Divisions of NS Flashcards
What does the central nervous consist of?
What does the peripheral nervous system consist of?
CNS = Brain and spinal cord
PNS = Somatic NS + Autonomic NS (para and sympathetic)
What controls the ANS?
Is it conscious?
Brain stem
No, unconscious
Parasympathetic vs. Sympathetic
- How targeted?
- Function
- Location in spine
- Ganglia location
- Length of neurones
- PSNS is so specific organs can receive signals, SNS is so one signal can go to multiple organs quickly
Which controls daily relaxed bodily functions and which if the flight or fight response out of sympathetic and parasympathetic?
Parasympathetic = relaxed day to day work
Sympathetic = flight or fight
How does the parasympathetic supply affect the following organs:
Eyes
Salivary glands
Bronchioles
Heart
Blood vessels
GI tract
Bladder
Eyes - constrict pupils, accommodates lens focus for close up
Salivary glands - stimulates secretion
Bronchioles - bronchoconstriction
Heart - decrease HR
Blood vessels - vasodilation in SOME
GI tract - increase activity, stimulate secretion
Bladder - urination
What signals does the PSNS respond to?
Where are the two locations of outflow and what do these nerves supply?
CNS
Exits brain - cranial nerves which supply organs
Exits sacral region - pelvic nerves that supply pelvic organs
Define the following:
neuron
synapse
ganglia
neuron - nerve cell
synapse - junction between two neurons
ganglia - cluster of cell bodies outside CNS that hold synapses
Organise the following pathway that the ANS follows:
Target organ
Synapse
CNS
Post-ganglionic neuron
Synapse
Synapse within ganglia
Pre-ganglionic neurons
CNS
Synapse
Pre-ganglionic neuron
Synapse within ganglia
Post-ganglionic neuron
Synapse
Target organ
How many neurons are required to work for CNS functions?
How many neurons are required to work for sensory/motor functions?
CNS - 2 neurons
Sensory/motor - 1 neuron
What are the main cranial nerves involved with the PSNS?
What are the main pelvic nerves?
Oculomoter (III)
Facial (VII)
Glossopharyngeal (IX)
Vagus (X) [sm. in airways, GI, HR]
Pelvic and splachinic nerves
How does the sympathetic supply affect the following organs:
Eyes
Bronchioles
Heart
Blood vessels
Adrenal glands
GI tract
Bladder
Eyes - pupil dilation
Bronchioles - bronchodilation
Heart - increase HR, increase contraction
Blood vessels - vasoconstriction
Adrenal glands - secretion of adrenaline* + noradrenaline
GI tract - decrease activity
Bladder - urine retention
*same as epinephrine
What signals does the SNS respond to?
Where do there nerves exit/outflow?
Signals from the CNS
Thoraco-lumbar region
In the SNS once exiting the spinal cord, what do the neurons enter?
What ganglia can the nerons then travel to to reach…
the head?
the neck?
the thorax?
the abdomen?
the pelvis?
Sympathetic trunk
Head - cranial cervical ganglion
Neck - cervicothoracic ganglion
Thorax - middle cervical + cervicothoracic ganglia
Abdomen - coeliac, cranial mesenteric, caudal mesenteric ganglia (splanchnic nerve)
Pelvis - caudal mesenteric abdomen ganglion (splanchnic nerve)
What is the origin of the vagus nerve?
Where does it exit from the cranial cavity?
Where do a couple of the vagus nerve fibres also go?
Exits from the medulla oblongata as a series of rootlets
Jugular foramen
In the recurrent laryngeal nerve
What are the vagus nerve fibres?
Mixed 80/20 (sensory/motor)
[motor is PSNS]
Describe the distribution of the vagus nerve in the head and neck:
Gives off the pharyngeal branch going to the pharynx (m+s)
Gives off the cranial laryngeal nerve going to the larynx (m+s)
Then,
Joins sympathetic trunk at cranial cervical ganglion forming the = vagosympathetic trunk
What structures can be found in the vagosympathetic trunk?
