Nervous System Flashcards
How is the nervous system divided?
CNS: brain and spinal cord
PNS: peripherals (everything else)
What are the functional divisions of NS?
Sensation (sensory functions)
Response (motor functions)
What is the somatic NS?
Responsible for conscious perception and voluntary motor responses
What is the autonomic nervous system?
Responsible for involuntary control of the body, usually for homeostasis.
Describe grey and white matter
Grey matter: cell bodies and dendrites
White matter: axons (+myelin)
Define nucleus in NS
Localised collection of neuronal cell bodies in CNS
Define ganglion
Cluster of neuronal cell bodies in PNS
Describe nerves/tracts
Tract: bundle of axons or fibres found in CNS
Nerve: same thing but in PNS
What is the dura mater?
- outermost meninx; thick and dense inelastic membrane
- Encloses entire CNS and major blood vessels that enter cranium and vertebral cavity
- Directly attached to the internal (periosteal) surface of the bones of the cranium and to the most inferior part of the vertebral cavity.
What is the dura mater’s role in flow of CSF and blood?
Forms the walls of the venous sinuses of the cranium, allowing blood to drain from the brain and into internal jugular vein to return to the heart
What is the falx cerebri?
- Dural reflection
- Double layered shelf of dura projecting into longitudinal fissure of the brain that partially seperates the cerebral hemispheres
What is the arachnoid mater?
Middle meninx; doesn’t extend into cerebral sulci
Named after the spider-web trabeculae between it and pia mater.
What is arachnoid mater’s role in CSF and blood flow?
- Trabeculae found in the subarachnoid space (filled with circulating CSF, cerebral arteries and veins)
- Small pockets of arachnoid protrude through dura mater to enter dural sinuses as arachnoid granulations
- CSF empties here into venous blood circulation for recycling
What is the pia mater?
- Delicate, deepest meninx
- Surface of brain and spinal cord covered by this
- Filum terminale at the end of spinal cord extends from inferior end of CNS at superior lumbar region of the vertebral column to the sacral end of the vertebral column to anchor the mobile spinal cord to the most inferior part of the vertebral canal.
What is the epidural space? Why is it important?
- adipose tissue filled space between dura mater and periosteal lining of vertebral canal.
- Important location for venous blood flow and is the site for epidural blocks (anaesthesia)
How is dura mater of the spine different to the brain?
Dura mater isn’t attached to bony wall of vertebral canal. Instead has epidural space.
What is the function of CSF?
- Removes metabolic wastes from interstitial fluids of nervous tissue and returns them to blood
- Acts as liquid cushion for brain and spinal cord
What are ventricles?
Open spaces within the brain where CSF circulates
What is the choroid plexus?
- Highly vascular structure, responsible for production of CSF
- Location: lateral ventricles, interventricular foramina, 3rd + 4th ventricle
How is CSF produced?
- In choroid plexus
- Ependymal cells surround blood capillaries and filter blood to make CSF
Describe 2 lateral ventricles
- Right and left
- Deep in each cerebral hemisphere
What is the interventricular foramina?
- 2
- Each foramen connects one lateral ventricle to 3rd ventricle
What is the third ventricle
- Deep, narrow, single ventricle located in midsagittal plane in space between R and L sides of diencephalon
What is the cerebral canal?
- Elongated canal that extends from 3rd ventricle to 4th ventricle
- Located in midbrain
What is the 4th ventricle?
- Most inferior
- Location: between pons and medulla oblongata anteriorly and cerebellum posteriorly
- Continuous with central canal
What is the central canal?
Thin passageway in the spinal cord.
What is the CSF Flow after ventricular system?
Flows from 4th ventricle inferiorly into central canal of spinal cord as well as posterolaterally through a number of small apertures that open up to subarachnoid space
What are the arachnoid villi/granulations? Where does the CSF go?
- Outpocketings of arachnoid mater through dura mater into superior sagittal sinus
- Allows CSF to flow from subarachnoid space into dural venous sinuses to return to venous blood circulation on its route back to the heart
- From dural sinuses, blood drains out of head and neck through internal jugular veins to be reoxygenated by lungs and wastes to be filtered out by kidneys
What’s the difference between arachnoid villi and granulations?
Arachnoid villi calcify with age and harden to become arachnoid granulations
What is the cerebrum?
Largest part of the brain. Seperated into 2 cerebral hemispheres. Cortex + several deep nuclei.
What is the cerebral cortex?
