Homeostasis - Regulation of the body, to maintain a constant stable internal environment in response to both external and internal conditions.

Nervous System

Automatic control systems -” help the body to maintain a stable environment by sending out signals to bring about a response.” These include:

• Receptors -” detect change (rise in temperature).”

• co-ordination centre “(brain, spinal chords - interpret change and decides what needs to be done).

• Effectors (muscles that contract, glands that release hormones - carry out change).”

Nervous system - “sends very fast/precise electrical impulses through nerves, allowing us to respond to things very quickly (e.g., touching a hot object)”

Endocrine system - “Hormones released into the blood stream for specific receptors. Used for the the entire body and act slower, are long-lasting, and are more generalised.”

Negative feedback - “how automatic control systems work. If the level of a substance (e.g. glucose concentration) gets too high, negative feedback opts to lower and vice versa.”

How does the body regulate temperature - “Sweating and shivering”

How are electrical impulses adapted passing messages onto other nerve cells faster?

• “Long

• Thin

• Branched connections to either end of nerve cells”

Synapses - “allows nerve cells to communicate. When an electrical impulse hits the end of a nerve, it causes the release of some chemicals which diffuse across the gas to the next nerve cell where they can trigger another electrical nerve cell.”

Sensory neurons - “Carry information quickly from receptors to the central nervous system (e.g. changes in temperature or C02 concentration in blood).”

Motor neurons - “Sends information decided in the central nervous to the effectors to bring about response.”

Reflex arc - “unconscious reflexes (moving hand away from hot object, swallowing spit). Rapid and automatic so we can respond to things easily.”

• How does reflex arc work?

  1. Receptors in skin pick up stimuli (e.g. touching a sharp object)

  2. Sensory neurons send this information to the spinal chord.

  3. In the spinal chord, information passes through a synapse, where they are momentarily changes to chemicals which diffuse through the gap, turning back into an electrical impulse when they enter the relay neurone.

  4. The relay neurone passes this information (going through a synapse) to a motor neurone where it travels to an effector like your bicep that will contract your hand away from the sharp object.