A&P Chapter 13 CNS & Cranial Nerves

cerebrum, diencephalon, brainstem, and cerebellum

4 main regions of the brain

Gyri

Fold of brain tissue that allow more neurons to fit within the endocranium

Sulci

Shallow depressions between gyri

Fissures

Deeper grooves between gyri

Rostral

Toward the nose; anterior

Caudal

Toward the tail; posterior

Cerebrum

Composed of the 2 cerebral hemispheres and the 5 lobes

Diencephalon

Includes the thalamus, hypothalamus, epithalamus,

Brainstem

Composed of the pons and the medulla oblongata

Cerebellum

arbor vitae

Neurulation

Occurs in the 3rd week of embryonic development. The ectoderm that overlies the notochord thickens forming the neural plate. The neural plate (induced by the notochord) forms the neural tube. This process ultimately forms all nervous tissue structures

Brain; spinal cord

The rostral part of the neural tube expands to form the \_______, while the caudal part of the neural tube expands to form the \__________.

Gray matter

Primarily derives its color from the motor neuron and interneuron cell bodies and their associated capillary beds, as well as the dendrites and some unmyelinated axons. In the brain this is located on the outer surface--the cerebral cortex and deep in the cerebrum--cerebral nuclei

White matter

Derives its color from the myelin on the abundant myelinated axons

Gray matter and white of the brain

Cranial meninges

3 connective tissue layers that separate and support the soft tissue of the brain from the bones of the cranium, enclose and protect some of the blood vessels that supply the brain, and help contain and circulate cerebrospinal fluid.

Dura mater, arachnoid mater, pia mater

Layers of meninges from most superficial to deepest

Pia mater

Thin layer of areolar connective tissue that tightly adheres to the brain

Arachnoid mater

Lies external to the pia mater; Partially composed of a delicate web of collage and elastic fibers.

Subarachnoid space

Immediately deep to the arachnoid mater and contains cerebrospinal fluid

Arachnoid trabeculae

Web of collagen and elastic fibers of the arachnoid mater extending to the pia mater.

Subdural space

Potential space between the arachnoid mater and the overlying dura mater. Becomes an actual space if blood or fluid accumulates there--a condition called subdural hematoma

Dura mater

The strongest of the meninges. Outer layer of dense irregular connective tissue covering that is composed of two layers: the meningeal layer and the periosteal layer.

Periosteal layer

More superficial layer of the dura mater that forms the periosteum on the internal surface of the cranial bones

Meningeal layer

Layer of the dura mater that is immediately superficial to the arachnoid layer. It is usually fused to the periosteal layer, except in specific areas where these 2 layers separate to form large, blood-filled spaces (dural venous sinuses).

Dural venous sinuses

Large, blood-filled spaces that are typically triangular in cross section, and unlike most other veins, they do not have valves to regulate venous blood flow They drain blood from the brain.

Epidural space

Contains blood vessels that nourish the meninges and bones of the cranium; may potentially become a real space separate the bones of the skull and the dura mater if blood or fluid accumulates within it

Cranial dura septa

membranous partitions that separate specific parts of the brain and provide additional stabilization and support to the brain. There are 4 of them: the falx cerebra, tantorium cerebelli, falx cerebelli, and diaphragma sellae

Ventricles

4 cavities within the brain that are derived from the neural canal. All are lined with ependymal cells and contain cerebrospinal fluid. Cavities are connected with one another as well as with the central canal of the spinal cord

Lateral ventricles

ventricles located in the cerebrum and are separated by a thin medial partition called the septum pellucidum.

Septum pellucidum

Thin medial partition that separates the lateral ventricles

Third ventricle

Ventricle located within the diencephalon; small and thin ventricle. Connects to each lateral ventricle though the interventricular foramen

Cerebral aqueduct

Narrow canal that passes through the midbrain and connects the 3rd ventricle with the sickle-shaped 4th ventricle

fourth ventricle

Sickle-shaped ventricle located between the pons, medulla oblongata, and cerebellum. It opens to the subarachnoid space. Narrows at its inferior end and merges with the slender central canal in the spinal cord

Cerebrospinal fluid (CSF)

Fluid that protects the brain by providing cushioning and buoyancy to the and aids in stable chemical environment by transporting nutrients and chemical messengers to the brain and removing waste

500 mL/day (1/2 liter)

How much cerebrospinal fluid is formed/day?

