Fundamentals of Neuroscience Exam 3

Describe montane voles.

- Asocial and promiscuous. - Males uninvolved in offspring, females only briefly so. - mostly in separate nests. - less oxytocin (female) - less vasopressin (male)

What are the effects of cerebellar lesions?

- Ataxia: uncoordinated and inaccurate movements - Dyssynergia: decomposition of synergistic multijoint movements - Dysmetria: overshoot or undershoot target

Which type of muscles are innervated by the large middle region of the spinal cord?

- Axial muscles: trunk movement - Responsible for posture

Explain the noradrenergic locus coeruleus.

- Axons innervate cerebral cortex, thalamus, hypothalamus, olfactory bulb, cerebellum, midbrain, spinal cord - 12,000 neurons in LC - Regulation of attention, arousal, sleep-wake cycles, learning + memory, anxiety + pain, mood, brain metabolism

Describe cholinergic diffuse modulatory systems.

- Basal forebrain complex: core of telecephalon, medial and ventral to BG; participates in learning and memory - Pontomesencephalotegmental complex: utilizes ACh; regulates excitability of thalamic sensory relay nuclei

Describe the medullary reticulospinal tract.

- Begins in medulla. - Terminates in ipsilateral spinal cord.

What is the social role of vasopressin?

- Vasopressin antagonists prevent formation of pair bond relationships in males only - Agonists increase formation of pair bonds - Increases paternal activities

Explain the laminar organization of the cerebellum.

- Very distinctive laminar organization. - Purkinje cells receive input from granule cells and project to deep cerebellar nuclei. - Each purkinje cell is innervated by 100,000 granule cells. - Granule cells are packed incredibly densely; make up majority of neurons in entire brain.

Describe the vestibulospinal tract.

- Vestibular nucleus: receives direct input from vestibular system - Bilateral projection to cervical spinal cord: important for neck stability

Describe the monosynaptic stretch reflex arc.

- Weight placed on muscle. - Muscle lengthens. - Depolarization of Ia axons via mechanoreceptors. - Ia spiking depolarizes alpha motor neurons causing muscle contraction. - Monosynaptic because only one synapse separates the sensory input from the motor output.

How many spinal nerves do humans have?

31 pairs

How many genes on Y chromosome? (25k total in genome)

50

How many genes on X chromosome? (25k total in genome)

800

The sympathetic and parasympathetic systems cannot be ____________ at the same time, and one __________ the other.

Activated; inhibits

Define motor neuron pool.

All the alpha motor neurons that innervate a single muscle.

Both posterior parietal cortex and prefrontal cortex innervate which area?

Area 6, supplementary and premotor areas

Define myofibrils.

Cylindrical structure surrounded by sarcoplasm reticulum, which contains Ca2+ stores.

SRY gene

sex determining region of the Y chromosome

Hypothalamus commands in cold weather -->

shiver, goosebumps, turn blue

How do cocaine and amphetamine work?

- Affect dopaminergic and nordrenergic systems - Block catecholamine reuptake - Cocaine targets DA reuptake - Amphetamine blocks NE and DA reuptake and stimulates DA release

What are the types of motor units?

- All three muscle fibers coexist in most muscles, but each motor unit only contains one type. 1. Slow motor units: slowly fatiguing red fibers; these alpha motor neurons are small in diameter. 2. Fatigue-resistant (FR) fast motor units 3. Fast-fatigue (FF) fast motor units; these alpha motor neurons are physically larger.

Define enteric sensory neurons.

- Detect stretch and tension of GI tract. - Chemical status of stomach and intestinal contents. - Hormone levels in blood.

What is dopamine's role in motivation?

- Animals with destroyed dopamine fibers still appear to enjoy the taste of food if placed in mouth. - Dopamine-depleted animals lack motivation to seek food but enjoy it when available. - Experiment with monkey and juice reward - found that dopamine fires to anticipatory signals related to reward. - Dopamine is involved in reward prediction, behaviors that are better than expected are reinforced.

What is the somatic motor response of elevated leptin levels?

- Arcuate nucleus has direct projections to lateral hypothalamus - decreases feeding behavior

What do the motor maps represent?

- Activation of neurons appears to be related to activating ethologically relevant behaviors. - Motor maps are plastic; ex. microstimulation after cutting nerve that supplies whisker muscles resulted in forelimb or eye movements

Where does the primary motor cortex receive inputs from?

- Adjacent cortical areas - Thalamus: most from VLc (VLc is innervated by cerebellum; VLo innervated by BG)

What is the structure of the hypothalamus?

- 3 zones: lateral, medial, periventricular - Contains many small but functionally distinct nuclei

Explain ANS preganglionic neurotransmitters.

- ACh binds to nicotinic ACh receptor, evokes fast EPSP. - Ganglionic ACh activates muscarinic ACh receptor, causes slow EPSPs and IPSPs. - Some preganglionic terminals release NPY, VIP - trigger small EPSPs (changes responsively to the nAChR).

What are the contributions of the prefrontal cortex to movement?

- Abstract thought, decision making, and anticipating consequences of action. - Densely innervated by parietal lobes.

fMRI

- Blood oxy/deoxyhemoglobin changes with neuron activity - This changes the MRI signal over time - Blood-oxygen level dependent (BOLD) signal - Functional changes can be measured (active brain areas have more blood and light up) - has a slight time delay

Describe the communication between kidneys and the brain.

- Body can influence brain and vice versa. - By the release of chemicals that cross BBB. - By stimulation via nerves innervating visceral organs (vagus).

What are the contributions of both posterior parietal and prefrontal cortexes to movement?

- Both regions project axons to area 6 (SMA + PMA) - This sends much of descending information to muscles. - Area 6 is link between what is intended to happen and execution. - PET studies find evidence for this hierarchal organization of information flow.

Describe the study that showed hierarchal organization of movement information.

- By PET scans. - Subjects were asked to carry out a sequence of finger movements. a) Signals found in somatosensory, posterior parietal areas, prefrontal, area 6 + 4. - Subjects were asked to mentally rehearse the same action. a) Signals found in many regions but not area 4.

How are descending projections to spinal cord modulated?

- By subcortical input - Basal ganglia loop - Cerebellar loop

How do steroid hormones affect changes in cell?

- Can bind to cytoplasmic receptors in cell or bind surface receptors - Gives direct access to cell internals

Describe diabetes insipidus.

- Causes loss of ADH secreting cells. - Loss of vasopressin causes kidneys to pass too much water. - Stimulates drive to drink water.

Describe fluorescence microscopy.

- Cells are stained with fluorescent dyes. - UV Light is shined on the specimen. - Fluorescent substances absorb UV light and emit visible light. - 1-photon measurements are influenced by out of focus fluorescence. - 2-photon measurements can show individual neurons

Describe temperature regulation.

