A+P Ch. 14 - The Brain and Cranial nerves

cerebral peduncles

These are the nerve fiber bundles on the ventrolateral surfaces of the midbrain. They contain: 1. descending fibers that go to the cerebellum by way of the pons 2. descending fibers that carry voluntary motor commands issued by the cerebral hemispheres.

Sensory and Motor Nuclei of Cranial Nerves. (pons)

These cranial nerves (V, VI, VII, and VIII) innervate the jaw muscles, the anterior surface of the face, one of the extrinsic eye muscles (the lateral rectus), and the sense organs of the internal ear (the vestibular and cochlear nuclei).

Cerebrovascular diseases

are cardiovascular disorders that interfere with the normal blood supply to the brain. The particular distribution of the vessel involved determines the signs and symptoms. The degree of oxygen or nutrient starvation determines their severity.

middle cerebellar peduncles

are connected to a broad band of fibers that cross the ventral surface of the pons at right angles to the axis of the brain stem. The middle cerebellar peduncles also connect the cerebellar hemispheres with sensory and motor nuclei in the pons.

inferior colliculus

receives auditory input from nuclei in the medulla oblongata and pons

superior colliculus

receives visual inputs from the lateral geniculate nucleus of the thalamus on that side.

olivary nuclei

relay information to the cerebellar cortex about somatic motor commands as they are issued by motor centers at higher levels. The bulk of the olivary nuclei creates the olives, prominent olive-shaped bulges along the ventrolateral surface of the medulla oblongata.

epithalamus

roof of the diencephalon superior to the third ventricle. - The anterior portion of the epithalamus contains an extensive area of choroid plexus that extends through the interventricular foramina into the lateral ventricles. - The posterior portion of the epithalamus contains the pineal gland, an endocrine structure that secretes the hormone melatonin.

choroid Plexus

s an area within each ventricle that produces CSF.

primary fissure

separates the anterior and posterior lobes of the cerebellum

left hemisphere of Cerebrum

typically contains the general interpretive and speech centers and is responsible for language-based skills.

Functions of the limbic system

(1) establishing emotional states; (2) linking the conscious, intellectual functions of the cerebral cortex with the unconscious and autonomic functions of the brain stem (3) facilitating memory storage and retrieval. The sensory cortex, motor cortex, and association areas of the cerebral cortex enable you to perform complex tasks, but it is largely the limbic system that makes you want to do them. For this reason, the limbic system is also known as the motivational system.

cerebellar nuclei

- Information about the motor commands issued at the conscious and subconscious levels reaches the Purkinje cells indirectly, after being relayed by nuclei in the pons or by the cerebellar nuclei embedded within the arbor vitae.

amygdaloid body

- It appears to act as an interface between the limbic system, the cerebrum, and various sensory systems. It plays a role in regulating heart rate, in responding to fear and anxiety and controlling the "fight or flight" response by the sympathetic division of the ANS, and in linking emotions with specific memories.

Purkinje cells

- Like the cerebrum, the cerebellum has a superficial layer of neural cortex. The cerebellar cortex contains relatively huge, highly branched cells called... - The extensive dendrites of each of these cells receive input from up to 200,000 synapses— more than any other type of brain cell.

ataxia

- The cerebellum can be permanently damaged by trauma or stroke. Drugs such as alcohol can also temporarily affect it. The result is _______, a disturbance in muscular coordination. In severe ataxia, the individual cannot sit or stand without assistance.

three gyri in the limbic lobe

- The cingulate gyrus ( girdle or belt) sits superior to the corpus callosum. - The dentate gyrus and the parahippocampal (pa-ra-hip-o. -KAM-pal) gyrus form the posterior and inferior portions of the limbic lobe. - These gyri conceal the hippocampus, a nucleus inferior to the floor of the lateral ventricle. To early anatomists, this structure resembled a sea horse (hippocampus). This nucleus is important in learning, especially in the storage and retrieval of new long-term memories. - The fornix (FOR-niks, arch) is a tract of white mat- ter that connects the hippocampus with the hypothalamus

arbor vitae

- The internal white matter of the cerebellum forms a branching array that in sectional view resembles a tree. Anatomists call it the "tree of life". It connects the cerebellar cortex and nuclei with the cerebellar peduncles.

