Chapters 9, 10 + 11 - Responses

Question 1

What is a stimulus?

Answer 1

A detectable change in the internal or external environment of an organism that produces a response in the organism.

Question 2

What is a receptor?

Answer 2

A cell which is able to detect changes in its environment.

Question 3

What is an effector?

Answer 3

An organ which responds to stimulation by a nerve impulse and brings about a response or change - muscles and glands.

Question 4

What is taxis?

Answer 4

A form of behaviour in which an organism moves either directly towards or away from a stimulus.

Question 5

What is kinesis?

Answer 5

A form of behaviour in which the response of the animal is proportional to the intensity of the stimulus - doesn’t respond to direction.

Question 6

What is a tropism?

Answer 6

A growth movement of part of a plant in response to a directional stimulus.

Question 7

What is the central nervous system?

Answer 7

Made up of the brain and spinal cord.

Question 8

What is the peripheral nervous system?

Answer 8

Made up of pairs of nerves that originate from the brain or spinal cord (divided into sensory and motor neurones).

Question 9

What is the spinal cord?

Answer 9

A column of nervous tissue that runs along the back and lies inside the vertebral column for protection.

Question 10

What is a reflex arc?

Answer 10

The pathway of neurones involved in a reflex.

Question 11

What does the sympathetic nervous system do?

Answer 11

Speeds up activity - stimulates effectors.

Question 12

What does the parasympathetic nervous system do?

Answer 12

Inhibits effectors, slowing down any activity.

Question 13

Which part of the brain controls heart rate?

Answer 13

Medulla oblongata.

Question 14

What is the pacinian corpuscle?

Answer 14

A type of pressure receptor, most numerous in the fingers and toes.

Question 15

What is a rod cell?

Answer 15

A type of light-sensitive cell found in the retina of the eye - can’t decipher between colours.

Question 16

What is rhodopsin?

Answer 16

A light-sensitive pigment found in the rod cells of the eye - broken down into opsin and retinine.

Question 17

What are cone cells?

Answer 17

A colour-sensitive receptor cell found in the retina of the eye.

Question 18

What are plant growth factors

Answer 18

Chemicals produced by a plant which are involved in the control of various aspects of its growth and development.

Question 19

What does IAA stand for?

Answer 19

Indoleacetic acid

Question 20

What are dendrons?

Answer 20

Small extensions of a nerve’s cell body which subdivide into smaller branched fibres, called dendrites, that carry nerve impulses towards the cell body.

Question 21

What is an axon?

Answer 21

A single long fibre that carries nerve impulses away from the cell body.

Question 22

What are Schwann cells?

Answer 22

Cells that surround the axon, protecting it and providing electrical insulation. Also carry out phagocytosis and play a part in nerve regeneration.

Question 23

What is the myelin sheath?

Answer 23

Forms a covering to the axon, made up of membranes of Schwann cells, rich in myelin. Myelinated neurones transmit nerve impulses faster.

Question 24

What are nodes of Ranvier?

Answer 24

Gaps between adjacent Schwann cells where there is no myelin sheath.

Question 25

What is a resting potential, with its usual value?

Answer 25

The difference in charge across the plasma membrane of a nerve cell. -70mV.

Question 26

What is an action potential, with its usual value?

Answer 26

The change which occurs in the electrical charge across the plasma membrane of a nerve cell during the passage of a nerve impulse. 40mV.

Question 27

What is the refractory period?

Answer 27

The short recovery period which occurs immediately after the passage of a nerve impulse along the axon of a nerve cell.

Question 28

What is the all-or-nothing principle?

Answer 28

When an action potential is produced in a nerve cell, it is always the same size.

Question 29

What is the threshold value?

Answer 29

The level of stimulus which triggers an action potential.

Question 30

What is a synapse?

Answer 30

A junction between nerve cells.

Question 31

What is a neurotransmitter?

Answer 31

A substance that is responsible for the transmission of information across a synapse.

Question 32

What is summation?

Answer 32

A process which occurs in synapses by which a number of weak stimuli can lead to the generation of a nerve impulse. Spatial - a number of presynaptic neurones together exceed the threshold value.
Temporal - a single presynaptic neurone releases neurotransmitter many times over a short period to exceed the threshold value.

Question 33

What are inhibitory synapses?

Answer 33

When protein channels carrying chloride ions on the postsynaptic membrane are made to open. Chloride ions diffuse in, decreasing the likelihood of an action potential being created.

Question 34

What is actin?

Answer 34

A protein found in the myofibrils of skeletal muscle, they form the thin filaments in the I-band.

Question 35

What is myosin?

Answer 35

Protein which makes up the thick filaments in the myofibrils of skeletal muscle.

Question 36

What are slow muscle fibres?

Answer 36

These allow sustained, aerobic muscle contractions and play an important part in maintaining body posture.

Question 37

What are fast muscle fibres?

Answer 37

These produce rapid, powerful contractions which make them very important in anaerobic activities.

Question 38

What is a neuromuscular junction?

Answer 38

A synapse between a nerve cell and a muscle.

Question 39

What is a sarcomere?

Answer 39

One of the basic structural units of which skeletal muscles are composed - a section of myofibril between z-lines.

Question 40

What is phosphocreatine?

Answer 40

A molecule which break down to give creatine, this liberates energy, which can be used to resynthesise ATP in muscles.