- Cells fine-tuned for constant temp, 98.7F - Transduce small changes in blood temp to changes in firing rate - Neurons for temperature homeostasis --> clustered in anterior hypothalamus - Humoral and visceral responses --> neurons in medial preoptic area of the hypothalamus - behavioral responses

Describe mirror neurons.

- Cells that fire when an organism observes a particular movement from someone else (grasping, holding, moving). - Seems to encode goal of motor act. - May be a part of extensive brain system for understanding actions and intentions of others. - Each cell has very specific preferences.

Describe insulin levels during each phase of eating.

- Cephalic: anticipation of food activates parasympathetic system which activates the pancreas, driving insulin release; blood glucose levels fall stimulating eating desire. - Gastric: GI hormones stimulate additional insulin release - Substrate: rising glucose levels drive insulin releases, which triggers satiety signals - Insulin can also act directly on neurons in hypothalamus to regulate feeding behaviors

Explain the disinhibitory circuit of the basal ganglia.

- Circuit is normally suppressive at rest. - Due to tonic inhibition from globus pallidus. - Excitatory input from cortex excites striatum, which inhibits globus pallidus, inhibiting the tonic inhibition. - Reduced inhibition on VLc, which increases output to cortex. - Net result is excitation.

What is the basal ganglia motor loop?

- Connection between basal ganglia and cortex. - Cortex --> striatum --> GP --> VLc --> Cortex - VLc (ventrolateral nucleus of thalamus) provides major input to SMA and PMA - Direct and indirect pathways.

In general, how do contracting muscles move a joint?

- Contraction of muscles can flex or extend a joint. - Muscles pull, not push. - Contraction of flexors pulls one end of the bone upward. - Contraction of extensor pulls the other end of the muscle up, causing the opposite end to pivot down.

What is the impact of reduced cortisol?

- Cortisol levels are self-regulated. - Prednisone is corticosteroid that treats many ailments. - Adrenal insufficiency: occurs due to sudden stopping of prednisone treatment. a) fools brain into reducing natural production of cortisol b) now there isn't a normal amount c) also caused by Addison's disease

How does the anterior pituitary mediate stress response?

- Cortisol mobilizes energy reserves and suppresses immune system. - Adrenal cortex produces cortisol, stimulated by multistep process that begins in hypothalamus.

Describe the pituitary.

- Cradled in a segment of bone at base of skull. - Provides broad signaling to rest of body. - Anterior + posterior lobes - Receives descending input from periventricular zone where neurohormones are released into bloodstream.

What is the impact of increased cortisol?

- Cushing's disease: caused by increased levels of ACTH; weight gain, immune suppression, sleeplessness - Chronic stress: daily injections of cortisol in rats caused dendrites to die

Describe the body's response to decreased leptin levels.

- Decreased leptin activates a distinct population of arcurate neurons that release NPY and AgRP. - Effects on energy balance: opposite effects of alpha-MSH and CART - Orexigenic peptides, which increase appetite a) NPY and AgRP inhibit secretion of TSH and ACTH. b) activate parasympathetic division of ANS. c) stimulate feeding behavior.

Describe androgen-insensitive genetic males.

- Defective androgen gene on x chromosome - Y chromosome generates male testes that is undescended; otherwise female appearance

What do lesions of both corticospinal and rubrospinal tracts cause?

- Deficits in separate movement of arms and hands - Can still grasp things, but loss of independent control of individual fingers/muscle groups. - Slower and less accurate voluntary movements.

Describe the concept of motivation as a driving force on voluntary behavior.

- Depends on many factors. - Probability and direction of behavior. - Varies with the driving force needed to perform the behavior.

What is the issue in the cerebellum caused by chronic alcohol abuse?

- Deterioration of anterior vermis - Area is important form movement in lower limbs - Individuals exhibit staggering gait but little impairment to arms or hands

Describe sexual dimorphisms.

- Differences in brain between males and females - May need neural mechanisms to control distinct body parts - Ex. tobacco hawk moth: male and female antenna different in size/structure, functionally specialized - Ex. zebrafish: males produce complex songs and females do not; song production is critical for attracting mate and establishing territory; males have differentiated trachea and have enlarged brain areas that control differentiated anatomy

Describe Huntington's disease.

- Disorder that decreases basal ganglia output, reducing inhibition on thalamus (i.e. increased activity). - Excess of movement.

Describe Parkinson's disease.

- Disorder that increases basal ganglia activity drive, increasing inhibition of the thalamus. - Scarcity of movement.

Explain hypothalamic control of the anterior pituitary.

- Distinct from posterior pituitary since it is an actual gland that contains hormone releasing neurons. - Releases many different hormones, controlled by hypothalamus. - Hormones modulate activity of may other glands, including thyroid, gonads, adrenal, mammary. - Parvocellular neurosecretory cells directly release neurohormones into capillary beds at top of pituitary. - Hypophysiotropic hormones run down capillary beds into anterior lobe. - These hormones bind to pituitary cells --> secrete or stop secreting hormones in response.

What is a population vector?

- Each cluster of lines that reflects the direction vector of many M1 neurons. - Average over many of them reveals that they specify the direction of the animal's arm movement.

How does reinforcement affect eating behavior?

- Electrical self-stimulation experiments identify brain sites of reinforcement (areas involved in dopamine release). - Placement of electrode strongly impacted the animals' motivation to lever press. - Rats would prioritize lever pressing over eating or drinking when electrode was in specific brain area. - drugs that block dopamine receptors reduce self-stimulation. - Dopamine reinforces particular behaviors.

Describe localization of function of motor movements.

- Electrical stimulation in specific areas resulted in physical movements of muscles. - Lesioning the same area causes muscle paralysis.

Describe the somatotopic map of motor control on the precentral gyrus.

- Electrical stimulation of these brain areas cause motor movements: primary motor cortex (area 4) - Analogous to how stimulating somatosensory cortex can evoke perception of touch. - Stimulation of higher areas causes more complex movements (ex. area 6)

What is the chemical cascade following elevated leptin levels?

- Elevated levels when body is full 1. Leptin activates arcuate neurons that release alpha-MSH and CART peptides. - Anorectic peptides: diminish appetite. - Injection of drugs that block these peptides increases feeding behavior. 2. Arcuate neurons project to regions that orchestrate coordinated response of humoral, visceromotor, and somatic responses.

Describe sexual behaviors of fruit flies.

- Encoded in genes - Male courts females with specific behaviors that are not taught - fru gene a) in males b) experimentally removing gene causes loss of courtship behaviors c) adding gene to female flies causes them to court - dsx gene a) expressed in both males and females b) important for sexual differentiation c) interacts with fru

Describe sexual dimorphisms of cognition.

- Evolutionary explanations - Possible role of hormonal differences - Larger differences between individuals than between sexes - Males and females are more alike than dissimilar

Explain the direct pathway through the basal ganglia.

- Excitatory connection from cortex to putamen. - Cortical activation: 1) Excited putamen (striatum) 2) Inhibits globus pallidus 3) Release VLc from inhibition - Activity in VLc boosts activity in SMA (movement-related cells). - Direct pathways enhances the selection of desired movements.

