2.1 Homeostasis and response

• What is homeostasis?


  Maintaining a constant internal environment for the optimum conditions of your cell
• What does homeostasis maintain?


  optimal conditions for enzyme action and all cell function.

  e.g:

  • blood glucose concentration
  • body temperature
  • water levels
• what are the two control systems?

  1. Nervous system
  2. endocrine system
• what does the nervous system do?

  allows body to detect and react to changes in the environment
• what is the nervous system?

  The nervous system is a complex network of nerves and cells that transmit signals between different parts of the body.
• what does nervous system control?

  1. breathing
  2. heart rate
  3. body temperature
• What is the Central Nervous System (CNS)?

  -the spinal cord and the brain

  -the CNS coordinates response of effectors which may be muscles contracting or glands secreting hormones
• What is the Peripheral Nervous System (PNS)?

  it is the nerves that connect the CNS to all the receptors
• stimulus


  change in the environment that you react to
• what are the three control system?

  1. receptors
  2. coordination centre
  3. effector
• What does receptor do?

  they are cells that detect stimuli (changes in the environment)
• What does coordination centre do?

  receive and process information from receptors

  (such as brain, spinal cord, pancreas)
• What does effector do?

  muscles or glands; respond to receptors and bring about change
• What are nerve cells called?

  Neurons
• what are neurons adapted to?

  carry electrical impulses from one part of the body to the other.
• what is a bundle of neurons called?

  nerve
• stages in the nervous response:

  1. stimulus - a change in the environmental conditions
  2. receptors- detecting change (attached to a sensory neurone )
  3. coordinator-processes and redirects the information
  4. effector - reacts upon receiving the information ( attached to a motor neurone)
  5. response - returns back to normal conditions
• what does the axon carry in a motor neurone?

  Signals along the cell
• what does the dendrons receive in the motor neurone?

  receive signals and sends them towards the cell body
• motor neurone


  carries electrical impulses from CNS to the effectors
• relay neurone

  transmits electrical impulses from sensory neurones to motor nuerones
• sensory neurone


  transmits electricsl impulse from receptors to the CNS
• what is synapes?

  the gap between neurons. Information must be transmitted as a chemical message.
• synapse

  When the electrical impulse reaches the end of the neurone, chemicals called neurotransmitters are released. The chemicals diffuse across the synapse and bind to receptors on the next neurone.
• how does the nervous system react to change?

  Receptor → sensory neurone → CNS → motor neurone → effector
• What are reflexes?


  Involuntary response to a stimulus
• why is reflex actions important?

  reflex actions are automatic and rapid; they don not involve conscious part of the brain. they are important so we can reduce our chance of being injured.
• how does reflex arc work?

  1. stimulus is picked up by receptor
  2. impulse carried along nerve cell (sensory neurone to CNS)
  3. relay neurones in the CNS relay the message
  4. impulse carried along nerve cell ( motor neurone) to effector muscle
  5. effector muscle bring about a response
• Parts of the brain:

  1. Cerebral cortex
  2. Hypothalamus
  3. Pituitary gland
  4. Cerebellum
  5. Medulla
• cerebral cortex


  Involves with consciousness, language, thought, perception, memory and attention
• hypothalamus 


  instinctive behaviour

  • feeding
  • fight
  • flight
  • mating
• pituitary gland 


  releases hormones
• cerebellum

  controls balance, co-ordination of movement, precision and timing
• medulla


  part of the brain stem

  involves in unconscious activities

  e.g controlling breathing, heartbea, gut and blood pressure
• methods for studying the brain

  1. studying patients with brain damage
  2. Electrically stimulating the brain
  3. MRI ( magnetic resonance imaging)
• studying an alive persons brain injury

  how?

  • can compare a persons abilities before or after a brain damaging incident
  • can correlate change in behaviour to the part of brain damage
• studying an alive persons brain injury

  benefits

  • can ask person for information
  • doesn’t have to be invasive

  risks

  • rely on people being accurate about the ”before”
• Electrically stimulating the brain

  how?

  • Brain stimulated electrically by pushing tiny electrode into tissue giving it a small zap of electricity.
• MRI 


  how?

  • use big machines with magnets to take a scan of brain to look for damage
• MRI


  benefits

  • no surgery
  • get a detailed picture

  risk

  • machine is claustrophobic
  • can’t be used if patient has metal implant