Nervous System Flashcards
What is a system?
collection of different organs and tissues that has a specific function
What is the nervous system made up of?
a network of nerve cells (neurons and fibres)and their supporting cells
What does the nervous system basically do?
transmit nerve impulses between different parts of the body
What is the basic function of the nervous system?
allows sentient organisms to live effectively in their environment
What are ganglia?
collections of cell bodies
What are the 4 key functions of the nervous system?
sense and monitor environment
respond, react and move around environment
integrate, process and store information
maintain internal stasis of the body
What tissues and cells does sensing and monitoring the environment involve?
sensory tissues and organs, sensory nerves
What cells and tissues are involved in responding to and moving around the environment?
motor nerves and muscles
What cells and tissues are involved in maintaining internal stasis of the body?
motor nerves, smooth/cardiac muscle and glands
What are the two locations of the nervous system?
central nervous system and peripheral nervous system
What is the CNS comprised of?
brain and spinal chord
What is the PNS comprised of?
all nerves that are not found in the brain/spinal chord
What can the sensory nervous system also be known as?
afferent
What can the motor nervous system also be known as?
efferent
What is the difference between somatic and autonomic nervous systems?
somatic is voluntary and autonomic is involuntary
What are glia?
supporting cells of CNS and PNS
How does regeneration of nerves differ between CNS and PNS?
CNS- nerves do not regenerate after injury, there is no secretion of growth factors and inhibitory factors are actually released
PNS- nerves regenerate well after injury
What are the 2 branches of the autonomic nervous system?
sympathetic and parasympathetic
What does the sympathetic nervous system do?
fight of flight mechanism, speeds things up and diverts blood where it is needed (e.g. away from digestive system towards muscles)
What does the parasympathetic nervous system do?
rest and digest mechanism, slows everything down, diverts blood back to slower areas (e.g. towards digestive system)
What main divisions of the nervous system are the sympathetic and parasympathetic systems associated with?
CNS and PNS
What is a neuron?
the functional unit of the nervous system
What 3 types of neuron are there?
sensory, motor and interneurons
What are neurons specialised to do?
detect and react to stimuli
What do neurons generate, conduct and transmit?
nerve impulses
What are the 3 main areas on a neuron?
axon, dendrites and terminal synapses
How does the signal flow through a neuron?
dendrites-axon-terminal synapse
what do neuroglia do?
surround neurons
What do neurons use synapses for?
to communicate with other neurons or effector target cells
Where are the 3 main locations of synapses?
axon to dendrite, axon to cell body, axon to axon
Basically describe how a synapse works?
nerve impulse reaches terminal, stimulates the release of synaptic vesicles containing neurotransmitter. These leave the cell by exocytosis, cross the synaptic cleft to receptors on next cell surface
What is mylination?
surrounding of axon by glial cells to improve rate of conduction
What is the node of ranvier?
unmylinated area of nerve cells
Which cells are involved in mylination in the CNS?
oligodendrites
Whic cells are involved in mylination in the PNS?
schwann cells
How are axons mylinated differently in CNS and PNS?
CNS- each cell wraps around a different part of the axon
PNS- axon is mylinated by single cell that is wrapped/spiralled around
What is the CNS housed within?
bone
What bones are the brain and spinal cord housed in?
cranium and vertebrae
What is the name for the 3 layers of tissue which surround the CNS?
meninges
What are the 3 layers of meninges?
dura mater, arachnoid mater, pia mater
What is the dura mater like?
tough, outer layer of meninges
What is the arachnoid mater like?
web like appearance, middle layer of meninges
What is the pia mater like?
pink in colour, sits directly on top of spinal cord and bran, thinnest layer
What do the meninges do?
support and protect CNS and produce cerebral spinal fluid
What do spaces between meningeal layers house?
