Nervous System Flashcards
What are the 2 types of nervous tissue cells?
1) Neurons
2) Glia
What are neurons?
Specialized cells for generating and propagating impulses across cells
What are glia cells?
Support cells of the NS
What is the basic cell of nervous tissue?
Neurons
What 4 structures make up a neuron?
1) Dendrites
2) Cell body
3) Axon
4) Axon terminal
Where does an axon commonly terminate, and what does it form?
Terminates on a neuron forming a synapse
What is a synapse?
The site of signal transmission between neurons
Most synapses are ______
Chemical
Where are astrocytes found?
White and gray matter
What do astrocytes secrete?
Growth factors
What is the function of astrocytes?
Physical, metabolic, and structural support
What 3 types of cells make up glia?
1) Astrocytes
2) Oligodendrocytes
3) Microglia
What is the function of oligodendrocytes?
Provide myelin sheaths around axons
What are microglia?
Macrophages of the NS
What is the function of microglia?
Protect against viruses, bacteria, and tumor cells
When are microglia cells activated?
During inflammation in the CNS
What 2 types of cells make up the PNS?
1) Schwann cells
2) Satellite cells
What are Schwann cells?
Myelin producing cells of the PNS
What are satellite cells?
Support cells of the PNS found within ganglia
How many pairs of cranial nerves are there and where are they attached?
12 pairs attached to the brain
How many pairs of spinal nerves are there and where are they attached?
31 pairs attached to spinal cord
What does gray matter consist of?
Neuronal cell bodies and dendrites
What is gray matter the site of?
Synaptic connections
What makes up the surface of the brain?
Gray matter
What is a nucleus (CNS)?
A collection of neuronal cell bodies that have a similar function
What does white matter consist of?
Axons
What constitutes the “wiring” of the brain?
White matter
What is a fasciculus?
A bundle of axons of similar functions and connections
What is the corpus callosum?
The largest fasciculus that connects the left and right cerebral hemispheres
What are the 3 main sections of the brain?
1) Forebrain
2) Midbrain
3) Hindbrain
What are 2 main principles of the NS?
1) Bilateral symmetry and “decussations”
2) “Maps” within the brain
What are decussations?
Descending motor tracts that start on the right and cross over to the left
What is the sensory homunculus?
A sensory map of the body in the rain that includes pain, temp., touch, proprioception, and vibration
What is the largest section of the brain?
Forebrain
What is the forebrain divided into?
Telencephalon (cerebrum) and diencephalon
What is the midbrain?
Short, narrow “stalk” that connects forebrain and hindbrain
What 3 sections does the hindbrain consist of?
1) Pons
2) Cerebellum
3) Medulla
What does the telencephalon consist of?
- Cerebral cortex (gray matter)
- White matter (axons)
- Ventricles
- Basal ganglia / nuclei
What are the 4 lobes of the brain?
1) Frontal
2) Parietal
3) Temporal
4) Occipital
What does functional localization mean?
Different sites of the brain have different functions
What does “contralateral nature of motor and sensory cortex” mean?
Left brain corresponds to right brain and vice versa
What is the cerebral cortex connected to?
Thalamus and spinal cord
What does the frontal lobe control?
Movements, behaviour, speech, and decision making
What separates the frontal and parietal lobe?
Central sulcus
What is the site of the primary motor cortex?
Pre-central gyrus
What is the pre-central gyrus responsible for?
Activating motor neurons of the spinal cord on the opposite side of the body
What is the site of the primary somatosensory cortex?
Post-central gyrus
What does the parietal lobe control?
Somatosensory info – pain, temperature, proprioception, and interpretation of sensory input
What separates the parietal and occipital lobes?
Parietoccipital sulcus
What is the site of the primary visual cortex?
Gyri on medial surface of occipital lobe
What is the site of the primary auditory cortex?
Gyri on floor of lateral sulcus of temporal lobe
What is the site of the primary olfactory cortex?
Inferior surface of temporal lobe
What lobe is the hippocampus contained within?
Temporal
What is the function of the hippocampus?
Memory formation
What is the function of basal nuclei?
Regulate motor activity
What is the diencephalon?
Area between cerebrum and midbrain
What does the diencephalon make up?
