chemical control of behavior

what is the hypothalamus part of

diencephalon, and sits under the thalamus

what is the secretary hypothalamus

a large collection of nuclei in the brain that regulates a lot of these kinds of chemical control of behavior systems

what does secretory hypothalamus release

hormones into the bloodstream that can act all over the body and in the brain

can the hormones the secretory hypothalamus release have different actions

yes, depending on the target tissue or system once released into the bloodstream

what is the autonmoic nervous system

part of the peripheral nervous system, also regulated by the hypothalamus

what is ANS important for

regulaating blood vessel strucutre, internal organs, things that are happening that you’re not coinsuoicly deciding to to. important for stress responses and arousal states

The diffuse neuromodulatory systems of the brain

Send projections all over the brain to widely regulate these systems

Diencephalon

part of the brain that sits between the forebrain and telencephalon and the  main cephalon of the midbrain 

what’s right in the middle of the hypothalamus

third ventricle that allows for interaction with cerebrospinal fluid

what does hypothalamus do

thermostat of the body: regulates homeostasis (keeping the body in a narrow, optimal physiological range). Temperature, blood pressure, salinity, glucose, stress responses, social behavior (crucial for getting food and offspring), feeding, sleep, more

What are right below the hypothalamus

the optic chiasm and pituitary gland

what are the zones of the hypothalamus

periventricular space, medial zone, lateral zone

what zone of hypothalamus is most important for releasing factors into the bloodstream

periventricular space

where does the pituitary gland in the brain

extends below the brain, where it is held in a delicate bone cradle

what are the two lobes of pituitary gland

anterior and posterior

what does pituitary gland do

mouthpiece by which the brain speaks to the body, neurons from the hypothalamus send their axons down into the pituitary gland

what cells project into posterior pituitary gland

magnocellular neuroscretroy cells

posterior pituitary gland mechanism

cell bodies in the hypothalamus send their axons down through the pituitary stalk into the posterior pituitary gland

there are lots of blood capillaries in the posterior pituitary gland

axons send their terminals to release neuropeptides onto these capillary beds

what are the two hormones released into the posterior pituitary

oxytocin and vasopressin

oxytocin and vasopressin are actually secreted by

cell bodies that have neurons in the brain

what is oxytocin important for

social behavior, parturition, and lactation

what is vasopressin

anti-diuretic hormone, regulates water balance, agression

what cells project onto anterior pituitary

parvocellular neurosecretory cells (from hypothalamus)

what do parvocellular cells do

send their axons to the pituitary, which also has capillaries, but they also have their own hormone-secreting cells

the anterior pituitary gland is an actual

organ itself, secreting hormones in respones to hypothalamic inputs

what stimulates/inhibits AP hormone-secreting cells

Hypophysiotropic hormones from the hypothalamus are released into the hypothalamic-pituitary portal circulation

What hormones are made by the AP

Growth hormones, ACTH, Follicule-stimulating hormone (gonads development), thyroid stimulating hormones

Negative feedback loop of pituitary

If the hormone gets too high in the pituitary, it’ll shoot back to the brain and give a signal to stop

Brain regulation for epinephrine

Starts in the hypothalamus, sends a signal to the endocrine cells to release these hormones, which then act on target cells, and then feed back to the hypothalamus to say we have enough, turn it off

• Brain and pituitary feedback for cortisol and HPA

Secreted from the hypothalamus, act on the anterior pituitary to release ACTH, then act on endocrine cells in the periphery to release cortisol to stimulate biological effects 

• But if these levels get high enough then they’re going to feedback to both the anterior pituitary and the hypothalamus to say okay we have enough 

types of stressors

acute vs. chronic, physical vs. psychological

acute physical stressors

• Physical exertion, acute injury, emergency, predator-prey interaction 

• Cue in the environment says there’s something in the environment you need to get away from 

• Chronic physical stressors 

• Illness, starvation/obesity, altitude exposure, heat/cold exposure 

• Challenging the body's ability to get back to homeostasis for long periods of time

• Psychological stress

• Exam, what are you going to do in your future 

when body is stressed, what is down-regulated

• Saliva production, digestion, filtration, food movement, and reproductionw

when body is stressed, what is up-regulated

• Attention and vigilance, pupil dilation, breathing, blood pressure and heart rate, blood sugar and fat concentrations, vessel constriction, contraction strength (trembling) 

The HPA Axis steps

1. Perceive a stressor 

2. The hypothalamus releases corticotropin-releasing hormone (CRH) into the hypophyseal portal system (a term for the system that connects the hypothalamus to AP gland) 

3. The AP releases adrenocorticotropic hormone (ACTH) into the systemic blood circulation 

4. The adrenal cortex releases glucocorticoid hormones (GCs), aka cortisol, in the systemic blood circulation 

5. Systemic GCs stimulate metabolism and suppress immune function

6. GCs circulate back into the brain and stimulate GC receptors, providing negative feedback at multiple levels 

what is predisone

• synthetic steroid/form of cortisol, anti-inflammatory

how does prednisone affect the body

• he body thinks that cortisol levels are very high, so it shuts off secretion 

• If prednisone is stopped quickly the body can’t turn on cortisol again fast enough leading to adrenal insufficiency 

adrenal insufficiency

low blood pressure, abdominal pain, mood/emotional changes 

Addison’s Disease

degeneration of the adrenal gland, leads to fatigue, skin discoloration, stomach pain, weight loss, mood changes 

Cushings Disease

• P releases too much ACTH, Rapid weight gain, sleeplessness, memory impairment, immunosuppression, irritability 

eustress

some sort of arc that’s the perfect amount of stress; probably no one is ever in it 

• Includes having focused attention, emotional regulation, and rational thinking

what does too little stress lead to

impaired attention, boredom, confusion, and apathy 

what does too much stress lead to

•  impaired memory, burnout, and impaired executive functioning

what can chronic stress cause

the negative feedback loop to breakdown

how does chronic stress cause negative feedback loop to breakdown

Chronically high levels of cortisol can cause atrophy of the dendrites (receptive parts of the brain that see cortisol and shut down the system) in places like the hippocampus that express glucocorticoid receptors, less response to feedback 

• Leads to memory and cognitive impairment 

what does control over a stress activate

•  the Prefrontal Cortex and blocks some of the negative outcomes t

test done in rats to see stressor controllability

• Rat in box getting shock, scared because they don’t know whats happening 

  • In one condition, if rat turns a wheel, they will turn off the shock (escapable stress) 

  • In one condition, if rat turns a wheel, nothing happens (inescapable stress) 

  • No stress control: no shock, also have a well

• The inescapable stress was very damaging, led to a “learned helplessness” phenotype (stop even trying to get out)

what controls the ANS

the periventricular hypothalamus

two divisions of ANS

sympathetic: increase heart rate and blood pressure, mobilizes glucose reserves, suppresses digestion (fight or flight). this causes adrenlaine to stimulate all of these things

parasympathetic: decreases heart rate and blood pressure, promotes digestion (rest and digest) 

• Occurs after sympathetic, brings you back down

what kind of strucutres does sympathetic and parasympathetic innervate

smooth muscle, cardiac muscle, gland cells

where do preganglionic fiber emerge from in sypmathetic

thoracic and lumbar spinal cord

where do preganglionic fiber emerge from in parasympathetic

brainstem and sacral

What do central nervous system neruons do in both divissions of ANS

synapse with ganglion cells in the periphery, but release different neurotransmitters

what neurotransmitters do sympathetic release

• noradrenaline, epinephrine (stimulating system) onto target tissues

what neurotrasnmiter does parasympathetic realse

acetylchlorine (Ach)