Chapter 13

Question 1

What is the need for communication and coordination

Answer 1

To increase chances of survival by responding to external conditions and to ensure optimal conditions for metabolism by responding to changes in internal environment

Question 2

What is cell signalling

Answer 2

Cell signalling is cells releasing chemicals which have an effect on target cell to communicate can be either
Locally EG neurones and synapses
Or across large distances EG hormones

Question 3

What are sensory neurones and draw a diagram

Answer 3

Sensory neurones transport impulses from sensory receptors to the central nervous system

Should include dendrites myelin sheath around the dendron axon cell body and axon terminal

Question 4

What are relay neurones and draw a diagram

Answer 4

Relay neurones transmit impulses between sensory and motor neurones
Should include axon terminal cell body axon and dendron and dendrites

Question 5

What is a motor neurone and diagram

Answer 5

Motor neurones transmit impulses from the central nervous system to an effector
Should include and write cell body note around the apps on my own sheath and axon terminal

Question 6

How does the myelin sheath work

Answer 6

Made of schwann cells the myelin sheath accident insulator which speeds are electrical impulse conduction this is because between the schwann cells there is a gap called the node of ranvier causing the impulses to jump from one node to the next which speed it up

Question 7

What are the two main factors of sensory receptors

Answer 7

They are specific to one type of stimulus

They act as transducers they convert energy from one form to another

Question 8

The four different types of sensory receptors

Answer 8

Mechanoreceptors- pressure and movement
Chemoreceptors- chemicals
Thermoreceptors- temperature
Photoreceptors- light

Question 9

Explain how the pancinian corpuscle works

Answer 9

1) at resting potential the stretch mediated sodium Ion channels are too narrow to allow them through
2) when pressure is applied the membrane changes shape causing the channels to widen and Sodium ions to diffuse in
3) this depolarise is it creating a generator potential
4) this creates an action potential which is a nerve impulse

Question 10

What is resting potential

Answer 10

Resting potential is the difference in charge between the inside and outside of an axon when the neurone is not transmitting an impulse

Question 11

How is a resting potential generated

Answer 11

1) sodium potassium pump actively transport three sodium ions out of every 2 potassium ions in
2) most gated sodium Ion channels are closed so sodium ions cannot diffuse back into the axon down its electrochemical gradient
3) most potassium ion channels are open allowing the potassium ions to diffuse back in
4) there are more positive ions outside the axon creating a resting potential

Question 12

How is an action potential generated

Answer 12

1) the neurone is at resting potential
2) the energy of a stimulus triggers some sodium voltage gated ion channels to open so sodium ions diffuse into the neurone down the electrochemical gradient
3) depolarisation- the potential difference threshold is reached so more sodium Ion channels open allowing more sodium ions in which is an example of positive feedback
4) repolarization at a potential difference of 40 sodium Ion channels clothes and voltage-gated potassium ion channels open so potassium ions diffuse out down their electrochemical gradient
5) hyper polarisation the potential difference becomes more negative than the resting potential due to potassium ion channels slowly closing
6) the sodium potassium pump returns the membrane to resting potential

Question 13

How is an action potential transmitted

Answer 13

1) during an action potential Some sodium ions that diffuse in during depolarization diffuse sideways down a concentration gradient
2) this triggers depolarization in the next region and so on known as the wave of depolarization
3) the previous region undergoes a refractory period to return to resting potential

Question 14

What is saltatory conduction

Answer 14

Myelinated neurons are faster as depolarization can only occur at the nodes of ranvier and this makes the action potential jump from one node known as saltatory conduction

Question 15

What is the all or nothing principle

Answer 15

The all-or-nothing principle states that if the threshold is reached and action potential of the same size will be triggered a bigger stimulus won’t cause a bigger action potential but it will cause more frequent action potentials

Question 16

What is a synapse

Answer 16

A synapse is the junction between two neurones or a neurone and an effector

Question 17

What is a neurotransmitter

Answer 17

A neurotransmitter is a chemical involved in communication across a synapse there are two types

Excitatory neurotransmitters result in the depolarisation of postsynaptic neurons

Inhibitory neurotransmitters result in the hyper polarisation of the postsynaptic membrane

Question 18

Explain the process of passing an action potential across a synapse at a cholinergic synapse

