Nervous System Flashcards
What are the anatomical divisions of the NS their components (with numbers), and function?
The NS has 2 divisions:
- CNS - central controller
- Brain
- Spinal cord
- PNS: all other nerve tissue not within CNS
- Cranial nerves (12 pairs) - connect with brain
- Spinal nerves (31 pairs) - connect with spinal cord
- ANS - involuntary regulation of our internal environment
- Organs
- Visceral afferents
- Smooth Muscle
- Glands
- Sympathetic NS
- Parasympathetic NS
What are the functions of the nervous system?
- NS allows us to sense our environment and to effect an appropriate response
= Sensory part and a motor (responsive) part and central connections (in the brain or spinal cord) between the two parts
- Protective: helps to “keep us safe”
– External environment (hot/sharp things etc)
– Internal environment (heart, lungs, intestines etc….)
What is the functional unit of the NS?
What are its parts?
A neuron (nerve cell) is the functional unit of the NS - nerve body + axon
Parts:
- Nerve body (soma)
- Dendrite (extension of the cell body - is part of it)
- Axon (nerve fibre)
- coated in myelin sheath
- Axon Terminal + dendrite of next neuron = sypanse with synaptic cleft
What are ganglia?
A ganglia is a collection of multiple cells bodies outside the CNS (in the PNS)
What is a named nerve?
When a lot of axons (nerve fibres) are bundled together, it is called a named nerve
What are the different types of nerve fibres and their function?
What is an important characteristic of nerve fibres?
There are six different types of nerve fibres:
- Somatic motor function: tell a skeletal muscle to contract
- Somatic sensory function: tell the spinal cord/brain about pain somewhere on the body wall
- Special sensory function: tell the brain about a “special” sensation: sight, smell, taste, sound, balance
- Visceral afferent function: tell the spinal cord/brain about pain from an organ
- Sympathetic function: tell cardiac or smooth muscle to contract or a gland to secrete
- Parasympathetic function: tell cardiac or smooth muscle to contract or a gland to secrete
A single nerve fibre (axon) can only conduct action potentials for ONE of the above functions
What is a mixed nerve?
Give some examples
A “mixed nerve” (e.g. intercostal nerve; phrenic nerve; vagus nerve) can carry two or more functional types of nerve fibre to any given region of the body or structure
How do neurons communicate with each other?
By releasing neurotransmitters at the synapse with the dendrite of the next neuron
What is the main part of the brain called? Name its parts and subdivisions
How are they named?
The main part is called the cerebrum or cerebral hemisphere. It has 2 parts:
- Right cerebral hemisphere
- Left cerebral hemisphere
Each hemisphere is divided into 4 lobes - named according to cranial bone they lie deep to:
- Frontal lobe
- Parietal lobe
- Temporal lobe
- Occipital lobe
Label the lobes and name their functions
Label the diagram
Describe the surface features of the brain
List the functions of the smaller part of the brain
A gyrus = undulation that sticks out
A sulcus = undulation that dives in
What is the outermost layer of the brain called?
What is the colour/constituents of the brain in cross section?
How does this relate to the spinal cord?
The outermost layer of the cerebral hemispheres is -cerebral neocortex (cortex)
It is grey in colour: cell bodies
The deep aspect of the brain is white in colour: myelinated axons (myelin gives the white appearance)
– brain neurons reache inwards into brain stem
In the SPINAL CORD the white matter is superficial and the grey matter is deep
– spinal cord neurons reach outwards to spinal nerves
Why are the cranial nerves so named?
How are they numbered?
They are called cranial nerves bc they leave the brain and exit the skull through
- cranial foramina (a hole in the base of the skill) or
- cranial fissures (a slot in the base of the skull)
Generally numbered according to the order from anterior to posterior (or medial to lateral) in which they connect with the brain.
Always use ROMAN NUMERALS (ordinal number is INCORRECT)
How many cranial nerves are there?
