Brain Mechanism of Movement

Brain Mechanism of Movement

• Body movements happen through the contraction of skeletal muscles.
• Flexion occurs when the flexor muscle contracts, drawing in a limb.
• Extension occurs when the extensor muscle contracts.
• Skeletal muscle fibers feature a striated appearance.

Composition of Skeletal Muscle

• Skeletal muscle consists of two types of fibers: extrafusal and intrafusal.
• Extrafusal fibers are innervated by alpha-motoneurons from the spinal cord and exert force.
• Intrafusal fibers are sensory fibers that detect the stretch of the muscle.
• Afferent fibers report the length of intrafusal fibers; when stretched, they stimulate the alpha-neuron that innervates the muscle fiber, maintaining muscle tone.

Muscle Fiber Structure

• Each muscle fiber comprises a bundle of myofibrils.
• Each myofibril is made of overlapping strands of actin and myosin.
• During a muscle twitch, myosin filaments move relative to actin filaments, shortening the muscle fiber.

Neuromuscular Junction

• The neuromuscular junction is the synapse formed between an alpha motor neuron axon and a muscle fiber.
• Each axon can form synapses with several muscle fibers, creating a motor unit.
• The precision of muscle control relates to the size of the motor unit.
• Smaller motor units facilitate more precise movements (e.g., hand), while larger units manage grosser movements (e.g., legs).

Neuromuscular Transmission

• Acetylcholine (ACh) serves as the neurotransmitter at the neuromuscular junction.
• The release of ACh generates a large endplate potential.
• Voltage changes cause calcium channels to open
• Calcium entry triggers myosin-actin interaction, leading to muscle fiber shortening through the movement of myosin bridges.

Smooth and Cardiac Muscle

• Smooth muscle is regulated by the autonomic nervous system.
• Multiunit smooth muscle is usually inactive, located in large arteries and around hair; responds to neural or hormonal stimulation.
• Single-unit smooth muscle exhibits rhythmic contraction, featuring muscle fibers that produce spontaneous pacemaker potentials; found in the GI tract, uterus, and small blood vessels.
• Cardiac muscle fibers resemble striated muscle in appearance.
• Cardiac muscle exhibits rhythmic contractions like single-unit smooth muscle.

Muscle Sensory Feedback

• Striated muscle contraction is influenced by sensory feedback.
• Intrafusal fibers are parallel with extrafusal fibers.
• Intrafusal receptors initiate firing when extrafusal muscle fibers are stretched, indicating a load on the muscle.
• Intrafusal fibers activate agonist muscle fibers and inhibit antagonist muscle fibers.
• Extrafusal contraction stops intrafusal firing.

Golgi Tendon Organs

• Golgi Tendon Organ (GTO) receptors are in tendons.
• GTO's sense the degree of stretch on a muscle.
• GTO activation inhibits the agonist muscle by releasing glycine onto the alpha-motoneuron.
• GTO receptors prevent the over-contraction of striated muscle.

Spinal Cord Anatomy

• The spinal cord is organized into dorsal and ventral aspects.
• The dorsal horn receives incoming sensory information.
• The ventral horn issues efferent fibers (alpha-motoneurons) that innervate extrafusal fibers.

Spinal Cord Reflexes

• Monosynaptic reflexes: involve a single synapse between a sensory fiber from a muscle and an alpha-motor neuron.
• Sensory fiber activation quickly activates the alpha motor neuron.
• The patellar reflex and monosynaptic stretch reflexes exemplify control of posture.
• Polysynaptic reflexes: involve multiple synapses between sensory axons, interneurons, and motor neurons.
• Axons from afferent muscle spindles can synapse onto alpha motoneurons connected to the agonist muscle, or inhibitory interneurons connected to the antagonist muscle.
• Signals from the muscle spindle activate the agonist and inhibit the antagonist muscle.