Answer 18

1) an action potential arrives at the end of the presynaptic neuron depolarising it and causing the calcium ion channels to open and calcium ions to enter
2) calcium ions influx causing synoptic vesicles to fuse with the presynaptic membrane and release the acetylcholine neurotransmitters into the synoptic cleft
3) acetylcholine diffuse across and fuse of receptors on the postsynaptic membrane causing sodium Ion channels to open
4) the influx of sodium Ions generate a new action potential
5) acetylcholine esterase hydrolyses the acetylcholine into choline and ethanoic acid which diffuses back into the presynaptic neurone preventing it from continually generating a new action potential
6) acetylcholine is recombined and stored in vesicles in the presynaptic neuron and the sodium Ion channels close

Question 19

What is spatial summation

Answer 19

Spatial summation is when neurones converge so as the small amount of neurotransmitter from each can be enough to reach the threshold and trigger an action potential

Question 20

What is temporal summation

Answer 20

Temporal summation is where two or more nerve impulses arrive in quick succession at the same presynaptic neurone building up neurotransmitters in the synoptic cleft increasing the likelihood of action potential

Question 21

What is a reflex

Answer 21

Reflex is an involuntary response to a sensory stimulus

Question 22

Draw the reflex arc

Answer 22

Receptor sensory neuron relay neuron motor neurone

Question 23

Explain the process of the blinking reflex

Answer 23

1) the cornea is irritated by foreign body
2) is triggers an impulse on a sensory neurone
3) this passes through a relay neurone to the central nervous system
4) a response is sent along the motor neurone to a muscle in the eyelid
5) the eyelid shuts

Question 24

Explain the process of the knee jerk reflex

Answer 24

1) the leg is taps just below knee cap
2) the patellar tendon detect the muscle being stretched and sends a nerve impulse on a sensory neurone
3) a motor neurone carries the impulse to the effector
4) this causes the extensor muscle to contract and a relay neuron inhabits the motor neurone of the flexor muscle causing it to relax which causes the kick

Question 25

Draw the organisation of the mammalian nervous system

Answer 25

Mammalian nervous system

CNS (brain and spinal cord) & PNS (sensory and motor neurones)

Somatic (conscious) and autonomic (unconcious)

Sympathetic (noradrenaline fight or flight) and parasympathetic (acetylcholine rest and digest)

Question 26

Draw a diagram of the brain

Answer 26

Should include
Cerebrum vision hearing learning thinking
Cerebellum coordinates muscles balance and posture
Medulla oblongata controls breathing and heart rate
Pituitary gland controls body glands
Hypothalamus maintains body temperature

Question 27

Describe skeletal muscle and draw diagram

Answer 27

Skeletal muscle is 
striated 
has conscious control 
has a regular arrangement (so contracts in one direction)
Responsible for movement 
and short rapid contractions

Question 28

Describe cardiac muscle and draw a diagram

Answer 28

Specialised striated
in voluntary control
irregular branch arrangement (for simultaneous contraction)
Intermediate contractions

Question 29

Describe involuntary muscle and draw a diagram

Answer 29

Non-striated
involuntary control
no regular arrangement (for multi directional contractions)
slow long contractions

Question 30

Draw diagram of a sarcomere

Answer 30

Shoukd include H zone myosin sarcomere light band acting and z line

Question 31

What is the sliding filament theory

Answer 31

During contraction the myosin filaments pull the actin towards the centre of the sarcomere

Question 32

Describe the structure of myosin

Answer 32

Myosin have globular heads with a binding site for actin and ATP

Question 33

Describe the structure of actin

Answer 33

Acting have binding sites for myosin heads but they are blocked by trypomyosin and held in place by Tryponin

Question 34

Describe the process of muscle contraction

Answer 34

1) an action potential from a motor neurone stimulates a muscle cell and depolarizes the sarcolemma
2) this spreads down the t-tubules to the sarcoplasmic reticulum
3) this causes it to release calcium ion into the sarcoplasm
4) calcium ions bind to troponin causing it to change shape pulling the trypo myosin out of the actin myosin binding site
5) this releases ADP so an ATP molecule can bind and provide energy to detach the myosin head
6) calcium ions activate atpase which hydrolyzes ATP to ADP and the head returns to its original position binded by ADP