Sympathetic fibres running cranially (to head + neck)
Parasympathetic fibres running cranially (from receptors + viscera)
Parasympathetic fibres running caudally (to heart and viscera)
Fibres that for the recurrent laryngeal nerve (to laryngeal muscle)
Describe the distribution of the vagus nerve in the thorax:
VN enters thoracic inlet separating from sympathetic trunk at middle cervical ganglion (doesn’t synapse here)
It gives off:
- recurrent laryngeal nerve
- cardiac branches (cardiac plexus)
- bronchial branches (pulmonary plexus)
Divides into two branches caudal to the heart (dorsal + ventral branch)
Dorsal unite at oesophagus forming single dorsal vagal trunk
Ventral unite forming single ventral vagal trunk
Both pass through oesophageal hiatus of diaphragm
Describe the pathway of the recurrent laryngeal nerve (RLN):
Fibres leave vagal trunk in thorax
Right RLN hooks around right subclavian artery and travels back up
Left RLN hooks around aortic arch and travels back up (longer route than right)
Describe the distribution of the vagus nerve in the abdomen:
Dorsal and Ventral vagal trunks
- supply pre-ganglionic PSNS to abdominal plexus and the gut
- receive post-ganglionic sympathetics
Dorsal vagal trunk
- fibres to coeliac and cranial mesenteric plexuses
Ventral vagal trunk
- fibres to gastric and hepatic plexuses
Describe the distribution of the vagus nerve in the ruminant abdomen:
Dorsal vagal trunk
- rumen
Ventral vagal trunk
- reticulum, omasum, abomasum
- Gastric plexus, branches to duodenum, pancreas, liver, hepatic plexus
Give examples of diseases which involve the nerves within the vagosympathetic trunk:
Idiopathic Laryngeal Hemiplegia – RLN Problem = unilateral laryngeal paralysis (usually left side)
Horners syndrome - damage to sympathetic trunk in the vagosympathetic trunk causing loss of supply to smooth muscle in the eye (usually 1 sided). Clinical signs = enopthalmos (globe tracts) and mitosis (pupil constriction)
Vagal indigestion in cattle and ruminants. Clinical signs = acute bloat, chronic paralysis, poor motility
Fill in the missing blanks:
Using the diagram, identify each of the following stages of the nerve pathway:
1. Pre-ganglionic cell body in grey matter of spinal cord
2. Short pre-ganglionic nerve fibres
3. Point of synapse (with many post-ganglionic fibres)
4. In a number of ganglia (on either side of the spinal cord)
Fill in the blanks for the SNS:
Pre-G fibres are ____ in length
Post-G fibres are ____ in length
Pre-G fibres are Short in length
Post-G fibres are Long in length
Where is the outflow of the SNS from the CNS?
Where are the SNS ganglia located?
Thoraco-lumbar outflow
Bilaterally along the sides of the spinal cord
What are the 3 main divisions of the nervous system?
CNS - brain and spinal cord
PNS - nerves throuoght entire body, including cranial & ANS (plus ganglia and plexi)
ENS - enteric so gut NS
What are the range of functions that the NS undertakes?
Sensory
Motor
Inforation processing
Behaviour
Unconscious (ANS & reflexes)
Conscious (thought, memory & co-ordinated locomotion)
What has an effect on neural function and behaviour?
Hormones
Neural inputs can produce hormonal changes
Neurones are multi-polar, what does this mean?
They undertake lots of processes
Neuron structure
- What are neurons?
- What are axons?
- Where is the nerve impulse generated?
- What are dendrites?
- What connects neurons?
- nerve cell
- nerve cell fibres
- axon hillock
- processes that receive the nerve impulses
- synapses
What are neuroglia cells?
Supporting cells for neurons
Does the CNS have connective tissue?
Is it vascularised?
Does it have a lymphatic supply?
