Neuro Lab 2

the motor neural pathway has upper motor neuron synapsing to

lower motor neuron

parts that make up the motor nervous system include:

motor planning areas (cortex), control circuits (cerebellum, basal nuclei), motor tract, spinal interneurons, lower motor neurons, skeletal muscles

premotor cortex:

plans, organizes, and coordinates groups of muscles to work together. plans how to move based on sensory feedback

supplementary motor cortex:

movement coordination particularly both sides of the body

Primary motor cortex:

carries out the complex movements and is located in the posterior region of the frontal lobe within the precentral gyrus

control circuts consist of:

cerebellum, basal nuclei

cerebellum provides for smooth coordinated movement by

processing info from the motor cortex, proprioception, and other sensory inputs

Basal nuclei can influence motor movements made by

the primary motor cortex: also helps start, stop, and control the intensity of movements; helps influence balance and gait.

Motor tracts deliver movement information from

primary motor cortex to lower motor neurons in the spinal cord or brain stem

there are three types of descending motor tracts

1. Postural/gross movement tracts

2. fine movement and limb flexion tracts

3. nonspecific UMN tract

Postural/gross movement tracts

control skeletal muscle activity (unconscious or involuntary)

fine movement and limb flexion tracts

controls limbs and face movements

nonspecific UMN tract

facilitates all LMNs

spinal interneurons:

some descending pathways connect to a connector neuron before synapsing with LMNs

lower motor neurons (LMNs)

directly innervates the effector (skeletal muscle fibers)

There are two types of LMNs:

Alpha motor neurons and Gamma motor neurons

Alpha motor neurons

have large cell bodies and large myelinated axons. Axons of alpha motor neurons project to extrafusal skeletal muscle

Gamma motor neuron:

have medium sized myelinated axons.Axons of gamma motor neurons project to intrafusal fibers in the muscle fibers

skeletal muscles (effectors)

composed of proteins like actin and myosin

Upper motor neurons (UMN) arise directly from the

cerebral cortex or arise within the brainstem

The UMNs axon travel in descending tracts to synapse with

LMN or interneurons in the brainstem or spinal cord.

UMNs are classified into 3 types according to whether they synapse

medially, laterally, or throughout the ventral horn

medial UMNs signal LMNs that innervate

postural and trunk muscles.

Four tracts arise from the brain stem and are involuntary and one arises directly from the cerebral cortex and is voluntary

1. Tectospinal tract

2. medial vestibulospinal tract

3. lateral vestibulospinal tract

4. medial reticulospinal tract

5. medial (anterior) corticospinal tract

tectospinal tract

this tract arises in the superior colliculus section of the tectum (posterior midbrain), crosses the midline and synapses in the cervical region of the spinal cord

medial vestibulospinal tract

This tract arises from the medial vestibular nucleus in the upper medulla, crosses midline and projects bilaterally and synapses in the cervical region of the spinal cord

lateral vestibulospinal tract

this tract arises from the lateral vestibular nucleus in the upper medulla, projects ipsilateally and synapses in the cervical and lumbar regions of the spinal cord.

medial reticulospinal tract

this tract begins in the pontine reticular formation, travels ipsilaterally and synapses in the cervical and limbar spinal cord regions

medial (anterior) corticospinal tract

this pathway is the direct connection from the cerebral cortex to the spinal cord and travels ipsilaterally; synapse in the cervical spinal region.

stimulates muscles, coordinates movements of the head and neck toward visual and auditory stimuli

tectospinal tract

stimulates LMNs innervating head, neck, and upper back muscles. Helps maintain balance during standing and moving.

Medial vestibulospinal tract

facilitates stimulation of LMNs to extensors and inhibits LMNs to flexors

lateral vestibulospinal tract

neural activity stimulates postural, trunk muscles (muscle tone) and stimulates proximal limb extensors

medial reticulospinal tract

voluntary pathway conveys information to LMNs that consciously controls head movemnets

Medial (anterior) corticospinal tracts.

Upper motor neuron disorders

Paresis or paralysis

causes of paresis or paralysis

spinal cord injury, cerebral palsy, ms, trauma or stroke

Paresis

partial loss of voluntary muscle contraction due to UMN lesion

paralysis

complete loss of voluntary muscle contraction

three types of paralysis

Hemiplegia, Paraplegia, Tetraplegia/quadriplegia

hemiplegia

loss affecting one side of the body; usually brain injury

paraplegia

loss affects the body below the arms: usually spine below T1

tetraplegia/quadriplegia

loss affects all four limbs; spinal damage, cervial region

Lower motor neuron disorders

atrophy, flaccid paralysis, abnormal reflexes

causes of LMN disorders

trauma, poliovirus, degenerative or vascular disorders and tumors can damade LMNs

Atrophy

loss of muscle bulk. two types: disuse- results from lack of muscle use and Neurogenic- results from damage to the LMNs

Flaccid paralysis:

weakness or loss of muscle tone (stiffness or resistance to stretch or limp and cannot contract. caused by infections or inflamations

