Download Exam2 Motor & Sensory Systems | PHARM 5114 - ANATOMY AND PHYSIOLOGY 1 and more Quizzes Health sciences in PDF only on Docsity!
Alpha motor unit
A single alpha motor neuron and the skeletal muscle fibers (cells) that it innervatesThe alpha motor unit is referred to as the "final common pathway" because all changes to the state of contraction of skeletal muscle must ultimately be transmitted through the alpha motor neurons that innervate individual muscle cells. TERM 2
Neural pathways connect different structures
in the brain w/ the alpha motor units; For
example...
DEFINITION 2
- The Corticospinal Tract - the pyramidal tract / direct activation pathway2. Extrapyramidal Tracts - indirect activation pathways Originate in midbrain: Tectospinal Tract and Rubrospinal Tract Vestibulospinal tract - originates in vestibular nuclei in the pons Reticulospinal tract - originates in reticular formation of the pons & medulla TERM 3
The Corticospinal Tract
DEFINITION 3 aka The Pyramidal Tract Connects cerebral cortex areas where movements are consciously initiated (primary motor cortex and motor association area) to the spinal cord location of the alpha motor neurons Direct activation pathway TERM 4
Extrapyramidal Tracts
DEFINITION 4 These are neural pathways that link multiple brain areas to the alpha motor neurons - also called indirect activation pathways TERM 5
Extrapyramidal tracts originating in the
midbrain
DEFINITION 5 Tectospinal tract - originates in the dorsal midbrainRubrospinal tract - originates in the red nucleus of the midbrain
Two other extrapyramidal tracts not
originating in the midbrain
Vestibulospinal tract - this pathway originates in the vestibular nuclei in the pons and is involved in vestibular function (balance and posture) Reticulospinal tract - originates in the reticular formation of the pons and medulla TERM 7
Function of the Corticospinal Pathway
DEFINITION 7 To initiate and control skilled voluntary motor activity Particularly important for fine motor control of extremities, i.e. hands and feet Well-developed in humans and other primates and accounts for the tremendous control we have in our hands and feet TERM 8
Origin of the Corticospinal Pathway
DEFINITION 8 The cell bodies of the first neuron ( corticospinal neuron ) are located in: Primary motor area - precentral gyrus of frontal cortex Premotor area - anterior to precentral gyrus TERM 9
How is the corticospinal pathway organized?
DEFINITION 9 Somatotopically - homunculi - certain parts of body have a greater degree of motor control than others Fingers have very extensive representation TERM 10
Crossover point of corticospinal pathway
DEFINITION 10 Midline (decussate) in the medulla The point of crossover is at the caudal extent of the medulla where it merges into the spinal cord at about the level of the foramen magnum
Inputs to the Alpha Motor Neuron (Final
common pathway)
- Spinal reflexes Direct synapse with primary sensory afferents (stretch reflex) Synapse with interneurons, inhibitory or excitatory (flexor and crossed extensor reflexes)
- Corticospinal tract - direct & interneuron synapses3. Indirect activation pathways TERM 17
The cerebellum has been referred to as the
"silent area" because:
DEFINITION 17
- Standard methods of stimulating cerebellar neurons produced no movement2. No evidence of conscious sensation in cerebellum3. If parts of the cerebellum are destroyed by strokes or tumors, paralysis is not observed TERM 18
How is damage to the cerebellum
manifested?
DEFINITION 18 Deficits that are seen during the conduct of motor activity, particularly apparent are the loss of coordination of movement of the limbs and eyes TERM 19
Functions of Cerebellum
DEFINITION 19
- Insures that muscle movements are completed exactly as they are consciously intended Controls timing & pattern of muscle activation, coordinates actions of all muscles involved in a movement (synergy), and smooth muscle movements by damping oscillations
- Subconscious correction of skeletal muscle contraction to maintain posture & equilibrium3. Stores learned movement patterns - writing, typing, playing instrument TERM 20
Where is the cerebellum located?
DEFINITION 20 Superior to the pons and medulla 2 hemispheres, 3 lobes Connected to pons by cerebellar peduncles Cortex (gray matter) 3 pair of deep nuclei
What forms the cerebellar peduncles?
Formed by the axons of neurons ascending and descending from the cerebellum TERM 22
Cortex (gray matter) of cerebellum
DEFINITION 22
- All body parts are somatotopically represented - sensory & motor2. 3 cellular layers - columnar arrangement of cells Molecular layer (outermost) Purkinje layer (middle) - inhibitory neuron (GABA), only output from cortex Granule layer TERM 23
What do the 3 pair of deep nuclei
do?
DEFINITION 23 Efferent output to other regions of the central nervous system arise in these nuclei TERM 24
Afferents to the Cerebellum
DEFINITION 24
- Spinocerebellar tracts2. Vestibular nuclei3. Cerebral cortex TERM 25
Spinocerebellar tracts
DEFINITION 25 Convey info from the limbs and trunk of the body concerning: Muscle length - muscle spindle Joint position - joint receptors Muscle tension - Golgi tendon organs Touch and pressure - from various mechanoreceptors
Asynergia
Loss of coordination of muscles involved in a movement TERM 32
Ataxia
DEFINITION 32 Disturbance in balance - drunk walking TERM 33
Intention tremor
DEFINITION 33 Oscillating tremor at the end of a movement ex. touch your nose, overshoot, tremor at end TERM 34
Decomposition of movement
DEFINITION 34 Action is performed in parts TERM 35
Adiadochokinesis
DEFINITION 35 Inability to perform alternating movements rapidly and smoothly, e.g. typing, finger tapping
Nystagmus
Eyes turn rapidly toward an object then slowly away TERM 37
Scanning speech
DEFINITION 37 Decompose words into separate syllables due to inability to coordinate muscle involved in speech TERM 38
Basal Ganglia (Cerebral Nuclei) Structure
DEFINITION 38 *Structures are bilateral Corpus striatum - putamen & caudate nucleus, they function together and are connected by bridges which cross the internal capsule Globus pallidus Subthalamic nucleus Substantia nigra - midbrain nucleus that sends projection neurons to corpus stratium TERM 39
Afferent input to Striatum
DEFINITION 39
- Cortex - cortical motor areas communicate extensively with the corpus striatum when a skeletal muscle movement is initiated and during the conduct of the movement2. Substantia nigra - this nucleus in the midbrain contains the cells bodies of dopamine neurons that send axons to the striatum in the nigrostriatal tract; dopamine released from these neurons exerts and inhibitory effect on striatum neurons TERM 40
Efferent output from Striatum
DEFINITION 40 Travels through globus pallidus and passes through the thalamus on its way back to the cortical motor areas
