4d PNS Flashcards
What are the two major divisions of the nervous system?
CNS and PNS
Central and peripheral
What constitutes the CNS?
Brain
Spinal cord
Integrates incoming information and coordinates all voluntary and involuntary nervous functions
What does the peripheral nervous system consist of?
Ganglia
Nerves that branch from the CNS
Keeps the CNS in contact with the rest of the body
What types of nerves make up the PNS and what are their functions?
Cranial: take impulses to and from the brain and brain stem
Spinal: take impulses to and away from the spinal cord
Ganglia: collections of nerve cell bodies
Basically all bring information back to brain tracts
In which system are tracts found?
Central
How many cranial nerves are there?
12 pairs
How are cranial nerve organized/categorized?
By name and number
What region do these nerves typically serve?
Head and neck (cervical and neck region)
Exception: nerve 10, vagus nerve, extends to the thoracic and abdominal cavity
What does it mean for cranial nerves to be mixed?
They contain both motor and sensory nerves
What cranial nerves are purely sensory?
1: olfactory
2: optic
8: vestibulocochlear
What pair of cranial nerves extend beyond the head and neck region?
Vagus nerve
What do the motor fibres in the vagus nerves do?
Parasympathetic fibres
Signal to the heart, lungs, abdominal viscera (heart rate, breathing and digestion)
What do the sensory fibres in the Vagus Nerves do?
Carry impulses from thoracic and abdominal viscera, baroreceptors, chemoreceptors, and taste buds of posterior tongue and pharynx
Where does the spinal cord begin and end?
Begin: foramen magnum (hole in vertebrae at base of neck)
Ends: first or second lumbar vertebra
How many pairs of spinal nerves are there?
31 pairs
Are spinal nerves mixed? What does that mean?
Yes, they are mixed
Have both sensory and motor nerves
How are spinal nerves named/categorized?
According to where they emerge from (ie: cervical, thoracic, lumbar, cauda equina)
What is the Cauda Equina?
Collection of spinal nerves at the inferior end
Where is white matter in the spinal cord (more superficial or deep)?
Superficial
Where is the dorsal root ganglion located (anterior or posterior)?
Posterior/dorsal
Good indication of which view you are in
What does it mean to reference the dorsal/lateral/ventral horn of gray matter?
Gray matter, found deep in the vertebrae, kind of have a butterfly shape. The specific horns refer to which end of the wings you refer to
What is gray matter in the spinal cord mainly composed of?
Cell bodies
What specifically can be found in the dorsal horns of the gray matter?
Cell bodies of interneurons
Receive information from sensory neurons in the dorsal root
Where is the dorsal root located?
Medial to the dorsal root ganglion
Is the dorsal root ganglion a part of the spinal cord?
No
Interneurons in the spinal cord communicate with sensory neurons in the dorsal root. Where specifically are the interneurons and cell bodies of sensory neurons found?
Interneurons: dorsal horns
Cell bodies of sensory neurons: dorsal root ganglion
-> distinction: the site of communication between interneurons and sensory neurons occurs at the cell body of the interneurons but at the axon terminal of the sensory neuron, so it makes sense that the cell body is further out
What can be found in ventral horns?
Cell bodies or motor neurons of the somatic (voluntary) nervous system
What do motor neurons pass to send information to the somatic nervous system? Hint: they start in the gray matter of the spinal cord
Ventral root
What surrounds the central canal? What is it filled with?
Surrounded by gray matter
Filled with cerebrospinal fluid (CSF)
What is the white matter of the spinal cord composed of?
Myelinated fibre tracts
Define the directions of sensory and motor tracts.
Sensory tracts: conduct impulses toward brain
Motor tracts: carry impulses from brain to skeletal muscles
Where exactly does a spinal nerve begin? Describe that geography.
From the spinal cord, the dorsal root and dorsal root ganglion leave the dorsal side, the ventral root leaves the ventral side, and the come together to from the spinal nerve
How long is the true spinal nerve?
Only about a centimetre long
What does the spinal nerve separate into?
Ventral and dorsal ramus
What does “ramus” mean?
Branch of a spinal nerve containing both motor and sensory fibres
What are the three types of rami types we know?
Dorsal rami
Ventral rami (t1-t12)
Ventral rami (EXCEPT t1-t12)
What are the dorsal rami in control of?
Serve the skin and muscles of the posterior trunk
What does the ventral rami of T1-T12 control?
Forms the intercostal nerves that supply muscles and skin of the ribs and trunk
What do the ventral rami excluding T1-T12 control?
Form a complex network/plexus of sensory and motor nerves for the limbs
Ventral rami extend from a single nerve and join with axons from adjacent nerves to form a plexus (kinda looks like a braid)
What is a plexus?
A network, an interconnection, of sensory and motor fibres that form new combinations as the peripheral nerves
What are the 4 voluntary plexuses and what do they control?
Cervical plexus: posterior head, neck, shoulders and diaphragm
Brachial plexus: upper limbs, some neck, shoulder muscles
Lumbar plexus: abdominal wall, external genitals, part of the lower limbs
Sacral plexus: buttocks, perineum, lower limbs
The PNS is divided into sensory and motor. Motor can be further divided into what sub categories?
Somatic Nervous System: stimulates skeletal (voluntary) muscle
Autonomic Nervous System: controls muscles in heart, smooth muscle in internal organs such as intestines, bladder and uterus (involuntary)
What is teh main purpose of the autonomic nervous system?
