Chemical control of brain and behaviour

Question 1

What are the 3 components of the nervous system that operate in expanded space and time?

Answer 1

-secretory hypothalamus –> directly secrete chemicals into the bloodstream.

-autonomic nervous system –> controlled neurally by the hypothalamus, ANS simultaneously controls the responses of many internal organs, blood vessels and glands

-The third component exists throughout the entirety within the CNS and consists of several related cell groups that differ with respect to the transmitter they use. All these cell groups extend their spatial reach with highly divergent axonal projections and prolong their actions by using metabotropic postsynaptic receptors. –>members of this component of the NS are called the diffuse modulatory system of the brain –> diffuse system regulates level of arousal and mood

Question 2

where does the hypothalamus sit? and size

Answer 2

Below the thalamus, along the walls of the third ventricle. –> connected by a stalk to the pituitary gland which dangles below the base of brain, just above mouth

makes up less than 1% of brains mass

Question 3

what does the hypothalamus integrate?

Answer 3

-somatic and visceral responses in accordance with the needs of the brain
-a lesion in hypothalamus –> disruptions of widely dispersed bodily functions

Question 4

what is homeostasis with respect to the hypothalamus?

Answer 4

-the maintenance of the body’s internal environment within a narrow physiological range –> hypothalamus regulates these levels

Question 5

what are the functional zones of the hypothalamus?

Answer 5

-each side has 3 functional zones:
-lateral, medial and periventricular

Question 6

describe the connections of the functional zones of hypothalamus

Answer 6

the lateral and medial zones have extensive connections with the brainstem and the telencephalon and regulate certain types of behaviour, the periventricular zone receives much of its input from the other 2 zones

Question 7

where does the periventricular zone of the hypothalamus lie?

Answer 7

-lie right next to the wall of the third ventricle

Question 8

what cells groups constitute the periventricular zone of the hypothalamus?

Answer 8

-suprachiasmatic nucleus (SCN) –> lies just above the optic chiasm –> these cells receive direct retinal innervation and function to synchronize circadian rhythms with daily light-dark cycle

-other cells in this zone control the ANS and regulate the outflow of the sympathetic and parasympathetic innervation of the visceral organs

-the third group, called neurosecretory neurons, extend axons down toward the stalk of the pituitary gland –> command our attention

Question 9

describe the pituitary gland in a living brain

Answer 9

-in a brain lifted out of the head, pituitary gland dangles below the base of the brain

-in a living brain pituitary gland is held in a cradle of bone at the base of the skull

Question 10

why does the pituitary gland require this level of protection ?

Answer 10

it is the “mouthpiece” from which much of the hypothalamus “speaks” to the body

Question 11

what are the lobes of the pituitary gland?

Answer 11

posterior and anterior –> hypothalamus controls the 2 lobes in different ways

Question 12

describe the magnocellular neurosecretory cells of the hypothalamus

Answer 12

-largest of the hypothalamus neurosecretory cells
-extend axons down the stalk of the pituitary gland and into the posterior lobe
- (ernst and Berter Scharrers) –> these neurons release chemical substances directly into the capillaries of the posterior lobe –> the substances releases into the blood by neurons are called neurohormones.

Question 13

what do the magnocellular neurosecretory cells release?

Answer 13

-two neurohormones into bloodstream, oxytocin and vasopressin

Question 14

describe oxytocin

Answer 14

-peptide containing a chain of 9 amino acids
-levels rise during sexual or intimate behaviours and promote social bonding
-crucial role during final stages of childbirth by causing uterus to contract and facilitating delivery of newborn –>also stimulates ejections of milk from mammary glands

Question 15

describe vasopressin (aka antidiuretic hormone (ADH))

Answer 15

-peptide containing a chain of 9 amino acids
-regulates blood volume and salt concentration
-when body is deprived of water, the blood volume decreases and blood salt concentration increases –> these changes are detected by pressure receptors in the cardiovascular system and salt concentration-sensitive cells in the hypothalamus, respectively
-vasopressin-containing neurons received information about these changes and respond by releasing vasopressin, which acts directly on the kidneys and leads to water retention and reduced urine production

Question 16

under conditions of lowered blood volume and pressure, communication between brain and kidneys…

Answer 16

occurs in both directions

Question 17

what happens when there is low blood pressure?

