5.1 Communication

Question 1

How do animals respond to changes in the environment ?

Answer 1

They response through electrical responses through neurones and chemical responses through hormones.

Question 2

How do plants respond to changes in the environment ?

Answer 2

Plants do not have a nervous system so only respond to changes through chemical responses via hormones.

Question 3

Why do cells within a multicellular organism need to coordinate ?

Answer 3

They need to coordinate the function of different cells to operate effectively.

Question 4

What is homeostasis ?

Answer 4

Coordination of organs in order to maintain a relatively constant internal environment. Eg. the digestive organs all work together to maintain a constant blood glucose concentration.

Question 5

What is cell signalling ?

Answer 5

Communication at a cellular level. Occurs through one cell releasing a chemical which has an effect on another cell. They can transfer signals locally or across large distances.

Question 6

What is the nervous system responsible for ?

Answer 6

The nervous system is responsible for detecting changes in the external and internal environment in order for a response to occur.

Question 7

What is a stimulus ?

Answer 7

Change in the environment resulting in a response.

Question 8

What are neurones ?

Answer 8

Specialised nerve cells that transmit electrical implulses rapidly around the body so the organism can respond to changes in the environment.

Question 9

What is the structure of cell body of a neurone ?

Answer 9

Contains the nucleus surrounded by cytoplasm. In cytoplasm there is endoplasmic reticulum and mitochondria, involved in the production of neurotransmitters.

Question 10

What is the structure of dendrons in a neurone ?

Answer 10

Short extensions from the cell body. They divide into smaller branches known as dendrites. They are responsible for transmitting impulses toward the cell body.

Question 11

What is the structure of axons in a neurone ?

Answer 11

Singular, elongated nerve fibres that transmit impulses away from the cell body. The fibres can be very long and are cylindrical with a narrow region of cytoplasm with a plasma membrane.

Question 12

What are sensory neurones ?

Answer 12

They transmit impulses from a sensory receptor cell to a relay or motor neurone or the brain. They have one dendron, which carries the impulse to the cell body and one axon, which carries impulse away from the cell body.

Question 13

What are relay neurones ?

Answer 13

They transmit impulses between neurones. They have many short axons and dendrons.

Question 14

What are motor neurones ?

Answer 14

Transmit impulses from a relay neurones or sensory neurone to an effector, such as a muscle or gland. They have one long axon and short dendrites.

Question 15

What is the electrical impulse pathway ?

Answer 15

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

Question 16

What is the myelin sheath ?

Answer 16

Many layers of plasma membrane that cover some neurones. It acts as an insulating layer and allows myelinated neurones to conduct the electrical impulse at a much faster speed than unmyelinated neurones.

Question 17

What are Schwann cells ?

Answer 17

They produce layers of plasma membrane around an axon, this is called the myelin sheath. They are a type of glia cell.

Question 18

What is saltatory conduction ?

Answer 18

When signal jumps from node to node, increasing speed of transmission by reducing distance travelled of electrical impulse.

Question 19

What is multiple sclerosis ?

Answer 19

Autoimmune disease, where myelin is recognised as foreign so is broken down, reducing speed of transmission affecting mobility.

Question 20

What is the Node of Ranvier ?

Answer 20

Gap between myelin sheath, where impulse jumps between to reduce distance and therefore increasing speed of transmission.

Question 21

What is the stimulus for photoreceptors and what is a specific type ?

Answer 21

They respond to light and some are cone cells in the eye.

Question 22

What is the stimulus for chemoreceptors and what is a specific type ?

Answer 22

They respond to chemicals and some are olfactory receptors found in ther nose.

Question 23

What is the stimulus for thermoreceptors and what is a specific type ?

Answer 23

They respond to heat and some are End-bulb Krause cells found in the tongue.

Question 24

What is the stimulus for mechanoreceptors and what is a specific type ?

Answer 24

They respond to pressure and movement and some are Pacinian corpuscle.

Question 25

What are sensory receptors ?

Answer 25

Allow the body to detect changes in the environment and are often located in sense organs.

Question 26

Are receptors specific ?

Answer 26

Yes receptors are specific to only one type of stimulus and act as transducers.

Question 27

What are transducers ?

Answer 27

They convert stimulus into a nerve impulse, called a generator potential into an action potential.

Question 28

What are pacinian corpuscle receptors ?

Answer 28

They are a type of receptor that responds to mechanical pressure. They are located deep within the skin and are most abundant in fingertips and sides of feet. Acts as a transducer.

Question 29

What is the resting membrane potential of pacinian corpuscle receptors ?

Answer 29

-70 mV

Question 30

What occurs to pacinian corpuscle when pressure is applied ?

