Spinal reflex L11 Flashcards
Three types of movement
reflex
voluntary
Rhythmic
Most movements are a combination of (except v simple movements);
reflex
voluntary
rhythmic
cerebral hemispheres are involved in
voluntary controls
modifying automatic movement
Cerebellum general role
coordinating movement
learning fine motor skills
Brainstem general role
automated type movements
Spinal cord movements
automatic or repetitive movements
grey matter in the spinal cord is
central
white matter in spinal cord is
on outside
Sensory neurons enter the spinal cord via the
dorsal horn
motor neurons exit the spinal cord via the
ventral horn
Cervical enlargement is between
C3-T1
Lumbar enlargement is between
L1-S3
trunk, head posture are organised ____ in the spinal cord
medially
upper limbs are organised____ in the spinal cord
medially
Hands, feet (distal) are organised_____ in the spinal cord
laterally
Which are the most motor neurons in the spinal cord
Alpha motor neurons
Largest neurons in the body=
alpha motor neurons
Where do alpha motor neurons synapse
skeletal muscle fibre
Upper motor neurons=
CNS
Lower motor neurons=
brain stem and spinal cord leave CNS synapse on muscles
Final common pathway=
LMN
Where are alpha motor neurons found
in the ventral horn of spinal cord
What neurotransmitters are associated with alpha motor neurons
Acetylcholine
Where can spinal motor neurons receive inputs from (3)
spinal interneurons
Muscle spindle and skin (sensory input)
UMN
Motor neuron disease also called
ALS
What goes wrong in ALS
degernation of alpha motor neurons (upper and lower)
Symptoms of ALS (4)
Muscle weakness
Atrophy
Twitching
Difficulty breathing/ swallowing
Drug treatment for ALS
Riluzole
what does Riluzole do
blocks glutamatergic neurotransmission
Reflex=
involuntary movement bc of sensory stimulation (impulses travel through reflex arc)
Reflex arc composed of
Sensory neuron
Interneuron (0-many)
Motor neuron
Why are reflexes so fast
Not many synapses
Why have reflexes
Protects the body against damage
Coordinates muscle activity
Stretch reflex=
myotatic reflex
Mitotic reflex caused
when a muscle is pulled on (it tends to pull back)
Where are muscle spindles are embedded in
extrafusal muscle
Muslce spindles are important for
proprioception
What is a muscle spindle made off
intrafusal muscle fibres
Which way do intrafusal muscle fibres run
in parallel with extrafusal fibres
What do intrafusal muscle fibres detect
amount and rate of change of muscle length (how stretched)
1a afferent neuron is
a sensory neuron
Where are 1a neurons wrapped
around the muscle spindle
Where do 1a neurons synapse
directly onto alpha motor neurons in the spinal cord
An alpha motor neuron signals the muscle to
contract
Where do Alpha motor neurons synapse
on extrafusal muscle fibres
What is a single synapse system
sensory fibres connected directly to the motor fibres
Monosynaptic=
single synapse between muscle sensory fibre and alpha motor neuron
Example of monosynaptic reflex
stretch reflex
What do gamma motor neurons do
regulates sensitivity of sensory afferents to stretch
Where do gamma motor neurons synapse
intrafusal muscle fibres
Which are thicker alpha or gamma motor neurons
Alpha
E.g of stretch reflex
patellar tendon tap
What type of response is a stretch reflex
graded
Arm flexors=
Biceps
Arm extensors=
triceps
The two actions of the patellar reflex
monosynaptic stretch reflex
reciprocal inhibition 9of antagonist)
What does the inverse stretch reflex involve
golgi tendon
Location of golgi tendon
junction of muscle and tendon
Which way does the golgi tendon run
in series with extrafusal fibres
what is the golgi tendon organ innervated by
1b afferent
What threshold are 1b afferents
high threshold (only innervated under extreme stretch0
What does muscle contraction do in the Golgi tendon
stretches the tendon and activates sensory receptors
What is the function of the Golgi tendon
Encodes and regulates muscle tension (protects muscles and tendons from damage)
1b afferents from the golgi tendon organ synapse with
inhibitory interneurons in spinal cord
Activation of 1b afferents decreases
activity of alpha motor neurons
Flexor withdrawal reflex or
crossed extensor reflex
receptors of flexor withdrawal reflex
nociceptive cutaneous receptors
Flexor withdrawal reflex=
bend one knee, extend opposite (compensatory support)
Flexor withdrawal reflex involves
multiple synapses
What are central pattern generators
neural networks that produce oscillatory patterned outputs without sensory input
Examples of central pattern generators
locomotion
chewing
swallowing
ect
