Anatomy and Physiology Ch 15-17

Direct pathways

(voluntary movements): from cerebral cortex to lower motoneurons e.g., lateral and anterior corticospinal. iii) Corticobulbar tracts -synapse on lower motor neurons in the motor nuclei of cranial nerves III, IV, V, VI,IX, XI, XII. Function: provide conscious control over skeletal muscles that move the eye, jaw, and face, some muscles of neck and pharynx

Sleep-wakefulness

-----circadian rhythm (suprachiasmatic nucleus and hypothalamus). Reticular formation (RAS) control increase and decrease activity in cerebral cortex Arousal -increased activity—inut from sensory receptors like eye, ear (sunlight, alarm). Sleep types a) REM-rapid eye movement and b) None REM—has four stages. REM -every 90 minutes (adults). Dreams occur in both REM and non-REM sleep but REM dreams-longer, emotional. Parasympathetic system very active during REM sleep---constriction of pupils and erection of penis or clitoris. Sleeper is hard to awake during REM sleep. Sleep paralysis strong in REM sleep—this may prevent sleeper to act on dreams

exteroceptors

----location near or on external surface---e.g., special senses

proprioceptors

---in muscle , tendon, joints. Three Major Groups of Proprioceptors Muscle spindles Golgi tendon organs Receptors in joint capsules

PAIN

-injured tissue release chemical bradykinin-most potent stimulus. Release of serotonin, prostaglandin, and histamine also stimulate pain receptors.

interoceptors

-inside body, e.g., blood vessels , visceral organs---no conscious sensation,

Projection2

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Higher-order functions involve

1) are performed by the cerebral cortex, 2) Involve conscious and unconscious information processing, 3) are subject to modification and adjustment over time.

Which of the following serve as receptors to measure body position and balance? inner ear receptors muscle spindles Golgi tendon organs All of the listed responses are correct.

All of the listed responses are correct

Tactile corpuscles

Also called Meissner's corpuscles Perceive sensations of fine touch, pressure, and low-frequency vibration Adapt to stimulation within 1 second after contact Fairly large structures Most abundant in the eyelids, lips, fingertips, nipples, and external genitalia

Thermoreceptors

Also called temperature receptors Are free nerve endings located in: The dermis Skeletal muscles The liver The hypothalamus Conducted along the same pathways that carry pain sensations

Which receptors are common in superficial portions of the skin, in joint capsules, within the periostea of bones, and around the walls of blood vessels? nociceptors mechanoreceptors thermoreceptors All of the listed responses are correct.

Answer: nociceptors

memory consolidation

Conversion from short-term to long term

Which of the following is NOT classified as a general sense? pressure olfaction temperature pain

General Senses describe our sensitivity to: Temperature Pain Touch Pressure Vibration Proprioception Answer: olfaction

Which of the following statements about adaptation is FALSE? It can occur in the CNS when inhibition of nuclei occurs along a sensory pathway. It is a reduction in sensitivity in the presence of a constant stimulus. It can occur peripherally when the level of receptor activity changes. It is a feature of tonic receptors but not of phasic receptors.

It is a feature of tonic receptors but not of phasic receptors.

tendon organs

Located at the junction between skeletal muscle and its tendon Stimulated by tension in tendon Monitor external tension developed during muscle contraction

Which type of receptor detects pressure changes? nociceptor thermoreceptor baroreceptor tactile receptor

Nociceptors (Pain Receptors) tactile receptor Provide the sensations of touch, pressure, and vibration Baroreceptors Detect pressure changes in the walls of blood vessels and in portions of the digestive, reproductive, and urinary tracts Answer: baroreceptor

Nociceptors Receptors

Pain Receptors common In the superficial portions of the skin, In joint capsules, Within the periostea of bones, Around the walls of blood vessels Are free nerve endings with large receptive fields have Myelinated Type A fibers (Carry sensations of fast pain ex. injection or a deep cut; often trigger somatic reflexes; Relayed to the primary sensory cortex) and non Myelinated Type C fibers (Carry sensations of slow pain, or burning and aching pain; cause a generalized activation of the reticular formation and thalamus; you become aware of the pain but only have a general idea of the area affected)

