BBB CH 13: Spinal Control of Movement

Why are lower motor neurons referred to as the "final common pathway" for behavior control? A) They directly command muscle contraction. B) They are the input of the motor system. C) They integrate sensory and motor information. D) They constitute the largest of the four main output pathways of the somatosensory system.

A

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Varying the firing rate of AMNs What neurotransmitter is at neuromuscular junctions?

ACh

diseases associated with LMN

ALS

TYPES OF MUSCLES What type of fibers is smooth muscle innervated by?

ANS (autonomic NS)

Two categories of LMNs in the spinal cord

Alpha, gamma

SPINAL CORD ANATOMY contains somas of sensory afferents entering the cord

DRG (dorsal root ganglion)

three major sources of input for AMNs

DRG neurons, UMNs, interneurons

T/F: skeletal muscles are evenly distributed throughout the body

F

CONTRACTILE PROPERTIES OF MOTOR NEURONS T/F: When the different muscle units experience repeated APs over a longer time period, they fatigue at the same rate

F (show different rates of fatigue)

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Size principle Recruitment of motor neurons in the cat gastrocnemius muscle under different behavioral conditions. • ______ units are recruited for the most strenuous activities.

FF (fast fatiguable)

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Size principle Recruitment of motor neurons in the cat gastrocnemius muscle under different behavioral conditions. • __________ units provide the additional force needed for walking and running.

FR (fast fatigue-resistant)

Somatic muscles are innervated by what type of somatic motor neurons in the ventral horn of the spinal cord?

LMN

directly command muscle contraction

LMN

TYPES OF MOTOR UNITS S (slow)/ FR (Fatigue-resistant)/ FF (fast Fatigue) important for sustained muscle contraction

S

TYPES OF MOTOR UNITS S (slow)/ FR (Fatigue-resistant)/ FF (fast Fatigue) smallest to largest motor units

S, FR, FF

TYPES OF MOTOR UNITS S (slow)/ FR (Fatigue-resistant)/ FF (fast Fatigue) most to least resistant to fatigue

S, FR, FF

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Size principle Recruitment of motor neurons in the cat gastrocnemius muscle under different behavioral conditions. • ______ motor units provide the tension required for standing.

S/slow

MOTOR NEURONS IN THE SPINAL CORD T/F: LMNs are not evenly distributed throughout the body

T

What provides input to LMNs?

UMN

NEUROMUSCULAR MATCH MAKING crossed-innervation experiment muscle phenotype switch can occur by changing the ...

activity in the input MN

LMNs that innervate extrafusal muscle fibers

alpha

SOMATIC MUSCULATURE: TERMINOLOGY trunk movement -- position head and spinal column; move rib cage; 60% of skeletal muscles

axial (muscles)

SOMATIC MUSCULATURE: TERMINOLOGY three types of muscles that refer to the location of the joints they act upon

axial, proximal, distal

INPUTS TO ALPHA MOTOR NEURONS Are interneurons in the spinal cord excitatory or inhibitory for AMNs

both

controls motor programs in spinal cord

brain

TYPES OF MOTOR UNITS FF: _______ exertions that require _____ forces

brief, large

TYPES OF MUSCLES two types of striated muscle

cardiac (heart) , skeletal

Where are the soma of UMNs?

cerebral cortex, brainstem

ALPHA MOTOR NEURONS Muscle contraction is due to the...

combined action of motor units

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Varying the firing rate of AMNs What does sustained contraction require?

continuous stimulation

What kind of control do LMNs have?

direct

SOMATIC MUSCULATURE: TERMINOLOGY What type of muscles: hands, feet, digits (fingers and toes) movement

distal

SPINAL CORD ANATOMY sensory (somatic and visceral) afferents

dorsal root

LMNS IN VENTRAL HORN Where do motor neurons controlling flexors lie?

dorsal to extensors

INPUTS TO ALPHA MOTOR NEURONS when interneurons give inhibitory input, it causes a muscle to...

extend

the motoneurons of the brain and spinal cord, so called because they receive and integrate all motor signals from the brain to direct movement

final common pathway

INPUTS TO ALPHA MOTOR NEURONS when interneurons give excitatory input, it causes a muscle to...

flex

CONTRACTILE PROPERTIES OF MOTOR NEURONS Single AP triggers contraction strengths of differing _________ and _______ in each of the different motor units

force, time course

LMNs that innervate intrafusal muscle fibers

gamma

role of motor system

generation of coordinated movements

ALPHA MOTOR NEURONS trigger the ..... by muscles

generation of force

What condition can damage to UMNs cause?

hypertonia/spasticity (too much muscle toning)

What is ALS caused by?

inability to contract muscles (LMNs)

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Varying the firing rate of AMNs What effect does continuous stimulation have on APs?

increased number and frequency

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Size principle what changes the amount of force produced by a muscle?

increasing number of active motor units

INPUTS TO ALPHA MOTOR NEURONS UMNs in motor cortex and brain stem are important for...

initiation and control of voluntary movement

TYPES OF MOTOR UNITS FR: ______ motor units -- innervated by _______ alpha MNs

intermediate

INPUTS TO ALPHA MOTOR NEURONS what is the largest input?

interneurons (in the spinal cord)

