hemispheres that dominate the superior and lateral surfaces of the adult brain.

diencephalon

thalamus and hypothalamus. has a roof (epithalamus), walls (left and right thalamus) and floor (hypothalamus). optic vesicles extend laterally from the sides.

metencephalon

pons and cerebellum. closest to mesencephalon

myelencephalon

medulla oblongata. closest to spinal cord

brainstem

contains important processing centers that relay information to and from the cerebrum or cerebellum

medulla oblongata

connects brainstem to the spinal cord. relays sensory information to the thalamus and other centers within brainstem. contains major centers regulating autonomic functions

pons

superior to the medulla. connects cerebellum to the brainstem. controls somatic and visceral motor functions

epithalamus

contains pineal gland

thalamus

relays messages between lower brain centers and cerebral cortex

hypothalamus

visceral control center. contains centers for emotions, autonomic nervous system function, and hormone production. link between nervous and endocrine systems

pituitary gland

endocrine gland at the base of the brain

hypophysis

narrow stalk that connects the hypothalamus and the pituitary gland

cerebellum

second largest part of the brain. automatically adjusts motor activities based on sensory information and memories of learned movements

cerebrum

largest part of the brain. conscious thought processes, intellectual functions, memory storage and retrieval, and complex motor patterns originate here

cerebral hemispheres

right and left sides of cerebrum

longitudinal fissure

separates cerebral hemispheres

sulci

folds in the brain

gyri

ridges of the brain

cortex

outermost covering of the brain consisting of densely packed neurons, responsible for higher thought processes and interpretation of sensory input

How many ventricles are present in the adult brain?

four

What fills and lines each ventricle of the brain?

they are filled with cerebrospinal fluid and lined by ependymal cells

lateral ventricles

a set of paired ventricles lying within the cerebral hemispheres.

septum pellucidum

thin membrane that separates lateral ventricles

What is the structure of the lateral ventricles of the brain?

body, anterior horn, posterior horn, inferior horn. body lies within parietal lobe, anterior horn extends into frontal lobe. posterior horn projects into occipital lobe. inferior horn curves laterally within temporal lobe

interventricular foramen

connects lateral ventricles to third ventricle

third ventricle

the ventricle located in the center of the diencephalon

cerebral aqueduct

connects the third and fourth ventricles

fourth ventricle

the ventricle located between the cerebellum and the dorsal pons, in the center of the metencephalon

What five things are involved in protection, support, and nourishment of the brain?

bones of the skull, cranial meninges, blood brain barrier, cerebrospinal fluid, rich blood supply

cranial meninges

protect the brain by acting as shock absorbers, preventing contact with the skull bones. continuous with the spinal meninges with the same three layers.

dura mater

Outermost layer of the meninges

periosteal cranial dura

fused to periosteum lining the cranial bones.

meningeal cranial dura

innermost layer of the dura mater

dural sinuses

spaces that collect blood that has circulated through the brain

In what four locations does the dura fold and extend deep into the brain?

falx cerebri, tentorium cereblli, falx cerebelli, diaphragma sellae

falx cerebri

found between cerebral hemispheres in the longitudinal fissure. attaches to the crista galli and interior occipital crest and tentorium cerebelli.

superior and inferior sagittal sinuses

lie within falx cerebri dura folds

tentorium cerebelli

supports and protects the two occipital lobes of the cerebrum. separates cerebellar hemispheres from cerebrum.

transverse sinus

lies within the tentorium cerebelli

falx cerebelli

divides the two cerebellar hemispheres along the midsagittal line inferior to the tentorium cerebelli

diaphragma sellae

small segment of dura mater lining the sella turcica of the sphenoid. anchors dura mater to the sphenoid and surrounds base of pituitary gland

arachnoid amter

delicate membrane covering the brain between surperficial dura matera and deeper pia mater.

subdural space

separates the dura mater from the arachnoid mater

subarachnoid space

delicate, weblike meshwork of collagen and elastic fibers linking the arachnoid mater to the underlying pia mater

arachnoid granulations

extensions of the arachnoid mater that allow excess CSF to be absorbed by the dural sinuses.

cranial arachnoid mater

acts as roof over the cranial blood vessels, and underlying pia mater forms a floor

arachnoid trabeculae

supports cerebral arteries and veins. surrounded by CSF

pia mater

tightly attached to the surface of contours of the brain, sticking to its contours and lining the sulci. anchored to the surface of the brain by the processes fo astrocytes. highly vascular

blood brain barrier

a filtering mechanism of the capillaries that carry blood to the brain and spinal cord tissue, blocking the passage of certain substances.