Thalamus and hypothalamus
What does the diencephalon form and where?
The wall of the 3rd ventricle between the 2 lateral ventricles of the cerebral hemispheres and 4th ventricle
What is the MOTOR function of the diencephalon?
Regulates motor activity via connections with basal nuclei and cerebral cortex
What part of the brain regulates autonomic NS activity?
Hypothalamus
Where is all sensory info (except smell) processed and then where is it relayed?
Processed in thalamus and relayed to cerebral cortex
What 2 cranial nerves are found in the midbrain?
CN 3 (occulomotor) and CN 4 (trochlear)
What is the midbrain the site of?
Substantia nigra and reticular formation
What is the reticular formation important for?
Consciousness and arousal
What makes up the brainstem?
Midbrain, pons, and medulla
What is the largest section of the hindbrain?
Pons
What is the pons made up of?
- Fibres
- Cranial nerve nuclei and RF
- Pontine nuclei
What is the medulla made up of?
- Fibres
- Cranial nerve nuclei (9, 10, and 12)
- Reticular formation
Where is the brainstem located?
Between diencephalon and spinal cord
Where is the brainstem connected to the diencephalon?
Anterior margin of tentorium cerebelli
What 3 things does the brainstem contain?
1) Fibre tracts (white matter)
2) Cranial nerve nuclei (gray matter)
3) Other nuclei related to cerebellar function and consciousness
What is the cerebellum important for?
Maintaining equilibrium and fine motor coordination
What are the 3 membranous layers that cover the brain and spinal cord?
1) Dura mater
2) Arachnoid mater
3) Pia mater
What are the functions of the membranous layers?
Protection and compartmentalization of cranial cavity
What is dura made of?
Collagen
What is dura close to?
Bone
What is arachnoid close to?
Dura
What is the size of the layer of dura in the cranium?
Dense
What is the size of the layer of arachnoid in the cranium?
Thin
What is the thinnest and innermost layer of the membranous layers?
Pia
What kind of space are the cranial epidural and subdural spaces?
A potential space
What is the cranial epidural space inbetween?
Dura and skull
What is the cranial subdural space inbetween?
Dura and arachnoid
What is epidural hematoma?
When the middle meninigeal artery lies between dura and skull, which will leak blood and cause dura to separate from skull
What is subdural hematoma?
When vessles passing between arachnoid and dura leak blood into subdural space
Where is the subarachnoid space?
Between arachnoid and pia
What is the subarachnoid space filled with?
Cerebrospinal fluid (CSF)
Are blood vessels present in the subarachnoid space?
Yes
How many cavities are there in the ventricular system and what are they filled with?
4 cavities filled with fluid
What drains into the 3rd ventricle and through what?
- 2 lateral ventricles
- Through inter-ventricular foramina
What drains into the 4th ventricle and through what?
- 3rd ventricle
- Through midline cerebral aqueduct
What parts of the brain make up the floor of the 4th ventricle?
Pons & medulla
What part of the brain makes up the roof of the 4th ventricle?
Cerebellum
What part of the brain makes up the wall of the 3rd ventricle?
Diencephalon
What is the flow of the ventricular system?
2 lateral ventricles into midline 3rd ventricle, which drains into 4th ventricle via cerebral aqueduct
What does the 4th ventricle drain into?
Subarachnoid space
What produces cerebralspinal fluid?
Choroid plexus
How much CSF is produced per day?
About 500 mL
What is the choroid plexus?
Highly vascularized tissue found within all 4 cerebral ventricles
What does CSF look like and where is it derived from?
Clear fluid derived from plasma of the choroid plexus
What is the choroid plexus made of?
Specialized epithelial cells
How is CSF absorbed into the blood?
Arachnoid granulations in venous sinuses
What is hydrocephalus caused by?
CSF production being greater than absorption
What are 3 functions of CSF?
1) Provide protection and buoyancy to brain
2) Maintain consistency of environment for brain tissue
3) Remove cellular waste
How is CSF drained, and where is it drained from and to?
Drained by arachnoid villi from subarachnoid space into venous sinuses
What are arachnoid villi?
Tufts of arachnoid that extend through dura into venous sinus
What is the function of CSF?
Transport CSF from villi and granulations into venous blood
When does production of CSF stop?
