Nervous System Flashcards
2 divisions of the nervous system
- central nervous system (CNS)
- peripheral nervous system (PNS)
Central nervous system consists of
brain and spinal cord
Central nervous system functions
processes and integrates info
Peripheral nervous system consists of
- cranial nerves
- spinal nerves
Cranial nerves go to and from the.. and spinal nerves go to and from the ..
- brain
- spine
Nerves detect changes in the ..
surrounding environment (stimuli) then transported to information to the CNS to process
2 divisions of the peripheral nervous system
- sensory division
- motor division
Sensory/afferent division
consists of afferent neurons. receptors that detect stimuli and transmit the information to the CNS
Motor/efferent division
consists of efferent neurons. the CNS produces a response that is sent to effectors (muscles cells and glands)
Motor division of PNS consists of ..
somatic and autonomic divisions
Relationship between CNS and PNS
receptors–> PNS (afferent)–> CNS –> PNS (efferent)–> effector glands or muscles
2 nervous system cell types
- neurons
- neuroliga (glial cells)
Impulses
electrical signals generated as a result of nervous system stimulation
Neurons functions to
integrate and store information. they conduct electrical impulses (15% of total brain cells)
Neurons are incapable of..
mitosis. so when dead are irreplaceable. (except for taste, olfaction neurons)
Cell body of neuron
typical organelles except centrioles. Rough endoplasmic reticulum called nissl bodies
Dendrites
short branching projections from body. receive incoming messages and relay to cell body
Axon
extends from the neuronal cell body. generates and transmits nerve impulses.
Axon hillock
where the axon meets cell body
Axon ends at the ..
axon terminal. which contains synaptic end bulbs
Axon may be..
- myelinated
- unmyelinated
Myelinated
wrapped in many layers of cell membrane (myelin) from Schwann cells (PNS) or oligodendrocytes (CNS)
Nodes of Ranvier
gaps in myelin sheath
Myelinated axon cells are
electrical insulation
Myelinated neurons are called …
- CNS= tracts (white matter)
- PNS=nerves
Unmyelinated
no myelin around axon
Neuroglia (glial cells).
function to support the neurons, capable of mitosis (85% of all cells in brain)
Types of neuroglia cells
- CNS neuroglia
- PNS neuroglia
4 types of CNS neuroglia cells
- oligodendrocytes
- microglia
- astrocytes
- ependymal
Oligodendrocytes
produce myelin around axon
Microglia
protective and become phagocytic if detect infected dead or damaged neurons
Astrocytes
surround blood capillaries to form part of blood brain barrier
Ependymal
line cavities in CNS, brain ventricles and spinal canal
Ependymal secrete..
cerebrospinal fluid (CSF) and circulate it
2 typess of PNS neuroglia cells
- schwann cells
- satallite cells
Schwann cells
form myelin around axis of PNS
Satellite cells
surround neuron cell bodies in ganglia
Unipolar neurons
1 process that divides into 2 central and peripheral, always sensory
Bipolar neurons
2 processes, 1 axon 1 dendrite, sensory neurons (retina and nose)
Multipolar neurons
3 or more processes, 1 axon many dendrites. all interneurons and motor neurons
Structural/anatomical types of neurons are based on
number of cell processes off of cell body
Functional types of neurons are based on
direction of impulse conduction (toward CNS or away from CNS)
Sensory/afferent neurons are…
unipolar. impulses collected by sensory receptors move toward the CNS
Interneurons
transmit impulses within CNS, 99% of neurons. located between sensory and motor neurons. most are multipolar
Motor/efferent neurons move impulses from ….
