CNS anatomy

Question 1

What is the CNS briefly? What does it include? And what is its main role?

Answer 1

The CNS is the central nervous system-composed of the brain-the brain stem and the spine
Its main role is information processing-intaking from PNS afferent division and acting through PSN efferent division (autonomic and somatic)

Question 2

How is the spinal cord organised? How many nerves are found coming out? where do they exit/enter?

Answer 2

Spinal cord sits within the spine-coming down from the brain-goes from C1 to L1/2 (shorter than vertebral column)-after that only nerves coming out/down
All the nerves come out under their named cervical (eg: T12 comes out under C12), except for C1
31 spinal nerves for average 33 vertebrae

Question 3

From how the spinal cord is organised, where would a lumbar punction be done to take fluid?

Answer 3

Would be done after the spinal cord ends-between L2/3 or L3/4-lower in children because spinal cord takes more space

Question 4

Describe the anatomy of the spinal cord? (in relation to horns, roots, ganglia, efferent and afferent

Answer 4

Spinal cord is made of a center of grey matter (cell bodies) and white matter (axons going up/down)
Spinal cord has 4 horns on each side (2xDorsal hrn, 2x ventral horn)
Ventral horn in connected to ventral root (motor, efferent)-connects to mixed nerve with dorsal root
Dorsal horn connected to dorsal root (afferent, sensory)-has a ganglia with cell bodies)-connects to ventral root to make mixed nerve

Question 5

What are the functions of the spinal cord?

Answer 5

Spinal cord is the connector between PNS/ANS and the brain (efferent and afferent go up and down from brain to periphery)
eg: intakes the snesory signals and carries motor signals-also role is sympathetic
coordinate reflexes (direct)

Question 6

What are the 3 parts of the brain usually descibred?

Answer 6

Cerebrum (main brain)cerebral hemisphere and diecenphalon), brain stem (midbrain, pons, medulla) and cerebellum

Question 7

Describe the rough anatomy of the brain stem, its functions and main features.

Answer 7

Brain stem is between spinal cord and cerebral hemisphere-all sensory and motor fibres pass by it and can activate stuff
Midbrain proxiam to brain-then pons and then medulla
Contain nuclei of 10/13 cranial nerves (III-XII)
Main roles-regulates vital functions like breathing, heart rate, blood pressure, swallowing (ANS)
Many defensive reflexes (cough, gag sneeze)

Question 8

What is the diencephalon composed of? What are its main functions?

Answer 8

Diencephalon is part of cerebrum-made of thalamus and hypothalamus (thalamus is 2 lobes either side of brain stem), hypo is smaller lobe center connected to pit gland
Hypothalamus role-intrgation of singals and hormonal, ANS and other functions
Thalamus-integration centre for special senses-and projction to cortex-involved in emotional status, appropriate motor response, consciousness

Question 9

What are the 2 parts that make up the cerebral hemispheres?

Answer 9

2 hemispheres (cortex) and basal ganlia-on top of brain stem and diecenphalon

Question 10

Describe the 3 different parts of the basal ganglia, and their function

Answer 10

3 parts-caudate, putamen and globus pallidus-form 2 ganglia on either side
2x Putamen is lateral to the ganglia (on the outside)
2x Caudate is on top, connected by striate (drosal/superior to caudate)
Together they make Corpus striatum
Globus pallidus sits medial to the caudate-on the other side
together they form lentiform nucleus
Function-control movement-fine tuning, inhbiting innapropriate movement

Question 11

Describe the organisation of the cerebral cortex, naming schemes for features

Answer 11

Cerberal cortex-frontal lobe , then parietal , then occipital
On either side-temporal lobes
The flods make gyrus (outgrowth) and suclus (foldings)
hemispheres are speratated by longitudinal fissure
Frontal and partietal seprates by central fissure

Question 12

Describe the main functions of the cortical functional areas

Answer 12

Frontal cortex-has prefrontal cortex (sense of relation with world-mood personality), brocha area (left-speech), motor association area (plan a program for muscle contraction for an action (like dancing), primary motor cortex (contralateral-for movement)
Parietital cortex-primary somethetic cortex-sense
Somesthetic associatin area-interpresents sensory intepreation and coordinate very large
Ociipital-primary visual cortex and visual association area
Temporal-Wernicke area (left)-recognise language, primary gustatory (taste), aditory cortex (hear)

Question 13

Describe the anatomy, function and main features of the cerebellum

Answer 13

attached posterially to brainstem
Outsdie grey cortex with parallel folds, deeper-white matter (nuclei)
Two hemispheres in lobes-central vermis (dip)
Connected to balance, spinal cord for posture and muscle tone, motor cortex and thalamus-helps you learn and commit to memory (specially movement)

Question 14

How are different parts of the brain connected? What are the 3 main fibers in the cerebrum?

