5.1 Neuronal communication & sensory receptors

Question 1

what must all organisms do?

Answer 1

respond to changes in their internal and external environment

Question 2

how do animals respond to their environment?

Answer 2

neuronal and hormonal

Question 3

how do plants respond to their environment?

Answer 3

chemical communication including hormones e.g. auxin

Question 4

what factors do we respond to in our environment?

Answer 4

humidity
temperature
sound
light intensity
blood glucose levels
internal temperature
cell PH
water potential

Question 5

why is coordination needed?

Answer 5

few body systems can work in isolation

all cells have specialised functions so must coordinate the function of different cells and systems efficiently

Question 6

(Coordination) give an example of body systems needing to work together? (animals)

Answer 6

muscles contract and need O2
O2 transported in RBCs
RBCs made in bone marrow my haematopoietic stem cells

Question 7

(coordination) give an example of plant cells needing to coordinate? and how they do it?

Answer 7

flowering plants need to coordinate with the seasons to know when to flower, light sensitive chemicals enable this to happen

Question 8

(Homeostasis) in multicellular animals different organs have different functions….

Answer 8

….so must be coordinated

Question 9

(Homeostasis) give examples of a system in which organs must work together:

Answer 9

digestive organs must work together to maintain blood glucose levels

Question 10

what does nervous and hormonal control rely upon?

Answer 10

communication at cellular level through cell signalling

Question 11

where can cells transfer signals?

Answer 11

locally - between neurones at synapses

over large distances using hormones

Question 12

what is AUTOCRINE cell signalling?

Answer 12

where the call targets itself

Question 13

what is PARACRINE cell signalling?

Answer 13

where cell targets nearby cell

Question 14

what is ENDOCRINE cell signalling?

Answer 14

where the cell targets a distant cell through the bloodstream

Question 15

What does cell signalling across gap junctions involve?

Answer 15

a cell targeting another cell which it is connected by gap junctions

Question 16

what is the nervous system responsible for?

Answer 16

detecting changes in the internal and external environment

Question 17

what is the pathway a nerve impulse follows?

Answer 17

receptor -> sensory neurone -> relay neurone -> motor neurone-> effector

Question 18

what are some axons covered in?

Answer 18

a myelin sheath (many layers of plasma membrane)

Question 19

what sort of cells produce the myelin sheath? how do they do it?

Answer 19

schwann cells

by growing around the axon many times adding a double layer of phospholipid bilayer each time

Question 20

what is the function of the myelin sheath?

Answer 20

insulation which leads to conducting electrical impulses at faster speeds

Question 21

what is the function of a motor neurone?

Answer 21

transmitting electrical impulses from the relay neurone (in the CNS) to the effector producing a response

Question 22

what is the function of a sensory neurone?

Answer 22

transmitting the electrical impulse from receptor cells to a relay neurone, motor neurone or the brain

Question 23

what is the function of the axon?

Answer 23

to carry nerve impulses away from the cell body

Question 24

what is multiple sclerosis?

Answer 24

autoimmune disease which affects nerves in the brain and spinal chord

Question 25

what does multiple sclerosis involve and what does it result in?

Answer 25

thinning of myelin sheath and axon, slow impulses, results in problems with muscle movement and vision

Question 26

what are sensory receptors?

Answer 26

groups of specialised cells located in sense organs such as the eyes and ears

Question 27

what do sensory receptors do?

Answer 27

convert the stimulus they detect into nerve impulses called a GENERATOR POTENTIAL which is transmitted to the CNS

Question 28

what are the two main features of sensory receptors?

Answer 28

specific to a single type of stimulus

acts as a transducer converting a stimulus to a nerve impulse

Question 29

what are the 4 types of sensory receptors?

Answer 29

photoreceptors
chemoreceptors
mechanoreceptors
thermoreceptors

Question 30

what stimulus does a mechanoreceptor detect? give an example of a mechanoreceptor and the sense organ:

Answer 30

pressure and movement
pacinian corpuscle (detects pressure)
organ: skin

Question 31

what stimulus does a chemoreceptor detect? give an example of a chemoreceptor and the sense organ:

Answer 31

chemicals
olfactory receptor (detects smells)
organ: nose

Question 32

what stimulus does a thermoreceptor detect? give an example of a thermoreceptor and sense organ:

Answer 32

heat
end bulbs of Krause
tounge

Question 33

what stimulus does a photoreceptor detect? give an example of a photoreceptor and sense organ:

Answer 33

light
cone cell (detects different wavelengths of light)
eye

Question 34

what are pacinian corpuscle’s?

Answer 34

sensory receptors that detect mechanical pressure

Question 35

where are pacinian corpuscle’s located?

Answer 35

in the joints and deep within skin

Question 36

what does the centre of the pacinian corpuscle contain?

Answer 36

the end of the sensory neurone surrounded by layers of connective tissue with each layer being separated by gel

Question 37

the neurone ending in a pacinian corpuscle has a…

Answer 37

…stretch mediated sodium ion channel

Question 38

1. In resting state the stretch mediated sodium ion channels in the sensory neurones membrane are too narrow to?

Answer 38

allow sodium ions to pass through - it has resting potential

Question 39

2. when pressure is applied to the pacinian corpuscle what does it do?

Answer 39

it changes shape causing the membrane to stretch

Question 40

3. When the membrane stretches what happens to the sodium ion channels?

Answer 40

sodium ion channels widen and sodium can diffuse into the neurone

Question 41

4. what does the influx of positive ions do to the membrane?

Answer 41

changes the potential of the membrane, it becomes depolarised resulting in a generator potential

Question 42

5. what does the generator create?

Answer 42

an action potential that passes along the sensory neurone to the CNS

Question 43

what do rod cells allow? what is this due to?

Answer 43

vision in dim light

due to the presence of a pigment called RHODOPSIN found in membrane bound vesicles

Question 44

what happens to rhodopsin when it absorbs light?

Answer 44

Bleaching - it is split into opsin and retinal.

Low levels of light are enough to cause this breakdown

Question 45

what effect does opsin have on the rod cells permeability to sodium?

Answer 45

changes its permeability to sodium, initiating a generator potential

Question 46

what are cone cells sensitive to? what is this due to?

Answer 46

high light intensities

due to the presence of the pigment IODOPSIN

Question 47

what happens to iodopsin in bright light?

Answer 47

broken down into its constituent parts, generating an action potential in the ganglion cell

Question 48

what does the cell body consist of?

Answer 48

nucleus surrounded by the cytoplasm, which contains large amounts of ER & mitochondria involved in the production of neurotransmitters

Question 49

what are dendrons?

Answer 49

short extensions from the cell body which divide into dendrites. They transmit electrical impulses toward the cell body.