Nervous Coordination Flashcards
1
Q
Describe the cell membrane of a neurone at resting state
A
- Outside: +ve charged compared to inside
- bc more +ve ions outside
- Membrane = polarised (diff. charge)
2
Q
Define potential diff/voltage
A
Diff in charge
3
Q
What is the v called when at rest?
A
- Resting potential
- -70v
4
Q
The sodium-potassium uses ____ so ___ is required
A
- AT
- ATP
5
Q
How is the resting potential created + maintained?
A
- Sodium potassium pump
- 3 Na+ moves out neurone, membrane not permeable so can’t diffuse back in
- Creates Na+ electrochemical gradient
- Pump also moves 2 K+ in neurone but membrane permeable so (facilitated) diffuse out through potassium ion channel
- Makes outside +ve charged compared to inside
6
Q
When does an action potential occur?
A
- Stimulus big enough, Na+ channels open
- Triggers rapid change in potential diff
7
Q
What happens in the refractory period?
A
- Neurone cell membrane can’t be excited straight away
- bc ion channels are recovering
- Na<strong>+</strong> channels closed during repolaristion + K+ channels closed during hyperpolarisation
8
Q
Explain how the action potential moves along the neurone as a wave of depolarisation
A
- During AP, some Na+ that enter neurone diffuse sideways
- Causes Na+ channels in next region to open + Na+ diffuse into that part
- Causes wave of depolarisation to travel along neurone
- Wave moves away from parts of membrane in refractory period bc can’t fire AP
9
Q
The refractory period acts as a time delay, what does the mean?
A
- AP don’t overlap but pass along as descrete impulses
- Limit to freq to which impulses can be transmitted
- AP are unidirectional (1 direction)
10
Q
Action potentials have an all or nothing nature, what does this mean?
A
- Once threshold is reached, AP will always fire w/ same charge in v
- If threshold not reached, AP won’t fire
11
Q
What does a bigger stimulus result in?
A
More frequent AP
12
Q
What factors affect the speed of conduction of action potential?
A
- Myelination
- Axon diameter
- Temp
13
Q
What is myelination?
A
When neurones have myelin sheath - electrical insulator
14
Q
In the peripheral NS, what is the sheath made from?
A
Schwann cell
15
Q
What are the sections btw the schwann cells?
A
Bare membrane - nodes of Ranvier
16
Q
What are conc at the nodes?
A
Na+ channels
17
Q
How does the action potential go across through a myelinated neurone?
A
Saltatory conduction
18
Q
How does saltatory conduction take place?
A
- Depolarisation only occurs at nodes of ranvier
- Cytoplasm conducts enough electrical charge to depolarise next node, so impulse jumps node to node
19
Q
How does an impulse travel along a non-myelinated neurone?
A
Travels as wave along whole length of axon membrane
20
Q
Does an impulse travel faster along a myelinated or a non-myelinated neurone? Why?
A
- Myelinated
- Saltatory conduction allows impulses to travel quickly
21
Q
How does the axon diameter affect speed of conduction?
A
- Bigger diameter = less resistance to flow of ions
- Depolarisation reaches other parts of neurone membrane faster
22
Q
How does the temperature affect speed of conduction?
A
- Temp inc = ions diffuse faster
- Only upto 40ºc bc proteins denature + speed dec
23
Q
Define synapse
A
Junction btw neurone + another neurone, neurone + effector cell
24
Q
How does synapses ensure that nerve impulses are unidirectional?
A
Reeceptors only on post synaptic membrane
25
Why and how are the NT removed from the cleft?
* So **response doesn't keep happening**
* **Taken back** into **presynaptic neurone**
* **Broken down** by **enzymes**
26
Define excitatory NT
**Depolarise post synaptic membrane**, making it **fire** an **action potential** if the **threshold** is **reached**
27
Define inhibitory NT
**Hyperpolarise post synaptic membrane**, **preventing** it from firing an **AP**
28
Define summation
**Effect** of **NT release**d from **many neurones** is **added together**
29
Spatial summation
* **Many neurones connect** to **1** neurone
* **Small amounts** of NT **released** from each **neurone** can be enough **altogether** to **reach threshold** in **postsynaptic neurone** + **trigger AP**
* If **inhibitory NT** released = **no AP**
30
Temporal summation
* **2/more nerve impulses** arrive in **quick sucession** from **same presynaptic neurone**
* Makes **AP more likely** bc **more NT** released into **synaptic cleft**
31
What does summation mean for synapses?
Synapses can **accurately process info**, **finely tuning response**
32
Define neuromuscular junction
Synapses btw **motor neurone** + **muscle cell**
33
What does acetylcholine bind to in neuromuscular junctions?
Cholinergic receptors called **nicotine cholinergic receptors**
34
What are the diff btw cholinergic synapses + neuronmuscular junctions?
* **Post synaptic mebrane** has **lots** of **folds** that form **clefts** - **stores enzyme** that **break down ACh** (**acetyl cholinesterase**)
* **More receptors**
* **ACh** always **excitatory** at **neuromuscular junction**- **motor fires AP** = **tiggers response** in **muscle cell**
35
What are agonist drugs + what do they do?