CNS to effectors (all multipolar)
3 types of primary synapses
- neuronal synapses
- neuromuscular junction
- neuroglandular junction
Neuronal synapses
junction occurs between two neurons, can be chemical or electrical
Neuromuscular junction
junction between motor neuron to sarcolemma of skeletal muscle cell
Neuroglandular junction
junction between motor neuron to gland
Chemical neuronal synapses structure
- presynaptic neuron
- axon terminal
- synaptic cleft
- postsynaptic neuron
Presynaptic neuron brings ..
in the signal
Pre synaptic neurons contains
axon terminal with synaptic end bulbs
Synaptic end bulbs contain ..
neurotransmitters –> chemical messages released upon a stimulus
Post synaptic neuron receives ..
the signal on the dendrites
Post synaptic membrane on dendrites contain
specific receptors for the neurotransmitter that was release from the pre synaptic membrane
Protective features of CNS
- bone
- meninges
- cerebrospinal fluid (CSF)
- blood brain barrier (BBB)
- circle of willis
Bone in CNS
skull and vertebral column
Meninges
CT membranes that surround the brain and spinal cord
Layers of meninges
- duramater (outer)
- arachnoid
- pia mater (inner)
Dura mater around the brain
- consists of two layers mostly fused.
- in some areas it is separated and filled with nexus blood (separated areas are called dural sinus)
2 spaces of the Dura mater around the spinal cord
- space between the dura mater and the vertebral canal is called the epidural space
- subdural space is between the dura mater and arachnoid mater
Subdural space is filled with
ISF
Epidural space is filled with
fat, blood vessels, CT (spinal cord only)
Arachnoid mater
beneath the subdural space, avascular, has subarachnoid space and arachnoid villi
Subarachnoid space
filled with CSF, web like strand of CT from arachnoid mater into subarachnoid space
Arachnoid villi
project into dural sinuses in order to deliver CSF into blood (brain only)
Pia mater
vascular layer directly on top of brain and spinal cord
Meningitis
inflammation of meninges
Cerebrospinal fluid
fluid located in and around CNS. provides insulation to the brain and allows the brain to float within the cavity (reduces weight)
CSF in brain ___ and central canal of ___ ___
ventricles; spinal cord
4 ventricles in brain located …
- 2 lateral ventricles in cerebrum
- 1 in diencephalon
- 1 in hindbrain
- central canal of the spinal cord is also included
CSF similar composition to ..
blood plasma
CSF produced by..
choroid plexuses found in each ventricle
Blood brain barrier (BBB)
Allows for only certain materials to pass through (mainly fat soluble ex: glucose) located throughout most parts of the brain
2 cell types of BBB
- endothelial cells w/ tight junctions
- astrocytes
Astrocytes of BBB
foot processes wrap around endothelial cells
Circle of Willis
cerebral arteries located at base of forebrain, allows continuous flow of blood too brain but provides alternate route for blood if vessels blocked. blood pressure remains constant
Circle of willis two internal carotid arteries deliver blood to ..
- midle cerebral artery (*not part of circle)
- anterior cerebral arteries
- posterior communicating arteries
Circle of willis merge the two vertebral arteries with the ..
basilar artery which then merges with the posterior cerebral arteries (which carry blood from occipital lobe and temporal lobe)
Forebrain consists of
cerebrum and diencephalon
Cerebrum
largest portion of the brain. consists of two hemispheres separated from one another by longitudinal fissure
5 Cerebrum lobes and function (named after overlying bones)
- frontal (motor)
- temporal (memory)
- parietal (sensory)
- occipital (visual)
- insula (visceral sensation)
Surface features of cerebrum
- fissures
- gyro
- sulci
Fissures are..
deep grooves
2 fissures of forebrain
- longitudinal
- transverse
Longitudinal fissures
separates right and left cerebral hemispheres
Transverse fissure
separates cerebellum and cerebrum
What are gyri and two gyri of cerebrum
elevated folds over most of the brain (separated by sulcus)
- precentral gyrus in frontal lobe
- postcentral gyrus in parietal lobe
What are sulci and two sulcus of cerebrum
shallow grooves
- central sulcus separate frontal and partial lobe
- lateral sulcus separate temporal from rest of cerebrum
Each cerebral hemisphere consist of three main regions
- cerebral cortex
- white matter
- basal nuclei
Cerebral cortex is..