Answer 30

Stretch-mediated sodium channels open causing Na+ ions to enter the receptor, causing depolarisation. This increases the voltage charge from -70mV and this initiates the generator potential.

Question 31

What does the generator potential trigger ?

Answer 31

Triggers the action potential.

Question 32

What is the resting membrane potential ?

Answer 32

Resting membrane potential is when the outside of the membrane is more positively charged than the inside, so it is polarised. It is normally around -70mV.

Question 33

What does the sodium-potassium pump do in membrane of axon?

Answer 33

It actively pumps sodium ions out of the axon and potassium ions into the axon. For every 3Na + pumped out, 2K+ are pumped in.

Question 34

What does sodium-potassium pump in membrane set up ?

Answer 34

Sets up the electrochemical gradient for sodium ions to diffuse back into the axon, and potassium ions back out.

Question 35

What happens to channels when electrochemical gradient is set up ?

Answer 35

Potassium channels are now open to allow K+ ions to diffuse out of the axon. Most gated sodium channels are closed preventing the sodium ions from diffusing back into the axon.

Question 36

How does the opening and closing of channels in axon membrane cause a resting potential of -70mV ?

Answer 36

Causes there to be more positively charged ions outside of the axon creating a resting potential of -70mV ?

Question 37

What happens when a stimulus is detected by a sensory receptor ?

Answer 37

The energy of the stimulus temporarily reverses the charges on the axon membrane.

Question 38

What happens when action potential has become depolarised ?

Answer 38

The potential difference across the membrane is approximately +40 mV so has become depolarised.

Question 39

What happens when repolarisation of axon occurs ?

Answer 39

When the impulse passes, repolarisation occurs, when potential changes from + to -, and the neurone returns to its resting potential.

Question 40

When does action potential occur ?

Answer 40

An action potential occurs when protein channels in the axon membrane change shape as a result of the change of voltage across its membrane.

Question 41

What is propagation of action potential ?

Answer 41

Action potentials start at one end of the neurone and are propagated along the axon to the other end.

Question 42

How does axon become propagated along the neurone ?

Answer 42

The polarisation of one region of the neurone acts as a stimulus for the depolarisation of the next region.

Question 43

What is the refractory period ?

Answer 43

After an action potential there is a short period of time when the axon cannot be excited again as the voltage gate sodium channels remain closed.

Question 44

Why is the refractory period needed ?

Answer 44

To ensure the action potential remains unidirectional as it cannot go back along the axon or to prevent it from overlapping.

Question 45

What are 3 factors that speed up the action potential ?

Answer 45

Myelination, diameter of axon and temperature.

Question 46

Why are nerve impulses described as all or nothing ?

Answer 46

This is because there is a threshold value that must be reached for a response to be triggered. No matter the stimulus, the same size action potential will be triggered.

Question 47

What is a synapse ?

Answer 47

Junction between 2 neurones (or a neurone and an effector).
Ensures impulses are unidirectional and allows impulse from a neurone (or multiple neurones) to many neurones/ or one neurone.

Question 48

What occurs when action potential goes along pre-synaptic neurone ?

Answer 48

Causes voltage gated calcium channels to open, leading to an influx of Ca2+ diffusing down the electrochemical gradient causing vesicles to fuse to the plasma membrane of the pre synaptic neurone.

Question 49

What occurs when synaptic vesicles fuse to the plasma membrane of pre-synaptic neurone ?

Answer 49

This causes neurotransmitters to diffuse across the synaptic cleft and fuse to the receptors causing voltage gated sodium channels causing them to open. This causes an influx of charge so the post-synaptic neurone is depolarised and causes a new action potential.

Question 50

What occurs when the neurotransmitter has opened the voltage gates sodium channels ?

Answer 50

Enzymes, such as Acetylcholinesterase breaks down the neurotransmitters into acetyl and choline. These then diffuse down the concentration gradient, where ATP is used to reform bonds between back into the pre-synaptic neurones to be recycled.

Question 51

What are excitatory neurotransmitters ?

Answer 51

They are neurotransmitters resulting in depolarisation of post synaptic neurone. If threshold is reached, an action potential is triggered.

Question 52

What are inhibitory neurotransmitters ?

Answer 52

They are neurotransmitters that result in the hyper polarisation of post synaptic neurone. Prevents the action potential from being triggered.

Question 53

What is spatial summation ?

Answer 53

When more than 1 pre-synaptic neurone is required for the threshold to be reached.

Question 54

What is temporal summation ?

Answer 54

Constant firing of neurotransmitters in the pre-synaptic neurone until the threshold has been reached.

Question 55

What does the central nervous system contain ?

