Module 3 Lecture 8: Central & Peripheral Nervous System Flashcards
Nervous system splits into?
- Central Nervous System
- Peripheral Nervous System
What composes the C.N.S. & P.N.S
Central Nervous System = Brain + Spinal Cord
Peripheral Nervous System = Nerve Fibres
PNS = connection between the CNS and effectors
Why is there no “nerve” in the central nervous system?
The central nervous system is known as the place where signals are received so instead of saying nerves we can say “pathway” for the group of axons
Nerve fibres come together to create a pathway/tract/commissure
What is Afferent? What is Efferent?
Afferent = signal that goes towards the CNS
Efferent = motor signal that leaves the CNS => PNS => Effector
What can the efferent (motor) division be further divided into?
- Somatic Nervous System
- Autonomic Nervous System
What does the Somatic Nervous System specialize in?
Controlling voluntary responses
* i.e. Muscle contraction
What’s special about the Somatic Nervous Systems Cell bodies?
Cell bodies of the neurons in this system are located in the brainstem & ventral horn of the spinal cord
Somatic Nervous System Neurons ===> A.K.A. Motor Neurons
What does the autonomic nervous system specialize in?
Sending motor signals to cardiac muscle, smooth muscle and glands
What are the three functional classes of neurons? Explain how they work together
Afferent Neurons in PNS:
* Creates an action potential in response to a long stimulus
* Long Peripheral Axon = Afferent Fibre (sending signal to CNS)
* Cell body: Found adjacent to the spinal cord
Interneurons:
* Link between afferent and efferent system
* Integrates peripheral responses to peripheral information
Efferent Neurons Crossing From CNS to PNS:
* Cell bodies in CNS
* Axons in PNS
* Signal originates from brain or received from interneuron
Axon terminal of Afferent Neurons peak into CNS => Synapse with interneurons
What is a ganglion? Purpose?
Cluster of neuronal cell bodies located in the PNS
* They coordinate & relay signals from different neurons
Explain what’s happening in the picture?
- Cell body of the presynaptic neuron carries a signal down its preganglionic fibre
- Preganglionic fibre synapses with cell body of the second neuron in a ganglion
- Axon of the second neuron (post ganglionic fibre) releases NT to the effector
Varicosity = Increased SA of the postganglionic fibre so that it hits more of the effector
* Numerous swellings that release NT to hit larger area of organs
Autonomic Nervous System has two subdivisions which are?
- Parasympathetic Nervous System
- Sympathetic Nervous System
Where is the Sympathetic Nervous System located?
Thoracic to lumbar region (T1-L2)
How do the ganglionic fibres vary in length when it comes to the sympathetic nervous system?
- Preganglionic fibres are short as they synapse in the sympathetic ganglia chain along the spinal cord
- Postganglionic fibres are long as they innervate effector organs
Sympathetic Ganglia Chain
A long chain of ganglia that connect to one another and run down the spinal cord
preganglionic fibres are short and precede the sympathetic ganglion chain
Where in the picture does the sympathetic preganglionic fibres pass through the sympathetic ganglion
It passes through the yellow circles which are the sympathetic ganglion chain which extend down the thoracic and lumbar
