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Lecture 23: Peripheral Nervous System

Terms in this set (41)

what are cranial nerves
- located in the peripheral system
- 12 pairs: mixed nerves, sensory impulses, and brainstem
what are the brainstem cranial nerves
- 10/12 pairs of these
- cranial nerves 3 to 12
what are the sensory impulse cranial nerves
- 3/12
- for olfaction, optic, and vestibulocohlear
what are the mixed nerves of the cranial nerves
- 9/12 are mixed meaning they carry sensory and motor information
- cell bodies of motor neurons in mixed neurons are located in nuclei of the brainstem
- the cell bodies of sensory neurons in mixed neurons are located in ganglia outside of the CNS
what are spinal nerves
- 31 pairs
- all are mixed containing both sensory and motor neurons
what are the two attachments of the spina nerves
- dorsal root: revives sensory information and cell bodies are located in the dorsal root ganglion
- ventricle root: carriers motor output: located in the ventral or lateral horn
what are the types of spinal nerves
- 8 cervical (C1-C8)
- 12 thoracic (T1-T12)
- 5 lumbar (L1-L5)
- 5 Sacral (S1-S5)
- 1 coxxygeal (C0)
What do the spinal nerves branch into
- dorsal ramus: innervates the skin and the muscles of the back
- ventral ramus: innervates the thoracic nerves and the plexus
- rami communicates: forms a component of the autonomic nervous system
what is the location of the spinal nerves
- located at the joint of the dorsal and ventral root
- all exit through the intervertebral foramina of of the vertebrae
what is the spinal plexuses
- are formed from the ventral rami of the spinal nerves (except T2-T12)
- Are a network of nerves
- 4 plexuses: cervical, brachial, lumbar, and sacral
what is the cervical plexuses in the spine
- C1-C4
- all phrenic nerves in the diaphragm
what is the brachial plexuses in the spine
C5-T1
- axillary, radius, ulna ,and the median nerves
what is the lumbar plexuses in the spine
- L1-L5
- femoral nerve
what is the sacral plexuses in the spine
- L4-S4
-Sciatic nerve that is a combination of the tibial and the fibular nerves
what is the wrapping of the nervous tissue
- entire nerve wrapped in epineurium connective tissue
- each nerve fascicle is wrapped in perineurium
- each axon and corresponding myelin is wrapped in endoneurlium
what are receptor
- afferent pathways move sensory information to the CNS
- the receptors will detect changes in the internal and external environment
- pathway is stimuli, receptor, to the CNS
How are receptors classified
- location: exteroceptors and interoceptors
- type of stimuli: Mechanoreceptors, thermoreceptors, chemoreceptors, and photoreceptors
- structure: free nerve ending or encapsulated nerve ending
what is exteroreceptors
- detect stimuli in the external environment or very close to the body surface
- located in the skin
- ex. pain and touch
what are interoceptors
- detect stimuli in the internal environment
- proprioceptors located in the joint and the muscles
- ex. blood pressure
what are the types of stimuli
-Mechanoreceptors: Detect pressure, touch
- thermoreceptors: detect hot and cold
- chemoreceptors: detects chemicals
- photoreceptors: detect light
what are free nerve endings
- dendrites of sneery neurons
- ex. pain and itchiness
what are encapsulated nerve endings
- terminal dendrites of these nerves are enclosed in connective tissue
- ex. meissners corpuscle for touch
- don't pick up as much stimuli
what is the motor pathway
- efferent pathway
- CNS to effector cells like muscles etc
- consists of the somatic nervous system and autonomic nervous system
what are the 3 neurons of the ascending pathway
- 1st order
- 2nd order
- 3rd order
What are 1st order neurons?
- located in the spinal nerve
- part of the peripheral nervous system
- unipolar neurons containing receptors
- cell body is located in the ganglia outside of the CNS
- synapse onton 2nd order neurons in the dorsal horn of the spinal cord or brainstem
what are 2nd order neurons
- cell body is in dorsal horn of the spinal cord or the medulla
- multipolar interneurons that carry impulses to the thalamus
- located in the tracts
- decussates in the spinal cord or medulla
what are 3rd order neurons
- cell body is in the thalamus
- multipolar interneurons that carry information to the sensory cortex of the CNS
- located in tracts
what is the spinocerebelllar pathway
- consists of ascending tracts from spinal cord to cerebellum
- don't have any conscious perception of the activities in this pathway
- 1 order neuron: receptor here, proprioceptors that detect changes in balance and body position
- 2 order neuron: neuron goes to the cerebellum
- does not have 3 order neuron
what are the ascending tracts of the spinal cord
- non-specific ascending pathway and specific ascending pathway
what is a specific ascending pathway
- sensations that your able able to detect its origin
- ex. touch
- ex. dorsal columns in the dorsal column pathway, decussates in the medulla
what is the non specific ascending pathway
- when you are aware of a sensation but are unable to detect it origin
- ex. pain
- ex. spinothalamic tracts of the spinothalmic pathway. Decussates the spina cord, picks up pain, temp, and send the information to the thalamus
what is the somatic nervous system
- effector cells are all skeletal muscles
- consists of 2 neurons: upper motor neurons and lower motor neurons
what are upper motor neurons
- cell bodies are in the cerebral cortex and basal nuclei
- multipolar interneurons
- synapse onto the lower motor neurons
- has descending tract of the pathway
what is the descending tract of the pathway
- corticospinal (pyramid tracts): cell bodied are in cortex and 85% of these tracts decussate in the medulla
- indirect tracts: cell bodies are located in the brainstem
what are the upper motor neurons of the somatic nervous system
- located in PNS
- cell bodies are located in the ventral horn of the spinal cord
- neurons transmit information from the spinal nerves to the effector (skeletal muscle)
What is the autonomic nervous system two divisions
- sympathetic nervous system (SNS)
- Parasympathetic nervous system (PSNS)
What is the autonomic nervous system?
- effector cells are cardiac muscle, smooth muscles and glands
- goes from CNS to effector cells
- consist of the preganglionic neurons and postganglionic neurons
what are preganglionic neurons
- myelinated
- cell body is in the brainstem or spinal cord
what are postganglionic neurons
- unmyelinated
- cell body is located in the ganglia
characteristics of the sympathetic autonomic nervous system
- cell body of the preganglionic neuron is in the lateral horn of (T1-L2)
- autonomic ganglia is located in lateral and colateral
- postganglionic neuron is a long axon
- functions in fight or flight
- nerves thoracic
characteristics of the parasympathetic autonomic nervous system
- cell body of the preganglionic neuron is in the brainstem and grey matter of S2-S4
- autonomic ganglia is located in terminal
- postganglionic neuron is a short axon
- functions during rest and digestion
- nerves mainly vagus (multiple functions)
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