BIO 271 CHP. 15 - The Diencephalon, Brainstem and Cerebellum

• Is a part of the prosencephalon sandwiched between the inferior regions of the cerebral hemispheres

• Region is often referred to as the “in-between brain”

• Provides relay and switching centers for some sensory and motor pathways and for control of visceral activities

What is this called?

Diencephalon

The components of the diencephalon include the what?

• Epithalamus

• Thalamus

• Hypothalamus

• Partially forms the posterior roof of the diencephalon

• Covers the third ventricle

• Posterior portion of this houses the pineal gland and the habenular nuclei

What is this called?

Epithalamus

• Is an endocrine gland

• Secretes the hormone melatonin, which appears to help regulate day-night cycles known as the body’s circadian rhythm

What is this called?

Pineal gland

• Refers to paired oval masses of gray matter that lie on each side of the third ventricle

• Forms the superolateral walls of the third ventricle

• (Midsagittal section) located between the anterior commissure and the pineal gland

• Principal and final relay point for sensory information that will be processed and projected to primary somatosensory cortex

What is this called?

Thalamus

Is a small, midline mass of gray matter that connects the right and left thalamic bodies

What is this called?

Interthalamic adhesion

Each part of the thalamus is a gray matter mass is composed of about a dozen major what?

• Axons from these nuclei project to specific regions of the cerebral cortex

Thalamic nuclei

Is the anteroinferior region of the diencephalon

Thin, stalklike infundibulum extends inferiorly from the ___________ to attach to pituitary gland

Hypothalamus

• Master control of the autonomic nervous system

• Master control of the endocrine system

• Regulation of body temperature

• Control of emotional behavior

• Control of food intake

• Control of water intake

• Regulation of sleep-wake (circadian) rhythms

These are all functions of what?

Hypothalamus

• Connects the prosencephalon and cerebellum to the spinal cord

• Bidirectional passageway for all extending between the cerebrum and the spinal cord

• Contains many autonomic center and reflex required for our survival

• Houses nuclei of may of the cranial nerves

What is this called?

Brainstem

Three regions form the brainstem, what are they?

• Superiorly placed midbrain

• The pons

• The inferiorly placed medulla oblongata

Is the superior portion of the brainstem

What is this called?

Midbrain

Extending through the midbrain is the what connecting the third and fourth ventricle

Cerebral aqueduct

Are motor tracts located on the anterolateral surfaces of the mesencephalon

What is this called?

Cerebral peduncles

• Are the superior nuclei

• Called visual reflex centers because they help visually track moving objects and control reflexes such as turning the eyes and head in response to a visual stimulus

What is this called?

Superior colliculi

• Are auditory reflex centers

• Control the turning of your head and eyes in unison toward an unexpected sound

What is this called?

Inferior colliculi

• Is bulging region on the anterior part of the brainstem that forms from part of the metencephalon

• Housed within this structure is sensory and motor tracts that connect to the brain and spinal cord

• Regulates skeletal muscles of breathing

What is this called?

Pons

• Formed from the myelencephalon

• Resembles the spinal cord with its flattened, round shape and narrow central canal

• As the central canal extends anteriorly toward the pons, it enlarges and becomes the fourth ventricle

• All communication between the brain and spinal cord involves tracts that ascend or descend through this structure

What is this called?

Medulla oblongata

The anterior surface of the medulla oblongata exhibits 2 longitudinal ridges called what?

Pyramids

Immediately lateral to each pyramid of the medulla oblongata is a distinct bulge called the what?

Olive

The medulla oblongata contains several what which regulate functions vital life?

• These group together to form centers in the medulla oblongata

Autonomic nuclei

Name the autonomic centers in the medulla oblongata

• Cardiac center

• Vasomotor center

• Medullary respiratory center

Regulates both the heart’s rate and its strength contraction

What is this called?

Cardiac center

• Controls blood pressure by regulating the contraction and relaxation of smooth muscle in the walls of the smallest arteries (arterioles) to alter diameter

• Blood pressure increases when vessel wall constrict and lowers when vessel walls dilate

What is this called?

Vasomotor center

• Which regulates the respiratory rate

• Composed of ventral respiratory group and a dorsal respiratory group

• Influenced by the pontine respiratory center in the pons

What is this called?

Medullary respiratory center

Other nuclei in the medulla oblongata

• Coughing

• Sneezing

• Salivating

• Swallowing

• Gagging

• Vomiting

• Second largest part of the brain

• Develops from the metencephalon

• Has a complex, highly convoluted surface covered by a layer of cerebellar cortex

• Coordinates and fine-tunes skeletal muscle movements and ensures that skeletal muscle contraction follows the correct pattern leading to smooth, coordinated movements

What is this called?

Cerebellum

The folds of the cerebellar cortex are called what?

Folia

The cerebellum is composed of left and right what?

Cerebellar hemispheres

Each cerebellar hemisphere consists of what two lobes?

• Anterior lobe

• Posterior lobe

Along the midline, a narrow band of cortex known as what separates the left and right cerebellar hemispheres?

Vermis

The cerebellum is partitioned internally into 3 regions, name them

1. Outer gray matter layer of cortex

2. Internal region of white matter

3. Deepest gray matter layer

The deepest gray matter layer of the cerebellum is composed of what?

Cerebellar nuclei

The white matter of the cerebellum is called what?

• Hint: It resembles branches of a tree

Arbor vitae

• Stores memories of previously learned movement patterns (regulated by activity along both voluntary and involuntary motor pathways at the cerebellar cortex)

• The cerebrum initiates a movement and sends a rough draft of movement to this structure which coordinates it and fine-tunes it

• Receives proprioceptive (sensory) information from the muscles and joints and uses this information to regulate the body’s position

• Help regulate behavioral expression and cognitive skills, language processing and retrieval

What is this called?

Cerebellum