Brain and Cranial NervesLearning Outcomes:1. Describe the major components of the brainstem (medulla oblongata, pons, midbrain, reticular formation). List the general functions of each.2. List the major regions of the cerebellum and describe the major functions of each.3. Name the four major components of the diencephalon.4. Describe the functions of the thalamus and hypothalamus.5. List the general functions of the epithalamus and subthalamus.6. Describe the structure of the cerebrum. Explain which structures are sep-arated by the longitudinal fissure and central sulcus.7. Name the five lobes of the cerebrum, and describe their locations and functions.8. List three categories of tracts in the cerebral medulla.9. Describe the general functions of the basal nuclei.10. Describe the functions of the limbic system.11. Describe the cranial meninges and contrast the structure of the cranial dura mater with the spinal dura mater.12. List the ventricles of the brain.13. Explain the function of the blood-brain barrier.***Review Table 13.1 for parts and brain and general functions***

Brainstem: Connects spinal cord to the remainder of brain; responsible for many vital functions; includes medulla oblongata, pons, midbrain, and retic-ular formation

Medulla Oblongata· communication between the brain and spinal cord

· autonomic nuclei include cardiovascular center (adjust HR), respira-tory rhythmicity center (adjust breathing rate)

· contains the nuclei of five cranial nerves

· contains tracts for both sensory and motor pathways (to and from the other parts of the brain)

· site of decussation (crossing over) of some neural pathways

· nucleus gracilis and nucleus cuneatus

o sensory nuclei

Pons “little bridge” · links cerebellum to brain stem and spinal cord

· respiratory center (allows you to breath)

· relay to and from the cerebellum

· contains four cranial nerve nuclei

Midbrain (mesencephalon)· Tectum (roof) : corpora quadrigemina are two pairs of sensory nuclei:

o superior colliculi visual reflexes in response to loud noises, flashing light or startling pain

o inferior colliculi receive auditory information from the ear; also conduct information to superior colliculi that stimulate visual re-flexes.

· Tegmentum (floor) : contains sensory tracts

o red nuclei : coordinates with cerebrum and cerebellum to control posture

· Substantia nigra : inhibits cerebral activity by secreting dopamine

· contains three cranial nerve nuclei

Reticular Formation:

· consists of nuclei scattered throughout the brain stem

· functions in cycles of activity (sleep-wake cycles)

Cerebellum· gray cortex and nuclei with white medulla in between

· cortex has ridges called folia

· white matter is called the arbor vitae

· consists of three parts

o flocculonodular lobe : controls balance and eye movement

o vermis :

o lateral hemispheres : involved in posture control, movement and motor coordination; communicates with cerebrum to regulate complex movements

Diencephalon: located between brain stem and cerebrum; includes the thal-amus, subthalamus, epithalamus and hypothalamus

Thalamus: relay between ascending sensory information and the cerebrum

• Examples of thalamic nuclei:· medial geniculate nucleus relays auditory input

· lateral geniculate nucleus relays visual input

· ventral posterior nucleus relay sensory information of pain, pres-sure, temperature, touch and taste

· anterior and medial nuclei: mood modification

Subthalamus: mainly involved in motor function

Epithalamus: includes the habenular nuclei (emotional and visceral re-sponses to odor) and pineal gland

Hypothalamus (review table 13.3; don’t worry about the nuclei, just study functions)

· emotional influences over body function; subconscious control of skeletal muscles associated with emotion

· autonomic functions (HR, BP, digestive tract movements, etc.)

· coordination between endocrine and nervous systems

· secretion of hormones: ADH and oxytocin

· regulates food and water intake

· regulates sexual development and behavior

· coordination between voluntary and autonomic functions

· regulates body temperature

Cerebrum: responsible for conscious thought and intellect

· Cerebral cortex : superficial layer of gray matter

· Divided into two hemispheres separated by longitudinal fissure

· Corpus collosum : connects the two hemispheres

· Each hemisphere in subdivided into lobes: frontal, parietal, temporal, occipital, and insula

· Central sulcus separates the primary motor cortex from the primary sensory cortex

Primary Motor Cortex· located in the frontal lobe

· directs voluntary movement

Primary Sensory Cortex· located in the parietal lobe

· receives sensory information of touch, pain, pressure, vibration, taste and temperature

Visual Cortex· located in the occipital lobe

· receives sensory information of sight

Auditory Cortex· located in the temporal lobe

· receives sensory information of sound

Olfactory Cortex· located in the temporal lobe

· receives sensory information of smell

Each hemisphere receives sensory information from and sends motor com-mands to the opposite side of the body.

Two hemispheres have different functions• Association areas of the Cerebrum:

· interpret incoming data or coordinate motor response, each cortex has its own association area

• Hemisphere specialization:

· Left hemisphere : categorical

· Right hemisphere : representational

Central White Matter of the Cerebrum:

· Association fibers : interconnect areas within the same hemisphere

· Commisural fibers : interconnect the two hemispheres

· Projection fibers : connect cerebrum with other parts of the brain

Basal Nuclei: functionally related nuclei located in the cerebrum, dien-cephalon, and midbrain; control motor function, subconscious control of muscle tone and coordination of learned movements

Limbic System: functional grouping including areas along the border be-tween the cerebrum and diencephalon

· establish emotional state and related behavioral drives

· linking conscious functions with unconscious functions

· memory storage and retrieval

Protection of the brain:

· bones of the cranium

· cranial meninges

· CSF

· blood-brain barrier

Cranial meninges: continuous with the spinal meninges, differences include the lack of an epidural space

· Cranial dura mater consists of two parts (periosteal and meningeal)

· Dural folds extend into brain fissures

· Dural venous sinuses are spaces that form between two dura mater layers, transport venous blood from the brain and cere-brospinal fluid

CSF provides cushioning and support for the brain, also transport of nutri-ents, chemical messengers and waste products

Blood-brain barrier prevents the movement of some substance in the blood into the interstitial fluids of the brain

Ventricles: fluid-filled cavities of the brain

· Lateral ventricles : in cerebral hemispheres

· Third ventricle : in diencephalon

· Fourth ventricle : in brainstem