CONTROL OF MOVEMENT

Movement Classification

REFLEX

Rapid, automatic response to specific stimuli

Reflex arc:1. Stimulus -> Receptor2. Activation sensory neuron3. Information processing4. Activation motor neuron5. Response peripheral effector

Classification of reflex

Monosynaptic Reflex Stretch reflex, eg: patellar

reflex Receptor is muscle

spindle consist of a bundle of small, specialized skeletal muscle fibers (intrafusal muscle fibers),

surrounded by larger skeletal muscle (extrafusal muscle fibers)

Postural reflex, reflexes that help us maintain normal upright posture

Polysynaptic Reflex

Interneurons involved can control several muscle groups

Can produce EPSPs or IPSPs at CNS motor nuclei -> stimulation some fibers and inhibition other Tendon reflex, produced during a

muscular contraction that prevents breaking of the tendons

Withdrawal reflexes or Flexor reflex move affected parts of body away from a stimulus.

Reciprocal inhibition, when one set of motor neurons is stimulated, those neurons that control antagonistic muscles are inhibited. When the flexors contract, the extensors relax; when the extensors contract, the flexors relax.

Crossed extensor reflex

VOLUNTARY MOVEMENT

Cerebral cortex

Motor and Sensory Area of the Cortex

Primary motor cortex (Frontal Lobe) Neurons of the primary motor cortex direct

voluntary movements by controlling somatic motor neurons in the brain stem and spinal cord.

Primary sensory cortex (Parietal Lobe) Neurons in this region receive somatic sensory

information from receptors for touch, pressure, pain, vibration, taste, or temperature.

We are aware of these sensations only when nuclei in the thalamus relay the information to the primary sensory cortex.

The visual cortex of the occipital lobe receives visual information, and

The auditory cortex and olfactory cortex of the temporal lobe receive information about hearing and smell, respectively.

The gustatory cortex, which receives information from taste receptors of the tongue and pharynx, lies in the anterior portion of the insula and adjacent portions of the frontal lobe.

Association Area

The sensory and motor regions of the cortex are connected to nearby association areas, regions of the cortex that interpret incoming data or coordinate a motor response

Sensory association areas are cortical regions that monitor and interpret the information that arrives at the sensory areas of the cortex somatic sensory association area visual association area auditory association area

Integrative Centers

Integrative centers are areas that receive information from many association areas and direct extremely complex motor activities. Prefrontal cortex integrates information from

sensory association areas and performs abstract intellectual functions, such as predicting the consequences of possible responses so it generate feelings of frustration, tension, and anxiety

General interpretative area on the left hemisphere, Wernicke’s area receives information from all sensory association area

Speech center or Broca’s area or Motor speech area, regulates the patterns of breathing and vocalization needed for normal speech. Some neurons from general interpretative

area innervate speech center. A person with a damaged speech center can

make sounds but not words. Brodman area

Brodman area 44 correspond to speech center

Brodman area 41 to auditory cortex

Hemispheric Lateralization Hemispheric Lateralization or Regional

Specialization shows that each of the two cerebral hemispheres is responsible for specific functions that are not ordinarily performed by the opposite hemisphere.

Left hemisphere contains the general interpretive and speech centers is responsible for language-based skills and

performance analytical task such as mathematical calculation and logical decision-making -> dominant hemisphere

the premotor cortex involved with the control of hand movements is larger on the left side for right-handed individuals than for left handed ones.

Right hemisphere analyzes sensory information identify familiar objects by touch, smell,

sight, taste or feel, in recognizing faces or analyzing emotional context of a conversation

Somatic Nervous System The somatic nervous system, or somatic motor

system, controls the contractions of skeletal muscles. Somatic motor pathways involve at least two motor

neurons: an upper motor neuron, whose cell body lies in a CNS

processing center, and a lower motor neuron, whose cell body lies in a nucleus of

the brain stem or spinal cord. The upper motor neuron synapses on the lower

motor neuron, which in turn innervates a single motor unit in a skeletal muscle.