The Diencephalon

- contains the left and right thalamus - they contain relay and processing centers for sensory info. - the hypothalamus is the floor of the diencephalon. It contains centers involved with emotions, autonomic function, and hormone production. - contains the pituitary gland which is part of the endocrine system. Connected to the hypothalamus by the infundibulum. - The diencephalon is a structural and functional line between the cerebral hemispheres and the brain stem.

The Cerebrum

...Is the largest portion of the adult brain. - Has a left and right hemispheres - The brain is covered by a superficial layer of gray matter called cortex. The cerebral cortex is the highly folded neural cortex that covers the surface of the cerebrum. - Gyri are the elevated rides of the folds. Sulci are the depressions, or grooves. - Fissures are grooves that are even deeper than sulci

The Cerebellum

...is the second largest part of the brain - partially hidden by the cerebral hemispheres - its neural cortex is called the cerebellar cortex - In function, the cerebellum adjusts ongoing movement by comparing arriving sensations with previously experienced sensations. This allows us to perform the same movements over again.

six major regions of the brain

1. Cerebrum 2. Cerebellum 3. Diencephalon 4. Midbrain (part of brainstem) 5. Pons (part of brainstem) 6. Medulla Oblongata (part of brainstem)

FUNCTIONS OF THE HYPOTHALAMUS

1. The Subconscious Control of Skeletal Muscle Contractions. 2. The Control of Autonomic Function 3. The Coordination of Activities of the Nervous and Endocrine Systems. 4. The Secretion of Two Hormones. The hypothalamus secretes antidiuretic hormone (ADH, also called vasopressin) and oxytocin (OXT). 5. The Production of Emotions and Behavioral Drives 6. Coordination between Voluntary and Autonomic Functions. 7. The Regulation of Body Temperature. 8. The Control of Circadian Rhythms.

Cerebrospinal Fluid

Functions: - Cushioning delicate neural structures - Supporting the brain - Transporting Nutrients, Chemical messengers, and waste products

respiratory rhythmicity centers

In the Medulla Oblongata set the basic pace for respiratory movements. Their activity is regulated by inputs from the apneustic and pneumotaxic respiratory centers of the pons.

cardiovascular centers

Located in the Medulla Oblongata They adjust the heart rate, the strength of cardiac contractions, and the flow of blood through peripheral tissues.

red nucleus

Midbrain. contains numerous blood vessels, which give it a rich red color. This nucleus receives information from the cerebrum and cerebellum and issues subconscious motor commands that affect upper limb position and background muscle tone.

blood-brain barrier (BBB)

Neural tissue in the CNS is isolated from the general circulation by the blood-brain barrier (BBB). - This barrier is formed by capillary endothelial cells that are extensively interconnected by tight junctions. - These junctions prevent materials from dif- fusing between endothelial cells. - Substances do not have free access to the CNS, however, because specialized ependymal cells create a blood-CSF barrier. These cells, also interconnected by tight junctions, surround the capillaries of the choroid plexus. The blood-brain barrier remains intact throughout the CNS except in small areas known as circumventricular organs (CVOs), which have fenestrated capillaries. Because they are outside the BBB, they provide a direct link between the CNS and the peripheral blood and they play a role in neuroendocrine function.

Nuclei Involved with the Control of Respiration (Pons)

On each side of the pons, the reticular formation in this region contains two respiratory centers: the apneustic center and the pneumotaxic center. These centers modify the activity of the respiratory rhythmicity centers in the medulla oblongata.

tectum

Roof of the midbrain, it is the region posterior to the cerebral aqueduct. It contains two pairs of sensory nuclei known collectively as the corpora quadrigemina.

The brainstem

The brainstem (midbrain, pons, medulla oblongata)

Adjusting the Postural Muscles of the Body.

The cerebellum coordinates rapid, automatic adjustments that maintain balance and equilibrium. It makes these alterations in muscle tone and position by modifying the activities of motor centers in the brain stem.

Programming and Fine-Tuning Movements Controlled at the Conscious and Subconscious Levels

The cerebellum refines learned movement patterns, such as riding a bicycle or playing the piano. It performs this function indirectly by regulating activity along motor pathways at the cerebral cortex, basal nuclei, and motor centers in the brain stem. The cerebellum compares the motor commands with proprioceptive information (position sense) and stimulates any adjustments needed to make the movement smooth.