Lamellated receptors

Pressure receptors Also called Pacinian corpuscles Sensitive to deep pressure Fast-adapting receptors Most sensitive to pulsing or high-frequency vibrating stimuli

Area is monitored by a single receptor cell

Receptive field

Which of the following is NOT considered a special sense? olfaction proprioception equilibrium gustation

Special Senses Olfaction (smell) Vision (sight) Gustation (taste) Equilibrium (balance) Hearing Answer: proprioception

Non-REM sleep

Stage 1 feel drowsy, close eyes and begin to relax. Waken easily. EEG—alpha waves dominant. Stage 2 sleeper is in light sleep and EEG declines in frequency but increase in amplitude, have sleep spindles (high spikes-due to interaction between neurons of thalamus and cerebral cortex. Stage 3 deep sleep-begin 20 minutes after stage 1, less sleep spindles, theta and delta waves in EEG appear, muscle relax, vital signs( temperature, blood pressure, heart rate, respiratory rate) fall. Stage 4 called slow-wave sleep because EEG is dominated by low-frequency and high amplitude delta waves. Muscle relaxed, vital signs are at lowest level, difficult to wake a person.

Corticospinal pathway or pyramidal pathway

Three corticospinal pathways: i) lateral corticospinal tract ii) anterior corticospinal tract iii) corticobulbar tract. i) Corticospinal tracts are visible in medulla as pair of thick bands called pyramids, most of the axons decussate here and descend as i) lateral corticospinal tract. ii) Those that do not cross over enter the as anterior corticopinal tracts.

Sensory receptors structural types

a) free nerve endings of 1st order neuron, b) encapsulated nerve endings, c) separate cells.

Sensory modality groups

a) general senses such as somatic senses and visceral senses b) special senses such as smell, taste, vision.

Sensory receptors base on stimulus

a) osmoreceptors, b) thermoreceptors, c) photoreceptors, d) nociceptors e) chemoreceptors.

Joint kinesthetic receptors

a) pressure receptors--pacinian corpuscle b) muscle spindle c) tendon organs.

Characteristics of receptors

a) rapidly adapting receptors—quick adaptation, e.g., touch, pressure, b) slowly adapting ---adapt slowly, e.g., pain.

Process of Sensation

a) sensory receptors—have selectivity to certain stimuli b) transduction -transformation of one type of energy into another type, c) generation of nerve impulses by first order neurons.

Sensation

a) tactile b) Pressure receptors or laminated c) thermal receptors d) pain receptors b) cutaneous ---Type I ---Merkel disc B) Type II ---Ruffini corpuscles

Free nerve endings

bare dendrites, no special structure, e.g., pain, thermal, tickle and itch

Referred pain

brains misidentification of location of pain. T1-T5 receive input from heart, chest and arm—follows pathways from thalamus to cerebral cortex. The pain of a heart attack is frequently felt in the left arm The pain of appendicitis is generally felt first in the area around the navel and then in the right, lower quadrant

Three major somatosensory pathways

carry sensation from the skin and musculature of the body wall, head, neck, and limbs: a) posterior column pathway, b) spinothalamic pathway and c) spiocerebellar pathway

Chemoreceptors

chemical concentration

Ruffini corpuscles

cutaneous -in dermis, tendons and ligaments --- encapsulated.

Tactile discs

cutaneous Also called Merkel discs Fine touch and pressure receptors Extremely sensitive to tonic receptors Have very small receptive fields are saucer shaped on stratum basale and have fine touch sensation.

Encapsulated

dendrites enclosed in connective tissue, e.g., touch, pressure.

CNS modulation of pain

enkephlins and endorphins, dymorphins -block pain. Modulation is by mid brain, pituitary, digestive tract secretion. They block pain. Pain signal can be stopped by dorsal horn by a) descending analgesic fibers from brain stem to spinal cord (reticulospinal tract).