Activity in the upper motor neuron may facilitate or inhibit the lower motor neuron.

Activation of the lower motor neuron triggers a contraction in the innervated muscle.

Corticospinal Pathway

The corticospinal pathway, sometimes called the pyramidal system, provides voluntary control over skeletal muscles. This system begins at the pyramidal cells of the primary motor cortex.

The corticospinal pathway contains three pairs of descending tracts: (1) the corticobulbar tracts, (2) the lateral corticospinal tracts, and (3) the anterior corticospinal tracts.

The Corticobulbar Tracts

Axons in the corticobulbar tracts synapse on lower motor neurons in the motor nuclei of cranial nerves III, IV, V, VI, VII, IX, XI, and XII.

The Corticospinal Tracts Axons in the corticospinal tracts

synapse on lower motor neurons in the anterior gray horns of the spinal cord.

As they descend, the corticospinal tracts are visible along the ventral surface of the medulla oblongata as a pair of thick bands, the pyramids

Medial and Lateral Pathways

Several centers in the cerebrum, diencephalon, and brain stem may issue somatic motor commands as a result of processing performed at a subconscious level.

These centers and their associated tracts were long known as the extrapyramidal system (EPS), because it was thought that they operated independently of, and in parallel with, the pyramidal system (corticospinal pathway).

Medial pathway help control gross movements of the trunk and proximal limb muscles.

Lateral pathway help control the distal limb muscles that perform more precise movements.

The Medial Pathway

The upper motor neurons of the medial pathway are located in the vestibular nuclei, the superior and inferior colliculi, and the reticular formation

The vestibular nuclei receive information, over the vestibulocochlear nerve (N VIII), from receptors in the internal ear that monitor the position and movement of the head.

The primary goal is to maintain posture and balance.-> vestibulospinal tracts

respond to changes in the orientation of the head, sending motor commands that alter the muscle tone, extension, and position of the neck, eyes, head, and limbs.

The superior and inferior colliculi are located in the tectum, or roof of the midbrain

The superior colliculi receive visual sensations and the inferior colliculi receive auditory sensations -> tectospinal tract

direct reflexive changes in the position of the head, neck, and upper limbs in response to bright lights, sudden movements, or loud noises.

The reticular formation is a loosely organized network of neurons that extends throughout the brain stem.-> reticulospinal tract

The reticular formation receives input from almost every ascending and descending pathway

For example, the stimulation of upper motor neurons in one portion of the reticular formation produces eye movements, whereas the stimulation of another portion activates respiratory muscles.

The Lateral Pathway

The upper motor neurons of the lateral pathway lie within the red nuclei of the midbrain -> rubrospinal tracts

In humans, the rubrospinal tracts are small and extend only to the cervical spinal cord.

There they provide motor control over distal muscles of the upper limbs;

Basal Nuclei The basal nuclei are masses of gray

matter that lie within each hemisphere deep to the floor of the lateral ventricle

The basal nuclei are involved with the subconscious control of skeletal muscle tone and the coordination of learned movement patterns. When you walk, the basal nuclei control the

cycles of arm and thigh movements that occur between the time you decide to “start” walking and the time you give the “stop” order.

As you begin a voluntary movement, the basal nuclei control and adjust muscle tone, particularly in the appendicular muscles, to set your body position. When you decide to pick up a pencil, you

consciously reach and grasp with your forearm, wrist, and hand while the basal nuclei operate at the subconscious level to position your shoulder and stabilize your arm.

Activity of the basal nuclei is inhibited by neurons in the substantia nigra of the midbrain, which release the neurotransmitter dopamine. If the substantia nigra is damaged or the

neurons secrete less dopamine, basal nuclei become more active.

The result is a gradual, generalized increase in muscle tone and the appearance of symptoms characteristic of Parkinson’s disease. -> difficulty starting voluntary movements, because opposing muscle groups do not relax; they must be overpowered.

