ic1 - neuroanatomy

Question 1

compare the components that make up the CNS and PNS

Answer 1

CNS: brain and spinal cord
PNS: cranial nerves and spinal nerves

Question 2

where is the brain located and what is it protected by and identify the parts of the brain and its components within these parts

Answer 2

brain is located in the cranial cavity

brain is protected by the skull and the meninges

brain is divided into forebrain, midbrain and hindbrain

forebrain consists of cerebrum and diencephalon (consists of thalamus and hypothalamus)

hind brain consists of medulla oblongata, pons and cerebellum

brain stem consists of midbrain, pons, medulla oblongata

Question 3

draw anatomy of brain and spinal cord and identify the parts

Answer 3

identify cerebral hemisphere (cerebrum), midbrain, pons, thalamus, medulla oblongata, foramen magnum, cerebellum

split spinal cord into cervical, thoracic, lumbar, sacral and coccygeal

Question 4

where is the spinal cord located and what is it protected by

Answer 4

spinal cord is located in the vertebral column

spinal cord is protected by meninges and surrounded by cerebrospinal fluid (CSF)

Question 5

how many pairs of cranial and spinal nerves are there

Answer 5

12 pairs of cranial nerves

31 pairs of spinal nerves

Question 6

what does the cerebrum consist of

Answer 6

two cerebral hemispheres separated by longitudinal fissure and connected by corpus callosum

Question 7

what is “cerebral cortex” and what is its structure (differentiate between them)

Answer 7

layer of grey matter on the surface of hemisphere

has gyri (folds) and sulci (grooves)

differentiate between central sulcus, lateral sulcus and parieto-occipital sulcus

Question 8

identify and locate the lobes of the brain

Answer 8

frontal, parietal, temporal and occipital

[frontal] anterior to central sulcus and superior to lateral fissure

[parietal] posterior to central sulcus and superior to lateral fissure

[temporal] inferior to lateral fissure

[occipital] posterior to parietal and temporal lobes

Question 9

what is the function of the sulci of the cerebral cortex

Answer 9

separates the brain into its frontal, parietal, temporal and occipital lobes

Question 10

where is the hypothalamus located at

Answer 10

forms the lower part of the lateral wall and floor of third ventricle

right below the thalamus

Question 11

what are the parts types of cells in the midbrain

Answer 11

dopamine and serotonin cells

has colliculus

Question 12

what is the function of the colliculus and where is it located

Answer 12

it is located in the midbrain and is involved in incorporating environmental stimuli and coordinating gaze shifts involving both eye and head movements

Question 13

what is a “cranial nerve nuclei”

Answer 13

a collection of cell bodies, distinguished to either have a motor or sensory function depending on where its axons goes to

each nuclei can only have either motor or sensory and if a cranial nerve is mixed function of both sensory and motor, that cranial nerve has two nucleis for each sensory and motor

Question 14

categorise the cranial nerves into their respective functions

Answer 14

motor cranial nerves: III, IV, VI, XI, XII
sensory cranial nerves: II, VIII
mixed cranial nerves: V, VII, IX, X

Question 15

what are the cranial nerves and nuclei assoc w and fiber tracts in midbrain

Answer 15

cranial nerves: III, IV
nuclei: III, IV, V, visual and auditory pathways
fiber tracts: ascending and descending fibers

Question 16

where is the pons located

Answer 16

inferior to the midbrain, superior to the medulla oblongata

Question 17

what are the cranial nerves and nuclei assoc w and the fiber tracts in the pons

Answer 17

cranial nerves: V, VI, VII, VIII
nuclei: V, VI, VII, VIII
fiber tracts: ascending and descending fibers

Question 18

where is the medulla oblongata located

Answer 18

most inferior portion of the brain (stem like structure)

Question 19

what are the cranial nerves and nuclei and fiber tracts in the medulla oblongata

Answer 19

cranial nerves: IX, X, XI, XII
nuclei: V, IX, X, XI, XII, cardiovascular and respiratory func
fiber tracts: ascending and descending fibers

Question 20

where is the cerebellum located and explain its structure

Answer 20

located posterior to the pons and medulla oblongata

cerebellum consists of a midline portion (vermis) and two hemispheres

cerebellum connected to the brainstem

Question 21

where is the start point and end point of the spinal cord

Answer 21

continuous with the brain at the foramen magnum of skull

tapers off into conus medullaris

Question 22

distinguish between grey and white matter of the spinal cord

Answer 22

grey matter creates a hornlike structure throughout the inside of the spinal cord while the white matter makes up the surrounding sections of the spinal cord

grey matter consists primarily of neuronal cell bodies (neurons) while white matter made up of myelinated axons

