Control of heart rate

revision notes for unit 5 AQA topic.

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Glossary

  • Autonomic
    • self generating
  • Antogolistic
    • if one system contracts a muscle then the other will relax it
  • Medulla Oblongata
    • centre of the brain that controls heart rate
  • Carotid arteries
    • arteries that serve the brain
  • Pressure receptors
    • occur within walls of carotid arteries and the aorta.
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Autonomic Nervous System (ANS)

2 parts:

  • Sympathetic nervous system
  • Parasympathetic nervous system

Both haves nerves that emerge from the brain and go to organs concerned.

ANS = involutarily controls activities of internal muscles and glands

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Sympathetic System (SS)

  • stimulates effectors
  • speeds up activity
  • emergency controller
    • used during strenous excersis and when experiencing powerful emotions
  • makes us more aware of surroundings.
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Parasympathetic system

  • inhibits effectors
  • slows down activity
  • controls activities under normal resting conditions
  • conserves energy and replenishes supplys
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SS and PS are Antogoistic

  • Allows activities of internal glands and muscles to be regulated by a balance of the two systems
    • e.g. heart rate.
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Control of heart rate

  • Resting rate of an adult varies depending on demands for oxygen
    • e.g. excessive increases demand
  • Medulla oblongata
    • 2 centres
      • one that increases heart rate which is linked to sinoatrial node in SS
      • one that decreases heart rate, linked to sinoatrial node in PS
    • centre stimulated depends on pressure and chemical changes in the blood.
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Chemoreceptors

  • found in wall of Carotid arteries
  • sensitive to changes in pH of blood
    • changes due to carbon dioxide conc.
  • Process of control:
    • higher than normal conc of carbon dioxide
    • chemoreceptors detect this and increase freq of nervous impulses to medulla oblongata
      • increases heart rate
    • centre increases freq of impulses via SNS to sinoatrial node which increases heart rate.
    • increases blood flow means more CO2 removed and pH returned to normal
    • medulla oblongata reduces freq of impulses and decreases heart rate to normal.
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Effects of exercise on cardiac output

Increased muscular/metabolic activity

--> more CO2 produced as increased respiration

--> blood pH is lowered

--> chemical receptors in the carotid arteries increase frequency of impulses to medulla oblongata

--> SA node increases heart rate

--> increases blood flow removes CO2 faster

--> CO2 level returns to normal

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Control by pressure receptors

Operate as follows:

  • When blood pressure higher than normal
    • nervous impulse is transmitted to medulla oblongata to decrease heart rate
    • impulses go via PS to sinoatrial node
  • When blood pressure is lower than normal
    • transmit a nervous impulse to medulla oblongata that increases heart rate
    • sends impulses via SS to sinoatrial node which increases heart rate.
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Comments

Tamsin

Brilliant resource helped me understand this better even if i am doing edexcel biology its the same content

Diksha

Some stuff I haven;t done but I loved card 6,7,8,9 

Thanks!

Hannah

Antogolistic? I think you mean antagonistic

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