*Anatomy - Nervous system Flashcards
What are the 2 anatomical divisions of the nervous system?
CNS (brain, spinal cord)
PNS (all tissues not within the spinal cord)
What type of nerves do you get within the PNS? (3)
Spinal nerves (connect with the spinal cord) Cranial nerves (connect with the brain) Autonomic nerves (control organs, smooth muscles, glands, can be visceral afferents, sympathetic nerves or parasympathetic nerves)
What type of autonomic nerves do you get? (3)
Visceral afferents
Sympathetic nerves
Parasympathetic nerves
Parts of a neurone? (4) + function
Dendrites (receive and conduct info towards cell body)
Body (processes information)
Myelin sheath (insulates nerve fibre helping signal travel quicker)
Axon (or nerve fibre - conduct signal away from cell body)
What is a collection of nerve cell bodies called in the:
CNS?
PNS?
CNS= nucleus PNS= ganglion
What are bundles of axons called in the:
CNS?
PNS?
CNS = tract PNS = nerve
What are nerves?
Bundles of axons (nerve fibres) wrapped in connective tissue which are travelling to or from the same region
What can bundles of axons leave a nerve as?
Branches
What is a synapse?
What happens at the synapse?
The region where one neurone communicates with another neurone in a ganglion in the PNS or in a nucleus in the CNS
An electrical signal (AP) becomes a chemical signal (neurotransmitter) then an electrical signal again
What are the 3 main parts of the brain?
The cerebrum
The cerebellum
Brain stem
What are the 4 main lobes of the cerebrum?
Frontal
Temporal
Parietal
Occipital
What is the outer layer of the cerebrum called?
Cerebral neocortex (cortex)
What are the 2 halves of the cerebrum called?
Right and left cerebral hemisphere
What does the cerebral neocortex consist of on its surface and what are these?
Gyrus (pl. gyri) = ridges
Sulcus (sulci) = dips
What are the 2 layers of cerebrum in the brain and what does each section contain?
Grey matter (cerebral cortex) = outermost layer full of cell bodies) White matter = deep to grey matter, contains many myelinated axons giving the white appearance
What is the order of matter in the spinal cord?
white matter is superficial
Grey matter is deep
Name of the 12 cranial nerves?
I = olfactory nerve II = optic nerve III = oculomotor nerve IV = trochlear nerve V = trigeminal nerve VI = abducent nerve VII = facial nerve VIII = vestibulocochlear nerve IX = glossopharyngeal nerve X = vagus nerve XI = spinal accessory nerve XII = hypoglossal nerve
From anterior to posterior, in which order do the cranial nerves attach to the brain?
CN I - XII
except CN XII is between CN IX and CN X
Name of the 3 fossae of the cranial cavity?
Anterior cranial fossa
Middle cranial fossa
Posterior cranial fossa
Which cranial nerve passes through the cribriform plate of the ethmoid bone?
CN I
What CN passes through the optic canal?
CN II
What cranial nerves pass through the superior orbital fissure?
CN III, IV, V1 (ophthalmic nerve) and VI
What cranial nerve passes through foramen rotundum?
CN V2 (maxillary nerve)
What nerve passes through foramen ovale?
CN V3 (mandibular nerve)
What CNs pass through the internal acoustic meatus?
CN VII and VIII
What nerves pass through jugular foramen?
CN IX, X and XI
What nerve passes through the hypoglossal canal?
CN XII
Look at position of foraminae on diagram
…
What foraminae does the spinal cord pass through?
The foramen magnum
What are the 3 parts of the course of a CN?
CNS part
Intracranial part
Extracranial part
What protects the spinal cord?
The vertebral canal
What are the 4 segments of the vertebral canal?
Cervical
Thoracic
Lumbar
Sacral/ coccygeal
what are the enlargements of the spinal cord?
What causes these?
Cervical
Lumbosacral
The limbs
What connects bilaterally to the spinal cord?
Spinal nerves
At what intervertebral disc level does the spinal cord end?
L1/L2
What is the tapered lower end of the spinal cord called which usually occurs around L1/L2 IV disc level?
Conus medullaris
What is a nerve root?
The base of a nerve as it branches off the spine or brain
why is the vertebral column longer than the spinal cord?
Lumbar and sacral spinal nerves have to descend in the vertebral canal to their respective intervertebral foraminae
How many pairs of spinal nerves are there?
31
How many pairs of each of the types of spinal nerves are there and what are their names?
8 cervical spinal nerves (C1 - C8) 12 thoracic spinal nerves (T1-T12) 5 lumbar spinal nerves (L1-L5) 5 sacral spinal nerves (S1-S5) 1 coccygeal spinal nerve (Co)
How many vertebrae are there?
33
How many of each type of vertebrae are there?
7 cervical 12 thoracic 5 lumbar 5 sacral (fused to form 1 sacrum) 4 coccygeal (fused to form 1 coccyx)
How are spinal nerves named?
According to the vertebrae above them except in the cervical region, where they are named according to the vertebrae below it
Where does C8 spinal nerve exit
C7 and T1
What spinal nerves supply?
