LO PNS

Question 1

Identify the neuronal components of the Peripheral Nervous System (PNS) and the Autonomic Nervous System (ANS) and know the neurotransmitters and receptor types used by PNS and ANS neurons.

Answer 1

Autonomic: don’t have voluntary control over

nerve: bundles of axons and a blood supply

PNS: motor neurons release Ach on nicotinic receptors at the NMJ.

Pathway from the CNS to the peripheral organ: 1st neuron (preganglionic in the CNS) 
2nd neuron (postganglioni) in the periphery. 

In sympathetic system the ganglion is close to the CNS
In parasympathetic its close to the target organ.

Question 2

2. Specifically identify and name the function of each cranial nerve.

Answer 2

draw them all out for cheating purposes.

Question 3

Identify and understand the organisation of the spinal nerves in relation to levels of the spinal cord.

Answer 3

31 pairs, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal. all voluntary motor function.
all except c1 have sensory fibres.

Question 4

Describe the cranial, thoracic and sacral outflow of ANS nerves.

Answer 4

sympathetic: T1-L2 preganglionics
parasympathetic: cranial nerves iii, vi, ix and sacral 234.

none of the cranial nerves have sympathetic fibres.
- head sympathetic innervation comes from upper thoracic and spinal nerves.

Question 5

Differentiate between the special and general senses.

Answer 5

special senses: 
olfaction:cr 1
vision: cr2
taste: cr 7 and 9 
hearing and balance 8 

general senses: trigeminal 5 and all spinal nerves except c1.
- muscles and proprioception.
somatosensory.

Question 6

Define and classify sensory receptors according to their sensory modality.

Answer 6

Transducers: convert one form of energy into another.
Photoreceptors: light rods and coens
Thermoreceptors: hypothalamus and periphery
Nociceptors: pain
Mechanoreceptors: externoreceptors and proprioceptors.

Question 7

3. Define “Generator Potential (GP), describe the role of a GP in the sensory transduction process and differentiate a GP from an Action Potential.

Answer 7

Membrane depolarized to generate an action potential.
Generator potential depolarizes the peripheral portion of the sensory axon. (always depo except in rods and cones) If GP is big enough to reach threshold, AP will be produced.
AP initated at first node of ranvier. by electrotonic propegation

The GP is like EPSP

• is graded in amplitude,
• does not cause refractory membrane, not actively propegated .

mostly due to the opening/closing of ion channels.

mechanoreceptors have a direct effect on stretch sensitive channels allowing na and k to pass.

nociceptors, photoreceptors and chemoreceptors are g-coupled

Question 8

4. Identify how stimulus intensity is coded by sensory neurons.

Answer 8

frequency coding (nonlinear) 
population coding (more invididual receptors included) 

heavy stim uses both

Question 9

Understand how sensory receptors adapt to stimuli and give examples of receptors with rapidly adapting and slowly adapting properties.

Answer 9

slowly adapting: tonic. maintain stable firing rate, record length and moniter unchanging stimuli. a length has a frequency of firing. (secondary endings of muscle spindle)
Ruffini endings

rapidly adapting (phasic)

• detect changein time (vibration pacinian corpuscle)
• detect change in space (Meissner corpuslce in the skin)

Question 10

Describe the structure and function of pain and temperature

Answer 10

free nerve endings, no capsule or specialization

Question 11

Be able to categorise peripheral nerves discussed in CAPS 301 lectures using two different classification schemes: the A, B, C scheme and the Roman numeral I, II, III and IV scheme.

Answer 11

Conduction velocity
A fast B smaller, C smallest and non mylinated can be alpha and gamma (are both A)

Size
I II III IV
by speed (diameter and myelination) exclusively used for sensory axons.

Question 12

What are the functions of the ANS? How is it coordinated and what are the afferents?

Answer 12

Homeostasis
Life suffport 
BLood pressure
GI motility, 
salt balance sexual function

coordinated via:
reflexes at spinal chord, medulla, hypothalamus, PFC, cerebellum

baroreceptors, osmoreceptors, thermal, cutaneous, pain, stretch

Question 13

What NT are released by autonomic nervous system?

