co-ordinating responses and controlling heart rate

• What is the role of baroreceptors? Where are they found?

  • Pressure receptors
  • Detect changes in blood pressure
  • Present in aorta, vena cava and carotid arteries
• What is the role of chemoreceptors? Where are they found?

  • Chemical receptors
  • Detect changes in particular chemicals in the blood eg co2
  • sensitive to changes in pH levels of the blood
  • Located in aorta, carotid artery and medulla
• Describe the action of adrenaline in the flight or fight response

  1. its the first messenger- binds to receptors on liver cell membrane
  2. Adenylyl cyclase activated
  3. Conversion of ATP into cAMP
  4. cAMP activates enzymes like protein kinases
  5. And therefore glycogen is converted to glucose
• state an example of the nervous and endocrine system working together to bring about a response

  happens in flight or fight response
• state the role of the hypothalamus and the responses in the body that it induces when a threat is detected by the autonomic nervous system

  • when a threat is detected, it communicates with the sympathetic nervous system and the adrenal-cortical system
  • sympathetic nervous system uses neuronal pathways to initiate the body's reactions, whereas the adrenal-cortisol system uses hormones in the blood stream
  • sympathetic NS sends impulses to glands and smooth muscles and tells the adrenal medulla to release adrenaline and noradrenaline, which cause eg an increased heart rate
  • other hormones are released from adrenal cortex which have longer lasting effects. Hypothalamus stimulates pituitary gland to secrete ACTH, which travels to adrenal cortex and causes it to release these hormones

  
• state examples of all the physiological responses that take place in the fight or flight response

  List of physiological responses:

  A) more oxygenated

  B) dilate

  C) better vision

  D) constrict

  E) blood

  F) brain and heart

  G) ventilation

  H) blood glucose

  I) respiration

  J) energy

  K) contraction

  L) relaxes

  M) oxygen

  N) digestion

  O) focusing

  P) threat

  
• explain what the purpose of adrenaline is

  • triggers liver cells to undergo glycogenolysis so glucose is released into the blood
  • respiration increases so more energy is available for muscle contraction
• true or false? adrenaline is hydrophobic

  FALSE- adrenaline is hydrophilic- so it can't pass through cell membranes
• describe the actions of adrenaline in the fight or flight response

  • binds to receptors on liver cell's surface
  • when it does this, triggers a chain reaction of events
  • when adrenaline binds to receptor, adenylyl cyclase is activated, which is present in the cell membrane
  • adenylyl cyclase converts ATP to cyclic AMP, which acts as a secondary messenger that activates other enzymes (protein kinases) that in turn, convert glycogen into glucose
  • adrenaline is the first messenger and cAMP is the second messenger
  • at each stage, the number of molecules involved increases so is said to have a cascade effect

  
• true or false? heart rate is voluntary and controlled by the peripheral nervous system

  FALSE- it's INVOLUNTARY and controlled by the AUTONOMIC nervous system
• what part of the brain is responsible for the control of heart rate?

  medulla oblongata
• how is the medulla oblongata linked to the SAN?

  • two centres in the medulla that link it to SAN
  • one centre increases heart rate by sending impulses through the sympathetic nervous system, these impulses are transmitted through the accelerator nerve
  • one centre decreases heart rate by sending impulses through the parasympathetic nervous system, these impulses are transmitted through the vagus nerve
  • which centre is stimulated depends on the information the receptors in blood vessels receive, two types of receptors which provide info affecting heart rate: baroreceptors and chemoreceptors
  • so heart rate is dependent on info received by both
• how do chemoreceptors detect changes in pH because of increased/decreased CO2 levels?

  • if carbon dioxide level increases, the pH of the blood decreases because carbonic acid is formed when carbon dioxide interacts with water in the blood
  • response is triggered therefore to increase heart rate
  • blood therefore flows more quickly to the lungs so CO2 can be exhaled
  • when CO2 levels decrease, pH of the blood rises
  • detected by chemoreceptors again
  • reduction in frequency of nerve impulses sent to medulla oblongata
  • therefore frequency of signals sent to SAN reduce
  • heart rate decreases to normal level
• describe processes involved in baroreceptors helping to control heart rate

  • baroreceptors detect changes in pressure
  • if pressure too high, signals sent to medulla oblongata centre which decreases heart rate
  • medulla sends impulses along parasympathetic neurones to SAN which decreases rate at which the heart beats
  • reduces blood pressure to normal
  • if pressure too low, impulses sent to medulla centre which increases heart rate
  • medulla oblongata sends nervous signals down sympathetic nerves to the SAN, which increases the rate the heart beats at, increasing bp to normal
• How is heart rate affected by hormones?

  adrenaline and noradrenaline- affect pacemaker region in times of stress, increase frequency of impulses produced by SAN