Module 5 - Communication, Homeostasis and Energy

Question 1

what is homeostasis?

Answer 1

the maintaining of a relatively constant internal environment

Question 2

what is cell signalling?

Answer 2

communication at a cellular level

Question 3

what is cell signalling used for?

Answer 3

transferring local signals e.g. between neurones and synapses
transferring signals across large distances using hormones

Question 4

what is the role of neurones?

Answer 4

transmit electrical impulses rapidly so we can respond to stimuli internally and externally

Question 5

what is the structure of a neurone?

Answer 5

cell body. dendrons, dendrites, axon

Question 6

what are the 3 main types of neurone?

Answer 6

sensory, relay, motor

Question 7

what is the structure of a sensory neurone?

Answer 7

one dendron, cell body in centre of axon

Question 8

what is the structure of a relay neurone?

Answer 8

many short axons and dendrons, cell body at the start of the neurone (along with dendrites)

Question 9

what is the structure of a motor neurone?

Answer 9

long axon, many short dendrites with cell body

Question 10

what pathway does an electrical impulse follow?

Answer 10

receptor –> sensory neurone –> relay neurone –> motor neurone –> effector

Question 11

what do Shwannn cells do?

Answer 11

produce layers of plasma membrane by growing around the axon multiple times to create a myelin sheath

Question 12

what does MS stand for?

Answer 12

multiple sclerosis

Question 13

what is MS?

Answer 13

an autoimmune disease that attacks the myelin sheath of neurones

Question 14

why does a myelin sheath increase speed of transmission?

Answer 14

allows the electrical impulse to jump between the nodes of Ranvier, insulates the axon

Question 15

name 2 features of sensory receptors:

Answer 15

they are specific to a single type of stimulus

they act as transducers

Question 16

name 4 types of sensory receptor:

Answer 16

mechanoreceptor, chemoreceptor, thermoreceptor, photoreceptor

Question 17

what is the stimulus for a mechanoreceptor?

Answer 17

pressure and movement

Question 18

name an example of a mechanoreceptor:

Answer 18

Pacinian corpuscle

Question 19

name the sense organ for mechanoreceptors:

Answer 19

skin

Question 20

what is the stimulus for a chemoreceptor?

Answer 20

chemicals

Question 21

name an example of a chemoreceptor:

Answer 21

olfactory receptor

Question 22

name the sense organ for chemoreceptors:

Answer 22

nose

Question 23

what is the stimulus for a thermoreceptor?

Answer 23

heat

Question 24

name an example of a thermoreceptor:

Answer 24

end-bulbs of Krause

Question 25

name the sense organ for thermoreceptors:

Answer 25

tongue

Question 26

what is the stimulus for photoreceptors?

Answer 26

light/light wavelengths

Question 27

name an example of a photoreceptor:

Answer 27

cone cells

Question 28

name the sense organ for photoreceptors:

Answer 28

eyes

Question 29

what is the role of a transducer?

Answer 29

creating a generator potential by converting a stimulus into a nervous impulse

Question 30

where are Pacinian corpuscles found?

Answer 30

deep within your skin, fingers, soles of feet, joints

Question 31

how does a Pacinian corpuscle convert mechanical pressure into a nervous impulse?

Answer 31

1. resting potential - stretch mediated Na+ channels are normal/narrow 2. when pressure is applied, shape changes and membrane stretches 3. when membrane stretches, Na+ channels open and Na+ ion diffuse into the neurone 4. influx of Na+ changes membrane potential - becomes depolarised. results in generator potential 5. generator potential creates action potential

Question 32

what is resting potential?

Answer 32

a neurone is not transmitting an impulse

Question 33

What is the membrane potential for resting potential?

Answer 33

about -70mV (outside membrane is more positively charged than the inside of the axon)

Question 34

what is threshold potential?

Answer 34

a certain mV the stimulus has to reach so that an action potential can be triggered

Question 35

what is the membrane potential for threshold potential?

Answer 35

about -60mV

Question 36

what is depolarisation?

Answer 36

energy of a stimulus temporarily reverses charges on axon membrane

Question 37

what is action potential?

Answer 37

this is when a response happens towards a stimulus

Question 38

what is the membrane potential for action potential?

Answer 38

+40mV

Question 39

what is repolarisation?

Answer 39

K+ ions diffuse out of the axon. axon becomes more negative inside than outside

Question 40

what is hyperpolarisation?

Answer 40

a dip in negativity due to an influx of K+ ions leaving the axon

Question 41

what 2 stages are part of the refractory period?

Answer 41

repolarisation, hyperpolarisation

Question 42

how does an action potential occur?

Answer 42

1. neurone is at resting potential. 2. stimulus triggers sodium voltage-gated channels to open, membrane more permeable to Na+ ions. Na+ ions diffuse inside the axon, inside of neurone less negative. 3. depolarisation causes more Na+ ion channels to open (positive feedback) 4. action potential occurs at +40mV. Voltage-gated Na+ ion channels close, voltage-gated K+ ion channels open 5. K+ ions diffuse out the axon. Reduces charge, inside of axon more negative than the outside. 6. Hyperpolarisation - influx of K+ ions leaving the neurone. Voltage-gated K+ ion channels close. 7. sodium-potassium pumps restore membrane potential and axon returns to resting potential.

Question 43

what is the all-or-nothing principle?

Answer 43

if threshold potential is reached, a response will be triggered. no matter how large the stimulus is, the same sized action potential will be triggered

Question 44

what is spatial summation?

Answer 44

a number of presynaptic neurones connect to one postsynaptic neurone

Question 45

what is temporal summation?

Answer 45

a single presynaptic neurone releases a neurotransmitter as a result of an action potential several times over a short period