Neuroscience Final

point to point communication in the nervous system

one neuron activates ~one neuron

• sparse connectivity & brief transmission of NT

diffuse pattern of communication in the nervous system

one neuron can activate many neurons

• NT can be released into bloodstream

homeostasis

maintenance of the body’s internal environment within narrow physiological range

regulate:

• temperature, food and water intake, blood volume, salinity, oxygenation

what are the 3 zones of the hypothalamus

1. lateral zone

2. medial zone

3. periventricular zone (closest to third ventricle)

location and function of periventricular zone

groups of neurons that lie near the wall of third ventricle

• receives input from lateral and medial zones and brain stem

• controls autonomic nervous system, regulating sympathetic and parasympathetic innervation of visceral organs

• neurons extend projections into the pituitary gland

what provides the broad signaling from the hypothalamus to the rest of the body

the pituitary gland

what are the 2 lobes of the pituitary gland

1. anterior lobe (left)

2. posterior lobe (right) & goes straight to bloodstream

________ are substances released into the blood by neurons

neurohormones

what are the two different neurohormones magnocellular neurosecretory cells release into the bloodstream after innervating the posterior pituitary

oxytocin and vasopressin

oxytocin

lactation and uterine contractions

vasopressin (ADH)

regulates blood volume and salt concentration, and acts on kidneys to modify water retention and urine production

what is important for thirst

vasopressin (because it regulates blood volume and salt concentration)

vasopressin regulation for thirst pathway

1. lowered blood volume and pressure triggers release of renin from kidneys

2. renin converts angiotensinogen to angiotensin I, then angiotensin II

3. angiotensin II has direct effects on kidney and blood vessels, also stimulating subfornical organ

4. subfornical cells project into hypothalamus, activating vasopressin cells

5. vasopressin acts on kidneys to increase water retention and lowered urine production

________ activation on the subfornical organ can modulate activity in the lateral hypothalamus to evoke behavior

angiotensin II

what lobe of the pituitary gland contains hormone releasing organs

the anterior pituitary

hormones released by anterior pituitary

• FSH - gonads

• LH - gonads & thyroid

• TSH - thyroid

• ACTH - adrenal cortex

• GH - all cells

• prolactin - mammary glands

parvocellular (hypothalamic) neurosecretory cells directly release ________ into the capillary beds at the top of the pituitary

neurohormones

what are parvocellular hormones called

hypophysiotropic hormones

what is the hypothalami-pituityary portal circulation

capillary beds

what do hypophysiotropic hormones run down to get to the anterior lobe

capillary beds

what do hypophysiotropic hormones bind to

pituitary cells

________ cells secrete or stop secreting hormones into the general circulation

pituitary

the steroid hormone ________ is thought to be related to stress, and why

cortisol

• mobilizes energy reserves

• suppresses immune system

• lipophilic molecule that crosses the BBB

what produces cortisol

the adrenal cortex

anterior pituitary pathway of stress response

1. periventricular hypothalamus parvocellular neurons secrete corticotropin-releasing hormone (CRH) into portal circulation & travels down anterior pituitary

2. stimulates release of adrenocorticotropic hormone (ACTH), which is released into circulation by the hormone secreting cells in anterior pituitary

3. ACTH stimulates cortisol release from adrenal cortex

adrenal insufficiency

occurs due to sudden stopping of prednisone (or Addisons disease)

• frequent administration fools brain into reducing natural production of cortisol

cushings disease

caused by pituitary gland dysfunction leading to increased levels of ACTH

• causes weight gain, immune suppression, sleeplessness

one effect of cortisol ending is elevated ________ levels

Ca2+ (chronic stress)

somatic PNS

• and dorsal root ganglia

innervates skin, joints, and muscles

• nerves that allow us to sense things and move our body

• dorsal root ganglia: clusters of cell bodies outside the spinal cord that contain somatic sensory axons

autonomic PNS (visceral)

innervates organs, blood vessels, and glands

• nerves that unconsciously monitor and run organs, glands, etc

• sympathetic: fight or flight

• parasympathetic: rest and digest

enteric PNS

complex network that runs gut and food digestion

functions of autonomic nervous system (ANS)