CSF and blood vessels
Where is the grey and white matter located in the spinal cord and what do they contain?
grey: houses cell bodies, located inside white matter which contains axons
Where is the grey and white matter located in the brain and what do they contain
grey: houses cell bodies and is located outside of the white matter which contains axons
Why is white matter white?
mylination of axons
Where does the spinal cord exit the brain?
at the foramen magnum
What is the foramen magnum?
hole at the bottom of the skull through which the spinal cord exits
Where does the spinal cord begin?
at the exit of the brain
What are the 5 sections of the spine?
cervical, thoracic, lumbar, sacral, coxygeal
What do nerves from the cervical spine lead to?
upper limbs/forelimbs
What do nerves from the thoracic spine lead to?
body wall and skin
What do nerves from the lumbar spine lead to ?
lower/hind limbs
What do nerves from the sacral spine lead to?
lower/hind limbs
Why is the cord not uniform in thickness?
increases in thickness in areas which correspond with limbs, increased neurons to the area
Where is the spinal cord thicker?
lumbar/sacral and cervical regions
What shape is the end of the spinal cord?
cone shaped
What is the name for the end of the spinal cord?
conus medullaris
At the end of the spinal cord what is the name of the nerves which continue in the vertebrae?
cauda equina
What is the filum terminale?
attachment of pia mater thread to the coccyx to anchor the spinal cord and cauda equina
what is the number of nerve pairs in each region often the same as?
the number of vertebrae in that region
How many pairs of spinal nerves are there in humans?
31
How many pairs of cervical nerves do all mammals have?
8
What happens to nerves in the thoracic region when they leave the spinal cord?
come out horizontally and don’t touch any other nerves
What are plexi?
groups of nerves that join together outside the spinal cord to form bigger nerves
What are 3 plexi in the mammalian body?
brachial plexus, lumbar plexus, sacral plexus
What do cranial nerves form part of?
PNS
How many pairs of cranial nerves are there?
12
Where do most cranial nerves originate from?
midbrain
What arteries make up the circle of willis?
clockwise from rostral end: anterior communicating artery, anterior cerebral artery, posterior communicating artery, posterior cerebral artery
Why is the circle of willis so important?
collateral blood flow, if one artery becomes blocked the blood can still flow to the brain
What are venous sinuses?
channels of venous blood that run between layers of dura
What two layers of dura are venous sinuses found between?
periostial and meningial
Where is the superior saggital sinus located?
over the top of the brain, on the midline
What does the sigmoid sinus do?
drains all blood from transverse sinus into internal jugular vein
What are the ventricles of the brain?
chambers within the brain
What do ventricles in the brain produce?
CSF
What are the 4 ventricles of the brain?
2 lateral ventricles that drain in to the 3rd ventricle in the midline, 4th ventricle is in the hindbrain
Where does cerebral spinal fluid enter the spinal cord and sub arachnoid space?
lateral and median apatures
What is CSF produced by that is found within all the ventricles of the brain?
choroid plexus
Where is CSF absorbed back into the blood stream?
venous sinuses at arachnoid villi
What does the ectoderm in an embryo go on to create?
skin and nervous system
What does ectoderm differentiate into?
ectoderm (skin) and neuroectoderm (neural tube)
What are neural crests the margins of?
neuroectoderm
What happens when neural crests meet in the mid line?
form a tube (neural tube)
What happens to neural crest cells once they separate from neuroectoderm?
migrate across embryo to differentiate into multiple different neural cells
What 7 structures do neural crest cells differentiate into?
sympathetic ganglia dorsal root ganglion (neural tube) adrenal medulla intrinsic nerve plexuses ondontoblasts melanocytes tissues of iris
What are the edges of the neural plate called?
neural folds
What do neural folds meet in the midline to form?
neural tube
what are the holes at each end of the neural tube known as?
cranial or caudal neuropores
Once the neuropores are closed what structures can begin to form?
brain and spinal cord
What does the closed neural tube then undergo to form the 3 cranial vesicles?
massive growth, swelling and folding
How many cranial vesicles are there initially?
3
What are the names of the 3 vesicles?
forebrain, midbrain and hindbrain
What does the lumen of the neural tube form?
ventricles of brain
At what week are 5 cranial vesicles formed?
week 5
What is the correct term for the forebrain?
prosencephalon
what is the correct term for the midbrain?
mesencephalon
what is the correct term for the hindbrain?
rhombencephalon
What are the names of the vesicles that the prosencephalon splits into?
telencephalon and diencephalon
What is formed in the telencephalon?
cerebral hemispheres and lateral ventricles
what is formed in the diencephalon?
thalamus, hypothalamus, pituitary gland and the 3rd ventricle
what two ventricles form in the rhombencephalon?
metencephalon and myelencephalon
what is formed in the metencephalon?
pons and cerebellum
what is formed in the myelencephalon?
medulla oblongata
from which vesicle does the optic vesicle originate?
diencephalon
What happens to the lumen of the mesencephalon?
narrows to form cerebral aqueduct
How many different fibre types are there in the brain?
3
How are the fibre types in the brain named?
