neuro overview

what structure does the pudendal nerve provide

• somatic motor innervation

• somatic sensory innervation

• the anal sphincter

• the perineal skin

where does the pudendal nerve convey parasympathetic fibres from and to

sacral spinal cord to rectal smooth muscle

what is another thing that the pudendal parasympathetic division controls

urinary bladder contraction

what nerve is responsible for hamstring, distal limb muscle and cutaneous innervation below the stifle

the sciatic nerve

what is the largest foramen and what major structures pass through

foramen magnum

• the spinal cord into the cranial cavity where it becomes continuous with the lower end of the medulla oblongata

• vertebral arteries

• anterior and posterior spinal arteries

• spinal roots of the accessory nerve

3 foramina and nerves that exit through

• foramen ovale: mandibular nerve

• jugular foramen: glossopharyngeal nerve, vagus nerve, accessory nerve

• foramen rotundum: maxillary nerve

a) Name two important structures that pass through the intervertebral spaces and foramina?

The articulation of the skull and the Atlas (the atlanto-occipital joint) creates a large space on the dorsal aspect. Identify this space. b) What might be the clinical significance of this space?

• craniocervical junction

• protets the structures transitioning from the skull to the spinal column

  • foramen magnum is a critical passage point

• conduit for major blood vessels supplying the brain eg the vertebral arteires

white and grey matter of the brain

• grey matter consists of neuronal cell bodies and dendrites and synpases and glial cells

• white matter is myelinated axons

Identify and name the tough membrane that covers the outer surface of the brain.

dura mater

Name the other two layers of membranes that cover the brain.

• arachnoid mater

• pia mater

Briefly explain why the two membranes you have named in (b) above are not discernible over the brain surface.

what are the elevations and depressions on the brain called

gyri and sulci

How far caudally does the spinal cord extend in the vertebral column? Use the vertebrae number (e.g. C1, T1 etc.) as a marker.

L2

here are two areas of the spinal cord where it briefly thickens, known as the intumescences. They correspond to the regions of the forelimb and hindlimb, respectively. b) What is the likely reason for these swellings?

Describe how the spinal cord terminates at its most caudal end.

• where does it travel inferiorly within

• what is it surrounded by

• where does it taper off and what does it form

• what do the spinal nerves form

• it travels inferiorly within the vertebral canal surrounded by spinal meninges containing csf

• at the l2 vertebrae level the spinal cord tapers off forming the conus medullaris

• the spinal nerves that arise from the end of the spinal cord are bundled together forming the cauda equina

What does the DRG consist of?

a collection of neuronal cell bodies of sensory neurons

How does the location of the dura mater in the vertebral column compare to that of the cranium?

• cranial dura mater

  • consist of an outer periosteal layer and an inner meningeal dura

  • periosteal is closely attached to the internal surface of skull bones

  • meningeal is continuous with the dura of the spinal cord

  • periosteal and meningeal are tightlly fused together except for where they separate to for the dural ventral sinuses

• spinal

  • only one layer

  • not closely integrated with the overlying bones

  • there is an epidural space

Some cranial nerves travel away from the cranium to innervate structures far away from the head. In pot 361, observe the nerve passing down the neck all the way to the thorax. The same nerve can be viewed in the additional pots and laminates, running very close to the base of the heart. i) Identify this cranial nerve

What is the effect of stimulation of this nerve on the heart?

What is the effect of stimulation of this nerve on the intestines?

Which part of the brain connects directly to the neurons projecting the nasal cavity?

olfactory bulb

what are the 4 main nerves supplying the canine forelimb?

• radial nerve

• musculocutaneous nerve

• median nerve

• ulnar nerve

which nrve passes down the neck to the thorax and runs close to the base of the heart?

• what type of nerve is it

• is it afferent or efferent

• effect on heart rate

• effect on the intestines

vagus nerve

• mainly parasympathetic autonomic

• both afferent and efferent

• slow heart rate

• increases intestinal activity

what are the major cell types found in the retina

• rods and cones

• retinal ganglion cells: transmit info from the rods and cones to the brain, a bundle forms the optic nerve

list all special sense organs

• nose- olfaction

• vomeronasal organ- phermomone detection

• tongue- taste

• eye- vision

• ear- hearing and balance

olfaction

• which cells detect

• what contain the sensory receptors

• which type of neurone and where do they pass through and through which structure

• what is the epithelium held by and what do they secrete

• detected by special cells in muscosa of nasal cavity

• mucose= olfactory epithelium, contain sensory receptors

• neurons (bipolar) pass through epithelial surface to olfactory bulb in cranium after passing through bony cribiform plate (separate cranial cavity from nasal cavity)

• cribiform plate has small pores

• olfactory epithelium held by supporting cells that secrete lipid rich mucus, odorants dissolve in this fliod and reach the sensory receptors

• signal tranduction takes place through neurons

vomeronasal organ

• where is it found

• what do ducts link

• what type of structure are they

• found on the floor of the nasal cavity

• ducts link nasal and oral cavities caudal to incisor teeth

• are blind ending caudal sacs

• flehmen reaction- pump air in and out (sexual and social behaviour)

• aroma is the combined effect of neural inputs from the sense o smell and taste

gustation

• where are gustatory receptors found

• features of the receptor cells

• where do gustatory inputs link directly to

• gustatory receptors found on the tongue mucosa

• sensory neurons carry info to the brain

• receptor cells have one single receptor type so each receptor can only detect one form of taste

• gustatory inputs link directly to centres involving ingestion, food avoidance, insulin release, diuresis when water in pharynx

vision

• what conducts light and what does this stimulate

• what substance fills the eye

• what is the sclera and what structure is it continuous with

• eye has transparent media that conducts light to stimulate photoreceptor cells

• vitreous humor is gel like substance filling the eye

• sclera is a tough connective tissue to maintain integrity and strength- continuous with membrane covering the brain.

ear

• outer middle and inner

the eye

• what are the 3 layers

• how is the light signal transmitted

• what protein is present in rods and cones and what does it trigger through what and where is it transmitted

Transparent media- Cornea, aqueous humour, lens and vitreous humour direct and converge light on the photoreceptor cells on the retina

Non-Transparent media- Choroid, Uvea, Sclera- Support transparent media

The photosensitive layer - retina made up of rod and cones receptor cells. Cones for daylight vision and rods for night vision.

