Chapter 16 Sensory Motor Integrative Systems Lecture Outline

Chapter 16 Sensory, Motor & Integrative Systems Lecture Outline 1

INTRODUCTION • The components of the brain interact to receive sensory input, integrate and store the information, and transmit motor responses. • To accomplish the primary functions of the nervous system there are neural pathways to transmit impulses from receptors to the circuitry of the brain, which manipulates the circuitry to form directives that are transmitted via neural pathways to effectors as a response. Principles of Human Anatomy and Physiology, 11 e 2

Chapter 16 Sensory, Motor & Integrative Systems • • Levels and components of sensation Pathways for sensations from body to brain Pathways for motor signals from brain to body Integration Process – wakefulness and sleep – learning and memory Principles of Human Anatomy and Physiology, 11 e 3

SENSATION • Sensation is a conscious or unconscious awareness of external or internal stimuli. Principles of Human Anatomy and Physiology, 11 e 4

Is Sensation Different from Perception? • Perception is the conscious awareness & interpretation of a sensation. – precisely localization & identification – memories of our perceptions are stored in the cortex • Sensation is any stimuli the body is aware of – Chemoreceptors, thermoreceptors, nociceptors, baroreceptors – What are we not aware of? • X-rays, ultra high frequency sound waves, UV light – We have no sensory receptors for those stimuli Principles of Human Anatomy and Physiology, 11 e 5

Sensory Modalities • Sensory Modality is the property by which one sensation is distinguished from another. • Different types of sensations – touch, pain, temperature, vibration, hearing, vision – Generally, each type of sensory neuron can respond to only one type of stimulus. • Two classes of sensory modalities – general senses – special senses Principles of Human Anatomy and Physiology, 11 e 6

Sensory Modalities • The classes of sensory modalities are general senses and special senses. – The general senses include both somatic and visceral senses, which provide information about conditions within internal organs. – The special senses include the modalities of smell, taste, vision, hearing, and equilibrium. Principles of Human Anatomy and Physiology, 11 e 7

Process of Sensation • Sensory receptors demonstrate selectivity – respond to only one type of stimuli • Events occurring within a sensation – stimulation of the receptor – transduction (conversion) of stimulus into a graded potential • vary in amplitude and are not propagated – generation of impulses when graded potential reaches threshold – integration of sensory input by the CNS Principles of Human Anatomy and Physiology, 11 e 8

Sensory Receptors • Receptor Structure may be simple or complex – General Sensory Receptors (Somatic Receptors) • no structural specializations in free nerve endings that provide us with pain, tickle, itch, temperatures • some structural specializations in receptors for touch, pressure & vibration – Special Sensory Receptors (Special Sense Receptors) • very complex structures---vision, hearing, taste, & smell Principles of Human Anatomy and Physiology, 11 e 9

Alternate Classifications of Sensory Receptors • • Structural classification Type of response to a stimulus Location of receptors & origin of stimuli Type of stimuli they detect Principles of Human Anatomy and Physiology, 11 e 10

Structural Classification of Receptors • Free nerve endings – bare dendrites – pain, temperature, tickle, itch & light touch • Encapsulated nerve endings – dendrites enclosed in connective tissue capsule – pressure, vibration & deep touch • Separate sensory cells – specialized cells that respond to stimuli – vision, taste, hearing, balance Principles of Human Anatomy and Physiology, 11 e 11

Structural Classification • Compare free nerve ending, encapsulated nerve ending and sensory receptor cell Principles of Human Anatomy and Physiology, 11 e 12

Classification by Stimuli Detected • Mechanoreceptors – detect pressure or stretch – touch, pressure, vibration, hearing, proprioception, equilibrium & blood pressure • Thermoreceptors detect temperature • Nociceptors detect damage to tissues • Photoreceptors detect light • Chemoreceptors detect molecules – taste, smell & changes in body fluid chemistry Principles of Human Anatomy and Physiology, 11 e 13

Classification by Response to Stimuli • Generator potential – free nerve endings, encapsulated nerve endings & olfactory receptors produce generator potentials – when large enough, it generates a nerve impulse in a firstorder neuron • Receptor potential – vision, hearing, equilibrium and taste receptors produce receptor potentials – receptor cells release neurotransmitter molecules on firstorder neurons producing postsynaptic potentials – PSP may trigger a nerve impulse • Amplitude of potentials vary with stimulus intensity Principles of Human Anatomy and Physiology, 11 e 14