According to their origin and destination
Are brain fibres myelinated or non myelinated?
Myelinated
What’s re the 3 types of brain fibre?
Association, projection. Commisural
What do association fibres do?
Span cortical regions within the same hemisphere
Give 2 examples of where association fibres may be found
Cinglugate gyrus
What do projection fibres link?
Cortex to other regions outside the cortex, sun cortical structures
Give an examples of where projection fibres are found
Internal capsule and corona radiata
What are commisural fibres?
Communicate between two hemispheres
Give 2 examples of where commisural fibres are located
Corpus callosum and anterior commisure
What is a plexus?
Region of the peripheral nervous system where several nerves arising from the spinal cord join
What do nerves in a plexus subsequently divide into?
Individual nerves
What are individual nerves that split from plexi named for?
Destination and function
What does a plexus allow?
Nerve fibres that originated in one nerve can be distributed into another
What are the types of plexus?
Spinal plexuses and autonomic plexuses
What is a spinal plexus?
Where spinal nerves containing mixed motor and sensory fibres join
What is an example of a spinal plexus?
Brachial plexus
What is an autonomic plexus?
Where splanchich nerves containing autonomic fibres join
Give an example of an autonomic plexus
Myenteric plexus
What other structure can a plexus recur to?
A group of blood vessels
What is controlled by spinal plexuses?
Skeletal muscles and skin
What is controlled by autonomic plexuses?
Smooth muscle
What nerve roots is the brachial plexus formed from?
Nerve roots of spinal nerves from C5, C6, C7, C8, T1
Which nerve roots join to form nerve trunks?
C5, C6 and C8, T1
What happens to the nerve trunks in a brachial plexus?
Divides into 2 and then reforms/ joins forming cords
What do nerve cords which originate from trunks in nerve plexi become?
Individual nerve branches (e.g. radial or ulnar nerves)
What is a spinal reflex?
A relay of sensation or stimulus which brings about an appropriate, fixed reaction or motor response
Where do afferent nerves enter the spinal cord?
The dorsal root
Where do efferent nerves exit the spinal cord?
Ventral root
Give a brief explanation of a reflex arc
Stimulus sensed, sensory nerve, synapse, motor neuron, effector
What happens during reciprocal innervation?
Stimulus, sensory nerve, inhibitory interneuron. This leads to no opposition of movement required by reflex
What does reciprocal innervation basically do?
Stops the antagonist of the reflex movement from being activated so that the reflex works
What is the spinal cord important in?
conveying sensory information from the body to the brain so that it can be experienced as sensation
also conveys information regarding appropriate motor responses coordinated by the brain
where are spinal tracts found?
white matter of the spinal cord
are spinal tracts myelinated or non-mylinated?
myelinated as located in white matter
what are the 2 types of spinal tracts?
ascending and descending
What do ascending spinal tracts do?
transfer sensory information towards the brain
What region of the spinal chord are ascending spinal tracts found in?
dorsal
what do descending spinal tracts do?
transfer motor information back towards the peripheral nervous system
what region of the spinal chord are descending spinal tracts found in?
tend to be found in the ventral regions of the cord
Why does each tract contain different nerve fibre types?
because they carry different information types
what is a single spinal tract called?
fasciculus
What is a funinculus?
Column of white matter tissue
What are the 3 main groups of funinculus?
Dorsal or posterior, lateral, ventral or anterior
what areas do motor somatic nerves go to?
skeletal muscle
What does the corticospinal pathway do?
Motor information from the motor cortex to the spinal cord, out into periphery to relevant skeletal muscles
What does ipsilateral mean?
Same side of the nervous system
What does converlateral mean?
Refers to the opposite side of the nervous system
what are the 2 branches of the sensory afferent nerves?
general and specialised
What sides is the nervous system divided into?
Left and right
What a nociceptors?
Receptors that detect noxious stimuli
What do autonomic afferents and efferents arise from and go to?
the viscera
Give 2 examples of areas sensory somatic nerves arise from
skin/eyes/ear
what areas do motor somatic nerves go to?
skeletal muscle
What is the somatic nervous system sometimes known as?
voluntary
What are the 2 components of spinal nerves?
motor and sensory
what are the 3 nerve types found in the somatic nervous system?
afferent sensory, efferent motor and interneurons
what are the 2 branches of the sensory afferent nerves?
general and specialised
What do general sensory afferent nerves detect?
touch, vibration etc
what do specialised sensory afferent nerves detect?
special senses (e.g. sight, hearing)
What do autonomic afferents and efferents arise from and go to?
the viscera
Which of the special senses are autonomic?
taste and smell
what are the functions of the somatic nervous system?
involved in the detection of stimuli from the external environment and control of skeletal muscles
What are spinal nerves named according to?
the region from which they emerge
what does the ventral rami do?
supplies muscles and skin associated with limbs and trunk
What can be formed from ventral rami?
plexuses
How many spinal nerve pairs do humans have in total?
