Module 6 Flashcards
Peripheral Nervous System
Nerves outside of the brain and spinal cord
Divisions of the Peripheral Nervous System
Sensory (Afferent) and Motor (Efferent)
What Does the Sensory (Afferent) Division do?
Transmits sensory information from the periphery nervous system to the central nervous system
What does the Motor (Efferent) Division do?
Transmits motor commands from the central nervous system to the periphery
Further Divisions of the Motor Division
Somatic and Autonomic
Somatic Division
Voluntary motor control of skeletal muscles
Autonomic Division
Involuntary motor control of smooth and cardiac muscle. Includes the sympathetic and parasympathetic system
Sympathetic
Flight or fight response
Parasympathetic
Rest and digest response
Cranial Nerves
Emerge in pairs from the brain and brain stem. There are 12 cranial nerves, Some carry only sensory information, only motor or both
CN I Name
Olfactory
CN I Function
Sensory only - Smell
CN II Name
Optic
CN II Function
Sensory only - Vision
CN III Name
Oculomotor
CN III Function
Motor only - movement of the eyes
CN IV Name
Trochlear
CN IV Function
Motor only - Movement of the eye
CN V Name
Trigeminal
CN V Function
Sensory - forehead, eye, upper jaw, lower jaw
Motor - muscles of mastication
CN VI Name
Abducens
CN VI Funciton
Motor only - movement of the eye
CN VII Name
Facial
CN VII Function
Sensory - taste for anterior 2/3 of tongue
Motor - Muscles of facial expression, parasympathetic innervation of tear and salivary glands
CN VIII Name
Vestibulocochlear
CN VIII Functiotion
Sensory only - Equilibrium and hearing
CN IX Name
Glossopharyngeal
CN IX Function
Sensory - sensory innervation of the pharynx, taste from posterior 1/3 tongue
Motor - pharynx muscles, parasympathetic innervation of salivary glands
CN X Name
Vagus
CN X Function
Sensory - innervation of the larynx
Motor - pharynx and larynx muscles, parasympathetic innervation of the thoracic and abdominal organs
CN XI Name
Accessory
CN XI Function
Motor only - Trapezius and sternocleidomastoid muscles
CN XII Name
Hypoglossal
CN XII Function
Motor only - Muscles of the tongue
What are Spinal Nerves
Nerves that emerge from the spinal cord
How Many Pairs of Spinal Nerves are There
31 pairs that carry info through the PNS
How is a Spinal Nerve Formed
Formed by the union of the posterior (sensory) and anterior (motor) roots of the spinal cord
Classifying Spinal Nerves
Can be identified based on a letter and number. Letter refers to the region, number refers to the level
Where do Cervical Spinal Nerves Emerge
Superior to their corresponding vertebrae - except for C8 emerging between C7 and T1
Where do Spinal nerves Below the Beck Emerge
Inferior to their corresponding vertebra
Nerve Plexuses Process
Once the spinal nerves leave the vertebral column, fibres from the anterior roots (motor) come together and then redistribute into new networks of nerves (plexuses) that innervate muscles of the limb
What are Nerve Plexus What Do They Contain
Each plexus contains fibres from a combination of spinal nerves
What Do the Spinal Nerve Plexuses Correspond With
The main spinal nerve plexuses in the body correspond to the enlargements of the spinal cord.
What Do the Cervical and Brachial Plexuses Correspond With
The cervical and brachial plexuses correspond to the cervical enlargement
What do the Lumbar and Sacral Plexuses Correspond With
the lumbar and sacral plexuses correspond to the lumbosacral enlargement
Autonomic Nervous System
Responsible for transmitting involuntary signals from the CNS to smooth muscle, cardiac muscle and glands
Organization of the Autonomic Nervous System
Two neuron pathway, between the CNS and any target organ, there are two neurons
Preganglionic Neuron
Cell body within the CNS, the axon enters into the PNS and travels to the autonomic ganglion
Autonomic Ganglion
Where the preganglionic and postganglionic neurons meet and communicate, located in the PNS
Postganglionic Neuron
Entirely in the PNS. The cell body is in the autonomic ganglion while its axon travels to the target organ
Sympathetic Nervous System Origin
Spinal cord segment T1-L2 (Thoracolumbar Division)
Sympathetic Nervous System Response
Fight or Flight
Parasympathetic Nervous System Origin
Brainstem and spinal cord segment S2-S4 (Craniosacral division)
Parasympathetic Nervous System Response
Rest and Digest
Sympathetic Pathways - (1) Lateral Horn of Spinal Cord
Sympathetic preganglionic axons leave the lateral horn of the spinal cord, with somatic motor axons to form the anterior root
Sympathetic Pathways - (2) Sympathetic Trunk
Preganglionic axons pass through the spinal nerve to the sympathetic trunk. PT provides a pathway for the sympathetic fibres to travel through the body superiorly and inferiorly
Sympathetic Pathways - (3) Ganglion
Preganglionic neurons synapse with postganglionic neurons in the ganglia
Sympathetic Pathways - (4) Effector Organ
Postganglionic axons leave the sympathetic trunk to enter the spinal nerve and extend to the effector tissue/organ at approximately that vertebral level
Parasympathetic Pathways
- Preganglionic neurons leave the brain or spinal cord at sacrum level
- Preganglionic neurons meet postganglionic neurons in ganglia close to viscera
- Postganglionic neurons travel to effector organs
What do Postganglionic Neurons from CN III, VII and IX Supply
The head
