L25: Homeostatic control system and hormone intro

• homeostasis is the presence of a stable internal environment to ensure cells have what they need and to do what we want
• balance is homeostasis. It is a relativity constant internal environment that supports cell functioning and life processes. Human body systems keep each regulated variable within an optimal range.
• imbalance is the loss of homeostasis. As cells function, they use up nutrients and produce biproducts. Examples of this is during growth, reproduction, exercise, stress and illness
• regulated variable is a variable for which there is a sensor and a system to ensure the variable is kept within a normal range, around a set point.
• examples of regulated variables is core temperature, plasma glucose and calcium concentration, and basal metabolic rate
• normal range is the the restricted set values for a regulated variable, that permits optimal cell functioning.
• set-point is the physiological value for any given value, around which its normal range fluctuates. each person has a unique set-point for each variable based on genetics and other factors.
• set point vs normal range label 1

  A) non-physiological

  B) homeostasis

  C) decreasing

  D) room temperature

  E) stimulus

  F) receptor

  G) information affects

  H) control centre

  I) sends commands to

  J) effector

  K) restored

  L) increasing

  M) setpoint

  
• label set point vs normal range 2

  A) stimulus

  B) receptors

  C) information affects

  D) control centre

  E) sends commands to

  F) effectors

  G) restored

  H) restored

  
• maintaining homeostasis


  the receptor/sensor sensitive to the environment change the stimulus.
• maintaining homeostasis

  the control centre receives and processes the information supplied by the receptor and sends out commands
• maintaining homeostasis

  the effector responds to the commands send by the control centre by opposing the stimulus
• the population reference range tends to be wider than any given individuals normal range based on the test results from large groups of healthy people or based on the breadth of individual normal ranges within the population sample
• when assuming normal distribution, the reference range is obtained by measuring the values in a reference group and taking two standard deviations either side of the mean
• most individuals will have a set point that is within the population range. the normal range fluctuates around the set point for any given variable
• if the variable moves outside and individuals normal range, it may lead to illness, disease of symptoms of a disorder. this may occur even if the variable remains within the population range
• feedback occurs when the receptor stimulation triggers a response that changes the environment at the receptor
• negative feedback means the effector activated by the control centre opposes the original stimulus and minimises changes
• negative feedback control loops keep a regulated variable within its normal range around its set-point
• if the variable goes up, the negative feedback brings it down. if the variable goes down , the negative feedback brings it up
• negative feedback 1

  A) stimulus

  B) variable

  C) sensors

  D) control centre

  E) effectors

  F) stimulus

  
• characteristics of a negative feedback loop

  the sensors monitor the variable and detect changes
• characteristics of a negative feedback loop

  the control centre compares variables changed value to the set-point. sends signals to effectors if correction is required
• characteristics of a negative feedback loop

  the effectors act to oppose the effect of the stimulus, thereby correcting the change and restoring the variable to its set-point.
• in positive feedback, an initial stimulus produces a response that exaggerates or enhances the change i.original conditions
• positive feedback control drives a process to completion by amplifying the change to a regulated variable
• if the variable goes up, the positive feedback makes it go up more
• if the variable goes down, the positive feedback with make it go down more
• characteristics of a positive feedback loop

  the sensors monitors the variable and detect changes. the control centre sends signals to effectors to amplify change. the effectors action amplifies the change, to drive a process to completion
• amplifying breast milk release

  the sensors are the nerve cells detecting suckling around the nipple areola. the control centre is the pituitary gland trigger the release of the hormone to stimulate milk producing cells. then the effector, milk producing cells send milk to ducts for release from nipple, causing the child to suckle more
• the nervous system and endocrine systems work together to control the body and maintain homeostasis
• in the nervous system

  • homeostatic control (breathing, core temperature, blood pressure)
  • sensory detection and interpretation
  • control of muscle and movement
  • higher functions (thinking, speech learning, memory, emotion)
• endocrine system control (hormonal)

  • homeostatic control (plasma calcium or glucose or pH)
  • cellular metabolism
  • reproduction
  • growth and development
  • immunity and stress management
• in the nervous system, neurons produce action potentials and release neurotransmitters at synapses. the neurotransmitter binds to chemically-gated ion channels on the post-synaptic cell. it has extremely fast signalling
• in the endocrine system, the endocrine cells release hormones into the bloodstream to travel to target cells. hormones bind to the membrane or intracellular receptors of target cells. it is slower, but longer lasting action compared to the nervous system
• label endocrine glands and organs

  A) hypothalamus

  B) pituitary gland

  C) thyroid gland

  D) adrenal glands

  E) pancreas

  F) pineal

  G) parathyroid