Answer 14

White matter in brain describes the axons (opposite of spine)
between hemispheres, commisural fibers (corpus collosum)
Within hemispheres -association fibers
to spine and rest of body-projection fibers

Question 15

Look up image of cranium bones

Answer 15

But remember roughtly-frontal (frontl), sphenoid, temporal, occipital
Ethmpid between frontal
Temproral on the side

Question 16

Describe the organisation of the meninges

Answer 16

Under skin, bone-dura mater (two layers, exterior periosteal, interior meningeal)
Then arachnoid mater, then pia mater-these continue all around the cortex (not following bone but even within folds)
This is where blood vessels (capilaries and veins sit)
cortex sperated by subarachnoid space (vessels)

Question 17

Describe the anatomy of the CSF ventricular system?

Answer 17

Large latral ventricules (2x) like horns sourround basal ganglia and diecephalon-connected to3rd ventricule-sit right between hypothalamus (little hole to allow connection) 1x
connected by aqueduct to 4th venticule (loacted near pons of brainstem)-then goes into spine and brain from there

Question 18

What is CSF mostly made of? What is its function?

Answer 18

Similar to blood plasma BUT lower glucose, lower prots, lwoer ca, K, higher Cl, Mg, and slightly lower pH
Function-cushioning, bringing nutrition, removing waste and immune cell
used for diagnosis (lumbar punction)-if meningitis (bacterial ahs lower gluc and higher prots)

Question 19

Describe the pathway of CSF flow

Answer 19

Blood-taken by lateral, 4th and 3rd ventricule and converted to CSF (filtering)
All then goes to fourth venticule-where though lateral and medial apertures goes to subarachnoid space
At arachnoid vili of dural veins-collects into venous blood and goes back to the heart

Question 20

What does the PNS consist of?

Answer 20

ANything that inst CNS-all the nerves as soon as they exist the spine and cranial nerves

Question 21

Where do (unipolar) sensory come from in regards to embyology

Answer 21

When the neural plate form, the extriot (neural plate border) form the top of the neural tube after envagination
These cells will then split of and mirgate from spinal crest-these from sensory neurons after (cell body that go in ganglia

Question 22

What is the anatomy of sensory neurons? What are the 3 types of fibers?

Answer 22

Dendrites sit in sensory receptors in the skin-then connect to cell body in dorsal ganglia-from there axon connects back to spinal cord-sends signal back up
3 fibres are A fibres (myelianted somatic), B fibers (myelinated viscleral) and C fibers (myelinated or unmyelinated, pain)

Question 23

What does the somatic nervous system consists of?

Answer 23

part of the motor division-but conscious decisions (voluntary) or reflexes
Efferent nerves that come from upper motor neurons in cerbral cortex-then either connect down to rbrain stem or down in spinal cord
From there, lower motor neurons connected to skeletal muscle-can have more than one nerve per muscle, but only 1 per terminal per fiber

Question 24

Where do motor neurons come from in regards to embyology

Answer 24

The top cells from neural cresit form sensory (dorsal root), while ventral (basal plate) migrate as motor neurons-cell bodies stay in spin

Question 25

How do sensory and motor neurons come out of the spine?

Answer 25

2 roots-from dorsal horns-dorsal root is sensory, afferent-with cell bodies in ganglia outside From ventral horn-ventral root-motor neuron/efferent-cell bodies in the spine then connecting to effector The 2 quickly merge into spinal nerve-comes out under vertebrae through intervertebral foramen '(except c1)

Question 26

How many cranial nerves and spinal nerves do we have?

Answer 26

12 cranial nerves | 31 spinal nerves C1-8, T1-12, L1-5, S1-5, coccygeal nerve (Co1)

Question 27

What does the autonomic nervous system consist of?

Answer 27

part of motor divison-2 categories-sympathetic and parasympathetic opposite effects usually-SNS is fight, PSNS is rest Start in the hypothalamus-1st neuron connects to brain stem nuclei or spinal cord (SNS) From there-preganglionic (called presynaptic for vagal and sacral PSNS) neuron that connects to ganglia (near spine for SNS or in target organ for PSNS) 3rd neuron-post ganglionic/synaptic that connect to visceral efferctors

Question 28

Where do Autonomic nervous system neurons come from in regards to embyology

Answer 28

Top of basal plate (motor neurons) axons dont extend out but up-make preganglionic sympathetic (T1-L2) SNS and pre synatpic scaral neurons (s2-s4) in PSNS Mutlipolar, Myelianted B fibres Post ganglionic and post synaptic neuron-cell bodies move out to make ganglias (from basal plate)-multipolar unmyelinated C fibres

Question 29

What is myelin? How is in organisedd/made in the SNS?

Answer 29

Myelin sheath are mostly the protein rich cytoplasm of swchann cell-they wrap around them selves and their cytoplasm forms loops around axon-up too 100 layers in A fibrers Small gaps between cells-nodes of ranvier where Na/k exchange can happen and increase AP Main role in speed of propagation

Question 30

How is the speed of the impulse propagation changed in different fibres of the SNS?

