Irritability

Question 1

stimulus

Answer 1

a change in the internal and external environment of an organism that initiates a response

Question 2

response

Answer 2

a change in an organism or part of an organism which is brought about by stimulus
secretion of substances may occur

Question 3

receptor

Answer 3

the part of the organism that detects the stimulus

in animals the sense organs contain the receptors
the eyes, ears, skin, tongue and nose contain specialised receptor cells that detect stimuli

in plants the very tips of roots and shoots act as the receptors

Question 4

effector

Answer 4

the part of an organism that responds to the stimulus

in animals, muscles and glands are effectors
in plants, the regions just behind the tips of roots and shoots and the petioles of leaves act as effector

Question 5

RESPONSES OF GREEN PLANTS TO STIMULI

Answer 5

plants respond to stimuli by part movements or growth movements, WHICH AID IN SUURVIVAL

Question 6

PART MOVEMNTS BY CHNAGES IN THE TURGIDITY OF CELLS

mimosa

Answer 6

leaves of some plants respond to touch or strong winds by folding to protect them from damage/being damaged

Question 7

PART MOVEMNTS BY CHNAGES IN THE TURGIDITY OF CELLS

tamarind

Answer 7

leaves of some plants respond to changing light intensities by folding at night and opening in the morning to access light for photosynthesis

Question 8

PART MOVEMNTS BY CHNAGES IN THE TURGIDITY OF CELLS

Answer 8

flowers of some plants respond to changes in light intensities, opening in the morning to expose the stamens and carpels for pollination, closing at the night e.g. hibiscus

other flowers close in the morning and open at night e.g. night flowering cactus

Question 9

plants part movements to stimuli

Answer 9

plants of insectivorous plants move to trap prey venus fly trap snaps to catch prey

Question 10

growth movements in plants

Answer 10

plants growing in response to stimulus

shoots grow and bend towards unilateral light. maximises the amt of light available for photosynthesis.

in the absence of light or illuminated evenly, plants grow upwards in serach for light or to maximise the light available against gravity

growing upwards also puts flowers in the best position for pollination and fruits and seeds for dispersal.

Question 11

growth movemnts in plants as a response to stimuli

Answer 11

roots grow and bend towards gravity which anchors the plant to the ground and allows to obtain minerals and water, roots also grow towards water maximisng the amount of water available for photosynethesis

Question 12

responses of invertebraes

Answer 12

invertebrates such as millipedes, earthworms, woodlice move their whole bodies towards or away from stimuli.

their responses aid in their survival and can be investigated using A CHOICE CHAMBER dry or moist environment hot or cold

Question 13

RESPONSE OF INVERTEBRATE
to light

Answer 13

most away from light into the darkness, this makes the organism harder to be seen by predators

Question 14

RESPONSE OF INVERTEBRATE
to moisture

Answer 14

most move away from dry areas into areas with moisture
beacuse, prevents desiccation especially in organisms that don’t have a waterproof coverings

Question 15

RESPONSE OF INVERTEBRATE
to temperature

Answer 15

move away from very low and very high temperatures
because, prevents extremes of temperatue affecting enzyme activity

Question 16

RESPONSE OF INVERTEBRATE
to chemicals and touch

Answer 16

chemicals, move toward chemicals given off by food and move away from harmful chemicals becuase, enables organisms to find food which is essential for survuval and preevnt being hurt by harmful chemicals such as pesticides

touch:
move away or curl up when touched, protects them from PREDATORS AND HELPS ORGANISMS EXCAPE PREDATORS

Question 17

nervous system composed of

Answer 17

neurones and nerve cells and is divided into two parts:
the central nervous system
peripheral nervous system

Question 18

central nervous system (CNS)

Answer 18

brain and spinal cord

Question 19

peripheral nervous system (PNS)

Answer 19

consists of cranial and spinal nerves that connect the CNS to all parts of the body.

