SPCH 311: Test 3

How is the brain externally organized?

Medulla

pons

Midbrain

Cranial Nerves

What is the medulla?

a. One-inch-long structure

b. Cranial nerve 12(hypoglossal nerve) is housed at the lower boundary of the medulla and the upper boundary of the medulla is the foramen cecum which marks the boundary between the medulla and the pons

c. 80% of the nerve fibers cross at the level of the medulla

d. Controls life functions such as

i. Respiration functions

ii. Swallow functions

iii. Cardiac functions

e. Coughing and vomiting are reflexes that are mediated here

What is the pons?

a. One inch long

b. Lies anterior to the cerebellum(Mini brain at back)

c. Attached to the cerebellum through cerebellar peduncles

d. Acts as a bridge to relay neural fibers between the cerebrum, cerebellum, and the lower structures(medulla and spinal cord)

e. Nuclei in the pons help with

i. Respiration

ii. Swallowing

iii. Hearing

iv. Eye movements

v. Facial expression

vi. General sensation

f. A number of cranial nerve nuclei are in the pons

What is the midbrain?

a. Inferior to the diencephalon

b. Superior to the pons

c. The anterior(front) of the midbrain consists of 2 cerebral peduncles

d. The front of the peduncle is called the crus cerebri and the back of the peduncle is called tegmentum

e. Between these two is a layer of dark grey matter called the substantia nigra

i. Dopamine is produced here

f. The back part of the midbrain is called the tectum which contains the paired inferior and superior colliculi

i. This is the auditory center of the midbrain

ii. Responsible for our startle response to loud noises and turning our head/eyes to the source of the sound

iii. May play a role in PTSD

List and Explain the 7 Cranial Nerves.

a. CN V(5)

i. Trigeminal nerve

ii. 3 branches

1. Ophthalmic

2. Maxillary

3. Mandibular

iii. Originates in the pons then branches into the 3

iv. Motor wise: responsible for the opening/closing movements of the jaw

v. Sensory: sensation of face, nose, mouth, scalp, jaw, anterior 2/3 of tongue, mucous membranes of the mouth, reads proprioceptive information from the muscles of chewing to the brainstem

b. CN VII(7)

i. Facial nerve

ii. Both motor and sensory(mixed nerve)

iii. Motor portion: relevant to speech production

1. Has 2 branches

a. Intracranial

b. Extracranial: innervates facial muscles for speech production

iv. Sensory portion: responsible for taste on the anterior 2/3 of the tongue

c. CN VIII(8)

i. Vestibulocochlear nerve(auditory nerve)

ii. 2 branches

1. Cochlear

2. vestibular

d. CN IX(9)

i. Glossopharyngeal

ii. Motor and sensory

iii. Motor portion: elevates pharynx and larynx (important for phonation)

iv. Nerve also mediates the gag reflex

v. Sensory portion: relays sensory info from the eustachian tube, pharynx, and tongue back to the brainstem and to the sensory cortex in the brain. This sensory info provides important feedback for motor function of the structure.

e. CN X(10)

i. Vagus

ii. Both motor and sensory

iii. 3 branches that originate in the medulla

iv. Controls pharyngeal constriction and palatal elevation

v. Velopharyngeal incompetence occurs when palate and cavity don't close correctly?

f. CN XI(11)

i. Spinal accessory

ii. Motor

1. 2 portions control head neck and shoulders

iii. Spinal portion: controls muscles of the neck to control neck and shoulders

iv. Cranial portion:

g. CN XII(12)

i. Hypoglossal

ii. Originates from the lower part of the medulla and controls all muscles of tongue (crucial for swallowing)

Separating Cranial Nerves for further study -->

What is CN V, where does it originate, and what is its function?

i. Trigeminal nerve

ii. 3 branches

1. Ophthalmic

2. Maxillary

3. Mandibular

iii. Originates in the pons then branches into the 3

iv. Motor wise: responsible for the opening/closing movements of the jaw

v. Sensory: sensation of face, nose, mouth, scalp, jaw, anterior 2/3 of tongue, mucous membranes of the mouth, reads proprioceptive information from the muscles of chewing to the brainstem

What is CN VII, where does it originate, and what is its function?

i. Facial nerve

ii. Both motor and sensory(mixed nerve)

iii. Motor portion: relevant to speech production

1. Has 2 branches

a. Intracranial

b. Extracranial: innervates facial muscles for speech production

iv. Sensory portion: responsible for taste on the anterior 2/3 of the tongue

What is CN VIII, where does it originate, and what is its function?

i.Vestibulocochlear nerve(auditory nerve)

ii. 2 branches

1. Cochlear

2. vestibular

What is CN IX, where does it originate, and what is its function?

i. Glossopharyngeal

ii. Motor and sensory

iii. Motor portion: elevates pharynx and larynx (important for phonation)

iv. Nerve also mediates the gag reflex

v. Sensory portion: relays sensory info from the eustachian tube, pharynx, and tongue back to the brainstem and to the sensory cortex in the brain. This sensory info provides important feedback for motor function of the structure.