Classification by Location • Exteroceptors – near surface of body – receive external stimuli – hearing, vision, smell, taste, touch, pressure, pain, vibration & temperature • Interoceptors – monitors internal environment (BV or viscera) – not conscious except for pain or pressure • Proprioceptors – muscle, tendon, joint & internal ear – senses body position & movement Principles of Human Anatomy and Physiology, 11 e 15

Adaptation in Sensory Receptors • Most sensory receptors exhibit adaptation – the tendency for the generator or receptor potential to decrease in amplitude during a maintained constant stimulus. • Receptors may be rapidly or slowly adapting. Principles of Human Anatomy and Physiology, 11 e 16

Adaptation of Sensory Receptors • Change in sensitivity to long-lasting stimuli – decrease in responsiveness of a receptor • bad smells disappear • very hot water starts to feel only warm – potential amplitudes decrease during a maintained, constant stimulus • Variability in tendency to adapt: – Rapidly adapting receptors (smell, pressure, touch) • specialized for detecting changes – Slowly adapting receptors (pain, body position) • nerve impulses continue as long as the stimulus persists – Pain is not easily ignored. Principles of Human Anatomy and Physiology, 11 e 17

SOMATIC SENSATIONS • Receptors for somatic sensation are summarized in Table 16. 2) Principles of Human Anatomy and Physiology, 11 e 18

Tactile Sensations • Tactile sensations are touch, pressure, and vibration plus itch and tickle. • receptors include (Figure 16. 2) – corpuscles of touch (Meissner’s corpuscles), – hair root plexuses, – type I (Merkel’s discs) – type II cutaneous (Ruffini’s corpuscles) – mechanoreceptors, – lamellated (Pacinian) corpuscles, – free nerve endings Principles of Human Anatomy and Physiology, 11 e 19

Touch • Crude touch refers to the ability to perceive that something has simply touched the skin • Discriminative touch (fine touch) provides specific information about a touch sensation such as location, shape, size, and texture of the source of stimulation. • Receptors for touch include corpuscles of touch (Meissner’s corpuscles) and hair root plexuses; these are rapidly adapting receptors. • Type I cutaneous mechanoreceptors (tactile or Merkel discs) and type II cutaneous mechanoreceptors (end organs of Ruffini) are slowly adapting receptors for touch (Figure 16. 2). Principles of Human Anatomy and Physiology, 11 e 20

Pressure and Vibration • Pressure is a sustained sensation that is felt over a larger area than touch. – Pressure sensations generally result from stimulation of tactile receptors in deeper tissues and are longer lasting and have less variation in intensity than touch sensations – Receptors for pressure are type II cutaneous mechanoreceptors and lamellated (Pacinian) corpuscles. • Like corpuscles of touch (Meissner’s corpuscles), lamellated corpuscles adapt rapidly. • Vibration sensations result from rapidly repetitive sensory signals from tactile receptors – receptors for vibration sensations are corpuscles of touch and lamellated corpuscles, which detect low-frequency and high-frequency vibrations, respectively. Principles of Human Anatomy and Physiology, 11 e 21

Itch and Tickle • Itch and tickle receptors are free nerve endings. – Tickle is the only sensation that you may not elicit on yourself. Principles of Human Anatomy and Physiology, 11 e 22

Meissner’s Corpuscle • Dendrites enclosed in CT in dermal papillae of hairless skin • Discriminative touch & vibration-- rapidly adapting • Generate impulses mainly at onset of a touch Principles of Human Anatomy and Physiology, 11 e 23

Hair Root Plexus • Free nerve endings found around follicles, detects movement of hair Principles of Human Anatomy and Physiology, 11 e 24

Merkel’s Disc • Flattened dendrites touching cells of stratum basale • Used in discriminative touch (25% of receptors in hands) Principles of Human Anatomy and Physiology, 11 e 25

Ruffini Corpuscle • Found deep in dermis of skin • Detect heavy touch, continuous touch, & pressure Principles of Human Anatomy and Physiology, 11 e 26

Pacinian Corpuscle • Onion-like connective tissue capsule enclosing a dendrite • Found in subcutaneous tissues & certain viscera • Sensations of pressure or high-frequency vibration Principles of Human Anatomy and Physiology, 11 e 27