Answer 17

Kidneys secrete an enzyme into the blood called renin. Elevated renin sets off a sequence of biochemical reactions in the blood. Angiotensinogen, a large protein released from the liver, is converted by renin to angiotensin I, which breaks down further to form another small peptide hormone, angiotensin II. Angiotensin II has direct effects on the kidney and blood vessels, which help increase blood pressure.

Question 18

describe angiotensin II and subfornical organ

Answer 18

angiotensin II in the blood is also detected by the subfornical organ, a part of the telencephalon that lacks a blood-brain barrier. Cells in the subfornical organ project axons into the hypothalamus where they activate, among other things, the vasopressin-containing neurosecretory cells. In addition, the subfornical organ activates cells in the lateral area of the hypothalamus, somehow producing an overwhelming thirst that motivates drinking behaviour.

Question 19

what part of the pituitary is the gland?

Answer 19

anterior lobe is the actual gland

Question 20

what does the anterior lobe of the pituitary gland do?

Answer 20

Synthesize and secrete a wide range of hormones that regulate secretions from other glands throughout the body –> together constituting the endocrine system

Question 21

what does the pituitary hormones act on?

Answer 21

gonads, thyroid glands, adrenal glands and mammary glands

Question 22

what controls the anterior pituitary?

Answer 22

the secretory hypothalamus, under the control of neurons in the periventricular area called parvocellular neurosecretory cells.

–anterior pituitary was traditionally describe as body’s “master gland” –> but anterior pituitary controlled by hypothalamus so hypothalamus is true master gland of the endocrine system

Question 23

how does the neurons in the periventricular area of the hypothalamus communicate with the anterior lobe?

Answer 23

-the parvocellular neurosecretory cells of the periventricular area do not extend all the way down into the anterior lobe, instead communicate with their targets via the bloodstream
-these neurons secrete what are called the hypophysiotropic hormones into a uniquely specialised capillary bed at the floor of the third ventricle
-these tiny blood vessels run down the stalk of the pituitary and branch in the anterior lobe –> this network of blood vessels is called the hypothalamo-pituitary portal circulation
-hypophysiotropic hormones secreted by the hypothalamic neurons into the portal circulation travel downstream until they bind to specific receptors on the surface of pituitary cells –> activation of these receptors causes the pituitary cells to either secrete or stop secreting hormones into the general circulation

Question 24

Where are the adrenal glands located and what do they consist of?

Answer 24

-located above the kidneys
-consist of two parts, a shell called the adrenal cortex and a centre called the adrenal medulla

Question 25

what does the adrenal cortex produce?

Answer 25

a steroid hormone, cortisol

Question 26

what happens when cortisol is released into bloodstream?

Answer 26

-cortisol acts throughout the body to mobilise energy reserves and suppress the immune system, preparing us to carry on in the face of life's various stresses

Question 27

what is a good stimulus for cortisol release?

Answer 27

-stress, ranging from physiological stress, such as a loss of blood, to positive emotional stimulation, such as falling in love; to psychological stress, such as anxiety over an upcoming exam

Question 28

What cells determine whether a stimulus is stressful or not?

Answer 28

-parvocellular neurosecretory cells that control the adrenal cortex determine whether a stimulus is stressful or not --> as defined by the release of cortisol

Question 29

where do parvocellular neurosecretory cells lie?

Answer 29

-in periventricular hypothalamus

Question 30

what do parvocellular neurosecretory cells release?

Answer 30

a peptide called corticotropin hormone (CRH) into the blood of the portal circulation

Question 31

where does CRH travel to after being secreted into the portal circulation by the parvocellular neurosecretory cells?

Answer 31

-travels the short distance to the anterior pituitary, where, within about 15 seconds, it stimulates the release of corticotropin, or adrenocorticotropic hormone (ACTH)

Question 32

what happens after ACTH is released?

Answer 32

ACTH enters the general circulation and travels to the adrenal cortex where, within a few minutes, it stimulates cortisol release

Question 33

describe cortisol in blood

Answer 33

-blood levels of cortisol are, to some extend, self-regulated -cortisol is a steroid, a class of biochemicals related to cholesterol --> is a lipophilic ("fat-loving") molecule, which dissolves easily in lipid membrane and readily crosses the blood-brain barrier

Question 34

How does the brain ensure cortisol levels don't get to high?