31
How many cervical nerve pairs do all mammals have?
8
How many spinal nerve pairs do cats and dogs have in total?
36
how many spinal nerve pairs do horses have in total?
42
what are dermatomes?
area of skin supplied by the afferent fibres of one single spinal nerve
what are myotomes?
group of skeletal muscles supplied by efferent fibres of one single spinal nerve
What does the T10 dermatome cover?
the umbilicus, often where pain originates during appendicitis
What does the L3 and L4 myotome supply?
quadriceps
What are myomeres?
adjacent blocks of skeletal muscle tissues separated by connective tissue
In what species are myomeres often seem?
fish (e.g. salmon)
What does the visceral nervous system monitor and control?
cardiac muscle, smooth muscle and glands
What is the motor division of the viscera known as?
autonomic nervous system
what are the 2 branches of the autonomic nervous system?
sympathetic and parasympathetic
What does the sympathetic nervous system control?
fight/flight
What does the parasympathetic nervous system control?
rest and digest
Is the sympathetic or parasympathetic system more widespread in the body?
sympathetic
What are the 2 types of visceral neurons?
general visceral afferent and general visceral efferent
where does the visceral nervous system synapse?
in the ganglia
Where is the cell body of presynaptic neurons of the visceral nervous system located?
cell body is in the grey matter of spinal cord
where are the postsynaptic neurons of the visceral nervous system located?
cell body in ganglion and axon outwards of this
Do ganglia vary between sympathetic and parasympathetic systems?
yes
Where are ganglia located in the sympathetic nervous system?
close to the spinal column
Where are ganglia located in the parasympathetic nervous system?
proximal to target organ
where are pre-vertebral ganglion located?
in front of the spinal cord
where are para vertebral ganglion located?
next to the spinal cord
What part of the sympathetic nervous system do the paravertebral ganglia from?
sympathetic chain
are there any synapses in the sympathetic chain?
no
What 2 locations do sympathetic neurons originate in?
thoracic and lumbar regions
What are splanchnic nerves?
nerves heading towards sympathetic /visceral structures, usually sympathetic nerves
Do parasympathetic nerves have a chain like the sympathetic chain?
no
where do the parasympathetic nerves originate from?
cranial and sacral regions
What 4 cranial nerves are parasympathetic?
3, 7, 9 and 10
What number cranial nerve is the vagus nerve?
10
Where are ganglia located in the parasympathetic nervous system?
close to/within the target organ
Do parasympathetic nerves join with spinal nerves?
no
In non-human mammals where is the vagus trunk formed of and what 2 nerves is is formed of?
in the neck adjacent to oesophagus
sympathetic nerve and vagus nerve
What is ischemia?
lack of blood supply
what is an ischemic stroke?
occlusion of a blood vessel in the brain by a clot
How can symptoms of nervous damage differ?
depends on site of injury and therefore the type of nerve fibre that has been damaged
What are common symptoms of sensory nerve damage?
partial/complete loss of sensation
parasthesia (pins and needles)
what is parasthesia?
pins and needles
What are common symptoms of motor nerve damage?
weakness/paralysis of muscles
change in muscle tone (rigidity and power)
fascultations (twitching)
What is tetraplegia?
complete or partial paralysis of all 4 limbs
what is paraplegia?
paralysis below bracial plexus so arms/forelimbs function but legs/hindlimbs do not
What is hemiplegia?