• innervates nearly every kind of tissue in every part of body

  • muscle, glands

• salivary, sweat, tears, mucus

• blood pressure and flow

• meet oxygen demands

• regulates digestive functions

• kidney, bladder, large intestine, rectum

• sexual responses

• immune system

what are the divisions of the ANS

1. sympathetic

2. parasympathetic

sympathetic division

fight or flight

• nerves from spinal cord > chain ganglia > glands and smooth muscle

• mobilize energy and divert blood to muscle

• increased heart rate and blood pressure

• depressed digestive function

• mobilized glucose reserves (frees stored energy for immediate use)

• fight, flee

parasympathetic divison

rest and digest

• stop sweating

• slower heart rate and blood pressure falls

• nerves from brainstem and spinal cord run to glands and smooth muscle

• increased digestive function

differences between somatic and ANS circuits

somatic:

• modulation is fast and precise

• controls target via a monosynaptic pathway

  • cell bodies controlling motor neurons lie within spinal cord or brain stem

ANS:

• modulation is slow and widely coordinated

• controls via a disynaptic pathway

  • cell bodies controlling motor neurons lie in ganglia outside of CNS

preganglionic neurons of sympathetic division

• originate in intermediolateral gray matter of spinal cord

• axons are sent though spinal cord ventral root to sympathetic chain or collateral ganglia

preganglionic neurons of parasympathetic division

• originate in parts of brain stem and sacral spinal cord

• axons travel through nerves to reach ganglia located relatively near their target organ

sympathetic and parasympathetic have (the same / opposite) effects on one another

opposite

• when one is high, the other is low

• both cannot be activated at the same time, one inhibits the other

what are the 2 networks of the enteric division of ANS

1. myenteric plexus

2. sub mucous plexus

both networks contain visceral sensory and motor neurons that control the function of the digestive organs

what is the network of nerves called that lines the walls of the esophagus, stomach, intestines, pancreas and gallbladder

the enteric nervous system

what do enteric sensory neurons detect

• stretch and tension of gastrointestinal tract

• chemical status of stomach and intestinal contents

• hormone levels in blood

what do enteric motor neurons control

• muscle motility

• mucous and digestive secretions

how do the enteric sensory and motor neurons work together

both neurons make sure that mucous and enzymes mix to digest food, and that there is sufficient blood flow to transport nutrients to rest of body

what ca suppress the enteric nervous system

the activation of the sympathetic system

what are the four diffuse modulatory system of the brain and what NT do each use

1. noradrenergic (norepinephrine NE)

2. cholinergic (acetylcholine ACh)

3. dopaminergic (dopamine DA)

4. serotonergic (serotinon 5-HT)

serotonergic raphe nuclei

• innervates many of the same areas as noradrenergic system

• functions together with noradrenergic system

• compromises the ascending reticular activating system

  • particularly involved in sleep-wake cycles and mood

  • most active during wakefulness when aroused and active

dopaminergic substantia nigra

• axons project to striatum

• facilitates initiation of voluntary movements (degeneration causes parkinson’s disease)

dopaminergic ventral tegmental area

• innervates circumscribed region of telencephalon

• mesocorticolimbic dopamine system: dopamine projection from midbrain

cholinergic basal forebrain complex

• core of telencephalon, medial and ventral to basal ganglia

• function is mostly unknown, participates in learning and memory

cholinergic pontomesencephalotegmental complex

• utilizes ACh

• function is to regulate excitability of thalamic sensory relay nuclei

cocaine and amphetamine affect what systems

dopaminergic and noradrenergic systems

LSD, mushrooms, and peyote are close to the structure of what

serotonin

________ lesions dont cause permanent hallucinations, which is why LSD seems to modulate serotonin flow, but that’s not the whole story

raphe nucleus

stimulants block what

catecholamine reuptake

cocains blocks what

dopamine reuptake

amphetamine blocks what

norepinephrine and dopamine reuptake

• also stimulates dopamine release

what are the 3 components of the hypothalamic response

1. humoral response

2. visceromotor response

3. somatic motor response

humoral response

stimulates or inhibits release of pituitary hormones into blood stream

visceromotor response

adjusts the balance of sympathetic and parasympathetic outputs of ANS

(when body is cold):

• urine production inhibited

• body fat reserved are mobilized

• body shivers

• blood shunted away from the body surface

somatic motor response

incites an appropriate somatic motor behavioral response

(when body is cold):