100 mL-160mL

Range of CSF in the subarachnoid space at any given time

Choroid plexus

Forms cerebrospinal fluid and is composed of a layer of glial cells called ependymal cells and the blood capillaries that lie within the pia mater

Formation of CSF by choroid plexus

Blood plasma is filtered from the blood capillaries and its composition is modified by the ependymal cells : more Na+ and Cl- is added and a little glucose, K+, and Ca2+ is taken away from it.

Circulation of CSF

CSF is produced by the choroid plexus--\>lateral ventricles--\>third ventricles--\>4th ventricle--\>subarachnoid space and central canal

Choroid plexus, ependymal cells, and subarachnoid space fluid

Although the choroid plexus is most responsible, what all contributes to the formation of CSF?

Fluid pressure

In the subarachnoid space, what insures the flow of CSF into the venous sinuses?

Blood-brain barrier

Barrier that strictly regulates which substances can and cannot enter the interstitial fluid of the brain to help prevent exposure of neurons in the brain to drugs, waste products in the blood, and variations in levels of normal substances (like hormones) that could adversely affect brain function.

Formation of the blood-brain barrier

Special capillaries are responsible for this. They contain endothelial cells with tight junctions that prevent passage of material between cells. Capillaries are also wrapped in the perivascular feet of astrocytes

Perivascular feet of astrocytes

Extension of astrocytes that form the outermost portion of the blood brain barrier

Choroid plexus, hypothalamus, and pineal gland

What 3 locations is the blood-brain barrier significantly reduced?

Cerebrum

Location of conscious thought processes and the origin of all complex intellectual functions: intelligence and reasoning; thought, memory, and judgement; emotions; voluntary motor, visual and auditory activities

Tracts

Bundles of axons; form white matter regions that allow for communication between the cerebral hemispheres

Corpus callosum

Largest of the white matter tracts of the brain that connects the cerebral hemispheres.

Crossed nature

Cerebral hemispheres receive their sensory information from, and project motor commands to, the opposite side of the body.

Left

The right cerebral hemisphere controls what side of the body?

frontal, parietal, occipital, temporal, and isula

What are the 5 lobes of the cerebrum?

Frontal lobe

Responsible for motor control, decision making, personality, concentration, verbal communication, and planning

Parietal lobe

Responsible for general sensory functions (shape and texture evaluation of objects being touched)

Temporal lobe

Responsible for hearing and smelling

Occipital lobe

Responsible for visual sensations and visual memory

Insula lobe

Responsible for memory and sense of taste

Central sulcus

Deep groove that divides the frontal lobe from the parietal lobe

Lateral sulcus

Deep groove that forms the border of the frontal lobe inferiorly; separates the frontal and parietal lobes from the temporal lobe

Precentral gyrus

Anatomic feature of the frontal lobe, which is the mass of nervous tissue immediately anterior to the central sulcus.

Central sulcus

Lateral sulcus

Precentral gyrus

Parieto-occipital sulcus

Posterior border of the parietal lobe. Separates the parietal and occipital lobes.

Postcentral gyrus

Anatomic feature of the parietal lobe. Mass of nervous tissue immediately posterior to the central sulcus.

Broca's area

MOVEMENT for speech and regulating pattern of breathing; most often on left side of brain

Frontal eye field

Regulates eye movements for reading and binocular vision; located on the superior surface of middle frontal gyrus

Premotor cortex

Somatic motor association area; Plans and coordinates learned, skilled motor activities involving skeletal muscles. E.g., playing the guitar

Primary motor cortex

Somatic motor area; Initiates voluntary skeletal muscle activity; located within the prefrontal gyrus of the frontal lobe. Left portion of this cortex controls the right-side of voluntary muscles and vice versa.