Somatic Tactile Sensations - Summary • Touch – crude touch is ability to perceive something has touched the skin – discriminative touch provides location and texture of source • Pressure is sustained sensation over a large area • Vibration is rapidly repetitive sensory signals • Itching is chemical stimulation of free nerve endings • Tickle is stimulation of free nerve endings only by someone else Principles of Human Anatomy and Physiology, 11 e 28

Thermal Sensations • Free nerve endings with 1 mm diameter receptive fields on the skin surface – Cold receptors in the stratum basale respond to temperatures between 50 -105 degrees F – Warm receptors in the dermis respond to temperatures between 90 -118 degrees F • Both adapt rapidly at first, but continue to generate impulses at a low frequency • Pain is produced below 50 and over 118 degrees F. Principles of Human Anatomy and Physiology, 11 e 29

Pain Sensations • Pain receptors (nociceptors) are free endings that are located in nearly every body tissue – Free nerve endings found in every tissue of body except the brain – adaptation is slight if it occurs at all. • Stimulated by excessive distension, muscle spasm, & inadequate blood flow • Tissue injury releases chemicals such as K+, kinins or prostaglandins that stimulate nociceptors Principles of Human Anatomy and Physiology, 11 e 30

Types of Pain • Fast pain (acute) – occurs rapidly after stimuli (. 1 second) – sharp pain like needle puncture or cut – not felt in deeper tissues – larger A nerve fibers • Slow pain (chronic) – begins more slowly & increases in intensity – aching or throbbing pain of toothache – in both superficial and deeper tissues – smaller C nerve fibers Principles of Human Anatomy and Physiology, 11 e 31

Types of Pain • Somatic pain that arises from the stimulation of receptors in the skin is superficial, while somatic pain that arises from skeletal muscle, joints, and tendons is deep. • Visceral pain, unlike somatic pain, is usually felt in or just under the skin that overlies the stimulated organ – localized damage (cutting) intestines may cause no pain, but diffuse visceral stimulation can be severe • distension of a bile duct from a gallstone • distension of the ureter from a kidney stone – pain may also be felt in a surface area far from the stimulated organ in a phenomenon known as referred pain (Figure 16. 3). Principles of Human Anatomy and Physiology, 11 e 32

Referred Pain • Visceral pain that is felt just deep to the skin overlying the stimulated organ or in a surface area far from the organ. • Skin area & organ are served by the same segment of the spinal cord. – Heart attack is felt in skin along left arm since both are supplied by spinal cord segment T 1 -T 5 Principles of Human Anatomy and Physiology, 11 e 33

Pain Relief Multiple sites of analgesic action: • Aspirin and ibuprofen block formation of prostaglandins that stimulate nociceptors • Novocaine blocks conduction of nerve impulses along pain fibers • Morphine lessen the perception of pain in the brain. Principles of Human Anatomy and Physiology, 11 e 34

Proprioceptive Sensations • Receptors located in skeletal muscles, in tendons, in and around joints, and in the internal ear convey nerve impulses related to muscle tone, movement of body parts, and body position. This awareness of the activities of muscles, tendons, and joints and of balance or equilibrium is provided by the proprioceptive or kinesthetic sense. Principles of Human Anatomy and Physiology, 11 e 35

Proprioceptive or Kinesthetic Sense • Awareness of body position & movement – walk or type without looking – estimate weight of objects • Proprioceptors adapt only slightly • Sensory information is sent to cerebellum & cerebral cortex – signals project from muscle, tendon, joint capsules & hair cells in the vestibular apparatus – receptors discussed here include muscle spindles, tendon organs (Golgi tendon organs), and joint kinesthetic receptors (Figure 16. 4). Principles of Human Anatomy and Physiology, 11 e 36

Muscle Spindles • Specialized intrafusal muscle fibers enclosed in a CT capsule and innervated by gamma motor neurons • Stretching of the muscle stretches the muscle spindles sending sensory information back to the CNS • Spindle sensory fiber monitor changes in muscle length • Brain regulates muscle tone by controlling gamma fibers Principles of Human Anatomy and Physiology, 11 e 37

Golgi Tendon Organs • Found at junction of tendon & muscle • Consists of an encapsulated bundle of collagen fibers laced with sensory fibers • When the tendon is overly stretched, sensory signals head for the CNS & resulting in the muscle’s relaxation Principles of Human Anatomy and Physiology, 11 e 38