Question 20

neurones

Answer 20

make up both the CNS and PNS and they transmit messages called nerve impulses

all neurons have a cell body with thin fibres of cytoplasm extending from it called NERVE FIBRES

Question 21

differnce between dendrites and axons

Answer 21

dendrites are nerve fibres that carry impulses towards the cell body

axons are nerve fibres that carry impulses from the cell body EACH NEURONE HAS ONLY ONE AXON

Question 22

THREE TYPES OF NEURONES

Sensory neurones
motor neurones
relay neurones

Answer 22

transmit impulses from receptors to the CNS
transmit impulses from the CNS to effectors
transmit impulses throughOUT the CNS, link the sensory and motor neurones

Question 23

what are nerves made up of

Answer 23

bundles of nerve fibres of sensory and/or motor neurones surrounded by connective tissue.

Question 24

what are the brain and spinal cord made up of?

Answer 24

mainly of relay neurones and the cell bodies of motor neurones.

Question 25

myelin sheath

Answer 25

fatty sheath or layer around nerves (including those in the CNS) to insulate and protect the nerve fibre
and speed up transmission of impulses

It is made up of protein and fatty substances. This myelin sheath allows electrical impulses to transmit quickly and efficiently along the nerve cells. If myelin is damaged, these impulses slow down.

Question 26

node of Ranvier

Answer 26

constriction in the myelin sheath

The nodes of Ranvier are gaps along the myelin sheath that covers the axon of neuron cells. They function to recharge the action potential that runs along the axon.

Because of the nodes of Ranvier the action potential “jumps” from one node to the next
If nodes of Ranvier were not present along an axon, the action potential would propagate very slowly;

Question 27

dendrite

Answer 27

long AND to the cell

Question 28

AXON

Answer 28

short AND away from the cell

Question 29

synaptic knob

Answer 29

Synapses connect neurons and help transmit information from one neuron to the next. When a nerve signal reaches the end of the neuron, it cannot simply continue to the next cell. Instead, it must trigger the release of neurotransmitters which can then carry the impulse across the synapse to the next neuron.

A synaptic knob is a terminal branch/swelling at the end of a sensory neuron. contain and releases neurotransmitters. Neurotransmitters are chemicals that the body makes to relay a message between neurons and other cells.

Question 30

why do relay neurones not have myelin sheaths

Answer 30

The relay neuron are found inside the central nervous system, henceforth don’t need insulation.

Myelinated neurons are neurons whose axons are surrounded by myelin; the myelin has has an insulating effect and allows the axons to conduct neural impulses faster - but at some metabolic cost, so neurons are not myelinated unless there is a significant advantage to they’re being able to conduct faster.

Question 31

Transmitting impulses between neurones

Answer 31

adjacent neurones do not touch. there are tiny gaps called synapses between the synaptic knobs at the end of one axon and the dendrites or cell body body of adjacent neurones. Chemicals called neurotransmitters are released into the synapses by the the synaptic knobs. these chemicals cause impulses to be set up in adjacent neurones. this ensures that impulses travel in one direction only.

Question 32

Coordinating function of the CNS

Answer 32

the job of the CNS is to coordinate the activities of all parts of the body. It gathers information from the receptors via sensory neurones. It then processes this information and send messages out to effectors via motor neurones so that the most appropriate action can be taken. Messages are based between the brain and spinal cord by relay neurones.

Question 33

learned reflex action

Answer 33

On the other hand, learned reflexes, also referred to as acquired or conditioned reflexes, result from experience and training. These reflexes develop through repeated exposure to certain stimuli, leading to a conditioned response.

Question 34

simple reflex action

Answer 34

a reflex action is rapid, automatic, involuntary response to a stimulus by a muscle or gland. e.g. automic withdrawal of hand when it touches something hot a hot object

simple reflex actions happen without conscious thought, they are not learned and aid in survival.

Question 35

examples of a learned reflex action

exmaples of a simple reflex action

Answer 35

dog jumping up when his owner says the word ‘food’
Trained dog salivates when you ring a bell

Eyes closed when anything enters into it, Hand taken away when pierced with a needle peristalsis

Question 36

unconditioned vs conditioned response

Answer 36

An unconditioned stimulus causes a response without any prior learning on the part of the subject. The response is automatic and occurs without thought.

In contrast, a conditioned stimulus produces a reaction only after the subject has learned to associate it with a given outcome.

