2.80-2.92 Coordination and response

What is the nervous system pathway?

1. Receptor

2. Coordinator

3. Effector

What is a stimulus?

A change in the environment

What does the receptor do?

The receptor detects the stimulus

How is the signal transferred from the receptor to the coordinator?

Via sensory neurons

What does the coordinator do?

The coordinator processes information

What does the effector do?

The effector carries out the response

What are the three parts of the nervous system?

The brain, the spinal cord and the peripheral nerves

What is the system that includes the brain and the spinal cord called?

Central nervous system

What are the parts of the neurone (LH to RH)?

• nerve endings

• axon

• myelin sheath

• dendrites

• cell body

What is the role of dendrites?

They carry the nerve impulses towards the cell body

What is the role of the myelin sheath?

It insulates the axon so the nerve impulse travels faster

What is the role of the nerve endings?

They carry the nerve impulses to the other neurones

What is the role of the cell body?

It contains all the usual organelles of a cell, eg mitochondria, nucleus

What is the role of the axon?

It carries nerve impulses away from the cell body

What are the two types of neurone?

Motor neurone and sensory neurone

What is a sensory neurone?

Carries nerve impulses from receptors to the CNS

What is a motor neurone?

Carries nerve impulses from the CNS to effectors

What are the similarities between the motor neurone and the sensory neurone?

• both have cell body

• dendrites, axon, myelin sheath, nerve endings

What are the differences between the motor neurone and the sensory neurone?

• cell body position differs

• motor neurone axon is longer

• motor neurone dendrites are shorter

• motor neurone dendrites are branched

• sensory neurone dendrites have a myelin sheath

What is a reflex arc?

A pathway which a nerve impulse follows for a reflex action through the spinal cord

What are the parts of the reflex arc?

• sensory neurone

• receptor

• synapse

• relay neurone

• motor neurone

• effector

Describe the process of a reflex action.

Fill in the gap:

1. The _ (a pin prick)

2. Pain _ are stimulated

3. Nerve impulse travels along the _ neurone

4. Nerve impulse enters the spinal cord

5. Nerve impulse passes across a _ into a relay neurone

6. Nerve impulse passes into a _ neurone and travels along this out of the spinal cord

7. Nerve impulse reaches the effector (the finger muscle) and the muscle _, pulling the finger away

1. The stimulus (a pin prick)

2. Pain receptors are stimulated

3. Nerve impulse travels along the sensory neurone

4. Nerve impulse enters the spinal cord

5. Nerve impulse passes across a synapse into a relay neurone

6. Nerve impulse passes into a motor neurone and travels along this out of the spinal cord

7. Nerve impulse reaches the effector (the finger muscle) and the muscle contracts, pulling the finger away

What are 3 key features of a reflex action?

• bypasses the brain

• fast

• unconscious, innate

What is this part of the eye?

Iris

What is this part of the eye?

Pupil

What is this part of the eye?

Cornea

What is this part of the eye?

Lens

What is this part of the eye?

Sclera

What is this part of the eye?

Retina

What is this part of the eye?

Optic nerve

What is this part of the front of the eye?

The ciliary muscle

What is this part of the front of the eye?

Suspensory ligaments

What is this part of the back of the eye?

Fovea

What is this part of the back of the eye?

Blind spot

What is this part of the back of the eye?

Choroid

What is this part of the back of the eye?

Retina

Where is there the highest concentration of receptors?

In the fovea

Describe the choroid:

It is a black layer that sits under the retina

It absorbs excess light

Describe the cornea:

Transparent coating on the front of the eye

What is the function of the cornea?

The cornea protects the eye and refracts light entering the eye

Describe the pupil:

Central hole in the iris

What is the function of the pupil?

Allows light to enter the eye

Describe the iris:

Coloured ring of muscle tissue

What is the function of the iris?

Alters pupil size by contracting or relaxing

Describe the lens:

Transparent biconvex lens

What is the function of the lens?

Focuses light clearly onto the retina

Describe the ciliary muscle:

Ring of muscle tissue

What is the function of the ciliary muscle?

