Chapter 13 ( 5.1.5 Plant and animal responses )

Question 1

13.1

What are the internal (2/4) and external (2/4) type of changes that can occur in the body, two ways animals respond

Answer 1

Internal : blood glucose concentration, cell Ph, internal temperature, water potential
External : external temperature, humidity, new or sudden noises, light intensity
- neurones and hormones

Question 2

13.1

2 reasons why co-ordination is needed in animals

Answer 2

• cells are specialised for a specific function and not many body systems can work isolated, therefore co-ordination is needed for them to work effectively
• To maintain homeostasis = relatively constant internal environment - maintenance of the functions of organs

Question 3

13.1

What is the process of cell signalling and what can cells do through this process

Answer 3

• one cell releases a chemical which has an affect on another cell (target cell)
• 1- transfer signals locally through neurotransmitters
• 2- transfer across large distances through hormones

Question 4

13.2

Definition of neurones and the three different structures within it

Answer 4

Neurone = transmits electrical impulses around the body to respond to stimuli

• Cell body
• Dendrites
• Axons

Question 5

13.2

What does the cell body of neurones contain and why (4)

Answer 5

• contains nucleus surrounded by cytoplasm

- Cytoplasm contains endoplasmic reticulum and mitochondria to produce neurotransmitters

Question 6

13.2

What are the two differences between axons and dendrons and what do dendrons divide into

Answer 6

• dendrons are short whereas axons are long
• dendrons transmit impulses towards the cell body whereas axons transmit impulses away from the cell body
• dendrites

Question 7

13.2

What is the function and structure of sensory neurones, relay neurones and motor neurones

Answer 7

• Sensory neurones :
• function - transmit impulses from the sensory receptor cell to a motor or relay neuron or the brain
• Structure - has one dendron and one axon

Relay neurones :

• function - transmit impulses between neurones e.g sensory and motor
• Structure - many short axons and dendrons

Motor neurones

• function - transmit impulses from sensory or relay neurones to the effector e.g. muscle
• structure - many short dendrites and one long axon

Question 8

13.2

What is the usual pathway of receptors

Answer 8

Receptor cell - sensory neurone - relay neurone - motor neurone - effector

Question 9

13.2

What is the process of myelin sheath being formed and how being an electrical insulator does it speed up the impulse

Answer 9

Process : Schwann cells produce layers of membrane by growing around the axon many times - each time they grow round, a double layer of phospholipid bilayer is laid down

The gap between each Schwann cell is called the node of Ranvier, the electrical impulses ‘jump’ between each gap/node allowing it to travel much faster

Question 10

13.2

What is multiple sclerosis and how does it effect humans

Answer 10

An autoimmune disease where the immune system mistakenly attack body tissue
- thinning or complete loss of myelin sheath and in some cases the whole axon of neurones

Question 11

13.3

Two main features of sensory receptors and definition of transducer

Answer 11

• specific to a single type of stimulus

- act as a transducer - convert mechanical energy into an electrical impulse

Question 12

13.3

What are the four main types of receptors and what do they detect

Answer 12

mechanoreceptor - pressure and movement
chemoreceptor – chemical change
thermoreceptor - heat change
photoreceptor - light change

Question 13

13.3

What does the Pacinian corpuscle detect and where are two places are they located

Answer 13

• mechanical pressure

- skin and joints

Question 14

13.3

Two key parts of pacinian corpuscle structure

Answer 14

• end of the sensory neurone is surrounded by connective tissue
• end of sensory neurone has stretch mediated sodium ion channels which can change shape to allow Na in

Question 15

13.3

The 5 steps of how the pacinian corpuscle converts mechanical pressure into a nerve impulse

Answer 15

1 - at normal = resting potential
2 - when pressure is applied the corpuscle ( connective tissue ) changes shape causing the membrane of the neurone ending to stretch
3 - Na channels now open allowing Na to diffuse in
4 - The membrane is now depolarised resulting in a generator potential
5 - Generator potential causes an action potential

Question 16

13.4

What is the resting potential and what is the potential difference at this state

Answer 16

when a nerve is not transmitting an impulse the outside of the axon is more positively charged than the inside = -70Mv

Question 17

13.4

What does the phospholipid bilayer not allow in the axon so what must the membrane have

Answer 17

doesn’t allow simple diffusion

has gated channel proteins and channel proteins

Question 18

13.4

What 3 events occur to cause and maintain the resting potential ( Na and K ions )