Name them
12 pairs of cranial nerves (one on each side)
- Olfactory (nose anterior to eyes!): CN I
- Optic: CN II
- Oculomotor: CN III
- Trochlear: CN IV
- Trigeminal: CN V
- Abducent: CN VI
- Facial: CN VII
- Vestibulocochlear: CN VIII (Auditory: mnemonic)
- Glossopharyngeal: CN IX
- Vagus: CN X
- Spinal accessory: CN XI
- Hypoglossal: CN XII
On Occasion Of Tea Time Attractive Faces Are Generally Viewed Some How
List the functions of each cranial nerve
What kind of nerve fibre does not exist in cranial nerves?
NO sympathetic axons in cranial nerves
- Olfactory (nose anterior to eyes!): CN I
- smell (special sensory)
- Optic: CN II
- vision (special sensory)
- Oculomotor: CN III
- eyeball/eyelid movement (somatic motor)
- pupil shape (parasympathetic)
- Trochlear: CN IV
- eye movement (somatic motor)
- Trigeminal: CN V
- V1 Ophthalmic: facial sensation (somatic sensory)
- V2 Maxillary: facial sensation (somatic sensory)
- V3 Mandibular: facial sensation and chewing (sensory AND motor)
- Abducent: CN VI
- eye movement (somatic motor)
- Facial: CN VII
- sense of taste (special sensory)
- facial expressions (motor)
- facial expression (parasympathetic)
- Vestibulocochlear: CN VIII (Auditory: mnemonic)
- hearing (special sensory)
- equilibrium (special sensory)
- Glossopharyngeal: CN IX
- sense of taste (special sensory)
- oral sensation (somatic sensory)
- swallowing (somatic motor)
- saliva secretion (parasympathetic)
- Vagus: CN X
- throat, cardiovascular, and GI (somatic sensory)
- (somatic motor)
- (parasympathetic)
- Spinal accessory: CN XI
- moving neck and shoulders (somatic motor)
- Hypoglossal: CN XII
- movement of tongue: swallowing, speech (somatic motor)
On Occasion Of Tea Time Attractive Faces Are Generally Viewed Some How
ID each cranial nerve and label the diagram
What is the floor of the cranial cavity called?
Describe its parts
The Base of the Skull (floor of cranial cavity)
Divided into 3 fossa:
- Anterior cranial fossa
- Middle cranial fossa
- Posterior cranial fossa
Characterised by foraminae/fissures/canals for cranial nerves to pass through
Label the cranial fossae
Label the foraminae and mention which cranial nerves pass through them
9 pairs of foraminae
List the cranial foraminae (and the nerves associated with them)
- Cribriform plate: I
- Optic canal: II
- Superior orbital fissure: III, IV, V1, VI
- Foramen rotundum: V2
- Foramen ovale: V3
- Internal acoustic meatus: VII, VIII
- Jugular foramen: IX, X, XI
- Hypoglossal canal: XII
- Foramen magnum
What are the segments of the spinal cord?
What protects it along its length?
Where does it end and name its relevant structures?
Spinal cord has 4 segments:
- Cervical
- Thoracic
- Lumbar
- Sacral/coccygeal
It is protected by the vertebral canal
The spinal cord has 2 enlargements:
- Cervical enlargement
- Lumbosacral enlargement
bc of the increased nerve fibres of the upper/lowe limbs
It ends at L1/L2 intervertebral disc level - tapered lower end called the conus medullaris
Below this the lumbar and sacral spinal nerves descend the vertebral canal to their respective intervertebral foramina via the cauda equina
How many spinal nerves are there?
Give the breakdown
Where are they found in relation to their vertebrae?
There are 31 pairs of spinal nerves
- Cervical spinal nerves: 8 (C1 - C8)
- Thoracic spinal nerves: 12 (T1 - T12)
- Lumbar: 5 (L1 - L5)
- Sacral: 5 (S1 - S5)
- Coccygeal: 1 (Co)
8, 12, 5, 5, 1 (31 total)
vs. 7, 12, 5, 5, 4 for vertebrae (33 total)
C1 vertebra has a spinal nerve above and below it
All other vertebrae have their spinal nerves below them
Label the diagram
Provide any relevant descriptions/details
What kind of nerve fibres do anterior and posterior spinal nerve rootlets/roots have?