Question 37

the pathway between a receptor and an effector is

Answer 37

known as a reflex arc
involves the following:
1. a receptor (which detects the stimulus)
2. a sensory neurones (impulse and carries the impulse to the CNS
3. a relay neurone (in the CNS, which carries the impulses to a motor neurone)
4. a motor neurone (carris the impulse away from the CNS)
5. an effector (RESPONDS TO STIMULUS)

Question 38

simple reflexes are classified into:

Answer 38

cranial e.g. sneezing, pupil reflex, blinking, coughing, saliva production

and spinal reflexes e.g. knee jerk reflex

Question 39

cranial reflexes

Answer 39

in cranial reflexes, impulses pass through the brain. EXAMPLE A BRIGHT LIGHT

1. stimulus (bright light)
2. receptor (light sensitive cells of retina)
3. sensory neurone (carries impulses to the CNS (relay neurone))
4. relay neurone (in the CNS, carries impulses to motor neurone)
5. motor neurone ( carries impulses away from CNS)
6. effector (a mucsle or gland resoonse so circular muscles of iris)
7. response (muscles contract reducing diameter of the pupil)

Question 40

SPINAL REFLEX

Answer 40

IMPULSES PASS THROUGH THE SPINAL CORD

knee jerk reflex and withdrawl reflex hot object
1. stimulus, being hit just below the knee cap
2. receptor, detects stimulus and the strech receptor in the muscle is stimulated
3. impulses trave along a SENSORY NEURONE to the spinal cord i.e CNS
4. impulses travel DIRECTLY TO THE MOTOR NEURONE in the spinal cord
5. effector, impulses travel along the motor neurone to the extensor muscle of the leg
6. response, extensor muscle contracts causing the lower leg to rise

Question 41

growth movements of plants garvity and light

Answer 41

light phototropism
Positive phototropism is growth towards a light source; negative phototropism is growth away from light.

gravity geotropism
The upward growth of plant shoots is an instance of negative geotropism ; the downward growth of roots is positive geotropism.

Question 42

amoeba

Answer 42

a unicellular protoctist, lacks any specialised structures to coordinate a response. it however does respond in definte ways such as phagocytosis (engulfing objects with the use of pseudopodia) when in contact with a food source

Question 43

phagocytosis

Answer 43

cellular process for ingesting and eliminating particles found in many types of cell organsims have pseudopodia (false feet) secrete digestive enzymes to break down the object

Question 44

Nervous system

Answer 44

Your nervous system is your body’s command center. It’s made up of your brain, spinal cord and nerves.

**A system of regulation and communication which coordinates responses to stimuli and together with the endocrine system maintains/controls homeostasis

Answer 45

Endotherms use internally generated heat to maintain/regulate body temperature. Their body temperature tends to stay steady regardless of their external environment.
birds, humans, fishes, invertebrates

Ectotherms depend mainly on external heat sources, and their body temperature changes with the temperature of the environment.
reptile/amphibian

Question 46

homeostasis

Answer 46

maintenance of a constant internal environment.
any self-regulating process by which an organism tends to maintain stability while adjusting to conditions that are best for its survival.
e.g. temperature regulation

Question 47

what is so special about response in mammals as to animals or plants, or fungi, or protoctists, or prokaryotae

Answer 47

in complex organisms, such as mammals, there are specialised structures –which form the nervous system, coordinating/providing/initiating a more complex, advanced and more intelligent response as the human brain is also a component.

Question 48

riding a bike

Answer 48

eg of conditioned reflex

Question 49

why is the central nervous system important/needed?

Answer 49

perhaps it would be quicker for pain receptors in your hand to send nerve impulses to ur arm muscles to tell it to move ur hand away from the hot plate rather than all the way to the spinal cord and back.
but it would not be enough to tell animals to vary their behaviour in certain situations

with the CNS it is possible to give a more advanvced modified reaction for example, you pick up a hot plate without the cns, the pain receptors would send impulses to ur hand muscles telling u to drop it, which would break the plate but with the cns involved it, there is another message saying don’t drop it perhaps it’s a grandmas or yk it will make a mess or it will be loud