What is CN X, where does it originate, and what is its function?

i. Vagus

ii. Both motor and sensory

iii. 3 branches that originate in the medulla

iv. Controls pharyngeal constriction and palatal elevation

v. Velopharyngeal incompetence occurs when palate and cavity don't close correctly?

What is CN XI, where does it originate, and what is its function?

i. Spinal accessory

ii. Motor

1. 2 portions control head neck and shoulders

iii. Spinal portion: controls muscles of the neck to control neck and shoulders

iv. Cranial portion:

What is CN XII, where does it originate, and what is its function?

i. Hypoglossal

ii. Originates from the lower part of the medulla and controls all muscles of tongue (crucial for swallowing)

What is the main cranial nerve for voice?

Vagus nerve (10)

How is the brainstem internally organized?

Tegmental regions

Nontegmental Regions

What are tegmental regions?

What makes up the tegmental regions?

a. Tegmentum is the core of brainstem which is continuous at each level of the brainstem

Tegmental areas include the following:

1.Reticular Formation

2. Inferior Olivary Nucleus

3.Red Nucleus

What is the Reticular formation?

a. The nuclei or the groups of specialized cells(cell bodies) of the RF are scattered throughout the tegmentum

b. These nuclei receive axon collaterals from the special senses and project axons throughout the brainstem, cerebellum, diencephalon, and the cerebral hemispheres

c. The circuitry of the RF inhibit, facilitate, modify, and regulate all cortical functions

d. The RF integrates internal thoughts, emotions, and cognition with sensory and motor stimuli

e. Responsible for consciousness, sleep/wake cycle, cardiovascular functions, and respiration

f. Partially responsible for homeostatic state of brain

g. Within the RF:

i. The complex multisynaptic ascending projections of the RF to the brain, thalamus, hypothalamus, and basal ganglia form the Reticular Activating System

ii. The RAS

1. Has controlling influence on levels of cortical arousal and consciousness

2. The level of alertness is correlated with the level of electro encephalic activity of the brain

3. While the cerebral hemisphere is sleeping the specialized nuclei in the brain stem turn on the metabolic repair systems

4. After body repair is completed and energy replenished the RF clock turns and awakens the brain

What is the inferior olivary nucleus?

a. A bulge on the medulla which receives axons from the cerebral cortex and sends the processed info to the cerebellum

What is the red nucleus?

a. A paired structure next to the substantia nigra

b. Receives projections(axons) from the cerebral cortex and in turn its axons make up the rubrospinal tract that descends the brainstem inputting into the ventral horn of the spinal cord. This modulates flexor tone in the upper extremities

c. Thought to be involved in babies preliminary crawling and arm swinging with walking

What are nontegmental regions and what are the 3 kinds?

(basic understanding not writeout)

Near the surface of the brainstem

1.Tectum

2.Cerebral Peduncles

3.Ventral Pons

What is the tectum?

a. Known as the rooftop of the midbrain

b. Has 2 little hills

i. Superior Colliculi: connected to vision

ii. Inferior Colliculi: involved with hearing as it projects axons to the auditory center in the thalamus which then projects to the auditory areas in the cerebral cortex

What are the cerebral peduncles?

a. Anterior portion known as the crus cerebri or bulges on the front side of the midbrain

b. Lateral corticospinal or corticobulbar tracts run through here

c. Lateral corticobulbar tract plays important role in speech production

d. Substantia Nigra also closely connects to the basal ganglia to play a role in speech production

What is the ventral pons?

a. Corticopontine fibers originate from the motor cortex and pass-through cerebral peduncles and input into the ventral pons nuclei

b. These projections then course/move to the cerebellum

c. Said to play role in movement error correction when learning new motor skills and also learning new languages

What is the cerebellum?

i. Known as mini brain

ii. Lies inferior to cerebral hemispheres and posterior to the pons

iii. On the outside:

1. Tightly packed folia with are composed of white matter overlayed with grey matter

a. This tightly packed folia allow for large amount of surface area

What makes of the anatomy of the cerebellum?

vermis

3 lobes

3 peduncles

What is the vermis?

