Topic 5 - Homeostasis and Response

The Brain

Functions of Parts

The brain and spinal chord together make up the central nervous system

Cerebral Cortex

Responsible For:

  • Consciousness
  • Intelligence
  • Memory
  • Language
  • Senses e.g sight, hearing

2 Hemispheres

  • Right controls the left
  • Left controls the right

Cerebellum

Responsible For:

  • Balance
  • Muscle co-ordination

Hypothalamus

Responsible For:

  • Regulating body temperature
  • Sending signals to the pituitary gland

Brain Stem

Medulla

Controls unconscious activity e.g breathing, beating of heart

How Scientists Study the Brain

Studying People with Brain Damage

Electrically Stimulate Different Parts of the Brain

Scanning the Brain

CT Scans (X-Rays)

PET Scans (Radioactive Chemicals)

MRI Scans (Magnetic Fields)

which areas of the brain are damaged

measuring the underlying activity

certain parts of the brain are highlighted depending on what you do e.g see things, feel sad, listen to music

Why treating the Brain is so Difficult

wide range of things that can go wrong in the brain

  • tumours
  • trauma
  • mental health problems
  • infections

encased within our skull

surrounding brain tissue is fragile

extremely difficult to fix anything via surgery

the brain is so complex and we don't fully understand it and the underlying processes

makes it difficult to fix it with drugs and chemicals

Homeostasis

the regulation of conditions inside the body to maintain a stable internal environment, in response to both internal and external conditions

Cells Need Specific Conditions to Function:

  • temperature
  • acidity
  • supply of glucose
  • supply of water

keeps everything around the right conditions

don't keep it constant, levels do fluctuate

even if our external conditions change, we can still keep our internal temperature at 37°c

Automatic Control Systems

Change from Optimal Conditions - Sends a Signal - Reverses Change - Back to Normal Conditions

Receptors - detect a change e.g a rise in temperature

Co-Ordination Centres - brain or spinal chord - interpret the change and decide what needs to be done

Effectors - things that carry out the change e.g muscles or glands

These components are in different parts of the body

Nervous System

  • very fast and precise electrical impulses through nerves
  • respond quickly

Endocrine System

  • releases hormones into the blood stream
  • travel through the whole body but only affect cells with the correct receptors
  • slower, longer lasting, more generalised

Automatic Control Systems

Negative Feedback

does the opposite of whatever the change was

too high - decrease

too low - increase

Example

normal temperature ---> walk into a cold room ---> receptors detect decrease in temperature ---> send electrical impulses to co-ordination centre ---> creates a useful response e.g. shivering ---> effectors carry out response ---> increases body temperature ---> back to normal temperature ---> if the body then becomes too hot ---> different set of receptors and effectors carry out responses to bring the temperature back down e.g. sweating