Anatomy Flashcards
What does the CNS includes?
Brain & spinal cord
Where is the brain located?
Cranial cavity
What is the brain protected by?
Skull & meninges
How is the brain divided?
- Forebrain
- Midbrain
- Hindbrain
What does the forebrain include?
- Cerebrum
- Diencephalon
What does the hindbrain include?
- Medulla oblongata
- Pons
- Cerebellum
The hindbrain is also called _________
Brainstem
Where is the spinal cord located?
Vertebral column
What is the spinal cord surrounded by?
Cerebrospinal fluid (CSF)
What is the spinal cord protected by?
Meninges
How many cranial nerves are there in the PNS?
12 pairs
How many spinal nerves are there in the PNS?
31 pairs
The _______ is the largest part of the brain.
Cerebrum
The cerebrum consists of 2 _______________.
Cerebral hemisphere
What separates the hemispheres of cerebrum?
Longitudinal fissure
What connects the 2 hemispheres of the cerebrum?
Corpus callosum (at the bottom)
What is the cerebral cortex? Where is it located?
A layer of grey matter on the surface of the hemispheres of cerebrum
What are gyri and sulci?
Gyri: ridges on the surface of the brain. Suci: fissues surrounding each ridge
Frontal lobe wrt central sulcus
Anterior (in front)
Frontal lobe wrt lateral fissure
Superior (above)
Parietal lobe wrt to central sulcus
Posterior (behind)
Parietal lobe wrt to lateral fissure
Superior (above)
Temporal lobe wrt lateral fissure
Inferior (below)
Occipital lobe is posterior to ______?
Parietal & temporal lobes (separated by parieto-occipital sulcus)
The hypothalamus forms the lower part of the _________ and floor of __________.
Lateral wall, third ventricle
The midbrain contains nuclei of which cranial nerves?
III (oculomotor) & IV (trochlear)
Cranial nerve II
Optic nerve (vision)
Cranial nerve V
Trigeminal nerve (sensation)
Cranial nerve III
Oculomotor nerve (eye movements and sensory function)
Cranial nerve IV
Oculomotor nerve (eye movements and sensory function)
What are fiber tracts?
White matter tract that connects the cortex with other areas of the CNS
Pons is located __________ to the midbrain
Inferior
Pons is located _________ to the medulla oblongata
Superior
The pons contains nuclei of which cranial nerves?
V, VI, VII, and VIII
Medulla oblongata is the most ________ portion of the brain
Inferior
The medulla oblongata contains nuclei of which cranial nerves?
IX, X, XI, XII
What functions is the medulla oblongata associated with?
Helps control vital processes like your heartbeat, breathing and blood pressure
What functions are the pons asscoiated with?
Unconscious processes such as your sleep-wake cycle and breathing
Cerebellum is located ________ to the pons and medulla oblongata
Posterior
Cerebellum is connected to the _________
Brainstem
What does the cerebellum consist of?
A midline portion (vermis) and 2 himespheres
Spinal cord is _____ with the brain at the ________ of the skull.
Continuous, foramen magnum
Where does the spinal cord taper off?
Conus medullaris
Outer part of the spinal cord
White matter
Inner part of the spinal cord
Grey matter
Two functions of the nervous tissue
- Receive and generate stimuli (excitable)
- Transmit impulses (conductive)
Two properties of the nervous tissue
- Receive and generate stimuli (excitable)
- Transmit impulses (conductive)
What are the types of cells in the brain?
- Neurons
- Non-neuronal cells (glial cells)
What are glial cells?
Non-neuronal cells in the brain
What are the main differences between neurons and glial cells
- Neurons are able to generate/conduct impulses and are excitable
- Glial cells are x10 the number of neurons
Three important parts of the neuron
- Cell body
- Axon
- Dendrite
What is the cell body of the neuron called?
Soma
What does the cell body (soma) of a neuron contain?
- Nucelus
- Cytoplasmic organelles
- Cytoskeletal elements
- Golgi complex (near nucleus)
- Mitochondria (throughout cytoplasm)
What are axons?
Nerve fibres of neurons
What is the function of an axon?
Conduct impulses away from cell body
Most axons are ______ processes that arises from the _________ in the cell body and branch at the _________.
long, slender
axon hillock
distal (terminal) end
What is an axonal cytoplasm (axoplasm)?
The cytoplasm within the axon of a neuron
Notable structures of an axonal cytoplasm (axoplasm)
Lacks ribosomes
RER
Golgi apparatus
Why are materials transported back and forth between the cell body and terminus of an axon?