Light splits chemical compound -Rhodopsin in cones and rods and triggers signal transduction thru optic nerve. The signals are transmitted to the optic cortex of the brain.

outer ear

sound collected from external auditory canal to the tympanic canal and tympanic membrane

middle ear

including what structure it is connected to

maleus, incus and stapes conducts sound to oval window. also connected to eustachian tube to the nasopharynx

inner ear

oval window transmits waves to the cochlea which contain sensory receptor cells known as hair cells from where signals are transmitted to the brain via CN VIII

Ear- balance and motion

• what structure detects angular movement

• what detects linear acceleration

• inner ear has semicircular canals that detect angular movement while the saccule and utricle (maculae) detect linear acceleration

cochlea

• what structures are located in the cochlea

• what causes a standing wave to travel in cochlea canals

• what does this cause

• basilar membrane

• organ of corti

• hair cells

• CN VIII

• fluid movement in the cochlea caused by sound vibration on the oval window cause a standing wave to travel in cochlea canals.

• so hair cells on basilar membrane bends against tectorial membrane

• then signals are generated and sent to the brain

• hair cells bend due to fluid movement and discharge electrical signals to the brain

semi circular canal

• function

• innervation

• cupula

• hair cell

• CN III

• hair cells of the cupula bend due to fluid movement in the semicircular canals and discharge electrical signals to the brain

saccule and utricle

• what does it detect

• what angles are they at

• detection of linear acceleration

• hair cells

• CN VIII

• hair cells (otoliths) bend due to fluid movement caused by inertia in the saccule and utricle causing them to discharge electrical signals to the brain

• two are in right angles to each other so can only detect linear movement in one plane

components of the somatic nervous system

• nerves

• what is incoming information coordinated by

(voluntary control)

afferent nerves- reception of internal and external stimuli

incoming info coordinated by spinal cord, somatomotor cortex and cerebellum

efferent transmit impulses from cns to skeletal muscles

components involved in the somatic

joints, skin, skeletal muscle, somatosensory fibers, somatomotor fibers

signal transduction route- sensory division

• sensory inputs to SC and brain

• SC initiate voluntary motor control

• SC also sends info to brain to initiate voluntary motor control

• SC and brain sends response to contract muscle

signal transduction route- motor division

• spinal cord initiates response via lower motor neurons or upper motor neurons of the somatomotor cortex and brain stem pathways make contact with spinal lower neurons

• somatomotor cortex initiate voluntary movement and modulate muscle/reflex activity

patella reflex

1. tap/bend the patella tendon

2. stretch receptors in muscle simulated

3. sensory neuron in muscle send signal spinal cord

4. spinal cord detects signal and sends response

5. motor neuron carry response to muscle from spinal cord

6. quads muscle contracts

meisnyer corpuscles

skin light touch

merkers disk

skin touch and texture

pacinian corpuscle

pain and deep pressure

ruffini corpuscle

stretch / kinesthesia

free nerveending

pain

components

parasympathetic, sympathetic, enteric

target tissues

cardiac, smooth, glandular tissue

what is the ans involved in

• percieved sensation

• involuntary inhibition or excitation of visceral and glandular tissue

• homeostasis

• complements the endocrine system

components of the ans

• general visceral efferent motor neurons- visceromotor fibres- target tissues

• general visceral afferent sensory neurons- enteroreceptors (chemoreceptors, baroreceptors)- viscero sensory fibres. Sensory fibres coveyed from the periphery to the cns via cranial nerves and somatic spinal nerves

• central integration centres (brain)- hypothalamus, brain stem (pons, medulla)

anatomy of the ans

• 2 types of neurons

2 neuron system in the periphery

1. pre-ganglionic neuron- cell body in brain or spinal cord

2. post-ganglionic neuron-cell body lies outside cns in autonomic ganglia

which is parasympathetic and sympathetic from craniosacral outflow and thoracolumbar outflow

• craniosacral- parasympathetic

• thoracolumbar- sympathetic

parasympathetic

• cranial parasympathetic outflow via which nerves

• sacral outflow via which nerves

• cranial parasympathetic outflow via:

• cranial nerves III, VII, IX AND X

• to visceral and glandular tissues of the head

• CN X - vagus nerve

• heart

• most of the GIT

• sacral outflow (S1-S3)

• caudal GIT

• urinary tract

• reproductive organs

sympathetic

• which spinal nerves to thoracolumnar outflow

• to head and neck via which spinal nerves

• thoracolumbar outflow via

• spinal nerves T1 to L4

• via sympathetic chain

• to head and neck T1-T3

• to organs of thorax abdomen and pelvis

• disributed via several peripheral ganglia

autonomic vs somatic motor neurons

autonomic

• pre and post ganglionic

• myelinated presynaptic and unmyelinatd post synaptic

• can be ach or nad

somatic

• one neuron only

• always excitatory

vagosympathetic tract what does it contain

parasympathetic traveling caudal direction and

sympathetic traveling cranial in neck

clinical significance of the vagosympathetic trunk

runs within the carotid sheath deep to to the jugular groove

vulnerable to needle stick injuries

control centres of autonomic

brainstem and hypothalamus