Lecture 9 Flashcards
(41 cards)
What is Homeostasis?
The process by which a system (such as the body) maintains a relatively constant internal milieu
Temperature/Blood concentrations
Blood pH/ p
What is the Set Point?
Set point is the point of optimal physiological functioning. Physiological and behavioral function must be maintained within a narrow range around set point.
What are the four steps required for Homeostasis?
Reference value: Set point
Detection mechanism: to detect deviation from set point
Mobilization: To return to set point
Negative Feedback: Shut down mobilized process once homeostasis is reached
What is Hypovolemic thirst?
Hypovolemic thirst refers to a kind of thirst provoked by low blood volume.
Ex. when bleeding from a wound.
What is osmotic thirst?
Osmotic thirst is caused by cellular dehydration- which can occur after ingesting a salty snack.
Dehydration and ADH/ Vasopressin Response.
ADH/AVP is release from the Anterior pituitary in response to Cerebral osmoreceptor dehydration and reduction of blood volume -via baroreceptors
What is caused by the release of ADH/AVP?
Retention of water in kidneys
Vasoconstriction
How do Cerebral osmoreceptors respond to mild and extended dehydration?
In mild dehydration: Sends signal to paraventricular nucleus (PVN) and supraoptic nucleus (SON) to produce AVP/ADH, which stimulates water retention
In extended dehydration: stimulates drinking
How do Baroreceptors respond to low blood volume?
Baroreceptors stretch receptors in walls of blood vessels and stimulates PVN and SON to produce AVP/ADH, release from post pituitary to increases blood pressure
What is stimulated by Hypovolemia in the kidneys?
Drop in blood pressure signals the brain and the kidneys to produce renin to converts angiotensinogen (from blood) to angiotensin I, II, and III.
What are some characteristics of the peptide hormone Insulin?
It is released by beta cells of pancreas in response to food cues or when blood glucose rises. In the liver, it converts glucose to glycogen. Prevents breakdown of glycogen and mobilization of fat stores. Is the ONLY hormone to promote energy storage.
Describe Metabolism: Fasting state
The metabolic system’s top priority is the BRAIN. the Brain can only process glucose via blood (ketones as last resort)
During fasting, glucose is diverted to brain at expense of rest of body, which metabolizes fatty acids into glucose.
What are non-food sources of energy and their characteristics?
Glucagon is released from alpha cells of pancreas when blood glucose is low. It stimulates glycogenolysis and Lipolysis in liver
During stress, cortisol and epinephrine stimulate production of glucose in liver (gluconeogenesis), and breakdown of fat.
What are some Orexigenic Neurotransmitters and where are they release from?
NPY (Neuropeptide Y) and AgRP (Agouti-related protein) both released from ARC, act on paraventricular nucleus of the hypothalamus (PVN) to induce feeding behavior.
What are some Anorectic neurotransmitters?
CART (cocaine and amphetamine-regulated transcript) and
POMC, which makes α-MSH(melanocyte-stimulating hormone) both might inhibit eating
What are some characteristics of the peptide hormone Ghrelin?
It is released by GI tract when the stomach is empty. It is stimulated by chronic stress and inhibits reproduction by acting on HPG Axis.
Activates the reward system and acts in ARC hypothalamus to promote feeding
What are Neuropeptide Y (NPY) and Agouti related protein (AgRP)?
They are orexigenic peptides that stimulates feeding behavior. Released from neurons in ARC hypothalamus.
Orexin and Melanin-concentrating hormone (MCH)
Both increase feeding and metabolism
Inhibited by leptin
Activated by ghrelin
Orexin also called hypocretin stimulates wakefulness (narcolepsy)
Describe Leptin?
Its a adipokine (released by fat cells) peptide hormone. Not the “satiety” hormone but the “starvation” hormone. Leptin treatment does not curtail obesity (usually).
Control of food intake: Insulin
When insulin levels drop, hunger ensues. Insulin reaches the hypothalamus via CSF. In baboons there is an increased of CSF insulin after meal.
ICV insulin reduced food intake. Insulin may serve as signal of amount of fat. Obese people have more circulating insulin and Insulin receptors in ARC.
what is POMC?
POMC is a hormone precursor normally produced by the pituitary gland and hypothalamus in the brain.
POMC involvement in food inhibition
Leptin and insulin activate receptors in ARC, to produce POMC. POMC is broken down into opioids and melanocortins (α-MSH and ACTH) POMC and α-MSH activate receptors in PVN suppressing feeding.
CART involvement in food inhibition
Leptin activates receptors in ARC to secrete CART. CART activate receptors in PVN to suppresses feeding
Hypothalamic control of inducing feeding
When leptin and insulin are low and ghrelin is high the NYP/AgRP are activate, suppressing POMC/CART and inducing feeding
