Chapter 6: Control and Coordination

The structural and functional unit of the nervous system.

Dendrite, cell body and axon.

The gap between two neurons, where the impulse passes on through chemicals.

A sudden, involuntary and quick response to a stimulus, such as pulling the hand away from a hot object.

The path of a reflex action: receptor → sensory neuron → spinal cord → motor neuron → effector (muscle).

Because they are controlled by the spinal cord, they do not wait for the brain to think, and the path is short.

Forebrain, midbrain and hindbrain.

Thinking, memory, control of voluntary actions and processing of senses.

Maintaining the balance and posture of the body and coordinating voluntary movements.

Control of involuntary actions such as heartbeat, blood pressure and vomiting.

By the skull (cranium) and by the cerebrospinal fluid filled inside the coverings around the brain.

The movement of a plant part, in the form of growth, in response to the direction of a stimulus.

Shoots bend towards light (positive phototropism) and roots grow downwards (positive geotropism).

Roots grow towards water (hydrotropism). The pollen tube grows towards the ovule (chemotropism).

Auxin: cell elongation. Gibberellins: growth of the stem. Cytokinins: cell division. Abscisic acid: stops growth and causes wilting.

Iodine is needed to make the hormone thyroxine. Its deficiency can cause goitre.

Insulin, made in the pancreas, controls the blood sugar level. Its deficiency causes diabetes.

Released by the adrenal glands, it prepares the body in an emergency: the heartbeat and breathing speed up.

A method of regulating the release of hormones. When blood sugar rises, more insulin is released, and when sugar falls, less is released.

Nerve impulses travel very fast along neurons and their effect is short-lived. Hormones reach their targets slowly through blood and their effect lasts longer.