Thin layer of grey matter that makes up the wrinkled, external portion of the brain
What is the longitudinal fissure
Deep narrow groove that partly seperates the paired cerebral hemispheres
What is the corpus callosum?
- Band like structure immediately inferior to longitudinal fissure
- Consists of white matter that provides axonal communication between 2 hemispheres
What are the basal nuclei?
- Located deep within each cerebral hemisphere; surrounded by white matter
- Responsible for cognitive processing (e.g: planning movements)
What are the cerebral gyri and sulci?
Gyri: surface fold of cerebral hemisphere (grey + white matter)
Sulcus: groove between 2 gyri. Lined by pia mater.
Why is the brain folded?
- Pattern of these folds indicates specific regions of cerebral cortex
- Folding allows more SA of grey matter
Frontal lobe functions?
Motor functions, production of language and cognitive functions (personality, consciousness, short term memory)
Parietal lobe functions
Somatosensation (tactile, proprioception, kinesthesia)
Temporal lobe functions
Primary auditory sensation, memory and smell
Occipital lobe function?
Processing visual information
What is the diencephalon?
Consists of thalamus, hypothalamus and pineal gland surrounding the third ventricle
Describe the thalamus
- 2 large oval masses of grey matter located on either side of 3rd ventricle
- Function: relaying and processing information
Describe the hypothalamus
- Inferior and slightly anterior to thalamus
- Forms anterolateral part of the lateral walls of third ventricle
- Collection of nuclei that’s involved with regulating homeostasis
- Function: in charge of ANS and ES through its regulation of anterior pituitary gland
- Also involved in memory and emotion (limbic system)
What is the pineal gland?
- Location: In epithalamus. Superior part of posterior wall of 3rd ventricle
- Small endocrine gland that produces melatonin (sleep-wake cycles)
What is the brain stem
Connects the brain to spinal cord.
Describe the medulla oblongata
- Most inferior part of brainstem; continuous with spinal cord inferiorly
- Surrounds proximal part of central canal, and inferior part of 4th ventricle
- Function: regulates crucial functions like cardiovascular and respiratory systems and rates
Describe pons
- Central part of brainstem; forms anterior wall of 4th ventricle
- Function: main connection with cerebellum
Describe midbrain
- Most superior part of brainstem; continuous with diencephalon superiorly
- Surrounds cerebral aqueduct
- Function: coordinates sensory representations of visual, auditory and somatosensory perceptual spaces
Describe the cerebellum
Responsible for comparing info from cerebrum with sensory feedback from periphery through the spinal cord. About 10% mass of the brain
Why is the spinal cord not the full length of vertebral column?
because the spinal cord does not grow significantly longer after the first or second year, but the skeleton continues to grow. Extends from foramen magnum of skull -> L1/L2 region of vertebral canal
Describe cervical/lumbar enlargement
- Spinal cord is larger in these regions to allow for more room for the cell bodies of neurones to reside (highly innervated regions)
What are the horns?
- Grey matter of spinal cord; cell bodies + synapses
- Posterior (dorsal) horn: sensory neurones synapsing
- Anterior (ventral) horn: cell bodies of motor neurones (send motor signals to skeletal muscles)
- Lateral horns: cell bodies of sympathetic neurones (only in thoracic and upper lumbar regions)
What are ascending/descending tracts?
Ascending: carry sensory info up to the brain
Descending: carry motor commands from the brain
Example of descending tract
Corticospinal Tract
* Responsible for voluntary movments of skeletal muscles
* Look in book for more in depth
Example of ascending tract
Spinothalamic tract
* Responsible for pain and temperature sensations
* Periphery to contralateral thalamus for processing
Describe conus medullaris
conical-shaped caudal end of spinal cord.
contains coccygeal region.
What is the cauda equina?
“horse’s tail”
collection of nerve roots located in vertebral canal inferior to the spinal cord in adults.
How many cranial nerves are there and describe cranial nerves
12 cranial nerves
responsible for innervating structures of the head and neck
What is the olfactory nerve (CN I)
Sensory nerve responsible for carrying smell information from nasal epithelium.