First order neurons

from receptors to brain stem (via spinal cord).

Somatic sensory pathways to cerebellum

include a) posterior and b) anterio lateral spinocerebellar tracts. These tracts carry proprioception, unconscious sensation.

Somatic motor pathways

involve upper motor neurons (cell bodies in CNS) and a lower motoneuron (cell bodies located in the nucleus of lower brain stem or spinal cord. a) direct--- pyramidal b) indirect---extrapyramidal.

Ascending pathways

nociceptors to second order neuron by substance P. Second order nerve fibers -spinothalamic tract to thalamus -by 3rd order neuron to cerebral cortex -gives conscious awareness of pain.

Brain regions involve in memory consolidation

nucleus basalis- a cerebral nucleus near diencephalon. Tract fibers connect this nucleus with hippocampus, amygdaloid body, and all areas of the cerebral cortex.

Projection

of cerebrum. Pain signal in spinal reticular tract travel to the reticular formation ---then hypothalamus and limbic system---producing emotional and behavioral and visceral responses of pain like nausea, fear.

Mechanoreceptors

physical distortion

Somato sensory pathways

posterior column pathway, anterio-lateral pathways and anterio-lateral spinothalamic pathways.

Sensory modality

refers to a type of sensation or stimulus like touch

Separate cells

sensory receptors for specialized senses, e.g., hair cells, photoreceptors

Anteriolateral Spinothalamic pathways

— lateral spinothalamic (pain and temperature sensations) and anterior spinothalamic (crude touch and pressure). Anteriolateral spinothalamic—first order neuron-dorsal root ganglia; axon enter CNS in dorsal roots of spinal cord and synapse over second order neurons within spinal cord, Second order neurons in spinal cord cross and proceed to brain stem in anterior or lateral spinothalamic tract. Third order neurons synapse in the primary sensory cortex Lateral spinothalmic -pain and temperature. Anterior spinothalamic-tickle, itch, crude touch, pressure.

Posterior column pathways

—Fasiculus gracilis and fasciculus cuneatus lying on each side of posterior median sulcus of spinal cord. Fasciculus gracilis is medial to cuneatus. Functions: proprioception, fine touch, pressure and vibrations. First order neuron —in dorsal root ganglia. Axons of these neurons ascend to nucleus gracilis and nucleus cuneatus of medulla oblongata. Second order neuron ascend from medullary nucleus gracilis and cuneatus to thalamus. As they ascend, they crossover to opposite side (decussation). After crossing over, axons enter a tract called medial lemniscus and synapse on third-order neurons of the thalamus. Thalamus perceives sensation as fine touch, pressure and vibration. Precise location of sensation from a particular body part depends on projection from the thalamus to primary sensory cortex. Third order neuron to primary somatosensory areas of cortex. Fibers are for fine touch, stereognosis, proprioception, vibratory senses.

Sensory receptors base on location

—a) exteroceptors b) interoceptors c) proprioceptors

Indirect motor pathways

—extrapyramidal pathways (also called medial pathway): vestibulospinal (information related to maintaining posture and balance; Rubrospinal (primary control muscle tone and movements of the distal muscles of the upper limbs), tectospinal (change the position of head, neck, and upper limbs in response to bright lights); medial reticulospinal (receives input from every ascending and descending tracts) Basal ganglia control muscle movement. Unwanted movements suppressed by inhibitory effect on thalamus and superior collculus.

Second order neuron

—from brain stem to thalamus, decussation in spinal cord or brain stem.

Third order neuron

—from thalamus to primary cortex.

muscle spindle

—has intrafusal and extrafusal fibers---alpha motoneuron in anterior horn and gamma motor neurons Monitor skeletal muscle length Trigger stretch reflexes

Descending pathways

—hypothalamus and cerebral cortex to midbrain to reticular formation of medulla to spinal cord (via reticulospinal tract) to spinal interneurons to second order pain fibers.