Joint Receptors • Ruffini corpuscles – found in joint capsule – respond to pressure • Pacinian corpuscles – found in connective tissue around the joint – respond to acceleration & deceleration of joints Principles of Human Anatomy and Physiology, 11 e 39

SOMATIC SENSORY PATHWAYS • Somatic sensory pathways relay information from somatic receptors to the primary somatosensory area in the cerebral cortex. • The pathways consist of three neurons – first-order, – second-order, and – third-order • Axon collaterals of somatic sensory neurons simultaneously carry signals into the cerebellum and the reticular formation of the brain stem. Principles of Human Anatomy and Physiology, 11 e 40

Somatic Sensory Pathways • First-order neuron conduct impulses to the CNS (brainstem or spinal cord) – either spinal or cranial nerves • Second-order neurons conducts impulses from brain stem or spinal cord to thalamus – cross over to opposite side of body • Third-order neuron conducts impulses from thalamus to primary somatosensory cortex (postcentral gyrus of parietal lobe) Principles of Human Anatomy and Physiology, 11 e 41

Posterior Column-Medial Lemniscus Pathway to the Cortex • The nerve impulses for conscious proprioception and most tactile sensations ascend to the cortex along a common pathway formed by three-neuron sets (Figure 16. 16 a). • These neurons are a part of the posterior (dorsal) columns – consist of the gracile fasciculus and cuneate fasciculus • Impulses conducted along this pathway – fine touch, – stereognosis, – proprioception, and – vibratory sensations Principles of Human Anatomy and Physiology, 11 e 42

Posterior Column-Medial Lemniscus Pathway of CNS • Proprioception, vibration, discriminative touch, weight discrimination & stereognosis • Signals travel up spinal cord in posterior column • Fibers cross-over in medulla to become the medial lemniscus pathway ending in thalamus • Thalamic fibers reach cortex Principles of Human Anatomy and Physiology, 11 e 43

Anterolateral Pathways to the Cortex • 3 -neuron pathway • The anterolateral or spinothalamic pathways carry mainly pain and temperature impulses (Figure 16. 5 b). • They also relay the sensations of tickle and itch and some tactile impulses. Principles of Human Anatomy and Physiology, 11 e 44

Spinothalamic Pathway of CNS • Lateral spinothalamic tract carries pain & temperature • Anterior tract carries tickle, itch, crude touch & pressure • First cell body in DRG with synapses in cord • 2 nd cell body in gray matter of cord, sends fibers to other side of cord & up through white matter to synapse in thalamus • 3 rd cell body in thalamus projects to cerebral cortex Principles of Human Anatomy and Physiology, 11 e 45

Somatosensory Map of Postcentral Gyrus • Relative sizes of cortical areas – proportional to number of sensory receptors – proportional to the sensitivity of each part of the body • Can be modified with learning – learn to read Braille & will have larger area representing fingertips Principles of Human Anatomy and Physiology, 11 e 46

Somatic Sensory Pathways to the Cerebellum • The posterior spinocerebellar and the anterior spinocerebellar tracts are the major routes whereby proprioceptive impulses reach the cerebellum. – impulses conveyed to the cerebellum are critical for posture, balance, and coordination of skilled movements. • Table 16. 3 summarizes the major sensory tracts in the spinal cord and pathways in the brain. Principles of Human Anatomy and Physiology, 11 e 47

Sensory Pathways to the Cerebellum • Major routes for proprioceptive signals to reach the cerebellum – anterior spinocerebellar tract – posterior spinocerebellar tract • Subconscious information used by cerebellum for adjusting posture, balance & skilled movements • Signal travels up to same side inferior cerebellar peduncle Principles of Human Anatomy and Physiology, 11 e 48

Clinical Application - Syphilis causes a progressive degeneration of the posterior portions of the spinal cord. – Sexually transmitted disease caused by bacterium Treponema pallidum. – Third clinical stage known as tertiary syphilis – Progressive degeneration of posterior portions of spinal cord & neurological loss • loss of somatic sensations • proprioceptive impulses fail to reach cerebellum – People watch their feet while walking, but are still uncoordinated and jerky Principles of Human Anatomy and Physiology, 11 e 49

SOMATIC MOTOR PATHWAYS • Lower motor neurons extend from the brain stem or spinal cord to skeletal muscles. • These lower motor neurons are called the final common pathway because many regulatory mechanisms converge on these peripheral neurons. Principles of Human Anatomy and Physiology, 11 e 50