Describe the topography of the motor system.

- Exists within the spinal cord and local muscles. - Motor neurons controlling flexors lie dorsal to extensors (i.e., are located higher in the ventral horn). - Motor neurons controlling axial muscles lie medial to those controlling distal muscles.

Describe learning in the cerebellum.

- Experiment: disrupt magnitude of compensatory movements using special glasses. - Result: eyes move too far in relation to image (disturb vestibulo-ocular reflex) - Brain compensates over time and the eyes move in accordance with the altered size of visual field. - Cannot be learned if cerebellum is damaged.

Monogamy

- Female and male mate exclusively - 3% of mammalian species

What are alternative treatments for Parkinson's?

- Fetal tissue transplantation - Deep brain stimulation (unsure why it works)

Describe white muscle fibers.

- Fewer mitochondria, anaerobic metabolism. - Fatigue-resistant fast fibers (FR): white fibers with moderate strength and fast contraction. - Fast fatigue fibers (FF): fastest, strongest white fibers but rapidly fatiguing.

Describe the direction-selection of motor neurons.

- Fire optimally to movement in particular direction. - Still fires considerably to non-optimal directions. - Directional tuning is much broader than expected based on performance. - Motor output not likely to be encoded by individual neurons. - Direction vectors are plotting strength of tuning as length of arrow.

Describe cerebellum anatomy.

- Folia: sheets of shallow ridges - Lobules: deeper transverse fissure - ^ both increase surface area of cerebellum - Deep cerebellar nuclei: relay cerebellar cortical output to brain stem structures - Vermis: axial musculature, contributes to ventromedial pathways - Cerebellar hemispheres: limb movements, contributes to lateral pathways (what is intended vs. what has happened)

Describe the diffuse modulatory systems of the brain.

- Four systems with common principles. - Small set of neurons at core. - Neurons arise from brain stem. - One neuron influences many others (up to 250,000 postsynaptic targets). - Synapses release transmitter molecules into extracellular fluid - Can have diffuse activity

How do stomach stretching and CCK provide satiety signals?

- Gastric distension signals brain via the vagus nerve, activating neurons in nucleus of solitary tract - These neurons inhibit feeding - Works synergistically with cholecystokinin (CCK) released in intestines in response to certain foods - CCK: peptide that inhibits meal frequency and size; released by intestines and small amount of neurons in brain

Explain the differentiation of fetus.

- Gonads start out sexually undifferentiated for first 6 weeks of development. a) develop into testes or ovaries depending on whether fetus is XX or XY. b) presence of SRY produces testosterone. - Female development: if testosterone is not present, mullerian duct develops into female reproductive system. - Male development: SRY gene --> testosterone produced --> Wolffian duct develops into male reproductive system

Describe the periventricular zone of the hypothalamus.

- Groups of neurons that lie near the wall of the third ventricle. - Receives input from lateral and medial zones, brain stem, other areas. - Control autonomic nervous system, regulating sympathetic and parasympathetic innervation of visceral organs. - Neurosecretory neurons extend projections into pituitary gland.

T1 MRI image

- H atoms in non-aqueous environment - bone, white matter, fat look bright

T2 MRI image

- H atoms surrounded by water - fluid spaces, gray matter looks bright

Explain coding of movement in M1.

- Have monkey carry out motor task while observing firing pattern of neuron. - Put electrode into MC to record from individual M1 cells. - Task: move joystick towards light; measure effect of movement on neuron activity. - Result: motor neurons fire optimally to movement in a particular direction.

Explain the competition for activation of the MC4 receptor.

- High and low levels of leptin cause stimulation of alpha-MSH and AgRP from distinct arcuate nucleus populations. - These neuropeptides act on MC4 receptor in lateral hypothalamus but have opposite effects. - alpha-MSH: activation of MC4 receptor inhibits feeding - AgRP: inhibiting the MC4 receptor stimulates feeding

Describe the hierarchy of controls of the activity of the spinal cord.

- Highest level: strategy a) Coordinated by activity in neocortex and basal ganglia. b) Goal of the movement. - Middle level: tactics a) Motor cortex and cerebellum. b) Coordinates sequence of muscle contractions. - Lowest level: execution. a) Brainstem and spinal cord. b) Activation of the motor neurons and interneurons.

What is melanin-concentrating hormone?

- Hormone that has wide connections in the brain - Prolongs consumption - Injections into brain stimulates feeding behavior - Mutant mice missing MCH have elevated metabolic rate and are lean

What is orexin?

- Hormone with widespread cortical connections - Promotes meal initiation, triggers hunger

Describe gonadotropins.

- Hormones that are important for normal sexual development and function in men and women (ex. LH and FSH). - Released from anterior pituitary. - GnRH is released by hypothalamus: stimulates release of LH and FSH from anterior pituitary; hypothalamic control of this is controlled by many environmental factors. - In males: LH stimulates testosterone production; FSH aids sperm maturation - In females: LH + FSH cause estrogen secretion

Explain the biology of bonding in humans.

- Human plasma oxytocin levels increase during breastfeeding and sexual intercourse. - Mothers' brains more active when seeing pictures of their own children. - fMRI demonstrates strong reinforcing nature of partner and parental relationships; activation in brain areas associated with oxytocin and vasopressin receptors.

How does the elbow joint move?

- Humerus is bound by fibrous ligaments to the radius and ulna. - Brachialis along with biceps brachii cause flexion. - Triceps brachii and anconeus cause extension.

What are the types of responses by the hypothalamus when the body is cold?

- Humor and visceromotor response: body shivers, blood shunted away from body surface, urine production inhibited, body fat reserves mobilized - Somatic motor response: motivated behavior to seek out warmer conditions

What are the 3 components of neuronal responses in the hypothalamus?

- Humoral response: stimulates or inhibits release of pituitary hormones into bloodstream - Visceromotor response: adjusts balance of sympathetic and parasympathetic outputs - Somatic motor response: incites an appropriate somatic motor behavioral response, involves motivation

Describe pathway triggering osmotic thirst.

- Hypertonicity: increased concentration of blood solutes. - Sensed by OVLT neurons. - Water leaves cells by osmosis when blood becomes hypertonic. - Stimulates osmometric thirst, the motivation to drink water when thirsty. - Water loss causes OVLT neurons to change in spiking, which excites: a) ADH secreting cells in paraventricular hypothalamus b) other cells in lateral hypothalamus c) lesions of OVLT prevents behavioral response to dehydration

Explain central nervous system control of the ANS.

- Hypothalamic periventricular zone connections to brain stem and spinal cord nuclei; main regulator of ANS. - Nucleus of solitary tract: integrates sensory information from internal organs and coordinates output to autonomic brain stem nuclei - some functions of NST are maintained even when brainstem is disconnect from rest of brain

Describe pathway triggering volumetric thirst.