Cerebellum is Divided into 2 hemispheres & separated by mound of tissue called the vermis at midline

It is also Divided into 3 lobes

What are the 3 lobes of the cerebellum?

· Anterior

· Posterior

· Flocculo-nodular

List and describe the 3 large peduncles that connect the cerebellum to the brainstem

· Inferior Peduncle

o Carry afferent info to the cerebellum

· Middle Peduncle

o Carry afferent info to the cerebellum

· Superior Peduncle

o Carries mostly motor info from the cerebellum to the brainstem, thalamus, motor cortex, and spinal cord

Describe the function of the cerebellum

a. Monitors sensory input from a variety of sources and integrates this feedback into motor movement

b. Coordinates but doesn't initiate movement

c. Through direct and indirect projections to the motor cortex, the basal ganglia, and the spinal cord, the cerebellum coordinates and modifies the tone, speed, and range of muscular excursions(movement) in the execution of motor function

d. The functions that the cerebellum monitors include:

i. Head and body position at rest

ii. Muscle tension

iii. Spinal cord activity

e. It participates in the planning, monitoring, and correction of motor movement using all of its collected sensory information

f. Through projections through the vestibular system, the cerebellum contributes to maintaining equilibrium

g. Also involved in the learning of new motor skills

h. Cerebellar control is ipsilateral as opposed to the cerebral cortex which is contralateral

What are the clinical signs of cerebellar dysfunction?

Three general characteristics:

1. signs and symptoms usually ipsilateral

2. deficits related to motor functions with no sensory loss or paralysis

3. gradual improvement unless cause is progressive degenerative type

List and describe the ways to test cerebellar function.

1. Finger-to-nose Method

a. Touching the finger to the nose

i. Your finger to your nose or your finger to examiners finger, to your nose, and back

b. Looking to see if there are accurate smoothly coordinated movements present

2. Diadochokinetic Movements

a. Persons ability to make rapid alternating movements(diadochokinesis)

b. Ex. /p,t,k/

c. Looking for uncoordinated sloppy movement that could point to cerebellar damage

3. Hopping

a. Hopping on one foot

b. Tests balance and equilibrium

4. Alternating Movements

a. Alternating movement of legs and arms while walking

b. Is it smooth?

5. Limb Rebounding

a. "im going to push hard on your arm, push against it, and when I let go hold it"

List and describe some common cerebellar impairments

1. Ataxia

a. Lack of order and coordination in motor activity

b. Coordinated motor activities become segmented

i. Ex. "drunk walk"

ii. Ex. While walking and turning, patient waits and then turns

2. Dysdiadochokinesia

a. Failure in the sequential progression of motor activities displayed by clumsiness in rapid and alternating movements

i. Test: finger tapping

3. Dysarthria

a. Commonly seen in bilateral cerebellar lesions

b. Impaired ability to make the needed changes in ongoing oral facial movement which can negatively affect speech production

c. With dysarthria speech is slow, slurred, and disjointed

i. Also called scanned verbal output: segmented movements

4. Dysmetria

a. Error in judgement of a movement's range or the distance from a target

i. Overshoots or undershoots the target

5. Intention Tremor

a. The impaired ability to reduce extra movements during skilled movement sequence

b. Often times, the closer they get to the target, the worse the tremor gets

i. Disappears during rest

6. Hypotonia

a. Not enough tone

b. Cerebellum functions to optimize motor tone of each muscle contributing to a movement

c. Normal muscle tone decreased

d. Muscles flaccid(floppy)

7. Rebounding

a. Impaired motor tone adjustment as well as a loss of rapid and precise corrective response

b. Patient loses the ability to predict, stop, or diminish movement

8. Disequilibrium

a. Walk like drunk

b. Impaired vestibular processing in the cerebellum

c. Their gait

What is the diencephalon?

a. Central core of the brain

b. Rests above midbrain of the brainstem

c. Includes the subcortical nuclear masses that form the central core of the brain

d. Aka: the between brain

i. Connects cerebral hemispheres to the rest of the body

What are the 4 parts of the diencephalon?

Thalamus

Subthalamus

hypothalamus

epithalamus

What is the anatomy and function of the thalamus?