No connective tissues so no obvious boundaries (PNS has connective tissues)
Does have blood vessels supported by neuroglia
Very rare to have lymphatic vessels
Identify the structures in the nervous tissue:
What are macroglia?
Oligodendrocytes (make myelin in CNS)
Schwann cells (make myelin in PNS)
Ependymal cells (line inside of CNS & make CSF and form blood-CSF barrier)
What are microglia?
Specialized mobile macrophages that control inflammation
What are the 3 types of neuronal junctions?
Synapses between neurons
- excitatory or inhibitory
- only in grey matter
Neuromuscular junctions
- neuron to muscle cell
- excitatory in case of skeletal
Neuroglandular junctions
- neuron to glandular cell
- mostly secretory glands
What are efferent neurons?
What are afferent neurons?
What part of the nervous system are they from?
Efferent - send signals from the CNS to the periphery
(E for exiting the CNS)
Afferent - send signals from the periphery towards the CNS
(A for accessing the CNS)
The somatic nervous system
What is the somatic nervous system?
Branch of the peripheral nervous system in association with voluntary control of body movements via the skeletal muscles
(all functions we consciously influence like moving arms and legs)
What neurons are found in the PNS?
- Motor (efferent), multipolar
- Sensory (afferent), pseudounipolar
- Connecting (interneurons) which can be bipolar or multipolar
What neurons are found in the CNS?
Neurones like purkinje fibres
What is white matter?
Nervous tissue covered in myelin which is laid dow around axons and never the cell body. They electrically insulate axons increasing their speed of conductivity.
What is grey matter?
Nervous tissue without myelin so nerve cell bodies and some unmyelinated nerve fibres
Which conducts faster, small or wide axons?
Wide
What is myelin, how does it differ between the PNS and CNS?
PNS - made of Schwann cells
CNS - made of oligodendrocytes
Insulates nerve axons improving their conductivity and therefore the speed at which signals travel across them
In the CNS neuron cell bodies form areas of grey matter..
..in the brain these are called?
..in the spinal cord these are called?
Brain - nuclei or centres
Spinal cord - horns or columns
Label the following cross-section of grey matter in the spinal cord:
What are the 3 main components of the brain?
- Cerebrum
- Cerebellum
- Brainstem
Label the following components pf the brain:
There are 3 kinds of tracts of white matter in the brain, what are these and what are their functions?
Association Fibres
- connect different areas of the same cortex
- short & long
Commissural Fibres
- connect identical areas from the two hemispheres
Projection Fibres
- connects cerebral cortex to subcortical structures (eg. thalamus to spinal cord)
What are the cervical and lumbar intumescences?
Areas where the spinal cord is enlarged and wider because there is an increased number of nerve cell bodies to supply the nerve fibres of the limbs (more muscles in limb = wider area)
The white matter in the spinal cord forms two colours, ventral and dorsal, what is the difference between the two?
Dorsal - sensory ascending tracts
Ventral - motor descending tracts
What does the central canal in the spinal cord contain?
CSF as it is continuous with the ventricles in the brain (however, it cannot be sampled from here)
What do the meninges include?
What makes the subarachnoid space and what does it contain?
What forms the epidural space?
Pia, arachnid matter, dura mater
The arachnoid & pia which form a closed bag which contains CSF
The periosteum & dura mater
What is the purpose of a spinal tap?
To sample CFS from the subarachnoid space
What is CFS Myelography?
Inject radiopaque material into spinal subarachnoid space
to detects space altering lesions of vertebral canal
In the PNS,
what are peripheral nerves in the head called?
what are peripheral nerves in the body called?
Head - cranial nerves (I - XII, arise from brainstem)
Body - spinal nerves (8 cervical, 13 thoracic, 2 sacral, 5 caudal)
What are InterVertebral Foraminae (IVF)?
What are vertebral foramen?
IVF = points of entry/exit for spinal nerves and vasculature
VF = opening for the vertebral canal