- Hypovolemia: decrease in blood volume; triggers volumetric thirst. - ADH: increases water retention and inhibits urine production. - Mechanoreceptors detect changes in blood volume and signal nucleus of solitary tract. - ANS stimulated with constricts arterioles, which helps to correct drop in BP.

How are muscle spindles different from golgi tendon organs?

- Ia activity from muscle spindle provides information about muscle length. - Ib activity from golgi tendon provides information about muscle tension.

Describe estradiol in hippocampus.

- Increase in hippocampal spine numbers coincides with female rat's peak fertility. - May play a role in changing reproductive needs. - Protective effects on neurons

Describe the parasympathetic division of the ANS.

- Rest and digest - stop sweating - slower HR, fall in BP - nerves from brainstem and spinal cord run to glands and smooth muscle - increased digestive function

Explain the indirect pathway through the basal ganglia.

- Inhibitory pathway that works in parallel with direct pathway. - Cortex directly projects onto sub thalamic nucleus, which provides excitatory projection to GPi. - Net effect of inhibition on thalamus. - Also includes pathway through GPe. - Indirect pathway antagonizes the activity of the direct pathway.

What are gamma motor neurons?

- Innervate intramural fibers (modified skeletal muscle fibers) inside muscle spindle. - Contrast with alpha motor neurons, which exclusively innervate extrafusal muscle fibers.

Describe serotonergic raphe nuclei.

- Innervates many of the same areas of noradrenergic system. - Together with noradrenergic system, comprise the ascending reticular activating system. - Particularly involved in sleep-wake cycles, mood. - Most active during wakefulness.

Name the functions of the autonomic nervous system.

- Innervates nearly every kind of tissue in every part of the body. - Muscle (smooth + cardiac) - Glands - Secretory glands: salivary, sweat, tears, mucus - Heart and blood vessels: blood pressure and flow - Lungs: meet oxygen demands - Liver, GI tract, pancreas: regulating digestive functions - Kidney, bladder, large intestine, rectum - Sexual responses - Immune system

Describe insulin's role in feeding.

- Insulin released by beta cells of pancreas and mediates transport of glucose into cells other than neurons. - Normally there is balance between blood glucose levels and insulin. - Blood glucose levels rise when insulin is low. - Blood glucose levels fall when insulin rises. - Insulin levels are controlled in each phase of eating.

How is L-dopa used as a treatment for Parkinson's?

- L-dopa: facilitators production of dopamine to alleviate some symptoms. - Helps to boost synthesis from the remaining dopamine neurons. - Stops working after a period of time since number of neurons continues to decrease. - L-dopa can cross the blood brain barrier while dopamine cannot. - L-dopa also increases production of peripheral dopamine, so usually co-administered with a drug that blocks peripheral synthesis of dopamine. - Still causes off-target side effects.

Describe red muscle fibers.

- Large number of mitochondria and enzymes. - Slow fibers (S): slow to contract, can sustain contraction.

Define alpha motor neurons.

- Large, multipolar lower motor neurons that evoke activity in skeletal muscles. - Directly trigger generation of force by muscles. - Each synapses with multiple fibers in the muscle.

Axons from the brain to the spinal cord descend along which two major pathways?

- Lateral pathways - Ventromedial pathways

Describe the input from cortex to lateral cerebellum.

- Layer 5 pyramidal cells from much of sensorimotor cortex project to pons which feeds cerebellum. - Massive innervation.

What does damage to spinal cord and brainstem circuits cause?

- Lesions cause somewhat unpredictable outcomes. - Partial or complete paralysis. - Muscles lose tone, reduce in size.

Describe the enteric division of the ANS.

- Lining of esophagus, stomach, intestines, pancreas, and gallbladder. - 2 networks: Myenteric plexus and Submucous plexus - Both networks contain visceral sensory and motor neurons that control the function of the digestive organs. - Sensory and motor neurons work together to digest food and transport nutrients to rest of body - Receives input indirectly from brain via sympathetic and parasympathetic divisions; can be suppressed by activation of sympathetic system

Describe serotonin levels during eating stages.

- Low in postabsoprtive period - Rise in anticipation of food - Spike during meal (mood elevation: rise in blood tryptophan and brain serotonin)

What are the descending output projections from the motor cortex?

- MC activates lower motor neurons via descending projections from neurons in layer 5. - Betz cells: pyramidal cells (large) in cortical layer 5 - Descend and can directly innervate single motor neurons, motor neuron pools, or interneurons - Branching projections means that the same Betz cell can provide reciprocal inhibition of opposing muscles to create synergistic movement

What are the neurohormones of the posterior pituitary?

- Magnocellular neurosecretory cells innervate the posterior pituitary and release two different neurohormones. - Oxytocin: lactation, suppress hypothalamic function. a) Oxytocin receptors are found all over the body, including in the mouth of neonates. - Vasopressin/ADH: regulates blood volume and salt concentration; acts on kidneys to modify water retention and urine production. a) lowered blood volume + pressure is detected by pressure sensitive cells and concentration-sensitive cells --> release of ADH which causes reduced urine production and water retention

Describe the study about the PMA.

- Monkey was trained that a juice reward required a specific arm movement to a target. - Monkey is given instruction of what the target is via instruction stimulus (PMA neuron begins to spike). - Variable delay until a trigger stimulus comes on telling them to move (PMA neuron stops spiking once action is completed). - Particular neuron was sensitive to movement of left target; would not have fired if instruction was to move to different direction. - Presumably a different neuron encodes for the other directions.

Where does the thalamus receive motor input from?

- Most from ventrolateral nucleus (VLc) - Heavily innervated by cerebellum

Describe spinal interneurons.

- Most input to alpha motor neurons mediated by spinal interneurons. - Synaptic inputs to spinal interneurons: 1) primary sensory axons 2) descending axons from brain 3) collaterals of lower motor neuron axons 4) other interneurons

What are the contributions of the postural parietal cortex to movement?

- Motor control relies on sensory information for proper function (posture, body position, spatial relationship to objects in environment). - Brain areas involved in integrating sensory + motor information. - Area 5: inputs from somatosensory cortex - Area 7: inputs from higher visual cortical areas - Lesions cause unusual deficits with regards to body image and spatial relationships.

Describe the distribution of motor neurons in the spinal cord.

- Motor neurons that provide fibers to one spinal nerve belong to a particular spinal segment. - Skeletal muscles are not evenly distributed throughout the body and spinal cord --> reflected in the spinal cord anatomy at different positions. - More muscles in arms and legs than in the trunk.

What is the evidence for a molecular signaling mechanism of weight?

- Mouse has mutation that causes obesity. - Hypothesis: a) mutant mouse has something in its blood that causes the obesity. b) mutant mouse is missing something that causes the obesity. - Experiment: fuse mutant mouse and wild type mouse together so they have common blood supply. - Result: mutant mice feeding behavior and obesity are greatly reduced. - Hypothesis b was correct: something missing was replaced (leptin)

What is the sliding-filament model?

