Ch 13, communication

Question 1

Need for Coordination/Communication

Answer 1

Organisms must coordinate actions of different cells/organs to operate effectively.

Question 2

Example of Plant need for Coordination

Answer 2

Flowering must coordinate with seasons.
Light-sensitive chemicals enable plants to coordinate the development of flower buds with lengthening days that signal the approach of summer.

Question 3

Example of Animal need for Coordination

Answer 3

Muscles need energy to contract, so must constantly respire. Respiration requires oxygen, so cells must be consantly supplied with oxygen - depend on red blood cells (erythrocytes) for this.

Question 4

Define Homeostasis

Answer 4

Maintainance of a stable equilibrium in the body’s internal environment

Question 5

What is Cell Signaling?

Answer 5

Communication at a cellular level.
One cell releases a Chemical that has an effect on another cell (target cell).
Cell Signalling can:
Transfer signals locally, e.g. between neurones at synapses - neurotransmitter = signal
Transfer signals across large distances, using Hormones, e.g. ADH

Question 6

Coordination in plants

Answer 6

Hormonal only - plants do not have nervous systems.

Question 7

Reflex Arc

Answer 7

(stimulus is detected by) Receptor
Sensory neurone
Relay neurone
Motor neurone
Effector (carries out appropriate response)

Question 8

Types of Muscle

Answer 8

Skeletal - responsible for movement
Cardiac - only in heart, myogenic (contract without need for nervous stimulus = heart beats in regular rhythm)
Involuntary - in walls of hollow organs and blood vessles

Question 9

Structure & Function of Skeletal Muscles

Answer 9

Striated appearance
Voluntary/Conscious control
Regular arrangement = muscle contracts in one direction
Rapid contraction speed
Short length of contraction
Fibres are tubular and multinucleated

Question 10

Structure & Function of Cardiac Muscles

Answer 10

Specialised Striated appearance
Involuntary Control
Cells branch and interconnect = simultaneous contraction
Intermediate contraction speed
Intermediate length of contraction
Fibres are Branched and Uninucleated

Question 11

Structure & Function of Involuntary Muscle

Answer 11

Non-Striated
Involuntary Control
No regular arrangement - different cells can contract in different directions
Slow contraction speed
can remain contracted relatively long time
Fibres are Spindle Shaped and Uninucleated

Question 12

What are Skeletal Muscle made up of?

Answer 12

Skeletal Muscles are made up of
bundles of Muscle Fibres, enclosed withing the Sarcolemma (membrane).
Muscle fibres contain a number of nuclei and are longer than normal cells = makes muscles stronger as fewer junctions (point of weakness).
Sarcoplasm = shared cytoplasm within a muscle fibre

Question 13

What are T Tubles?

Answer 13

Transveres Tubles = inward folds of sarcolemma
Help to spread electrical impulses throughout the sarcoplasm, ensuring whole of the fibre recieves the impulse to contract at the same time.

Question 14

What do Muscle Fibres have lots of?

Answer 14

Mitochondria to provide ATP for contraction.

Sarcoplasmic Reticulum - contains Ca ions required for mucle contraction; extends throughout the muscle fibre.

Question 15

Make-up of Myofibrils?

Answer 15

Long Cylindrical Organelles made of Actin & Myosin, specialised for contraction.
Collectively very powerful - lined up in parallel to provide maximum force when all contract together.

Question 16

Light-Bands / I-bands

Answer 16

region where actin and myosin filaments don’t overlap

Question 17

Dark bands / A-bands

Answer 17

Dark due to presence of myosin. Actin overflaps myosin at edges

Question 18

Z-line

Answer 18

line at centre of each light/I band

Question 19

What is a Sarcomere?

Answer 19

Distance between each Z-line; the functional unit of the myofibril.
Shortens when muscle contracts

Question 20

H-zone

Answer 20

Lighter coloured region found at centre of each dark/A band. Only Myosin filaments are present.
H-zone decreases when muscle contracts.

Question 21

bands/zones when Muscle Contracts:

Answer 21

Myosin filaments pull the actin filaments inwards toward the centre of the sarcomere, resulting in:
Light bands/I-bands become narrower
Z-lines move closer togther = Sarcomere shortens
H-zone becomes narrower
The Simultaneous Contraction of many sarcomeres means the myofibrils and therefore muscle fibres contract, resulting in enough force to pull on a bone and cause movement - muscle relaxes when sarcomeres return to their origninal length.

Question 22

Structure of Myosin

Answer 22

Globular heads have binding sites for actin & ATP, and are hinged to allow them to move forward and back.
The tails of several hundred myosin molecules are aligned together, forming the myosin filament.

Question 23

Structure of Actin

Answer 23

Actin-Mysoin Binding Sites - blocked by tropomyosin, held in place by troponin when muscle is relaxed.
When muscle is stiumulated to contract, the myosin heads form bonds with actin filaments; actin-myosin cross-bridges. Myosin heads flex/change angle in unison, pulling the actin filament along the myosin filament. Myosin detatches from the actin and its head returns t its original angle using ATP. The Myosin reataches further along the actin filament.

Question 24

Muscle contraction, starting at Neuromuscular Junction

Answer 24

muscle contraction is triggered when an action potential arrives at a NMJ
Ca2+ ion channels open and diffuse into the synaptic knob (from synapse) where they cause synaptic vesicles to fuse with the presynaptic membrane, releasing Acetylcholine into the synaptic cleft (exocytosis) & it diffuses across the synapse.
Acetylcholine binds to receptors on the postsynaptic membrane (sarcolemma), opening Na+ ion channels, resulting in depolarisation.
Acetylcholinesterase breaks acetylcholine into choline and ethanoic acid, preventing muscle being over stimulated - re-uptake.

Question 25

Define Motor unit

Answer 25

Motor unit = all musce fibres supplied by a single motor neurone

Question 26

Depolarisation of Sarcolemma

Answer 26

Depolarisation of sarcolemma travels deep into musclr fibre through T-tubules (in contact woth sarcoplasmic retculum, contaiing Ca2+ ions)
When action potential reaches S.R it stimulates Ca ion channels to open and diffuse out down cond. grad., flooding the sarcoplasm.
The Ca2+ ions bind to troponin causing it to change shape. this pulls tropomyosin away from the actin-myosin binding site. Myosin heads now form actin-myosin cross-bridges.
Myosin heads flex once attached, pulling the actin filament. The ADP bound to myosin is released and ATP replaces it = head detatches from actin.
Myosin hydrolyses ATP, releasing energy, used to move the mosin head back to original position, reattaching at another actin binding site.

Question 27

Creatine Phosphate

Answer 27

stored in muscles; acts as reserve store of phosphate available immediately to combine with ADP = ​ATP. Stores are used up quickly so only used for short-bursts of vigorous exercise.

Question 28

Sensors can be used to monitor the electrical activity in a muscle; to measure strenghth of muscle contraction or to track muscle fatigue.
Electromyography :
What is an Electromyogram? (EMG)

Answer 28

Use of Electrodes (which detect electrical currents created when muscles contract) to gain the signal trace (EMG).
Changes in this signal are used to identify fatigue:
increase in mean amplitude
decrease in frequency of the signal
disruption to overall pattern existing within the signal
An EMG is a record of the electrical activity in a muscle during contraction.