In what four regions of the brain is the blood brain barrier notably different?

portions of the hypothalamus, where capillary endothelium has increased permeability. capillaries in the pineal gland, which is increasingly permeable. capillaries at a choroid plexus, the site of CSF production for maintenance of blood-CSF barrier. capillaries in the posterior lobe of pituitary gland.

endothelial transport across BBB

selective and directional.

What are the main functions of cerebrospinal fluid?

preventing contact between delicate neural structures and surrounding bones. supporting the brain. transporting nutrients, chemicals, and wastes, except at the choroid plexus where the ependymal lining is freely permeable.

Where is CSF formed?

choroid plexuses in all ventricles of the brain. capillaries are fenestrated and highly permeable, but large, highly specialized ependymal cells cover them. choroid plexus also removes waste from CSF and fine tune its composition

lateral apertures

pair of openings from the fourth ventricle to the subarachnoid space on either side and between the medulla and cerebellum

median aperture

an opening in the roof of the fourth ventricle that connects to the subarachnoid space

How does CSF reenter circulation?

through the arachnoid granulations

How are energy demands in the brain met?

extensive vascular supply

cerebrovascular diseases

circulatory disorders that interfere with the normal blood supply to the brain

cerebrovascular accident (CVA)

stroke. occurs when the blood supply to a portion of the brain is shut off. affected neurons begin to die in a matter of minutes

all communication between the brain and spinal cord involves tracts ascending or descending through what?

the medulla oblongata

What are the three groups of nuclei in the medulla oblongata?

relay stations and processing centers, nuclei of cranial nerves, autonomic nuclei

gracile nucleus

relay somatic sensory information to the thalamus

cuneate nucleus

fine touch and proprioception of the upper body

solitary nucleus

receives visceral sensory information that reaches the CNS from the spinal nerves and cranial nerves

olivary nuclei

relay information from spinal cord, cerebral cortex, diencephalon, and brainstem to the cerebellar cortex.

olives

prominent bulges formed by the bulk of olivary nuclei that occur along the ventrolateral surface of the medulla oblongata.

reflex centers

receive input from cranial nerves, the cerebral cortex, diencephalon, and brainstem, and their output adjusts the activities of one or more peripheral systems

What are the major reflex centers?

cardiovascular centers and respiratory rhythmicity centers,

cardiovascular centers

adjust heart rate, strength of cardiac contractions, and the flow of blood through peripheral tissues. divided into cardiac and vasomotor centers.

respiratory rhythmicity centers

set basic pace for breathing. inputs from apneustic and pneumotaxic centers within the pons regulate their activity

What is contained in the pons?

sensory and motor nuclei for four cranial nerves, nuclei regulating the involuntary control of respiration, nuclei that process and relay cerebellar commands, and ascending, descending, transverse tracts

What is contained in the white matter of the pons?

ascending and descending tracts (interconnect other portions of the CNS), and transverse fibers (interconnect cerebellar hemispheres, interconnect pontine nuclei with the cerebellar hemispheres on the contralateral side)

What is contained in the gray matter of the pons?

respiratory centers (modify output of respiratory centers in the medulla oblongata), reticular formation (automatic processing of incoming sensations and outgoing motor commands), and other nuclei/centers (nuclei associated with four cranial nerves and the cerebellum)

tectum

the surface posterior to the cerebral aqueduct

corpora quadrigemina

located in the midbrain; contains reflex centers for vision and auditory reflexes.

superior collicui

receive visual input from the lateral geniculate of the thalamus on the ipsilateral side

inferior colliculi

receive auditory input from the nuclei in the medulla oblongata; some of this information is forwarded to the medial geniculate on the ipsilateral side

red nucleus

a large nucleus of the midbrain that receives inputs from the cerebellum and motor cortex and sends axons to motor neurons in the spinal cord.

substantia nigra

lateral to the red nucleus. regulates motor output of the basal nuclei

cerebral peduncles

nerve fiber bundles on the ventrolateral surfaces of the midbrain. ascending fibers synapse in the thalamic nuclei and descending fibers of corticospinal pathway carrying voluntary motor commands from the primary cortex of each cerebral hemisphere

pineal gland

endocrine structure that secretes melatonin.

melatonin

regulates day/night cycles, and some effects on reproductive function

Where is most of the nervous tissue of the diencephalon concentrated?

in left and right thalamus

thalamic nuclei

provide integration and relay centers for sensory and motor pathway

What nerves synapse in the thalamic nuclei?

all ascending sensory information from the spinal cord and cranial nerves

How do the thalami act as information filters?

by processing all of the incoming sensory information and then passing on only a small portion to the cerebrum or brainstem.

What separates the two thalami?

the third ventricle

interthalamic adhesion

medial projection of gray matter that extends into the ventricle from the thalamus on either side.

What forms the lateral border of each thalamus?

fibers of the internal capsule

What are the five major groups of thalamic nuclei?

anterior, medial, ventral, posterior, lateral