Homeostasis and response

Homeostasis and Response - B5

Homeostasis: The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal or external changes. It's important because it maintains optimum conditions for enzyme actions and all cell functions. It involves automatic control systems.

Negative feedback: This means to counteract an internal or external change. It works like this: 

The receptor detects a stimulus which is either too high or too low. > The coordination centre receives and processes the information, then organises a response. > The effector produces a response which counteracts the change by making the level either increase or decrease. It restores the optimum level. 

The effectors continue producing a response as long as they're stimulated by the coordination centre and this could cause the opposite problem so negative feedback will start again.

The conditions that the body need to maintain are: 

Temperature - This is controlled by shivering or sweating - The organs involved are the skin, glands and blood.

Blood glucose levels - This is controlled by releasing insulin - The organs involved are the blood and pancreas.

Urea and Ion levels - This is controlled by urination or drinking - The organs involved are the bladder, kidneys and blood.

Hydration levels - This is controlled by urination or drinking - The organs involved are the stomach, kidneys and blood.

Types of neurones:

Sensory neurone - These transmit electrical impulses, which is information, from the receptors to the CNS.

Motor neurone - These transmit nerve impulses from the CNS to effectors.

Relay neurone - These transmit nerve impulses from a receptor to the CNS.

The automatic response system - the nervous system: 

CNS - In vertebrates (animals with back bones) this consists of the brain and spinal cord only. In mammals it's connected to the body by sensory neurones and motor neurones.

Sensory neurones and motor neurones are part of it.

Effectors - Muscles or glands which respond to nervous impulses. Muscles respond to the impulse by contracting. Glands respond to the impulse by secreting hormones.

Receptors - These are cells which detect stimuli. There are many different type of receptors like taste, sound and sound. These can form a larger complex organs e.g. the retina of the eye is covered in light receptor cells.

Reflexes:

Synapses are the gap between two neurones and they are how electrical impulses travel from one neurone to the next. The signal is transferred by chemicals called neurotransmitters which diffuse across the receptor site. 

Reflexes are rapid automatic responses to certain stimuli that don't invlove the conscious part of the brain. It helps reduce the risk of injury. 

Reflex arc - 1) hand near heat. 2) stimulation of the pain receptor. 3) impulses travel along the sensory neurone. 4) impulses are passed through a relay neurone via a synapse. 5) impulses travel alone a motor neurone via a synapse. 6) when the impulses reach the muscle, it contracts to pull you away.…