Never
Where are arachnoid villi most numerous?
Superior sagittal sinus
What supplies oxygen to the brain?
Internal carotid and vertebral arteries
Does the internal carotid provide anterior or posterior oxygen circulation?
Anterior
Do the vertebral arteries provide anterior or posterior oxygen circulation?
Posterior
Where does the internal carotid provide circulation?
Telencephalon and diencephalon
Where do the vertebral arteries provide circulation?
Cervical spinal cord, brainstem, cerebellum, occipital and temporal lobes, and posterior and inferior cerebrum
What are the 3 major branches of the internal carotid?
1) Posterior communicating
2) Anterior cerebral
3) Middle cerebral
What does the posterior communicating branch do?
Connects anterior and posterior arterial supplies
Where is the anterior cerebral branch found?
Medial and superior surfaces of frontal and parietal lobes
What connects the 2 anterior cerebral branches?
Anterior communicating
What can be caused by an occlusion of the anterior cerebral?
Sensory and motor deficits of the lower limbs of the contralateral body
Where is the middle cerebral branch found?
Lateral cortical and sub cortical areas
What does the middle cerebral branch do?
Supplies large portion of motor and pre-motor areas in the frontal, parietal, and temporal lobes
What may be caused by an occlusion of the middle cerebral branch?
Sensory and motor deficits in the upper limbs and head of the contralateral body
What do the vertebral arteries enter, and what do they form once in?
Enter cranium and form the single basilar artery
What does the basilar artery ascend along?
Pons
What does the basilar artery split into?
Left and right posterior cerebral arteries
What do the posterior cerebral arteries supply?
Occipital lobe and inferior surface of temporal lobe
What connects the posterior cerebral and anterior circulation arteries?
Posterior communicating artery
What is the anterior spinal artery?
Midline artery that descends along the anterior medial sulcus of the medulla and spinal cord
What does the CNS require for neurons to stay alive?
Uninterrupted flow of blood and constant energy
What causes a stroke?
Interrupted blood supply to the brain
What system are typically involved in strokes?
Arterial system
What is an ischemic stroke?
An occlusion of vessel
What is a hemorrhagic stroke?
When a vessel bursts; involves smaller vessels under chronic hypertension
What is a sinus?
A channel carrying deoxygenated blood to internal jugular veins
What is a sinus functionally similar to?
A vein
Where does all venous blood in the brain drain into?
A venous sinus
What is a difference between sinuses and arteries?
Sinuses have lower pressure than arteries
What are the 3 midline sinuses that carry the majority of the brains venous blood?
1) Superior sagittal sinus
2) Inferior sagittal
3) Straight sinus
Where is the superior sagittal sinus?
Superior margin of falx cerebri
Where is the inferior sagittal sinus?
Inferior margin of falx cerebri
What does the inferior sagittal sinus flow into?
Straight sinus
Where is the straight sinus?
Junction of falx cerebri and tentorium cerebelli
What are the 3 major paired sinuses?
1) Transverse sinus
2) Inferior petrosal sinus
3) Sigmoid sinus
What does the sigmoid sinus join with and what does it form?
Joins with inferior petrosal to form internal jugular vein
What do superficial cerebral veins drain into and what is the rest of the flow?
Drain into superior sagittal sinus –> confluence of sinuses –> transverse sinus –> sigmoid sinus –> internal jugular
What is the function of the internal jugular vein?
Drain blood from the brain and return it to the heart
What do the deep cerebral veins drain into and what is the rest of the flow?
Drain into inferior sagittal sinus –> straight sinus –> transverse sinus –> sigmoid sinus –> internal jugular
How many cranial nerves are there and what do they innervate (grand scheme)?
12 pairs that innervate head and neck, as well as thorax and abdomen
Which cranial nerves arise from the midbrain?
3 - occulomotor & 4 - trochlear
Which cranial nerves arise from the pons?
5 - trigeminal, 6 - abducens, 7 - facial, & 8 - vestibulocochlear
Which cranial nerves arise from the medulla?
9 - glossopharyngeal, 10 - vagus, 11 - spinal accessory, & 12 - hypoglossal
What is an acronym to remember the cranial nerves?
