FR lecture 12 - brain: brainstem and cerebellum

Brainstem

Made up of 3 main components: medulla oblongata, pons, and midbrain

Medulla oblongata

Most inferior portion of the brain; connects the brain to the spinal cord

Pons

Enlarged region of the brainstem with a bulge on the anterior side; located superior to the medulla oblongata; means “bridge”

Midbrain

Most superior portion of the brainstem; sits between the pons and the diencephalon

how does spinal cord gray matter relate to the medulla oblongata?

Spinal cord has gray matter in an H or butterfly shape on the inside; as it moves into the medulla oblongata, this pattern starts to change

C1 spinal nerve

First spinal nerve encountered when entering the spinal cord; last spinal nerve when moving upward toward the brain

Pyramids

White matter bulges on the interior side of the medulla oblongata; contain descending motor tracts that are part of the somatic motor system

Descending tracts

Carry information from the brain down toward the spinal cord

Pyramids function

carry electrical signals being sent from brain → skeletal muscles down to the spinal cord so they can be sent out to the periphery

Pyramids and skeletal muscle control

Contain motor tracts involved in conscious control of skeletal muscle; only descending; part of the somatic nervous system

the pyramids are ______ structures

Bilateral structures

Decussation of the pyramids

Area where the pyramids cross over to the opposite side of the body just before entering the spinal cord

what % of the tracts of the pyramids cross over to left/right?

90% of the tracts cross from the left side to the right and from the right side to the left

Decussation of the pyramids and brain damage

Damage to the right hemisphere or right side of the brainstem can affect muscles on the left side of the body because motor neurons controlling skeletal muscle cross over

Stroke and decussation of the pyramids

Which side of the brain has been affected can often be identified by which muscles are affected because motor control occurs on the opposite side

Olives

Bilateral concentrations of nuclei in the medulla oblongata

Inferior olivary nucleus

Nuclear region within an olive

Olives (medulla oblongata) function

Relay information about position of muscles and joints to the cerebellum

Information from the body travels through the _____ ____ synapses at the _____, and is then redirected to the _______ so it can help smooth out motor movements

spinal cord, olives, cerebellum

the _____ are a region involved in sound perception; they help perceive sounds by slightly altering how information is received from the inner ear

olives

Nucleus

Collection of cell bodies in the central nervous system

Hypoglossal nerve # and where it exits

Cranial nerve XII; exits the medulla oblongata

Hypoglossal nucleus + where its located

Region in the medulla oblongata where the cell bodies of the hypoglossal nerve are located

Cranial nerve structure

neuron cell bodies are located in nuclei within the medulla oblongata; axons exit the medulla oblongata and join with other axons to form the nerve

Vagus nerve

Cranial nerve X; exits the medulla oblongata; has a nuclei region in the medulla oblongata

Medulla oblongata function

Transmits both ascending and descending impulses between the brain and spinal cord

Medulla oblongata white matter contains

• pyramids with descending somatic motor neurons

Medulla oblongata vital reflexes

Contains centers for vital reflexes important for keeping the body alive

Cardiovascular control center

Located in the medulla oblongata; controls heart rate and blood pressure

Respiratory control center

Located in the medulla oblongata; controls respiration or breathing

Medulla oblongata reflexes

Reflexes involved in swallowing, coughing, and sneezing

Medulla oblongata and airway

Swallowing, coughing, and sneezing reflexes help keep the airway clear

Medulla oblongata and cardiovascular system

Cardiovascular control center helps keep the cardiovascular system functioning properly

Medulla oblongata and breathing

Respiratory control center helps keep breathing rate going

ignore

ignore

which cranial nerves have nuclei in the medulla oblongata?

V, VII, IX, X, XI, and XII

5, 7, 9, 10, 11, 12

Pons

Located just superior to the medulla oblongata; the word means “bridge”

Pons function

Acts as a connection between different areas of the brain

Does the pons contain only descending, ascending or both nerve tracts?

both

Pons ascending tracts

Carry information from the spinal cord up toward the cerebrum

Pons descending tracts

Carry information from the cerebrum down through the spinal cord

Pons gray matter

Contains several areas of gray matter that contain nuclei

the ____ contains a sleep center involved in the sleep-wake cycle

pons

Pons and REM sleep

Specifically involved in REM sleep, or rapid eye movement sleep

REM sleep

Phase of sleep where the eyes can be seen moving underneath the eyelids

the ____ works with the medulla oblongata to control respiration

pons

Pontine nuclei

Nuclear region in the anterior portion of the pons

Pontine nuclei function

Involved in communication between the cerebrum and cerebellum

Pontine nuclei and cerebrum/cerebellum communication

Gathers information from the cerebellum and brings it up to the cerebrum or vice versa; area where neurons synapse between the cerebrum and cerebellum

which cranial nerves have their nuclei in the pons?

