2.85 describe the structure and functioning of a simple reflex arc illustrated by the withdrawalof a finger from a hot object

Only the spinal chord is used to product a reflex. This is so that time is reduced for the response and the persons finger won't be damaged as much.

Reflexes are always the same.
Reflexes can't be controlled but responses can.

The receptors are stimulated by the heat, electrical impulses sent to the spinal chord, The relay nerve directly connects the impulses to the motor nerve which creates the response to withdraw the hand.

2.84 understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses

- The receptors in the sense organs, when stimulated create electric impulses along the nerves.
- This moves into the nervous system and out to create a rapid response.
 e.g. Light enters the eyes, this creates an electrical impulse along the nerves. They move in and out of the nervous system, to the effector and create a response such as blinking.

2.83 recall that the central nervous system consists of the brain and spinal cord and is linked to sense organs by nerves

-The Central nervous system consists of the brain and the spinal chord.

-Receptors send electrical signals to the effectors using the nerves.

2.82 describe how responses can be controlled by nervous or by hormonal communication and understand the differences between the two systems

Differences:
-Hormones act slower and have a longer effect
-Hormones are transported via the blood stream and bind to receptors on the outside of cells
-Hormone molecules can cause chain reactions
-Nerves communicate through electrical impulses
-They both use they same transmitters, but use them in different way.

Thermoregulation

2.77 Understand that homeostasis is the maintenance of a constant internal environment and that body water content and body temperature are both examples of homeostasis.

Homeo is the idea of something being the 'same'.  
Stasis refers to the idea of a fixed point or a set of conditions.

Homeostasis is the idea that the conditions are kept the same or constant.

Homeothermic is the idea of maintaining the same temperature.

Some organisms (e.g. mammals) which when the environmental temperature increases or decreases, their body temperature stays constant. These are homeothermic organisms.

The carry a process called thermoregulation, an example of homeostasis.

Mammals need to maintain a constant body temperature because of rates of reactions and to prevent denaturing (enzymes).

The optimum temperature for the enzymes, tends to be the temperature that the mammals maintain their body at.

Sensitivity

2.76 Understand that organisms are able to respond to changes in their environment