Anatomy & Physiology Part 3 (Test 1) PNS

Which cranial nerves do not arise from the brainstem?

I- Olfactory

II- Optic

(associated with the brain)

Which cranial nerves are associated with the midbrain?

III-Oculomotor

IV- Trochlea

Which cranial nerves are associated with the pons?

V- Trigeminal

VI- Abducens

VII- Facial

VIII- Vestibulocochlear

Which cranial nerves are associated with the medulla?

IX- Glossopharyngeal

X- Vagus

XI- Accessory

XII- Hypoglossal

Efferent

motor

Afferent

sensory

General somatic efferent

motor to skeletal muscles

General somatic afferent

carries sensory from skin

General visceral efferent

motor to smooth muscles

General visceral afferent

carries sensory from smooth muscle

special somatic afferent

relays sensory from special sense areas

special visceral efferent

motor to glands in head and neck

special visceral afferent

relays special sense of smell and taste

Trigeminal (V)

- pons

- sensory functions: mucous membrane of the moth, deep pressure from the teeth, gum, hard palate, and TMJ

- Sensory from anterior 2/3 of tongue and floor of mouth - GSA; sends proprioception from muscles of mastication to brainstem; sends sensory from upper face, nose, mouth, lower jaw.

Motor functions of Trigeminal (V)

- innervates muscles of mastication, mylohyoid, anterior belly of the digastic, tensor tympani, and tensor veli palatine muscles.

Largest cranial; divides into branches: maxillary - provides sensory information

mandibular

Facial (VII)

- pons

- Sensory functions - submandibular, sublingual and lacrimal glands, taste receptors of anterior 2/3 of tongue and nasopharynx.

- Damage can paralyze side of the face (ipsilateral) impacting emotional and reflex movements. If atrophy occurs, there is facial asymmetry and fasciculations can occur.

Facial (VII) motor functions

facial expression upper & lower muscles and stapedius

Glossopharyngeal Nerve (IX)

- medulla

- Sensory - from pharynx (gag reflex and sensation) and some velum, posterior 1/3 of tongue, and Eustachian tube (middle ear)

- Damage often includes damage to the vagus and causes reduced gag reflex and pharyngeal sensation and motorically pharyngeal elevation.

Glossopharyngeal Nerve (IX) motor functions

to tongue, faucial pillars, stylopharyngeus and superior constrictor muscles; stylopharyngeus elevates the pharynx during swallowing and speech.

Vagus Nerve (X)

- medulla

- Sensory - from those above areas, external auditory meatus and taste receptors from the posterior pharynx, larynx, trachea; temperature from esophagus; taste from epiglottis

Vagus Nerve (X) motor function

to striated muscle of the soft palate, pharynx, esophagus, trachea, larynx

What nerve branches into three?

the vagus nerve (X)

The pharyngeal branch

innervates the pharynx at the middle pharyngeal constrictor muscle and joins with the glossopharyngeal and other laryngeal nerves to form the pharyngeal plexus. This branch innervates most pharyngeal and soft palate muscles but not stylopharyngeus and tensor veli. Supplies the palatoglossus. In general innervates muscles for pharyngeal constriction and soft palate retraction and elevation for VP closure.

Superior Laryngeal Branch

goes to the pharynx has two branches. The internal laryngeal nerve is sensory from the laryngeal lining to the vocal folds, epiglottis, base of tongue, aryepiglottic folds and dorsum of arytenoid cartilages. Transmits sensory information from the larynx.

The external laryngeal nerve innervates the inferior pharyngeal constrictor and the cricothyroid muscles which are important to phonation due to its effect on vocal folds (lengthen

Recurrent Laryngeal Branch

innervates all intrinsic muscles of the larynx except the cricothyroid. Sensory from vocal folds and all of laryngeal area.

Damage causes weakness of soft palate, pharynx and larynx. Unilateral damage can cause phonation, resonance, voice and swallowing problems. Bilateral damage has more implications.

Accessory Nerve (XI)

Has a cranial and spinal portion. Becomes part of the vagus' 3 branches. The cranial has motor to the uvula, levator veli and intrinsic laryngeal muscles. The spinal portion innervates the sternocleidomastoid and trapezius muscles.

Damage to to the Accessory Nerve (XI)

weaken head rotation

Hypoglossal Nerve (XII) motor function

intrinsic and all but one extrinsic (muscle of the tongue)

Hypoglossal Nerve (XII) sensory function

taste and tactile from nucleus of tractus solitaries and sensory trigeminal nucleus

Dorsal

sensory

Ventral

motor

Characteristics of a Neuron (Nerve Cell)

- How our body communicates

- Common denominator of our nervous system

- 85-100 billion neurons ranging in size and shape

- Neurons connect with other neurons and our muscle tissue

Transmit information via electrochemical process

o Electrical part is the neuron itself and its parts

o Chemical part is the neurotransmitter

Soma

Cell body: nucleus of the neuron, nutrients and mitochondria to maintain the neuron

Dendrite

Many of them, grey matter

Axon

associated with white matter

o Takes info from the soma to the next neuron dendrite

What does the Myelin Sheath do?