- Muscle contraction occurs when thin filaments slide along the thick filaments. - Z lines are brought towards one another. - Sarcomere becomes shorter in length.

Each muscle contains hundreds of what?

- Muscle fibers - Each fiber is innervated by axons from CNS

Describe muscle fiber structure.

- Muscle fibers are enclosed in an excitable cell membrane called the sarcolemma. - The fibers contain myofibrils, which contract in response to action potentials. - Action potentials gain access to those Ca2+ stores via the T tubules. - Specialized coupling between the T tubules and sarcoplasmic reticulum. a) T Tubules have a cluster of 4 voltage-sensitive calcium channels. b) SR contains a calcium release channel. - AP causes conformational change in calcium release channel, causing calcium to flow into cytosol which causes myofibril to contract.

How does motor cortex activity relate to movement?

- Muscle force is proportional to firing rate - Individual cells fire best when moving in a specific direction - Many cells in M1 are active for every movement, but broadly tuned. - Activity of each cell represents a single vote. - Direction of movement: determined by a tally/averaging of votes, shown using population vectors. - Movement of direction encoded by collective activity of motor cortex neurons.

Describe the stretch reflex of muscles.

- Muscle has a tendency to pull back. - Not intrinsic property of muscle tissue (involves sensory feedback). - Cutting dorsal roots eliminates reflex and causes loss of muscle tone.

Describe enteric motor neurons.

- Muscle motility - Mucous and digestive secretions

Define the somatic motor system.

- Muscles and neurons that control muscles. - Responsible for generation of coordinated movements.

Why does increased voluntary force recruit additional motor units?

- Muscles have different motor unit sizes. - ex. leg muscles have innervation of 1 alpha motor neuron to ~1000 muscle fibers; fingers and eyes have smaller innervation ratios (~3 fibers per neuron). - Less convergence provides finer control. - Motor units are recruited in the order of smallest (light) to largest (heavy) --> why we have better control over lighter loads.

How does the sensorimotor system influence motor activity of the spinal cord?

- Nearly all motor control relies on sensory information for proper function. - Mental representation of body is generated from current sensory information. - Tactical decisions are made based on past sensory representations. - Sensory feedback helps maintain posture, current muscle positions.

Describe the sympathetic division of the ANS.

- Nerves from spinal cord run to chain ganglia then to glands and smooth muscle. - Mobilize energy, divert blood to muscle. - Increased heart rate + BP - Depressed digestive function - mobilized glucose reserves - fight or flee

What is the humoral response of alpha-MSH and CART peptides?

- Neurons in paraventricular hypothalamus are activated, releasing hypophysiotropic hormones - Stimulates secretion of TSH and ACTH from anterior pituitary - Hormones act on thyroid and adrenal glands to raise cellular and metabolic rate

Define motor unit.

- One alpha motor neuron and all the muscle fibers it innervates. - The specific neuron and which fibers it contacts define the motor unit.

What does the point-to-point pattern of communication refer to?

- One neuron activates ~one. - Many mechanisms designed to keep transmission constrained. - Sparse connectivity, brief transmission of neurotransmitters.

What does diffuse pattern of communication refer to?

- One neuron can activate many. - NT released into bloodstream. - One neuron can influence a network of neurons that has large effect. - One neuron can synapse onto many.

Describe preganglionic neurons of the sympathetic division.

- Originate in intermediolateral gray matter of spinal cord (middle 1/3 of spinal cord; thoracic + lumbar segments) - Axons are sent though spinal cord ventral root to sympathetic chain of collateral ganglia.

Describe preganglionic neurons of parasympathetic division.

- Originate in parts of brain stem and sacral spinal cord - Axons travel through cranial nerves to reach ganglia located relatively near target organ

Describe the corticospinal tract.

- Originates in cortex. - Majority comes from motor areas; some innervation from somatosensory areas. 1. Cortex - axon fibers descend through internal capsule. 2. Through base of cerebral peduncle. 3. Through medullary pyramid. - Pathway decussates at level of medulla and spinal cord. - Right motor cortex controls left side of body. 4. Enters spinal cord in dorsal-lateral region.

Describe the rubrospinal tract.

- Originates in the red nucleus (brainstem). - Red nucleus receives descending feedback from frontal cortex. - Almost immediately decussates and run mostly parallel with corticospinal tract.

How does LSD act?

- Seems to modulate serotonin flow - Close to structure of serotonin

Explain ANS postganglionic neurotransmitters.

- Parasympathetic: release ACh, local effect - Sympathetic: most release NE, far-reaching effects - Sympathomimetic: mimic or promote NE actions or inhibit muscarinic actions of ACh (ex. atropine, a muscarinic antagonist, causes pupil dilation) - Parasympathomimetic: mimic or promote muscarinic actions of ACh or inhibit actions of NE (ex. propranolol, a NE antagonist, slows heart rate and lowers BP)

What is the visceromotor response of elevated leptin levels?

- Paraventricular nucleus has direct projections to brainstem nuclei that control ANS - alpha-MSH and CART are directly released onto ANS nuclei in brainstem/spinal cord via direct projection from arcuate nucleus - Increases sympathetic NS tone - Increases body temperature

Explain Turner syndrome.

- Partial or complete absence of one X chromosome in female. - Most are miscarried but girls who survive exhibit a number of developmental disabilities. - Missing X chromosome in male is lethal.

Describe the mirror neuron study.

- Particular mirror neuron fired to grasping of food. - Fires regardless of whether the same monkey, different monkey, or human reaches for peanut. - Does not fire if peanut is grabbed with tweezers.

What is ghrelin?

- Peptide that is highly concentrated in stomach and gets released into bloodstream when hungry. - Stimulates appetite and feeding. - Activates NPY/AgRP-containing neurons in arcuate nucleus which bind to lateral hypothalamus and stimulate MCH + orexin, stimulating feeding behavior. - Removal of ghrelin secreting cells of stomach causes appetite loss

What role does dopamine have in the basal ganglia?

- Plays a critical role in BG circuitry. - Substantia nigra: contains one of the densest population of dopamine releasing neurons in the brain. - Degeneration of these neurons --> Parkinson's disease

Describe the pontine reticulospinal tract.

- Pontine reticular formation. - Passes through medullary reticula formation. - Terminates in ipsilateral spinal cord.

Explain brain changes with maternal and paternal behaviors.

- Pregnancy: a) rise in leptin levels b) hormonal changes in hypothalamus lead to leptin resistance - Somatosensory map plasticity in rats during lactation and nursing: non-pregnant female mice have sensory representation of nipples in S1 --> representation doubles when lactating - In males, interaction with offspring may alter brain structure (density of dendritic spines + increased vasopressin receptors)

Describe neuronal correlates of motor planning in the PMA.

- Premotor area thought to be important for getting ready to make an action. - Movement strategies are devised and held in memory until execution. - PMA appears to be holding the motor instruction in a sort of short-term storage until it is carried out. -

What causes development of a male vs female?