Question 23

what is the properties and function of the nervous tissue

Answer 23

nervous tissue is specialised to receive and generate stimuli (excitable) and transmits impulses (conductive)

Question 24

what are the types of cells in the brain and differentiate between the types of cells

Answer 24

neurons and non neuronal cells (glial cells)

[neurons] structural and functional unit of the nervous system, generate or conduct impulses and are excitable

[glial cells] non conducting, support and protect neurons, 10x the number of neurons, big diversity in terms of shapes and sizes

Question 25

list examples of non neuronal cells (glial cells) in the brain

Answer 25

astrocytes and oligodendrocytes

Question 26

what is the structure of a neuron

Answer 26

cell body (consists of nucleus, ER, mitochondria, golgi) dendrites (have dendritic branches) axons (have axon hillock and synaptic terminals)

Question 27

differentiate the function of a dendrite and the function of axons

Answer 27

dendrites receive information and bring information or impulses towards the cell body of the neuron axons conducts impulses to the next cell

Question 28

what is the "soma" and what does it contain

Answer 28

the cell body of a neuron contains nucleus, various cytoplasmic organelles, cytoplasmic organelles, cytoskeletal elements (eg. actin fibers) and inclusions (aka nutrients or pigments eg. glycogen and lipids)

Question 29

what are "axons" and what is its structure (what is an "axoplasm" and what is its structure)

Answer 29

axons are nerve fibers that conduct impulses away from the cell body most axons are long slender processes that arise from the axon hillock in the cell body and branch at the distal (terminal) end axonal cytoplasm (axoplasm) lacks ribosomes, rough ER and golgi -> since proteins are made in ribosomes, the lack of it means that for a new proteins cannot be synthesised and old proteins cannot be degraded thus materials must be transported back and forth between cell body and terminus (new protein made in soma then cargoed all the way to axon terminal)

Question 30

what kind of transports do axons have and what materials are transported

Answer 30

anterograde and retrogade transports anterograde is from cell body to axon terminal while retrograde is from axon terminal to cell body axoplasm lacks ribosomes, rough ER and golgi thus cannot synthesise new proteins nor degrade old proteins thus transportation of nutrients, cytoskeletal elements and proteins etc via these routes

Question 31

what are the "fast component" and "slow component"

Answer 31

fast component (50-400mm/day) transports cytoplasmic proteins and macro molecules that are required for metabolic (eg. glycogen, glucose for production of energy by mitochondria) and synaptic activities slow component (1-4mm/day) transports cytoskeletal components down the axon -> things that are needed for long term maintenance of the axon thus no urgency for transport and would not require as much energy

Question 32

what are "dendrites" and what is the structure of it

Answer 32

dendrites conduct impulses towards cell body dendrites usually are relatively short and highly branched, contains all the cytoplasmic components found in the cell body except golgi (have ribosomes and ER to make own proteins thus do not need transportation)

Question 33

do dendrites require the same transportation system as axons

Answer 33

no as they have their own ribosomes and ER to synthesise own proteins

Question 34

what are "dendritic spines"

Answer 34

they stick out of dendrites (protrusions on dendritic shaft) vast majority of excitation synapses are formed on the top of dendritic spine

Question 35

what are "synapses" and what are the types of synapses (differentiate between them)

Answer 35

chemical and electrical synapses in a chemical synapse, impulses are transmitted chemically via neurotransmitters vs in an electrical synapse, nerve impulse transmitted electrically via channel proteins (through gap junction channels)

Question 36

from where to where are impulses transmitted

Answer 36

impulses are transmitted from one neuron (presynaptic) to another neuron (postsynaptic) or from a neuron to an effector cell (muscle) at synapses

Question 37

what are the components of a "chemical synapse" and how does it work (presynaptic membrane, voltage gated Ca2+ channels, synaptic cleft, postsynaptic membrane) and what are the different types of a synapse

Answer 37

chemical synapses have presynaptic axon terminal which is a small knoblike termination of the transmitting neuron and contains synaptic vesicles filled with a neurotransmitter the presynaptic membrane is a thickened region in the plasmalemma of the presynaptic axon terminal and contains voltage gated Ca2+ channels when AP reaches axon terminal, it activates the opening of Ca channels which causes influx of Ca ions into the terminal thus causing a rise in cytosolic Ca2+ level which triggers exocytosis of the neurotransmitter into the synaptic cleft the synaptic cleft is a 20-40nm wide space separating the pre and postsynaptic membranes across which a neurotransmitter diffuses the postsynaptic membrane is a thickened region in the plasmalemma of a receiving dendrite that contains neurotransmitter receptors path follows to either excitatory or inhibitory synapses

