WEEK 4 LECTURE FINISHED Flashcards
What does the CNS consist of?
Brain
Spinal cord
What does the Peripheral nervous system consist of?
CN’s - 12 pairs
Spinal Nerves - 31 pairs
What are the 2 components of the functional nervous system?
Autonomic nervous system
Somatic nervous system
What does the autonomic nervous system control?
Smooth muscle
Glands
Organs/viscera
What is the function of the nervous system?
Enables the body to react to continuous changes in the internal and external environment
Controls and integrates the various activities of the body e.g. circulation and respiration
What are the main cells of nervous tissue?
2 main cells
- Neurons/nerve cells
- Neuroglia (glia cells), support cells
Nerve cells to neuroglia cells ratio
1:5
What is the structural and functional unit of the nervous system?
The neuron
What are the 3 functional classes of neurons?
Efferent (motor)
Afferent (sensory)
Interneurons
What are the parts of a neuron?
Cell body
Dendrites (carry impulses to the cell)
Axon (Carry nerve impulses away from the cell body)
What are afferent neurons? Describe a typical afferent neuron. Where is the cell body located?
A sensory receptor which generates AP’s in response to a type of stimulus
Cell body has no dendrites, located adjacent to spinal cord.
Long peripheral axon extending between receptor and cell body
Short central axon from cell body to spinal cord, synapses with neurons in spinal cord
What are efferent neurons? What do they do? Where is the cell body located?
• Carry information from the CNS
- ‘e’ = from
- ‘ferent’ = carry
- Transmits instructions from the CNS to effector organs (mm, glands)
- Cell body originates w/n the spinal cord
What are Interneurons? Where are they situated? How many of them do we have approx?
- 99% of all neurons
- Lie entirely w/n the CNS
- 100 billion interneurons
- Inter = between
- Lie between afferent and efferent neurons
What does glial mean?
Glue
What are the 4 main types of neuroglial cells within the CNS? Describe them
- Astrocytes (physically support, neural scar tissue, help transmit nutrients, degrade neurotransmitters)
- Oligodendrocytes (myelin in CNS)
- Microglia (phagocytic, defence)
- Ependymal (line cavities, contribute to CSF, neural stem cells - neurone and glial)
Where are schwann cells found and what do they do?
Peripheral nervous system. They make myelin.
What is myelin? What does it do? What is it made by? What is an interruption between 2 segments of myelin called?
Myelin is a protein and lipid substance which helps by greatly increasing the velocity of impulse conduction.
It gives a fibre a white creamy colour.
Made by oligodendrocytes in the CNS
Made by schwann cells in the peripheral nervous system
Interruption = node of ranvier
MS: What is it?
MS is a progressive disease where there is demyelination of nerve fibres in the brain and spinal cord
Synapses: what do they do? And how do they communicate between with each other?
Neurons communicate with each other at synapses, points of contact between neurons.
Neurons communicate via the release of chemical substances called neurotransmitters which may excite or inhibit the other neuron.
What is a collection of nerve cell bodies in the CNS known as?
Nucleus
What is a collection of axons in the CNS known as?
A tract
What is grey matter?
Nerve cell bodies
What is white matter?
Interconnecting fibre tract systems
How many horns are there in the spinal cord?
4
- Right anterior / ventral horn
- Left anterior/ ventral horn
- Right posterior / dorsal horn
- Left posterior / dorsal horn
What are the meninges? How many types are there?
3 types:
Pia mater (inner most) “tender”
Arachnoid mater “Spider form”
Dura mater “Hard”
What does CSF do? Where is it found?
Surrounds the brain and spinal cord and protects/cushions it.
Found between the pia mater and the arachnoid mater in the subarachnoid space
What are the principle roles of the CNS?
Integrate and coordinates incoming and outgoing neural signals
Carry out higher mental functions (eg thinking and learning)
What does the peripheral nervous system consist of?
Nerve fibres and cells bodies outside of the CNS
Cranial Nerves
Peripheral nerves
How many pairs of cranial nerves are there?
12
How many pairs of spinal nerves are there? Break down into the different areas of the spine e.g. cervical etc
31
8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal
Where do spinal nerves exit in relation to the vertebra?
Through the intervertebral foramina
Usually exit beneath the corresponding vertebra except in the neck, where the cervical ones pass out above the corresponding vertebra, which is why there is a C8 spinal nerve but no C8 vertebra.
What are the 2 types of peripheral nerves?
Sensory - impulses towards CNS
Motor - impulses away from CNS
What is the connective tissue around peripheral nerves?
» Endoneurium (surrounds the neurolemma cells and axons)
» Perineurium (encloses a bundle of peripheral nerve fibres, provides protection against foreign substances)
» Epineurium thick sheath of loose connective tissue, surrounds nerve bundles (outermost covering, includes fatty tissue, blood vessels and lymphatics)
Spinal nerves:
Typically arise from?
What are the horns?
What do they do/what types of nerves are they?
What happens to the nerve fibres after they have left the spinal cord as nerve roots?