Motor Cortex

• Multiple motor systems control body movements, including walking, talking, posture, and arm/finger movements.
• The primary motor cortex is on the precentral gyrus.
• It is somatotopically organized (motor homunculus).
• The pre motor cortex, supplemental motor area, frontal association cortex, and primary somatosensory cortex provide the motor cortex with input.
• Planning of movements involves the premotor cortex and the supplemental motor area, which influence the primary motor cortex.

Descending Motor Pathways

• Axons from the primary motor cortex descend to the spinal cord via two groups: lateral and ventromedial.
• The lateral group controls independent limb movements through three tracts:
  • Corticospinal: controls hand and finger movements.
  • Corticobulbar: manages movements of the face, neck, tongue, and eye.
  • Rubrospinal: controls fore and hind-limb muscles.
• The ventromedial group controls gross limb movements through the following tracts:
  • Vestibulospinal: controls posture.
  • Tectospinal: coordinates eye and head/trunk movements.
  • Reticulospinal: regulates walking, sneezing, and muscle tone.
  • Ventral corticospinal: controls the muscles of the upper leg and trunk.

Corticospinal Tract Details

• Neurons of the corticospinal tract terminate on motor neurons within the gray matter of the spinal cord.
• The corticospinal tract starts in layer 5 of the primary motor cortex, passes through the cerebral peduncles of the midbrain, and decussates(crosses over) in the medulla.
• 80% of fibers become the lateral corticospinal tract, and 20% become the ventral corticospinal tract.
• Fibers terminate onto internuncial neurons or alpha-motoneurons of the ventral horn.
• Corticospinal tracts control fine movements.
  • Destruction can cause loss of muscle strength and reduced dexterity of hands and fingers.
  • Corticospinal lesions, however, have no effect on posture or use of limbs for reaching.

Apraxia

• Apraxia refers to the inability to execute learned, skilled movements following brain damage.
• Limb apraxia involves wrong movements of a limb or incorrect sequences of movements.
  • Callosal apraxia: inability to perform movements of the left hand to a verbal request due to interruption in the anterior callosum.
  • Sympathetic apraxia: damage to the anterior left hemisphere causes apraxia of the left arm, paralysis of the right arm, and hand.
  • Left parietal apraxia: difficulty initiating movements to verbal requests.
  • Constructional apraxia: damage to the right parietal lobe; evidenced by difficulty in drawing or assembling objects.

Basal Ganglia

• The basal ganglia include the caudate nucleus, putamen, and globus pallidus.
• Input to the basal ganglia comes from the primary motor cortex and the substantia nigra.
• Output goes to primary motor cortex, supplemental motor area, premotor cortex, and brainstem motor nuclei (ventromedial pathways).
• The cortical-basal ganglia loop: Frontal, parietal, and temporal cortices send signals to the caudate/putamen. The caudate/putamen projects to the globus pallidus. The globus pallidus projects back to the motor cortex via thalamic nuclei.

Parkinson's Disease

• Parkinson’s Disease (PD) involves muscle rigidity, resting tremor, and slow movements. Results from damage to dopamine neurons within the nigrostriatal bundle.
• This bundle projects to the caudate and putamen.
• Slow movements and postural problems result from loss of excitatory input to the direct circuit or loss of output from the indirect circuit.
• Neurological treatment may consist of transplants of dopamine-secreting neurons. Fetal substantia nigra cells or cells from the carotid body.
• Stereotaxic lesions of the globus pallidus may alleviate some symptoms.

Huntington's Disease

• Huntington’s Disease (HD) involves uncontrollable, jerky movements of the limbs.
• It results from the degeneration of the caudate nucleus and putamen.
• Cell loss involves GABA-secreting axons that innervate the external division of the globus pallidus.
• The GP cells increase their activity, which inhibits the activity of the subthalamic nucleus.
• HD is a hereditary disorder caused by a dominant gene on chromosome 4.
• The gene produces a faulty version of the protein huntingtin.

