PSB 3002 Exam 2: Part 2

monosynaptic stretch reflex

A reflex in which a muscle contracts in response to its being quickly stretched; involves a sensory neuron and a motor neuron, with one synapse between them.

clasp knife reflex

A reflex that occurs when force is applied to flex or extend the limb of an animal showing decerebrate rigidity; resistance is replaced by sudden relaxation

parietal reach region

A region in the medial posterior parietal cortex that plays a critical role in control of pointing or reaching with the hands

supplementary motor area (SMA)

A region of motor association cortex of the dorsal and dorsomedial frontal lobe, rostral to the primary motor cortex

premotor cortex

A region of motor association cortex of the lateral frontal lobe, rostral to the primary motor cortex

ventrolateral periaqueductal gray matter (vlPAG)

A region of the dorsal midbrain that contains REM-OFF neurons; part of the REM flip-flop.

sublateodorsal nucleus (SLD)

A region of the dorsal pons, just ventral to the locus coeruleus, that contains REM-ON neurons; part of the REM flip-flop

zeitgeber

A stimulus (usually the light of dawn) that resets the biological clock that is responsible for circadian rhythms.

caudate nucleus

A telencephalic nucleus, one of the input nuclei of basal ganglia; involved with control of voluntary movement.

putamen

A telencephalic nucleus; one of the input nuclei of the basal ganglia; involved with control of voluntary movement

globus pallidus

A telencephalic nucleus; the primary output nucleus of the basal ganglia; involved with control of voluntary movement.

ventrolateral nucleus (of thalamus)

A thalamic nucleus that receives projections from the basal ganglia and sends projections to the motor cortex

ventral anterior nucleus (of thalamus)

A thalamic nucleus that receives projections from the basal ganglia and sends projections to the motor cortex.

somatotopic organization

A topographically organized mapping of parts of the body that are represented in a particular region of the brain

decerebrate rigidity

Simultaneous contraction of agonistic and antagonistic muscles; caused by decerebration or damage to the reticular formation.

Explain how a relatively small number of receptors can detect a wide variety of odors

A particular odorant binds to more than one receptor and different odorants produce patterns of activity in different glomeruli. Recognizing a particular odor involves recognizing a particular pattern of activity in the glomeruli. The primary olfactory cortex contains an olfactory map that appears to be based on the chemical structure of odorant molecules.

melanopsin

A photopigment present in ganglion cells in the retina whose axons transmit information to the SCN, the thalamus, and the olivary pretectal nuclei

chroda tympani

A branch of the facial nerve that passes beneath the eardrum; conveys taste information from the anterior part of the tongue and controls the secretion of some salivary glands

olfactory glomerulus

A bundle of dendrites of mitral cells and the associated terminal buttons of the axons of olfactory receptors.

circadian rhythm

A daily rhythmical change in behavior or physiological process

locus coeruleus (LC)

A dark-colored group of noradrenergic cell bodies located in the pons near the rostral end of the floor of the fourth ventricle; involved in arousal and vigilance

pineal gland

A gland attached to the dorsal tectum; produces melatonin and plays a role in circadian and seasonal rhythms.

ventrolateral preoptic area (vlPOA)

A group of GABAergic neurons in the preoptic area whose activity suppresses alertness and behavioral arousal and promotes sleep.

raphe nuclei

A group of nuclei located in the reticular formation of the medulla, pons, and midbrain, situated along the midline; contain serotonergic neurons

melatonin

A hormone secreted during the night by the pineal body; plays a role in circadian and seasonal rhythms.

motor unit

A motor neuron and its associated muscle fibers

flexion

A movement of a limb that tends to bend its joints; the opposite of extension

extension

A movement of a limb that tends to straighten its joints; the opposite of flexion

intrafusal muscle fiber

A muscle fiber that functions as a stretch receptor, arranged parallel to the extrafusal muscle fibers, thus detecting changes in muscle length

adenosine

A neuromodulator that is released by neurons engaging in high levels of metabolic activity; may play a primary role in the initiation of sleep

mitral cell

A neuron located in the olfactory bulb that receives information from olfactory receptors; axons of mitral cells bring information to the rest of the brain

alpha motor neuron

A neuron whose axon forms synapses with extrafusal muscle fibers of a skeletal muscle; activation contracts the muscle fibers.

