The body in balance

Question 1

suprachiasmatic nucleus (SCN)

Answer 1

a small group of neurons in hypothalamus that act like metronome for the rest of the body. active during the day and silent during the night. activity is regulated by 2 sets of proteins. SCN also tracks the time of the day based on info coming from photoreceptors in retina to keep the body time in sync with actual day duration of 24h.

Question 2

melatonin release

Answer 2

melatonin is a hormone that influences sleep behaviors.
electrical signals originating in SCN enters the PVN–>PVN send signals to pineal gland (pine cone shaped gland located in the middle of the cerebral hemispheres) –> pineal gland secretes melatonin

Question 3

preparing for wakeful state from sleep

Answer 3

1. cortisol levels increase in blood –> releasing sugars from storage and induce feeling of appetite while using the sugars for energy replenishment
2. body temperature increases to increase metabolic rate

Question 4

neuroendocrine system

Answer 4

the brain region involved in hormone release and regulation; hormones are important for keeping the body at equilibrium, brain reacts to hormonal signals to “manage the body”.
PVN and SON in hypothalamus sends axons to the pituitary gland–>activation of specific neurons–>release of oxytocin or vasopressin

Question 5

oxytocin and vasopressin (+ function as hormones)

Answer 5

both act as NT inside the brain and as hormones in other parts of the body;
vasopressin- (ADH) affects water retention in kidneys and vasoconstriction
oxytocin- promotes uterine contractions during labor and milk release during nursing

Question 6

Example for a 3-hormone cascade

Answer 6

regulation of reproduction in mammals, same underlying mechanism in both sexes;

1. gonadotropin- releasing hormone (GnRH) from the hypothalamus makes the anterior pituitary release
2. LH and FSH –> make the gonads secrete
3. sex hormones and start the development of mature eggs or sperm
   - -> sex hormones attach to receptors in hypothalamus and anterior pituitary to modify release of hypothalamic and pituitary hormones. (negative feedback loop)

Question 7

stress response

Answer 7

involving 3 of the brain’s parallel communication systems;

• message sent to muscles through somatic (voluntary) NS telling muscles to react to danger (fight or flight..)
• message sent through autonomic (involuntary) NS redirect nutrients and oxygen supply to the active muscles (sympathetic NS increases blood pressure etc, parasympathetic restricts blood flow to other areas and decreases digestion etc)
• a cascade of neuroendocrine hormones in hypothalamus and anterior pituitary activates release os cortisol from adrenal cortex –>glucocorticoids prepare the body to respond to the threat.