Answer 18

• Na ions are actively transported out the axon whereas potassium is actively transported in through the sodium potassium pump - for every 3 Na 2 K is tranpsorted
• This causes more Na ions outside the membrane than inside and more potassium ions in inside than outside at this stage
• Na channels are gated meaning they stay outside of the axon whereas some K channels stay open allowing ions to diffuse out - this causes more positively charged ions to be outside than inside creating a potential difference of -70Mv

Question 19

13.4

Why are potassium ions pumped in to the axon if they can still diffuse out

Answer 19

• some diffuse out to keep the potential difference at -70Mv
• need potassium ions in the axon to repolarise the axon after the action potential is generated

Question 20

13.4

What are the two steps action potential is triggered

Answer 20

• energy from the stimulus triggers some Na voltage gated channels to open so Na ions diffuse into the axon down the electrochemical gradient making the neurone less negative
• this change in charge causes more Na channels to open so more Na can diffuse in - positive feedback

Question 21

13.4

At +40Mv how does the neurone start to repolarise (2)

Answer 21

Voltage gated Na channels close so no more can diffuse in and voltage gated potassium channels open so k can leave down the electrochemical gradient causing the outside to be more negative than the outside

Question 22

13.4

How does hyperpolarisation occur and then what are the 3 steps that occur the cell so it is fully repolarised

Answer 22

Hyperpolarisation = initally lots of K diffuses out the axon so now the axon is more negative than at its normal resting state

Repolarise :

• Voltage gated K channels close
• Na pumped out by the pump
• K pumped in by the pump

Question 23

13.4
How does Na causing depolarisation at the start of the neurone then cause the next bit of the neurone to depolarise and so on

Answer 23

Na diffuses along the neurone down its concentration gradient as it does this not only does it start to depolarise this part of the neurone but also causes the Na channels on this sections to open causing more Na to diffuse in

Question 24

13.4

What are the 5 steps for the propogation of an action potential

Answer 24

1 - resting potential
2 - stimulus causes first part of the neurone to become depolarised
3 - The next part of the neurone then beomes depolarised nd as this happens potassium gated channles at the start of the neurone open
4 - The neurone continues to become depolarised and as this happens the movement of potassium ions at the start of the neurone cause it to become repolarised
5 - the start of the neurone is now back at resting potential

Question 25

13.4 | What is the refractory period how does this occur and two reasons it occurs

Answer 25

Refractory period = short period after an action potential when the axon can't be excited again - How - Na channels remain shut - why - the action potential doesn't move backwards ( it is unidirectional ) - action potentials don't overlap

Question 26

13.4 | What is saltatory conduction and how is it more energy efficient

Answer 26

= action potentials 'jump' between nodes of ranvier - more energy efficient as less parts of the neurone are being depolarised, therefore less repolarisation is needed which requires ATP for the sodium potassium pump

Question 27

13.4 | What are two other ways that speed up action potential travels

Answer 27

- axon diameter = bigger diameter the quicker transmission as there is less resistance in the cytoplasm - temperature = ions diffuse quicker at higher temperatures however optimum = 40 as proteins become denatured like Na K pump

Question 28

13.4 | What is the all or nothing principle and what do large stimulus' do and not do

Answer 28

The stimulus must hit a certain threshold value to trigger a response - large stimulus does not cause a larger action potential as this is always the same however it does cause more frequent generation of action potentials

Question 29

13.5 | What are six key features of synapses

Answer 29

Synaptic cleft - the gap seperating the two neurones ( usually axon and dendrite ) Presynaptic neurone - the neurone the impulse comes from Postsynaptic neurone - the neurone recieving the impulse Synaptic knob - the swollen end of the presynaptic neurone Synoptic vesicles - contain neurotransmitters, fuse with presynaptic membrane and release them into cleft through exocytosis Neurotransmitter receptors - receptor molecules of neurotransmitters on the postsynaptic membrane

Question 30

13.5 | What does the synaptic knob contain which is key

Answer 30

Mitochondria and endoplasmic reticulum and these are important to make neurotransmitters

Question 31

13.5 | What are the two different types of neurotransmitters in the body and example of each

Answer 31

Excitatory - create action potential in postsynaptic membrane if threshold reached e.g. acetylcholine Inhibitory - result in hyperpolarisation to prevent an action potential being triggered e.g. GABA in the brain

Question 32

13.5 | What is the 8 step simple process of transmitting impulses across synapses

Answer 32

1 - Action potential reaches the end presynaptic neurone 2 - Depolarisation of presynaptic membrane causes Ca ion channels to open 3 - Ca diffuses in to the synaptic knob 4 - Causes synaptic vesicles containing neurotransmitters to fuse with presynaptic membrane and release into cleft through exocytosis 5 - Neurotransmitters diffuse across the cleft and bind with specific receptors on the end of the postsynaptic membrane 6 - This causes Na channels to open 7 - Na ions diffuse in 8 - Action potential created

