Intro to Central nervous system Flashcards
Name the two divisions of the structural nervous system.
- CNS (brain and spinal cord)
- PNS (everything else … spinal nerves, cranial nerves, ganglia, plexuses)
Name the 2 functional divisions of the nervous system. Explain what they mean.
- Afferent (= sensory) : bring back sensory information back to the CNS.
- Efferent (= motor) : stimulate muscles to contract & gland to secrete.
What do the terms somatic and visceral refer to :
Somatic : motor innervation of voluntary muscles (think skeletal muscle and skin)
Visceral : motor innervation of involuntary muscles (think smooth muscles such as viscera, cardiac muscle and glands).
The efferent (motor) division can act on the _____ nervous system or the ______ nervous system.
Somatic nervous system
Autonomic nervous system
Parasympathetic ‘’rest & digest’’ and sympathetic ‘’fight or flight’’ are branches of the ____ nervous system.
Autonomic nervous system.
Define the neuron.
The neuron is the structural & functional unit of the nervous system.
It is composed of a cell body and nerve cell processes (dendrites & axons).
Dendrites receive _____.
Axon produce ______.
Incoming signals
Outgoing outputs
What are collection of axons called in the PNS ?
What are they called in the CNS ?
Nerve & tracts respectively.
Compare nucleus and ganglion.
Nucleus is a collection of nerve cell bodies in the CNS .
Ganglia is a collection of nerve cell bodies in the PNS.
Compare unipolar, bipolar and multipolar types of neurons.
Unipolar (pseudounipolar) : relate to sensory function = afferent.
Bipolar : associated with special senses (retina, inner ear).
Multipolar : relate to motor function = efferent
Unipolar / sensory neurons have their cell bodies in the _____.
Dorsal root ganglion.
The DRG is a cluster of neurons in the dorsal root of the ganglion
ALL sensory nerve cell bodies are located in the dorsal root ganglia.
Differentiate white matter from gray matter.
Gray matter is mainly composed of neuron cell bodies.
White matter is mainly composed of neuron axons.
Remember that axons are covered with myelin which is white!
Sensory nerve cell bodies are located in the DRG.
Motor ones are located in the _____.
Sympathetic chain ganglia.
Define glial cells and gives 4 examples.
Glial cells are supporting cells of the nervous system (greatly outnumber neural cells)
E.g.
- Astrocytes*
- Microglia*
- Schwann cells*
- Oligodendrocytes*
Schwann cells (neurolemmocytes) are _____ forming cells in the ___.
Myelin
PNS
Oligodendrocytes are ____ forming cells in the ____.
Myelin
CNS
What are Astrocytes ?
Astrocytes are specialized glial cells that outnumber neurons by over fivefold. They contiguously tile the entire central nervous system (CNS) and exert many essential complex functions in the healthy CNS.
They form the blood/brain barrier.
What are microglia?
Microglia are the resident innate immune cells of the CNS and are responsible for normal maintenance of CNS tissue as well as the local response to injury or infection.
They act as phagocytes within the CNS.
They act as the ‘‘glue”“
Nerves can convey several types of axons. Name the 4 different general components of a nerve.
General Somatic Afferent (GSA)
General Somatic Efferent (GSE)
General Visceral Afferent (GVA)
General Visceral Efferent (GVE)
Describe GSA nerves.
General Somatic Afferent nerves transmits pain, touch, temperature & proprioception from the body to the CNS.
Describe General Somatic Efferent nerve (GSE)
General Somatic Efferent : motor impulses to skeletal muscles.
Describe General Visceral Afferent (GVE) neurones.
GVA : sensory info from visceral organs to CNS.
General Visceral Efferent (GVE) :
Motor to cardiac, smooth muscles & gland cells.
Name the 3 SPECIAL functional components of a nerve:
- Special Somatic Afferent (SSA)
- Special Visceral Afferents (SVA)
- SpecialVisceral Efferents (SVE)
Define SSA neurones.
Sensations of vision, hearing and equilibrium to the CNS.
Define SVA :
Special Visceral Afferent : taste and smell to CNS.
Define SVE neurons.
Special Visceral Efferent : Motor to certain muscles of the head & neck (mastication, facial expression, some muscles of the pharynx/larynx)
The peripheral system consists of _____ pairs of cranial nerves which exit the skull through a foramina AND ___ pairs of spinal nerves which exit through intervertebral foramina.
12 pairs of cranial nerves
31 pairs of spinal nerves
What is a spinal cord segment ?
A portion of the spinal cord that gives rise to a pair of spinal nerves (left and right).
There are 31 pairs of spinal nerves.
How many pairs of spinal nerves come from the cervical region ?
8 pairs
*** Note that there is 8, even though there are 7 cervical vertebrae. The first pairs starts above the first segment.
How many pairs of spinal nerves originate from the thoracic, lumbar, sacral and coccygeal regions?
12 thoracic
5 lumbar
5 sacral
1 coccygeal
Explain the following image.
What distinguishes a root from a ramus ?
Think of the spinal nerve as the trunk of a tree - the word ramus means branch in Latin, so the primary rami are the branches of a spinal nerve, whereas the roots unite to form the spinal nerve. These terms are very easy to confuse. The primary rami are mixed nerves carrying both motor and sensory fibers.