- Hold the neurotransmitter

- Increases the signal transmission

- Myelination

- protect the axons

What are the nodes of ranvier?

- Spaces between the axons

- Not wrapped in myelin

- Do participate in speed of transmission

What do neurotransmitters do?

excite or inhibit our activity

Types of Neurotransmitters?

- Play a part in neural development, plasticity and learning

- Dopamine (basal ganglia)

- Glutamate: excitatory central nervous system neuron

- Gaba: inhibitor neurotransmitter regulating muscle tone

- Acetylcholine: peripheral nervous system and is also and excitatory neurotransmitter contraction of muscle fibers

An axon has a what on it?

bouton

Within the bouton are what?

vesicles that hold the neurotransmitter

Unipolar

single process from soma; associated with sensory

Bipolar

more than one process [dendrite & soma] from soma; associated with special senses vision, hearing, smell

Multipolar

multiple projections [several dendrites & 1 axons]; associated with motor

Within the Central Nervous System

Tracts

Within the Peripheral Nervous System

Nerves

Sensory

- sending afferent information from our body to our brain

o Typically ascending

Motor

efferent and descending

Upper Motor Neuron

Cortex to brainstem

Lower Motor Neuron

brainstem to spinal cord

UMN and LMN

neuropathological concepts and are a way of explaining damage

What is the lower motor neuron a part of?

- Part of peripheral

- Part of the pathway from the brainstem to the face or neck muscles

- Or from the spinal cord to part of the body it is going to

Alpha motor neuron

What is it called when the UMN and LMN connect with one another?

Final common pathway

What motor neurons are pyramidal?

- corticospinal

- corticobulbar

Corticospinal

cortex to the spinal cord/nerves

Corticobulbar

cortex to the brainstem/cranial nerves

When a muscle is innervated it is called

motor fibers/extrafusal fibers

What are motor fibers/extrafusal fibers responsible for?

making the muscle contract

Where do these motor fibers come from?

the Lower Motor Neuron

What are muscle spindles?

- intrafusal fibers

- responsible for the proprioception or the accuracy of the contraction

What do gama motor neurons do?

send information back to the indirect system giving feedback on performance

Example of gama motor neurons system

Command from the motor strip comes through the UMN comes to the Spinal nerves and synapses go to the muscles that need to be contracted and then the muscle spindles provide information to the Gama motor neuron to send sensory information on performance and then signals sent if changes need to be made

When is the critical period for brain development?

3-16 weeks gestation

What does brain development begin with?

the neural plate

What is the neural plate made of?

cells and tissue

By 27 days what does the neural plate do?

the plate comes around and converges into a tube

After 27 days what does the neural tube do?

the tube expands and begins to transform into the central nervous system

---beginning with the lower systems: spinal cord and brain stem

What develops later in the growing CNS?

cortex and higher level functioning of the brain, may not reach maturity into adolescents or sometimes later

Myelination begins at?

14 weeks gestation

Are all of the needed functions there when born?

yes, higher order portions are just not completely developed

What are primitive reflexes?

rooting & sucking

- involuntary reflexes that a baby does

- help survive environment

- they should go away at about a year if not something may be wrong

Anomalies during embryonic brain development

- During neural tube 3-4 week, if it fails to close the child may have incomplete closure and part of the brain may not be present: anencephaly

- If the spinal cord does not close can cause spina bifida

What is brain development dependent on?

adequate nutrition which includes fetus- 2 years of age

- Without appropriate nutrition brain can be smaller and less efficient

---Medications, drugs, alcohol, infections: can all cause abnormalities

Characteristics of an adolescent brain?

-overproduction of cells/neurons

- thickening of cortex (grey matter)

When does the overproduction of neurons peak?

peaks at puberty for children 11 girls 12 boys

What occurs after the peak of overproduction?

pruning begins

How much weight increase of the brain in the first 2 years of life?

350%

How much weight increase for the next 10 years?

35%

By age 6 the child's brain is what percent of the adult size?

95%

What does it mean to have plasticity of the brain?

having the ability to learn a new skill

What changes occur in the adolescent brain?

1. Pruning of neurons starts to occur

a. Cells not used will be pruned

b. Reducing brain to normal volume

2. increase in weight of brain- age 6 (95% of the adult size)

3. plasticity to help learn new skills

What is the average lifespan?

75 years

What was the average lifespan in the early 1900s?

mid to late 40

What can occur in an aging brain?

proteins and tangles can cause issues

What are the characteristics of neuron in the aging brain?

neurons tend to be intact as we age, just don't fire as fast

Brain weight and volume begin to decrease by what?

5-10% between the age of 20-90

Does the surface of the brain begin to change?

yes

What happens to the gyri and fissures?

gyri not as large causing the fissures to become larger

What other things can effect the brain?

o Weight and brain aging

o Diabetes

o Hypertension and major stress

How do we prevent cognitive loss?

1. Education and stimulation of the brain

2. Exercise

3. Good rest