midsem prep

Question 1

what are the 3 stages in the nociceptive pathways

Answer 1

1 - afferent neurons
2 - projection neurons (from doral horn to medulla, pons, midbrain, thalamus, hypothalamus
3. - supraspinal neurones - project from spinal neurons to subcortical and cortical areas where pain is percieved

Question 2

what stages of nociception do we want to block under general anaesthesia

Answer 2

3rd stage (perception)

Question 3

In the first stage of pain perception, what neurotransmitters are coreleased?

Answer 3

amino acids (glutamate, aspartate)
neuropeptides (substance P, neurokinin, CGRP)

Question 4

in the second stage of pain perception what neurotransmitters are released?

Answer 4

glutamate, this is the major transmitter in the thalamus, and the 2nd stage is occurring in the spinothalamic tract, crossing the midline and communicating with different nuclei in the thalamus

Question 5

What is the antinocicpetive pathway?

Answer 5

This is a descending pain pathway that modulates nociceptive input at the supraspinal and spinal levels. It starts in the supraspinal level and finishes in the dorsal horn.

Question 6

what regions of the CNS are involved in the antinociceptive pathway?

Answer 6

the periaqueductal gray, the locus ceruleus and the nucleus raphe magnus

Question 7

What neurotransmitters are involved in the antinociceptive pathways in the dorsal horn?

Answer 7

seratonin (raphe magnus)
norepinephrine (locus ceruleus)
endogenous opiods

Question 8

What is peripheral sensitisation?

Answer 8

this is a sensitising soup of chemical mediators brought about by the inflammatory response. (bradykinin, histamine, seratonin, macrophages). its good because it can promote healing

Question 9

what is central sensitisation?

Answer 9

this is an indirect consequence of tissue trauma and inflammation, and means there is a constant activation of NMDA peripheral receptos increasing excitabilty of cells to both nociceptive (hyperalgesic) and non-nocicpetive allodynia stimuli .

Question 10

where anatomicallly is the sympathetic nervous system?

Answer 10

it originates in the lateral to intermediate horn of spinal cord segments C8 to L3/L4. efferent fibres leave the spinal cord in the ventral root to the proper spinal nerve and the ramus communicans leaves the proper spinal nerve and the sympathetic trunk.
Splanchic nerves supply the abdomen
fibres from c8-t7 ascend to supply the head
vagosympathetic trunk is located in the carotid sheath of the neck
ganglia: middle cerical ganglion at throacic inlet and cervicothoracic ganglion and cranial cervical ganglion (deep to the tympanic bulla)
SYMPATHETIC FIBRES LIKE TO TRAVEL IN ASSOCIATION WITH THE ARTERIES

Question 11

Describe the anatomy of the parasmpathetic nervous system

Answer 11

the head is supplied by parasympathetic nuclei of nerves 3, 7 and 9 (7 and 9 do parasympathetic supply to the salivary glands with their nuclei in the myelencephalon)
vagus (10) has parasympathetic gangion to pharynx, larynx, thorax, abdomen. Bear in mind that the enteric NS can functon alone. (submucosal and myenteric plexus).
THe caudal end of the body is supplied by the sacral spinal cord (s1-s3) and continues as the pelvic nerves joining the pelvic plexus.

Question 12

what are the three thin tunics in the eye?

Answer 12

outer fibrous tunic - made of dense collagenous tissue, it resists internal pressure and consists of scleral and cornea (anteriorly) meeting at the limbus)
middle vascular tunic
internal nervous tunic

Question 13

what does the sclera do?

Answer 13

its opaque, penetrated by fibres of optic nerve where it attaches to the tendons of the extinsic muscles of the eye and is continuous with the dura mater of the optic nerve

Question 14

what does the cornea do?

Answer 14

its a specialised trasparent connective tissue, with very organised collagenic layers and continuous pumping of intersititual fluid out by posterior epithelium. it is nourished by the lacrimal fluid and is very sensitive due to nerve endings.

Question 15

what does the vascular tunic do?

Answer 15

it has the choroid, ciliary body and iris. anchors zonular fibres, lines sclera, has blood vessels in its pigmented connective tissue and contains avascular tapetum lucidum.
THe iris is a ring of tissue. it is made of pigmented connective tissue and there is specie variation when it is constricted

Question 16

What is the internal tunic of the eye?

Answer 16

this is the retina.
it contains photoreceptor rods and cones, as well as horizontal cells, bipolar cells, amacrine cells and ganglion cells. ganglion cells are the most anterior, they synapse with bipolar cells which synapse with photoreceptors.

Question 17

what is the role of the lens, aqueous humour and vitreous body?

Answer 17

lens - focus image on retina
aqueous humour - fills space between cornea and lens and has posterior and anterior bodies
vitreous body - occupies space between lens and retina. a gel like mass consisting of stroma of fine transparent fibres filled with glycosaminoglycans and water.

Question 18

what are the extrinsic muscles of the eyeball?

Answer 18

there are 7, all insert on fibrous tunic
dorsal, ventral, lateral and medial rectus muscles
dorsal oblique - innervated by trochlea nerve as its tendon passes through the trochlea
the ventral oblique
retractor bulbi (retracts eyeball, not in humans)
levator palpebrae superioris

Question 19

what are the 3 secretions from the eyelids

Answer 19

tarsal gland - fatty material
mucoid layer - from goblet cells in conjunctiva
aqueous layer - from lacrimal gland

Question 20

what nerves innervate what in the eye?

Answer 20

OPTIC - perception of light
oculomotor - muscles
trochlea - dorsal oblique
5 - sensory to eyeball
abducens - lateral rectus, retractor bulbi
sympathetic innervation is via the cranial thoracic spinal cord and ascends in vagosympathetic trunk to cranial cervical ganglion near tympanic bulla.