Maintain the internal environment of the human body in homeostasis, especially after trauma
Reacts to internal/external changes by regulating things like: blood pressure, heart rate, vascular sal concentrations
What to the autonomic and somatic sub divisions have in common?
Both involve reflexes and connections to the CNS
Both use unipolar and multipolar sensory neurons, interneurons and motor neurons
What do the autonomic and somatic systems differ in?
In the effectors
In their efferent pathways
In their target organ responses to their neurotransmitter
Where do motor neuron cell bodies originate for the somatic nervous system? Autonomic?
Somatic: in the CNS
Autonomic: chain of 2 motor neurons
-preganglionic neuron is in the brain/spinal cord
-postganglionic neuron extends to the organ
What are the subdivisions of the autonomic nervous system?
Sympathetic: fight or flight
-exercise, excitement, emergency, embarrassment (E)
Parasympathetic: rest and digest
-digest, defecate, diuresis (D)
What do cholinergic nerve fibres release? Type of effects?
Acetylcholine
Stimulatory effect on skeletal muscle
Inhibitory effect on cardiac muscle
What do adrenergic nerve fibres release? Effect?
Norepinephrine, epinephrine, or dopamine
Effect: fight or flight response
-increase heart rate, increase blood flow to skeletal muscle, increase breakdown of glucose stores (causing spike)
What do the sympathetic and parasympathetic systems have in common?
Both operate continuously along with the rest of the nervous system
-they dont switch on and off when required but rather respond at various degrees to info provided by sensory system
Under what circumstance does parasympathetic dominate? Sympathetic?
Parasympathetic: times of emotional calm, physical rest
Sympathetic: stressful times
Where is the thoracolumbar division located?
Between the thoracic and lumbar regions
What types of neurons originate from T1 to L2? Where do they go?
Preganglionic motor neurons
Pass through a ramus communicants to enter a sympathetic trunk ganglion
Where is the sympathetic trunk located?
Lies near the spinal cord
Runs down the length of the spinal cord on both sides, connects 22 pairs of ganglia
How many pairs of ganglia make up the sympathetic trunk ganglia?
22 pairs
What happens in the sympathetic division after the preganglionic neuron synapses at the ganglion?
It may synapse with a postganglionic neuron at the same or different level
Or is may pass through the ganglion without synapsing and form part of the splanchnic nerves
What do splanchnic nerves do?
Travel to the collateral ganglion
What do collateral ganglia do?
Serve the abdominal and pelvic organs
What do sympathetic pathways do?
Trigger a response in the body, mobilize it
What types of fibres do preganglionic and postganglionic neurons have?
Preganglionic: cholinergic fibres
Postganglionic: adrenergic fibres
Is there a size difference in preganglionic and postganglionic neurons in sympathetic and parasympathetic divisions? Why?
Yes
Parasympathetic: originate in cranium (craniosacral) and has to make its way to effector organ. Results it long preganglionic and short post
Sympathetic: originates in thoracic region (thoracolumnar) and are not far from the sympathetic ganglion trunk where they synapse. Then they synapse with post ganglionic neuron, which is farther. Results in short pre long post
What structures only receive input from the sympathetic nervous system?
Adrenal glands, skin, blood vessels
What’s another name for the sympathetic division?
Thoracolumbar
What’s another name for the parasympathetic division?
Craniosacral
In the parasympathetic division, where do preganglionic neurons originate?
Cranial nerves 3, 7, 9, 10
III, VII, IX ,X
S2 through S4 regions of the sacral spinal cord
What so preganglionic neurons of the parasympathetic system synapse with?
Terminal ganglia, from there postganglionic axons extend to organs
What is the purpose of a parasympathetic pathway?
To conserve energy and relax
Where are the autonomic/terminal ganglia located in the parasympathetic pathway? What does this result in?
On or near the effector organ
Results in a long preganglionic neuron and a short postganglionic neuron
What do pre and postganglionic neurons have in common in the parasympathetic pathway?
Cholinergic fibres
By what division of the autonomic nervous system are body organs served? Exceptions?
Receive fibres from both divisons
Blood vessels, structures of the skin, some glands, adrenal medulla
-only receive sympathetic fibres
What happens when both the sympathetic and parasympathetic systems serve the same organ?
They cause antagonistic effects due to the release of different neurotransmitters
What neurotransmitter is released at the preganglionic neurons of the sympathetic and parasympathetic divisions?
Both release acetylcholine
What neurotransmitter is released from post ganglionic neurons in the sympathetic and parasympathetic divisions?
Para: cholinergic fibres release acetylcholine again
Sym: adrenergic fibres release norepinephrine instead of
What are the effects of the sympathetic nervous system throughout the body?
Fight flight freeze
Dilation of pupils and airways
Increase heart rate, force of contraction, blood pressure and respiratory rate
Decrease flow to non essential organs (ie. digestive)
Increase flow to skeletal and cardiac muscle
Increase blood glucose levels
Also activates adrenal medulla to secrete epinephrine and norepinephrine
What effects does the parasympathetic nervous system have on the body?
Basically the opposite effects of the sympathetic
Most active in the bodys restorative processes
Dominant when individual is relaxed and non-threatened
-Promoting normal digestion
-Elimination of feces and urine
-Conserving and storing body energy
-Decreasing demand on cardiovascular system
What does the corpus callosum do?
Connects the left and right hemispheres of the brain
Where do spinal nerves extend?
Between vertebrae
Which nerves does the cervical plexus include?
C1-C4
Which nerves does teh brachial plexus include?
C5-T1
WHich nerves does the lumbar plexus include?
L1-L4
Which nerves does the sacral plexus include?
L4-S5