Damage to one of the cerebral hemispheres that leads to paralysis of the side of the body it controls (opposite)
what can the formation of a dermoid sinus lead to?
infection within the spinal cord
What are 2 examples of neural tube defects?
spina bifida and anencephaly
What is the function of the temporal lobe?
hearing
What is the function of the oxypital lobe?
vision
what is the function of the frontal lobe?
higher mental functions/memory formation
What do the nerve endings of sensory nerves relate to ?
their functions
What are the 2 divisions of sensory neurone?
free and encapsulated
How does the terminus of sensory process appear in a free sensory neuron?
lacks any special ending/association
How do free sensory neurons increase the area monitored?
branch extensively
Where are free sensory neurons most often found?
in epidermis and dermal skin layers
How does the terminus of sensory process appear in an encapsulated sensory neuron?
enclosed in a specialised structure
What are 2 examples of encapsulated sensory neurons?
messiner corpuscle: light touch, in the dermis
corpuscle of Ruffini: dual mechanoreceptor and thermoreceptor
Where are proprioceptors found?
within muscle/tendon
What is the function of proprioceptors?
show degree of strength/stretch and enables CNS to have an idea of location of limb in space
What is hyperalgesia?
amplification of stimulus to sensory nerves as a result of tissue damage
What is alodenia?
reduction of pain threshold as a result of nervous tissue damage. Non-painful stimuli may be interpreted as such
What are the majority of muscle fibres made up of?
extra fusal muscle fibre
What does extra fusal muscle fibre contain?
actin, myosin and sarcomeres
What do muscle fibres basically do?
lengthen and shorten muscle
what sort of nerves are muscle fibres innervated by?
somatic efferent neurones
Why does the CNS need to be receptive to the tone and stretch in muscles?
to ensure there is no damage
Do muscles contain a slight amount of tension even when relaxed?
yes
What is the name of the sensory fibres of the PNS that extend into the muscle which measure tension and stretch?
muscle spindle
What makes up a muscle spindle?
composed of intrafusal muscle fibre which has a sensory nerve fibre wrapped around it
What part of the brain is information from muscle spindles relayed to?
cerabellum
What happens to the frequency of action potential in muscle spindles when they stretch?
increases
What happens to the frequency of action potential in muscle spindles when they contract?
decreases
What are golgi tendon organs?
sensory fibres in tendons that attach to bone
What do golgi tendon organs measure?
tension recorded by tension created in muscles
Where are hair cells found?
in inner ear, cochlea and vestibular organs
What transduces signals into electrical impulses in hair cells?
deformation of hair cells by sound waves or fluid
What are lateral line systems?
pores on the sides of fish which are sensitive to movement in water and pressure changes
What parts of fish behavior do lateral line systems help with?
school behavior
What is echolocation?
animal emits and detects soundwaves to determine the rages between objects
Ho do dolphins produce and receive soundwaves during echolocation?
air enters blowhole and fills nasal sacs where it vibrates. this produces sound waves which are concentratedin the melon and emmitted as a beam into surrounding water. Vibrations received are felt in the jaw and transfurred to the middle ear where hair cells in the vestibular system are deformed
What do radiation receptors pick up?
light spectrum
What is infra red light linked to?
thermoreceptors
what is UV light filtered by?
human eye, retinal pigments
In what species are electrorecptors seen?
bony fish and monotrines
What is a monotrine?
mammal that lays eggs
what do electroreceptors produce and detect?
electric and magnetic fields
What would a gustatory stimulus be triggerd by?
taste
What sensations other than those produced by chemoreceptors lead to our experience of taste?
mechanical texture of food
olfaction
What are pheremones produced by?
exocrine glands
What is the main taste organ?
the tongue
Which cranial nerves are involved in taste?
7 and 9
Which part of the tongue supplies cranial nerve 7?
anterior 2 thirds
which part of the tongue supplies cranial nerve 9?
posterior third
Where are tastebuds located?
crits on papilliae
What are tastebuds also known as?
gustatory cells
What parts of the tongue contain tastebuds?
valliate
foliate
fungiform
Which part of the tongue is involved in general sensation?
fileform
Where is the gustatory cortex located in the brain?
insular region between temporal and poriatal lobes deep into the lateral fissure
How are the olfactory nerves stimulated?
air is inhaled into nasal passages and picked up by nasal hair and mucous that line the nasal mucosa. Odorants dissolve in mucous and stimulate olfactory nerves
Where is the olfactory centre of the brain located?
olfactory bulb near the hippocampus
What is the main organ involved in pheromone detection?
jacobsen’s organ/vomeronasal organ
Where is the vomeronasal organ located?
nasal septum
In what species is a vomeronasal organ found?
cats, dogs, reptiles, equines, cows
What varies in the usage of the vomeronasal organ between species?
how they deliver the pheromone to the organ (e.g. cats and horses inhale to a duct behind their teeth. Snakes use their tongue to gather scent and then touch the organ)