gamma motor neuron

A neuron whose axons form synapses with intrafusal muscle fibers.

histamine

A neurotransmitter synthesized from the amino acid histidine; plays an important role in maintenance of wakefulness and arousal

subthalamic nucleus

A nucleus located ventral to the thalamus, an important part of the subcortical motor system that includes the basal ganglia; a target of deep-brain stimulation for treatment of Parkinson's disease

nucleus of the solitary tract

A nucleus of the medulla that receives information from visceral organs and from the gustatory system

suprachiasmatic nucleus (SCN)

A nucleus situated atop the optic chiasm. It contains a biological clock that is responsible for organizing many of the body's circadian rhythms

Explain how adenosine contributes to regulating sleep.

Adenosine is released when neurons use glycogen, and it serves as the link between increased brain metabolism and the necessity of sleep. When neurons are active, glycogen is depleted and adenosine accumulates. Accumulating adenosine serves as a sleep-promoting signal. Glycogen is replenished during slow-wave sleep and adenosine levels decrease.

myofibril

An element of muscle fibers that consists of overlapping strands of actin and myosin; responsible for muscular contractions.

hyperdirect pathway

An excitatory pathway from the pre-SMA to the subthalamic nucleus that increases the activity of the GPi and appears to play a role in preventing or quickly stopping movements that are being initiated by the direct pathway. indirect pathway (in basal ganglia)

List the six qualities of taste stimuli

Bitterness, sourness, sweetness, saltiness, umami, and fat

Compare the roles of slow-wave and REM sleep in learning.

Both REM and slow-wave sleep promote learning: REM sleep facilitates nondelcarative learning and slow-wave sleep facilitates declarative learning.

Describe how brain lesions can produce limb apraxia.

Constructional apraxia is caused by lesions of the right hemisphere, particularly the right parietal love. People with this disorder have trouble drawing pictures or assembling objects fro elements such as toy building blocks.

decerebrate

Describes an animal whose brain stem has been transected

apraxia

Difficulty in carrying out purposeful movements, in the absence of paralysis or muscular weakness

constructional apraxia

Difficulty in drawing pictures or diagrams or in making geometrical constructions of elements such as building blocks or sticks; caused by damage to the right parietal lobe

List examples of circadian rhythms and zeitgebers.

Examples of circadian rhythms include the: sleep/wake cycle, cycles of physical activity and body temperature. Examples of zeitgebers include the presence of illumination, clocks, or other time clues.

Describe how acetylcholine, norepinephrine, serotonin, histamine, and orexin contribute to regulating arousal.

Five systems of neurons appear to be important for alert, active wakefulness. The acetocholinergic system of the pons and the basal forebrain is involved in cortical activation. The noradrenergic system of the locus coeruleus is involved in vigilance. The serotongeric system of the raphe nucleus is involved in activation of automatic behaviors such as locomotion and grooming. the histaminergic neurons of the tuberomammilary nucleus are involved in maintaining wakefulness. The orexinergic system of the lateral hypothalamus is involved in maintaining wakefulness.

Summarize the roles of homeostatic/allostatic /circadian factors, brain regions, flip-flop circuits, and neurotransmitter systems in regulating transitions between sleep and wake.

Homeostatic control of sleep maintains the balance of sleep/wake at an optimal level. Sleep can also be regulated by allostatic control, which responds to the environmental stressors to override homeostatic control when needed. Circadian factors entrain periods of sleep to particular portions of the light/dark cycle. Slow-wave sleep occurs when neurons in the ventrolateral preoptic area (vIOPA) become active. These neurons inhibit the systems of neurons that promote wakefulness. In turn, the vIPOA is inhibited by these sam wakefulness promoting neurons of the vIOPA. Activity of the orexinergic neurons of the lateral hypothalamus keeps the flip-flip that controls sleep and waking in the 'waking" state.

Contrast the types of information detected by afferent axons of muscle spindles and Golgi tendon organs

Intrafusal muscle fibers contain sensory endings that are sensitive to stretch. Receptors on intrafusal muscle fibers detect muscle length. Golgi tendon organs contain stretch receptors for tendons.

process of transduction for perception of salt, sour, bitter, sweet, and umami

Molecules bind with receptor cells and produce changes in membrane permeability that cause receptor potentials. The receptor for saltiness seems to be a simple sodium channel, which allows sodium ions to enter the cell and depolarize it. The receptors for sour likely interact with hydrogen and anions. Receptors sensitive to bitterness, sweetness, and umami are linked to a G protein.

