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Control and Co-ordination in mammals
Nervous vs endocrine system
Nervous system
Cell signalling

Endocrine system

Both involve cell signalling

Detail

Both involve signal molecule binding to receptor

Chemicals

Both involve chemicals

Communication

Action potential / impulse

Hormone

Nature of communication

Electrical and chemical

Chemical

Mode of transmission

Neurone / nerve cell

Blood

Response destination

Muscle / gland

Target organs / tissue / cells

Transmission speed

fast

Slow

Effects

Specific / localised

Can be widespread

Response speed

fast

Slow

Duration

Short-lived

Long-lasting

Receptor location

On cell surface membrane

Either on cell surface
membrane or within cell

Structure of
- Sensory neurone
- Nucleus in cell body (C)
- Long dendron
- Short axon
- Many mitochondria in cell body
- Many ribosomes in cell body
- Synaptic knobs
- Schwann cells / myelin sheath
- Nodes of Ranvier
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Motor neurone
- Dendrites lead to cell body
- Nucleus in cell body
- Many mitochondria in cell body

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Much RER in cell body
Long axon
Synaptic knobs at end furthest from cell body
Schwann cells / myelin sheath
Nodes of Ranvier

Roles of sensory receptor cells in detecting stimuli and stimulating the transmission of
nerve impulses in sensory neurones
*​chemoreceptor cell in human taste bud
1
...
Sodium ions of salt acts as stimulus
3
...
Sensory cell membrane depolarises
5
...
When conc
...
Voltage-gated calcium ion channels will open
8
...
Action potential stimulates neighbouring area of membrane
2
...
Causes Na+ ion channels to open
4
...
Myelin sheath insulates axon
6
...
Saltatory conduction
*Importance of sodium and potassium ions in impulse transmission
- Sodium potassium pump maintains resting potential
- Membrane polarised during resting potential (negative inside, positive outside)
When sodium potassium pump stops working,
- Ions move by diffusion
- Sodium ions into neurone through non voltage-gated channels
- Potassium ions stay in neurone
- Eventually, inside of neurone becomes less negative
- Membrane of neurone depolarises

Importance of myelin sheath in
- Schwann cells wrap around the axon to form myelin sheath
- Insulates the axon
- Location without myelin known as nodes
- Nodes are 1-3 mm intervals
- Depolarisation only occurs at nodes of Ranvier
- Local circuits set up between nodes causes opening of sodium ion channels at next
node
- Causing next depolarisation
- Saltatory conduction
- Speeds transmission of impulse
- Speed increases up to 100ms-1
- Myelination prevents leakage of ions
- One way transmission

Structure of cholinergic synapse

A: vesicle containing acetylcholine
B: presynaptic membrane
C: synaptic cleft
D: postsynaptic membrane
E: receptors
Function
1
...
Voltage-gated calcium ion channels open and calcium ions enter pre-synaptic neurone
3
...
Vesicles fuse with pre-synaptic membrane
5
...
Acetylcholine diffuse across synaptic cleft
7
...
Ligand-gated sodium ion channels open and sodium ions enter post-synaptic neurone
a
...
d
...
Channels close when membrane repolarises
9
...
Threshold value exceeded (enough sodium ions)
11
...
Acetylcholinesterase breaks down acetylcholine into acetate and choline
13
...
Mitochondria produce ATP to reform vesicles and acetylcholine
*If acetylcholine not released from synapse, neurone will be constantly excited and cause
fatigue
- Action potentials generated for long time

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Cause release of other transmitters

*​Role of calcium ions
- Depolarisation / action potential opens calcium ion channels
- Channels on presynaptic membrane
- Calcium ions enter through presynaptic membrane
- Causes vesicles to move toward presynaptic membrane
- Causes vesicles of acetylcholine fuse with presynaptic membrane
- Exocytosis
*Role of mitochondria/ATP
- Produces ATP
- Energy for exocytosis
- Form acetylcholine
- Form the vesicle
- Vesicle movement
- Functioning of ion pumps
*Role of acetylcholinesterase
- Breaks down acetylcholine into acetate and choline
- Acetylcholine leaves receptor
- Stops continuous depolarisation of postsynaptic membrane
- Stops continuous action potentials
- ACh recycled