Answer 13

at effetor site: sympathetic releases noepinephrine onto adrenergic receptors
parasymp releases ach onto muscarinic

in brain: ach is released onto both.

ach is onto nicotinic at skeletal things and ganglia but muscarinic on effector tissues

Question 14

what are the effects of parasympathetic and sympathetic ns?

Answer 14

catabolic sympathetic ns: increase HR, sv and BP, increased blood flow, decreased blood flow to skin fight or flight. epinephrine noepinephrine from adrenal medulla

Anabolic parasympatheic
- decreased those things, relazation and there is sometimes paradoxal coactivation.

Question 15

describe the pacinian corpuscle

Answer 15

rapidly adapting sensory neuron with layers of fluid that does mechanical stretch receptors. but after a while the fluid is normal and its adapted. (rapid adaptation in this case)

Question 16

describe the structure and function of receptors

Answer 16

tactile: meissners corpuscles, pacinian corpuscles. rapidly adapting, discriminative touch. (when you put fingers and slide them across something) up and down movement. texture requries movement.

merkels and ruffindi endings

• slowly adapting.
• maintained pressure

proprioception
- muscle spindles (primary and secondary endings) signal change of muscle length and absolute length.

Question 17

Outline the anatomy of the both the exterior and interior of the spinal cord including how the cord differ at different segments of the vertebral column

Answer 17

x shaped grey matter
mostly cell bodies/dendrites.
outerportion is white matter axons (descending and ascending) - divided into dorsal, lateral and ventral.

3 main tracts: dorsal column (touch, proprioception)
lateral spinothalamic (pain and temperature-crossed) 
lateral corticospinal tract (voluntary muscle control) 

Dorsal root of spinal nerve: sensory into to the chord, cell bodies of these sensory neurons in dorsal root ganglia

Ventral root: contains axons of motor neurons, cell bodies in ventral horn grey matter

Ventral horn: larger in cervical and lumbar areas
Dorsal horn: contains sensory neurons
Intermediolateral horm at T1-L2 and S2-S4.

Question 18

Describe the components of a neuronal reflex.

Answer 18

no voluntary command from brain. unchangeable activity in a series of neurons.
REFLEX ARC

Sensory receptor 
Sensory Axon 
Integration in CNS (spine) 
Motor neuron and motor axon 
Effector organ (muscle or gland)

Question 19

Detail the neuronal and non-neuronal components of a muscle spindle.

Answer 19

Detects stretch, within skeletal muscle. contains intrafusal muscle fibres. When it lengthens, increase in APs.

1. nuclear bag (1 per spindle)
2. nuclear chain (several per spindle)

extrafusal: force generating, reflexive
intrafusal: inside extrafusal and sensory

Sensory Innervation: 
1a fibre (bag and chain) primary endings, rapidly adapting signal change in length 
II fibres (only chain) secondary endings slowly adapting signal absolute length 

Motor innervation of intrafusal spindles via gamma motor neurons (chain and bag) , stretches intrafusal fibres by pulling sarcomeres together which increases firing in in I and II fibres.

gamma prevents slack muscle (with alpha coactivation)

Question 20

Compare and contrast the monosynaptic stretch reflex and the polysynaptic flexor-withdrawal reflex in terms of organizational components and function.

Answer 20

MONO: 2 neurons 1 synapse in the spinal chord

• primary endings activated by rapid muscle stretch (knee tap), excite the alpha motor neurons of the same muscle and contract it.
• at the same time (not mono anymore) the antagonist flexor muscles inhibited by an interneurons (reciprocal inhibition which hyperpolarizes the flexor mn

POLY (uses interneurons)
withdraw limb from painful stimulus
pain: activate nociceptors (group III or IV) excite interneuron in the cord, excites flexor motor neurons (also receiprocal inbitition to inhibit extensor muscles)
This withdraws foot.
may also cause crossed extensor reflex causing opposite leg to contract and move away from it. (same muscles used when voluntary control)

Question 21

Outline how the body generates muscle tone using information from muscle spindles

Answer 21

Background contraction even when no movement, via gamma motor neurons. activating reticulospinal nerves from reticular formation and constantly stretches the spindle (GROUP II FIBRES: nonchanging length) to create elasticity and power for when the extrafusal muscle wants to fire. constant exitation of alpha motor neurons.