Answer 30

propagation speed is dependent of largness of axon (larger-faster) and the myelination Therefroe A fiber-large and lyelinated-fastest B-in between C thin and unmyelianted-slow

Question 31

In the SNS, what are rootlets, roots, rami and ganglia?

Answer 31

rootlets are the numerous neron bundles exiting ventral/dorsal horn before connecting into ventral/dorsal root They then connect into 1 spinal nerve-but that splits up into: Dorsal ramus of spinal nerve-goes to innervate back of spine) and ventral ramus of nerve (eg:intercostal nerve) that innervate the front of spine (also connecting remi branch off the nerve into the ganglions of the ANS (communaicting remi)

Question 32

How are PSNS cranial nerves oragnised in the skull?

Answer 32

Nerve will come up as bundle of axon and then split off numerous times (eg vagus nerve), innervating

Question 33

How are paravertebral and collateral of the SNS organised?

Answer 33

nerves (preganglionic) start (soma) in the spinal cord-then borrow same route of efferent nerves (motors), but split of by communicating remi to sympathetic ganglia (they are stacked on top of one another either side of the spine)-or some collateral ganglia (for visceral organs, ganglia ouside the stack) from there, nerves connect to other soma, and these go back to spinal nerve (sweat glands, piloecrector msucles, iris, salivary glangs, etcc

Question 34

What are nerve plexuses (plexi)

Answer 34

Several spinal nerves (ventral remi) connect to the same area-form plexuses before organ-network of sucesciss ventral remi that EXCHANGE fibers are redistributed Mostly for muscles Thoraci ventral remi dont form plexuses

Question 35

What are dermatomes? And reffered pain?

Answer 35

Each spinal nerve (efferent) comes into a specific part of the spine, and come from a specific part of the body-therefore can map out which nerve managed which parts These parts-when sensory (area of skin MAINLY supplied by single sensory spinal nerve root)-dermatome -therefore damage in 1 nerve makes you lose sensation in that specific dermatome. eg: S2 and S3 do penis dermatome Some area are innevrated through pelxuses-some sensory areas come from more than one spinal root Furthermore-roots split and go to different organs, and can have other neurons in them (such as visceral afferents, or pain neurons)-actiavte nerve of a dermatome on the way back to brain-eg: visceral sensory nerve of heart joins back the same nerve as that then goes to T2,3,4 dermatomes-heart pain is felt there-REFFERED PAIN

Question 36

What are mytomes?

Answer 36

Muscle areas that are mainly innervated by a single spinal nerve (eg C1/2 do neck extension), C3 do neck laterally, etc

Question 37

What does peripheral neuropathies mean? What do the terms mono and poly neuropathy means?

Answer 37

Damage of disease of PNS nerve-can impair sensation, movement, gland or organ Sensory nerve-cause tingling, pain, numbness, motor nerve-cause weakness hand and feet Autonimic nerves-changes in heart rate and stuff Can have many causes-metabolic, toxic, inflamatory, traumatic, genetic-and 30% are idiopathic (unknown origin) Mono: single nerve affected Poly-several nerves affected

Question 38

Describe how PNS nerves are envelopped

Answer 38

Endoneurium around individual axons/neuron-loose collager Perineurum-around a bundle of neuron axons (tensile strnth) Epineurum-around entire nevre-dense, has blood vessels and fatty tissue

Question 39

What do the 3 PNS nerve injurt classification (neuropraxia, axonotmesis and neutotmesis) describeN

Answer 39

Neuropraxia-reversible-selectinve demyelination,-endoneurium and axon still intact -eg: nerve compression Axonotmesis-demyelination and axon loss but epi and perinerium intact (still continuity between nerve). Degenration distal to injury (from cell body)-walleraian degeneration Neurotmesis-complete nerve divison (lose all 3 layers)-no nerve regrowth

Question 40

Describe the main steps of axon regeneration (after axonotmesis)

Answer 40

Distal to site of injury-wallerian degenaration makes everything degrade and clear Then axon proximal end regenrate in tube of schann cells-grow until target is found and connect-then remyelin and works Can go wrong and reconect wrong

Question 41

What is Electromyography?

Answer 41

Needle EMG measures the AP in target (eg:in thumb) after patient is asked to contract it Norrmal-nothing at rest, contracts more and more as signal increases Denervated-fibrilate at rest-very large unit for mild activation and not much more at maximal signal Myopathy-fibrilate, then with signal smal polyphasic units, and full interference at max

Question 42

What is nerve conduction study?

Answer 42

have two electrodes along nerve trying to be studies-send a signal from the first measured by second-passing by the nerve Can measure connection, amplitude response AND velocity

Question 43

What is somatosensroy evoked potential?

Answer 43

Mix of EMG and NCS-evaluate lesions in pathways/latecy small stiumulus given somewhere and then measured way down pathway need averaging because very small nerve responses