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A Level Biology Flashcards - BB > 26 The nervous system > Flashcards

26 The nervous system Flashcards

1
Q

what are the two subdivisions of the peripheral NS?

A

autonomic NS

somatic NS

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2
Q

what are the two subdivisions of the somatic NS?

A

sensory neurones

motor neurones

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3
Q

what is the function of the somatic NS?

A

conscious control of skeletal muscle

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4
Q

what is the neurotransmitter associated with the somatic NS?

A

acetylcholine (ACh)

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5
Q

what is the function of the autonomic NS?

A

subconscious control, allowing reaction to the environment and internal changes and appropriate behaviour modification

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6
Q

what is the difference in myelination between somatic NS neurones and autonomic neurones?

A

somatic myelinated completely

autonomic myelinated only CNS -> ganglion (not ganglion -> receptor)

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7
Q

what is the pre-ganglionic neurotransmitter in the autonomic NS?

A

acetylcholine (ACh)

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8
Q

what is the neurotransmitter used in the

  • parasympathetic
  • sympathetic

divisions of the autonomic NS?

A

parasympathetic = acetylcholine (ACh)

sympathetic = noradrenaline (NAdr)

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9
Q

outline functions of the parasympathetic NS

A

digestion/movement of food through gut

slows h.r.

dilates arteries and arterioles

contracts circular muscles in iris –> pupil constricts

erector pili relax –> hairs lie flat

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10
Q

outline functions of the sympathetic NS

A

slows movement of food through gut

increases h.r.

constricts arteries and arterioles

contracts radial muscles in iris –> pupil dilates

erector pili contract –> hairs stand erect

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11
Q

in which division of the autonomic NS are the ganglia linking neurones found within the target organ?

A

parasympathetic

sympathetic’s are close to the spinal cord

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12
Q

what is the role of the cerebrum?

A

conscious thought/reasoning

emotional understanding

language

contralateral control

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13
Q

what is the role of the corpus callosum?

A

hemispheric communication

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14
Q

what is the role of the cerebellum?

A

muscle co-ordination

non-voluntary movement (i.e. reflexes)

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15
Q

what is the role of the medulla oblongata?

A

autonomic control of:

  • heart rate
  • breathing rate
  • blood pressure
  • peristalsis
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16
Q

what is the role of the hypothalamus?

A

homeostasis

osmoregulation

production of hormones secreted by the posterior pituitary gland

production of releasing factors to stimulate hormone secretion from the anterior pituitary

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17
Q

what is the role of the

  • posterior
  • anterior

pituitary gland?

A

posterior = storage and secretion of hormones produced by the hypothalamus

anterior = production and secretion of hormones

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18
Q

what is an axon?

A

a single elongated nerve fibre extending away from the cell body

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19
Q

what is a dendrite?

A

a short extension of cell and cytoplasm to increase the surface area of the neurone for receiving impulses from other neurones

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20
Q

what is the structure and function of the myelin sheath?

A

layers of plasma membrane produced by Schwann cells

wrap the axon and make it impermeable to Na+/K+

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21
Q

what is the function of the Nodes of Ranvier?

A

small (2 - 3 um) gaps every 1 - 3 mm along the axon

sites of depolarisation allowing saltatory conduction –> faster conduction of nerve impulses

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22
Q

what is the resting potential?

A

when a neurone is not transmitting an impulse or action potential

~ -60 mV

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23
Q

why is the resting potential of the interior of a neurone negative compared to its outside negative?

A

Na+/K+ channels and pump open/working

interior of cell has large inorganic ions

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24
Q

outline the procedure of an action potential

A

1) resting potential

2) depolarisation
- stimulus energy causes Na+ channels to open
- Na+ ions enter down e-chem gradient
- p.d. of membrane reverses
- more Na+ channels open (voltage-gated) (+ve feedback)

3) action potential
- +40 mV reached
- Na+ channels close / voltage-gated K+ channels open
- membrane returns to resting potential

4) repolarisation
- ionic balance restored by pump
- refractory period

5) hyperpolarisation
- K+ channels too slow to close
- ∴ overshoot of p.d. beyond -60 mV
- pump restores resting potential

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25
Q

what is the definition of a refractory period?

A

the period in which no further action potentials can be generated

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26
Q

what is the purpose of the refractory period?

A

prevents action potential from going in reverse

controls frequency

in cardiac muscle, refractory period = diastole –> allows time for chambers to refill

27
Q

outline the process of propagation of a nerve impulse

A

Na+ diffuse sideways along axon

Na+ channels in next region open

Na+ diffuse in –> depolarisation

28
Q

what is saltatory conduction?

A

when an action potential ‘jumps’ from one node to another

29
Q

what are the advantages of saltatory conduction?

A

increases transmission speed

conserves energy - fewer ion pumps/channels

30
Q

what are the factors affecting the speed of action potential transmission?

A

temperature: more Ek of ions –> faster diffusion

axon diameter: larger = faster transmission (less resistance)

31
Q

what is a synapse?

A

a junction between two neurones, or between a neurone and an effector

32
Q

what are the specialised features of the synaptic knob?