The axon terminus lack components for synthesizing new materials
What is the rate of slow axonal transport?
1 to 4mm/day
What is the rate of fast axonal transport?
50-400mm/day
What does the fast axonal component transport?
Cytoplasmic proteins and macromolecules - required for metabolic and synaptic activity
What is the function of dendrites?
Conduct impulses toward the cell body
Dendrites are usually relatively ______ and __________
Short
Highly branched
What do dendrites contain?
Cytoplasmic components found in cell body except for Golgi apparatus
Synapses connect neurons in the _____ to neurons in the ________ and from those neurons to the _________.
Brain, rest of the body, muscle
What are synapses?
Regions of functional apposition where impulses are transmitted from one neuron (presynaptic) to another neuron (postsynaptic) or from a neuron to an effector cell (muscle)
What are chemical synapses?
Presynaptic axon terminal: small knoblike termination of the transmitting neuron
What do chemical synapses contain?
Vesicles filled with neurotransmitter
Where is the presynaptic membrane?
Thickened region in plasmalemma (of presynaptic axon terminal)
What do presynaptic membrane contain?
Voltage-gated Ca2+ channels
What happens after the arrival of an action potential at an axon terminal?
Ca2+ channel opens → influx of Ca2+ ions → rise in cytosolic Ca2+ level
What does the rise in cytosolic Ca2+ level trigger?
Exocytosis of the neurotransmitter into synaptic cleft
What is the width of a synaptic cleft?
20-40nm
What is a synaptic cleft
Space separating presynaptic and posynaptic membranes
(neurotransmitter diffuses across)
Where is the postsyanptic membrane?
Thickened region in plasmalemma of a receiving dendrite (contains neurotransmitter receptors)
Where does the neurotransmitter bind to its receptor?
Excitatory or inhibitory synapse
What happens after binding of neurotransmitter to its receptor (at excitatory synapse)?
Na+ channels open in postsynaptic membrane → depolarise membrane → action potential in postsynaptic cell
What happens after binding of neurotransmitter to its receptor (at inhibitory synapse)?
K+ or Cl- channels in postsynaptic membrane opens → hyperpolarisation of membrane → no action potential in postsynaptic neuron
Types of glial cells in the CNS
Astrocytes
Oligodendrocytes
Microglia
Proportion of oligodendrocytes
60-80%
Function of oligodendrocytes
Myelin sheath formation
Proportion of astrocytes
25%
Properties of astrocytes
- BBB
- Structural support**, scar formation **
- Secretion of nerve growth factors
- Water transport
- Excess transport (cerebral edema)
Proportion of microglia
5-10%
Functions of microglia
- Brain macrophages**, phagocytosis
- Secretion of pro-inflammatory cytokines (TNFa, IL1b), chemokines
- Antigen presenting function (MHCII antigen)
- Immunocompetent cells ** of CNS
Astrocytes are the ________ of neuroglial cells
Largest
Fibrous astrocytes are located primarily in the __________.
White matter
Fibrous astrocytes are _______ processes with _______.
long, spindly
few branches
Protoplasmic astrocytes are located in the __________.
Grey matter
Protoplasmic astrocytes are ______ processes, closely apposed to _________.
thick, lightly branched
neuron cell bodies
Functions of astrocytes
- Regulates composition of intercellular environment & entry of substances into it
- Provide structural support to neurons (specifically synapses)
- Metabolise neurotransmitters
- Mediate exchange ofnutrients & metabolites between blood & neurons
Name a type of neurotransmitter metabolised by astrocytes
Glutamate glutamine shuttle
Tripartite synapses
Between astrocytes and neurons
Oligodendrocytes produces ________ around ________ in white matter.
myelin sheath
myelinated fibers
What do oligodendrocytes function as in grey matter?
Satellite
What are oligodendrocytes closely associated with in grey matter?
Neuron cell bodies
What is the region not insulated by myelin sheath called?
Node of Ranvier
Cell marker of oligodendrocytes
CNPase
Oligodendrocytes expresses _________.
Nogo-A (myelin associated neurite-outgrowth inhibitor)
Inhibits axonal regeneration following injury and ischaemia in CNS
What are microglia
Small phagocytic cells that enlarge and become mobile after injury to CNS
Microglia are implicated in _________?