Question 38

compare what happens at the excitatory synapse compared to what happens at the inhibitory synapse

Answer 38

at excitatory synapse, binding of neurotransmitter to its receptor causes opening of Na+ channels in the postsynaptic membrane which depolarises the membrane in the postsynaptic cell at the inhibitory synapse, neurotransmitter binding leads to opening of K+ or Cl- channels in the postsynaptic membrane which leads to hyperpolarisation of the membrane and thus no action potential in the postsynaptic neuron

Question 39

what are the types of glial cells and its respective composition and function

Answer 39

astrocytes, oligodendrocytes, microglia [astrocytes] 25% (i) forms BBB (ii) structural support, scar formation (iii) secretion of nerve growth factors (iv) water transport (v) excess transport (cerebral edema -> clear extra fluid from brain and nervous tissue) (vi) regulate composition of intercellular environment and entry of substances into it (vii) provide structural support to neurons and specifically to synapses (viii) metabolise neurotransmitters (regulate homeostasis of GLUTAMATE) (ix) mediate exchange of nutrients and metabolites between blood and neurons [oligodendrocytes] 60-80% (i) formation of myelin sheath around axons [microglia] 5-10% (i) act as brain macrophages -> causes phagocytosis (ii) secretion of proinflamm cytokines (TNF alpha and IL1beta), chemokines (iii) Ag presentation function (MHCII Ag) (iv) immunocompetent cells of CNS

Question 40

what is the structure of astrocytes

Answer 40

largest size of the neuroglial cells, have numerous processes with expanded end-feet (pedicles) that terminate on capillaries or on the pia mater

Question 41

what are the types of astrocytes (location, structure)

Answer 41

fibrous and protoplasmic astrocytes [fibrous astrocyte] located primarily in white matter, long, spindly processes with few branches [protoplasmic astrocyte] located in gray matter, thick, lightly branched processes, closely apposed to neuron cell body -> can support cell body and keep it in place (fibrous astrocyte touches vessel to form BBB vs protoplasmic astrocyte touches neuron cell body)

Question 42

what is the "tripartite synapse"

Answer 42

consists of axon terminal, dendritic spine and astrocytic process

Question 43

where are oligodendrocytes found in

Answer 43

in both white and gray matter in white matter, it is the most predominant type of neuroglial cell and produce the myelin sheath around myelinated fibers in gray matter, they are closely assoc with neuron cell bodies, functioning as satellite cells -> to give structural support

Question 44

what is the r/s between shwann cells and oligodendrocytes

Answer 44

schwann cells are analogues of oligodendrocytes (for PNS)

Question 45

what special component do oligodendrocytes express that would help in injury and ischemia in CNS

Answer 45

oligodendrocytes express Nogo-A which is a myelin assoc neurite outgrowth inhibitor which plays a key role in inhibition of axonal regulation following injury and ischemia -> neutralization or blockade of Nogo-A enhances regeneration

Question 45

what is the structure of microglia

Answer 45

small phagocytic cells that enlarge and become mobile after injury to CNS monocyte origin

Question 46

what is the PNS composed of

Answer 46

neuron processes and cell bodies located outside CNS, neuroglial cells (shwann cells and satellite cells), nerve endings

Question 47

what is the structure of a peripheral nerve

Answer 47

a peripheral nerve comprises bundles (fasicles) of nerve fibers (axons) that are surrounded by myelin sheaths or schwann cells and have three connective tissue elements (epineurium, perineurium, endoneurium) (axons from different neurons -> form fasicle -> multiple fasicles form a peripheral nerve)

Question 48

what is the "epineurium", "perineurium" and "endoneurium"

Answer 48

they are the three connective tissue elements part of the peripheral nerve structure [epineurium] connective tissue surrounding entire nerve [perineurium] layer of dense connective tissue around each fasicle of nerve fibers [endoneurium] thin reticular layer that surrounds each individual nerve fibers and contains schwann cells

Question 49

compare the myelin sheaths in CNS and PNS

Answer 49

in PNS, myelin sheath formed by schwann cells, each individual schwann cells can only myelinate portions of a single axon in CNS, myelin sheath formed by oligodendrocytes, each individual oligodendrocytes can myelinate portions of several axons

Question 50

what is a "ganglia" and what is the structure of a peripheral ganglion

Answer 50

ganglia are encapsulated collections of neuron cell bodies located outside of the CNS and contains satellite cells and connective tissue elements along with neurons

Question 51

what are "satellite cells"