2-4 mm thick grey matter
3 functional areas of cerebral cortex
- motor areas
- sensory areas
- association areas
Motor areas of cerebral cortex
in the frontal lobe, control skeletal muscle movement
3 regions of motor areas of cerebral cortex
- primary motor area (on precentral gyrus)
- premotor area (anterior to precentral gyrus)
- Broca’s area controls speech muscles (in only 1 hemisphere)
4 sensory areas of cerebral cortex
- general sensory area for pain temperature and touch (in postcentral gyrus in parietal lobe)
- vision (occipital lobe)
- auditory and olfaction (temporal lobe)
- taste and visceral sensation (insular lobe)
Associated ares of cerebral cortex
- allows recall/recognition of information stored in memory (temporal lobe)
- intellect (frontal lobe)
3 tracts/white matter of cerebrum
- association tracts
- commissural
- projection tracts
Association tracts
transmit information from gyrus to gyrus in same hemisphere
Commissural tracts
transmit information from gyrus to gyrus in opposite hemisphere (corpus callosum)
Projection tracts run..
vertically (transmit information from brain to spinal cord and vice versa)
Basal nuclei of cerebrum
paired masses of grey matter located in the white matter of cerebrum. control skeletal muscle movement
Diencephalon
all grey matter, consists of thalamus and hypothalmus
Thalamus
2 lobes connected by intermediate mass (bridge of gray matter) located superior to midbrain. relay station for sensory impulses coming to cortex
Hypothalamus
inferior to thalamus, above pituitary gland. major regulator of the internal environment (blood pressure) and has endocrine and nervous function
Midbrain
connects pons and diencephalon, contains cerebral aqueduct.
Anterior portion of midbrain contains
projection tracts called cerebral penduncles
Posterior portion of midbrain
4 nuclei called corpora quadrigemina
4 nuclei of posterior portion of midbrain
- 2 superior colliculi (visceral reflexes that allow movement of the head and eyes)
- 2 inferior colliculi (auditory reflexes)
Hindbrain consists of
pons, cerebellum and medulla
Pons
anterior to cerebellum, connects medulla to the midbrain. tracts between brain and spinal cord. forms portion of the 4th ventricle
Pons is home to the
pontine respiratory centres (pontine nuclei) assists in medulla in maintaining normal breathing rhythms
Medulla oblongata
forms part of 4th ventricle. begins at the foramen magnum and blends brain into the spinal cord.
Medulla has two pyramids which are large motor tracts (part of corticospinal tracts) which ..
decussate just prior to start of the spinal cord. cross to opposite side of the body (which is why the brains controls opposite sides of the body)
Medullar oblongata contains nuclei for 4 cranial nerves:
- IX: glosspharyngeal
- X: vagus
- XI: accessory
- XII: hypoglossal
Medulla contain nuclei for vital centres including
- cardiac (contraction and heart rate)
- vasomotor (blood vessel diameter)
- respiratory (rate and depth of breathing)
Several non vital centres in medulla for..
swallowing, sneezing, vomiting, coughing
Brain stem comprised of ..
midbrain, pons, medulla
Cerebellum
located in dorsal portion of brain (posterior to pons and medulla). contains folia which are folds. functions to regulate skeletal muscle, posture balance.
Cortex of cerebellum is formed from ..
grey matter
Arbor vitae of cerebellum =
deep within the cortex is white matter
Limbic system function and location
functions to regulate emotions and emotional behaviours. network of nuclei located in cerebrum and diencephalon
Reticular formation function and location
functions to keep you alert and attentive. inhibition of this area results in sleep. located in brain stem
Sleeping pills and anesthetics affect what area
reticular formation`
If reticular formation damaged results in
coma
Cauda equina
nerves that exist below the conus
Filum terminale is formed from ..