The soma (body wall) (as well as other things)
Where are spinal nerves located?
Only within the intervertebral foramina
How do spinal nerves connect with the structures of the soma?
Via rami
How do the spinal nerves connect with the spinal cord?
Via roots and rootlets
What are the names of the rootlets on the right hand side?
Right anterior rootlets
Right posterior rootlets
How does the posterior rami and anterior rami compare?
Posterior rami is smaller and supplies the posterior body wall,
Anterior rami is larger and supplies the anterolateral body wall
What is the swelling of the posterior root called?
Posterior/ dorsal root ganglion (collection of nerve cell bodies)
What does each pair of spinal nerves supply?
One strip of the soma
Posterior rami = posterior paramedian strip
Anterior rami = supplies the remainder of the posterior part of the strip, the lateral and the anterior parts of the strip
What map is used to describe the segments of the body wall divided by what spinal nerves they are supplied by?
Dermatome/ foerster map
What are dermatomes?
Areas (strips) of skin supplied by bot the anterior and posterior rami of a spinal nerve
What dermatome is the male nipple in?
T4 dermatome
What dermatome is the umbilicus in?
T10 dermatome
What are plexuses?
Networks of intertwined anterior rami (causes less predictable shapes of the limb segments)
4 nerve plexus?
Cervical plexus
Brachial plexus
Lumbar plexus
Sacral plexus
What forms the cervical plexus?
What does this innervate? (3)
C1-C4 anterior rami
Supplies posterior scapl, neck wall and diaphragm
What forms the brachial plexus?
What does this innervate?
C5-T1 anterior rami
Upper limb
What forms the lumbar plexus?
What does this innervate
L1-L4 anterior rami
Lower limb
What forms the sacral plexus?
What does this innervate? (3)
L5-S4 anterior rami
Lower limb, gluteal region and perineum
What are the 5 named nerves which result from the anterior plexus?
Axillary nerve Median nerve Musculocutaneous nerve Radial nerve Ulnar nerve
How do sympathetics travel from the brain to supply organs and sweat glands, arrestor muscles and arterioles?
Originate from autonomic centres in the brain
Pass down the spinal cord
Exit spinal cord with T1-L2 spinal nerves
Travel to the sympathetic chains running the length of the vertebral column
Pass into all spinal nerves (anterior and posterior rami) to supply sweat glands, arrestor muscles and arterioles
“hitch a ride” with arteries to all head and neck organs and skin
Pass into splanchnic nerves to eventually supply organs
What segments of the spinal cord have lateral horns?
T1 to L2 (for cell bodies of the next sympathetic neurones in the chain)
What happens to sympathetic axons that descend from the brain?
They descend in the spinal cord lateral grey column
The sympaethic axon leaves in anterior rootlets/ root
Sympathetic axons then run within the spinal nerve anterior and posterior rami)
Sympathetics also travel within the sympathetic trunk (runs parallel to the vertebral column - has a paravertebral ganglion)
Where do parasympathetic axons leave the CNS via?
Via cranial nerves III, VII, IX and X and via sacral spinal nerves
What type of outflow is the parasympathetic outflow?
Craniosacral outflow
What do parasympathetic ganglia in the head supply?
Lacrimal gland and salivary glands
What does the vagus nerve supply? (CN X)
Organs of the neck, chest and abdomen as far as the mid-gut
What does the sacral spinal nerves supply?
They carry parasympathetic axons to the hindgut, pelvis and perineum
What are the 2 functional subdivisions of the peripheral nervous system?
Somatic nervous system
Autonomic nervous system
What parts of the body does the somatic nervous system supply?
The soma (body wall) - external environment Head and neck, chest walls, back, diaphragm (internal wall), abdominal wall, pelvic wall, limbs Structures = skin, fascia, skeletal muscle, skeleton, internal lining of body cavities
What is the other name for the autonomic nervous system?
Visceral motor system (internal environment)
What structures does the autonomic nervous system control?
Where are these structures located?
Organs
Glands (mucous,sweat, salivary)
Smooth and cardiac muscle
External lining layer of organs
Located = internal organs in chest, pelvic and abdominal cavity
Body wall organs (Sweat glands, arrestor smooth muscles, arterioles)
What does efferent mean?
Motor = action potential towards body wall, body cavity or organ
What does afferent mean?
Sensory = action potential towards the brain
What are the further subdivisions of the somatic nervous system?
Sensory (afferent)
Motor (efferent)
What are the 6 main types of neurones?
Somatic sensory Somatic motor Visceral afferent Sympathetic Parasympathetic Special sensory
What type of neurone provides sensory innervation to the soma?
Somatic sensory
What type of neurones provides motor innervation to the soma?
Somatic motor
What type of innervation provides sensory innervation to the organs (including arterioles, sweat glands, etc.)
Visceral afferents
What type of neurones provides motor innervation to the organs (including the body wall organs)?
Sympathetic
Parasympathetic
What type of neurones provides sensory innervation to the special sense organs?