Answer 34

in the brain cortisol interacts with specific receptors that lead to inhibition of CRH release, thus ensuring that circulating cortisol levels don't get too high

Question 35

describe prednisone

Answer 35

-synthetic form of cortisol -frequently used to suppress inflammation, but when administered for several days, the prednisone circulating in the bloodstream fools the brain into thinking that naturally release levels of cortisol are too high and shutting down the release of CRH and the adrenal cortex

Question 36

what happens when there is an abrupt discontinuation of prednisone?

Answer 36

-does not give the adrenal cortex enough tie to ramp up cortisol production and can thus result in what is called adrenal insufficiency

Question 37

describe adrenal insufficiency

Answer 37

-can occur as a result of abrupt cessation of prednisone -among the symptoms of adrenal insufficiency are severe abdominal pain and diarrhoea, extremely low blood pressure, and changes in mood and personality. -feature of rare disorder called Addison's disease --> degeneration of adrenal gland

Question 38

What is Cushing's disease?

Answer 38

-pituitary gland dysfunction that results in elevated levels of ACTH and consequently, cortisol. -symptoms include rapid weight gain, immune suppression, sleeplessness, memory impairment, and irritability. -symptoms of Cushings disease is common side effects for prednisone treatment

Question 39

describe the myriad behavioural changes that are caused by the fluctuation of cortisol levels

Answer 39

-the myriad behavioural changes caused by this different level of cortisol may be explained by the fact that neurons with cortisol receptors are found widely distributed in the brain, not just in hypothalamus. in these other CNS locations, cortisol has been shown to have significant effects on neurons activity. Thus, we see that the release of hypophysiotropic hormones by cells in the secretory hypothalamus can produce widespread alterations in the physiology of both the body and the brain

Question 40

what controls the autonomic nervous system?

Answer 40

hypothalamus

Question 41

What responses are produced by the sympathetic division of the ANS?

Answer 41

(not all the responses) -increased HR and BP, depressed digestive functions and mobilised glucose reserves

Question 42

What responses does the parasympathetic division of the ANS produce?

Answer 42

returning your body back to normal levels -HR slows, BP drops, digestive functions work harder, and stop sweating

Question 43

describe the speed and accuracy of the ANS compared to the somatic motor system

Answer 43

-unlike the somatic motor system, whose alpha motor neurons can rapidly excite skeletal muscles with pinpoint accuracy, the actions of the ANS are typically multiple, widespread and relatively slow -in addition, unlike the somatic motor system, which can excite its peripheral targets, the ANS balances synaptic excitation and inhibition to achieve widely coordinated and graded control

Question 44

what comprises the total neural output of the CNS?

Answer 44

-the somatic motor system and the ANS

Question 45

what task does the ANS have?

Answer 45

-complex task of commanding every other tissue and organ in the body that is innervated with the exception of the somatic motor system

Question 46

what are similarities and differences between the somatic motor system and the ANS

Answer 46

Similarity-both systems have upper motor neurons in the brain that send commands to lower motor neurons, which actually innervate the target structures outside the nervous system difference-the cell bodies of all somatic lower motor neurons lie within the CNS in either the ventral horn of the spinal cord or the brain stem -->the cell bodies of all autonomic lower motor neurons lie outside the CNS, within cell clusters called autonomic ganglia. the neurons in these ganglia are called postganglionic neurons. postganglionic neurons are driven by preganglionic neurons, whose cell bodies are in the spinal cord and brain stem. Thus, the somatic motor system control its target (skeletal muscles) via a monosynaptic pathway, while the ANS influences its targets (smooth muscles, cardiac muscle, and glands) using disynaptic pathway

Question 47

where do the preganglionic axons of the sympathetic division emerge in the spinal cord?

Answer 47

-only from the middle third of the spinal cord (thoracic and lumbar segments)

Question 48

where do the preganglionic axons of the parasympathetic division emerge in the spinal cord?

Answer 48

only from the brainstem and the lowest (sacral) segments of the spinal cord

Question 49

where does the preganglionic neurons of the sympathetic division lie? and where do they send their axons?

Answer 49

-lie within the intermediolateral gray matter of the spinal cord. -send their axons through the ventral roots to synapse on neurons in the ganglia of the sympathetic chain, which lies next to the spinal column, or within collateral ganglia found within the abdominal cavity

Question 50

where does the preganglionic neurons of the parasympathetic division lie? and where do they send their axons?