Abnormal reflexes

abnormal cutaneous reflexes, Babinskis sign, clonus

abnormal cutaneous reflexes

changes in cutaneous reflec in respnse to normally innocuous stimuli, can be due to spinal cord injury with testing of flexors

Babinskis sign reflex

Extension of great toe, often accompanied by fanning of the other toes. It occurs onlu in people with corticospinal tract lesions or infants less than 7months

clonus reflex

involuntary, repeating, rhythmic muscle contractions

Tract

A bundle of axons traveling together in the CNS

Nerve

A bundle of axons traveling together in the PNS

Nucleus

A cluster of neuron cell bodies in the CNS

Ganglion

A cluster of neuron cell bodies in the PNS

Structure of a peripheral nerve

nerve fiber, Fascicle, Endoneurium, perineurium, Epineurium

nerve fiber

myelinated or unmyelinated axonpresent in a nerve

fascicle

a bundle of nerve fibers/axons

endoneurium

connective tissue layer that surrounds a single nerve fiber

perineurium

connective tissue layer that surrounds a fascicle

epineurium

connective tissue layer that surrounds an entire nerve trunk

know this

Cranial nerves I-IV

Cranial nerve V-VIII

Cranial nerve IX through XII

Cranial nerve numbers and pairs mneumonics

Oh, Once One Takes The Anatomy Final Very Good Vacations Are Heavenly ( I Olfactory, II Optic, III Oculomotor, IV Trochlear, V Trigeminal, VI Abducens, VII Facial, VII Vestibulocochlear, IX Glossopharyngeal, X vagus, XI Accessory, XII Hypoglossal

Cranial nerve Classification Mneumonics

Some Say Marry Money But My Brother Says Beautiful Blondes Marry Money

(sensory, Motor, Both. in the order of cranial nerves)

I Olfactory connection to the brain and function

Inferior frontal lobe and sense of smell/ ability to detect odors

II optic connection to the brain and function

diencephalon and sense of vision: the ability to see

III Oculomotor connection to the brain and function

anterior midbrain and moves each eye up and down, constricts pupils, elevates upper eyelid

IV Trochlear connection to the brain and function

posterior midbrain and moves eye medially and down

V Trigeminal connection to the brain and function

Lateral pons and blink reflex, chewing

VI Abducens connection to the brain and function

between pons - medulla and moves eye laterally

VII facial connection to the brain and function

between pons/medulla and blink reflex, facial expression, tear production

VII Vestibulocochlear connection to the brain and function

Between pons -medulla and sensation of head position relative to gravity and head movement

IX glossophanygeal connection to the brain and function

Medulla and sense of taste, gag reflex, salivation

X Vagus connection to the brain and function

Motor limb gag reflex, swallowing, speech production

XI Spinal Accessory connection to the brain and function

medulla and moves tounge

Disorder caused by damage to the olfactory nerve

Anosmia; inability to smell

Disorder caused by damage to the Optic

Ipsilateral blindness, loss of pupillary light reflex

Disorder caused by damage to the occulomotor

ptosis; drooping of eyelid and Diplopia; double vision

Disorder caused by damage to the trochlear

Diplopia; double vision, difficulty reading

Disorder caused by damage to the trigeminal

Trigeminal neuralgia; servere sharp/ stabbing pain to trigeminal nerve

Disorder caused by damage to the abducens

Diplopia; double vision ab

Disorder caused by damage to the facial

bells palsy; paralusis or paresis of muscles

Disorder caused by damage to the vestibulocochlear

conductive deafness and sensorineural deafness

Disorder caused by damage to the glossopharyngeal

interrupts gag reflex and swallowing reflex

Disorder caused by damage to the vagus

interrupts gag reflex and swallowing reflex, trouble speaking

Disorder caused by damage to the spinal accessory

paralysis of ipsilateral sternocleidomastoid and trapezius

Disorder caused by damage to the hypoglossal

difficulty speaking and swallowing, atrophy of tounge

sheep brain know

Somatosensory system

complex system of sensory neurons and pathways that respond to changes at the surface of the skin

the somatosensory part of the NS process sensory info and consists of

sensory receptors, sensory neural pathways, parts of the brain involved in sensory perception

Types of somatosensation

touch, pain, temp, proprioception

stages of somatosensation

activation of sensory receptors by stimuli, Receptor responds to stimuli by conversion of a sensory signal to an electrical signal, the electrical signal is carried to the brain and processed in specialized region of the brain

Types of somatosensory receptors

mecanoreceptors, chemoreceptors, thermoreceptros, nociceptors

mechaoreceptors

respond to mechanical deformities/ forces (touch pressure, vibration, stretch, hearing)

chemoreceptors:

respond to chemical changes in the cellular environment, including cell death. (taste, smell, blood composition)

Thermoreceptors

respond to changes in temp (hot, cold, warm)

Nociceptors

ability to respond to painful stimuli: a subset of each type of somatosensory receptors (respond when something may cause harm/ damage)

What affects conduction speed of info to the cerebrum

1. Myelinated fibers conduct info more quickly than unmyelinated fibers due to saltatory conduction

2. Axons with a large diameter conduct info faster than small-diameter axons

3. more connections or synapses along the path slow speed of conduction