KINS 4200 Exam 2 Neural Control

central nervous system

brain and spinal cord

peripheral nervous system

cranial and spinal nerves

somatic nervous system

somatic sensory fibers

somatic motor fibers

voluntary actions

autonomic nervous system

involuntary functions

visceral motor

visceral sensory

dorsal root

sensory root

ventral root

motor root

afferent neuron

carries sensory information to the CNS

convey sensory information into the CNS about stimuli

efferent neuron

carries motor information from the CNS to the muscle

soma

body of cell

execute nerve function

locations of somas

gray matter of spinal cord

ganglia

ganglia definition

bundles of cell bodies

dendrites

receives information from other neurons

axon

transmits action potentials to other neurons or muscle fibers through axon terminal

myeline sheath

an insulated shell (schwann cells) covering the axon

allows electrical impulses transmit quickly

node of ranvier

gap in between schwann cells

synapse

junction between neurons or muscle fibers

allows passing electrical/chemical signals

motor unit

group of muscle fibers + alpha motor neuron

innervation ratio

# of muscle fibers innervated by one neuron

small innervation ratio

fine motor control

ex. eye muscle

large innervation ratio

gross motor control

ex. leg muscle

motor unit size

larger unit = more force

# of motor units recruited

more motor units = more force

size principle

order of motor unit activation

smaller —> larger

size principle smaller units

smaller motor units recruited faster but conduction speed is slow

slow twitch

activated first and remain activated due to fatigue resistance

fast twitch oxidative

activated second

fast twitch glycolytic

activated third and only briefly

firing rate

higher rate = greater force

electromyography (EMG)

measures voluntary muscle activity

measurement of action potentials

records sum of motor unit activity

fine wire/indwelling EMG

individual motor unit activity

invasive

difficult to apply

best used to record small, deep musculature

more stable recordings

surface EMG

overall muscle activity

comfortable

easy to apply

best used to record large superficial muscles

susceptible to movement artifacts

twitch

single action potential results in

electromechanical delay

time delay between muscle activation and force production

chemical events need to occur for contraction

eccentric reaches force at less biceps activity than concentric why?

eccentric muscles have passive tension not measured on EMG, so looks like eccentric isnt using as many motor units to produce the same amoung of force as concentric

factors that affect EMG signal

physiological cross talk of overlapping muscles

external noise

quality of electrode

motor unit firing rate

muscle fiber diameter

# of fibers

# of active motor units

distance of skin surface to msucle fiber

factors that affect how EMG is collected

resistance of skin

correct placement of EMG

correct placement of EMG

muscle belly, not the tendon

parallel to muscle fibers

limitations of EMG

EMG does NOT equal force production

cannot be directly used to make comparisons between subjects

corticospinal tract

direct pathway from the cortex to the spinal cord

right motor cortex controls what side of the body

the left side of the body

when does the control switch from right = left to right = right / cross midline

medulla, pyramidal decussation

premotor cortex

helps plan and coordinate movements

helps with sequencing and planing order of firing

primary motor cortex

controls individual movements or sequences of movements

create and initiate signal

cerebellum

fine tunes movement

helps get optimal signal down to the body

ataxia

abnormal movements appearing as lack of coordination

causes of ataxia

stroke, TBI, degenerative diseases

spinal cord 3 functions

1. send efferent signals from brain to the body

2. send afferent signals from the body to the brain

3. coordinates reflexes

reflexes

involuntary neural response to a sensory stimulus

unique because they don’t involve the brain

cutaneous mechanoreceptors

detect pressure

thermal receptors

detect temperature

nociceptors

detect pain

joint receptors

force in and around the joint

muscle spindles

monitor length and velocity of muscle stretch

location of muscle spindles

primarily in muscle belly

type Ia sensory endings

detect changes in muscle velocity and length

type II sensory endings

detect changes in muscle length

golgi tendon organs

monitors muscle tension (force)

location of golgi tendon organs

primarily on musculotendinous junction

type Ib afferent receptors

detect muscle tension

monosynaptic pathway

direct connection with motor neuron

polysynaptic pathway

connected through interneurons

stretch reflex steps

reflex hammer tap → tendon stretches → muscle stretches fast → muscle spindle detects fast stretch → increase firing rate of Ia afferent fiber in muscle spindle → increase firing rate of alpha motor neuron in muscle → same muscle contracts

agonist

muscle doing the work and motion

antagonist

one doing the opposite motion

antagonist vs agonist in knee flexion

antagonist: quadriceps

agonist: hamstrings

antagonist vs agonist in knee extension

antagonist: hamstrings

agonist: quadriceps

inverse stretch reflex steps

golgi tendon senses excessive tension/force → sensory neuron conducts action potential → sensory neurons synapse with interneurons → alpha motor neuron to quadriceps is inhibited with the alpha motor neuron to hamstring is stimulated → hamstring contracts and quads relax

ways inverse stretch reflex controls muscle tension

• inhibit agonist muscle

• excite/fire antagonist muscle

stretch reflex type

mono synaptic

inverse stretch reflex and flexion withdrawl (flexor) reflex type

poly synaptic

flexion-withdrawal (flexor) reflex

activated by painful stimulus

excites motor neurons that innervate flexors in affected limb

inhibits motor neurons that innervate extensors in affected limb

myotomes and dermatomes use

used for assessment if affected nerves after injury

myotome

muscle, motor neuron

muscle or group of muscle supplied by a spinal nerve

dermatome

skin, sensory neuron

area of the surface of the skin suppled by a spinal nerve

herniated disc mechanism of injury

constant abnormal stress leading to degeneration or injury from slip/fall/car accident

symptoms of herniated disc

sharp, radiating pain

numbness or tingling

weakness in musculature

how to test dermatomes

look at pain and numbness

sharp/soft test

how to test myotomes

test motor weakness and screening examination of strength