Somatic Motor Pathways - Overview • Control of body movement – motor portions of cerebral cortex • initiate & control precise movements – basal ganglia help establish muscle tone & integrate semivoluntary automatic movements – cerebellum helps make movements smooth & helps maintain posture & balance • Somatic motor pathways – direct pathway from cerebral cortex to spinal cord & out to muscles – indirect pathway includes synapses in basal ganglia, thalamus, reticular formation & cerebellum Principles of Human Anatomy and Physiology, 11 e 51

SOMATIC MOTOR PATHWAYS • Four distinct neural circuits (somatic motor pathways) participate in control of movement by providing input to lower motor neurons (Figure 16. 7). – Local circuit neurons are located close to lower motor neuron cell bodies in the brain stem and spinal cord. – Local circuit neurons and lower motor neurons receive input from upper motor neurons. – Neurons of the basal ganglia provide input to upper motor neurons. – Cerebellar neurons also control activity of upper motor neurons. Principles of Human Anatomy and Physiology, 11 e 52

SOMATIC MOTOR PATHWAYS • Organization of upper motor neuron pathways – Direct motor pathways provide input to lower motor neurons via axons that extend directly from the cerebral cortex. – Indirect pathways provide input to lower motor neurons from motor centers in the brain stem • Paralysis: damage of lower motor neurons produces flaccid paralysis while injury to upper motor neurons causes spastic paralysis. Principles of Human Anatomy and Physiology, 11 e 53

Primary Motor Cortex Principles of Human Anatomy and Physiology, 11 e • The primary motor area is located in the precentral gyrus of the frontal lobe (Figure 16. 6 b) – upper motor neurons initiate voluntary movement • The adjacent premotor area and somatosensory area of the postcentral gyrus also contribute axons to descending motor pathways. • The cortical area devoted to a muscle is proportional to the number of motor units. – More cortical area is needed if number of motor units in a muscle is high • vocal cords, tongue, lips, fingers & thumb 54

Direct motor pathways • The direct pathways (pyramidal tracts) include (Figure 16. 8). – lateral and anterior corticospinal tracts – corticobulbar tracts • The various tracts of the pyramidal system convey impulses from the cerebral cortex that result in precise muscular movements. • Table 16. 4 summarizes the functions and pathways of the tracts in the direct motor pathways. Principles of Human Anatomy and Physiology, 11 e 55

Direct Pathways (Pyramidal Pathways) • 1 million upper motor neurons in cerebral cortex • Axons form internal capsule in cerebrum and pyramids in the medulla oblongata • 90% of fibers decussate (cross over) in the medulla – right side of brain controls left side muscles • Terminate on interneurons which synapse on lower motor neurons in either: – nuclei of cranial nerves – anterior horns of spinal cord • Integrate excitatory & inhibitory input to become final common pathway Principles of Human Anatomy and Physiology, 11 e 56

Details of Pyramidal Pathways • Lateral corticospinal tracts – cortex, cerebral peduncles, 90% decussation of axons in medulla, tract formed in lateral column. – skilled movements (hands & feet) • Anterior corticospinal tracts – the 10% of axons that do not cross – controls neck & trunk muscles • Corticobulbar tracts – cortex to nuclei of CNs • III, IV, V, VII, IX, X, XI & XII – movements of eyes, tongue, chewing, expressions & speech Principles of Human Anatomy and Physiology, 11 e 57

Location of Direct Pathways • Lateral corticospinal tract • Anterior corticospinal tract • Corticobulbar tract Principles of Human Anatomy and Physiology, 11 e 58

Application • Amyotrophic Lateral Sclerosis (ALS) is a disease hat attacks motor areas of the cerebral cortex, axons of upper motor neurons and cell bodies of lower motor neurons. • It causes progressive muscle weakness. • There are several theories as to its cause. While there is no cure, several drugs are used to treat the symptoms. Principles of Human Anatomy and Physiology, 11 e 59

Paralysis • Flaccid paralysis = damage lower motor neurons – no voluntary movement on same side as damage – no reflex actions – muscle limp & flaccid – decreased muscle tone • Spastic paralysis = damage upper motor neurons – paralysis on opposite side from injury – increased muscle tone – exaggerated reflexes Principles of Human Anatomy and Physiology, 11 e 60