- Presence of SRY gene - Encodes testis-determining factor (TDF) a) causes development of testes and testicular hormones b) makes fetus develop as male c) no SRY --> female development

Describe the output of lateral cerebellum to cortex.

- Projects back to motor cortex via relay in ventral lateral thalamus. - Instructs motor cortex with respect to direction, timing, and force of movement. - Somewhat based on past experience.

How are proprioceptors involved in spinal control of motor units?

- Proprioceptors provide information about "body sense" (posture, body position). - Stretch receptors provide sensory feedback from muscle spindles. - Group1 sensory axons wrap around muscle fibers of spindle; detect changes in muscle length.

Describe leptin.

- Protein normally released by fat cells, regulates body mass by acting on hypothalamic neurons. - Leptin --> decreases appetite and increases energy expenditure - Leptin depletion incites adaptive responses to fight starvation. - Not a miracle cure for obesity because many obese individuals have a lot of leptin (but are less sensitive to it).

What do basal ganglia disorders do?

- Provide evidence that the basal ganglia is important for the initiation of willed movements. - Ex. Parkinson's, Huntington's

Which type of muscles are innervated by the cervical and lumbar segments of the spinal cord?

- Proximal muscles: shoulder, elbow, pelvis, knee; responsible for locomotion - Distal muscles: hands, feet, digits; responsible for object manipulation

Describe MRI.

- Put subject in big magnetic field - Transmit radio waves into subject - Turn off radio wave transmitter - Receive radio waves re-transmitted by subject - Hydrogen atoms relax at different rates in different tissues - Convert data to image

What is the ready/set/go description of planning and execution of movement by the cerebral cortex?

- Ready: need mental representation of current body position and its relationship to things in environment; parietal and frontal lobes - Set: movement strategies are devised and held until execution; lateral region --> premotor area + medial region --> supplementary motor area - Go: activating motor program to accomplish goal; area 4/M1 (primary motor cortex) + area 6 (higher motor area)

Give examples of inhibitory motor input.

- Reciprocal inhibition: contraction of one muscle set accompanied by relaxation of antagonist muscle (VOR reflex). - Stretch reflex: Ia proprioceptive sensory neurons synapse on inhibitory interneuron to inhibit the antagonist muscle.

What are the two types of muscle fibers?

- Red muscle fibers (slow) - White muscle fibers (fast)

What is the flexor withdrawal reflex?

- Reflex arc used to withdraw limb from averse stimulus. - Activates excitatory interneuron to withdraw leg.

Describe the basal ganglia.

- Selection and initiation of willed movements. - Composed of several brain areas: a) Striatum: input to basal ganglia; caudate nucleus + putamen b) Globus pallidus: output from basal ganglia; includes two distinct compartments, GPi and GPe c) Ventral lateral nucleus of thalamus: receives output from GP, projects to cortex d) Subthalamic nucleus e) Substantia nigra: major source of dopaminergic neurons

Describe hormonal control of sex.

- Sex hormones: steroids released from endocrine glands (ovaries + testes); endocrine glands regulated by pituitary. - Men: high concentration of androgens (testosterone) - Women: high concentration of estrogens (estradiol) - males and females have both, but more of one than the other.

Describe sexual dimorphisms in the CNS.

- Sexual dimorphic nucleus: located in preoptic area of hypothalamus; 5-8x larger in males - Possibly true in humans: INAH (interstitial nuclei of the anterior hypothalamus) - Male and female brains are more alike than they are different. - Dimorphisms reflect differential growth due to distinct patterns of gonadal steroids.

What do lesions of corticospinal tracts cause?

- Similar level of loss but apparent recovery if rubrospianl tract is intact. - Subsequent rubrospinal lesion reverses recovery.

What is the influence of a single cortical motor neuron on muscle activity?

- Single cortical motor neuron can drive activity in multiple muscles (muscle field) - Size of muscle field in wrist is 2-3 muscles per upper motor neuron

What is the arcuate nucleus of hypothalamus?

- Sits near base of third ventricle. - Important for the control of feeding. - Leptin released by fat cells, circulate in blood and can bind to leptin receptors in arcuate nucleus. - releases peptides that modulate feeding behaviors.

What are the types of muscle?

- Smooth (involuntary control): digestive tract, arteries, related structures - Striated: a) cardiac muscle (involuntary control) b) skeletal muscle (voluntary control): bulk of body mass; voluntary movement, speech, eye movement, etc.

Describe prairie voles.

- Social and monogamous, exhibit pair bonding. - Lifelong partners. - Dual care of offspring. - Spend much of time in one nest. - more oxytocin (female) - more vasopressin (male) - levels rise during copulation

How are muscles innervated by lower motor neurons?

- Somatic musculature is innervated by lower motor neurons in the ventral horn (contrast with somatic sensory system which innervates the dorsal horn). - Axons of lower motor neurons bundle together to form the ventral roots. - Dorsal and ventral roots join at the notches between vertebrae; contain both sensory and motor fibers.

What does damage to motor cortex cause?

- Some paralysis. - Loss of sensory signals to alpha motor neurons can result in unusual reflexive activity. - Spasticity, Babinski sign

What does MPTP-induced Parkinson's mean?

- Street chemists screwed up synthesis of narcotics. - Accidentally made MPTP. - Individuals who took it got Parkinson's. - MPTP taken up by dopamine cells and is metabolized into MPP, which is toxic as it interrupts ATP production.

Describe dopaminergic substantia nigra and ventral tegmental area.

- Substantia nigra: axons project to striatum; facilitates initiation of voluntary movements - VTA: innervates circumscribed region of telencephalon; mesocorticolimbic dopamine system: dopaminergic projection from midbrain

Describe the tectospinal tract.

- Superior colliculus: receives direct input from retina. - Crosses immediately and descends to spinal cord.

Describe neuronal correlates of motor planning in the SMA.

- Supplementary motor area is thought to be involved in the planning stage of motor activity (planned, practiced, trained movements). - Cells in SMA spike prior to the execution of the behavior. - Important for coordinated activity of the two hands.

Describe the experiment about if the property of the alpha neuron drove the specific nerve fiber or vice versa.

- Switched nerve input --> switch in muscle phenotype. - Fast muscle acquired many properties of slow muscle, and vice versa. - Muscles are also strongly influenced by experience. - Showed that property of the alpha neuron drives the specific muscle fiber.

Describe Huntington's disease in depth.

- Symptoms: chorea, hyperkinesia, dyskinesia, dementia, personality disorder - Caused by net increase in output of the basal ganglia due to decreased inhibition to thalamus. - Loss of neurons in caudate nucleus, putamen, globus pallidus. - Cortical degeneration primarily responsible for dementia and personality changes

Describe control of contraction by alpha motor neurons.

- The force of muscle contractions are controlled by graded mechanisms. - Muscle contraction happens by varying the firing rate of motor neurons --> releases ACh. - Postsynaptic potential causes muscle switch (rapid sequence of contraction/relaxation). - Twitch summation causes increased muscle tension --> more ACh.

