Response to stimuli

Question 1

Define taxis

Answer 1

Movement of organism whose direction is determined by a stimulus

Question 2

Define kinesis

Answer 2

Movement that is not towards or away from stimulus; the more unpleasant the stimulus, the more frantic the random movements

Question 3

Define tropism

Answer 3

Growth of part of a plant in response to a directional stimulus

Question 4

The nervous system splits into…

Answer 4

• peripheral

- central

Question 5

The peripheral nervous system splits into…

Answer 5

• somatic

- autonomic

Question 6

The autonomic system splits into…

Answer 6

• sympathetic

- parasympathetic

Question 7

Why are reflex arcs important?

Answer 7

• protect from danger; response is rapid as there are only 3 neurones involved
• involuntary; does not require decision from brain, so it can carry on performing other tasks

Question 8

What does the sympathetic nervous system do?

Answer 8

• increase heart rate and speeds up any activity

- prepares us in stressful situations by heightening our awareness

Question 9

Changes of heart rate are controlled by…

Answer 9

Medulla oblongata in brain

Question 10

The medulla oblongata receives info from which receptors (and where are they found)?

Answer 10

• chemoreceptors; found in walls of carotid arteries

- pressure receptors; found in walls of carotid arteries and aorta

Question 11

Describe effect of increased CO2 in blood on heart rate

Answer 11

1. Low pH is detected by chemoreceptors
2. They increase frequency of impulses to centre in MO that increases heart rate
3. Centre increases impulses via sympathetic system to SAN, which increases heart rate
4. Increased blood flow leads to more CO2 being removed, pH returns to normal

Question 12

Give the features of receptors

Answer 12

• specific to 1 type of stimulus

- produce a generator potential by acting as a transducer (convert 1 type of energy to 1 that is recognised by body)

Question 13

Describe how pacinian corpuscle produces an action potential

Answer 13

1. Pressure is applied to receptor (stimuli)
2. This changes the shape of the stretch-mediated Na+ channel, opening it and thus producing a rapid influx of Na+
3. Membrane is depolarised, thereby producing a generator potential
4. This in turn creates an action potential

Question 14

Define visual acuity

Answer 14

Ability to distinguish fine detail

Question 15

Why do rod cells produce low visual acuity?

Answer 15

• many rod cells are connected to 1 bipolar cell, so only 1 impulse is generated regardless of how many neurones are stimulated. Different sources of light are not distinguished

Question 16

Why are cone cells only receptive to high light intensity?

Answer 16

• each cell is connected to 1 bipolar cell, meaning a generator potential is only reached if light intensity is high enough to reach threshold value (cannot be combined)

Question 17

Where are the cone cells concentrated, and why?

Answer 17

• the fovea, because that is where the highest intensity of light is recieved

Question 18

How do cone cells produce colour images?

Answer 18

• there are 3 different types, which respond to different wavelengths of light