C3.1

System integration

The coordination of component parts of a system to perform an overall function.

Importance of system integration

Allows multicellular organisms to function effectively as a whole.

Levels of biological organization

Cells, tissues, organs, and body systems.

Hierarchy of subsystems

Lower levels combine to form higher levels of organization.

Emergent properties

Characteristics that arise from interactions between components.

Example of emergent property

A cheetah's speed results from integration of multiple body systems.

Methods of integration in animals

Nervous signalling, hormonal signalling, and transport of materials.

Nervous system signalling

Rapid transmission of electrical impulses for short-term effects.

Endocrine system signalling

Slower transmission of hormones with longer-lasting effects.

Role of blood system

Transports hormones, nutrients, gases, and wastes between organs.

Brain as an integration centre

Processes information from multiple inputs.

Functions of the brain

Information processing, learning, and memory.

Input integration in the brain

Combines sensory information from different receptors.

Memory as integration

Result of interactions between neurons.

Spinal cord role

Integration centre for unconscious processes.

Conscious processes

Require processing in the brain.

Unconscious processes

Automatic responses coordinated by the spinal cord.

Sensory neurons

Carry impulses from receptors to the central nervous system.

Input to CNS

Sensory neurons transmit information to spinal cord and brain.

Motor neurons

Carry impulses from CNS to effectors.

Effect of motor neuron output

Muscles are stimulated to contract.

Nerves

Bundles of nerve fibres.

Components of a nerve

Sensory neurons, motor neurons, and protective sheath.

Transverse section of nerve

Shows myelinated and unmyelinated fibres.

Protective sheath

Connective tissue surrounding nerve fibres.

Reflex arc

A rapid involuntary response to a stimulus.

Pain reflex arc example

Withdrawal of hand from a painful stimulus.

Pain receptor

A free sensory nerve ending in the skin.

Interneuron location

Grey matter of the spinal cord.

Effector in pain reflex

Skeletal muscle.

Cerebellum

Part of the brain that coordinates movement.

Role of cerebellum

Coordination of skeletal muscle contraction and balance.

Circadian rhythm

A roughly 24-hour biological cycle.

Melatonin

Hormone that regulates sleep-wake cycles.

Pineal gland

Secretes melatonin.

Pattern of melatonin secretion

Higher at night, lower during the day.

Effect of melatonin

Promotes sleep.

Epinephrine (adrenaline)

Hormone secreted by adrenal glands.

Trigger for epinephrine secretion

Stress or vigorous activity.

Effects of epinephrine

Increases heart rate, blood flow to muscles, and glucose availability.

Purpose of epinephrine

Prepares body for intense muscle contraction.

Hypothalamus

Links nervous and endocrine systems.

Pituitary gland

Controls other endocrine glands.

Control of endocrine system

Hypothalamus regulates pituitary hormone secretion.

Baroreceptors

Receptors that detect blood pressure.

Location of baroreceptors

Carotid arteries and aorta.

Chemoreceptors

Receptors that detect blood pH and gas concentrations.

Location of chemoreceptors

Carotid bodies, aorta, and brainstem.

Medulla

Coordinates cardiovascular responses.

Heart rate control

Nerve impulses adjust heart rate and stroke volume.

Ventilation rate

Breathing rate and depth.

Cause of blood pH changes

Changes in carbon dioxide concentration.

Control of ventilation

Chemoreceptors signal medulla.

Effectors in ventilation

Diaphragm and intercostal muscles.

Peristalsis

Wave-like muscle contractions moving food through the gut.

Control of swallowing

Voluntary control by central nervous system.

Control of egestion

Voluntary control by central nervous system.

Enteric nervous system (ENS)

Controls involuntary gut movements.

Role of ENS

Coordinates peristalsis through digestive system.

Tropism

Directional growth response to a stimulus.

Observation of tropisms

Seedlings bend in response to stimuli.

Qualitative observations

Descriptive, non-numerical data.

Quantitative observations

Numerical data such as angle of curvature.

Accuracy of measurements

Closeness to true value.

Precision of measurements

Repeatability of measurements.

Phototropism

Growth response to light.

Positive phototropism

Growth towards a light source.

Site of phototropism

Shoots.

Phytohormones

Signalling chemicals in plants.

Role of phytohormones

Control growth, development, and responses to stimuli.

Auxin

A phytohormone involved in growth and phototropism.

Auxin diffusion

Auxin can diffuse into plant cells.

Auxin efflux carriers

Transport auxin out of cells.

Polar auxin transport

Auxin carriers concentrated on one side of cells.

Auxin concentration gradient

Causes uneven growth in plant tissue.

Auxin and cell elongation

Auxin promotes hydrogen ion secretion.

Apoplast

The cell wall and spaces outside the plasma membrane.

Effect of acidification

Loosens cellulose cross-links.

Result of cell wall loosening

Cell elongation.

Cytokinin

Phytohormone involved in cell division.

Source of cytokinin

Produced in root tips.

Source of auxin

Produced in shoot tips.

Transport of cytokinin

Moves from roots to shoots.

Transport of auxin

Moves from shoots to roots.

Auxin-cytokinin interaction

Coordinates root and shoot growth.

Ethylene

A gaseous phytohormone involved in fruit ripening.

Positive feedback in ripening

Ripening increases ethylene production.

Effect of ethylene

Stimulates fruit ripening changes.

Benefit of positive feedback

Rapid and synchronized fruit ripening.