Aqa Biol 9 - Sensory Reception

Front 1

What is a stimulus?

Back 1

A detectable change in the internal or external environment of an organism that produces a response

Front 2

What is good about the ability to respond to stimuli?

Back 2

Increases chances for survival - e.g. detecting extremes of temperature. Those that survive have a greater chance of raising offspring and passing on alleles - selection pressure favouring organisms with favourable responses (moving away from an unpleasant stimulus!)

Front 3

Which organs detect stimuli?

Back 3

Receptors

Front 4

What is the role of recepotrs?

Back 4

Transforming energy of a stimulus into another form of energy that can be processed by the organism

Front 5

What is an effector?

Back 5

Something that carries out the response

Front 6

What are the two ways of transporting information around the body?

Back 6

Hormonal and nervous system

Front 7

Stimulus -->...--> response

Back 7

Stimulus --> Receptor --> Coordinator --> Effector --> Response

Front 8

What is a taxes?

Back 8

A response whose direction is determined by the direction of the stimulus. An organism responds by either moving towards a favourable stimulus (positive taxes) or away from an unfavourable one (negative taxes).

Front 9

What is a kinesis?

Back 9

A response whereby the more unpleasant the stimulus is, the more rapidly the organism moves and the more rapidly it changes direction (so that it gets out of danger)

Stimulus is LESS directional

Front 10

What is a tropism?

Back 10

A growth movement of a plant in response to a directional stimulus (e.g. moving towards the light).

Front 11

What are the two major divisions of the nervous system?

Back 11

CNS (brain and spinal cord) and PNS (nerves that originate from either the brain or spinal cord)

Front 12

What is the PNS divided into? (The two neurones in it)

Back 12

Sensory and motor neurones

Front 13

Where do sensory neurones carry information from and to?

Back 13

From receptors towards the CNS

Front 14

Where do motor neurones carry information?

Back 14

Away from the CNS to EFFECTORS

Front 15

What is the motor nervous system divided into?

Back 15

The voluntary nervous system and autonomic nervous system (Carries nerve impulses to glands, smooth and cardiac muscle)

Front 16

What is the spinal cord?

Back 16

A column of nervous tissue that runs along the back and lies inside the vertebral column for protection

Front 17

The pathway of neurones involved in a reflex is known as a...

Back 17

...reflex arc

Front 18

How many neurones do reflexes involve, and what are they?

Back 18

Three - Sensory, intermediate and motor

Front 19

Describe the process of a reflex arc (7)

Back 19

Stimulus, receptor, sensory neurone, intermediate neurone, motor neurone, effector, response

Front 20

Why are reflex arcs important?

Back 20

Involuntary - do not require brain and thus it is not overloaded with situations where the response is always the same

Protection from harmful stimuli

Very fast - important in withdrawal reflexes

Front 21

What are the two sections of the autonomic NS?

Back 21

Sympathetic NS and parasympathetic NS (they are antagonistic)

Front 22

What does the sympathetic NS do?

Back 22

Stimulates effectors
Speeds up an activity
Helps us cope with stressful situations by heightening our awareness and preparing for activity
Fight/Flight

Front 23

What does the parasympathetic NS do?

Back 23

Inhibits effectors - slows odwn activity
Controls activities under NORMAL RESTING CONDITIONS
Conserving energy
Replenishing body's reserves
Rest and digest

Front 24

Where is heart rate controlled?

Back 24

Medulla Oblongata - two different sections

Front 25

Decrease in pH -->

Back 25

Increase in HR

Front 26

Increase in pressure -->

Back 26

Decrease in HR

Front 27

Where are chemoreceptors and baroreceptors located?

Back 27

In the aortic arch and caroted arteries.

Front 28

When blood pressure is higher than normal...

Back 28

...baroreceptors transmit nervous impulses to MO area that decreases HR. The centre sends impulses via parasympathetic NS to SAN to decrease HR (and vise versa)

Front 29

Pacinian corpuscles respond to changes in what type of pressure?

Back 29

Mechanical pressure

Front 30

What are two specific features of sensory receptors?

Back 30

They respond to a single type of stimulus

They produce a generator potential by acting as a transducer (A transducer converts information provided by the stimulus into nerve impulses which can be understood by the body)

Front 31

What is a generator potential?

Back 31

All receptors convert the energy of a stimulus into a nervous impulse. This nervous impulse is known as a generator potential.

Front 32

What is the purpose of pacinian corpuscles occurring in joints, ligaments and tendons?

Back 32

They enable the organism to know which joints are changing direction

Front 33

How does a pacinian corpuscle transduce the mechanical energy of a stimulus into a generator potential?

Back 33

The plasma contains stretch-mediated sodium channels. Their permeability to sodium changes when they change shape (e.g. by stretching)

Stretching increases sodium permeability and this leads to a GP and then AP

Front 34

Where are light receptors found?

Back 34

The retina (inner most layer of the eye)

Front 35

Which cells see in black and white?

Back 35

Rod cells

Front 36

Which type of cells are more numerous in the eye?

Back 36

Rod cells (120m/eye)

Front 37

How many sensory neurones: rod cells?

Back 37

1:3 (RETINAL CONVERGENCE)

Front 38

Rod cells can respond to light of a very low/high intensity

Back 38

low - A certain threshold value has to be exceeded before a generator potential is created in the BIPOLAR CELLS - retinal convergence increases the likelihood the threshold value will be exceeded

- Therefore can see at low light intensity but only in black and white

Front 39

What is needed to create a generator potential in rod cells?

Back 39

The pigment in the cells (rhodopsin) needs to be broken down - low intensity light can do this

Front 40

What is the disadvantage of rod cells?

Back 40

They have low visual acuity as 3 rod cells only cause one nerve impulse

Front 41

How many different types of cone cells are there? How are they different?

Back 41

3 - respond to different wavelengths of light

Front 42

How many cone cells are there in each human eye?

Back 42

6m/eye

Front 43

What is the name of the pigment in cone cells and how is it different?

Back 43

Iodopsin - requires a higher intensity for its breakdown

Front 44

Light is focused by the lens on a part of the retina opposite the pupil, this is called...

Back 44

The fovea

Front 45

What is special about the distribution of cells on the fovea?

Back 45

Many more cone cells are found there - on the periphery of the eye only rod cells are found