1. sits on top of the midbrain

2. known as a sensory fiber relay station between the cerebral cortex and subcortical structures

3.Processes all special sensory information except for olfaction routing it to the cerebral cortex and other structures

4.Made up of small nuclei serving different functions projecting to different parts of the brain

5. Involved in motor function through directing some extrapyramidal fibers to the basal ganglia

What are disorders to the thalamus?

damage to this area produces contralateral somatic sensation

Ex. Burning, tingling, and a low pain threshold

1. Thalamic Aphasia

Language disorder

Fluent aphasia (speech might be disordered but it is fluid) is characterized by fluent like output and jargon-like speech. Repetition is minimally impaired

What is the anatomy, function, and damage of the subthalamus?

1. Anatomy and function

Lies below the thalamus

Contains a set of specialized cells called the subthalamic nuclei

Has a lot in common with the basal ganglia

Involved in: selection of actions and impulse control

2. Damage to the Subthalamus

When it is damaged: you see hemiballismus

This is an involuntary flinging of limbs

EX. OCD

Explain the anatomy, function and damage of the hypothalamus.

1. Anatomy and function

About the size of an almond and lies just under the anterior ventral surface of the thalamus

“linker and regulator”

Connects the nervous system to our endocrine system(hormonal system) which controls our hormones by way of the pituitary gland

4 primary functions:

Autonomic: controls autonomic nervous system

Endocrine: releases hormones into the blood system

Regulatory: involved in maintaining body temperature, blood volume, food/water intake, body mass, and reproduction, also helps with circadian rhythms

Drive and Emotion: has projections to the limbic system(emotional part of brain)

2. Damage here

Lack of regulation

What is the epithalamus?

1. Lies superior and posterior to the thalamus

2. Contains the pineal gland which produces melatonin which is involved in sleep wake cycles

3. Also contains habenula: a group of nuclei involved in olfactory reflexes(gag is example)

a. Also deals with stress responses and reward processing system

4. Contains the stria medullaris: white matter tract connecting the habenula to the limbic system

What is the anatomy and function of the Basal Ganglia?

a. Made up of 3 large nuclei that lie deep within the cerebral hemispheres

i. Caudate nucleus

ii. Globus Pallidus

iii. Putamen

b. Key components of the basal ganglia and the extrapyramidal system

c. Consists of 2 major pathways

i. Direct pathway: facilitates movement(helps make easier)

ii. Indirect pathway: inhibits or slows movement

d. Although the basal ganglia has many connections to the cerebral cortex, their connections to the cortical motor areas are most important

e. Using dopamine, the BG regulate motor functions and muscle tone, more specifically, the extrapyramidal functions such as: posture, balance, and arm swinging while walking

What occurs when the basal ganglia is damaged?

a. Results in increased muscle tone known as rigidity

b. Dyskinesias like tremors

c. Choreoathetosis: slow and voluntary movements(writhe or jerky)

d. Parkinsons: includes rigidity and stiffness

e. Huntingtons

f. Damage either by physical injury or loss of neurotransmitters results in disinhibition and the release of inappropriate behavior patterns(Tourette's)

g. Is suspected that damage to the BG can lead to variety of deficits including

i.Dysarthria(speech), dysphonia(voice), as well as comprehension, naming, and repetition problems

Explain what the internal capsule and corona radiata do and why they are important.

Medullary Centers

Bands of fibers

a. Internal Capsule

i. Subcortical band of fibers that contain all ascending fibers to the cerebral cortex and descending fibers projecting downward as they pass between the basal ganglia and thalamus

ii. The fibers bend in the area of the internal capsule called the genu. If this area is damaged it can affect the corticobulbar tract which is an important motor pathway which affects speech, and damage to area can also lead to hemiparesis(one sided weakness) or hemiplegia(one sided paralysis)

b. Corona radiata

i. Fibers between cortical surfaces and the thalamus create a fan shaped sheet of axons called the corona radiata

ii. Carries nearly all neuronal traffic to and from the cerebral cortex

iii. MS greatly negatively impacts/affects this area and can cause motor, cognitive, and psychiatric problems

Describe the anatomy of the ventricles of the brain.

a. The brain contains 4 ventricles (basically spaces in brain)

i. Right lateral ventricle

ii. Left lateral ventricle

iii. 3rd ventricle

iv. 4th ventricle

b. Lateral ventricles have 3 horns which are each located in a different lobe of the brain

i. Anterior horn is in the frontal lobe

ii. Posterior horn is in the parietal lobe

iii. Inferior horn is in the temporal lobe

iv. 3rd ventricle is located at midline in the diencephalon

1. 3rd Joins with 2 lateral ventricles by way of the interventricular foramen

v. 3rd ventricle narrows near midbrain to form the cerebral aqueduct which leads to the 4th ventricle

vi. 4th ventricle is located behind the pons and in front of the cerebellum

What is the function of the ventricles of the brain?