Alters the shape of the lens

Describe the suspensory ligaments:

Ligament tissue

What is the function of the suspensory ligaments?

Connects the ciliary muscle to the lens

Describe the optic nerve:

Nervous tissue

What is the function of the optic nerve?

Carries nerve impulses to the brain

In DIM LIGHT, what do the radial and circular muscles do?

The radial muscles contract and the circular muscles relax

In DIM LIGHT, what happens to the pupil size?

It increases, and the light entering the eye increases (dilation)

In BRIGHT LIGHT, what do the radial and circular muscles do?

Radial muscles relax and circular muscles contract

In BRIGHT LIGHT, what happens to the pupil size?

It decreases, and the amount of light entering the eye decreases (constriction)

What does antagonistic mean?

Equal and opposite muscle movements which work together for a movement - whilst one relaxes, one contracts

How is light focused?

Light is refracted by the cornea and the lens and then focused on the fovea

What is the relative angle of light rays reaching the eye when focusing on a near object?

Wide angle

What is the degree of refraction needed when focusing on a near object?

High degree

What is the shape of the lens when focusing on a near object?

Short and fat - more curved to increase refraction

Describe the ciliary muscle when focusing on a near object?

Contracts towards the lens inwards

Describe the suspensory ligaments when focusing on a near object?

Slacken, no longer pulling tight on the lens

What is the relative angle of light rays reaching the eye when focusing on a far object?

Almost parallel

What is the degree of refraction needed when focusing on a far object?

Low degree (as the cornea has already refracted most of the light)

What is the shape of the lens when focusing on a far object?

Longer and thinner

Describe the ciliary muscle when focusing on a far object?

Relaxes away from the lens, pulling suspensory ligaments taut

Describe the suspensory ligaments when focusing on a far object?

Taut, pulling tight on the lens

What is a synapse?

A junction between 2 neurones across which nerve impulses pass via neurotransmitter molecules

What is this highlighted part of the synapse?

Presynaptic neurone

What is this highlighted part of the synapse?

Postsynaptic neurone

What is this highlighted part of the synapse?

Complimentary receptors

What is this highlighted part of the synapse?

Synaptic cleft

What is this highlighted part of the synapse?

Vesicles

What are inside of the vesicles?

Neurotransmitter molecules

How are neurotransmitters used in a synapse function?
Fill in the gap:

1. The nerve impulse arrives at the first neurone called the _ neurone

2. Vesicles (sacs) containing _ move towards the membrane of the neurone

3. The vesicles _ with the _ of the _ and release their contents into the synapse

4. The neurotransmitter molecules _ across the synapse

5. The neurotransmitter molecules bind to _ on the membrane of the postsynaptic neurone

6. The receptor molecules stimulate the generation of a _ _ impulse in the postsynaptic neurone

1. The nerve impulse arrives at the first neurone called the presynaptic neurone

2. Vesicles (sacs) containing neurotransmitters move towards the membrane of the neurone

3. The vesicles fuse with the membrane of the neurone and release their contents into the synapse

4. The neurotransmitter molecules diffuse across the synapse

5. The neurotransmitter molecules bind to receptors on the membrane of the postsynaptic neurone

6. The receptor molecules stimulate the generation of a new nerve impulse in the postsynaptic neurone

What is positive phototropism?

When the shoot grows towards light

What is negative phototropism?

When the root grows away from light

What is positive geotropism?

When the root grows towards the direction of gravity

What is negative geotropism?

When the shoot grows away from the direction of gravity

What is positive hydrotropism?

When the root grows towards water

What does the hormone auxin do?

Auxin stimulates new cells to grow longer or elongate

What happens to auxin when light shines all around the tip?

Auxin is distributed evenly throughout and the cells in the shoot grow at the same rate

What happens to auxin when the light shines on the shoot from one side?

Auxin produced in the shoot tip concentrates on the shaded side so:

• shaded side cells elongate and grow faster than the cells on the sunny side

• Shoot grows towards the direction of light, max psis

What are gibberellins important for?

They are plant hormones that are important in initiating seed germination, inducing flowering and fruit growth

What is ethene?

A gas released by plants which controls cells division and ripening of fruits

What is the gel