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Brain & Behaviour > Week 2 - Spinal Cord > Flashcards

Week 2 - Spinal Cord Flashcards

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1
Q

Which is more selective: presynaptic or post-synaptic modulation?

A

Pre-synaptic

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2
Q

All the connections between peripheral afferents and CNS neurons are __________

A

Excitatory

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3
Q

What is the major inhibitory neurotransmitter?

A

GABA

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4
Q

What are the types of GABA receptors? and how are they different from one another?

A

GABA(A): Cl- conductance, shunting of AP

GABA(B): GPCR that modulates K+ and Ca++ channels

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5
Q

What are Renshaw cells?

A

Interneurons that are critically important for recurrent inhibition

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6
Q

What is defective in someone affected with Clostridium tetani? how does this cause muscle symptoms?

A

Glycine Receptors are defective (normally these are inhibitory on muscle contraction so without them, get extreme contraction and no relaxation of muscles).

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7
Q

Describe the inverse myotatic reflex.

A

Golgi tendon organs are present in the tendons of muscles.

  • -> stretch of the tendon stimulates golgi tendon organ and sends an AP along the Ib afferent nerve fiber
  • -> Ib fiber stimulates both the agonist and antagonist interneurons
  • -> agonist neuron inhibits muscle contraction
  • -> antagonist neuron facilitates contraction of the antagonist muscle group
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8
Q

What type of nerve fibers, at what level of the spinal cord inhibit erection?
- stimulate erection?

A

Inhibition: sympathetic T11-L2

Excitation: Parasympathetic S2-4

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9
Q

At what level do the nerves in the lateral corticospinal tract decussate?

A

The caudal midbrain

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10
Q

What are neurons in the lateral corticospinal tract responsible for?
- in the anterior corticospinal tract?

A

Lateral – voluntary movement

Anterior – postural muscles

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11
Q

What regulates the excitability of the muscle spindle?

A

gamma-motor neurons

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12
Q

What levels of the spinal cord are responsible for the transmission of “psychogenic” erection?

A

T10 - L3 (sympathetic)

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13
Q

What levels of the spinal cord are responsible for the transmission of “reflex” erection?

A

S2-4 (parasympathetic)

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14
Q

How does morphine act?

A

Acts on Mu1 & Mu2 opioid receptors

- causes supraspinal analgesia & respiratory depression

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15
Q

How do enkephalins act?

A

Bind to delta opioid receptors

- cause spinal analgesia

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16
Q

What type of receptor is the opioid receptor?

A

G-protein coupled receptor – stimulation causes opening of K+ channels

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17
Q

What is the mechanism of action of opioids?

A
  1. Post-synaptic: opens K+ channels causing hyperpolarization.
  2. Pre-synaptic: closes Ca++ channels decreasing excitatory transmitter release.
  3. Activates inhibitory enkephalin interneurons
  4. Activates inhibitory descending pathways
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18
Q

What pharmaceutical opioid is 100x more potent than morphine (when both are given parenterally)?

A

Fentanyl

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19
Q

How does route of administration affect the bioavailability of morphine?

A

If giving oral dose, must give 3-6x as much as the parenteral dose.

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20
Q

Name a couple synthetic opioids.

A

Fentanyl, methadone

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21
Q

Name some natural alkaloids (extracted from opium).

A

Morphine, Codeine

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22
Q

How does norepinephrine affect sexual function?

A

Stimulates brain (excitement), but inhibits genitals (decreased arousal)

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23
Q

How does 5-HT affect sexual function?

A

Inhibitory action on:

  • interest
  • genital arousal
  • orgasm
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24
Q

How does a spinal cord lesion in the upper thoracic/cervical region affect sexual function?

A

Prevents psychogenic erection – can only get genital arousal by reflexogenic erection

25
Q

How does a spinal cord lesion in the sacral region affect sexual arousal?

A

Inhibits reflexogenic erections; psychogenic erections are still possible.

26
Q

How does a spinal cord lesion in the L4/5-S1 region affect sexual arousal?

A

Sexual arousal response is weakened.

27
Q

What are some possible causes of physiological genital arousal problems?

A
  • spinal cord injury
  • central or peripheral nerve disease (MS, Parkinson’s)
  • meds
  • med hx/underlying factors affecting vasculature (ex. diabetes, CVD, smoking)
28
Q

What is the physiological process of penile tumescence?

A
  • smooth muscle relaxation and compression of venules (against tunica albuginea) block venous outflow causing engorgement of vasculature
29
Q

What is the action of PDE-5i’s (Phosphodiesterase-5 inhibitors)?

What is the physiological pathway for erection leading up to cGMP formation?

A

Blocks the degradation of cGMP in the lining of the smooth muscle cells of corpus cavernosum –> this leads to increased blood flow to the penis.
- used in treatment of erectile dysfunction

Normally, NO is released in vasculature of corpus cavernosum –> activates gyanylate cyclase –> increases cGMP

30
Q

Name some PDE-5 inhibitors.