Medulla Oblongata

1. Autonomic Nuclei Controlling Visceral Activities

Reflex centers: cardiovascular centers, respiratory rhythmicity centers

2. Sensory and Motor Nuclei of Cranial Nerve VII, IX, X, XI & XII

3. Relay Station along Sensory and Motor Pathway

Nucleus gracilis and nucleus caudatus pass somatic sensory information to the thalamus, cross to the opposite side of the brain (decussation) before reaching destination

Pons

1. Sensory and Motor Nuclei of Cranial Nerves

V, VI, VII & VIII

2. Nuclei involved with the Control of Respiration;

Apneustic center and Pneumotaxic center

3. Nuclei and Tracts That Process and Relay Information Sent to or from the Cerebellum

4. Ascending, Descending, and Transverse Tracts

Cerebellum

The cerebellum coordinates learned and reflexive patterns of muscular activity at the subconscious level:

1. Adjusting the Postural Muscles of the Body Coordinates rapid, automatic adjustments that maintain

balance and equilibrium by modifying activities motor centers in brain stem

2.Programming and Fine-Tuning Movements Controlled at the Conscious and Subconscious Levels

Ataxia is a disturbance in muscular coordination caused permanently cerebellar damage by trauma or stroke or temporarily affected by drugs such as alcohol

The Spinocerebellar Pathway The spinocerebellar pathway conveys information about muscle, tendon, and joint positions from the spine to the cerebellum

This information does not reach our awareness.

The axons of first-order sensory neurons synapse on interneurons in the dorsal gray horns of the spinal cord.

The axons of these second-order neurons ascend in one of the spinocerebellar tracts: the posterior spinocerebellar tracts or the anterior spinocerebellar tracts.

The sensations carried by the anterior spinocerebellar tracts reach the cerebellar cortex via the superior cerebellar peduncle.

Pengaturan Postur

Brain stem (batang otak) dan serebellum mengontrol refleks postur

The cerebellum monitors proprioceptive (position) sensations, visual information from the eyes, and vestibular (balance) sensations from the internal ear as movements are under way.

Midbrain

Midbrain

The midbrain regulates auditory and visual reflexes and controls alertness

Contains Reticular Activating System (RAS) that makes alert and attentive

Diencephalon Diencephalon integrates sensory information

with motor output at the subconscious level Diencephalon is a division of a brain consists of

epi thalamus, thalamus and hypothalamus Ascending sensory information from the spinal

cord and cranial nerves (other than the olfactory tract) synapses in a nucleus in the left or right thalamus before reaching the cerebral cortex and our conscious awareness.

The hypothalamus contains centers involved with emotions and visceral processes that affect the cerebrum as well as other components of the brain stem.

Thalamus

Thalamus is the final relay point for ascending sensory information that will be projected to the primary sensory cortex.

It acts as a filter, passing on only a small portion of the arriving sensory information.

The thalamus also coordinates the activities of the basal nuclei and the cerebral cortex by relaying information between them.

Hypothalamus

1. Subconscious Control of Skeletal Muscle Contractions

2. Control of Autonomic Function3. Coordination of Activities of the

Nervous and Endocrine System4. Secretion of Two Hormones

ADH by supraoptic nucleus & Oxytocin by Paraventricular nucleus

5. Production of Emotion and Behavioral Drives

6. Coordination between Voluntary and Autonomic Functions

7. Regulation of Body TemperaturePreoptic area coordinates other CNS centers and regulates other physiological systems to maintain body temperature

8. Control of Circadian RhythmsSuprachiasmatic nucleus coordinates daily cycles, receive input from retina and its output adjust activities of hypothalamic nuclei, pineal gland and reticular formation.

Limbic System

Limbic system includes nuclei and tracts along the border between cerebrum and diencephalon

Functions: Establishing emotional states Linking the conscious, intellectual

functions of the cerebral cortex with the unconscious and autonomic functions of the brain stem; and

Facilitating memory storage and retrieval.

Summary ; CNS Control of Voluntary Movement

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