2.82 Communication

Responses can be controlled by nerves or hormonal control

1. Motor Nerve - located in the spine

- electrical/nerve impulses travel down the axon of the cell to the effector (e.g muscle)
- the schwann cells produce myelin sheath (fat) to increase the sphere of nerve conduction

2. Endocrine System

- produces hormones (proteins or steroids)
- made in the endocrine glands (e.g adrenal gland - adrenaline)
- hormone travels through blood
- travels to target tissue/organ

- hormones can have multiple targets and effects

2.77b Thermoregulation

Homeostasis - maintenance of a constant internal environment

Receptor   ->   Co-ordinator    ->    Effector
(e.g brain)                      (37/38 degrees)                       (skin)

     ^
stimuli
(Temp of body, blood)

When to hot:

The blood vessel within the skin dilate/widen so more blood flows to the surface, increasing the exchange of heat to the outside of the body by; sweat, radiation, flat hairs.

Cools to blood and returns to body temp to its optimum temp. 

When too cold:

Skin reacts with shivering and raised hairs 

This forces the blood to travel deep within the tissues and reduces the heat exchange with the external environment

2.77a Thermoregulation

Homeostasis - the maintenance of a constant internal environment
                      e.g body water content, body temperature



Homeothermic - keeping the same temperature

                           e.g Thermoregulation (the act of keeping the same temp.)

Animals try to keep optimum temperature within their bodies, so that the enzymes and cells within them can work as best as they can.

2.76 Organisms responding to change

Types of change

- light

- temperature

- pressure

- chemical alteration

Receptor   ->   Effector    ->   Response

(detects the change)      (responds to change)