Typically arise from the spinal cord via rootlets to form 2 nerve roots. These roots are named for the part of the spinal cord they exit, and this also determines what kind of signal they will carry.
- Nerve root from the Anterior / ventral horn – motor fibres, nerve cell bodies are in the ventral horn of the spinal cord
- Nerve roots from the Posterior / dorsal horn – sensory fibres, nerve cell bodies are in the dorsal root ganglion
Fibres from the ventral and coral roots will unite to form a mixed spinal nerve.
Mixed spinal nerves divide into 2 rami: what are their names? name them and explain where each of these rami usually innervate.
Dorsal rami: The smaller of the two rami - Supply: The synovial joints of the vertebral column Deep muscles of the back Overlying skin
Visceral Rami: The larger of the two rami
- Supply:
the anterior and lateral trunk
Upper and lower limbs
Components of spinal nerves: what are the 4 types and what do they do?
Somatic sensory (general somatic afferent) - Transmits sensations from the body to the spinal cord (eg pain, temperature, touch and pressure from skin) (pain and proprioception from muscles, tendons, joints)
Somatic motor (general somatic efferent) - Impulsestoskeletal(voluntary)muscle
Visceral sensory (general visceral afferents)
- Reflex or pain sensations from mucous
membranes, glands, blood vessels
Visceral motor (general visceral efferent)
- Transmits impulses to smooth (involuntary) muscle and glandular tissue
- Includes presynaptic and postsynaptic neurons
Sensory Nerves: Where are their cell bodies?
Both types of sensory nerves (general somatic and visceral) have their cells bodies in:
- spinal ganglia
OR
- the sensory ganglia of the cranial nerve.
What is the somatic nervous system comprised of?
What does the somatic motor system do?
Comprised of somatic pars of both CNS and peripheral nervous system. It relates to external activities and the bodes structure.
Transmits sensations of touch, pain, temperature and position from the sensory receptors
The somatic motor system permits voluntary and reflexive movement by causing contraction of skeletal muscle
ANS is?
AKA?
Autonomic nervous system
Visceral system
What is the ANS related to?
The internal activities of the body
What do the ANS nerve fibres innervate?
Is it voluntary or involuntary?
Organs, glands, smooth muscle, cardiac muscle
Involuntary
Where does the central control for the ANS come from?
Hypothalamus
What does the visceral afferent system usually conveys what kind of sensory impulse and where is this sensation from?
Conducts visceral pain impulses
What are the 2 components of the autonomic nervous system? Can these be further broken down?
Afferent and efferent components
Efferent can be broken down into:
Sympathetic and Parasympathetic
What do visceral afferents do? What do they run with?
Detect pressure, distension and chemical substances
Have a direct influence on sympathetic & parasympathetic function. They run with the PNS and SNS nerves
What are the 2 divisions of the ANS efferent systems? Where do they get their innervation from?
Parasympathetic -
Cranio-sacral division
CN’s, pelvic splachnics (S2-S4)
Only 4 CN’s have parasympathetic fibres (3,7,9,10)
Sympathetic -
Thoracolumnar division
How many neurons are there in the output pathways of the ANS?
2 neurons in the output pathways:
1st cell presynaptic or preganglionic neuron
2nd cell, post synaptic or postganglionic neuron
Where is the presynaptic or preganglionic sympathetic neuron located?
The cell body is located in the grey matter of the CNS
- this cell only synapses on the cell body of the postsynaptic or postganglionic neuron
Where is the postsynaptic or post ganglionic sympathetic neuron located?
Where do its fibres terminate?
The cell body is located in autonomic ganglion outside the CNS
- its fibres terminate on the effector organ (ie smooth mm, cardiac mm, gland)
What are the differences between the 2 divisions of the ANS?
- Action (sympathetic vs parasympathetic)
- The location of the presynaptic cell bodies
- Secrete different neurotransmitters e.g.
sympathetic (norepinephrine)
parasympathetic (acetylcholine)
In general each visceral organ receives innervation form both divisions of the ANS
The SNS:
Where are the cell bodies found? Are they singular or pair in the spinal cord? Between which spinal segments do the cell bodies lie in the spinal cord?
Cells bodies of the presynaptic neurons are found in the CNS (in the lateral horn) in a part called the IMLs
(IML = intermediolateral cell columns of the spinal cord)
They are paired columns (left and right)
Part of the grey matter extending between T1 and L2/3 segments of the spinal cord
- little lateral horns in the H-shaped grey matter
What is the paraverterbral sympathetic ganglia?
A possible site of synapse of the pre and post ganglionic neurons of the SNS
The post synaptic neuron cell bodies of the SNS can be found where?
Paravertebral ganglia
OR
Prevertebral ganglia
What are the paraverterbal ganglia?
The site of post synaptic ganglia to which the SNS presynaptic fibres can synapse.
These link and form the left and right sympathetic trunks on each side of the vertebral column
Extend essentially along the whole length of the vertebral column
How many ganglia are in the cervical region?
3 cervical ganglion:
- superior (C1/2)
- middle (C6)
- inferior (C7))
How many ganglia are in the:
Thoracic region?