Role of synapses in nervous system in
- Allowing transmission in one direction
- Vesicles containing acetylcholine are found only in the presynaptic knob
- Acetylcholine receptors are found only on the postsynaptic membrane
- Refractory period
*​Advantages of increased number of synapses
- Improved memory
- More interconnection of nerve pathways
- Wider range of responses
- Summation

S​tructure of striated muscle (*sarcomere structure)

Thick Filament:
- myosin
- Fibrous protein
- Globular heads
- ATPase
- M lines
- 15nm diameter
Thin filament:
- actin
- Globular protein
- Tropomyosin / troponin
- Binding site for myosin head
- Z lines
- 7nm diameter
Sliding filament model of muscular contraction
1
...
Transverse tubules depolarised
3
...
Calcium ions bind to troponin
5
...
Tropomyosin moves
7
...
Myosin heads bind to site of actin

9
...
Actin pulled / power stroke
11
...
Myosin head lets go of actin
13
...
Process repeated
15
...
Fall in concentration of progesterone
2
...
Menstruation occurs
4
...
Oestrogen concentration rises
6
...
Corpus luteum secretes progesterone
8
...
Progesterone maintains endometrium

Biological basis of contraceptive pills containing oestrogen and/or progesterone
- Synthetic hormones used
- As they do not get broken down quickly
- Oestrogen and progesterone concentrations remain high
- Act on anterior pituitary gland
- Progesterone inhibits FSH secretion
- Follicle does not develop
- Oestrogen inhibits LH secretion
- Ovulation prevented
- Cervical mucus thickens to stop sperm
- Prevents implantation / endometrium less well developed
- Negative feedback
*Advantages of contraception method that does not involve oestrogen and progesterone

-

No unwanted side effects (nausea, mood swing, headache, weight gain)
Maintain natural hormone balance

Control and Co-ordination in plants
Venus fly trap
1
...
Sensory hair / trigger hair cell detects touch and cause formation of an action potential
*​two​ hairs touched within 35 seconds
3
...
When membrane potential more than threshold potential, action potential is generated
5
...
Action potential travels along csm through csm along plasmodesmata to midrib cells,
action potential spreads over lobe
7
...
Proton pumps pump H+ ions into cell wall spaces of midrib cell
9
...
Expansin breaks down non covalent bonds between cellulose microfibrils and
hemicellulose, and digests calcium pectate
11
...
Water enters cell through osmosis, midrib cells expand
13
...
Trap snaps shut quickly (0
...
Acid-growth hypothesis
2
...
Stimulates proton pumps in cell surface membrane
4
...
Pumps protons into cell wall spaces using energy / by active transport
6
...
pH-dependent enzymes activated such as expansins
8
...
Cell wall loosens / becomes more elastic
10
...
Water enters by osmosis through aquaporin
12
...
So cell wall expands

*​Apical bud is source of auxin
- Auxin inhibits growth of side shoot
- Removal of bud causes decrease in auxin concentration
- This allows cell elongation in side shoots

Role of gibberellin (GA) in germination of wheat or barley
1
...
DELLA protein inhibits germination, GA breaks down DELLA protein
3
...
Transcription of mRNA coding for amylase in aleurone layer
5
...
Glucose diffuses into embryo, source of energy for growth of seed, glucose respired by
embryo during germination

Role of gibberellin in stem elongation
1
...
GA binds to receptor
3
...
Transcription factor / PIF binds to DNA
5
...
Causes cell division
7
...
Causes cell elongation
9
...
Loosens cell wall
11

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