Answer 50

they lie within a variety of brain stem nuclei and the lower (sacral) spinal cord, and their axons travel within several cranial nerves as well as the nerves of the sacral spinal cord

Question 51

which division of the ANS travels farther?

Answer 51

-the parasympathetic preganglionic axons travels much farther than the sympathetic axons because the parasympathetic ganglia are typically located next to, on or in their target organs

Question 52

describe the innervation of the ANS

Answer 52

- innervates glands, smooth muscle and cardiac muscle The ANS: -innervates the secretory glands (salivary, sweat, tear, and various mucus-producing glands) -innervates the heart and blood vessels to control blood pressure and flow -innervates the bronchi of the lungs to meet the oxygen demands of the body -regulates the digestive and metabolic functions of the liver, gastrointestinal tract and pancreas -regulates the functions of the kidney, urinary bladder, large intestine, and rectum -is essential to the sexual responses of the genitals and reproductive organs -interacts with the body's immune system

Question 53

when is the sympathetic divisions most active? and what is it summarised as?

Answer 53

-during a crisis, real or perceived -the 4 Fs --> fight, flight, fright and sex

Question 54

what does the parasympathetic division facilitate?

Answer 54

various non-four-F processes, such as digestion, growth, immune responses and energy storage

Question 55

do all tissues receive innervation from both divisions of the ANS?

Answer 55

-no, for example, blood vessels of skin and the sweat glands are innervated (and excited) only by sympathetic axons --> and lacrimal (tear-producing) glands are innervated (and excited) only by the parasympathetic input

Question 56

describe the enteric division

Answer 56

-the enteric division is a division of the ANS, sometimes called "little brain" -its the lining of the oesophagus, stomach, intestines, pancreas, and gallbladder -control many of the physiological processes involved in the transport and digestion of food, from oral to anal openings -contains about 500 million neurons (same number as the entire spinal cord)

Question 57

what are the 2 networks of the enteric division?

Answer 57

-myenteric (Auerbach's) plexus and submucous (Meissner's) plexus -both consisting with sensory nerves, interneurons, and autonomic motor neurons

Question 58

Why is the enteric division referred to as a "brain"?

Answer 58

-it can operate with a great deal of independence. Enteric sensory neurons monitor tension and stretch of the gastrointestinal walls, the chemical status of the stomach and intestinal contents, and hormone levels in the blood. -but not entirely autonomous --> receives input indirectly from the "real" brain via axons of the sympathetic and parasympathetic divisions

Question 59

describe the role of nucleus of the solitary tract and its connection with the hypothalamus

Answer 59

-located in the medulla and connected with the hypothalamus, the nucleus of the solitary tract is another important centre for autonomic control -some autonomic functions operate well even when brain stem is disconnected from all structures above it, including hypothalamus -solitary nucleus integrates sensory information from the internal organs and coordinates output to the autonomic brain nuclei

Question 60

what is the primary transmitter of peripheral autonomic neurons?

Answer 60

-same transmitter used at skeletal neuromuscular junctions --> acetylcholine (ACh)

Question 61

what do the preganglionic neurons of the sympathetic and parasympathetic divisions release? and its effect

Answer 61

ACh, the immediate effect is that the ACh bind to nicotinic ACh receptors (nAChR), which are ACh-gate channels and evokes a fast excitatory postsynaptic potential (EPSP) that usually triggers an AP in the postganglionic cell. similar mechanism of the skeletal neuromuscular junction, and drugs that block nAChRs in muscle, such as curare, also block autonomic output

Question 62

does ganglionic ACh also activate muscarinic ACh receptors (mAChR)?

Answer 62

yes, mAChR are metabotropic (G-protein-couple) receptors that can cause both the opening and the closing of ion channels that lead to very slow EPSPs and IPSPs. These slow mAChR events are usually not evident unless the preganglionic nerve is activated repetitively

Question 63

in addition to ACh, what else do some preganglionic terminals release?

Answer 63

-a variety of small, neuroactive peptides such as neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP)

Question 64

what is the effects of peptides?

Answer 64

-modulatory, they do not usually bring the postsynaptic neurons to firing threshold, but they make them more responsive to fast nicotinic effects when they do come along

Question 65

what do postganglionic cells in the sympathetic and parasympathetic division use are transmitters?