Describe optic nerve (CN II)
thick sensory nerve responsible for vision
Describe oculomotor nerve (CN III)
motor nerve responsible for eye movements and the pupillary reflex by controller 4 of the extraocular muscles
Describe trigeminal nerve (CN V)
thick, mixed nerve
responsible for cutaneous sensations of the face and controlling muscles of mastication
Describe facial nerve (CN VII)
motor nerve responsible for muscles of facial expression. Also part of sense of taste and saliva production (autonomic)
Describe vestibulocochlear nerve (CN VIII)
sensory nerve responsible for hearing and balance
Describe vagus nerve (CN X)
mixed nerve contributes to the majority of the parasympathetic supply to the body (homeostatic control of organs of thoracic and superior abdominal regions)
Which cranial nerves contain autonomic fibres?
oculomotor, facial and vagus
Describe spinal nerves
- All are combined sensory and motor axons that seperate into 2 nerve roots
- 31 spinal nerves
Explain dorsal nerve root
- Sensory (unipolar) axons enter the spinal cord
- Contains dorsal root ganglion
Explain ventral nerve root
Motor fibres (both somatic and autonomic) emerge as ventral nerve root.
What is the dorsal root ganglion?
enlargement of the dorsal root of spinal nerve where cel bodies of sensory pseudounipolar neurones are located.
What is the body of the spinal nerve
- lateral to dorsal root ganglion
- formed from the union of dorsal and ventral nerve roots
- Divides into dorsal and ventral rami
What is the dorsal ramus of each spinal nerve
- smaller of the two rami
- innervates largely the organs of the back
What is the ventral ramus?
- larger branch of the body of the spinal nerve
- innervates most regions of the body anterior to the vertebral column
What is the intervertebral foramen?
Nerves are numbered from superior to inferior positions. Each emerges from the vertebral column through the intervertebral foramen at its level.
How many pairs of spinal nerves in each region?
Cerival: 8 pairs
Thoracic: 12 pairs
Lumbar: 5 pairs
Sacral: 5 pairs
Coccygeal: 1 pair
Total: 31 pairs
What is a peripheral nerve?
Arise from spinal nerve plexuses and carry sensory, motor and autonomic info to and from spinal nerve plexuses.
What is a nerve plexus?
Interlacing networks of the anterior rami of cervical, lumbar, and sacral spinal nerves.
What is the cervical plexus?
- Paired
- Formed by cervical spinal nerves
- Innervates posterior neck and head, and thoracic diaphragm (phrenic)
What is the brachial plexus
- Paired
- Formed from mainly cervical nerves (C4-T1)
- Innervates upper limb (median)
What is the lumbar plexus
- Paired
- formed by lumbar spinal nerves
- Innervates anterior and medial compartments of thigh (femoral nerve)
Describe phrenic nerve
- Descends down the neck, anterior to scalenus anterior muscle, through thoracic region to innervate thoracic diaphragm
- Arises mainly from cervical plexus
Describe median nerve
- Arises from brachial plexus
- Located in median part of the cubital and antebrachial regions
- Innervates most muscles of anterior antebrachium and palmar region
Describe femoral nerve
- Located in pelvic cavity and siperior part of anterior region of the thigh
- arises from lumbar plexus
Desribe sciatic nerve
- Largest diameter nerve in the body
- Passes through the greater sciatic foramen to enter posterior region og the thigh
- Arises from sacral plexus
Whats the basic unit of ANS?
2 motor neurones (pre and post ganglionic neurones) which synapse in a ganglion
How does the ANS work?
- Cardiac muscle, smooth muscle of tubular organs and most glands are innervated by both subdivisions
- For each tissue, one has an excitatory function while the other has inhibitory function
What are innervated only by sympathetic system?
Sweat glands, vessels and adrenal (suprarenal) glands
Describe the parasympathetic system
- Rest and digest
- Has a craniosacral outflow from the CNS, meaning the cell bodies of their preganglionic neurons are located in the brainstem and travel with cranial nerves or in the sacral part of the spinal cord.
- Long pregan. and short postgan. (bc parasym. ganglia located close to their target organ)
Describe sympathetic nervous system
- Fight or flight
- has a thoracolumbar outflow from the CNS, meaning the cell bodies of their preganglionic neurons are located in the thoracic and upper lumbar parts of the spinal cord.
- Located in lateral horns (hence why only found in T and UL regions)
- Characterised by short preganglionic axons and long postganglionic axons owing to the location of sympathetic ganglia close to the spinal cord.
Describe sympathetic chain/trunk
- Allows axons of pregan. neurones to travel to more superior and inferior levels of the body
- Elongated, paired structure
- Location: anterolateral to vertebral column
What are sympathetic chain ganglia
- Interdispersed along sympathetic chain
- Contain synaptic connections of pregan neurones with the cell bodies of post gan.
Label diencephalon