A

Viagra (Sildenafil), Cialis, Levitra

31
Q

What level of the spinal cord is responsible for the ejaculation reflex?

A

T10-S4

32
Q

What are the steps in ejaculatory inevitability?

A
  • closure of bladder neck
  • seminal fluid emission
  • closure of of external sphincter (increases intraprostatic pressure)
33
Q

What are the two phases of ejaculation?

A 
Seminal emission (sympathetic T10-L1; some voluntary control).
Propulsatile ejaculation/expulsion (parasymp & somatic; loss of voluntary control).
34
Q

What are some possible causes of ejaculation without orgasm?

A
  • spinal cord injury
  • MS
  • anhedonic ejaculation
35
Q

What are some possible causes of orgasm without ejaculation?

A
  • prostate removal
  • retrograde ejaculation
  • retroperitoneal lymph node dissectioin
36
Q

What neurological exam tests the capacity for erection/vaginal lubrication & accomodation?

A
  • sacral reflex (Bulbocavernosus reflex)
37
Q

What neurological exam tests the capacity for ejaculation?

A
  • sacral reflex
38
Q

What neurological exam tests can be used to asses the capacity for orgasm?

A

test neural tracts:

  • spinothalamic –> pinprick (differentiate sharp from dull) & temperature
  • corticospinal –> voluntary anal contraction
39
Q

What is PGE-1? pharmacologically, what is it used for?

A

Prostaglandin-E1 is a vasodilator

- used in treatment of erectile dysfunction

40
Q

What is the testicular squeeze test?

- what is a positive test?

A

Squeeze testicles gently and there should be some pain.

  • pain (positive test) indicates that innervation of T9-brain is intact
  • therefore, lesion (if present) would be below T9
41
Q

List points of sexual assessment in rehab patients.

A
  1. Sex drive/interest
  2. Sexual functioning
  3. Bowel/bladder functioning
  4. Motor/sensory functioning
  5. Factors specific to the condition
  6. Partnership concerns
  7. Fertility concerns
  8. Sexual self-view & self-esteem
42
Q

What are the sexual rehab principles?

A
  1. Maximize the physiology
  2. Adapt to limitations
  3. Stay positive & open to experiences
43
Q

What does the reticulospinal tract control?

A

Posture and strength of reflexes

44
Q

What happens when there is a lesion in the corticospinal tract?

A
  • UMNs cannot send message to interneurons
  • interneurons (which usually are inhibitory) do not send stimuli to LMNs
  • unrestricted flow of excitation reaches motor neurons
  • hyperreflexia & increased tone
45
Q

What are two reflex tests that can be reversed after UMN (corticospinal tract) lesion?
- what result would be present on each of these if there was an UMN lesion?

A

Babinski (stroke lateral plantar surface of foot and toes splay instead of curling up.
&
Bing (apply pinprick to dorsal aspect of foot and foot dorsiflexes into pin instead of away from it)

46
Q

What is the action of Baclofen and what is it used for?

A

It is a GABA(B) receptor agonist - acts presynaptically to reduce spasticity.

47
Q

What is the action of benzodiazepines such as diazepam?

A

Increases the frequency of GABA(A) receptor channel opening - increases post-synaptic inhibition to reduce spasticity

48
Q

What are the major inhibitory and excitatory neurons in the CNS?

A

Inhibitory: GABA & glutamate.

Excitatory: glutamate

49
Q

Activation of nicotinic receptors affects which ion channels? in what way?

A

increases Na+ & K+ conductance

50
Q

Activation of NMDA receptors affects which ion channels? in what way?

A

increases Na+, K+, & Ca++ conductance

51
Q

Activation of GABA(A) receptors affects which ion channels? in what way?

A

increases Cl- conductance

52
Q

Activation of GABA(B) receptors affects which ion channels? in what way?

A

decreases the open probability of Ca++ channels on presynaptic excitatory terminals.

53
Q

Into what do the dural venous sinuses drain?

A

Into the internal jugular veins

54
Q

What does the inferior sagittal sinus directly drain into?

A

The straight sinus.

55
Q 
Which nerves (involved in the reflex arc) are affected after a spinal cord injury above the level of the reflex arc?
 - how are they affected?
A
  • increased alpha-motor neuron activity during reflex
  • increased gamma-motor neuron activity without reflex (causing increased muscle tone)
  • increased 1a afferent fiber activity during reflex
56
Q

What is the denticulate ligament composed of?

A

Pia mater & glial cells

57
Q

Which spinal cord tracts are necessary for genital orgasm?

A

Spinothalamic & Corticospinal

58
Q

What occurs during microglial activation in the absence of cell death?

A

Microglia secrete cytokines

Brain & Behaviour (4 decks)

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