Answer 65

-postganglionic parasympathetic neurons release ACh --> local effect -postganglionic sympathetic division uses norepinephrine (NE) --> -far reaching effect

Question 66

describe the effects of parasympathetic ACh in contract with sympathetic NE

Answer 66

-parasympathetic ACH has a very local effect on its target and acts entirely through mAChRs. -in contract, sympathetic NE often spreads far, even into the blood where it can circulate widely

Question 67

What are sympathomimetic drugs?

Answer 67

-drugs that promote that actions of norepinephrine or inhibit the muscarinic actions of acetylcholine, they cause effects that mimic activation of the sympathetic division of the ANS -for example, atropine, an antagonist of mAChRs, produces signs of sympathetic activation, such as dilation of the pupils

Question 68

What are parasympathomimetic drugs?

Answer 68

-drugs that promote the muscarinic actions of ACh or inhibit the actions of NE, they cause effects that mimic activation o the parasympathetic division of the AND -for example, propranolol, an antagonise of the beta-receptor for NE, slows the heart rate and lowers blood pressure

Question 69

what are certain principles the diffuse modulatory systems have in common?

Answer 69

-typically, the core of each system has a small set of neurons (several thousand) -neurons of the diffuse system arise from the central core of the brain, most of them from the brainstem -each neuron can influence many others because each one has an axon that may contact more thena 100,000 postsynatic neurons spread widely across the brain -the synapses made by many of these systems release transmitter molecules into the extracullar fluid, so they can diffuse to many neurons rather than be confined to the vicinity of the synaptic cleft

Question 70

What transmitter is used by neurons in the locus coeruleus that's in the pons?

Answer 70

Noradrenaline (or norepinephrine)

Question 71

roughly how many neurons do we have in the locus coeruleus? and synapses

Answer 71

-each locus coeruleus has about 12,000, we have 2 one on each side -just one of its neurons can make more than 250,000 synapses

Question 72

what part of the brain does the locus coeruleus innervate?

Answer 72

-Just about every part of the brain --> all of the cerebral cortex, the thalamus, hypothalamus, olfactory bulb, cerebellum, midbrain and the spinal cord

Question 73

What are the locus coeruleus cells involved in? and when is it activated?

Answer 73

-involved in the regulation of attention, arousal, sleep-wake cycle, learning, memory, anxiety, pain, mood, and brain metabolism -new, unexpected, nonpainful sensory stimuli

Question 74

where are the serotonin-containing neurons mostly clustered?

Answer 74

-within the 9 raphe nuclei

Question 75

which parts of the raphe modulate what

Answer 75

-those more caudal, in the medulla, innervate the spinal cord, where they modulate pain-related sensory signals -those more rostral, in the pons and midbrain, innervate most of the brain in much the same diffuse way as do the LC neurons

Question 76

when do raphe nuclei cells fire the most? and most quiet

Answer 76

-during wakefulness, when an animal is aroused and active, most quiet during sleep

Question 77

what are the raphe neurons involved in?

Answer 77

-intimately involved in the control of sleep-wake cycles, as well as the different stages of sleep -also implicated in the control of mood and certain types of emotional behaviour

Question 78

what are the main dopaminergic cells that have characteristics of the diffuse modulatory systems

Answer 78

-substantia nigra in the midbrain and ventral tegmental area of the midbrain

Question 79

describe the role of dopaminergic neurons of the substantia nigra

Answer 79

-these cells project axons to the striatum, where they facilitate the initiation of voluntary movements --> degeneration of the dopamine-containing cells in the substantia nigra is all that is necessary to produce the progressive, motor disorders of Parkinson's disease

Question 80

describe the role of dopaminergic neurons of the ventral tegmental area

Answer 80

-axons from these neurons innervate a circumscribed region of the telencephalon that includes the frontal cortex and parts of the limbic system

Question 81

what are the dopaminergic projections from the midbrain called and its general functions

Answer 81

-mesocorticolimbic dopamine system --> evidence indicated that its involved in a "reward" system that somehow assigns value to, or reinforces, certain behaviours that are adaptive

Question 82

what are the 2 major diffuse modulatory cholinergic systems in the brain

Answer 82

-basal forebrain complex -pontomesencephalotegmental complex (in brainstem)

Question 83

where do the basal forebrain complex cholinergic neurons lie?