Which parts of the body do posterior and anterior rami and spinal nerves in general innervate?
anterior roots (motor)
posterior roots (sensory)
anterior rami supply the anterlolateral body wall (soma)
posterior rami supply the posterior body wall (soma)
spinal nerves: nerve supply of the soma (body wall)
How long is a spinal nerve?
Where is it found?
What kind of nerve fibers do they contain?
A spinal nerve is only about 1 cm long in the intervertebral foramen
It immediately splits into rami – anterior and posterior rami
spinal nerves are mixed structures containing both sensory and motor fibers (combination of anterior and posterior roots)
Name the parts of the body wall (the parts supplied by spinal nerves)
body wall:
- neck wall
- chest wall
- diaphragm
- abdominal wall
- pelvic wall
- all 4 limbs
How is the body wall innervated by spinal nerves?
Name significant landmarks
The body wall is innervated segmentally: dermatomes - area (strip) of skin supplied by both the anterior and posterior rami of a spinal nerve (however no posterior rami in limb dermatomes)
Each dermatome is innervated by a pair of spinal nerves
Significant dermatomes:
T4 dermatome – male nipple
T10 dermatome – umbilicus
What are the functional/physiological divisions of the NS?
Describe the main features
The nervous system is subdivided on the basis of FUNCTION (PHYSIOLOGY)into:
- The SOMATIC NERVOUS SYSTEM: senses and responds to the external environment
- Soma = supplies the body wall.
- has a sensory and motor component
- voluntary EXCEPT reflexes
- The AUTONOMIC NERVOUS SYSTEM: senses and responds to the internal environment
- has a sensory and motor component
- involuntary
- Has 2 divisions
- Sympathetic
- Parasympathetic
–
Where are somatic neurons found?
What do sensory somatic nerve fibres supply?
What do motor somatic nerve fibres supply?
Somatic neurons are found in ALL the spinal nerves and their branches (rami)
Sensory somatic nerve fibres from
- skin
- parietal pleura
- skeletal muscles
- bones & joints
Motor somatic nerve fibres supply
- skeletal muscle (including diaphragm)
What do somatic sensory neurons sense?
- Touch
- Pain
- Temperature
- Joint position
Describe how each of the following organs are affected by the sympathetic/parasympathetic NS:
- Pupils
- Skin
- Arterioles
- Heart
- Lungs
- Gut
- Liver
Sympathetic/Parasympathetic
- Pupils: dilated/constricted
- Skin: hair stands on end, produces sweat/NO PARASYMPATHETIC
- Arterioles: dilates to skeletal muscles, constricts on skin (nonessential: looks cold and pale)/NO PARASYMPATHETIC
- Heart: HR increased/decreased
- Lungs: bronchioles dilated/constricted
- Gut: reduces motility, closes sphincters/increases motility, opens sphincters
- Liver: releases glucose/stores glucose
Describe the flow of sympathetic nervous stimulation
- Originates in the brain
- Flows down spinal cord
- Exits spinal cord at T1-L2 spinal nerves only (thoracolumbar outflow)
- Passes into sympathetic chain (bilateral structure running parallel to the length of the vertebral column)
- Can pass into all 31 spinal nerves and their rami (anterior and posterior) to reach body wall OR
- Can pass into splanchnic nerve to reach organs
Why does sympathetic flow occur only within T1-L2 vertebrae?
Which structure does the sympathetic outflow enter after the spinal cord (and via which rami)?
Because only T1-L2 vertebrae have lateral horns, which house cell bodies of the sympathetic neurons the spinal cord synapses with
After exiting the spinal cord the sympathetic outflow enters the anterior rootlets/roots/rami and then a rami communicans to reach the paravertebral ganglion of the (right or left) sympathetic trunk
Label the diagram
Describe parasympathetic outflow
- Craniosacral Outflow: Leaves CNS via
- CN III, VII, IX, X (oculomotor, facial, glossopharyngeal, vagus)
- Sacral spinal nerves
- Reaches internal organs, not body wall
Vagus nerve supplies organs of the neck, chest and abdomen as far as the mid-gut
Sacral spinal nerves ‘carry’ parasympathetic axons to thehindgut, pelvis and perineum