Oh Once One Takes The Anatomy Final Very Good Vacations Are Heavenly
Which cranial nerves have only sensory functions?
1 - olfactory, 2 - optic, and 8 - vestibulocochlear
Which cranial nerves have only motor functions?
3 - occulomotor, 4 - trochlear, 6 - abducens, 11 - spinal accessory, & 12 - hypoglossal
Which cranial nerves have sensory and motor functions?
5 - trigeminal, 7 - facial, 9 - glossopharyngeal, & 10 - vaugs
What is the function of the olfactory nerve?
Carry olfactory info from olfactory epithelium through the foramina of cribiform plate
What is the function of the optic nerve?
Carries visual info from retina through optic canal
What is the function of the vestibulocochlear nerve?
Carries balance and hearing from inner ear (cochlear and vestibular apparatus) through the internal auditory meatus
What is the function of the occulomotor nerve?
Innervate intrinsic muscles and 4 of the 6 extrinsic muscles of the eye
What is the function of the trochlear nerve?
Innervate superior oblique (pulls down eye when adducted)
What is the function of the abducens nerve?
Innervate lateral rectus (abducts eye)
What is the function of the spinal accessory nerve?
Innervate steinocleidomastoid (rotate head) and trapezius (shrug shoulders)
What is the function of the hypoglossal nerve?
Innervate intrinsic and extrinsic muscles of tongue (sticking out tongue)
What does the spinal accessory nerve leave the cranium through?
Jugular foramen
What does the hypoglossal nerve leave the cranium through?
Hypoglossal canal
What are the 3 branches of the trigeminal nerve and what is its simplified function?
- Somatosensation of the face
1) Ophthalmic nerve
2) Maxillary nerve
3) Mandibular nerve
What is the function of the ophthalmic branch of the trigeminal nerve?
Somatosensory from cornea, nose, and forehead
What is the function of the maxillary branch of the trigeminal nerve?
Somatosensory from maxilla, upper lip, teeth, and hard palate
What are 2 functions of the mandibular branch of the trigeminal nerve?
- Somatosensory from mandible, lower lip, teeth, and anterior 2/3 of tongue
- Motor to muscles of mastication (chewing)
What is the sensory function of the facial nerve?
Taste and anterior 2/3 of tongue
What are the motor functions of the facial nerve?
- Muscles of facial expression
- All glands of face / oral cavity EXCEPT PAROTID
What is the sensory function of the glossopharyngeal nerve?
Taste and somatosensation of posterior 1/3 of tongue
What are the motor functions of the glossopharyngeal nerve?
- Assist in swallowing
- Parotid gland
What are the sensory functions of the vagus nerve?
- Taste (epiglottis)
- Visceral sensory from respiratory tract and viscera
What are the motor functions of the vagus nerve?
- Swallowing and speech
- Respiratory tract, heart, esophagus, and intestines
How many layers of meninges are there and what are they called?
3
1) Dura mater
2) Arachnoid
3) Pia mater
List the meninges layers from outermost to innermost
Dura, arachnoid, pia
At what vertebrae does the dura end?
S2
What does dura look & feel like?
Tough, fibrous, and continuous with dura of brain
Where is the REAL epidural space, and what does it contain?
- Between dura and vertebral bones
- Contains connective tissue, fat, and veins
What is the arachnoid meninge layer adherent to?
Dura
At what vertebrae does the arachnoid end?
S2
Where is the subarachnoid space and what does it contain?
- Between arachnoid and pia
- Contains CSF
What is the lumbar cistern and what is it used for in medicine?
- Space between L1 and S2
- Used to get a sample of CSF without possibility of damaging the spinal cord
What does pia mater adhere to?
Spinal cord
At what vertebrae does the pia end at?
S2
What makes up the sac that contains the spinal cord?
Dura
What is dura NOT attached to?
Vertebral bones
What kind of ligaments attach spinal cord to dural sac?
Denticulate ligaments
Where does the dura sac begin and end?
- Begins at foramen magnum
- Ends at S2
At what vertebrae does the spinal cord end?
L1 - L2 (the conus medullaris)
What is the cauda equina?
Lumbar, sacral, and coccygeal nerve roots that extend to exit the dural sac
What tethers the end of the spinal cord to dural sac?
