Topic1.6 - Nervous System & Hormones

Question 1

The action of nerves compared to the action of hormones

Answer 1

The action of nerves is fast and short-lived.

The action of hormones isn’t as fast but has longer lasting effects.

Question 2

Stimuli

Answer 2

Changes in the environment

Question 3

The 3 components and basic sequence of sensing and responding to stimulus in an animal nervous system are…

They are linked by…

Answer 3

Receptors
Coordinator
Effector

…linked by neurones (nerve cells)

Question 4

Receptors

Answer 4

Receive and detect the stimulus (e.g. pressure sensors in the skin)

Question 5

Coordinator

Answer 5

Determines the response (the brain and the spinal cord)

Question 6

Effector

Answer 6

Carries out response (e.g. biceps muscle)

Question 7

The eye is an…

and contains…

Answer 7

an advanced receptor

contains cell types that are sensitive to light

Question 8

What are the purposes of the fluids in the eye (aqueous humour and vitreous humour)?

Answer 8

Provide support

Allow light to pass through to the retina

Question 9

The iris consists of 2 types of muscle:

Answer 9

Radial muscles are like the spokes of the wheel and circular muscle which forms rings around the pupil.

Question 10

Bright light:
Risk
Action of muscles
Effect of pupil diameter
Amount of light entering eye

Answer 10

Bright light can damage the cells of the retina leading to blindness.
Circular muscles contract, radial muscles relax.
Pupil diameter decreases.
Amount of light entering eye is decreased.

Question 11

Dim light:
Risk
Action of muscles
Effect of pupil diameter
Amount of light entering eye

Answer 11

Low light level can result in not enough light reacting to form an image.
Circular muscles relax, radial muscles contract.
Pupil diameter increases.
Amount of light entering eye is increased.

Question 12

Light is focussed onto the retina by…

This allows…

Answer 12

Changing the shape of the lens

Both near and far objects to be seen clearly (accommodation)

Question 13

Eye focussed on distant object

Light rays
Lens

Answer 13

Light rays arrive parallel, cornea refracts rays, lens is thin as additional refraction is necessary to focus light on retina.

Ciliary muscles relax, suspenseful ligaments pulled tight , lens pulled thin

Question 14

Eye focussed on near object

Light rays
Lens

Answer 14

Light rays diverge, cornea refracts rays, lens is thicker as additional refraction is necessary to focus light on retina.

Ciliary muscles contract, suspenseful ligaments slackened , lens allowed to bulge

Question 15

Nerve cells are specially adapted to carry electrical impulses through the nervous system:

Answer 15

> long length - to carry impulses long distances
insulating sheath - to allow rapid transmission of impulses
branching ends - to receive or pass impulses from or to many other nerve cells

Question 16

Neurons 1,2,3

Answer 16

1- sensory
2- association
3- motor

Question 17

Synapses

Answer 17

Tiny gaps between nerve cells

Question 18

Process of impulses passing from one nerve to the next

Answer 18

(1) impulse reaches synaptic bulb (end of neurone)
(2) vesicles containing transmitter move towards cell membrane at synapse
(3) vesicles release neurotransmitter into gap
(4) neurotransmitter diffuses across gap
(5) neurotransmitter reaches membrane of next cell
(6) when enough neurotransmitter reaches next cell an impulse will occur
(7) impulse travels along next cell
(8) the used neurotransmitter is broken down by an enzyme

Question 19

Voluntary actions

Answer 19

We have conscious control over these

Question 20

Reflex actions

Answer 20

We aren’t conscious over these actions. They are much faster as they use a pathway of nerves called the reflex arc that does away with ‘thinking time’. They are used by the body for protection.

Question 21

Role of insulin

Answer 21

Meal rich in carbohydrates ->

Blood glucose level increases ->

Pancreas releases insulin ->

Insulin decreases blood glucose by: (i) increasing rate of respiration in liver and muscle (ii) converts glucose to glycogen for storage in liver and muscle

Question 22

The mechanism that insulin uses to control blood glucose levels

Answer 22

Negative feedback - ensures that changes are reversed and returned back to the set level. When normal blood glucose levels are restored (due to action of insulin) the pancreas will no longer need to release insulin.

Question 23

Role of glucagon

Answer 23

Involved in increasing blood sugar levels during exercise or when blood glucose levels fall.

Glucagon acts on the cells of the liver causing them to convert glycogen back into glucose.

Question 24

Diabetes

Answer 24

The condition where people fail to produce enough insulin or fail to respond to it correctly.

Question 25

Symptoms of diabetes

Answer 25

> high blood glucose levels
> glucose in the urine
> excessive thirst
> lethargy
> frequent need to urinate

Question 26

Long term dangers if diabetes is left untreated

Answer 26

> kidney damage
eye damage
stroke
heart disease

Question 27

What must diabetics do?

Answer 27

Diabetics must test their blood glucose levels and may need to inject insulin.

Question 28

Why can’t insulin be taken in a tablet?

Answer 28

The hormone would be digested in the stomach

Question 29

If too much insulin is taken…

Answer 29

Blood glucose levels can fall too low resulting in a ‘hypo’ (hypoglycaemia)

Question 30

Phototropism

Answer 30

Parts of a plant above the ground most often grow towards light as this should increase the rate of growth as more photosynthesis can occur.

Question 31

Hormone responsible for phototropism

Answer 31

Auxin

Question 32

The action of auxin

Answer 32

(1) auxin diffuses away from the tip of the shoot into the area where cells are actively growing
(2) auxin causes the cells t elongate
(3) if light is coming from directly above or from all side with similar intensity the auxin is distributed evenly and therefore all cells elongate by the same amount
(4) the shoot will therefore grow straight up
(5) if light is hitting the shoot from one side, auxin diffuses into the shaded side away from the light
(6) the cells on the shaded side become longer than those on the illuminated side and the shoot will curve towards the light
(7) more light will be absorbed by the photosynthetic parts of the plant resulting in an increased growth rate

Question 33

Commercial uses of plant hormones

Answer 33

> selective weed killers
rooting powder
promoting flower and fruit formation

Question 34

Selective weed killers

Answer 34

Hormone stimulates such a high rate of uncontrolled growth that plant cannot be sustained.

Benefit: hormones only act on broad leafed plants (weeds) but not on narrow leafed grasses and cereals

Question 35

Rooting powder

Answer 35

Hormone stimulates certain cells to develop the features of root cells (they make stems quickly develop roots).

Benefit: can be used in horticulture to allow growth of new plants from cuttings.

Question 36

Promoting flower and fruit formation

Answer 36

Hormone causes flowers to develop - these flowers can be pollinated to allow development of seeds and fruits.

Benefits:
> allows moe fruit to be produced e.g. there are adverse weather conditions or there’s a lack of natural pollinators
> can be used to produce seedless fruit
> can speed up or slow down fruit ripening (useful for travelling)