Indirect Pathways • Indirect or extrapyramidal pathways include all somatic motor tracts other than the corticospinal and corticobulbar tracts. – involve the motor cortex, basal ganglia, thalamus, cerebellum, reticular formation, and nuclei in the brain stem (Figure 16. 8). – indirect tracts are the rubrospinal, tectospinal, vestibulospinal, lateral reticulospinal and medial reticulospinal tracts. • Table 16. 4 summarizes the major motor tracts, their functions, and pathways in the brain. Principles of Human Anatomy and Physiology, 11 e 61

Indirect Pathways • All other descending motor pathways • Complex polysynaptic circuits – include basal ganglia, thalamus, cerebellum, reticular formation • Descend in spinal cord as 5 major tracts • All 5 tracts end upon interneurons or lower motor neurons Principles of Human Anatomy and Physiology, 11 e 62

Final Common Pathway • Lower motor neurons receive signals from both direct & indirect upper motor neurons • Sum total of all inhibitory & excitatory signals determines the final response of the lower motor neuron & the skeletal muscles Principles of Human Anatomy and Physiology, 11 e 63

Roles of the basal ganglia • The circuit from the cerebral cortex to basal ganglia to thalamus to cortex seems to function in initiating and terminating movement. – basal ganglia also suppress unwanted movements – basal ganglia may influence aspects of cortical function including sensory, limbic, cognitive, and linguistic functions. • Damage to the basal ganglia results in uncontrollable, abnormal body movements, often accompanied by muscle rigidity and tremors. • Parkinson disease and Huntington disease result from damage to the basal ganglia. Principles of Human Anatomy and Physiology, 11 e 64

Basal Ganglia • Helps to program automatic movement sequences – walking and arm swinging or laughing at a joke • Set muscle tone by inhibiting other motor circuits Principles of Human Anatomy and Physiology, 11 e 65

Basal Ganglia Connections - Review • Circuit of connections – cortex to basal ganglia to thalamus to cortex – planning movements • Output from basal ganglia to reticular formation – reduces muscle tone – damage produces rigidity of Parkinson’s disease Principles of Human Anatomy and Physiology, 11 e 66

Modulation of Movement by the Cerebellum • The cerebellum is active in both learning and performing rapid, coordinated, highly skilled movements and in maintaining proper posture and equilibrium. • The four aspects of cerebellar function (Figure 16. 9) – monitoring intent for movement, – monitoring actual movement, – comparing intent with actual performance, and – sending out corrective signals • Damage to the cerebellum is evidenced by ataxia and intention tremors. Principles of Human Anatomy and Physiology, 11 e 67

Cerebellar Function Aspects of Function • learning • coordinated & skilled movements • posture & equilibrium 1. Monitors intentions for movements -- input from cerebral cortex 2. Monitors actual movements with feedback from proprioceptors 3. Compares intentions with actual movements 4. Sends out corrective signals to motor cortex Principles of Human Anatomy and Physiology, 11 e 68

INTEGRATIVE FUNCTIONS OF THE CEREBRUM • The integrative functions include sleep and wakefulness, memory, and emotional responses. (discussed in Chapter 14). Principles of Human Anatomy and Physiology, 11 e 69

Wakefulness and Sleep Role of the Reticular Activating System (RAS) • Sleep and wakefulness are integrative functions that are controlled by the reticular activating system (Figure 16. 10). – Arousal, or awakening from a sleep, involves increased activity of the RAS. – When the RAS is activated, the cerebral cortex is also activated and arousal occurs. – The result is a state of wakefulness called consciousness. Principles of Human Anatomy and Physiology, 11 e 70

Reticular Activating System • RAS has connections to cortex & spinal cord. • Many types of inputs can activate the RAS---pain, light, noise, muscle activity, touch • Coma is sleep-like state – A person in a deep coma has no reflexes. Principles of Human Anatomy and Physiology, 11 e 71

Wakefulness and Sleep • Circadian rhythm – 24 hour cycle of sleep and awakening – established by hypothalamus • EEG recordings show large amount of activity in cerebral cortex when awake Principles of Human Anatomy and Physiology, 11 e 72

Sleep • During sleep, a state of altered consciousness or partial unconsciousness from which an individual can be aroused by different stimuli, • During sleep activity in the RAS is very low. • Normal sleep consists of two types: – non-rapid eye movement sleep (NREM) and – rapid eye movement sleep (REM) Principles of Human Anatomy and Physiology, 11 e 73

