midsem prep Flashcards
what are the 3 stages in the nociceptive pathways
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
what stages of nociception do we want to block under general anaesthesia
3rd stage (perception)
In the first stage of pain perception, what neurotransmitters are coreleased?
amino acids (glutamate, aspartate) neuropeptides (substance P, neurokinin, CGRP)
in the second stage of pain perception what neurotransmitters are released?
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
What is the antinocicpetive pathway?
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.
what regions of the CNS are involved in the antinociceptive pathway?
the periaqueductal gray, the locus ceruleus and the nucleus raphe magnus
What neurotransmitters are involved in the antinociceptive pathways in the dorsal horn?
seratonin (raphe magnus)
norepinephrine (locus ceruleus)
endogenous opiods
What is peripheral sensitisation?
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
what is central sensitisation?
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 .
where anatomicallly is the sympathetic nervous system?
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
Describe the anatomy of the parasmpathetic nervous system
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.
what are the three thin tunics in the eye?
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
what does the sclera do?
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
what does the cornea do?
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.
what does the vascular tunic do?
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
What is the internal tunic of the eye?
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.
what is the role of the lens, aqueous humour and vitreous body?
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.
what are the extrinsic muscles of the eyeball?
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
what are the 3 secretions from the eyelids
tarsal gland - fatty material
mucoid layer - from goblet cells in conjunctiva
aqueous layer - from lacrimal gland
what nerves innervate what in the eye?
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.
what systems are working in the continence and urine storage function of bladder control? what muscles are innervated by what nerves?
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
What systems are working in the voiding phase?
parasymathetic
detrusor muscle is contracted (hypogastric nerve)
relaxation of the interan and external urinary sphincters (pudendal nerves)
What is a lower motor neuron bladder?
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
what is an upper motor neuron bladder?
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.
what are the 5 classes of sedatives used in veterinary medicine?
opiod analgesics alpha 2 adrenergic agonists phenothiazine derivatives benzodiazepines butyrophenones
What is the mechanism of action of the alpha 2 adrenergic agonists and what side effects may they cause?
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.
WHat is the mechanism of action of phenothiazine derivatives and side effects?
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.
What is the mechanism of action of benzodiazepines?
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
what features make up the external ear?
pinna, external acoustic meatus, tympanic membrane,
what features make up the middle ear?
tympanic cavity, auditory ossicles
what is the function of the tympanic cavity?
it changes air vibrations (sound waves) into mechanical movement trhough the auditory ossicles, and is expanded ventrally within the tympanic bulla.
What are the 3 bones of the middle ear? (auditory ossicles)
melleus, incus and stapes
What muscles move the bones of the inner ear?
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
What are the components of the inner ear?
There are 2 labyrinths:
MEMBRANOUS: utricle and saccule, semicircular ducts, cochlear ducts. Contains endolypmph and is surrounded by perilymph
BONY: vestibule, semicircular canals, cochlea
What is the function of the vestibular system?
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.
How do the semicircular ducts sense position
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.
How does the cochlea transmit sound?
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
what is the innervation of the ear?
CN8, CN7, CN5 (m. tensor tympani.)
what are the external, middle and inner ear derived from?
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
name the sequence of events in neurulation:
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.
