Practical 2 Flashcards
What is the peripheral nervous system?
The peripheral nervous system is composed of all the nerves outside of the brain and spinal cord (cranial & spinal).
What are the divisions of the PNS?
Sensory (Afferent) - Transmits sensory information to the CNS
Motor (Efferent) - Transmits motor information from the CNS to cells
Somatic - Voluntary
Autonomic - Involuntary
Sympathetic - Fight or flight
Parasympathetic - Rest and digest
What are the cranial nerves?
There are 12 cranial nerves that emerge in pairs from the brain and brainstem. They are numbered using Roman numerals and can be referred to by number or name.
I (olfactory nerve): sensory - smell
II (optic nerve): sensory – vision
III (oculomotor nerve): motor – movement of the eye
IV (trochlear nerve): motor – movement of the eye
V (trigeminal nerve): sensory – forehead, eye, upper jaw, lower jaw; motor – muscles of mastication
VI (abducens nerve): motor – movement of the eye
VII (facial nerve): sensory - taste for anterior 2/3 of tongue; motor - muscles of facial expression, parasympathetic innervation of tear and salivary glands
VIII (vestibulocochlear nerve): sensory – equilibrium and hearing
IX (glossopharyngal nerve): sensory – innervation of the pharynx, taste from posterior 1/3 of tongue; motor – pharynx muscles, parasympathetic innervation of salivary glands
X (vagus nerve): sensory - innervation of the larynx; motor - pharynx and larynx muscles, parasympathetic innervation of the thoracic and abdominal organs
XI (accessory nerve): motor – trapezius and sternocleidomastoid muscles
XII (hypoglossal nerve): motor – muscles of the tongue
What are the spinal nerves?
Spinal nerves are named as such because they emerge from the spinal cord. There are 31 pairs of spinal nerves that carry information through the PNS. Spinal nerves are formed by the union of the posterior (sensory) and anterior (motor) roots of the spinal cord.
Spinal nerves are identified based on a letter and number. The letter refers to the region of the spinal cord, while the number refers to the level.
In the cervical region, spinal nerves emerge superior to the corresponding vertebrae. Spinal nerve C8 is the exception, emerging between C7 and T1. Below the neck, all spinal nerves emerge inferior to its corresponding vertebra.
What are nerve plexuses?
When spinal nerves exit the vertebral column, fibres from the anterior roots come together and re-distribute into new networks of plexus is that innervate muscles of the limb. Each plexus contains fibres from a combination of spinal nerves with functional importance in case of injury, because multiple spinal nerves in plexuses ensure innervation to the muscle. The main spinal nerve plexuses corresponds to the enlargement of the spinal cord. The cervical and brachial plexus is correspond to the cervical enlargement, while the lumbar and sacral plexus is correspond to the lumbosacral enlargement.
What is the autonomic nervous system?
The autonomic nervous system is known as the visceral motor system and is responsible for transmitting involuntary signals from the CNS to smooth muscles, cardiac muscles, and glands.
What is the organization of the autonomic nervous system?
The autonomic nervous system is a two neuron pathway between the CNS and any target organ.
Preganglionic fibers: has its cell body within the CNS and its axon entering into the PNS and travelling to the autonomic ganglion.
Autonomic ganglion: where the preganglionic and postganglionic neurons meet and communicate in the PNS.
Postganglionic neuron: entirely in the PNS with its cell body in the autonomic ganglion and its axon travelling to the target organ.
What are the differences between the sympathetic and parasympathetic nervous systems?
Sympathetic: spinal cord segment T1 to L2 (Thoracolumbar division), fight or flight response, and widely distributed affect to many parts of the body.
Parasympathetic: brainstem and spinal cord segment S2 to S4 (Craniosacral division), rest and digest response, limited distribution to target organs with localized effects.
Describe the sympathetic pathway.
1- Sympathetic preganglionic axons leave the lateral horn of the spinal cord with somatic motor axons to form the anterior route.
2- Preganglionic axons passed through the spinal nerve to the sympathetic trunk, a structure lateral to the spinal cord on either side. The sympathetic trunk provides a pathway for the sympathetic fibres to travel through the body both superiorly and inferiorly.
3- Preganglionic neurons synapse with the postganglionic neurons in the ganglia.
4- Postganglionic axons leave the sympathetic trunk to enter the spinal nerve and extend to the effect or tissue/organ at approximately that vertebral level.
Describe the parasympathetic pathway.
1- Preganglionic neurons leave the brain or spinal cord at the level of the sacrum.
2- Preganglionic neurons meet postganglionic neurons and ganglia close to viscera.
3- Post ganglionic neurons travel to effector organs (CNIII/VII/IX - head, CNX - thorax to descending colon, S2/3/4 - terminal gut and pelvic viscera)
Discuss vision.
Vision requires special visual receptors called photoreceptors located at the back of the eye.
What are the accessory structures of the eyeball?
Lacrimal gland: produces tears to keep the cornea and outside surface of the eyeball moist and clean. The tear drainage system is also very important as part of the lacrimal apparatus.
Eyelid: upper eyelid contains the le at or palpebrae superioris muscle and orbicularis oculi muscle to control the opening and closing of the eyelid.
Extrinsic eye muscles: 6 extrinsic eye muscles allow you to move your eyes to increase range of motion.
Extraocular eye muscles: located outside of the eyeball and named based on location.
What are the general features of the eye?