Process of transducing the signal from an odorant molecule

Molecules of odorant bind with olfactory receptors, and the G proteins coupled to these receptors open sodium channels and produce depolarizing receptor potentials.

Explain the function of monosynaptic stretch reflexes.

Monosynaptic stretch responses function to control limb movements when weight is applied or removed quickly and to maintain upright posture.

Describe how brain lesions can produce constructional apraxia.

Most cases of limb apraxia are produced by lesions of the left frontal or parietal cortex. The left parietal cortex directly controls movement of the right limb by activation neurons in the left primary motor cortex and indirectly controls movement of the left limb by sending information to the right frontal association cortex.

mirror nucleus

Neurons located in the ventral premotor cortex and inferior parietal lobule that respond when the individual makes a particular movement or sees another individual making that movement

Suggest some possible functions of slow wave sleep.

One important function of slow-wave sleep seems to be to lower the brain's metabolism and permit it to rest. In support of this hypothesis, research has shown that slow-wave sleep reduces the brain's metabolic rate and that increased mental activity (the surprise fun-day-out experiment) can cause an increase in slow-wave sleep the next night.

extrafusal muscle fiber

One of the muscle fibers that are responsible for the force exerted by contraction of a skeletal muscle

myosin

One of the proteins (with actin) that provide the physical basis for muscular contraction.

actin

One of the proteins (with myosin) that provide the physical basis for muscular contraction

skeletal muscle

One of the striated muscles attached to bones

Describe the role of flip-flop circuits in neural control of transition to REM.

REM sleep is controlled by another flip-flop. The subleterodorsal nucleus (SLD) serves as the REN-ON region, and the ventrolateral periaqueductal gray region (vIPAG) serves as the REM-FF region. This flip-flop is controlled by the sleep/waking flip-flop; only when the sleep/waking flip-flop is in the sleeping state can the REM flip-flop switch to the "REM" state. The muscular paralysis that prevents us from acting out our dreams is produced by connections between neurons in the SLD that excite inhibitory interneurons in the spinal cord.

striated muscle

Skeletal muscle; muscle that contains striations.

Describe the structures of a skeletal muscle

Skeletal muscles contain extrafusal muscle fibers, which provide the force of contraction. The alpha motor neurons from synapses with the extrafusal muscle fibers and control their contraction. Skeletal muscles also contain intrafusal muscle fibers, which detect changes in muscle length. The length of the intrafusal muscle fiber, and hence its sensitivity to increase in muscle length, is controlled by the gamma motor neuron. Besides the intrafusal muscle fibers, the muscles contain stretch receptors in the Golgi tendon organs, located at the ends of the muscles.

Path of gustatory processing from nerves to subcortical and cortical structures

Taste receptors in the tongue send taste information to the brain via cranial nerves. Taste information first enters the nucleus of the solitary tract in the medulla, then to the thalamus, the the primary gustatory cortex, and finally the secondary gustatory cortex. Unlike most other sense modalities, taste is ipsilaterally represented in the brain. The primary gustatory cortex contains a taste map.

Describe the relationship between the pineal gland and melatonin

The SCN and he pineal gland control annual rhythms. During the night the SCN signals the pineal glad to secrete melatonin. Prolonged melatonin secretion, which occurs during winter, causes animals to enter the winter phase of their annual cycle. Melatonin also appears to be involved in synchronizing circadian rhythms: The hormone can help people to adjust to the effects of shift work or jet lag and even synchronize the daily rhythms of blind people for whom light cannot serve as a zeitgeber.

Identify the role of the suprachiasmatic nucleus in regulating circadian rhythms, and explain how the clock mechanism functions.

