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24 Cards in this Set

  • Front
  • Back

The medulla also contains nuclei that are components of sensory pathways for gustation (taste), audition (hearing), and equilibrium (balance).

- The gustatory nucleus of the medulla is a part of the gustatory pathway from the tongue to the brain; it receives gustatory input from the taste buds of the tongue




- The cochlear nuclei of the medulla are part of the auditory pathway from the inner ear to the brain; they receive auditory input from the cochlea of the inner ear

Vestibular Nuclei _______

- Of the medulla and pons are components of the equilibrium pathway from the inner ear to the brain; they receive sensory information associated w/ equilibrium from proprioceptors in the vestibular apparatus of the inner ear

The medulla contains nuclei associated with the following cranial nerves :

1. Vestibulocochlear (VIII) Nerves :




Several nuclei in the medulla receive sensory input from and provide motor output to the cochlea of the internal ear via the vestibulocochlear nerves. These nerves convey impulses related to hearing

The medulla contains nuclei associated with the following cranial nerves :

2. Glossopharyngeal (IX) Nerves :




Nuclei in the medulla relay sensory and motor impulses related to taste, swallowing, and salivation via the glossopharyngeal nerves

The medulla contains nuclei associated with the following cranial nerves :

3. Vagus (X) Nerves :




Nuclei in the medulla receive sensory impulses from and provide motor impulses to the pharynx and larynx and many thoracic and abdominal viscera via the vagus nerves

Pons 1

- Lies directly superior to the medulla and anterior to the cerebellum and is about 2.5 cm long




- Consists of both nuclei and tracts




- A bridge that connects parts of the brain with one another

Pons 2

- These connections are provided by bundles of axons




- Some axons of the pons connect the right and left sides of the cerebellum




- Others are part of ascending sensory tracts and descending motor tracts

The pons has two major structural components: a ventral region and a dorsal region.

- The ventral region forms a large synaptic relay station consisting of scattered gray centers called the pontine nuclei




- Entering and exiting these nuclei are numerous white matter tracts, each of which provides a connection between the cortex (outer layer) of a cerebral hemisphere and that of the opposite hemiphere of the cerebellum

The dorsal region of the pons is more like other regions of ________

- The brain stem, medulla, and midbrain




- The dorsal region contains ascending and descending tracts along with the nuclei of cranial nerves

Other nuclei located in the pons are ______

- The pneumotaxic area and the apneustic area




- Together with the medullary rhythmicity area, the pneumotaxic and apneustic areas help to control breathing

The Pons Contains Nuclei With the Following Pairs of Cranial Nerves :

1. Trigeminal (V) Nerves


Nuclei in the pons receive sensory impulses for somatic sensations from the head and face and provide motor impulses that govern chewing via the trigeminal nerves


2. Abducens (VI) Nerves


Nuclei in the pons provide motor impulses that control eyeball movement via abducens nerves

The Pons Contains Nuclei With the Following Pairs of Cranial Nerves :

3. Facial (VII) Nerves




Nuclei in the pons receive sensory impulses for taste and provide motor impulses to regulate secretion of saliva and tears and contraction of muscles of facial expression via the facial nerves

Midbrain (Mesencephalon)

- Extends from the pons to the diencephalon and is about 2.5 cm long




- The aqueduct of the midbrain (cerebral aqueduct) passes through the midbrain, connecting the 3rd ventricle above w/ the 4th below




- Contains both nuclei and tracts

The anterior part of the midbrain contains paired bundles of axons known as ______

- The cerebral peduncles




- They consist of axons of the corticospinal, corticobulbar, and corticopontine tracts, which conduct nerve impulses from motor areas in the cerebral cortex to the spinal cord, medulla, and pons, respectively

The posterior part of the midbrain, called _______

- The tectum, contains 4 rounded elevations




- The 2 superior elevations, nuclei known as superior colliculi, serve as reflex centers for certain visual activities




- Sup. colli. are responsible for reflexes that govern movements of the head, eyes, and trunk in response to visual stimuli

The two inferior elevations of the tectum, called _______

- The inferior colliculi, are part of the auditory pathway, relaying impulses from the receptors for hearing in the inner ear to the brain




- These 2 nuclei are also reflex centers for the startle reflex, sudden movements of the head, eyes, and trunk that occur when you are surprised by a loud noise

The midbrain contains several other nuclei, including the left and right _______

- Substantia nigra, which are large and darkly pigmented




- Neurons that release dopamine, extending from the sub. nigra to the basal nuclei, help control subconscious muscle activities




- Loss of these neurons is associated w/ Parkinsons disease

Also present in the midbrain are the left and right ________

- Red nuclei, which look reddish due to their rich blood supply and an iron-containing pigment in their neuronal cell bodies




- Axons from the cerebellum and cerebral cortex form synapses in the red nuclei, which help control muscular movement

In addition to the well-defined nuclei already described, much of the brain stem consists of small clusters of neuronal cell bodies (gray matter) interspersed among small bundles of myelinated axons (white matter).

- The broad region where white matter and gray matter exhibit a netlike arrangement is known as the reticular formation


- It extends from the superior part of the spinal cord, throughout the brain stem, and into the inferior part of the diencephalon


- Neurons w/in retic. form. have both ascending neurons and descending fucntions

The ascending portion of the reticular formation is called _______

- The reticular activating system (RAS) which consists of sensory axons that project to the cerebral cortex, both directly and through the thalamus




- Many sensory stimuli can activate the ascending portion of the RAS

Among the stimuli are auditory stimuli; mental activites; stimuli from pain, touch, and pressure receptors; and receptors in our limbs and head that keep us aware of the position of our body parts.

- Perhaps the most important function of the RAS is consciousness, a state of wakefulness in which an individual is fully alert, aware, and oriented




- Visual and auditory stimuli and mental activities can stimulate the RAS to maintain consciousness

The RAS is also active during ______

- Arousal, or wakening from sleep




- Another function of the RAS is to help maintain attention and alertness




- Also prevents sensory overload by filtering out insignificant info so that it does not reach consciousness

Inactivation of the RAS produces _______

- Sleep, a state of partial consciousness from which an individual can be aroused




- Damage to the RAS results in coma, a state of unconsciousness from which an individual cannot be aroused

In the lightest stages of coma, brain stem and spinal cord reflexes persist, but in the deepest states even those reflexes are lost, and if respiratory and cardiovascular controls are lost, the patient dies. Drugs such as melatonin affect the RAS by helping to induce sleep, and general anesthetics turn off consciousness via the RAS.

- The descending portion of the RAS has connections to the cerebellum and spinal cord and helps regulate muscle tone, the slight degree of involuntary contraction in normal resting skeletal muscles




- This porttion of the RAS also assists in regulation of heart rate, BP, and respiratory rate