* **Same/similar shape** as **NT** so **mimic** their ac**t**ion at **receptors**
* Means **more receptors** are **activated**
36
What are antagonist drugs + what do they do?
* **Same/similar shape** as **NT** so **block receptors** so **can't** be **activated**
* **Fewer receptors can** be **activated**
37
What happens when drugs inhibit enzymes that break down NT?
**More NT** in **synaptic cleft** to **bind** to **receptors** + they're there for **longer**
38
What do some drugs stimulate the release of?
**NT** from **presynaptic neurone** so **more receptors** are **activated**
39
What do some drugs inhibit the release of?
**NT** from **presynaptic neurone** so **fewer receptors** are **activated**
40
Describe how a nerve impulse is transmitted across a cholinergic synapse (8)
* **Impulse** causes **Ca**2+ to **enter axon**
* **Vesicles move** to **presynaptic membrane**
* **Acetylcholine released**
* **Diffuse** across **synaptic cleft**/synapse
* **Binds** w/ **receptor** on **post synaptic membrane**
* **Na+ enter post synaptic neurone**
* **Depolarisation** of **post synaptic membrane**
* If **above threshold**, **AP produced**
41
Skeletal muscles
Muscles you use to **move**
42
Tendons
Attach **skeletal muscles** to **bones**
43
Ligaments
Attach **bones** to **bones**
44
Why are muscles described as antagonistic pairs?
* **Contracting** muscle: **agonist**
* **Relaxing** muscle: **antagonist**
* **Bones** of skeleton are **incompressible** so act as **lever**, giving **muscles** something to **pull against**
45
Outline the structure of a skeletal muscle
* **Large bundles** of **long cells** - **muscle fibres**
* **Cell membrane** of muscle fibre - **sarcolemma**
* Sarcolemma **fold inwards** + **stick** into **sarcoplasm**, folds = **transverse tubule,** help **spread electrical impulse throughout sarcoplasm**
* **Network** of **internal membrane** (**sarcoplasmic reticulu**m) runs through sarcoplasm, **stores** + **releases Ca2+** needed for contraction
* **Lots** of **mitochondria** provide **ATP**
* **Multinucleate**
* Made up of **myofibrils**, **specialised** for **contraction**
46
Myosin
* **Thick myofilament**
* **Dark**
* **A band**
47
Actin
* **Thin myofilament**
* **Light**
* **I band**
48
Contracted sarcomere
* **A band** stays **same**
* **I band**, **H zone** + **sarcomere** gets **shorter**
49
Outline the structure of myofibrils when a muscle is at rest
* **Actin-myosin binding site** is **blocked** by **tropomyosin**
* **Myofilaments** **unable** to **slide** past bc **myosin head can't bind**
50
Outline the process when muscles contract
* **AP depolarises sarcolemm**, spreads to **t tubules** + down **SR**, **releases Ca2+** to **sarcoplasm**
* Ca2+ **binds** to **protein** on **tropomyosin**, **changes** **shape** **pulling tropomyosin out AM binding site** on actin
* **Exposes binding site** allowing **myosin head** to **bind**, forming **AM cross bridges**
* **CA2+ activates ATP hydralase**, hydrolysing ATP
* **Energy** causes **myosin head** to **bend**, **pulling actin filament along**
* Another **ATP provides energy** to **break AM cross bridge** so **myosin head detaches**
* **Myosin head reattaches** to **another binding site**
51
What happens when muscles relax?
* **Ca2+ leave binding site** + **AT** into **SR**
* Causing **tropomyosin** to **block AM binding site**
* **Actin filament** slides back to **relaxed position**, **lengthens sarcomere**
52
Aerobic respiration
* **ATP generated** via **OP** in **mitochondria**
* **Oxygen available**
* **Long periods** of **low intenisity exercise**
53
Anaerobic respiration
* **ATP** generated **rapidly** by **glylosis**
* **Pyruvate** → **lactate** - causing **muscle fatigue**
* **Short periods** of **hard exercise**
54
ATP phosphocreatine system
* ATP made by **phosphorylating ADP** - **adding phosphate** group from **PCr**
* **PCr stored** inside **cells** but **runs out quickly**, **short bursts** of **vigorous exercise**
* **Generates ATP quickly**
* **Anaerobic**
* **Alactic**
55
Slow twitch muscle fibres
* **Contract slowly**
* **Endurance** activity
* Work for **long time w/o getting tired**
* **Energy** **released slowly** via **aerobic respiration**, **lots** of **mitochondria** + **blood vessels**
* **Red** bc **rich** in **myoglobin**
56
Fast twitch muscle fibre
* **Contracts quickly**
* **Short bursts** of **speed** + **power**
* Get **tired quickly**
* **Energy released quickly** via **anaerobic respiration** using **glycogen**. **Few mitochondria** + **blood vessels**
* **White** bc **lacks myoglobin**