The eye is a globe structure with the majority of it situated within the skull. It is a complex organ with many features and layers.
What are the cavities of the eye?
There are two fluid filled cavities that are delineated by the lens.
Anterior cavity: composed of the anterior and posterior chambers that are filled with aqueous humour (watery)
Lens: separates the interior cavity and the posterior cavity.
Posterior cavity: compartment filled with vitreous humour (gelatinous)
What are the layers of the eye?
The eye is composed of three layers, or tunics.
Deep layer - sensory (retina): The innermost layer of the eye
-Neural layer: has photo receptors that are light sensitive cells which send signals through smaller nerves to the axons of ganglion cells to form CNII
-Optic disc: area were smaller nerve cell axons converge. It is the location we see you when we look into the eye.
-Optic nerve: CN II
-Macula: central area of the retina with a depression, the fovea, where fine detail division occurs.
Middle layer - vascular: middle layer of the eye.
-Chorid: Contains blood vessels that supply the eye with oxygen and nourishment
-Ciliary Body: produces aqueous humour and contains the ciliary muscles which control the shape of the lens
-Iris: contains the sphincter and dilator muscles that control the narrowing and widening of the people while also containing pigment that gives the eye its color.
Outer layer – fibrous: outermost layer of the eye with two portions that or continuous with one another
-Sclera: internal aspect of the fibrous tunic that forms the white portion of the eye with a layer of dense connective tissue acting as a point of attachment for extrinsic eye muscles.
-Cornea: external aspect of the fibrous tunic that is transparent to enable light transmission.
Discuss the flow of aqueous humor.
Aqueous humour is produced by ciliary processes in the posterior chamber then sent through the pupil into anterior chambers to exit at the anterior chamber angle through trabecular meshwork into Schlemm’s canal and ultimately into episcleral venous channels that drain into the systemic circulation.
What is responsible for hearing and equilibrium?
The receptors located in the inner ear are responsible for hearing and equilibrium, one’s unconscious sense of balance and position in space.
Discuss the structure of the ear.
External ear: The structure of the ear that you can touch. Sound waves from the external environment travel through the external auditory canal to reach the tympanic membrane, causing it to vibrate. The tympanic membrane marks the boundary between the external and middle ear. Ceruminous glands are microscopic glands that are present in the external auditory canal as glands that secrete earwax.
Middle ear: Located within the temporal bone, spanning from the tympanic membrane to the oval window. Sound waves involved with hearing are transmitted through the middle ear.
-Tympanic cavity: chamber in the temporal bone
-Ossicles: small bones in the middle ear That transmit sound waves to the receptors in the inner ear with muscles that dampen loud noises. The malleus is the most lateral ossicle, The incus sits between the malleus and the stapes, and the stapes is the smallest bone that sits in the oval window (1/3 mass)
-Round and oval windows: areas at which the middle ear connects to the inner ear
-Eustachian tube: connects the middle ear to the nasopharynx
Inner ear: located within the temporal bone housing the receptor is responsible for hearing and equilibrium.
-Vestibular apparatus: contains receptors for equilibrium. Semicircular canals detect rotational movement, well utricle and saccule are responsible for detecting positional movement.
-Cochlea: contains receptors for hearing. A cross-section of cochlea reveals the structure has three ducts: the vestibular, tympanic, and cochlear. The organ of Corti is made up of specialized cochlear hair cells that rest on the basilar membrane to detect sound waves and fire an impulse to the brain via CNVIII for interpretation.
Labyrinth: both the cochlea and vestibular apparatus are structured as channels in the bone, called labyrinths. Both labyrinths are filled with fluid that allow us to hear or become aware of and monitor the position of her head. The membraneous labyrinth is within the boney labyrinth, filled with endolymph. Boney labyrinth is filled with perilymph.
What is the endocrine system?
The endocrine system is a system of glands that secrete hormones into the bloodstream to create an effect. It impacts all the systems of the body.
What are the different types of glands?
Endocrine: cells secrete hormones directly into the interstitial fluid surrounding the secretory cells. The hormones are then picked up by blood capillaries.
Exocrine: glands that secrete cell products into a duct system.
Discuss the pituitary gland.
Pituitary gland is the master gland because it releases hormones that control all other endocrine glands. It is located inferior to the hypothalamus, sitting on a concavity of the sphenoid bone in the middle of the skull. The physical contact between the hypothalamus and the pituitary allows for communication between the nervous and endocrine systems.
Anterior lobe (Adenohypophesis): composed of glandular secretory cells that produce and release 7 stimulating hormones.
-TSH: causes thyroid gland to release thyroid hormones
-PRL: induces mammary glands of the breast to produce milk
-ACTH: causes adrenal glands to release their hormones
-GH: stimulates growth in all cells
-FSH/LH: act on the gonads to stimulate secretion of estrogen and progesterone, and maturation of oocytes in the ovaries. They also stimulates secretion of testosterone and sperm production in the testes.
-MSH: stimulates melanocytes in the skin to produce pigment
Posterior lobe (Neurohypophesis): made up of nervous tissue to release two hormones produced in the hypothalamus.
-ADH: promotes reabsorption of water at the kidneys
-Oxytocin: promotes uterine contractions during childbirth and plays a role in breast-feeding
What is the histology of the pituitary gland?
Anterior: made of granular acini that are arranged in small groups surrounded by connective tissue. Stains darker.
Posterior: composed of nervous and connective tissue without acini. Stains lighter.