i. This ventricular system is continuous with the subarachnoid space(meaning it is uninterrupted)

ii. These ventricles are filled with CSF which is clear and colorless( csf found in spinal cord, ventricles, and subarachnoid space fo the meninges)

iii. Each ventricle contains the choroid plexus which produces CSF at a rate of 400-500 mL per day

b. CSF

i. Moves between ventricles by way of interventricular foramen and the cerebral aqueduct

ii. Replenished about every 7 hours

iii. Old CSF is absorbed into the venous system and thereby enters the blood stream

1. This is done through the arachnoid villi which are small protrusions of the arachnoid layer which protrude the dura mater into the venous sinuses of the brain allowing the csf to exit the subarachnoid space into the blood stream

c. 4 functions of the CSF

i. Protects brain tissue by acting as a shock absorbing water cushion

ii. Lightens the weight of the brain through buoyance

iii. Reduces waste by removing metabolic waste from the nervous system

iv. Helps transport nutrients and hormones throughout the body

What are the 4 functions of the CSF?

i. Protects brain tissue by acting as a shock absorbing water cushion

ii. Lightens the weight of the brain through buoyance

iii. Reduces waste by removing metabolic waste from the nervous system

iv. Helps transport nutrients and hormones throughout the body

What are some disorders of the ventricles? List and describe.

1. Obstructive hydrocephalus

a. This involves a narrowing of the passageways that connect the ventricles which leads to CSF build up because it can't move freely through system

2. Non-obstructive hydrocephalus

a. Involves a problem in the absorption and sometimes the production of the CSF which causes the ventricles to swell

3. Random facts:

a. Hydrocephalus can be congenital and can begin in the embryonic stages

b. Can also be acquired through TBI, meningitis, or a tumor

c. Why is this so serious?

i. The danger is the build up of intracranial pressure which can cause brain damage or even death

d. Treatment is provided through surgically inserted shunts which act as drainage pipes for the nervous system and csf

e. Risky to put shunt in due to bleeding and infection

END OF TEST INFO(CH 9 following)

What is the cerebrum?

also rando intro info

a. The brain weighs approximately 3 pounds and comprises about 2% of your body weight

b. It is large in comparison to your body

c. Current research shows total number of neurons in the brain is the reason humans have superior cognitive skills over other creatures

d. The surface of the brain is called the cerebral cortex and it is made of neuronal cell bodies(grey) underneath is the white matter that consists of neuronal axons

What parts of the cerebrum help with protection and nourishment?

The meninges

The blood-brain barrier

Cerebral Arteries

Waste Removal

What are the meninges?

a. Just as our skull(hard bony layer under scalp) protects brain tissues from outer forces, the meninges, add and added layer to protect brain

b. Going from outside in: scalp, scull, dura mater,arachnoid mater, subarachnoid space(filled with blood vessels and CSF), pia mater(innermost layer adhering to the gyri and sulci)

c. Brain floats on this watery CSF cushion

blood vessels that run on surface of brain are located on top of the pia mater in the subarachnoid space

What is the blood-brain barrier?

a. In most parts of body, almost all molecules can pass through the capillary walls into the extracellular space of the adjacent tissues, but NOT in the brain

b. Here, the cells of and surrounding the capillaries form selective blood-brain barrier

i. This barrier prevents most pathogens including most bacteria and viruses from leaving the blood stream and entering brain

c. Also limits or eliminates the effects of many drugs on the brain(not permeable to a lot of things)

i. Hallucinogens seem to be the exception to this rule

d. In fetuses the blood brain barrier isn't fully developed(brain so susceptible to drugs and alcohol)

e. The body's way around the blood brain barrier is in the circumventricular organs(CVO)

i. CVOs link the CNS, vascular system, and the endocrine system creating an alternative route for neuropeptides and hormones

What are the cerebral arteries?

a. The brain consumes approximately 20% of oxygen in the body

b. Oxygen nourishes the brain and without it the brain begins to die

c. Only a few minutes wihtough blood flow to the brain, can result in brain damage

d. Due to this great need for oxygen, the brain has a rich blood supply

e. Oxygen enters the brain through 2 arterial systems

1. Internal carotid arteries

2. Vertebral arteries

f. Arteries bring oxygenated blood from the heart to the brain and the veins carry deoxygenated from the brain back to the heart