1
Q
stimulus definition
A
a change in the environment that can be detected by an organism
2
Q
the human nervous system consists of:
A
- The CNS (central nervous system)
- The PNS (peripheral nervous system)
3
Q
what is the CNS composed of and what does it do?
A
- Composed of:
- brain and spinal cord- Responsible for coordinating all reactions and nervous communication around the body
4
Q
what is the PNS composed of and what does it do?
A
- Composed of:
- Nerves in the other parts- Responsible for transmitting the impulses from the CNS to all parts of the body
5
Q
3 main types of neurons
A
- sensory neurone
- motor neurone
- relay neurone
6
Q
sensory neurone
A
- Transfer nerve impulses from receptor cells to the spinal cord when a stimulus is detected.
7
Q
motor neurone
A
- Transfer nerve impulses from the brain or spinal cord to effectors (such as muscles)
8
Q
relay neurone
A
- Connect one neuron to the next
- Found in the brain
- Make links between the sensory neurons and the motor neurons in the spinal cord
9
Q
synapse
A
- Junction between two neurons
- Allows an impulse to travel from an axon terminal of one neuron to a dendrite in another neuron
10
Q
how do synapses work?
A
- Axon terminals contain tiny, bubble-like structures called vesicles
- Vesicles contain substances called neurotransmitters
- Receptor molecules in dendrites bind to neurotransmitters
11
Q
how do neurotransmitters travel across the synaptic cleft/synaptic gap?
A
by diffusion
12
Q
characteristics of reflex actions
A
- Rapid
- Automatic
- Innate (you don’t need to learn how to do them)
13
Q
what is the reflex arc?
A
- The pathway through the body that brings about a reflex action
- receptor → sensory neurone → relay neurone → motor neurone → effector
14
Q
receptor cells
A
- Cells that detect different stimuli
Include:
- Touch receptors in the skin
- Sound receptors in the ear
- Light receptors in the eye
- Taste (chemical) receptors in the nose, tongue and mouth
- Temperature receptors in the skin and brain
15
Q
effectors
A
- Produce a response
Eg. A muscle or a gland that produces a hormone
16
Q
sense organ
A
group of receptor cells that respond to a specific stimulus
17
Q
Light entering the eye travels in this direction:
A
- cornea → pupil → lens → optic nerve
18
Q
cornea function
A
refracts light, focusing it towards the retina
19
Q
lens function
A
refracts light, focusing it onto the retina
20
Q
iris function
A
controls the amount of light passing through the pupil
21
Q
retina function
A
responds to light levels and to light of different colors
22
Q
optic nerve function
A
carries nerve impulses from the retina to the brain
23
Q
in dim light…
A
- Pupil dilates
- Radial muscles contract
- Circular muscles relax
24
Q
in bright light…
A
- Pupil constricts
- Radial muscles relax
- Circular muscles contract
25
ciliary muscles function
- Control the shape of the lens
- Attached to the lens by suspensory ligaments
26
To focus light from distant objects onto the retina:
- Ciliary muscles relax
- Tension in suspensory ligaments increases
- Lens becomes thinner
- Light is refracted less strongly
27
To focus light from near objects onto the retina:
- Ciliary muscles contract
- Tension in suspensory ligaments decreases
- Lens becomes thicker
- Light is refracted more strongly
28
where are cones located
on the fovea
29
what do cones provide?
colour vision
3 types of cones:
- red
- blue
- green
30
where are rods distributed?
mostly around the sides of the retina
31
what do rods provide?
vision in dim light
32
hormones (4 points)
- Chemical substance produced by glands
- Transported in the blood
- Alters the activity of one or more specific target organs
- Endocrine system: series of glands that make hormones
33
the adrenal gland produces...
adrenaline
34
the pancreas produces..
insulin and glucagon
35
the ovary produces
oestrogen
36
the testis produces...
testosterone
37
effect of insulin and what it causes
- Effect of lowering blood glucose concentration
- Causes cells in the liver to remove glucose from the blood and store it as glycogen
38
How does Insulin lower blood glucose concentration?
insulin stimulates cells in the liver and tissues such as muscles to use glucose from the blood either to use it for respiration or to store it as glycogen
39
what does glucagon stimulate?
- Stimulates the breakdown of stored glycogen, releasing more glucose into the blood
40
what does adrenaline cause?
- Increased breathing rate
- Increased pulse rate
- Widened pupils in the eyes
41
homeostasis definition
- Maintenance of a constant internal environment within the body
42
what does homeostasis control?
- Body temperature
- Concentration of glucose in the blood
- Water levels
43
negative feedback definition
response which is the reverse to the change detected so that levels can return to normal.
eg, when it is cold you start to shiver, which increases again your body temperature
44
thermoregulation meaning
process that allows the body to maintain a constant core temperature
45
vasodilation
the widening of blood vessels that causes more blood to flow in the skin capillaries, so more heat is lost from the body
Vasodilation = heat loss
46
vasoconstriction
the narrowing of blood vessels that causes less blood to flow in the skin capillaries, so less heat is lost from the body
Vasoconstriction = less heat loss
47
what is meant by type 1 diabetes
- Pancreas does not make enough insulin
- Meaning the glucose in the blood cannot enter cells and is not converted into glycogen
48
type 1 diabetes symptoms
- Frequent urination (body is trying to secrete excess glucose)
- Increased thirst (due to frequent urination)
49
tropism definition
a response by a plant to a stimulus
50
geotropism
a response in which parts of a plant grow towards or away from gravity
51
phototropism
a response in which a plant grows towards or away from light
52
what do auxins do?
plant hormone that cause tropisms
biology IGCSE
flashcards
Decks in class (22)
# Cards
-
characteristics and classification of living organisms18
-
organization of organisms22
-
movement into and out of cells4
-
biological molecules10
-
enzymes10
-
plant nutrition5
-
leaf structure13
-
human nutrition63
-
transport in plants8
-
transport in animals32
-
diseases and immunity17
-
gas exchange in humans10
-
respiration5
-
excretion in humans11
-
drugs2
-
coordination and response52
-
reproduction59
-
inheritance29
-
variation and selection17
-
organisms and their environments23
-
human influences on ecosystems24
-
biotech and genetic modification4