A

many mitochondria

lots of SER

voltage-gated Ca2+ channels

33
Q

outline the process of synaptic transmission

A

a.p. reaches pre-s knob

depolarisation causes Ca2+ channels to open

Ca+ diffuse in

synaptic vesicles triggered to fuse with pre-s membrane

NT released via exocytosis into cleft

NT binds to specific, complementary receptors on post-s membrane

Na+ channels on post-s membrane open

if sufficient Na+ enter, depolarisation ∴ a.p. triggered

34
Q

what happens to the neurotransmitter after synaptic transmission?

A

must be removed to prevent stimulus being maintained

broken down by enzymes in cleft

products reabsorbed by pre-s knob by endocytosis

reformed using ATP and packaged into vesicles for next use

35
Q

what is an EPSP?

A

{excitatory post-synaptic potential}

increased likelihood of a.p. occurring in post-synaptic neurone - membrane potential –> less negative

36
Q

what is an IPSP?

A

{inhibitory post-synaptic potential}

decreased likelihood of a.p. occurring in post-synaptic neurone - membrane potential –> less negative

37
Q

what is the role of synapses?

A

ensures impulses are unidirectional

allows synaptic divergence

allows synaptic convergence

38
Q

what is summation?

A

the effect of combined neurotransmitters

39
Q

what are the two types of summation?

A

spatial:

  • lots of pre-s connected to one post-s
  • accumulation of NT in synapse
  • a.p. triggered in single post-s

temporal:

  • NT released several times - builds up in quick succession
  • a.p. triggered
40
Q

what is the function of reflex arcs?

A

to allow rapid responses to prevent harm to the body

41
Q

outline the plantar reflex

A

indicates brain/spinal cord damage

bottom of foot poked - normal: flex down ; abnormal: flex up

42
Q

outline the pupillary light reflex

A

indicates damage to brain/optic nerve

light shone in both eyes - should constrict to same degree

43
Q

what are the advantages of reflex arcs?

A

involuntary

do not need to be learnt

extremely fast

44
Q

what is the definition of acquired brain injury?

A

any brain injury that occurs after birth

45
Q

what are the two types of brain injury?

A

traumatic - involves a severe blow to the head (e.g. RTC/mugging)

non-traumatic - no severe blow (e.g. stroke/infection)

46
Q

how does a stroke occur?

A

blood vessel supplying brain becomes blocked

OR

blood vessel ruptures and bleeds into brain (subdural haematoma)

47
Q

when is a person considered ‘dead’?

A

when there is no activity in the brain stem

48
Q

how could drugs be used to treat Alzheimer’s?

A

cholinesterase inhibitors –> prevent hydrolysis of ACh

∴ increased ACh concentrations

∴ increased functioning/restoration of lost functioning

49
Q

what are the actions of non-steroidal anti-inflammatory drugs (NSAIDs)?

A

inhibit inflammation response

reduce pain

reduce fever

50
Q

what are the causes and symptoms of Parkinson’s?

A

loss of dopamine producing cells

leading to increased muscle tension

leading to joint rigidity and slow movement

51
Q

how could therapeutic drugs be used to treat Parkinson’s?

A

levodopa –> metabolised to dopamine

dopamine agonists –> mimic dopamine

monoamine oxidase inhibitors –> inhibition of enzymes that break down dopamine

52
Q

what is the effect of alcohol on the NS?

A

inhibition of neurotransmission across synapses –> loss of motor skills and co-ordination

binds to a number of synaptic receptors

53
Q

what is the effect of heroin on the NS?

A

an opioid - converted to morphine in brain and binds ti opioid receptors

leading to clouded cognitive function, and reduced h.r./b.r.

54
Q

what is the effect of marijuana on the NS?

A

THC - similar to anandamide (a natural cannabinoid)

temporarily releases dopamine

THC not broken down quickly and blocks GABA

55
Q

what is the effect of methamphetamines on the NS?

A

affect excitatory synapses in neurones by increasing dopamine released at synapses

slow to be broken down ∴ effect of dopamine prolonged

56
Q

what is the function of the limbic system?

A

long term memory creation, behaviour and emotions

influences endocrine system and autonomic NS

57
Q

what is the effect of excess dopamine on the limbic systems?

A

dopamine released by hypothalamus for reward-motivated behaviour/actions and creates desire for it to be repeated

ongoing dopamine activity activates limbic system and changes brain to state of dependency

58
Q

what is the definition of addiction?

A

when a tolerance to a substance builds up so that more of it is required to produce the same effect

59
Q

what is the definition of dependency?

A

when a substance is required by the body for normal functioning

60
Q

give an example of a biochemical reaction to drug use

A

increased enzymes required to break down drug

reduction in sensitivity of synapse

61
Q

what are the reasons that might cause someone to develop an addiction?

A

social (i.e. peer pressure)

emotional (e.g. anxiety issues)

depression/malfunctioning

62
Q

what are the consequences of addiction?

A

can become dominant in life

reduces ability for basic functions

can lead to criminal behaviour

63
Q

what are the costs to society of addition?

A

healthcare costs

costs of criminal activity

policing and customs to prevent trafficking

loss of abuser’s contribution to economy

social breakdown as behaviour detoriorates

A Level Biology Flashcards - BB (35 decks)

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