Question 33

13.5 | How is the neurotransmitter removed from the receptor, where do the products go and 2 reasons this important

Answer 33

- Acetylcholine broken down by enzymes and products return to the synaptic knob - so the stimulus is not maintained - another stimulus can arrive

Question 34

13.5 | What are cholinergic synapses and where do they usually occur

Answer 34

- synapses using acetylcholine | - neuromusuclar junctions = motor neurone to muslce cell (effector)

Question 35

13.5 | What can acetylcholine do and what enzyme breaks it down in the cleft and what are the products

Answer 35

- cause muscles to contract - acetylcholinesterase - choline and ethanoic - go back to presynaptic knob

Question 36

13.5 | What are the three key roles of synapses and how

Answer 36

- make it unidirectional as neurotransmitters are only present on the postsynaptic membrane - impulse on one single neurone can feed multiple differnet neurones - number of simultaneous responses - stimuli from different receptors can produce a single result

Question 37

13.5 | What occurs at some synapses which mean summation must occur

Answer 37

At some synapses not enough neurotransmitters are released to cause an action potential on the postsynaptic neurone

Question 38

13.5 | The two different types of summation

Answer 38

``` Spatial = lots of presynaptic neurones connect to one postsynaptic neurone - build up of neurotransmitters Temporal = lots of action potentials on the same presynaptic neurone over a short period builds up the amount of neurotransmitters ```

Question 39

13.6 - Importante | What are the two systems that the nervous system is structurally organised into

Answer 39

- Central nervous system (CNS) = Brain and spinal cord - Peripheral nervous system = All the neurones that connect the CNS to the rest of the body like sensory neurones from receptors to CNS and motor neurones from CNS to effectors

Question 40

13.6 | What two systems is the nervous system functionally split into

Answer 40

Somatic - under conscious control | Autonomic - under sub-conscious control - something happens automatically without you knowing

Question 41

13.6 | What three places does the autonomic nervous system carry nerve impulses to

Answer 41

- glands, cardiac tissue and smooth muscle

Question 42

13.6 | How is the autonomic nervous system further split

Answer 42

``` Sympathetic = increases activity or something e.g. increased heart rate Parasympathetic = decreases activity or something e.g. decreases heart rate ```

Question 43

13.7 | What are two advantages of having a central control centre ( the brain )

Answer 43

- produces a co-ordinated response | - much faster than if you had control centres all over the body

Question 44

13.7 | What is the function of the cerebrum of the brain and the 5 steps it takes to do this

Answer 44

- responsible for co-ordinating all of the body's voluntary responses (and some involuntary) - receives impulse from sensory neurones into the sensory area within a cerebral hemisphere , interprets it in an association area (regarding previous experience), it then goes to a motor area and then sends it along a motor neurone to an effector cell

Question 45

13.7 | what are the two sides of the cerebrum called and what is the outer layer called, what occurs in this outer layer

Answer 45

- left hemisphere and right hemisphere | - cerebral cortex - most sophisticated area where most of the reasoning and decision making occurs

Question 46

13.7 | What does the size of sensory and motor areas depend on

Answer 46

- the sensory area associated's size depends on the number of receptor cells in the body part - the motor area associated's size depends on how many motor endings there are

Question 47

13.7 | what is the function of the cerebellum

Answer 47

concerned with the co-ordination of muscular movement, body posture and balance - does not initiate movement

Question 48

13.7 | Where are the two places the cerebellum receives information from and where does it relay this information to

Answer 48

- organs of balance in the ears, tone of muscles and tendons - areas of the cerebral cortex that are involved in motor control

Question 49

13.7 | what is the function of the medulla oblongata and 3 examples of the centres

Answer 49

- contains many important regulating centres for the autonomic nervous system - reflex's, heart rate, breathing rate, coughing, swallowing

Question 50

13.7 | What is the function of the hypothalamus and and why is it split into two centres

Answer 50

- main controlling region of the autonomic nervous system | - one centre for the parasympathetic and one for the sympathetic

Question 51

13.7 | What are the 3 main functions of the hypothalamus and why does it have a rich blood supply

Answer 51

- produces hormones - endocrine gland = this is why it is a major control region for autonomic nervous system - controls patter of behaviour e.g. feeding, sleeping and aggression - maintains the composition of the blood plasma like concentration of water and blood glucose = this is why it needs a rich blood supply so it can monitor it

