human phys exam 3

thermoregulatory inputs

• peripheral temp sensors

  • skin

• central temp sensors

  • warm & cold responsive neurons in hypothalamus

• hypothalamus integrates peripheral & central inputs

temp < setpt

• too cold

• shiver & conserve heat

temp > setpt

• too hot

• sweat

• vasodilate skin

  • helps release excess heat

thermoregulatory responses

• engaged if:

  • body temp moves away from setpt

    • responds to restore body temp

  • central setpt changes

    • bring body temp to new setpt

    • lower setpt → body responds as if too hot

    • higher setpt → body responds as if too cold

feedback loop

• high lvls of regulated variable cause hypothalamus to downregulate behavior & physiology that drive variable up

• negative x balances positive input

• no setpt

setpoint

• areas of hypothalamus integrate info about a physiological variable

  • ex: temperature

• attempt to maintain that variable at a particular x

preoptic area

• thermoregulatory site of integration

• stimulates panting & sweating

• lesioned = hyperthermia

posterior area of hypothalamus

• thermoregulatory site of integration

• stimulates shivering

• lesioned = hypothermia

short-term neural outputs

• sweating

• panting

• salivation

• vasodilation

  • conduction of heat from core by blood and radiation from skin

• shivering

  • generation of metabolic heat

• non-shivering thermogenesis

  • burn off adipose stores

• voluntary behavior

  • driven by conscious perception

long term thermoregulatory outputs

• secretion of thyroid releasing hormone (TRH) to inc thyroid hormone (TH) to inc metabolism

• increased feeding to match metabolic heat generation

  • autonomic can only change metabolic rate by 4x, need behavior to compensate for big environmental shifts

postsurgical shivering

• anesthesia depresses normal thermoregulatory response

• body starts to cool to room temp

• as anesthesia wears off, hypothalamus regains function and induces shivering

• disregulation of body temp

hot flashes

• disregulation of body temp

• lack of estrogen causes occasional lowering of setpt

  • hypothalamus decides its too hot & tries to lower body temp

    • sweating, perception of heat

fever

• disregulation of body temp

• induced by infection and pyrogens

• chemical components of bacteria activate immune system to produce prostaglandins (PGs)

  • stimulate brain to change setpt and sickness syndrome

exocrine

• secretion outside the body

• ex: sweating

endocrine

• secretion into the blood, acting on distant tissues

paracrine

• secretion acting on nearby cells

• antihistamine

autocrine

• secretion acting on same cell

• feedback loop

leptin

• hypothalamus is target organ

• effect is to suppress appetite

• secreted by adipose tissue (gland)

• ~100 aa peptide hormone

• mutations causes obesity

  • exogenous leptin doesn’t dec appetite/body

glucocorticoids

• target organs: liver, muscles, kidneys

• endocrine gland: adrenal cortex

• effect: influences glucose metabolism

aldosterone

• target organs: liver, muscles, kidneys

• endocrine gland: adrenal cortex

• effect: Na+ retention, K+ excretion

epinephrine

• target organs: heat, bronchioles, blood vessels

• endocrine gland: adrenal medulla

• effect: causes adrenergic stimulation

releasing and inhibiting hormones

• target organs: ant pituitary

• endocrine gland: hypothalamus

• effect: regulates secretion of ant pit hormones

tropic hormones

• target organs: endocrine glands & other organs

• endocrine gland: ant pituitary

• effect: stimulates growth & development of target organs, stimulates secretion of other hormones

T4 and T3

• target organs: most organs

• endocrine gland: thyroid gland

• effect: promote growth & development and stimulate basal rate of cell respiration

endocrine cell

• synthesizes hormone

• secretes into blood when stimulated

loss of hormone proof

• connect circ systems of normal and diseased individual

• shared circulation cures the disease

no receptor proof

• connect circ systems of normal and diseased individual

• shared circulation = no effect on disease

• no receptors on target cells

ob/ob mutation

• mouse mutant results in obesity

• extra stop codon terminates leptin transcript

• can’t produce negative feedback signal and keeps putting on fat

• hypoleptinemia

• wildtype blood normalizes it

• homologous to anglo-pakistani brothers

db/db mutation

• mouse mutant results in obesity

• extra stop codon terminates leptin receptor

• can’t detect negative feedback signal & keeps putting on fat

• functional hypoleptinemia

• makes wildtype & ob/ob anorexic

  • excess hormone that they can detect

• homologous to french sisters

feedback regulation

• high lvls of regulated variable cause hypothalamus to downregulate behavior & physiology that drive the variable up

nuclear receptor hormones

• steroids

• thyroid hormone

• retinoic acid

polypeptide and glycoprotein hormones

• lipophilic molecules

  • second messenger coupled hormones

  • GPCR linked to cAMP

  • GPCR linked to phospholipase C and Ca++

  • tyrosine kinase receptors

• coordinate peripheral physiological and central nervous response

  • readily diffuse thruout body and brain to produce parallel phys and behavioral

• release regulated by synth

lipophilic molecules

• pass thru membranes and skin

• made up of sterol ring structures (steroids) or long chain hydrocarbons (thyroid, retinoic acid)

• bound in blood to carrier ptns w hydrophobic domain to help circ thru the body