3.1 Integration of body systems

Emergent properties

Properties that exist due to many different components working together

The role of the nervous system

To send messages from various parts of the body to the brain, to tell the body what to do

The role of the endocrine system

To release hormones into the bloodstream

How messages are sent in the nervous system

Electrical impulses are used to send messages by cells called neurons which transmit and receive impulses. The responses occur quickly but are short-lived

How messages are sent in the endocrine system

Endocrine glands make chemicals called hormones and pass them straight into the bloodstream

Central Nervous System

Made up of the brain and spinal cord

Brain

The central information integration organ

Spinal cord

Carries nerve impulses between the brain and the rest of the body

Peripheral Nervous System

The part of the nervous system that lies outside the brain and spinal cord

Autonomic Nervous System

A component of the peripheral nervous system that regulates involuntary physiologic processes

Somatic Nervous System

A component of the peripheral nervous system associated with the voluntary control of body movements via skeletal muscles

Cerebral hemispheres

Where learning and memory are formed

Cerebellum

Controls balance and muscle contraction. It is also involved in the formation of muscle memory

White matter (spinal cord)

Containing myelinated axons and other nerve fibres

Grey matter (spinal cord)

Containing the cell bodies of motor neurons and interneurons, with many synapses between these neurons

Motor neurons

They receive signals via synapses with interneurons which allow us to move our muscles, found in the CNS

Synapse

The place where neurons connect and communicate with each other

Interneurons (relay neurons)

They transfer signals between sensory and motor neurons, found in the CNS

Sensory neurons

They carry information about changes in external and internal environments, found in the PNS

Receptors

They sense a change in conditions (a stimulus)

Effectors

They carry out the response when they receive the signal from a motor neuron

Reflex

An autonomic or involuntary response

Monosynaptic reflex arcs

They consist of stimulus, receptor, sensory neurons, interneurons, motor neurons and an effector

Dendrites

Where a neuron receives input from other cells (looks like tree branches)

Axon

The portion of a neuron that carries nerve impulses away from the cell body

Photoreceptors

Specialised light-detecting cells on the retinas at the back of the eyes

Auditory receptors

Sensory receptors consisting of hair cells which allow us to perceive sound

Olfactory receptors

Sensory neurons within the olfactory system, they allow us to detect smells

Left cerebral hemisphere

Receives sensory input from sensory receptors in the right side of the body

Nerve

A bundle of nerve fibres enclosed by a protective sheet

Circadian rhythms

Controlled by a biological clock within the brain

Melatonin

A natural hormone that is mainly produced by the pineal gland in the brain

Suprachiasmatic nuclei

Groups of cells in the hypothalamus of the brain which set a daily rhythm

Epinephrine (adrenaline)

A hormone that prepares the body for vigorous physical activity. It is secreted by the adrenal glands

Hypothalamus

A small region in the brain which produces hormones. It links the nervous and endocrine system

Pituitary gland

Responds to directives from the hypothalamus, releasing different hormones

Sympathetic cardiac nerve

Increases heart rate and force of contraction

Vagus nerve

Decreases heart rate

Medulla

Controls unconscious activities such as heart rate and breathing rate

Baroreceptors

Monitor blood pressure, located within the carotid sinuses and the aortic arch

Chemoreceptors

Monitor blood pH and concentrations of oxygen and carbon dioxide, located in the aortic and carotid bodies

Acidosis

Decrease in blood pH caused by high concentrations of carbon dioxide

Peristalsis

A type of involuntary muscle movement that occurs in the digestive system

Enteric nervous system

The largest and most complex unit of the peripheral nervous system

Plants control…

The direction of growth of their roots and shoots

Positive tropism

Growth towards the stimulus

Negative tropism

Growth away from the stimulus

Tropism

The process of differential growth towards a stimulus

Phytohormones

Chemical messages that control all aspects of plant growth and development

Gibberellin

Affects the rate of cell division and cell enlargement such as stem growth

Ethylene

Promotes ripening in fruits and other aspects of development using a positive feedback mechanism

Auxin

Accumulates on the opposite side of light (shaded side), promotes cell elongation and makes plant curve towards light

Axillary buds

A sprout that develops in the axil of a plant (where leaves develop)

Apical bud

Where new plant growth and elongation occur (main stem of the plant)

Apical dominance

Where the main shoot dominates and inhibits the outgrowth of other shoots (axillary buds)

PIN3 proteins (glycoproteins)

They are found in the plasma membrane. They facilitate the auxin fluxes between cells

Auxin efflux carriers

Required for the export of auxin out of the plant cells

Auxin influx carriers

They mediate the uptake of auxin inside the cells

Gravitropism

A response of plant roots to the stimulus of gravity

Phototropism

The ability of the plant to re-orient the shoot growth towards a direction of light source

Cytokinin

Produced in root apical meristems (tip of roots) and is transported to the shoot where they promote lateral bud growth

Ratio of auxin to cytokinin

A high ratio of cytokinin to auxin favours shoot production, whereas a high ratio of auxin to cytokinin favours root production

Mechanism of auxin transport

1. Auxin influx (IAA) into a cell occurs by diffusion and is facilitated by influx carriers

2. Within the cell, IAA dissociates by losing a proton. The negatively charged ions are unable to leave the cell

3. Auxin efflux carriers pump these ions across the plasma membrane and into the cell wall

4. The cell wall is slightly acidic, so auxin returns to its uncharged state

5. Auxin can then diffuse into an adjacent cell