Coordination and response

Question 1

Nerve impulse

Answer 1

an electrical signal that passes along nerve cells called neurones

Question 2

Human nervous system

Answer 2

Allows for coordinated movement and constant internal environment to be maintained.
-CNS: Central nervous system, consisting of
brain and spinal cord
-PNS: peripheral nervous system, made up of nerves and receprtors

Question 3

Mylein sheath

Answer 3

-fatty layer that surrounds the axon. The sheath acts as an insulator and speeds up nerve impulses.

Question 4

voluntary and involuntary actions

Answer 4

• Voluntary actions uses conscious control, and is slower response
• Involuntary actions does not use conscious control and is faster response.

Question 5

Identify motor (effector), relay (connector) and sensory neurones from diagrams

Answer 5

• sensory neurones: Carries impulses from a receptor to brain and spinal cord
• relay (connector): Carries impulses between different parts of the central nervous system
• motor (effector)

Question 6

simple reflex arc

Answer 6

1. Receptor: Stimulus such as heat is detected by recptors
2. Sensory neurone: Receptor send an impulse down sensory neuron to spinal cord
3. Relay neurone: In CNS passes the impulse to motor neuron
4. Motor neurones: Impulse travels along motor neuron to effector
5. Effector:

Question 7

reflex action

Answer 7

A means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands)

Question 8

Synapse

Answer 8

a junction between two neurones

Question 9

structure of a synapse, How impulse arrives is passed at a synapse

Answer 9

1. An impulse arrives at the end of the presynaptic neuron
2. Vesicles move towards, and fuse with the presynaptic membrane, this releases neurotransmitters into the synaptic cleft.
3. The neurotransmitters diffuse across the synaptic cleft (down concentration gradient)
4. Neurotransmitters attach to the receptors of the postsynaptic membrane
5. This triggers an impulse which travels along the postsynaptic neuron
6. The neurotransmitters are recycled or destroyed after an impulse is sent.

Question 10

how an impulse triggers the release of a neurotransmitter from vesicles into the synaptic gap and how the neurotransmitter diffuses across to bind with receptor molecules, in the membrane of the neurone after the synaptic gap, causing the impulse to continue

Answer 10

Fusion of a vesicle with the presynaptic membrane causes neurotransmitters to be released into the synaptic cleft.

3. The neurotransmitters diffuse across the synaptic cleft (down concentration gradient)
4. Neurotransmitters attach to the receptors of the postsynaptic membrane
5. This triggers an impulse which travels along the postsynaptic neuron
6. The neurotransmitters are recycled or destroyed after an impulse is sent.

Question 11

in a reflex arc

Answer 11

the synapses ensure that impulses travel in one direction only

Question 12

Many drugs, e.g. heroin, act upon synapses

Answer 12

Stimulants such as caffeine, cause a release of neurotransmitters such as dopamine and serotonin into the synapses, whereas depressants such as heroin and alcohol, inhabits synapses by blocking the receptors on the presynaptic neuron so that impulses cannot be sent

Question 13

Sense organs

Answer 13

groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals

Question 14

Identify the structures of the eye, limited to cornea, iris, pupil, lens, retina, optic nerve and blind spot

Answer 14

…

Question 15

Function of each part of the eye

Answer 15

– cornea: clear layer that coats the iris and refracts light
– iris: controls how much light enters pupil, by contacting and dilating the pupil
– lens: focuses light onto retina
– retina: contains light receptors, some sensitive to light of different colours Rod and cone cells, AKA photoreceptors
– Optic nerve: carries impulses to the brain

Question 16

The pupil reflex in terms of light intensity and antagonistic action of circular and radial muscles in the iris

Answer 16

Pupil of the eye expands and contracts to control the amount of light that enters the eye, Carried out by circular and radial muscles, that work antagonistically.

• Low light intensity: Pupil dilates to allow more light in by relaxing circular muscles and contracting radial muscles.
• High light intensity: Pupil constricts to limit amount of light entering the eye, By relaxing radial muscles and contacting circular muscles. To prevent eye being damage by bright light

Question 17

accommodation to view near and distant objects in terms of the contraction and relaxation of the ciliary muscles, tension in the suspensory ligaments, shape of the lens and refraction of light

Answer 17

Ciliary muscles and suspensory ligaments change their shape to focus on near and far objects. which work antagonistically.

• To focus on near object, Ciliary muscles contract whilst suspensory ligaments slackened, allowing the lens to bulge.
• To focus on distant objects: Ciliary muscles relax whilst suspensory ligaments contract, making lens thinner and less curved.

Question 18

distribution of rods and cones in the retina of a human

Answer 18

cones are present in the center of the fovea. Rods are present at high density throughout most of the retina

Question 19

function of rods and cones

Answer 19

• Rod: Used for monochromatic night vision as more sensitive to low levels of light.
• Cone: Used for colour vision in bright light. RGB, Three types of cone cells, sensitive to each colour.

Question 20

Position of the fovea

Answer 20

In a region of the retina

Question 21

Hormone

Answer 21

a chemical substance, produced by a gland and carried by the blood, which alters the activity of one or more specific target organs

Question 22

endocrine glands and their secretions

Answer 22

• Adrenal glands (top of kidney): Secretes adrenalin, which is secreted during “fight” or “flight” response. it leads to increased heart rate and widening of pupils. Also causes glucagon to be converted into glucose in cells so it can be used for respiration for energy. As heart rate increase, provides more oxygen for respiration.
• Pancreas: Secrete insulin, which maintains blood glucose concentration.
• Testes: secretes testosterone, maintains muscle and bone strength and plays a role in reproduction.
• Ovaries: Secrete Oestrogen, regulates female reproductive system.

Question 23

role of the hormone adrenaline in the chemical control of metabolic activity, including increasing the blood glucose concentration and pulse rate

Answer 23

leads to increased heart rate and widening of pupils. Also causes glucagon to be converted into glucose in cells so it can be used for respiration for energy. As heart rate increase, provides more oxygen for respiration.

Question 24

Compare nervous and hormonal control systems in terms of speed and longevity of action

Answer 24

• Impulse travel along neurons whereas hormones travel in the blood.
• Nerve impulses much quicker than hormones, as hormones must be transported in blood, whereas nerve impulses can travel along specialized nerve cells.
• Nerve impulses are short-term whereas hormonal response are long-lasting
• Endocrine system use chemicals (hormones), whereas nervous system uses electrical signals.

Question 25

Gravitropism

Answer 25

a response in which parts of a plant grow towards or away from gravity

Question 26

Phototropism

Answer 26

a response in which parts of a plant grow towards or away from the direction from which light is coming

Question 27

Gravitropism and phototropism in shoots and roots.

Answer 27

Gravitropism:
-shoots are negatively gravitropic, as they grow upwards against gravity, whereas roots are positively gravitropic
Phototropism:
-Plant shoots are positively phototrophic, as they more towards light, in order to allow the plant to absorb more light to photosynthesize. Plant roots are negatively phototrophic as they move away from light

Question 28

role of auxin in controlling shoot growth

Answer 28

• Auxin made in shoot tip, which are transported down the shoot.
• Light causes auxin to move to the shady side of the root
• Auxin stimulates cell elongation in shady side
• Cells grow faster on shady side thus shoot bends towards light

Question 29

use in weedkillers of the synthetic plant hormone 2,4-D

Answer 29

-Weedkillers used to selectively kill plants, 2,4-D is a synthetic plant hormone. when a plant is exposed to 2,4-D, it results in uncontrolled growth resulting in plants death.