Primary somatosensory cortex

Housed within the post-central gyrus of the parietal lobes. Neurons within this cortex receive general info from the skin regarding touch, pressure, pain, and temperature receptors, as well as sensory input form proprioceptors

Somatosensory association area

Located within the parietal lobe and lies immediately posterior to the primary somatosensory cortex. Integrates sensory info and INTERPRETS sensations to determine the texture, temperature, pressure, and shape of objects

Primary visual cortex and association area

Located in occipital lobe; receives, processes, and integrates visual information

Primary auditory cortex and association area

Located in the temporal lobe; Receives and processes sound and memories

Primary olfactory area

Located in the temporal lobe and is responsible for consciousness of smell--mine is probably broken

Primary gustatory area

Located in the insula lobe and is responsible for processing taste

Prefrontal cortex

Located in the rostral portions of the frontal lobes and anterior to both the primary motor and premotor cortices. Associated with complex thought, judgment, personality, planning, deciding.

Wernicke's area

Typically located within the left hemisphere. It is involved in recognizing, understanding, and comprehending spoken or written language. this area and Broca's area must work together for fluent communication to occur

Gnostic area

Integrates all somatosensory, visual, and auditory information being processed by the association areas and develops perception (consciousness). It is composed of regions of the parietal, occipital, and temporal lobes

Association tracts

Tracts that connect different regions of the cerebral cortex within the same hemisphere.

Arcurate fibers

Short association tracts are composed of these. E.g., tract that connects the premotor or motor association area with the primary motor cortex ( both located in the frontal lobe)--composed of these fibers

Longitudinal fasciculi

Longer association tracts that connect gyri in different lobes of the same hemisphere. E.g., tract that connects the Wernicke area to Broca's area

Commisures

Tracts that connect between hemispheres. E.g., corpus callosum

Projection tracts

Tracts that link cerebral cortex to inferior brain regions and spinal cord. E.g., the corticospinal tracts that carry motor signals for the cerebrum to the brainstem and spinal cord.

Petalias

Protrusion of one side of the brain vs. the other; correlated with handedness. E.g., right handed people typically have a right frontal protrusions and left occipital protrusions

Left hemisphere--categorical

In most people, specialized for language, categorization, analysis

Right hemisphere--representational

In most people, visuospatial relationships, imagination, comparison of senses

Corpus callosum and commisures

regions of the brain most responsible for communication of the cerebral hemispheres

Women

Which gender has a thicker corpus callosum and therefore, more connections between hemispheres?

Men

Which gender suffers more functional loss with damage to a cerebral hemisphere?

Right-handers

Individuals that are most often left hemisphere dominant--categorical; speech

Cerebral nuclei

Paired, irregular masses of gray matter buried deep within the central white matter in the basal region of the cerebral hemispheres inferior to the floor of the lateral ventricle. They help regular motor output and to inhibit unwanted movement. Includes the caudate nucleus, the amygdaloid body, the claustrum, and the lentiform nucleus

Caudate nucleus

Part of the cerebral nuclei that is parallel with the lateral ventricles. Responsible for pattern and rhythm of walking movements

Lentiform nucleus

Part of cerebral nuclei that is located between the insula and diencephalon. Responsible for movements at subconscious level; Influences thalamus to adjust muscle tone

Amygdaloid body

Part cerebral nuclei that is responsible for mood, emotions, and behavioral activities.

Claustrum

Part of cerebral nuclei that is located inferior to insula cortex. It's responsible for subconscious processing of visual information

Diencephalon

Function includes relaying and switching centers for sensory, motor and visceral pathways. Includes the epithalamus, thalamus, and hypothalamus

Epithalamus

Portion of diencephalon. Contains pineal gland and habenular nuclei

Pineal gland

Melatonin and circadian rhythm

Habenular nuclei

Visceral and emotional response to odor

Thalamus

Portion of diencephalon that is responsible for conscious senses except olfaction. It relays signals to appropriate cortex and filters out distractions