CT extension of pia mater (anchors conus to coccyx)
Spinal cord functions to ..
take in sensory information and generate motor output (reflexes)
Cross sectional structure of spinal cord consists of left and right halves..
- anterior median fissure (ventral side)
- posterior median sulcus (dorsal side)
- central canal (middle of the cord)
Central canal contains
CSF
Grey matter contains ..
cell bodies and dendrites of motor neurons and interneurons
Grey matter is H shaped with
- cross bar = grey commissures
- horns
Horns in grey matter
- dorsal horn = sensory info
- ventral and lateral horn = motor output
White matter contains ..
myelinated axons of ascending (sensory) or descending (motor) tracts
3 columns of white matter
- dorsal
- lateral
- ventral
Structures of PNS
- cranial nerves
- spinal nerves
- cross section of a nerve
__ pairs of cranial nerves
12
12 cranial nerves are
- olfactory |
- optic ll
- oculomotor lll
- trochlear lV
- trigeminal V
- abducens Vl
- facial Vll
- vestibulocochlear Vlll
- glossopharyngeal lX
- vagus X
- accessory Xl
- hypoglossal Xll
Mnemonic for cranial nerves
oh once one takes the anatomy final very good vacations are had
3 pairs of cranial nerves that are only sensory neurons
optic, olfactory, vestibulochlear
9 pairs that are mixed nerves
carry both sensory and motor nerons
Spinal nerves
31 pair of nerves, all mixed sensory and motor
Pairs of spinal nerves
- 8cervical
- 12thoracic
- 5lumbar
- 5sacral
- 1coccygeal
Each spinal nerves has 2 points of attachment to spinal cord
- dorsal root
- ventral root
Dorsal root
receives sensory information; cell bodies are in dorsal root ganglion
Ventral root
carries motor output; cell bodies in ventral or lateral horns
Spinal nerves located at
joint of dorsal and ventral root
Spinal nerve immediately divide into branches =
rami
3 rami
- dorsal ramus
- ventral ramus
- rami communicates
Dorsal ramus
innervate skin and muscles of back
Ventral ramus
innervate the thoracic nerves T1-T12 and the plexuses
4 plexus
- cervical C1-C4: phrenic nerve (diaphragm)
- brachial C5-T1: axillary, radias, ulna, median nerves
- lumbar L1-L5: femoral nerve
- sacral L4-S4: sciatic nerve (tibial and fibular nerves)
All but the first spinal nerve leave through the ..
intervertebral foramina of the vertebrae
Rami communicates contain form a component of the ..
autonomic nervous system
3 CT wrappings around nerves are..
- entire nerve wrapped in epineurium
- each nerve fascicle is wrapped in perineurium
- each axon and myelin is wrapped in endoneurium
PNS sesnory (afferent) divison
stimulus– receptor– CNS
Receptors
detect changes in environment
Receptors are classified by 3 things:
- location
- type of stimulus
- structure
2 locations of receptors
- exteroceptors
- interoceptors
Exteroceptors
detect stimulus in external environment or very close to body surface. (in skin for pain, touch)
Interoceptors
detect stimulus in internal environment (blood pressure)
Proprioceptors are specifically located in
in joints and skeletal muscles
4 types of stimulus received by receptors
- mechanoreceptors (detect touch and pressure)
- thermoreceptors (detect temp)
- chemoreceptors (detect chemicals)
- photoreceptors (detect light)
Structure of receptor consists of
- free nerve endings
- encapsulated nerve endings
Free nerve endings
dendrites of sensory neurons (pain, root hair)
Encapsulated nerve endings
terminal dendrites enclosed in CT (meissners corpuscles
First order neurons
unipolar neuron containing receptors. located in spinal nerve. part of PNS
First order neurons cell bodies in
ganglia outside of the CNS
First order neurons synapse into second order neurons in the ..
