Coordination and Response

What is a stimulus?

A change in your environment than requires a response. e.g Light, sound, touch, pressure, pain, chemical or temperature.

What is a tropism?

Plants detect and respond to stimuli. Their growth towards or away from a stimulus is called a tropism

What are the types of tropism?

Phototropism, Gravitropism/Geotropism, Hydrotropism

What do you call it when a shoot grows away from gravity?

A shoot grows away from gravity so is negatively geotropic.

What do you call it when a shoot grows towards light?

A shoot grows towards light so it is positively phototropic

What is an auxin?

Plant hormone responsible for tropisms

Describe auxins involvement in positive phototropism

• Auxin synthesised in growing tip

• Auxins diffuses down the plant

• In plant shoots, auxin causes cells to elongate (get longer)

• If plant is illuminated from one time the auxin moves to the dark side

• Cells on the dark side elongate, causing the plant growing tip to grow towards the light

how does auxin cause positive geotropism in plant roots

• In the root auxins inhibit growth

• Auxins move to the lower side of the root due to gravity

• The lower side grows more slowly than the top

• Cells on top side grow faster

• Root tip grows downwards

How is geotropism investigated?

• Apart from doing experiments in space,where there is low gravity, it was difficult to investigate geotropism

• To overcome this scientists use a piece of equipment called a clinostat

• Although gravity is still present, the clinostat continually rotates so that all parts of the plant are equally affected by gravity in the same direction

What is a neurone?

nerve cell

What are the main features of a neurone?

• Dendrites

• Nucleus

• Cell body

• 1 axon

• Axon terminals

What is the main function of a neurone?

Its main function is to communicate with other cells

What is the cell body

The main part of the cell which contain the

What does the cell body contain?

• Nucleus and dendrons

• It also has one axon projecting from it

What is a dendron?

A cytoplasmic extension of the cell body.

What are dendrites?

Even finer cytoplasmic extension from the dendrons.

What is an axon?

A cytoplasmic extension from the cell body that carries messages away from the cell body.

How long can an axon be?

The axon length can vary from cell-to-cell. For example, it can be several metres long

What are Myelin sheaths?

Some (not all) axons are wrapped in a fatty material called myelin.

What do Myelin sheaths do?

• prevents 'short circuits' with other axons

• speeds the impulse along the axon

What is an axon terminal?

• the end of an axon

• The impulses are transmitted to other cells when they reach the axon terminals

What do axon terminals do?

branch to meet other neurons, transmit messages

Where can neurones be found?

PNS or CNS

What is the CNS?

central nervous system

• brain

• spinal cord

What is the PNS?

peripheral nervous system, (other parts of the body), it carries info between the body and the CNS

Where are all interneurones/relay neurones found?

All interneurones/relay neurones are in the CNS

Where are the sensory neurones?

• The majority of the sensory neurone is in the PNS (except for the axon terminals which can be found in the CNS)

• The cell bodies are found in the dorsal root ganglia just outside the spinal cord

Where are motor neurones, and where do the axons go to?

• The cell bodies of motor neurones are in the CNS

• The axons leave the CNS, pass through the PNS and make contact with either muscles or glands

What direction does axon carry information?

Away from the cell body/to axon terminals

What are sensory receptors?

Sensory receptors are either specialised cells or specialised dendrites of sensory neurones

What do sensory receptors do?

They detect a stimulus

What happens to the information in the stimulus? (what is it converted to and where does it go)

The information in the stimulus is then converted into an electrical impulse which ca be sent to the CNS via the sensory neurone

What is transduction?

The changing of he stimulus signal into electrical impulses is called transduction

What type of energy transduced to electrical energy in the eyes (retina, rods and cones)?

light

What type of energy transduced to electrical energy in the ears (organ of hearing)?

sound

What type of energy transduced to electrical energy in the ear as an organ of balance (semicircular canals)

movement (kinetic)

What type of energy transduced to electrical energy in the tongue (taste buds)?

chemical

What type of energy transduced to electrical energy in the nose (organ of smell, olfactory cells)?

chemical

What type of energy transduced to electrical energy in the skin (touch/pressure/pain receptors)?

movement (kinetic)

What type of energy transduced to electrical energy in the skin (temperature receptors)?

heat

What type of energy transduced to electrical energy in the muscle (stretch receptors)?

movement (kinetic)

What are synapses?

gaps between neurons

Process of synapses

• Electrical impulse travels down 1st neuron

• Neurotransmitters are released into synapse and diffuse across gap

• Neurotransmitters bind with receptor proteins imbedded in membrane of the neighbouring neurone

• Electrical impulse starts in the second neurone

• Transmitters reabsorbed by 1st neurone or broken down

What reflexes do we have?

• Nervous system (quick)

• Protect the body

• Automatic/Involuntary

• Homeostasis

What is a reflex arc?

The neuronal pathway of a reflex

What is the function of the cornea?

Transparent region of the sclera at the front of the eye

What is the function of the Lens?

Focuses light rays on the retina

What is the Pupil?

The hole in the centre of the iris

What is the function of the Pupil?

allows light to pass through

What is the Iris?

The coloured part of the eye, contains a set of muscles that control the size of the pupil

What is the function of the Iris?

regulates the light reaching the retina

What is the function of the Suspensory ligaments and ciliary muscles?

Changes the shape of the lens to focus light rays on the retina

What is the retina made of?

Made of light sensitive receptor cells

What does the optic nerve do?

Carries impulses from the retina to the brain

What happens to pupils in bright light?

In bright light, the pupil gets smaller to restrict light entering the eye.

How does this happen?

The radial muscles relax and the circular muscles contract

What happens to pupils in dim light?

In dim light, the pupil gets larger to increase light entering the eye. Radical muscles contract, circular muscles relax

How does this happen?

Radical muscles contract, circular muscles relax

What is the accommodation reflex?

a reflex action of the eye, in response to focusing on a near object, then looking at distant object (and vice versa)

How does the accomodation reflex work?

• When focusing on near objects, the lens needs to refract and end light more. The lens needs to be thick.

• Therefore, the ciliary muscles contract. This puts less tension on the suspensory ligaments. The lens moves into its natural more convex shape

• When focusing on a far object, the lens needs to refract or bend light less. The lens needs to be thin

• Therefore, the ciliary muscles relax. This puts more tension on the suspensory ligaments which pulls the lens moves into a thin convex shape