Cerebellum

• The cerebellum consists of two hemispheres with associated deep nuclei.
• The flocculonodular lobe is at the caudal aspect of the cerebellum, has inputs and outputs to the vestibular system, and is involved in controlling posture.
• The vermis is on the midline of the cerebellum, receiving auditory/visual from the tectum and cutaneous from the spinal cord.
• The vermis projects to the fastigial nucleus, which then projects to the vestibular nucleus and to brainstem motor nuclei.
• Damage to the cerebellum causes jerky, erratic, and awkward movements.

Sleep

• Sleep is a naturally occurring altered state of consciousness.
• Sleep involves decreased awareness and responsiveness to stimuli.
• Sleep is controlled by the reticular-activating and bulbar-synchronizing systems.
• Wakefulness happens when the reticular activating system is activated.
• The hypothalamus has control centers for sleeping and waking.
  • Injury to the hypothalamus may cause someone to sleep for abnormally long periods.
• Biological rhythms that follow a cycle of about 24 hours are known as circadian rhythms.
• Circa means "about," and dies means "day."
• Circadian synchronization can only occur when an individual sleep-wake pattern follows an inner biological clock.
• When physiological and psychological rhythms are high; the person is awake, and when low; the person will sleep.
• Physiologic function is achieved through the use of electrophysiological and neurotransmitter Approaches. Electro-physiologic changes in brain waves, eye movements, and muscles show five sleep stages.
• The neurotransmitter balance involves the interaction of the reticular activating system (RAS), a dynamic interaction of neurotransmitters:
• Serotonin reduces the activity of the RAS, inducing and sustaining sleep. Acetylcholine and Norepinephrine appear to be required for the REM sleep cycle.

Sleep Stages

• Stage 1- Fast theta waves on the EEG, muscles relax, respirations become even, and pulse rate decreases.
• Stage 2- Bursts of sleep spindles appear on the EEG, rolling eye movements continue and snoring can occur, Body functions continue to slow.
• Stages 3 and 4- Delta sleep is seen on the EEG, the muscles are relaxed, respirations are even, and a decrease in vital signs, urine formation and oxygen consumption by muscle.
• Snoring, sleepwalking, and bedwetting are likely to occur in these stages.
• REM (Rapid Eye Movement) sleep closely resembles wakefulness.
  • REM has very low muscle tone with the reduction of the EMG.
  • Blood pressure and pulse rate may show wide variations and may fluctuate rapidly Respirations are irregular, and oxygen consumption increases
• Vaginal secretions increases in women, and erections may occur in men.
• Physiological function sorts and discards neurophysiologic data.
• Character reinforcement and adaptation occur.

Sleep Hygiene

• During the day and before bed, avoid :
  • Napping
  • Stimulants
  • Stimulating exercise
  • Heavy food Try to ensure adequate exposure to natural light during the day. Establish a regular bedtime routine. Try to avoid emotionally upsetting situations before sleep. Associate your bed with sleep—use it mainly for sleeping. Ensure the sleep environment is pleasant and relaxing (clean and cool, dark and quiet).

Factors Affecting Sleep

• Physical activity
  • Psychological stress
  • Motivation
  • Diet
  • Alcohol intake
  • Smoking
  • Environmental factors
  • Lifestyle
  • Illness
  • Medications

Sleep Disorders

• According to the ICD (International Classification of Diseases):

Dyssomnias can be:

• Intrinsic
• Extrinsic
• Due to Disturbance of circadian rhythm

Intrinsic Sleep Disorders:

• Primary insomnia: a troubling or difficulty in falling asleep. Idiopathic insomnia: decreased feeling of well being during the day, a deterioration of mood and motivation, decreased attention span, low level of energy and concentration and increased fatigue. Psychophysiological insomnia: not sleepy during the day but function poorly in terms of cognitive skills and report fatigue.
• Narcolepsy: A condition characterized by an uncontrollable desire to sleep. - Features: - Fall asleep while one is standing up, driving a car, or swimming - Cataplexy - Hallucinations - Sleep paralysis - Disrupted night time sleep
• Narcolepsy Diagnosis: - Polysomnography - Multiple sleep latency test - Narcolepsy Treatment: - Stimulant medication such as methylphenidate, methamphetamine, dextroamphetamine, and modafinil are generally used. -Dependency is common.
  • Hypersomnia: a condition characterized by excessive sleep, particularly during the day.
  • In some cases, sleep drunkenness may be seen.
  • Kleine-Levin Syndrome causes two to three days worth of sleeping (18-20 hours per day) followed by hypersexual behavior, compulsive eating, and irritability.
  • Sleep Apnea Syndrome: periodic breathing ceases between snoring intervals that can be:
  • Obstructive Sleep Apnea
  • Central Sleep Apnea Syndrome
  • Mixed-type Sleep Apnea Syndrome - There is a drop in the blood oxygen level, an irregular pulse, and blood pressure increases; This accumulation results from a brief period of awakening throughout the night. -Periodic Limb Movement Disorder is also called nocturnal myoclonus: In this syndrome, sleep is disturbed by repetitive jerky flexion movements of the limbs during early sleep.
  • Treatment includes small doses of levodopa (100-200 mgs) at night or a dopamine agonist.
• Restless Leg Syndrome (Ekborn’s Syndrome): Unpleasant sensations in the legs are relieved by the legs moving and are more likely to happen at night when rested.
  • Treatment options include clonazepam (0.5-2 mgs) or small amounts of levodopa(100-200 mgs) or a dopamine agonist at night.

Extrinsic Sleep Disorders:

• Secondary insomnia
  • Adjustment insomnia
  • Inadequate sleep hygiene
  • Insomnia associated with psychiatric condition
  • Insomnia caused by a medical condition
  • Insomnia caused by a drug or substance
• Clinical features of insomnia
  • Complain about inability to sleep long/well enough to waken feeling rested or restored.
  • Experience tiredness, fatigue, or trouble concentrating during the day.
  • Diagnosis: -Sleep diaries -Actigraphy -Treatment: -Behavior Therapy: •Stimulus control therapy •Sleep restriction therapy •Relaxation therapy •Cognitive therapy •Sleep hygiene education • •Medication

Circadian Rhythm Sleep Disorders:

• Jet Lag Disorder
• Shift Work Disorder
• Delayed Sleep Phase Disorder
• Advanced Sleep Phase Disorder
• 24 Hour Wake/Sleep Disorder

Parasomnias have conditions associated with arousal during transitions in NREM periods of sleep:

• Arousal Disorders can cause:

• Somnambulism with automatic motor activities

• Sleep terrors including screams, sweating, tachycardia, and hyperventilation.

• Sleep-wake Transition Disorder causes jerking motions of the legs as the sleeping is falling asleep.

• The Parasomnias usually linked to REM Sleep:

• Nightmares with vivid retelling during awakening.

• Sleep Bruxism: Grinding of teeth during sleeping treated by providing custom molds to protect the teeth. .

• Sleep Enuresis: bedwetting that should be treated with the desmopressin 0.2 mg HS, oxybutynin chloride 5-10 mg HS or imipramine 10-50 mg HS

Medical/Psychiatric Sleep Disorders

• Associated with mental disorder
• Associated with neurological disorder
• Associated with medical disorder

Proposed Sleep Disorders

• Short Sleeper Disorder
• Long Sleeper Disorder
• Menstrual Associated Sleep Disorder
• Pregnancy Associated Sleep Disorder
• Sleep Related Laryngospasm

Sleep Deprivation

• Sleep Deprivation refers to a decrease in the amount, consistency, and quality of sleep with increased :
  • Irratibility
  • Inpaired mental abilities
  • Disintegration of personality
  • Partial sleep deprivation causes loss of concentration and safety risks.
• The hospital environment can effect a patient's quality of sleeping.