-dorsal horn of spinal cord or brain stem
2 subdivisions of motor division
- somatic
- automanic
Somatic subdivision of PNS effector cells are all ..
skeletal muscle
Somatic motor pathways consists of 2 neurons
upper and lower motor neurons
Single multipolar neurons
- cell bodies in ventral horn of SC to effector
- cell bodies in motor nuclei of brainstem to effector
Autonomic effector cells are ..
smooth muscle, cardiac muscle, glands
2 successive multipolar neurons from CNS to effector
- preganglionic neuron
- postganglionic neuron
Preganglionic neuron
myelinated, cell body in brain stem of the spinal cord
2 subdivisions of autonomic
- sympathetic SNS
- parasympathetic PSNS
3 successive neurons from receptor to cortex
- first order neuron
- second order neuron
- third order neuron
Second order neuron
multipolar interneurons that carry impulses to the thalamus (CNS). located in tracts and decussates in spinal cord or medulla
Third order neuron
multipolar interneurons that carry impulses to the sensory cortex of the CNS .located in tracts. cell body is in thalamus.
Cell body of 2nd order neuron is located in
dorsal horn of spinal cord or medulla.
Spinothalamic tracts of the spinothalamic pathway decussates in .. and picks up..
decussates in spinal cord. picks up pain, temp and sends info to the thalamus
Spinocerebellar Pathway/Tracts consists of
ascending tracts from spinal cord to cerebellum, receptor is located on the 1st order neuron. (proprioceptors that detect changes in balance)
2nd order neuron directly to cerebellum in spinocerebellar pathway has no..
- conscious perception
- 3rd order neuron
Motor pathway send output ..
away from CNS. efferent pathways and multipolar neurons. CNS–> effector cells
2 neuron pathway of the somatic motor pathway
- upper motor neuron
- lower motor neuron
Upper motor neurons
multipolar interneurons, cell bodies in cortex or basal nuclei
Lower motor neurons
cell bodies in CNS and axons in PNS
Axons of upper motor neurons form descending spinal tracts
- corticospinal tracts
- indirect tracts
Cerebellum has folds called..
folia
Nervous tissue are composed of gray and white matter
- gray matter
- white matter
Gray matter
formed from an aggregation of neuonal cell bodies and dendrites
Nuclei are clusters of..
neuronal cell bodies in CNS
Ganglia are cutters of ..
neuronal cell bodies in PNS
White matter
composed of axons that are myelinated
Tracts are bundles of ..
myelinated axons in the CNS
Nerves are bundles of ..
myelinated axons in the PNS
Hydrocephalus
- results from an accumulation of fluid in the ventricles of brain
- occurs because cerebral aqueduct becomes blocked
Midbrain contains nuclei for 2 cranial nerves ..
- lll: oculomotor
- lV: trochlear
Pons consist of motor nuclei for cranial nerves..
- V: trigeminal
- Vl: abducens
- Vll: facial
Spinal cord begins and terminates..
- begins below the foramen magnum
- terminates in the lumbar region of spinal column (termination region is conus medullaris and cone shaped)
Nerves continue down from the conus medullaris existing via the ..
vertebral foramina
Spinal cord contains cervical, thoracic, lumbar and sacral segments that correspond to..
vertebral sections
Cell bodies of motor neurons in mixed nerves are located in..
nuclei of brainstem
Cell bodies of sensory neurons in mixed nerves are located in ..
ganglia outside of the CNS
Spinal plexuses are formed from the ..
ventral rami of the spinal nerves (except T2-T12)
Plexus is a
nerve network
General senses contain 3 different neurons from the receptor to the..
cortex of the brain
Ascending tracts located in the spinal cord
- non specific ascending pathways
- specific ascending pathways
Non specific ascending pathways are when …
you aware of a sensation but unable to detect its origin (pain)
Specific ascending pathways
sensations that you accurately able to detect origin of (touch). ex: dorsal columns in dorsal column pathway
Postganglionic neurons
unmyelinated. cell body is located in ganglia