Answer 83

-scattered among several related nuclei at the core of the telencephalon, medial and ventral to the basal ganglia -best known of these are the medial septal nuclei, which provide the cholinergic innervation of the hippocampus, and the basal nucleus of Meynert, which provides most of the cholinergic innervation of the neocortex

Question 84

what is the function of the cells of basal forebrain complex?

Answer 84

-remains mostly unknown -among the first cells to die during the course of Alzheimer's disease, which is characterised by a progressive and profound loss of cognitive functions -implicated in regulating general brain excitability during arousal and sleep-wake cycles -may also play a role in learning and memory function

Question 85

where does the pontomesencephalotegmental complex mainly act on?

Answer 85

-On the dorsal thalamus, where together with the noradrenergic and serotonergic systems, it regulates the excitability of the thalamic sensory relay nuclei --> these cells also project up to the telencephalon, providing a cholinergic link between the brain stem and basal forebrain complexes

Question 86

what are psychoactive drugs?

Answer 86

-compounds with "mind-altering" effects -all act on CNS -most do so by interfering with chemical synaptic transmission -many abused drugs ac directly on the modulatory systems, particularly noradrenergic, dopaminergic, and serotonergic systems

Question 87

What do hallucinogens produce?

Answer 87

- produce hallucinations - LSD produces a dreamlike state with heightened awareness of sensory stimuli, often with a mixing of perceptions such that sounds can evoke images, images can evoke smells, and so on. (not drugs of abuse because doesn't manipulate dopaminergic system)

Question 88

Describe the history of hallucinogens

Answer 88

-the use of them goes back thousands of years -hallucinogenic compounds are contained in a number of plants consumed as part of religious ritual, for example the psilocybe mushroom by the Maya and peyote cactus by the Aztec -modern era of hallucinogenic drug use was unwittingly ushered in at the laboratory of Swiss chemist Albert Hofmann --> lysergic acid diethylamide (LSD)

Question 89

describe LSDs potency

Answer 89

-extremely potent, a dose of 25 microgram is sufficient to produce a full-blown hallucinogenic effect

Question 90

What does LSD act on?

Answer 90

-chemical structure of LSD (and the active ingredients of psilocybe mushrooms and peyote) is very close to that of serotonin, suggesting that it acts on the serotonergic system -LSD is a potent agonist at the serotonin receptors on the presynaptic terminals of neurons in the raphe nuclei. activation of these receptors markedly inhibits the firing of raphe neurons -thus, one known CNS effect of LSD is a reduction in the outflow of the brains serotoninergic diffuse modulatory system

Question 91

Can we conclude that LSD produces hallucinations by silencing the brain's serotonin systems?

Answer 91

-No, for one silencing neurons in the raphe nuclei by other means (i.e., destroying them) does not mimic the effects of LSD in experimental animals, furthermore animals still response as expected to LSD after their raphe nuclei have been destroyed

Question 92

What does current research suggest about how LSD causes hallucinations?

Answer 92

-suggests LSD causes hallucinations by superseding the naturally modulated release of serotonin in cortical areas where perceptions normally are formed and interpreted

Question 93

what common features do cocaine and amphetamines share?

Answer 93

-are simulants -both exert their effects at synapses made by dopaminergic and noradrenergic systems -both drugs give users a feeling of increased alertness and self-confidence, a sense of exhilaration and euphoria, and a decreased appetite -both are sympathomimetic --> they cause peripheral effects that mimic activation of sympathetic division of the ANS (increase HR, BP, dilation of pupils and so on) -both block catecholamine uptake (actions of catecholamine released into the synaptic cleft are normally terminated by specific uptake mechanisms) -both have behavioural action of psychological dependence (addiction)

Question 94

Where is cocaine extracted from?

Answer 94

From the leaves of the coca plant

Question 95

What are the differences between cocaine and amphetamines?

Answer 95

-recent research suggests that cocaine targets DA reuptake more selectively -and amphetamine blocks NE and DA reuptake and stimulates the release of DA -thus these drugs can prolong and intensify the effects of release of DA or NE

Question 96

Why is cocaine and amphetamines addictive?

Answer 96

-users will develop powerful cravings for prolonging and continuing drug-induced pleasurable feelings -these effects are believed to result specifically from the enhanced transmission in the mesocorticolimbic dopamine system during drug use --> this system may normally function to reinforce adaptive behaviours, by short-circuiting the system, these drugs instead reinforce drug-seeking behaviour