control and coordination

Stimulus

Any change in the internal or external environment to which an organism responds (e.g., light, heat, cold, touch, pressure, sound).

Response

The reaction of an organism’s body to a stimulus (e.g., withdrawing a hand when touching a hot object).

Coordination

The systematic working together of various organs in a body to produce an appropriate response to a stimulus.

Nervous System

Uses electrical impulses for rapid, localized, and short-term responses in organisms.

Endocrine System

Uses chemical messengers (hormones) for widespread, slower, and longer-lasting responses.

Neuron

The structural and functional unit of the nervous system.

Dendrites

Branching, tree-like projections of a neuron that receive electrical/chemical impulses.

Axon

A long, slender projection of a neuron that transmits electrical impulses away from the cell body.

Synapse

The specialized microscopic gap/junction between the axon terminal of one neuron and the dendrite of the next neuron.

Reflex Action

A sudden, rapid, and involuntary response of the body to a stimulus, operating without conscious thought.

Reflex Arc

The shortest pathway taken by electrical impulses during a reflex action.

Central Nervous System (CNS)

Comprises the brain and the spinal cord.

Peripheral Nervous System (PNS)

Nerves originating from the CNS that connect it to the rest of the body.

Somatic Nervous System

Controls voluntary bodily movements via skeletal muscles.

Autonomic Nervous System (ANS)

Controls involuntary visceral body functions, such as heart rate and digestion.

Tropism

Growth movements that are directional, dependent on the direction of the stimulus.

Phototropism

Growth response to light where stems bend toward light and roots grow away.

Geotropism (Gravitropism)

Growth response to gravity; roots grow downward while stems grow upward.

Hydrotropism

Directional growth of roots toward water or moisture.

Thigmotropism

Growth response to touch/contact, such as tendrils coiling around support.

Plant Hormones (Phytohormones)

Chemical signals used in plant coordination for growth and responses.

Feedback Mechanism

The regulatory process that maintains homeostasis by adjusting hormone levels based on internal conditions.

Insulin

A hormone secreted by the pancreas that lowers blood glucose levels.