Special sensory
What types of neurones provides motor innervation to the special sense organs?
Sympathetic
Parasympathetic
In a neve, are the nerve fibres all usually of the same modality e.g. somatic motor, or do they tend to be mixed?
Mixed e.g. somatic motor, somatic sensory and sympatehtic all together in one nerve
Which cranial nerves are special sensory?
CN I, II and VIII
which cranial nerves are somatic motor?
CN IV, VI XI and XII
Which cranial nerves are mixed?
CN III, V, VII, IX and X
What 4 things do mechanoreceptors sense (somatic sensory)?
Coarse touchy
Fine touch
Vibration
Proprioception
What thermoreceptors (somatic sensory) sense?
Temperature
What doe nociceptors sense? (somatic sensory)
Pain (sharp, stabbing, well localised)
How does somatic sensation work e.g. if somatic sensory mechanorecepors in right L2 dermatome are stimulated?
Mechanoreceptors stimulated
APs conducted along axons within the L2 anterior ramus (no posterior rami in limbs)
L2 axons weave their way through the lumbar plexus to the L2 spinal nerve
APs are conducted by the same axons and pass through the dorsal ganglion, poster roots and posterior rootlets
PAS arrive at the posterior horn of the L2 spinal cord segment
APs synapse in posterior horn to the 2nd sensory neurone
APs cross over the midline and then ascend towards the thalamus and cerebral cortex
Sensory APs synapse onto a 3rd neurone in the thalamus
Finally arrive at a location in the left cerebral cortex, specific to the part of the right body wall stimulated
3 horns of the spinal cord and their function?
Anterior horn = motor
Lateral horn = sympathetic
Posterior horn = sensory
Where is the left primary somatosensory area?
What is the purpose of this?
In the left parietal lobe
Sensory APs arrive here from the right side of the body wall
Sensations are brought into consciousness here
What does sensory homunculus show?
The areas of primary somatosensory part of cerebral cortex where sensations from each body wall structure reach consciousness
Size indicates sensitivity of the body part
Where is the left primary somatomotor area located?
In the left frontal lobe
What is the function of the primary somatomotor area?
Motor APs originate
Plan a movement
Contract a right sided skeletal muscle to make movement
How does APs from the left primary somatomotor area cause skeletal muscles in the lower limb to contract?
Somatic motor axons from let cerebral cortex cross over in brainstem then descend to the right anterior horn
APs conducted along axons within anterior rootlets, then anterior roots, then into spinal nerves
APs conducted along axons in right named nerves of right lumbar plexus
synapse onto skeletal muscle of right lower limb
Muscle contracts
What does spinal reflexes miss out that makes them extremely rapid?
Miss out pathway to the brain
Are the following neurones on the opposite or same side as the movement:
Upper motor neurone?
Lower motor neurone?
Upper motor neurone = opposite side (axons cross over at brainstem)
Lower = same side (connect to skeletal muscle)
In terms of neurones, what does a paralysed muscle lack?
What does this mean in terms of function?
What will be seen on examination?
A functioning lower motor neurone
Paralysed muscle cannot contract
Reduced muscle tone
In terms of neurones, what is present in muscle spasticity?
What will be seen on examination?
The muscle has an intact and functioning lower motor neurone
The descending controls from the brain are not working
On examination the muscle would have an increased tone
(usually a symptom of an upper motor neurone lesion)
What type of things do visceral afferents sense?
Sense the internal environment (organs)
e.g. heart rate, blood pressure digestion, gland secretions, touch, temperature, pain
What are the dual motor controls of the autonomic nervous system?
sympathetics and parasympatehtics
What do motor neurones repond to?
what structures do they supply motor supply to?
Changes in the internal environment
Cardiac muscle, smooth muscle and glands
What type of pain can visceral afferents sense?
What is visceral pain described as?
Ischaemic (reduced blood flow)
Colicky (Obstruction)
Dull, achy, nauseating, poorly localised (can be sharp or localised if colicky)
What type of response does the sympathetic division of the ANS cause?
“fight or flight” response
What effect does sympathetic stimulation have the: Pupils Heart Lungs Gi tract
dilate
heart rate increases
bronchioles dilate
Motility is reduced/ sphincters close
What effect does sympathetic stimulation have on the: Liver Adrenal glands Arterioles Skin
Glucose released into the blood
Adrenaline/ noradrenaline released
Arterioles dilate (e.g. in skeletal muscle) and constrict (e.g. in skin) - skin feels cold and looks pale
Hair stands on end and sweat is produced
Which organs have innervation from the sympathetic/ parasympathetic outflow?
Eyes Heart Lungs Abdominopelvic organs Adrenal medulla (arterioles and body wall organs have sympathetic innervation but not parasympathetic innervation)
What type of state does the parasympathetic division cause?
Rest and digest
returns to homeostasis, compliments/ opposes the sympathetic system
Where does the sympathetic nerves and the parasympathetic nerves synapse?
Sympathetic nerves synapse in the sympathetic chain
Parasympathetic nerves synapse nearer to the organ