Sleep • Triggers for sleep are unclear – adenosine levels increase with brain activity – adenosine levels inhibit activity in RAS – caffeine prevents adenosine from inhibiting RAS • Non-rapid eye movement or slow wave sleep consists of four stages, each of which gradually merges into the next. • Most dreaming occurs during rapid eye movement sleep. Principles of Human Anatomy and Physiology, 11 e 74

Non-Rapid Eye Movement Sleep • Stage 1 – person is drifting off with eyes closed (first few minutes) • Stage 2 – fragments of dreams – eyes may roll from side to side • Stage 3 – very relaxed, moderately deep – 20 minutes, body temperature & BP have dropped • Stage 4 = deep sleep – bed-wetting & sleep walking occur in this phase Principles of Human Anatomy and Physiology, 11 e 75

REM Sleep • Most dreams occur during REM sleep • In first 90 minutes of sleep: – go from stage 1 to 4 of NREM, – go up to stage 2 of NREM – to REM sleep • Cycles repeat until total REM sleep totals 90 to 120 minutes • Neuronal activity & oxygen use is highest in REM sleep • Total sleeping & dreaming time decreases with age Principles of Human Anatomy and Physiology, 11 e 76

Learning and Memory • Learning is the ability to acquire new knowledge or skills through instruction or experience. • Memory is the process by which that knowledge is retained over time. • For an experience to become part of memory, it must produce persistent functional changes that represent the experience in the brain. • The capability for change with learning is called plasticity. Principles of Human Anatomy and Physiology, 11 e 77

Learning and Memory • Memory occurs in stages over a period and is described as immediate memory, short term memory, or long term memory. – Immediate memory is the ability to recall for a few seconds. – Short-term memory lasts only seconds or hours and is the ability to recall bits of information; it is related to electrical and chemical events. – Long-term memory lasts from days to years and is related to anatomical and biochemical changes at synapses. Principles of Human Anatomy and Physiology, 11 e 78

Amnesia • Amnesia refers to the loss of memory • Anterograde amnesia is the loss of memory for events that occur after the trauma; the inability to form new memories. • Retrograde amnesia is the loss of memory for events that occurred before the trauma; the inability to recall past events. Principles of Human Anatomy and Physiology, 11 e 79

DISORDERS: HOMEOSTATIC IMBALANCES • Phantom pain is the sensations of pain in a limb that has been amputated; the brain interprets nerve impulses arising in the remaining proximal portions of the sensory nerves as coming from the nonexistent (phantom) limb. Another explanation is that the neurons in the brain that received input from the missing limbs are still active. Principles of Human Anatomy and Physiology, 11 e 80

Spinal Cord Injury • Spinal cord injury can be due to damage in a number of ways, such as compression or transection, and the location and extent of damage determines the type and degree of loss in neural abilities. – tumor, herniated disc, clot, trauma … • Paralysis – monoplegia is paralysis of one limb only – diplegia is paralysis of both upper or both lower – hemiplegia is paralysis of one side – quadriplegia is paralysis of all four limbs • Spinal shock is loss of reflex function (areflexia) – slow heart rate, low blood pressure, bladder problem – reflexes gradually return Principles of Human Anatomy and Physiology, 11 e 81

Cerebral Palsy • Loss of motor control and coordination • Damage to motor areas of the brain – infection of pregnant woman with rubella virus – radiation during fetal life – temporary lack of O 2 during birth • Not a progressive disease, but irreversible Principles of Human Anatomy and Physiology, 11 e 82

Parkinson Disease • Parkinson’s disease is a progressive degeneration of CNS neurons of the basal nuclei region due to unknown causes that decreases dopamine neurotransmitter production. – Environmental toxins may be the cause in some cases • Neurons from the substantia nigra do not release enough dopamine onto basal ganglia – tremor, rigidity, bradykinesia (slow movement) or hypokinesia (decreasing range of movement) – may affect walking, speech, and facial expression • Treatments – drugs to increase dopamine levels (L-Dopa), or to prevent its breakdown – surgery to transplant fetal tissue or removal of part of globus pallidus to slow tremors – acetylcholine inhibitors Principles of Human Anatomy and Physiology, 11 e 83

end Principles of Human Anatomy and Physiology, 11 e 84