IGCSE Biology Coordination

Summary:

This text discusses coordination in living organisms, focusing on the nervous and hormonal systems. The nervous system comprises neurons and the central nervous system (CNS), consisting of the brain and spinal cord. It coordinates responses to stimuli by transmitting impulses through sensory neurons, relay neurons, and motor neurons to effectors, which bring about responses. Reflexes are automatic and rapid responses to stimuli that protect from harm and involve a reflex arc.

The hormonal system involves glands producing chemical messengers called hormones that travel through the blood to target cells or organs. The text details insulin, which regulates blood glucose levels, and adrenaline, which prepares the body for fight-or-flight responses.

Additionally, the text discusses osmoregulation, thermoregulation, and how plants respond to stimuli like light (phototropism) and gravity (geotropism). Homeostasis, the maintenance of a constant internal environment, is also explained.

Overall, the text covers how living organisms sense and respond to changes in their surroundings to maintain proper functioning and survival.

Excerpt:

IGCSE Biology Coordination

Coordination
Living organisms are sensitive to their surroundings – one of the 8 life processes. A change in the environment is called a stimulus – internal (such as blood glucose levels) or external – such as a temperature change. Organisms can respond to these changes.

The nervous system consists of neurons & the CNS. The central nervous system (CNS) comprises the brain and spinal cord. The CNS coordinates a response between receptors and effectors.

Sensory neurons carry the impulse from the receptor to the CNS. Relay neurons relay the impulse around the CNS. Motor neurons carry the impulse from CNS to the effectors.

An effector brings about a response to stimuli. An effector may be: – A muscle – contract to bring about movement – A gland – secrete hormone.

HOW IT WORKS:
1. Receptors detect a stimulus and convert its energy into an impulse
2. Sensory neurons transmit this electrical impulse to the CNS
3. Impulse transmitted through CNS by a relay neurone & CNS coordinates a response
4. Impulse transmitted to effector along a motor neurone
5. Effector brings about the response