Week 2- Peripheral Nervous System Flashcards
How can the PNS be divided up?
Somatic and autonomic.
Sensory (afferent) carry info towards CNS
Motor (efferent) nerves carry info away from CNS
How many pairs of cranial nerves do we have?
12 (have names)
How many pairs of spinal nerves do we have?
31 (spinal nerves have a letter and number)
What do the somatic afferent and efferent nerves do?
Afferent: from skin, skeletal muscle and joints
Efferent: to skeletal muscles
What is a dermatome?
An area of skin that is supplied by a single spinal nerve
What is a myotome?
A group of muscles innervated by a single spinal nerve
What does anasthesia mean?
No sensation
How can visceral (autonomic) nerves be catagorised?
They carry info from viscera (organs)
Can be divided into…
Parasympathetic: innervate viscera only
Sympathetic: innervate viscera and periphery
What’s a ganglion?
A collection of cell bodies outside the CNS
What’s a nucleus?
A collection of cell bodies inside CNS
What’s a plexus?
A network of interconnecting nerves
Where are the cell bodies of afferent fibres found?
In the spinal ganglia
Where do visceral efferent nerves synapse?
In a peripheral ganglion
What are the bundles that peripheral nerves are arranged into?
Fasciculi
What are the layers of connective tissue of a nerve?
Epineurium: external vascular layer
Perineurium: individual fascicles covered in
Endoneurium: individual axons covered by this layer
How are peripheral nerves classified?
Letters A-C (A being fastest) based on conduction velocity
Numbers I-IV (I being largest) based on axonal diameter
How are sensory receptors classified?
They can detect external or internal info
External: exoreceptors (pain, temp, touch, pressure)
Internal: proprioreceptors (movement, joint position)/enteroreceptors (movement through gut, blood pH)
Or by mode of detection: chemo/photo/thermo/mechano receptors or nociceptors
What are the structures in the proprioreceptors and their functions?
Muscle spindles: detect changes in muscle length
Golgi tendon organs: detect changes in tension in tendons
Joint receptors: found in joint capsules, detect start and end of movement
What’s a neuromuscular junction?
A specialized synapse between a motor neuron and a muscle fibre
What is a motor unit?
A single motor neuron and all the muscle fibres it innervates, stimulation of it causes contraction of all muscle fibres in that unit
What is required for a reflex action?
An afferent and efferent limb
What is a reflex action?
An involuntary pattern of muscle contraction and relaxation elicited by peripheral stimuli
What does the visceral sensory part of the autonomic nervous system do?
Relays sensory information from the core ie pain, fullness, blood pressure
What nerves are part of the visceral sensory autonomic nervous system?
T1-L2, S2-S4, cranial nerves 9&10
What does the visceral motor part of the autonomic nervous system do?
Outflow to core and body wall, controls pupils, sweat and salivary glands, heart muscle, airways
What nerves are part of the visceral motor autonomic nervous system?
Thoracolumbar T1- L2, craniosacral outflow ie cranial nerves 3/7/9/10
Describe the anatomy of sympathetic outflow to the periphery
T1- L2 has an extra part of grey matter.
- Efferent fiber comes out and goes down spinal nerve
- The nerve synapses in the sympathetic paravertebral trunks (enlarged due to ganglionic neurones)
- They then go up, down or straight out to the skin
Describe the anatomy of sympathetic outflow to the viscera
Same as outflow to periphery but the nerves don’t synapse in the sympathetic trunk, they synapse in the pre aortic ganglia
Describe the anatomy of parasympathetic outflow to the viscera
Cranial outflow: cranial nerves 3/7/9/10
Sacral outflow: via splanchnic nerves S2-S4
Describe the effect of the parasympathetic and sympathetic branches of the autonomic nervous system on eyes
P: pupil constricts
S: pupil dialates
Describe the effect of the parasympathetic and sympathetic branches of the autonomic nervous system on the salivary glands
S: inhibits
P: enhances
Describe the effect of the parasympathetic and sympathetic branches of the autonomic nervous system on the heart
S: increases rate and force of outflow
P: decreases rate and force of outflow
Describe the effect of the parasympathetic and sympathetic branches of the autonomic nervous system on the lungs
S: dilates bronchus
P: constricts bronchus
Describe the effect of the parasympathetic and sympathetic branches of the autonomic nervous system on the stomach
S: inhibits digestion
P: stimulates digestion
Describe the effect of the parasympathetic and sympathetic branches of the autonomic nervous system on the kidneys
S: stimulates secretion of epinephrine and norepinephrine
P: none
Describe the effect of the parasympathetic and sympathetic branches of the autonomic nervous system on the liver
S: stimulates glucose release
P: stimulates bile release
Describe the effect of the parasympathetic and sympathetic branches of the autonomic nervous system on the intestine
S: stimulates peristalsis and secretion
P: inhibits peristalsis and secretion
Describe the effect of the parasympathetic and sympathetic branches of the autonomic nervous system on the bladder
S: relaxes bladder
P: contracts bladder