Alzheimer’s disease, Parkinson disease, cerebral ischaemia (stroke) etc
PNS composes of
- Neuron processses and cell bodies located outside the CNS
- Neuroglial (Schwann cells & satellite cells)
- Nerve endings
A peripheral nerve comprises bundle (______) of nerve fibers (_______) surrounded by myelin sheath or Schwann cells.
fascicles, axons
What are the 3 connective tissue elements fascicles of nerve fibrers are invested with?
Endoneurium (inside)
Perineurium (around)
Epineurium (outside)
Epineurium
Connective tissues surrounding the entire nerve
Perineurium
Layer of dense connective tissue around each fascicle of nerve fibers
Endoneurium
Thin, reticular layer that surrounds each individual nerve fiber & contains Schwann cells
What forms myelin sheath around myelinated axons
Schwann cells
Difference between myelin-producing cells in CNS and PNS
CNS: individual oligodendrocytes myelinate portions of SEVERAL axons
PNS: individual Schwann cells myelinate portions of only a SINGLE axon
What are ganglia/ganglion?
Collections of neuron cell bodies located outside CNS
What do ganglia contain?
Satellite cells and connective tissue elements along with neurons
Satellite cells (__________) form a capsule of cells around neuron cell bodies located in the peripheral ganglia
Amphicytes
What are the two pairs of arteries that supply blood to the brain?
Left and right internal carotid arteries & vertebral arteries
The vertebral artery originates from the _____________ in the neck.
Subclavian artery
The vertebral artery enters skull through the _______________.
Foramen magnum (hole at the base of the skull)
What are the branches the vertebral artery gives to supply the spinal cord, medulla oblongata and cerebellum?
Anterior spinal artery
Posterior spinal artery
Posterior inferior cerebellar artery
What is the single artery in the midline the two vertebral arteries join?
Basilar artery
What does the basilar artery branch off to?
- Anterior inferior cerebellar artery
- Pontine branches
- Labyrinthine artery
- Superior cerebellar artery
What does the basilar artery supply?
Pons, cerebellum and inner ear
What does the basilar artery divide into?
Two posterior cerebral arteries
What does the posterior cerebral artery supply?
- Midbrain
- Medial aspect of occipital lobe
- Base of temporal and occipital lobes
Internal carotid artery originates from _______ in neck.
Common carotid artery
Internal carotid artery enter skull through ________.
Carotid canals
Where is internal carotid artery situated at?
Within cavernous sinus
What do the internal carotid artery divide into when it ends?
Anterior cerebral artery & middle cerebral artery
___________ supplies most of the medial surface of hemisphere (except medial aspect of occipital lobe)
Anterior cerebral artery
What do the middle cerebral artery pass laterally?
Temporal & frontal lobes
________ is a connection between left and right arteries supplying the brain.
Circle of Wilis
Circle of Wilis helps to supply blood on opposite side during ______________ on one side.
Slow occlusion of an artery
_________ connects the anterior cerebral arteries of both side.
Anterior communicating artery
__________ connects the middle cerebral artery and posterior cererbal artery
Posterior communicating artery
Where is the circle of Wilis located?
Base of brain
Blood from brain drains into ___________, which eventually empty into _____________.
venous sinuses
internal jugular vein
Blood from superficial part of the superior aspect of brain drains into ___________.
Superior sagittal sinus
Blood from inferior part of brain drains into ___________.
Transverse sinus & superficial middle cerebral vein
Superficial middle cerebral vein drains into _________.
Carvernous sinus
What CNs is the carvenous sinus related to?
III, IV, V, VI
Carvenous sinus is part of the _________.
Internal carotid artery
Blood from centre of brain drains into ___________.
Deep cerebral veins
Deep cerebral veins drain into _______.
Venous sinus (straight sinus)
Blood from both superficial and deep parts of brain drain into venous sinuses then to the _________ and the heart.
Internal jugular vein
Superior sagittal and straight sinuses flow into transverse sinus, continues to ______, which drains into internal jugular vein of neck.
Sigmoid sinus
Rupture of cerebral vein between one of the superior cerebral vein as it drains into the superior sagittal sinus leads to?
Subdural haemorrhage
Capillaries of the brain have ________ between endothelial cells that form BBB, preventing random entry of water soluble substances into brain parenchyma.
Tight junctions
Functions of CSF
- Protective “liquid cushion’
- Metabolites removal
What is CSF produced by?
Choroid plexus in cerebral ventricles
Flow of CSF
Lateral ventricle → 3rd ventricle → 4th ventricle via cerebral aqueduct → bathe whole brain and spinal cord
Where is CSF absorbed?
Superior sagittal sinus
How is CSF absorbed?
Arachnoid granulations