Question 52

13.7 | where is the pituitary gland found and what is its function

Answer 52

- bottom of the hypothalamus and controls most of our glands in the body

Question 53

13.7 | what are the two different sections of the pituitary gland and the function of each

Answer 53

- Anterior pituitary (front section)= produces six hormones e.g. follicle stimulating hormone (FSH) which is a growth hormone - Posterior pituitary (back section) = stores and releases hormones produced by the hypothalamus e.g. ADH which is involved in urine production

Question 54

13.8 | What is a reflex action and why is it essential

Answer 54

- an involuntary response to a sensory stimulus | - provides a faster response preventing or minimising damage to the body

Question 55

13.8 | What is the reflex arc and what are the 4 steps within the process

Answer 55

- the pathway of neurones that provide a reflex action 1) Receptor = detects stimulus and creates an action potential 2) Sensory neurone = carries impulse to the spinal cord 3) Relay neurone = carries impulse from the sensory neurone to a motor neurone within the spinal cord 4) Motor neurone = carries impulse from the spinal cord to the appropriate response (effector)

Question 56

13.8 | What is the spinal cord and how do the neurones interact within the spinal cord

Answer 56

- column of nervous tissues surrounded by the spine for protection - check the revision book

Question 57

13.8 | Why is the knee-jerk reflex considered a spinal reflex

Answer 57

Spinal reflex- is when the impulses doesn't go up to the brain just interacts with the spinal cord

Question 58

13.8 | What is the 4 step process of the knee-jerk reflex

Answer 58

1) leg is tapped just below the patella which stretches the patella tendon - acts as stimulus 2) stimulus initiates reflex arc which causes the extensor muscle on top of the thigh to contract 3) at the same time a relay neurone inhibits the motor neurone of the antagonistic flexor muscle causing it to relax 4) this contraction causes the leg to kick

Question 59

13.8 | What could the absence of the knee-jerk reflex mean and what is the reflex used for

Answer 59

- there could be problems with the patients nervous system | - helps the body maintain posture and balance - can remain balance without much effort

Question 60

13.8 | Why is the blinking reflex regarded as a cranial reflex and what is its purpose

Answer 60

- because the reflex arc occurs in the brain and not the spinal cord - to protect the cornea from foreign bodies e.g. dust and flying insects

Question 61

13.8 | What are 3 reasons the blinking reflex occurs

Answer 61

- when the cornea is stimulated - sounds greater than 40-60 dB - over-bright light - to protect the lens and retina

Question 62

13.8 | what is the 4 step process of the blinking reflex, what is a consensual response ?

Answer 62

1) when the the cornea is irritated the stimulus triggers an impulse along a sensory neurone ( fifth cranial nerve ) 2) impulse passes through a relay neurone in the lower brain stem 3) impulse sent along branches of motor neurone (seventh cranial nerve) to initiate a motor response close to the eyelids 4) this initiates a consensual response = both eyes are closed in response to a stimulus

Question 63

13.8 | why can doctors use the blinking reflex to determine if an unconscious patient is brain dead

Answer 63

as the blinking reflex uses the lower brain stem so if it is not present then the patient is brain dead

Question 64

13.8 | What are four ways reflexes increase your chance of survival

Answer 64

1- they are involuntary = prevents the brain from being overloaded as it does not use the decision making region of the brain 2- don't have to be learnt = provides immediate protection as it is present from birth 3- they are extremely fast = reduces the chance of damage ( only uses one or two synapses ) 4- they are everyday actions = for example they keep us up right and aid with digestion

Question 65

13.9 | What are the three different types of muscle

Answer 65

- skeletal muscles = muscle cells responsible for movement - Cardiac muscle = muscle found in the heart, myogenic - can contract without the need for nervous impulse - Smooth muscle = found in vessel walls, bladder, stomach etc.

Question 66

13.9 | What is the difference in arrangements and contractions between skeletal, cardiac and smooth muscle1

Answer 66

skeletal - A = regular so muscle contracts in one direction C = rapid, short Cardiac - A = cells branch can interconnect resulting in a simultaneous contraction C = intermediate, intermediate Smooth - A = no regular arrangement as different cells can contract in different directions C = slow, can remain contracted for a while

Question 67

13.9 | What is the name of the plasma membrane enclosing the muscle fibres

Answer 67

- sarcolemma

Question 68

13.9 | Why are muscle fibres longer than normal cells and why is this important

Answer 68

- formed by embryonic muscle cells fusing together | - makes the muscle stronger as the junction between adjacent cells would have been a point of weakness