Lecture 6 - Motor and Sensory Function Flashcards
Somatic Nervous system
- The somatic nervous system innervates the skeletal muscle (voluntary muscle)
- Somatic efferent nerve firing excites muscle activity
- Composed of somatic parts of the CNS and PNS
Autonomic nervous system
- The autonomic nervous system innervates smooth muscle (involuntary) in the intestines, sweat, and salivary glands, myocardium and some endocrine glands
- Functions as a unit to maintain constancy in the internal environment
Somatic sensory system
transmits sensations of touch, pain, temperature, and position from sensory receptors
Somatic motor system
Innervates only skeletal muscle, stimulating voluntary and reflexive movement by causing the muscle to contract, as occurs in response to touching a hot flame
Peripheral nerves
- A unique type of inert tissue in that they are not contractile tissue, but they are necessary for the normal functioning of voluntary muscle
- Can be sensory, motor, or mixed
What is muscular weakness
Lack of muscle strength as a result of morphological factors, physiological, metabolic factors, or a lesion or disease of the muscle, its tendons, or the bony insertion
What are the morphological factors of muscle weakness
- muscle cross-sectional area
- arrangement of muscle fibres
- fibre-type distribution
- fascicle length
- tendon stiffness
What are ways to test muscle strength
- Single rep max
- MMT
- Hand help dynamometers
- Modified sphygmomanometer
Motor impairment
Muscle weakness, if elicited, may be caused by:
- Upper motor neuron lesion
- A nerve root lesion
- Injury to a peripheral nerve
- Pathology at the neuromuscular junction
Myotomes
- groups of muscles that are predominantly supplied by a single nerve root
- A lesion of a single nerve root is usually associated with paresis of the myotome
Testing myotomes
- examiner should place the test joint(s) in a neutral or resting position and then apply a resisted isometric force
- The contraction should be held for at least 5 seconds and repeated 3 times to show if there is fatiguable weakness
- Positive findings indicate neurological impairment as opposed to muscle weakness
Upper motor neuron syndrome
- includes lesions involving the cortical spinal pathways
- Levels of involvement include: cortex, internal capsule, brainstem, and spinal cord
Lower motor neuron syndrome
Damage to the lower motor neuron cell bodies or their peripheral axons
Negative features for upper motor neuron syndrome
- weakness
- slowness or movement
- impaired coordination
Positive features for upper motor neuron syndrome
- spasticity
- hyperactive reflexes
- rigidity
- intentional tremors
- dystonia
Negative features for lower motor neuron syndrome
- paresis
- Hyporeflexia
- rapid atrophy
- fatigue
Positive features for lower motor neuron syndrome
- fasciculations (involuntary muscle contraction)
- spasms
Sensation
- Sensation is the conscious perception of basic sensory input
Sensibility
the neutral events occurring at the periphery nerve fibres. and nerve receptors
Anterior spinothalamic tract
- type A alpha and C fibre
- small diameter, unmyelinated
- Discriminative aspects including location and intensity
- Light touch and pressure
Anterior spinothalamic tract route
- Peripheral receptor
- enters the spinal cord
- synapses in the dorsal horn
- decussates (crosses) - can ascend a few levels prior to decussating
- travels up the spinothalamic tract (anterolateral pathway)
- synapses in the ventral posterior lateral nucleus ( thalamus)
- Terminates in tei primary somatosensory cortex
Dorsal column - medial lemniscal pathway
- type a alpha and a beta
- large diameter, myelinated
- proprioception, vibration and fine touch
Dorsal column - medial lemniscal pathway route
- peripheral receptor
- enters spinal cord and travels up the dorsal column
- synapses in the dorsal column nucleus (medulla)
- Decussates
- travels up the medial lemniscus pathway
- synapse in raw ventral posterior lateral nucleus (thalamus)
- terminates in the primary somatosensory cortex
Lateral spinothalamic tract
- Type a alpha and type c
- pain and temperature
Lateral spinothalamic tract route
The pathway crosses over at the level of the spinal cord, rather than in the brainstem like the dorsal column-medial lemniscal pathway
Dermatome
- the area of skin supplies by a single nerve root
- the area innervated by a nerve root is larger than that innervated by a puerperal nerve
Peripheral cutaneous nerve
the subcutaneous tissue supply the skin
Hyporeflexia
an absent or diminished response to tapping. It usually indicated a disease that involves one or more of the components of the neuron reflex arc
Hyperreflexia
- hyperactive or repeating (clonic) reflexes
- usually indicate an interruption of corticospinal and other descending pathways that influence the reflex arc due to a suprasegmental lesion, that is, a lesion above the level of the spinal reflex pathway
Deep tendon reflexes
- results from sit,ulation of the stretch-sensitive IA afferents of the neuromuscular spindle producing muscle contraction via a monosynaptic pathway
- tested by tapping sharply over the muscle tendon
are increases in UMN syndrome and decreases in LMN syndrome
What is the DTR grading
0 - Absent (areflexia)
1 - diminished (Hyporeflexia)
2 - Average
3 - exaggerated (brisk)
4 - clonus, very brisk (hyperreflexia)
Proprioceptive reflexes
Clonus
- extension of the wrist or dorsiflexion of the ankle - apply quick overpressure
- positive sign includes more than 3 involuntary beats (1 or 2 beats is normal)
Cutaneous reflexes
- light stroke applied to skin
- the expected response is brief contraction of muscles innervated by the same spinal segments receiving the afferent inputs from the cutaneous receptors
Babinski reflex
- Pathology: pyramidal tract lesion
- Procedure: stroke lateral aspect of the sole of the foot
- Positive: big toe extends and 4 lateral digits fan out
- Normal: all toes flex
Positive: corticospinal tract disruption (pyramidal)