Answer 55

Contains the brain and the spinal cord.

Question 56

What does the peripheral nervous system contain ?

Answer 56

Has most of the sensory and motor neurones, as well as the pacinian corpuscle.

Question 57

What is somatic nervous system responsible for ?

Answer 57

Responsible for conscious control. Eg., movement and speech.

Question 58

What is the autonomic nervous stem responsible for ?

Answer 58

Responsible for the subconscious control as it frees up higher thinking. Eg., breathing, heart rate, blinking, digestion.

Question 59

What does the sympathetic nervous system responsible for ?

Answer 59

‘Flight for fight’ and is controlled by the neurotransmitter, noradrenaline.

Question 60

What is the parasympathetic nervous system responsible for ?

Answer 60

Responsible for relaxing responses and is controlled by the neurotransmitter, acetylcholine.

Question 61

What is the cerebrum responsible for ?

Answer 61

Controls voluntary actions. Is highly convoluted, which increases SA.

Question 62

What lobes are in the cerebrum and what are they responsible for ?

Answer 62

-Frontal lobe = problem solving, decision making, language
-Parietal lobe = sensory information
-Temporal lobe = listening, speech, communication.
-Occipital lobe = Vision

Question 63

What is the cerebellum responsible for ?

Answer 63

Controls muscular movement, posture and balance. It does not initiate movement but coordinates it. Receives information from ears about balance and tone of muscles and tendons.

Question 64

What is the medulla oblongata responsible for ?

Answer 64

Part of the brain stems that control reflex activities such as heart and breathing rate. Important in autonomic nervous system, controlling swallowing and coughing.

Question 65

What is the hypothalamus responsible for ?

Answer 65

Controls and regulates release of hormones in the pituitary gland. Regulates homeostasis, hunger, etc.

Question 66

What is the anterior pituitary gland responsible for ?

Answer 66

Produces and release of hormones that regulate many bodily functions.

Question 67

What is the posterior pituitary gland responsible for ?

Answer 67

Stores and releases hormone that regulates many bodily functions.

Question 68

What is a reflex ?

Answer 68

Involuntary response to a sensory stimulus.

Question 69

What is the blinking reflex ?

Answer 69

Involuntary reflex of the eyelids when cornea is stimulated. It is a cranial reflex so occurs in the brains stem not the spinal cord.

Question 70

What is the trigeminal nerve in the blinking reflex ?

Answer 70

Sensory neurone that synapses with the cornea receptor and motor neurone.

Question 71

What is the knee jerk reflex ?

Answer 71

Spinal reflex so only goes to the spinal cord and is commonly tested by doctors to check reflex of the knee.

Question 72

How does a knee reflex occur ?

Answer 72

When knee is tapped below the kneecap it stretches the patellar tendon and acts as a stimulus, which initiates the reflex arc. This causes the extensor muscle to contract.

Question 73

What occurs at same time as contraction of extensor muscle in a knee reflex ?

Answer 73

Relay neurone inhibits a motor neurone of the flexor muscle, causing it to relax. This contraction, coordinated with the antagonistic flexor hamstring muscle, causes the leg to kick.

Question 74

What are skeletal muscles ?

Answer 74

Make up bulk of body muscle tissue and are responsible for movement. They are striated in appearance and are a regular arrangement of muscle cells so contracts in one direction.

Question 75

What are cardiac muscles ?

Answer 75

Found only in the heart. Myogenic, so contract without need for nervous stimulus, causing heart to beat regularly. They are also specialised striated arrangement. Fibres are branched and uninucleated.

Question 76

What are smooth muscles ?

Answer 76

Found in many parts of the body and are non-striated. They are involuntary muscles and can remain contracted for a relatively long time. Fibres are spindle shaped and uninucleated.

Question 77

What is the sarcolemma ?

Answer 77

Specialised plasma membrane for muscle fibres in skeletal muscles.

Question 78

What is the sarcoplasmic reticulum ?

Answer 78

Specialised version of the ER that generated Ca2+ ions.

Question 79

What are T tubules ?

Answer 79

Extend inward when there is Ca2+, so all myofibrils depolarise at the same time.

Question 80

What are myofibrils ?

Answer 80

Cylindrical organelles made of protein and are specialised for contraction. They are thicker than actin filaments.

Question 81

What is the sarcomere ?

Answer 81

Functional region of myofibril. When muscle contracts, sarcomere contracts. Has dark band (actin and myosin), light band (actin only) and the H zone (myosin only).

Question 82

What is tropomyosin ?

Answer 82

Covers the binding sites on actin filaments in resting states.

Question 83

What is troponin ?

Answer 83

Holds tropomyosin in place.