Sensory and Motor Nuclei of Cranial Nerves (Medulla Oblongata)

The medulla oblongata contains sensory and motor nuclei associated with five of the cranial nerves (VIII, IX, X, XI, and XII). These cranial nerves provide motor commands to muscles of the pharynx, neck, and back as well as to the visceral organs of the thoracic and peritoneal cavities. Cranial nerve VIII carries sensory information from receptors in the internal ear to the vestibular and cochlear nuclei, which extend from the pons into the medulla oblongata.

reticular activating system (RAS)

The midbrain also contains the (RAS), a specialized component of the reticular formation. Stimulation of the RAS makes you more alert and attentive; damage to the RAS produces unconsciousness.

Relay Stations along Sensory and Motor Pathways. (medulla)

The nucleus gracilis and the nucleus cuneatus pass somatic sensory information to the thalamus. Tracts leaving these brain stem nuclei cross to the opposite side of the brain before reaching their destinations. This crossing over is called a decussation (de. -kuh-SA-shun; decus- satio, crossing over), and the site is the decussation of pyramids.

3. Nuclei and Tracts That Process and Relay Information Sent to or from the Cerebellum. (Pons)

The pons links the cerebellum with the brain stem, cerebrum, and spinal cord.

The right hemisphere

The right hemisphere is typically responsible for spatial relationships and analyses.

ventricles of the brain

are lined with cells called ependyma. - Each of the cerebral hemisphere contains a large lateral ventricle. - The Septum Pellucidum is a thin medial partition that separates the two lateral ventricles - The ventricle in the diencephalon is called the third ventricle. - The two lateral ventricles are not directly connected, but each communicates with the third ventricle through an interventricular foramen. - The midbrain has a slender canal known as the cerebral aqueduct. This passageway connects the third ventricle with the fourth ventricle. - The ventricles are filled with CSF. it continually circulates from the ventricles and central canal into the subarachnoid space of the surrounding cranial meninges.

tegmentum

area of Midbrain anterior to the cerebral aqeuduct

inferior cerebellar peduncles

communicate between the cerebellum and nuclei in the medulla oblongata and carry ascending and descending cerebellar tracts from the spinal cord.

The medulla oblongata

connects the brain to the spinal cord. It relays sensory info to the thalamus and to centers in other portions of the brain stem. Heart rate, blood pressure, and digestion are regulated here.

The midbrain

contains nuclei that process visual and auditory information and control reflexes stimulated by these stimuli.

Association areas, such as the somatic sensory association area, visual association area, and premotor cortex

control our ability to understand sensory information and coordinate a motor response.

prefrontal cortex

coordinates information from the secondary and special association areas of the entire cortex and performs abstract intellectual functions.

basal nuclei

include the caudate nucleus, globus pallidus, and putamen; they control muscle tone and coordinate learned movement patterns and other somatic motor activities.

substantia nigra

is the largest midbrain nucleus. It lies lateral to the red nucleus. The gray matter in this region contains darkly pigmented cells, giving it a black color. The pigment is melanin and here it is a byproduct of dopamine synthesis. - The substantia nigra inhibits activity of the basal nuclei in the cerebrum. The basal nuclei are involved in the subconscious control of muscle tone and learned movements.

superior cerebellar peduncles

link the cerebellum with nuclei in the midbrain, diencephalon, and cerebrum.

Ascending, Descending, and Transverse Tracts

longitudinal tracts interconnect other portions of the CNS. The middle cerebellar peduncles are connected to the transverse fibers, which cross the anterior surface of the pons. These fibers are axons that link nuclei of the pons (pontine nuclei) with the cerebellar hemisphere of the opposite side.

The pons

meaning 'bridge', connects the cerebellum to the brain stem. Contains nuclei involved with somatic and visceral motor control. Also contains tracts and relay centers.

limbic lobe

of the cerebral hemisphere consists of the superficial folds, or gyri, and underlying structures adjacent to the diencephalon. - The gyri curve along the corpus callosum, a fiber tract that links the two cerebral hemispheres

solitary nucleus

on either side receives visceral sensory information that reaches the CNS from the spinal nerves and cranial nerves. This information is integrated and for- warded to other autonomic centers in the medulla oblongata and elsewhere.

folia

or folds of the cerebellum surface, are less prominent than the folds in the surfaces of the cerebral hemispheres

A cerebrovascular accident (CVA)

or 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.