What is a mixed nerve ?
Mixed nerves are composed of both motor and sensory fibers, and transmit messages in both directions at once. Together, the nerves make up the peripheral nervous system.
E.g. Spinal nerves
What does the dorsal (posterior) rami of a spinal nerve supply ?
- facet joints of the vertebral column
- deep muscles of the back (erector spinae)
- Skin of the back
What does the ventral (anterior) rami of a spinal nerve supply?
Everything else except back area ;
- most anterior neck muscles
- anterior lateral & thoracic & abdominal & pelvic walls
- Entire upper limbs
- Entire lower limbs
What are the 31 segments of the spinal cord ?
The spinal cord divides into 31 segments: cervical 8, thoracic 12, lumbar 5, sacral 5, and coccygeal 1.
Where do roots unite to form a spinal nerve ?
At the intervertebral foramen.
The dorsal and ventral roots are the only sites where motor and sensory fibers. Only at this locations can a surgeon selectively cut either functional components for the relief of pain or spams . This procedure is called ____.
Rhizotomy
About the ventral rami. The typical spinal nerves that occur between T2 and T12 are called_______.
Intercostal nerves.
Most ventral rami merge and intermingle w/ one or more adjacent ventral rami to form a ______.
Plexus (network)
Define dermatome.
The band like area of skin whose sensation is supplied by a spinal cord segment.
Define Myotome.
The area of skeletal muscle receiving motor innervation by 1 spinal cord segment.
True or false. At least 2 adjacent spinal nerves must be interrupted to produce a discernable area of numbness.
True.
Cutting a single nerve rarely results in numbness over the area demarcated for that nerve because the axons conveyed by adjacent spinal nerve overlap.
What are spinal reflexes ?
Spinal reflexes are those in which the sensory stimuli arise from receptors in muscles, joints and skin, and in which the neural circuitry responsible for the motor response is entirely contained within the spinal cord.
Explain the difference between monosynaptic and polysynaptic reflexes.
The autonomic nervous system involves ______ functions of the body.
Involuntary
As opposed to the somatic nervous system, how many neurones does it take from the CNS to the target organ ?
2
What are the 3 target organs that the autonomic nervous system supply?
Smooth muscles
Cardiac muscle
Gland cells
What are the 2 divisions of the autonomic nervous system?
Sympathetic
Parasympathetic
True or false. Most organs have dual innervation with both sympathetics and parasympathetic innervation.
True
Define the enteric nervous system.
A subdivisoin of the sympathetic, and parasympathetic (mainly)
Represents a collection of neurons embedded within the wall of the entire GIT and its derivates.
It controls the GI motility + secretions
This entire system is contained within 2 plexuses (Myenteric/Auernbach’s and Submucous/Meissner’s)
The parasympathetic or ‘’rest and digest’’ is also called _________.
Craniosacral (Cranial nerves 3, 7, 9, 10 & Spinal cord segments S2,3, 4)
In the autonomic system, where are the preganglionic nerve cell bodies located ?
CNS (nuclei of brainstem)
Which cranial nerve supplies 75% of the parasympathetics of the body and is also referred to as the vagabond or wandering nerve?
Vagus nerve
Exactly where are the preganglionic parasympathetic nerve cell bodies located ?
Dorsal motor nucleus of medulla
What does the vagus nerve innervate ?
Neck
Thorax
GIT (foregut and midgut)
Where are the postganglionic nerve cell bodies located in the parasympathetic system ?
In the walls (intramural) of organ.
True or false. The parasympathetic nerves have long preganglionic axons and short post ganglionic axones?
True.
The parasympathetic innervation of the hindgut (from splenic flexure of the colon to the anus) & pelvic organs is via the _________.
Pelvic splanchic nerves.
The nerves that make up the sympathetic nervous system originate from ____ & ______ spinal nerves.
Thoracic
Lumbar
(Thoracolumbar)
What is the location of ALL pre-ganglionic nerve cell bodies of sympathetic nerves ?
Lateral horn (colum) of gray matter from T1-L2
What is the location of many (not all) post ganglionic sympathetic nerve cell bodies ?
The sympathetic trunk = paravertebral ganglia = chain ganglia
Whenever you hear splanchnic nerve, it is ___ ganglionic.
PRE ganglionic
Name the two types of ganglia of sympathetic nervous system
Paravertebral
Preverterbral (aka pre-aortic)
Explain this image in details.
True or false. Sympathetics have short preganglionic axons and long postganglionic axons.
True.
Give an exemple of a modified sympathetic ganglion and explain why.
Preganglonic axons that are going to supply adrenal medulla pass paravertebral and prevertebral ganglia without synapsing and pass all the way through the adrenal medulla.
Explain this
Name the different effects the fight or flight response has
Describe visceral afferent nerves :
They provide information about the condition of the body’s internal environment. This info is integrated into the CNS usually without our conscious knowledge.
What regulates blood pressure and blood chemistry by altering function such as the hearth and respiratory rate and vascular resistance ?
Visceral reflexes.
What is the role of visceral afferent nerves
Provide info about the condition of body’s internal environment.