TYPES OF MOTOR UNITS FF: ______ motor units -- innervated by _______ alpha MNs

large, large

• LMNs are not evenly distributed within the spinal cord • regions of the cord where innervation of the muscles of the arms and legs occur • Dorsal and ventral horns are "swollen"

limb enlargements

SOMATIC MUSCULATURE: TERMINOLOGY What are proximal muscles important for?

locomotion

ventral horn motor neurons, innervate skeletal muscles

lower motor (LMN)

SOMATIC MUSCULATURE: TERMINOLOGY What are axial muscles important for?

maintaining posture

SOMATIC MUSCULATURE: TERMINOLOGY What are distal muscles important for?

manipulation of objects

LMNS IN VENTRAL HORN Where do motor neurons controlling axial muscles lie?

medial to those controlling distal muscles

all alpha motor neurons that innervate a single muscle

motor neuron pool

muscles (skeletal) and neurons that control muscles

motor system

ALPHA MOTOR NEURONS one alpha motor neuron and all the muscle fibers it innervates - "The elementary unit of motor control"

motor unit

NEUROMUSCULAR MATCH MAKING crossed-innervation experiment When a slow AMN was rewired to innervate a fast muscle type, what occurred?

muscle phenotype switched to slow (same thing happened vice versa)

INPUTS TO ALPHA MOTOR NEURONS 1. DRG neurons with axons that innervate the...

muscle spindle

SOMATIC MUSCULATURE: TERMINOLOGY Flexors and extensors pull on the joint in ______ directions

opposite (antagonize ea other)

TYPES OF MOTOR UNITS FF: _____ muscle fibers

pale

SOMATIC MUSCULATURE: TERMINOLOGY What type of muscles: shoulder, elbow, pelvis, knee movement

proximal

What do muscles do to a joint?

pull

TYPES OF MOTOR UNITS S (slow): Type of muscle fiber

red

TYPES OF MUSCLE FIBERS red/white muscle fibers: better for marathon running

red

TYPES OF MUSCLE FIBERS red/white muscle fibers: rich in myoglobin

red

TYPES OF MUSCLE FIBERS red/white muscle fibers: slow to contract

red

TYPES OF MUSCLE FIBERS red/white muscle fibers: slow twitch

red

TYPES OF MUSCLE FIBERS Have a high myoglobin content Appear darker (dark meat in chicken legs and thighs) Contain more mitochondria Supplied by more blood capillaries

red muscle fibers

two types of muscle fibers

red, white

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) motor units are recruited from smaller to largest

size principle

motor units with larger and larger fibers are recruited as stimulus intensity increases

size principle

TYPES OF MUSCLES What type of muscle makes up the build of body muscle mass?

skeletal

What do alpha MNs excite?

skeletal muscles

TYPES OF MOTOR UNITS 3 types

slow (S) , Fast fatigue-resistant (FR) , Fast fatiguable (FF)

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Size principle do small or large motor neurons have a lower threshold for activation

small

TYPES OF MOTOR UNITS What are slow motor units (S) innervated by?

small alpha MNs

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Size principle Small motor units have ______ AMNs, large motor units have ______ AMNs

small, large

TYPES OF MOTOR UNITS S: ______ motor units -- innervated by _______ alpha MNs

small, small

TYPES OF MUSCLES Involuntary muscle found inside many internal organs of the body (digestive tract, arteries, viscera (organs))

smooth

TYPES OF MUSCLES digestive tract, arteries, viscera (organs)

smooth

TYPES OF MUSCLES two types

smooth, striated

coordinated movements are produced by _______ and _____ patterns of muscle contractions orchestrated by the brain and spinal cord

spatial, temporal

contains motor programs necessary for generating coordinated movements

spinal cord

SPINAL CORD ANATOMY mixed sensory and motor info

spinal nerves

NEUROMUSCULAR MATCH MAKING crossed-innervation experiment What was done to test if axons are matched with the appropriate muscle fibers or if the type of muscle (its phenotype - slow/fast) is determined by its type of innervation (AMN motor type)?

switched the nerve input (AMN type) that innervates muscles

SOMATIC MUSCULATURE: TERMINOLOGY relationship between flexors and extensors

synergistic/antagonistic

TYPES OF MOTOR UNITS FR (Fatigue-resistant) motor units generate ______ the force of S(slow) motor units

twice

CONTROL OF CONTRACTION BY ALPHA MOTOR NEURONS (AMNS) Varying the firing rate of AMNs What does a single AP in an AMN cause in muscle?

twitch

motor neurons in the central nervous system that control the lower motor neurons in the peripheral nervous system

upper motor (UMNs)

two mechanisms of Control of Contraction by Alpha Motor Neurons (AMNs)

varying the firing rate, size principle

SPINAL CORD ANATOMY motor (somatic and visceral) efferents

ventral root

MOTOR NEURONS IN THE SPINAL CORD What areas of the spinal cord are there "limb enlargements"

where innervation of the muscles of the arms and legs occur

TYPES OF MUSCLE FIBERS red/white muscle fibers: anaerobic metabolism

white

TYPES OF MUSCLE FIBERS red/white muscle fibers: better for sprints

white

TYPES OF MUSCLE FIBERS red/white muscle fibers: fast twitch

white

TYPES OF MUSCLE FIBERS red/white muscle fibers: fatigue rapidly

white

TYPES OF MUSCLE FIBERS red/white muscle fibers: sparse mitochondria

white

ALPHA MOTOR NEURONS innervate fibers over a ______ area

wide