The SCN is responsible for circadian regulation of sleep, but not homeostatic regulation. After receiving light information from the eyes, information from the SCN is conveyed via the subparaventicular zone and the dorsomedial nucleus of the hypothalamus to regions of the brain involved in sleep and waking. Individual neurons, rather than circuits of neurons, are responsible for the 'ticking".Each tick, approx. 24 hours long, consists of the production and breakdown of a series of proteins in two interlocking loops that act back on the genes responsible for their own production.

lateral group

The corticospinal tract, the corticobulbar tract, and the rubrospinal tract

Summarize the contributions of the parietal cortex in reaching and grasping behavior

The dorsal stream of the visual association cortex contributes spatial information to the parietal reaching region, which calculates the reaching movement that must be made and transmits this information to the motor association cortex. During the reaching movement the cortex located in the anterior intraparietal sulcus sends information to the motor association cortex that moves he hand and fingers to be ready to grasp an object.

olfactory epithelium

The epithelial tissue of the nasal sinus that covers the cribriform plate; contains the cilia of the olfactory receptors.

Identify some possible functions of REM sleep.

The functions of REM sleep are less understood than that of slow-wave sleep. REM sleep may promote brain development and facilitate changes responsible for learning that occur throughout the lifespan.

Explain the function of the gamma motor system and its role in regulating the length of muscles

The gamma motor system functions to help regulate the length of an entire muscle. This feedback is used by the brain to help coordinate limb movement.

Describe the location, components, and functions of the mirror neuron system.

The mirror neuron system is located in the ventral premotor cortex. The neurons of the mirror neuron system are active when an individual engages in behavior as well as when the individual observes (or hears) the behavior. Another circuit of mirror neurons is located in the posterior parietal lobe. The proposed function of the mirror neuron system is to help an individual understand the actions of others.

indirect pathway (in basal ganglia)

The pathway that includes the caudate nucleus and putamen, the external division of the globus pallidus, the subthalamic nucleus, the internal division of the globus pallidus, and the ventral anterior/ventrolateral thalamic nuclei; has an inhibitory effect on movement

direct pathway (in basal ganglia)

The pathway that includes the caudate nucleus and putamen, the internal division of the globus pallidus, and the ventral anterior/ventrolateral thalamic nuclei; has an excitatory effect on movement

olfactory bulb

The protrusion at the end of the olfactory tract; receives input from the olfactory receptors

Explain the patterns of brain activity present during REM and slow-wave sleep.

The rate of cerebral blood flow during REM sleep is high in the extrastriate cortex but low in the stirate cortex and the prefrontal cortex. This activity reflects a lack of visual input in REM ( little or no activation of the striate cortex), but the presence of active visual hallucinations during dreaming (activation in the extrastriate cortex). Lack of prefrontal cortex activity likely reflects the lack of organization and planning the occur in dreams. Regional cerebral blood flow during slow-wave sleep is generally decreased through the brain compared to waking. However, some researchers have found localized increases in the visual and auditory cortexes, which are hypothesized to be the neural basis for the dreamlike imagery experienced during slow-wave sleep. Blood flow to the thalamus and cerebellum is decreased in slow-wave sleep.

Structure and function of the olfactory apparatus

The stimuli for olfaction are chemical molecules that are typically lipid soluble and organic. Olfactory receptor cells are bipolar neurons whose cell bodies lie within the olfactory mucosa that lines the cribriform plate. These neurons send information to the olfactory bulb and through the brain via olfactory tracts. Some information proceeds to the limbic system and integrates with gustatory information. Olfactory information is processes in the olfactory cortex. Regions of olfactory cortex contain olfactotopic maps.

Describe the pathways and functions of cortical regions involved in control of motor behavior

The supplementary motor area and the premotor cortex receive information from the parietal lobe and help to initiate movements through their connections with the primary motor cortex, which is responsible for causing movements of particular parts of the body.

Explain the functions of the motor association cortex (including the supplementary motor area and the premotor cortex) in planning and initiating movement.

The supplementary motor area is involved in well-learned behavior sequences. Neurons there fire at particular points in behavioral sequences, and disruption or damage impairs the ability to perform these sequences. the pre-SMA is involved in awareness of our decisions to make spontaneous movements. The premotor cortex is involved in learning and executing complex movements that are guided by arbitrary sensory information, such as verbal instructions.

umami

The taste sensation produced by glutamate

Identify the location and structure of taste buds and taste receptor cells.

The tongue contains the taste buds. Most taste buds are arranged around papillae and contain groups of receptor cells.

ventromedial group

The vestibulospinal tract, the tectospinal tract, the reticulospinal tract, and the ventral corticospinal tract