Answer 51

satellite cells (amphicytes) form a capsule of cells around neuron cell bodies located in peripheral ganglia act similarly to astrocytes in CNS

Question 52

what is the arterial supply to the brain

Answer 52

two pairs of arteries -- left and right internal carotid arteries and left and right vertebral arteries supply blood to brain

Question 53

what is the "vertebrobasilar arterial system"

Answer 53

vertebral artery originates from subclavian artery in the neck and enters the skull through foramen magnum vertebral artery branches to supply spinal cord, medulla oblongata and cerebellum: (i) anterior spinal artery (ii) posterior spinal artery (iii) posterior inferior cerebellar artery the two vertebral arteries joins to form a single artery -- basilar artery basilar artery branches to supply pons, cerebellum and inner ear: (i) anterior inferior cerebellar artery (ii) pontine branches (iii) labyrinthine artery (iv) superior cerebellar artery basilar artery ends (after going to top of pons) by dividing into two posterior cerebral arteries posterior cerebral artery supplies midbrain, medial aspect of occipital lobe and base of temporal and occipital lobes

Question 54

what is the "carotid arterial system"

Answer 54

internal carotid artery originates from common carotid artery in the neck and enter the skull through carotid canals and is situated within the cavernous sinus internal carotid artery ends by dividing into anterior cerebral artery and middle cerebral artery (i) anterior cerebral artery passes forward into medial longitudinal fissure and sweeps back to parieto-occipital sulcus to supply most of medial surface of hemisphere (except medial aspect of occipital lobe) (ii) middle cerebral artery pass laterally between temporal and frontal lobes and emerges at lateral fissure and fans out to supply most of lateral surface of hemisphere (frontal, parietal, temporal and occipital)

Question 55

what is the "circle of willis" and its function

Answer 55

it is an anastomosis (connection) between left and right arteries supplying the brain may help to supply blood to opposite side in cases of slow occlusion of an artery on one side (not effective if sudden occlusion) (i) anterior communicating artery connects anterior cerebral arteries of both sides (ii) posterior communicating artery connects middle cerebral artery with posterior cerebral artery thus (i) and (ii) forms an anastomotic ring between vertebral and internal carotid arteries arterial ring is located at base of brain

Question 56

what is "aneurysm" and what is a frequent site for it

Answer 56

aneurysms are abnormal out pocketing of the wall of a blood vessel a frequent site for it is the circle of willis

Question 57

where does blood from the brain drain into (superior, inferior, centre of brain)

Answer 57

blood from the brain drains into venous sinuses which eventually empty into internal jugular vein (i) blood from superficial part of the superior aspect of brain drains into superior sagittal sinus (ii) blood from inferior part of brain drains into transverse sinus and superficial middle cerebral vein -> superficial middle cerebral vein drains into cavernous sinus which is closely related to cranial nerves III, IV, V, VI and is part of internal carotid artery (iii) blood from centre of brain drains into deep cerebral veins -> deep cerebral veins drain into venous sinus (straight sinus) route 1: blood from superficial and deep parts of brain drain into venous sinuses -> drain into internal jugular vein and heart route 2: blood from superior sagittal and straight sinuses flow into transverse sinus -> sigmoid sinus -> internal jugular vein

Question 58

compare the venous pressure in the brain vs the body

Answer 58

venous pressure in the brain very much lower compared to rest of body bc venous sinuses are much bigger in the brain

Question 59

what is a "subdural hemorrhage"

Answer 59

rupture of a cerebral brain that occurs between one of the superior cerebral veins as it drains into the superior sagittal sinus

Question 60

what forms the blood brain barrier and what is the function of BBB

Answer 60

capillaries of the brain that have tight junctions between endothelial cells forms BBB that prevents random entry of water soluble substances into the brain parenchyma BBB formed by astrocytes

Question 61

what is "cerebrospinal fluid" and its function and what is it produced by

Answer 61

CSF is a clear fluid that acts as a protective liquid cushion around the brain and spinal cord by absorbing shock waves from blows and falls since brain has no lymphatic channels, CSF also helps remove metabolites from brain CSF produced by a delicate lace like structure -- choroid plexus in cerebral ventricles (lateral ventricle)

Question 62

what is the flow of CSF

Answer 62

flows from lateral ventricle (where it is mostly produced at) -> to third ventricle -> to forth ventricle via cerebral aqueduct -> flows out of forth ventricle to bathe whole brain and spinal cord CSF absorbed into superior sagittal sinus by arachnoid granulations

Question 63

what are the components in the meninges of the brain

Answer 63

dura mater, arachnoid, pia matar