What do Postganglionic Neurons from CN X Supply
The thorax to the descending colon
What do Preganglionic Neurons from S 2, 3, 4 Supply
The terminal gut and pelvic viscera (bladder and reproductive organ)
What Does Vision Require
Special visual receptors called photoreceptors located at the back of the eye
Accessory Structures of the Eye
Important structures outside of the eyeball that protect and move the eyeball
Accessory Structures - Lacrimal Gland
Produces tears, which keep the cornea or the outside surface pf the eyeball moist and clear
Accessory Structures - Eyelid
Upper eyelid contains the levator palpebrae superioris muscle and orbicularis oculi muscle
Accessory Structures - Extrinsic Eye Muscles
Six extrinsic eye muscles that allow you to move your eyes to increase your range of motion, they are named based on their location
Cavities of the Eye
There are two fluid cavities that are delineated by the lens
Anterior Cavity
Composed of the anterior and posterior chambers, filled with aqueous humour
Lens
Separates the anterior cavity of the eye from the posterior
Posterior Cavity
Filled with vitreous humour (gelatinous fluid)
Deep Layer : Sensory Tunic (Retina) - Neural Layer
Outermost part is made up of photoreceptors (rods and cones) which are light sensitive cells. They send signals through smaller nerves to the axons of the ganglion cells exit the posterior aspect of the brain to form CN II
Deep Layer Sensory Tunic (Retina) - Optic Disc
Area where smaller nerve cell axons converge. Location we can see when we look into the eye
Sensory Tunic (Retina) - Optic Nerve (CN II)
just know its part of the sensory tunic ig
Sensory Tunic (Retina) - Macula
The central area of the retina, lateral to the optic disc. The central depression of the macula, the fovea is the area where detailed vision occurs
Middle Layer: Vascular Tunic - Choroid
Contains the blood vessels that supply the eye with oxygen and nourishment
Middle Layer: Vascular Tunic - Ciliary Body
Produces aqueous humor and contains the ciliary muscles which control the shape of the lens
Middle Layer: Vascular Tunic - Iris
Contains the sphincter and dilator muscles which control the narrowing and widening of the pupil. Contains pigments which gives the eye its colour
Outer Layer: Fibrous Tunic - Sclera
The sclera is the internal aspect of the fibrous tunic, located posterior to the lens. The sclera forms the white portion of the eye. It is a layer of dense connective tissue that acts as a point of attachment for the extrinsic eye muscles
Outer Layer: Fibrous Tunic - Cornea
The cornea is the external aspect of the fibrous tunic, located anterior to the lens. The cornea is transparent enabling light transmission
Flow of Aqueous Humor
Produced by the ciliary processes in the posterior chamber. It flows through the pupil into the anterior chamber and exits at the anterior chamber angle through trabecular meshwork into episcleral venous channels which drain into the systemic circulation
External Ear - Soundwaves
Soundwaves from the external environment travel through the external auditory canal to reach the tympanic membrane, causing it to vibrate
Tympanic Membrane
Marks the boundary between the external and middle ear
Ceruminous Glands
Microscopic glands that are present in the external auditory canal. These glands secrete ear wax
External Ear
The structure of the ear you can touch
Middle Ear
Located within the temporal bone, spands from the tympanic membrane to the oval window
Middle Ear - Tympanic Cavity
Chamber in the temporal bone
Middle Ear - Ossicles
Small bones located in the middle ear
Middle Ear - Round and Oval Windows
Area where the middle ear connects to the inner ear
Middle Ear - Eustachian Tube
Connects the middle ear to the nasopharynx
Ossicles
Three small bones located in the middle ear that help transmit sound waves to the receptors in the middle ear
Ossicles - Malleus (Hammer)
Most lateral ossicle that is attached to and behind the tympanic membrane
Ossicles - Incus (Anvil)
Sits between the malleus and stapes
Ossicles - Stapes (Stirrup)
Smallest bone and sits in the oval window
Inner Ear
Located within the temporal bone, houses the receptors responsible for hearing and equilibrium
Inner Ear - Vestibular Apparatus
Contains the receptors for equilibrium
Inner Ear - Cochlea
Contains receptors for hearing
Labyrinth Definition
Both the cochlea and the vestibular apparatus are structured as two channels in the bone, called labyrinths: the membranous and bony labyrinths. The membranous labyrinth is within the bony labyrinth
Labyrinth Function
Both labyrinths are filled with fluids that allow us to hear (cochlea) or become aware of and monitor the position of our head (vestibular apparatus). The membranous labyrinth is filled with endolymph and the bony labyrinth is filled with perilymph
Vestibular Apparatus - Semicircular Canals
Detect rotational movement (changes in the head’s position in space on an angular axis - side to side, up and down)
Vestibular Apparatus - Utricle and Saccule
Responsible for detecting positional movement (changes in the head’s position from one point to another)
Cochlea Ducts
there are three ducts: vestibular, tympanic and cochlear
Organs of Corti
Specialized cochlear hair cells that rest on a basilar membrane. When a membrane is moved by soundwaves, the hair cells fire an impulse sent to the brain via CN VIII for interpretation
