Topic 14

Question 1

The nervous system

Answer 1

Coordinates and regulates body functions
. Contains neurones through which electrical impulses travel along

Question 2

The nervous system: Mammalian nervous system

Answer 2

Central nervous system (CNS): brain and spinal chord
Peripheral nervous system (PNS): neurones outside CNS

Question 3

The nervous system: reflex actions

Answer 3

Rapid, automatic responses to stimuli that don’t involve the conscious part of the brain -> passage of nerve impulses in reflex action is called reflex arc

Question 4

The nervous system: sequence of events in a reflex arc

Answer 4

Stimulus -> receptor -> coordinator -> effector -> response
1. Stimulus detected by receptors
2. Impulses sent along sensory neuron to CNS
3. Impulses cross synapse between sensory and relay neurone -> impulses continue along relay neuron
4. Impulses cross synapse between relay and motor neuron -> impulses continue along motor neuron
5. Then impulses reach effector -> If it’s a muscle it contracts and if it’s a gland it secretes a hormone

Question 5

Types of neurons

Answer 5

. Sensory neurones
. Relay neurones
. Motor neurones

Question 6

Synapses

Answer 6

Junction between two neurones
- Structure:
. Vesicles containing neurotransmitters
. Synaptic gap
. Receptor proteins

Question 7

Nerve impulse passing through synapse:

Answer 7

1. Impulse stimulates release of a neurotransmitter molecules from vesicles into synaptic gap
2. Neurotransmitter molecules diffuse across gap
3. Neurotransmitter molecules bind with receptor proteins ( on 1 side so impulses have one direction) on next neuron
4. Impulse is then stimulated in next neurone

Question 8

Sense organs

Answer 8

Sense organ: group of receptor cells responding to specific stimuli -> light, sound, touch, temperatures and chemicals

Question 9

Structures of eye

Answer 9

Cornea: refelcts light
Iris: controls how much light enters pupil
Lens: focuses light onto retina
Retina: contains light receptors -> some sensitive to light of different colours
Optic nerve: carries impulses to brain

Question 10

Types of receptors in eyes: Rods

Answer 10

. Found in peripheral parts of retina
. Very light sensitive -> work well in dim light
. 1 type of rod gives info in black and white -> not colour vision

Question 11

Types of receptors in eyes: cones

Answer 11

. Found packed together in fovea
. Less light sensitive -> work best in bright light
. 3 types of cones give info in different colours -> colour vision

Question 12

The eyes: pupil reflex

Answer 12

Antagonisitic action of circular and radial muscles in iris
. To make pupil wider: radial muscles contract and circular mucles relax -> increases light that enters eye
. To make pupil smaller: circular muscles contract and radial muscles relax -> decreases light that enters eye

Question 13

The eyes: accomodation -> near objects

Answer 13

Eye focuses light on retina by changing the shape of the lens
- Near objects:
. Ciliary muscles contract -> slackens suspensory ligaments
. Lens becomes fat (more curved)
. Increases amount by which light is refracted

Question 14

The eyes: accomodation -> distant objects

Answer 14

• Distant objects:
  . Ciliary muscles relax -> suspensory ligaments pull tight
  . Lens goes thin (less curved)
  . Decreases amount by which light is refracted

Question 15

Hormones

Answer 15

A chemical substance produced by a gland and carried by the blood, which alters the activity of one or more specific target organs
. Endocrine glands: produce and secrete hormones

Question 16

Hormones: endocrine glands

Answer 16

. Adrenal glands: secrete adrenaline
. Ovaries: secrete oestrogen
. Testes: secrete testosterone
. Pancreas: secretes insulin and glucagon

Question 17

Hormones: adrenaline

Answer 17

Hormone secreted in ‘fight or flight’ situations
- Effects:
. Increased breathing rate
. Increased pupil diameter
. Causes heart muscle to contract more frequently and with more force -> heart rate increases
. Causes liver to breakdown it’s glycogen stores to release glucose -> blood glucose level increases

Question 18

Hormones VS nerve impulses: Hormone

Answer 18

. Slower message
. Act for long time

Question 19

Hormones VS nerve impulses: nerve impulses

Answer 19

. Very fast message
. Act for very short time

Question 20

Homeostasis

Answer 20

Maintenace of a constant internal environment
. Homeostatic control: kept using negative feedback systems -> body receptors detect a condition has gone above/below its normal level + trigger a response to bring level back to its set point again

Question 21

Internal body temperature -> mechanisms to reduce body temperature: hairs lie flat

Answer 21

Less air is trapped -> skin less insulated + heat lost easily

Question 22

Internal body temperature -> mechanisms to reduce body temperature: sweating

Answer 22

Water in sweat evaporates from skin surface taking heat from body

Question 23

Internal body temperature -> mechanisms to reduce body temperature: vasolidation

Answer 23

Arterioles near skin surface dilate + more blood through capillaries near skin surface -> heat loss

Question 24

Internal body temperatures -> mechanisms to increase body temperature: hairs stand up

Answer 24

Traps an insulating layer of air -> prevents heat loss

Question 25

Internal body temperatures -> mechanisms to increase body temperature: much less sweat

Answer 25

Reduces amount of heat loss

Question 26

Internal body temperatures -> mechanisms to increase body temperature: shivering

Answer 26

Muscles contract in spasms -> more heat produced from increased respiration

Question 27

Internal body temperatures -> mechanisms to increase body temperature: vasoconstriction

Answer 27

Arterioles near skin surface constrict + less blood through capillaries near skin surface -> less heat loss

Question 28

Controlling blood glucose: blood glucose too high

Answer 28

1. Insulin secreted by pancreas
2. Glucose from blood to liver and muscle cells
3. Insulin makes liver turn glucose into glycogen
4. Blood glucose reduced

Question 29

Controlling blood glucose: blood glucose concentration too low

Answer 29

1. Glucagon secreted by pancreas
2. Glucagon enters liver -> makes liver turn glycogen into glucose
3. Glucose released into blood by liver
4. Blood glucose increased

Question 30

Type 1 diabetes treatment: insulin therapy

Answer 30

. Insulin therapy: injecting insulin after meals -> glucose removed quickly once food digested

Question 31

Type 1 diabetes treatment: diet

Answer 31

Not eating too many simple carbohydrates

Question 32

Type 1 diabetes treatment: exercise

Answer 32

Helps remove excess glucose from blood

Question 33

Tropic response: gravitropism

Answer 33

Response which parts of a plant grow towards or away from gravity

Question 34

Tropic response: phototropism

Answer 34

Response which parts of a plant grow towards or away from a light source

Question 35

Shoot growth: Auxin

Answer 35

Plant hormone that chemically controls growth near tips of shoots -> produced in tips and diffuses unequally through plant from there due to light and gravity + stimulates cell elongation
. Phototropism and gravitoprism: examples of chemical control of plant growth

Question 36

Shoot growth: shoot grow towards light

Answer 36

1. Auxin accumulates on side that’s in shade when shoot tip exposed to light
2. Stimulates cells to elongate faster on shade side -> shoots bends towards light (positive phototropism)

Question 37

Shoot growth: shoot grow away from gravity

Answer 37

1. Auxin distributed unequally by gravity with more on lower side of tip
2. Stimulates cells of lower side to elongate faster -> shoots bends upwards (negative gravitropism)