Treatment of Sleep Disorder

• Medication: Sedative or Hypnotic Medication Benzodiazapines Temazepam and estazolam Diazepam Safer hypnotic agents like lorazepam,temazepam Over the counter sleeping pills contain sedating antihistamines, usually diphenhydramine chloral hydrate
• Antidepressants
  • Stimulants
• Psychotherapy
  • Sleep Education
  • Lifestyle Changes
    • Surgery
• Alternative Treatment

Dreams

Dreams comprise imaginary pictures, sounds, voices, words, thoughts, or feelings. Dreams usually seem real during sleep with both normal.

• Dreams generally take place during REM or Rapid Eye Movement sleep. During this time there will be high brain activity in quick side to side motions.
• Other stages of sleep can create clear memories of your dreams, however, the quality of thoughts will be much less. -The length of can varies, but can lasts as little as a few to as long as twenty continuous minutes. Dreams creates a relation to the inner human self.
• Thoughts can be normal, realistic, bizarre, or surreal.
• It is currently theorized if Dreams has a sole purpose through Scientific research, there are two main hypothesis to the main cause of the thoughts. These are Physiological Theory and Psychological Theory.
• The Physiological is thought to be focusing on how the body or mainly the brain to react while being in it's REM stages.
• There is a thought if Dreams can exercise connections between brain cells. as Where the pshycology is said to look more with the connections of mind

About dreaming

• The body encounters many changes such as increased adrenaline rushing, the blood has a rush, as well the heart is quickening.
• After falling asleep will take from 30 to 90 minutes, as Where our body transitions through a series of Four stages.
• The body during a REM phase will be only 4-7 as We encounter in our sleep. During stage four, it is only 15 to 20 percent of our average slumber.
• Body tempurate can rise, and blood pressure is heightened as the muscles stay in full relaxation.
• All natural movement may be avoided until We reach beyond a normal phase. It has also known as Rem Paralysis,

Importance of Dreaming

• Research has shown those that enter dreaming phase will be met with both irritation and anxiety.
• Volunteers has shown that waking up before, put back to rest can cause over all irritable mood even to go beyond their usual state
• REM sleep deprivation with lack of concentration, over-sensitivity, memory loss.

Daydreams/ Fantasies

• There are many way everyone can interact and imagine those of having something or wanting to be someone different.
• One way is those to think of ways to interact while using the Classroom, the comfort to house, and thinking while to travel the streets.
• It is also way We can imagine what is to come, and motivates Us to think of new and upcoming happenings. With all the positives from fantasy, one such effect is distracting where many minds drift from serious topics causing some to become more and more lost with reality.
• It can be easy to understand others true feelings through Dreams, and be able to fulfill goals as We see where the true self comes into play.

Lucid Dreams

• In some instances We can have insight with our mindset We can encounter Dreams.
• That kind of thought-set is Lucid type Dreams. With that level insight We can encounter positive levels if the thought is mostly to the real state.
• Otherwise one that has fear due by the mindset We can reassure the individual to only think all to be true.
• There are thoughts that most individual can have their own choice and power through the thoughts and choose to encounter from each sleep.

Nightmares

• At one point We had Nightmares, and those certain type are still a type of Dreams, but have different meaning.
• A Nightmares are a subcategory with different ideas, and thought sets but has a sub-class relating to being fearful. When that certain situation can happen, people may find themselves a fright from what has played.

recurring Dreams - There are a different thought during Dreams that tend to teach an specific lesson :

Most will forget what has happened but if those persist it will be extremely important.

• If Those moments will replay more and more, it will force the dreamer to see the message one is sending/receiving. The core message the Dream may be related to fear

Prophetic Dreams

• Prophetic Dreams can also be known as precognitive or pschic Dreams where in ones mind the ability can piece things to see what can come.
• It may be that the natural mindset can piece more than other but has to encounter it consciously to be able see all at the same time.

Epic Dream

• When encountering those situations with epic thoughts one may be seen as remarkable due the vivid set of memories one can hold for long periods.

• There tends to have lots of beauty in symbolic form.

• When waking with those Dreams, there is way to view from the world where many people may find amazing to share. These tend to stay with a person for a huge milestone.