Question 21

what systems are working in the continence and urine storage function of bladder control? what muscles are innervated by what nerves?

Answer 21

the detrusor muscle is relaxed to allow filling
the external sphincter striated muscle
GVA neurons tell cerebral cortex
this is all the sympathetic system. 
parasympathetic outputs are inhibited

Question 22

What systems are working in the voiding phase?

Answer 22

parasymathetic
detrusor muscle is contracted (hypogastric nerve)
relaxation of the interan and external urinary sphincters (pudendal nerves)

Question 23

What is a lower motor neuron bladder?

Answer 23

distended bladder with little tone and dribbling with the only resistance being from the internal urethral sphincter. it results from lesions in the pudendal nerve, sacral spinal nerves, pelvic nerves and sacral plexus

Question 24

what is an upper motor neuron bladder?

Answer 24

more common. occurs with sever spinal cord compressive lesions. signs include lack of voluntary urination, distended turgid bladder and some leakage, with occasional reflex emptying.

Question 25

what are the 5 classes of sedatives used in veterinary medicine?

Answer 25

opiod analgesics
alpha 2 adrenergic agonists
phenothiazine derivatives
benzodiazepines
butyrophenones

Question 26

What is the mechanism of action of the alpha 2 adrenergic agonists and what side effects may they cause?

Answer 26

MOA - locus coeruleus - sedation. CVS in medulla, analgesia in spinal cord, also autonomic ganglia. there is an inhibition of noradrenaline release and a contraction of vascular smooth muscle. Cause emesis in cats too! and muscle relaxation in cows and horses. increse blood pressure initially due an a hypertension followed by a reflex bradycardia leading to a hypotensio. this cause muddy mucous memebranse and reduced coronary perfusion. also causes hyperglycaemia due to inhibiting insulin, inhibits lipolysis, inhibits renin and temp reg. an example is xylazine. this class of drug can be reversed.

Question 27

WHat is the mechanism of action of phenothiazine derivatives and side effects?

Answer 27

eg. acepromazine. these block dopamine receptors, which causes catalepsy and blocks emesis. it also has a peripheral alpha adrenoreceptor blocking function. its also antimuscarinic and antihistaminic but has NO ANALGESIC properties. its often used as a premed, but causes decreased PCV and hypotension, so is contraindicated in shocked or colicky animals. becasue youre blocking the peripheral alpha adrenoreceptors they dilate and you get pooling of blood.

Question 28

What is the mechanism of action of benzodiazepines?

Answer 28

these have allosteric action on the GABA receptor, with little CVS effect. they cause skeletal relaxation. stimulates appetite in cats. anticonvulsant. dependance potential more important in human medicine

Question 29

what features make up the external ear?

Answer 29

pinna, external acoustic meatus, tympanic membrane,

Question 30

what features make up the middle ear?

Answer 30

tympanic cavity, auditory ossicles

Question 31

what is the function of the tympanic cavity?

Answer 31

it changes air vibrations (sound waves) into mechanical movement trhough the auditory ossicles, and is expanded ventrally within the tympanic bulla.

Question 32

What are the 3 bones of the middle ear? (auditory ossicles)

Answer 32

melleus, incus and stapes

Question 33

What muscles move the bones of the inner ear?

Answer 33

tensor tympani and m. stapedius, dampening transimittions. vovement is transmitted to the vestibular window of the inner ear which ha s fluid that can be moved

Question 34

What are the components of the inner ear?

Answer 34

There are 2 labyrinths:
MEMBRANOUS: utricle and saccule, semicircular ducts, cochlear ducts. Contains endolypmph and is surrounded by perilymph
BONY: vestibule, semicircular canals, cochlea

Question 35

What is the function of the vestibular system?

Answer 35

this is composed the utricle and saccule and semicircular ducts and is responsible for sensing body position. THe hair cells have 40-80 cilia and one kinocilium. cilia towards kino - depolarisation. other way - hyperpolarisation. this causes excitation or inhibiton of fibring of the neuron at the base of the hair cell.
THe utricle and saccule are two membranous components, and they sense static postition through the maculae. The macula in the saccule are oriented vertically and those in the utricle are horizontally.

Question 36

How do the semicircular ducts sense position

Answer 36

there are 3 in each ear, they are located at right angles to each other. Each duct has an ampulla at one end, this is a sensory enlargement and has a sensory region (crista). they sense dynamic position of head due to movement of head, and the hair cells project into cupula, which is readily deflected by movement of endolymph.

Question 37

How does the cochlea transmit sound?

Answer 37

it has 2 canals - the dorsal scala vestibuli and the ventral scala tympani. communicate with each other at blind apical end of spiral canal. the waves created from the vibration of stapes moving perilymph vibrates the basilar membrane, which distorts hair cell cilia resting against the tectorial membrane and depolarises hair cells, creating impulse in the cochlear nerve. Waves ascend the spiral in the s.v and descend in the s.t

Question 38

what is the innervation of the ear?

Answer 38

CN8, CN7, CN5 (m. tensor tympani.)

Question 39

what are the external, middle and inner ear derived from?

Answer 39

external - ectoderm and underlying mesenchyme of first pharyngeal cleft
middle - endoderm of first pharyngeal pouch and surrounding mesenchyme
inner ear - derived from ectoderm lateral to hindbrain

Question 40

name the sequence of events in neurulation:

Answer 40

notochord formation (jhead, nervous system, somite)
ectodermal thickens above to form neural plate
neural plate bound by elevations called neural folds
neural plate depressed in midline - neural groove
neural fold is more elevated, folds converge towrds midline, meet, fuse.
final fusion froms neural tube, which is now separated from the surface ectodem.