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PS1106 - BRAIN AND BEHAVIOUR > HORMONES: NOCICEPTION AND ANALGESIA > Flashcards

HORMONES: NOCICEPTION AND ANALGESIA Flashcards

(42 cards)

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1
Q

What do neurotransmitters do?

A
  • communication between neurons
  • released from neuronal terminal
  • released into synapse
  • action very local - within the synapse
  • action fast and short lasting
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2
Q

Describe what hormones do?

A
  • communication between many cell types
  • released from endocrine cells
  • released inot blood circulatory system
  • action widespread
  • action relatively slow and long lasting
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3
Q

Describe what neurohormones?

A
  • intermediate class of chemical signallers
  • share similarities with both
  • release from cells resembling neurons
  • released into blood circulatory system
  • action normally relatively local
  • action fairly fast and can be long or short lasting
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4
Q

Whats the main hormone secreting in the brain?

A

The pituitary gland ( hypophysis)

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5
Q

What do the hormones secreted from the pituitary gland control?

A

Secretion from many other glands

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6
Q

Where is the pituitary gland attached to?

A

The hypothalamus of the brain, which controls much of the secretion from the pituitary gland

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7
Q

What are the two distinct lobes in the pituitary gland?

A

Anterior - adenohypophysis
Posterior - neurophypophysis

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8
Q
A
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9
Q

Where is the anterior pituitary gland in?

A

Endocrine gland

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10
Q

What happens in the anterior pituitary gland?

A
  • neurosecretory cells in the hypothalamus secrete hormones into blood capillaries in the hypothalamus
  • the blood then flows through the hypothalamic - pituitary portal system to a secondary capillary bed in the anterior pituitary
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11
Q

What cells control the hormones secretion from the anterior pituitary ?

A

Hypothalamic - pituitary portal system

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12
Q

Hypothalamic releasing hormones stimulate the…..?

A

Anterior pituitary which release hormones into the main blood system,
Which in turn stimulate other organs to release their hormones

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13
Q

Whats the hormones released from the anterior pituitary?

A
  • adrenal Cortex - glucocorticoids
  • thyroid - thyroid hormones
    Gonads - females ovaries, progesterone, oestrogens
    Males testes, testosterone
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14
Q

Whats the posterior pituitary (neurohypophysis) and what does it do?

A

An extension of the brain
Hormones are synthesised and secreted by brain neurosecretory cells
Cell bodies of the axonx are in the hypothalamus
The axons extend into he posterior pituitary

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15
Q

What are examples of the hormones the posterior pituitary release?

A

Anti-diuretic hormone
Oxytocin

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16
Q

What are pheromones?

A

Signal transmission between inviduals
Chemicals released by one individual and affecting other individuals

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17
Q

Whats the pheromones importance in insects?

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A

Promotes social functioning
Promote cooperation in
Used in territorial behaviour
Danger signals which promote aggression

18
Q

Where are phenomens detected?

19
Q

Define pain?

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A

The subjective ‘feeling’ due to a noxious stimulus

20
Q

How are pheromes involved in humans?

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A

May be involved in human sexual responses, including attraction
Potential use by the cosmetics industry

21
Q

Define analgesia?

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A

The modulation of nocicpetion or pain

22
Q

Define transduction?

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A

Og a noxious stimulus inot electrical activity in appropriate nerve endings

23
Q

Define nocicpetion?

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A

The perception of a noxious stimulus

24
Q

Define transmission?

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A

Of the electrical signal through nerves, to the spinal cord and the brain

25
Define perception?
The noxious stimulus in brain areas, and the conscious ‘feeling’ of pain
26
Define modulation?
Signal at various levels (analgesia)
27
Explain what happens in transduction?
Noxious stimuli activate peripheral nociceptors - mostly polymodal, responding to mechanical, thermal and chemical stimuli - some uni modal - responses mediated through a number of signalling chemicals
28
Explain what happens in peripheral transmission?
Peripheral nociceptive fibres enter spinal cord through the dorsal root and terminate in the dorsal horn • Synapse in dorsal horn with both ascending axons projecting to the brain and spinal interneurones • Neurotransmitters at the spinal cord: glutamate and substance P
29
Explain the central transmission?
- Ascending axons cross the midline and travel via the anterolateral column of the spinal cord. - They terminate in the thalamus, with collateral branches ending in the brainstem. - From the brainstem, signals also project to the thalamus. - The thalamus projects to: The somatosensory cortex (for localization of pain)- pain consciously felt The cingulate cortex (for emotional processing of pain) There are reciprocal connections between the somatosensory and cingulate cortices.
30
Where is the perception of the pain?
- The cingulate cortex is activated even during imagined pain - Pain is subjective, based on input from nociceptive (pain) fibres - The brain can perceive pain without actual tissue damage (e.g., phantom limb, placebo, empathy) - The mechanism of pain perception is still not fully understood
31
Whats the earliest know drug used by man?
Opium which comprised the dried sap of the opium poppy - sedative and analgesic - well known to ancient Greeks
32
What are the two main active components of opium?
Morphine - 10% Codeine - 0.5% Morphine is poorly absorbed orally hence to produce central effects its injected
33
Whats opiate or opioid?
Active components of opium, and drugs with simialr pharmacologically
34
What does morphine act as?
Binding sites in the brain and spinal cord
35
What are the effects of morphine blocked by?
Naloxone suggesting that morphine is an agonist not a antagonist Morphine is not endogenous
36
What are the specific receptors found in opioids?
U (mu) - receptors = most sensitive to morphine and to endorphins & (delta) receptors = most sensitive to enkephalins K (kappa) receptors = most sensitive to dynorphines
37
How is morphine put into the body?
Injected into lateral ventricles relieves severe pain - effective at does 10-fold lower that for systemic injection, therefore acting in the brain
38
What induces the analgesia?
Morphine injected into: Periaqueductal grey (PAG) Periventricular grey (PVG) Rostroventral medulla (RVM) → Produces analgesia (pain relief) These effects are blocked by naloxone - which is injected into PAG, PVG, RVM Which confirms that morphine acts on opioid receptors in these brain regions
39
What are the similarities between opioid analgesia and stimulation produced analgesia?
Effective loci are the same in each case - both are blocked by naloxone - combining sub-analgesic levels of both produces analgesia - cross-tolerance develops between the two - both efffects cause blockade of spinal cord - both effects activate the same descending spinal pathway - dorsolaterlal funiculus
40
Where is stimulus produced analgesia mediated through?
Opioid mechanism
41
How are opioids involved in pain modulation across supraspinal, spinal, and hormonal pathways?
Supraspinal - brainstem • opioid receptor activation in brain stem • mediated via spinal cord mechanisms • mu-receptor mediated (i.e. endorphins) Spinal - spinal cord • opioid receptors activation in spinal cord • delta- & kappa- receptor mediated (enkephalins & dynorphins) Hormonal • stress-induced analgesia is reversed by naloxone • also reversed by removal of adrenal glands • mechanism is unclear
42
How do adrenaline, serotonin, and other substances modulate pain in the brain, spinal cord, and periphery
Brain stem - no adrenaline and 5HT modulate analgesia - especially in PAG and PVG - mechanism not clearly understood Spinal cord - no adrenaline injected into spinal cord blocks responses to noxious stimuli - 5HT injected into spinal cord is analgesic - block spinal cord nociceptive neurons - blocks spine-thalamic neurons Periphery - anti-histamines and anti-inflammatories reduce impact of the injury - local anaesthetics reduce transmission of the signal

PS1106 - BRAIN AND BEHAVIOUR (30 decks)

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