Lectures 6 & 7 Cranial and spinal nerves, sympathetic trunk Flashcards
Motor fibres can be either?
Somatic efferent to voluntary muscles or autonomic (visceral efferent) to smooth muscles and glands.
The autonomic nervous system consists of?
Sympathetic and parasympathetic divisions.
Sensory nerves are either concerned with?
Special senses of sell, taste, vision, hearing and balance
Describe somatic motor nerves
Axons/fibres arise from neurons in either brain or spinal cord. These axons pass into peripheral nerves (usually nerves of mixed function) & via these nerves directly to the skeletal muscle that they innervate. There is no second cell body.
Describe autonomic nervous system
- Parasympathetic and sympathetic divisions
- Autonomic nerves are involved in: secretion from glands (secretomotor), smooth muscle contraction in blood vessels (vasomotor), internal organs, erector pili muscles.
- Many but not all organs have a dual sympathetic and parasympathetic supply with opposite effects - e.g. one stimulating and the other inhabiting.
Autonomic pathways involve which two neurons?
The neuron of origin in the brain or spinal cord and a second one in a peripheral ganglion e.g. in sympathetic trunk or one of the cranial parasympathetic ganglia e.g. pterygopalatine ganglion.
Define ‘ganglion’
Collection of nerve cell bodies outside the central nervous system
Define ‘preganglionic fibres’
Myelinated axons of autonomic nerves which have not undergone a second synapse. Called post-ganglionic after this synapsing. Post ganglionic fibres are usually unmyelinated.
Parasympathetic nerves leave the brainstem via FOUR cranial nerves:
- Oculomotor (CN3)
- Facial (CN7)
- Glossopharyngeal (CN9)
- Vagus (CN10)
- And via 2nd and 4th sacral spinal nerves
Preganglionic fibres from these nerves synapse in:
- Ciliary ganglion in orbit
- Pterygopalatine ganglion in pterygopalatine fossa
- Submandibular ganglion adjacent to submandibular salivary gland
- Otic ganglia just below foramen ovale
Describe ciliary ganglion
Parasympathetic fibres arise from oculomotor nerve
Describe pterygopalatine ganglion
Parasympathetic fibres arise from facial nerve
Describe submandibular ganglion
Parasympathetic fibres arise from facial nerve
Describe otic ganglia
Parasympathetic fibres arise from glossopharangeal nerve
Ciliary ganglion location?
Orbit
Pterygopalatine ganglion location
Pterygopalatine fossa
Submandibular ganglion location
Adjacent to submandibular salivary gland
Otic ganglion location
Just below foramen ovale
Ganglia receiving fibres from the vagus are in the thorax and abdomen.
True
Parasympathetic fibres are frequently transferred from the cranial nerves of origin to other cranial nerves (hitchhikers) via special connecting branches.
True
Sympathetic fibres are not hitchhikers.
False, they are great hitchhikers, and travel on both blood vessels (usually arteries) and/or branches of cranial nerves (more later).
What is the sympathetic trunk?
It is a chain of axons and ganglia situated along the sides of the vertebral bodies. It extends from cranial base to coccyx. In the neck, it is posterior to carotid sheath and anterior to vertebral transverse processes.
Sympathetic nerves arise from neurons in the?
Thoracic and upper lumbar spinal chord.
Preganglionic fibres of sympathetic nerves leave the spinal cord via ?
Mixed spinal nerves through gaps between the vertebrae called intervertebral foramen.
Define ‘mixed spinal nerves’
These are mixed because they also carry motor fibres leaving the spinal cord and sensory fibres passing into the spinal cord.
Mixed spinal nerves are connected to the sympathetic trunk in?
Thorax and upper lumbar regions via fine communicating branches, white rami.
White rami transmits ?
Preganglionic sympathetic fibres to the sympathetic trunk.
Where do preganglionic fibres synapse?
The preganglionic fibres synapse on neurons in the sympathetic ganglia somewhere in the sympathetic trunk, either adjacent to their point of exit from the spinal cord or at some other more distant ganglion.
Define post-ganglionic fibres
Axons derived from neurons in the sympathetic ganglia.