Lumbar region?
Sacral region?
11 thoracic
4 lumbar
3/4 sacral
What happens to the 2 pelvic sympathetic trunks distally?
The two pelvic sympathetic trunks converge, and end on the front of the coccyx in a small ganglion, the ganglion impar (or ganglion of Walther).
What does the grey communicating branch do?
Transmits the impulse from the postsynaptic neuron back to the spinal nerve and distributed around the body.
What does the white communicating branch do?
Transmits the presynaptic neuron information to the paravertebral ganglia for synapse. This information can then be sent back to the spinal cord (via grey communicating branch) for transmission to the target organ or can be sent up or down the sympathetic chain to a level above or below, there it then goes through the grey communicating branch, to the spinal nerve and then to the target organ
What are the 3 options for synapse of the SNS?
1) Enter and synapse immediately with postganglionic fibre at the same level
2) Ascend or descend in the sympathetic trunk and synapse with a post ganglionic neuron at a higher or lower level
3) Pass through the sympathetic trunk without synapsing and continue through to the prevertebral ganglion (via an abdominopelvic splanchnic nerve)
Parasympathetic Nervous system fibres: where do the presynaptic parasympathetic neuron cell bodies originate in the CNS?
In 2 locations:
They can be found in the grey matter of the CNS
- Cranial Nerves: 3,7,9,10 (Cranial parasympathetic outflow)
OR
The grey matter of the sacral segment of the spinal cord.
- S2-S4
These fibres exit the CNS through the ventral roots of the spinal cord. The pelvic splanchnic nerves arise from the ventral rami of spinal nerves S2-S4
What does the parasympathetic system innervate?
The viscera only
Where are the presynaptic PSNS neuron cells bodies located?
Grey matter within brain stem
OR
Grey matter of the sacral segment of the spinal cord
What is the crania parasympathetic outflow supply to the GIT and abdomen?
What does the pelvic splanchnic supply in the GIT?
Cranial outflow:
All the way down to the left colic flexure, everything between the descending colon.
Testes and ovaries
Pelvic splanchnic:
Descending colon, sigmond colon and rectum (everything after left colic flexure)
How many discrete pairs of parasympathetic ganglia are there in the head?
4
Cillary
Pterygopalatine
Otic
Submandibular
Ciliary Ganglia location
Found between optic nerve and the lateral rectus muscle
Pterygopalatine ganglion location
Found just inferior to the apex of the orbit, small pyramidal space
Otic ganglion location
Lies just inferior to foramen oval of the sphenoid
Submandibular ganglion location
Lies on the surface of the hyoglossus muscle inferior to the submandibular duct.
If not with the parasympathetic ganglia in the head, where do the presynaptic parasympathetic fibres synapse with the post synaptic neurons?
Usually in or on the wall of the organ.
What are gliomas?
Glial cells can multiply, brain tumours - gliomas
What is a bundle of nerve cell bodies in the peripheral nervous system called?
Ganglion
What is a bundle of nerve fibres (axons) in the peripheral nervous system called>
A peripheral nerve
What does lemmal mean?
Sheath/ husk
Where do sympathetic fibres pass after they have synapsed with the post synaptic neuron?
They travel back to the spinal nerves via the grey communicating branch.
These fibres are then distributed to both the dorsal and ventral rami to supply the neck, body walls, limbs. Eg stimulate arrector pili muscle in hard follicles, sweating, contraction of blood vessels.
Where do the SNS fibres that perform functions in the head usually have their post synaptic neuron?
Usually in the superior cervical ganglion
Where do the SNS fibres that perform functions in the thorax usually have their post synaptic neuron?
Innervated by neurons in:
The 3 cervical ganglia
AND
The first 6 thoracic paravertebral ganglia
Where do SNS fibres that perform functions in the abdomen usually have their post synaptic neuron?
Neurons located in the prevertebral ganglia
What are splanchnic nerves? Are they specifically SNS or PSNS?
Nerves that convey impulses to visceral organs. Can be SNS and PSNS
What do the cardiopulmonary splanchnic nerves do? Does it contain postsynaptic or presynaptic neurons?
Enter the cardiac, pulmonary and oesophageal plexi .
They’re designed for the lungs, heart and oesophagus.
Contains post synaptic neurons.
What does the abdominopelvic splanchnic plexus do?
Does it contain postsynaptic or presynaptic neurons? Where do they all synapse? What is the exception?
It supplies the intestines and stomach.
Contains presynaptic neurons.
The presynaptic sympathetic nerves pass to the prevertebral ganglia through the abdominopelvic splanchnic nerves
They all synapse prevertebral ganglia except for the fibres innervating the adrenal glands.
What parts does the abdominopelvic splanchnic plexus consist of?
Greater - (T5-T9)
Lesser - T9-T10/11
Least - T12
Lumbar splanchnic nerves - L1-L3
Where do the pelvic splanchnic nerves arise from?
The pelvic splanchnic nerves arise from the ventral rami of spinal nerves S2-S4