V, VI, VII, and VIII

5, 6, 7, 8

Cranial nerve V nuclei located where

both the medulla oblongata and pons

Midbrain

Most superior portion of the brainstem; sits between the pons and diencephalon

Midbrain white matter contains what

Contains nerve tracts carrying sensory information upward and motor information downward

Midbrain gray matter

Contains nuclei

Sensory information traveling from the spinal cord toward the cerebrum travels through the ______

midbrain

Motor information traveling from the cerebrum downward travels through the ______

midbrain

the ______ provides a connection to the thalamus, which is the relay center for sensory information

midbrain

Thalamus

Part of the diencephalon; receives most sensory input

Midbrain reflex centers

Contains visual and auditory reflex centers

which cranial nerves have their nuclei in the midbrain?

III, IV, and V

3, 4, 5

Neurons belonging to cranial nerve _ have cell bodies located in all _____ regions of the brainstem; their axons come together to form cranial nerve _

V, three, V

Tectum

Structure on the posterior portion of the midbrain formed by 4 nuclei

Colliculus

Individual mound of gray matter forming the tectum

Superior colliculi

Two nuclei located on the posterior surface of the midbrain; involved in visual reflexes

Inferior colliculi

Two nuclei located on the posterior surface of the midbrain; involved in auditory reflexes

Superior colliculi function

Visual reflex center; involved in visual movements

the ______ _______ in the midbrain controls reflex movements involving both extrinsic muscles of the eye and intrinsic muscles of the eye

superior colliculi

Extrinsic eye muscles

Muscles that move the eyeballs around in their sockets

Intrinsic eye muscles

Smooth muscles that change things such as pupil diameter

the ______ ______ in the midbrain gather visual, auditory, and touch information to help direct where the eyes need to move

superior colliculi

Superior colliculi and auditory information

Auditory information, such as hearing a loud noise, can direct the eyes to look toward where the sound came from

The ______ ______ is involved in tracking and scanning eye movements

superior colliculi

Inferior colliculi function

Auditory reflex center; involved in reflexes such as the startle reflex

Startle reflex

A loud noise can cause the body to jump and move toward the sound; some control is contained in the inferior colliculi

Inferior and superior colliculi relationship

A loud noise can send a signal to the superior colliculi to move the eyes while the inferior colliculi contributes to the body’s startle response

Cerebellar peduncles

• structures that come off the brainstem toward the cerebellum

• bundles of axons or white matter pathways carrying info from one area to another

Superior cerebellar peduncle

Carries axons to and from the midbrain to the cerebellum

Middle cerebellar peduncle

Carries information from the pons to the cerebellum

Inferior cerebellar peduncle

Carries nerve tracts from the medulla oblongata to the cerebellum

Cerebellar peduncles function

Connection points between the brainstem and cerebellum; white matter connections between the brainstem and cerebellum

Reticular formation

Group of nuclei scattered throughout the brainstem and connected to each other by white matter connections

the __________ _________ forms a cloud-like structure in the brainstem; often referred to as the “reticular cloud”

reticular formation

Reticular formation function

Partly controls the sleep-wake cycle

the _______ _______ maintains consciousness or brings a person into awakening from a sleep phase

reticular formation

the _________ _______ should be activated when a person is awake, such as while listening to a lecture

reticular formation

the ______ ______ is activated when waking up in the morning from a sleeping phase

reticular formation

Cerebellum

Second largest part of the brain

Cerebellum location

Attached to the brainstem on the posterior side

Cerebellum and brainstem attachment

Cerebellum attaches to the brainstem through the cerebellar peduncles

Cerebellar peduncles

nerve tracts connecting the brainstem and cerebellum

Cerebellar peduncles connections span to the

entire brain stem (midbrain, pons, and medulla oblongata)

Fourth ventricle is a space b/w the ___ and ________

pons and cerebellum

Arbor vitae

White matter regions inside the cerebellum; named because they resemble the trunk and branches of a tree

Arbor vitae composition

White matter made of myelinated axons

Arbor vitae function

gathers information from gray matter regions and brings it toward the brainstem via the cerebellar peduncles

Cerebellar cortex

Gray matter region surrounding the arbor vitae

Folia

Folds in the gray matter cortex of the cerebellum

Cerebellar folia appearance

Surface folds that look like ridges or grooves; on superior and inferior views they appear as long groups or folds

Cerebellar neurons

Cerebellum contains many neurons

Cerebellar hemispheres

Two hemispheres of the cerebellum; also called lateral hemispheres or cerebellar hemispheres