Filum terminale (extension of pia)
What is the cervical enlargement and between which vertebrae is it found?
- Site of innervation of arm
- C4 - T1
What is the lumbosacral enlargement and between which vertebrae is it found?
- Site of innervation of leg
- L2 - S3
Describe the differences between roots in the cervical region and roots in the lumbosacral region
- Roots in cervical region are short and horizontal
- Roots in lumbosacral region are long and vertical (cauda equina)
What is the function of the dorsal horn?
It processes and relays sensory info to the brain
How does sensory information enter the spinal cord?
Dorsal root
What kinds of fibres does the dorsal root contain?
Afferent (sensory)
Where are ALL cells bodies of sensory neurons located?
Dorsal root ganglion
What is the function of the ventral horn?
Projects signals to muscle through large motor neurons via the ventral root
What are motor neurons innervated by?
Descending fibres carried in white matter
What does white matter consist of?
Nerve fibres, neuroglia, and blood vessels
Why does white matter appear white?
Fibres are myelinated
What 3 locations do fibres arise from?
Cell bodies in:
1) Brain
2) Spinal cord
3) Periphery
What kind of axons do fibres in the brain contain?
Descending axons from cerebrum and brainstem
What kind of axons do fibres in the spinal cord contain?
Ascending axons from gray matter
What kind of axons do fibres in the PNS contain?
Ascending axons from dorsal root ganglion
What direction does sensory info travel?
Up the cord to the brain
What area of the spinal cord will have the greatest number of sensory fibres?
Top
What direction does motor activity travel?
Down the cord to the neurons in the gray matter
What area of the spinal cord will have the greatest number of motor fibres?
Top
What does gray matter mainly consist of?
Neuronal cell bodies and neuroglia
How many pairs of spinal nerves are there?
31
Describe the path of spinal nerves
Leave spinal cord, pass through intervertebral foramen, and exit as peripheral nerves
How many pairs of cervical spinal nerves are there?
8
How many pairs of thoracic spinal nerves are there?
12
How many pairs of lumbar spinal nerves are there?
5
How many pairs of sacral spinal nerves are there?
5
How many pairs of coccygeal spinal nerves are there?
1
What attaches spinal nerves to the cord?
A ventral root and a dorsal root
What innervates skeletal muscle?
Motor neurons (cell bodies in the ventral horn)
How do action potentials enter the CNS?
Dorsal roots of spinal nerves
Name 3 stimuli that the sensory system is capable of detecting
1) Mechanical
2) Pain
3) Temperature
What are 2 examples of mechanoreceptors?
1) Neuromuscular spindles
2) Golgi tendon organs
What do neuromuscular spindles detect?
Changes in length
What do golgi tendon organs detect?
Tension in tendons
Where are cell bodies of sensory neurons of the PNS found?
Dorsal root ganglion
What structures are supplied by spinal nerves?
Myotomes and dermatomes
Is a spinal nerve sensory, motor, or mixed?
Mixed
What are myotomes?
Muscles innervated by motor fibres of a spinal nerve
What is a dermatome?
An area of skin innervated by sensory fibres of a spinal nerve
Name 2 consequences of peripheral nerve injury
1) Muscle degeneration
2) Loss of sensitivity in a dermatome
What are 3 target tissues of the autonomic nervous system?
1) Cardiac muscle
2) Smooth muscle
3) Glands
What is the cell body of the first neuron in the CNS referred to as?
Pre-ganglionic neuron
What is a ganglion the site of?
Connection between the pre- and post-ganglionic neuron
What are the 2 divisions of the ANS, and do they have similar or opposing functions?
1) Sympathetic
2) Parasympathetic
- Opposing
When is the sympathetic nervous system activated?
During the “fight or flight” response
Where are pre-ganglionic cell bodies of the sympathetic NS located?
Thoracic and lumbar segments of spinal cord
Where are pre-ganglionic cell bodies of the parasympathetic NS located?
Brainstem and sacral levels of spinal cord
Where are parasympathetic ganglia located?
Near the target tissue
When is the parasympathetic NS most dominant?
At rest
What happens when both the branches of the ANS innervate a muscle?
One branch will cause contraction and the other will causes relaxation
What part of the brain is a major regulator of the ANS?
Hypothalamus