Describe Parkinson's disease in depth.

- Trouble initiating willed movements due to increased inhibition of the thalamus by BG. - Causes hypokinesia, bradykinesia, akinesia, rigidity, and tremors. - Caused by net reduction in output of BG, due to degeneration of substantia nigra dopaminergic neurons. - Direct pathway: reduced excitation of inhibition on GPi; higher inhibition on thalamus.

What are the two main types of movement?

- Unconscious reflexes like pupil dilation - Voluntary movements that are motivated to satisfy a need

Briefly describe the lateral pathways.

- Under direct cortical control. - Voluntary movement of distal musculature. a) Corticospinal tract (pyramidal tract) b) Rubrospinal tract (red nucleus)

Describe sarcomere.

- Unit within a myofibril consisting of two Z lines and the myofibril. - Z lines: division of myofibril into segments by disks. - Thin filaments: series of bristles anchored to Z lines. - Thick filaments: between and among thin filaments.

Describe sexual orientation.

- Unrelated to activational effects of hormones in adults. - May be correlated with INAH-3 size differences (larger in heterosexual man)

polyandry

Female mates with many males

Describe golgi tendon organs.

- additional proprioceptive input, monitors muscle tension. - Located at junction between muscle and tendon; innervated by mechanosensitive Ib axons. - Muscle contraction causes collagen to squeeze Ib axons. - Oriented in series. - Respond to increased tension on muscle. - Transmits information to spinal cord. - Ib axons enter spinal cord, branch and synapse on Ib inhibitory interneurons. - These interneurons can directly modulate local alpha motor neurons.

Why doesn't estrogen from mother cross place and masculinize all fetuses?

- alpha-fetoprotein in fetal blood binds estrogens and protects female fetus from masculinization - females missing this protein are infertile

activational effects of hormones

- behaviors - tend to be temporary

Describe energy balance.

- brain needs a constant glucose supply. - prandial state: the state right after having eaten a meal, body is full of nutrients. a) anabolism: assembly of glycogen and triglycerides as energy storage - post absorptive state: fasting between meals a) catabolism: glycogen and triglycerides are broken down to provide body with continuous supply of energy - if intake exceeds usage, adiposity increases --> obesity - if intake is too low, adiposity decreases --> starvation - many regulatory mechanisms that modulate this seemingly straightforward process

organizational effects of hormones

- development, anatomy - tend to be irreversible - ex. masculinization of NS due to surge of testosterone --> increased estrogen

Describe congenital adrenal hyperplasia.

- in genetic females - abnormally large adrenals overproduce androgens - external genitals intermediate between clitoris and penis

autonomic PNS

- innervates internal organs, blood vessels, glands - nerves that unconsciously monitor and run organs, glands, etc. - sympathetic: fight or flight - parasympathetic: rest and digest

somatic PNS

- innervates skin, joints, muscles - nerves that allow us to sense things and move our bodies - dorsal root ganglia: clusters of neuronal cell bodies outside the spinal cord that contain somatic sensory axons

What are prostaglandins?

- local hormones produced by most body tissues - prostaglandin is synthesized via enzyme COX - COX inhibitors --> reduced copulatory behavior in male rats; male-like copulatory behaviors in female rats

Describe maintenance of body weight in animals.

- maintain relatively narrow range of body weight - animals fed reduced calorie diet lose weight - animals force fed gain weight - lipostatic hypothesis: the brain is involved in regulating intake to maintain optimal conditions

peripheral nervous system (PNS)

- nervous system outside brain and spinal cord - fibers that innervate spine, visceral function + everything else

Explain activational effects of sex hormones.

- temporary modifications in brain organization and structural changes in neurites. - men: anticipation of sex --> rise in testosterone, fall in testosterone associated with decreased sexual interest - women: rise in estrogen --> increased sexual interest - ongoing fluctuations in these hormones constantly impact our brain

What is the body's response to decreased body fat?

1. Leptin decreases 2. Stimulates release of NPY and AgRP from arcuate nucleus 3. NPY and AgRP bind to hypothalamic neurons which release MCH and orexin 4. Feeding behavior is stimulated

What are the differences between somatic and ANS circuits?

-Both control motor systems (somatic: modulation is fast and precise; autonomic: slow widely coordinated and graded control) - Somatic system controls targets via a monosynaptic pathway (cell bodies controlling motor neurons lie within spinal cord or brain stem) - ANS controls targets via disynaptic pathway (cell bodies controlling motor neurons lie in ganglia outside CNS)

What are the three phases of feeding behavior?

1) Cephalic phase: the hunger phase in which sensory information drives anticipatory processes to prepare for eating. - Sights and smells can trigger ANS to prepare for eating. - Parasympathetic and enteric NS trigger salivation and digestive secretions. 2) Gastric phase: includes the processes of eating food and starting to feel full 3) Substrate phase: process by which nutrients are absorbed and moved into the bloodstream

What effects does dopamine release onto striatum have?

1) Direct pathway: enhances cortical inputs. - Provides excitatory signal to cells in putamen. - Net result of reducing inhibition onto thalamus. 2) Indirect pathway: suppresses cortical input. - Inhibits neurons in striatum that sends inhibitory outputs. - Net result of increasing inhibition on thalamus.

Describe the steps of the sliding-filament model.

1. Actin binding sites for myosin are blocked at rest. 2. Binding of Ca2+ to troponin causes tropomyosin to shift position, exposing binding sites. 3. Myosin filament binds to actin. 4. Myosin heads undergo conformation change, causing a pivot which causes filaments to slide. 5. ATP binds to myosin heads, causing them to disengage. - Loss of ATP prevents this detachment (muscle stiffening). 6. Repetition of process walks myosin heads along filament. - Contraction occurs as long as Ca2+ and ATP are available.

Describe muscle excitation.

1. Action potential occurs in alpha motor neuron. 2. ACh is released by axon terminal at the neuromuscular junction. 3. Nicotinic receptor channels open in the sarcolemma, causing depolarization. 4. Voltage-gated Na+ channels open, an AP is generated in the muscle fiber, which sweeps down the sarcolemma into the T-tubules. 5. Depolarization of the T-tubules causes Ca2+ release from the SR.

Describe intrafusal muscle contraction.

1. At rest, Ia axon provides baseline information about the current state of stretch. 2. When a muscle is stretched, the intramural fibers relax reducing Ia axon action potentials. - Muscle contraction causes a loss of proprioceptive information about muscle length. 3. Gamma motor neurons compensate for this change; their activation brings the two ends of the muscle spindle together.

Describe muscle contraction.

1. Ca2+ binds to troponin. 2. Tropomyosin shifts position, myosin binding sites on actin are exposed. 3. Myosin heads bind actin. 4. Myosin heads pivot. 5. ATP binds to each myosin head, disengaging from actin.