• motivated behavior to seek out warmer conditions

the brain needs a constant ________ supply

glucose

prandial state

the state right after having eaten a meal — the body is full of nutrients

• anabolism

anabolism

assembly of glycogen and triglycerides as energy storage

postabsorptive state

fasting between meals

• catabolism

catabolism

glycogen and triglycerides are broken down to provide body with continuous supply of energy

3 stages of energy balance

1. In theory, we have energy balance by replenishing energy at the same time

2. If intake exceeds usage, adipose increased and leads to obesity

3. If intake fails to meet demands, loss of fat occurs, leading to starvation

lipostatic hypothesis

the brain is involved in regulating energy intake to maintain optimal conditions

parabiosis

surgically joining two mice together to link blood supplies

evidence for a molecular signaling mechanism for feeding behavior

• hypothesis

• possibility 1

• possibility 2

• experiment

• result & interpretation

mouse has mutation that causes obesity

• hypothesis: obesity is related to aberrant signaling

• possibility 1: the mutant mouse has something in its blood that causes the obesity

  • adding this factor to the thin mouse should make it become obese

• possibility 2: the mutant mouse is missing something that causes the obesity

  • adding this factor to the obese mouse should make it become thin

• experiment: fuse the mutant (obese) mouse and wild type (lean) mouse together to result in a common blood supply

• result: mutant mice feeding behavior and obesity are greatly reduced

  • something missing appeared to be replaced

the mutation in obese mice encoded the protein ______

leptin

what does treating an obese mouse with leptin do

it reverses their obesity

leptin is normally released by ______ cells and regulates body mass by acting on ______ neurons

fat; hypothalamic

leptin

decreases appetite and increases energy expenditure

leptin deficiency

stimulates hunger and feeding and suppresses energy expenditure

why isn’t leptin a miracle cure for obesity

many obese individuals have a lot of leptin, so it seems that their hypothalamic neurons are not sensitive to it

lesions to lateral hypothalamus cause

anorexia

lesions to ventral hypothalamus cause

obesity

what is the arcuate nucleus of the hypothalamus important for

the control of feeding

where is the hypothalamic nucleus located

near the base of the 3rd ventricle

what does the arcuate nucleus release

peptides that modulate feeding behaviors

leptin activates actuate neurons that release ______ and ______ peptides

aMSH and CART

anorectic peptides

diminish apetite

injection of drugs that block anorectic peptides

increases feeding behavior

arcuate neurons project to regions that orchestrate what 3 responses

humoral, visceral, and somatic responses

humoral response effect of aMSH and CART peptides

• neurons in paraventricular hypothalamus are activated, releasing hypophysiotropic hormones

• then stimulates secretion of TSH and ACTH from anterior pituitary

• hormones act on the thyroid and adrenal glands to raise cellular and metabolic rate throughout body

effect of elevated leptin levels on visceromotor response

• paraventricular nucleus has direct projections to brainstem nuclei that control the ANS

• aMSH and CART are directly released onto ANS nuclei in the brainstem/spinal cord via direct projection from the arcuate nucleus

• increases sympathetic nervous system tone

• increases body temperature (metabolic rate)

effect of elevated leptin levels on somatic motor response

• arcuate nucleus has direct projections to lateral hypothalamus

• decreases feeding behavior

when leptin levels are decreased, accurate neurons release what

NPY and AgRP

NPY and AgRP vs aMSH and CART

they have opposite effects on energy balance

NPY and AgRH are ______ peptides, which increase appetite

orexigenic

what do orexigenic peptides do to appetite

increase appetite

what to NPY and AgRH inhibit the secretion of

TSH and ACTH

what do NPY and AgRH activate

parasympathetic division of ANS

what do NPY and AgRH stimulate

feeding behavior

what does the activation of MC4 receptor do

inhibits feeding behavior

where is the MC4 receptor located

on cells in the lateral hypothalamus

aMSH and AgRP

both neuropeptides act on the MC4 receptor in the lateral hypothalamus but have opposite effects

aMSH and MC4

aMSH is an agonist (activates)

• activation of MC4 receptor that inhibits feeding

AgRP and MC4

AgRP is an antagonist (inhibitor)

• inhibiting the MC4 receptor that stimulates feeding