Module 3: Lecture 7 Flashcards
what are the two components of the nervous system?
- central nervous system (CNS)
- peripheral nervous system (PNS)
what part of us is our central nervous system?
the brain and spinal cord
what part of us is our peripheral nervous system?
nerve fibers
- all the extra nervous tissue, predominantly nerves
what brings information either toward or away from the spinal cord?
the peripheral nervous system
what does ‘afferent’ in regards to the peripheral nervous system mean?
you are carrying information towards the spinal cord
- ex. touch receptors - from periphery to the CNS
what does ‘efferent’ in regards to the peripheral nervous system mean?
you are carrying information away from the spinal cord
ex. walking around - motor commands from CNS that allows us to move around and communicate
what is the peripheral nervous system?
connection between the CNS and effectors/receptors located in other parts of the body
when do we refer to specific nerve bundles?
when talking about the PNS
what is a pathway/tract?
groups or bundles of nerves or axons within the CNS
what are the two divisions of the efferent division of PNS?
- somatic nervous system
- autonomic nervous system
what are the two divisions of the autonomic nervous system?
- sympathetic nervous system
- parasympathetic nervous system
which systems of the efferent division do you have conscious and voluntary control over vs unconscious and involuntary?
conscious and voluntary- somatic
unconscious and involuntary- autonomic
do the pathways of the efferent and afferent divisions utilize the same neurons?
no, different neurons
what is the pathway of the afferent division?
- from a receptor to the CNS
what is the pathway of the efferent division?
- carries information away from the CNS toward the end effector organs or muscles
what does the somatic nervous system control?
skeletal muscles
the cell bodies of the neurons of the somatic nervous system are located where?
in the brainstem and the ventral horn of the spinal cord
- spinal cord
what are the neurons of the somatic nervous system?
motor neurons
what does the autonomic nervous system innervate?
- all of your internal organs that have some sort of neural input on them
ex:
- the smooth and cardiac muscles
- glands
- adipose tissue, liver, other neurons from the gastrointestinal tract
what is the structure of the afferent neuron in PNS?
- sensory receptor within the periphery that generates the action potential which will travel towards the CNS
- has a long peripheral axon which is the information traveling back to the CNS
- cell body located next to the CNS next to the spinal cord
- axon terminals project slightly into CNS
what does a sensory receptor do?
generates an action potential in response to a stimulus
how does an afferent neuron get into the CNS?
the touch receptor (sensory receptor) generated an action potential in response to that stimulus and then the axon terminals will project into the CNS, into the spinal cord, where it will synapse
how does the cell body of an afferent neuron in PNS look like?
- adjacent to the spinal cord
- has no dendrites
what is responsible for most of our neural tissue?
our interneurons
- around 99% of our neurons are interneurons
what is the link between our afferent and efferent systems?
interneurons
what is important to integrating peripheral responses to peripheral information?
interneurons
ex. touch something hot –> interneurons relay signal to efferent neurons to withdraw hand (reflex)
which part of efferent neurons are in which systems? why?
efferent neurons cross from CNS to PNS. the cell body is in the CNS, and the axons are in the PNS. this is because the signal originates in the brain or received from interneuron
what does your autonomic nervous system control?
a whole host of organs
- all of the internal organs that are regulated by neural pathways
true or false: the autonomic nervous system is always composed of a two neuron chain
yes
in the autonomic nervous system, what communicates or innervated the end effector organ?
the second neuron
what part of the first neuron (preganglionic neuron) of the autonomic nervous system is in the CNS and which is in the PNS?
- cell body in CNS
- axon in PNS
in the autonomic nervous system, what do we call the pre and post synaptic neuron instead?
- preganglionic neuron
- postganglionic neuron
where does the postganglionic neuron sit?
within the ganglion
what is a ganglion?
cluster of neuronal cell bodies outside of the CNS
each autonomic neural pathway extending from the CNS to an innervated organ is a ____________.
two-neuron chain
- preganglionic neuron sits within the CNS, axon projects out towards the peripheral nervous system where it synapses with the second neuron in the ganglia
what is the axon of the second neuron in the autonomic nervous system called?
postganglionic fibre
what is the axon of the first neuron in the autonomic nervous system called?
preganglionic fibre
- it synapses with the cell body of the second neuron in a ganglion
what is a varicosity?
- the output zones of our postganglionic neurons
- swelling and numerous branching of the axon terminal of the output zone of the postganglionic neuron so that it can release neurotransmitters over very large areas rather than single cells so that you can influence an entire organ rather than one specific cell
what region of our body is the sympathetic nervous system?
from the thoracic and lumbar regions of the spinal cord
what region of our body is the parasympathetic nervous system?
from the brain and sacral/lower spinal cord
are the preganglionic fibres shorter than the postganglionic fibres in the sympathetic nervous system?
preganglionic fibres are shorter than the postganglionic fibres in the sympathetic nervous system
what do the preganglionic fibers of the sympathetic nervous system travel into?
the synaptic ganglia chain (‘sympathetic trunk’) that is located along the side of the spinal cord
what does the postganglionic fibres of the sympathetic nervous system innervate?
effector organs
are the preganglionic fibres shorter than the postganglionic fibres in the parasympathetic nervous system?
the preganglionic fibres are longer. so long that they will reach a terminal ganglion in or near the effector organ
- very short postganglionic fibres ending on cells of an organ itself
where is the sympathetic ganglion chain?
next to the spinal cord on both sides
most sympathetic preganglionic fibres pass through the sympathetic ganglion chain which extend?
down the thoracic and lumbar region of the spinal cord on both sides
do parasympathetic ganglion pass through ganglion near the spinal cord?
no
what is the sympathetic ganglion chain used for?
to ensure that the sympathetic system can relay and coordinate signals across the entire thorax
what do all your preganglionic neurons utilize to synapse/communicate with our postganglionic neurons?
acetylcholine
what differs in the postganglionic neuron from the sympathetic and the parasympathetic nervous system?
- what they secret at the end effector organ
what does your parasympathetic system utilize for your postganglionic neuron to communicate with the end effector organ?
acetlycholine
what does your sympathetic system utilize for your postganglionic neuron to communicate with the end effector organ?
norepinephrine
when would we refer to a fibre as cholinergic fibres?
if it releases acetylcholine
when would we refer to a fibre as adrenergic fibres?
if it releases norepinephrine
what does the adrenal medulla release?
norepinephrine AND epinephrine
what are most organs controlled by?
both sympathetic AND parasympathetic innervations
- often they have opposing affects
do the parasympathetic and sympathetic systems turn off as one turns on?
no, they are both partially active
- although one will show dominance for the overall response
which system is your “fight-or-flight”?
sympathetic nervous system
what are the advantages of always have both of your autonomic systems parcially active?
- easier/faster to change a systems activity if it is already running
- reduces the chances of one system being over-activated when a stimulus is provided