What is an example of a spinal interneuron circuit that can generate rhythms despite constant input?

1. Channels are closed. 2. Glutamate depolarizes cell, bringing in Na/Ca2+, causing spikes. 3. Ca2+ activates calcium-activated potassium channel. 4. K+ leaves cell, repolarizing. 5. K+ channel closes. 6. Repolarize and repeat.

Describe muscle relaxation.

1. EPSPs end, sarcolemma and T-tubules return to resting potentials. 2. Ca2+ is sequestered by SR via an ATP-powered calcium pump. 3. Myosin binding site son actin are covered by tropomyosin; binding is prevented.

What is the body's response to increased body fat?

1. Leptin increases 2. Release of alpha-MSH and CART from arcuate nucleus 3. alpha-MSH and CART bind to MC4 receptor in hypothalamus 4. Feeding behavior inhibited and metabolism increased

What is the process of ADH?

1. Lowered blood volume and pressure. 2. Release of renin from kidneys. 3. Renin converts angiotensinogen to angiotensin I. 4. Angiotensin II has direct effects on kidney and blood vessels, also stimulates subfornical organ (brain structure lacking BBB) 5. Subfornical cells project into hypothalamus, activating vasopressin cells + other neurons in lateral hypothalamus critical for stimulating thirst. 6. Vasopresin acts on kidneys to increase water retention and lowered urine production.

Describe the steps of muscle excitation-contraction.

1. Muscle contraction. 2. Alpha motor neurons release ACh. 3. ACh produces large EPSP in muscle fiber. 4. EPSP evokes muscle action potential. 5. AP triggers Ca2+ release. 6. Fiber contracts. 7. Ca2+ reuptake. 8. Fiber relaxes.

How does the anterior pituitary release cortisol?

1. Periventricular hypothalamus parvocellular neurons secrete coricotropin-releasing hormone into portal circulation --> travels down anterior pituitary (15s). 2. Stimulates release of adrenocorticotropic hormone (ACTH), released into bloodstream by anterior pituitary. 3. ACTH stimulates cortisol release from adrenal cortex (minutes).

What are the inputs to alpha motor neurons?

1. Sensory input from muscle spindles: dorsal root ganglion cells that provide information about muscle tone/length. 2. Upper motor neurons in motor cortex and brainstem: initiation and control of voluntary movement. 3. Interneurons in spinal cord: generates spinal motor programs.

In intrafusal muscle fibers, how are deviations from set point detected?

By Ia sensory axon endings, compensated by alpha motor neurons activating on extrafusal muscle fibers.

50 arm muscles originate from which spinal segments?

C1-T1

Define motor programs.

Circuits that evoke specific patterns of activity to coordinate movement.

What are 3 X-linked diseases?

Color blindness, hemophilia, Duchenne muscular dystrophy

Alpha motor neuron activation --> __________ Ia sensory neuron output

Decreases

Why are laser scanning techniques limited?

Due to speed of scanning, will always lag behind slightly

Hunger can alter _______, which influence feeding desires by modifying olfactory sensory gain.

Endocannabinoids

In cultured hypothalamic tissue, addition of _______ caused dramatic increase in neurite formation.

Estrogen

Explain Klinefelter's syndrome.

Extra X chromosome in male. No obvious indications.

Desire to eat is increased by...

High orexigenic and low satiety signals

Which brain region is involved in homeostasis?

Hypothalamus

What did Douglas Coleman hypothesize regarding animal obesity?

If a circulating factor controlled obesity, he could test for it by linking the blood supply of two animals.

Where are leg muscles controlled?

In lumbar enlargement (L1-S3)

Gamma motor neuron activation --> _________ Ia sensory neuron output

Increases

What does activating the basal ganglia do?

Increases activity in motor cortex by reducing inhibition on the thalamus.

Describe the knee-jerk reflex.

Knee tapping causes quadriceps muscle to stretch, causing activation of the Ia axon during leg movement.

In montane voles, why does giving vasopressin or oxytocin not result in pair bonding?

Lack of pair-bonding in response to vasopressin or oxytocin is related to lack of binding sites in the brain.

Which motor pathways are voluntary?

Lateral pathways

Treating mutant obese mice with _________ reversed their obesity.

Leptin (a protein)

Define homeostasis.

Maintenance of the body's internal environment within a narrow physical range.

polygyny

Male mates with many females

Brain --> control of __________ __________ in spinal cord

Motor programs

Where does SMA innervate?

Motor units in the spinal cord and area 4 (motor cortex)

Spinal cord --> control of coordinated _________ _________

Muscle contraction

antagonist muscles

Muscles that pull in opposite directions.

synergist muscles

Muscles that work together to produce a given movement.

Where are estradiol sensitive neurons heavily expressed?

Pituitary and hypothalamus

What area of Phineas Gage's brain was damaged?

Prefrontal cortex

What is the net result of the direct BG pathway?

Provides net excitation onto cortex via reduced inhibition onto thalamus, increasing thalamic output and helping to select appropriate motor programs.

What is the net result of the indirect BG pathway?

Provides net reduced drive onto cortex, decreasing thalamic output and helping to suppress competing/inappropriate motor programs.

Branching projections from the same Betz cell can provide what?

Reciprocal inhibition of opposing muscles to create synergistic movement.

Where does PMA innervate?

Reticulospinal pathways and some connections with motor cortex

What is the spinal cord control of muscle contraction process?

Sensory inputs --> local circuit neurons (sensorimotor integration and central pattern generation) --> motor neuron pools (lower motor neurons) --> skeletal muscles

What type of muscle makes up the somatic motor system?

Skeletal muscle

Where does the circuitry for walking reside?

Spinal cord

What is the social role of oxytocin?

Stimulates maternal behavior with pups

What is the direct projection from the retina to hypothalamus?

Suprachiasmatic nucleus

Describe the process of temp regulation during fall in temperature.

TSH released by anterior pituitary --> TSH stimulates release of thyroxin from thyroid gland --> increase in cellular metabolism

Which motor pathways are reflexive?

Ventromedial pathways

Why do X-linked conditions appear more frequently in males than in females?

The extra X compensates for small defects on the other in women.

The activity of different muscles are directly activated by what?

The spiking of cortical motor neurons

female genotype

XX

male genotype

XY

Briefly describe the ventromedial pathways.

a) Vestibulospinal tract: originates in vestibular nuclei; head balance, head turning b) Tectospinal tract: originates in superior colliculus; provides an orienting response to things in environment c) Pontine reticulospinal tract: facilitates extensors in lower limbs - maintains standing posture; enhances antigravity reflexes. d) Medullary reticulospinal tract: liberates antigravity muscles from reflex control.

Lesions to lateral hypothalamus -->

anorexia

central nervous system (CNS)

brain and spinal cord

enteric NS

complex network that runs gut, food digestion.

Lesions to ventral hypothalamus -->

obesity

Hypothalamus commands in hot weather -->

turn red, sweat