PNS Chapter 13 Flashcards
Meninges in PNS
1) Dura Mater: outermost layer
2) Arachnoid mater: thin and wispy
3) Pia mater: bound tightly to surface.
Pia mater
- Forms the Filum Terminale (anchors spinal cord to coccyx)
- Forms the denticulate ligaments that attache the spinal cord to the dura mater
Epidural space
- Spinal epidural is done between L3 and S1
- Spinal tap or epidural is done to inject medications into the cerebrospinl fluid, particularly for spinal anesthesia or chemotherapy
- Epidural is don to collect cerebrospinal fluid, particularly for spinal when meningitis is suspected.
- Between the bony vertebrae and spinal dura mater; filled with soft padding of fat and a network of veins
Subdural space
- Filled with Serous fluid
- The space appears to be widest in the cervical region
- however, that the spinal subdural space is not a “potential” space at all, but that it occurs as a result of tissue damage which creates a cleft in this area of the meninges
Superior Sagittal Sinus
- CSF is absorbed into the dural venus sinuses via the arachnoid villi.
- dural venus sinuses collect venous blood from the brain and direct it into the internal jugular veins of the neck. It has no valves.
Arachnoid villi
- knoblike projections of the arachnoid mater that protude superiorly through the dura mater into the superior sagittal sinus.
- This villi absorb CSF into the venous blood of the sinus
Receptors classification by Stiumulus type
- Mechanoreceptors
- Thermoreceptors
- Photoreceptors
- Chemoreceptors
- Nociceptors
Mechanoreceptors
Respond to touch, pressure, vibration, stretch, and itch
Thermoreceptors
- Sensitive to changes in temperature (warm and cold)
- Cold receptors: (10 -40 °C); in superficial dermis
- Heat receptors: (32 - 48 °C); in deeper dermis
Photoreceptors
Respond to light energy (e.g retina)
Chemoreceptors
Respond to chemicals (e.g. smell, taste, changes in blood chemistry)
Nociceptors
Sensitive to pain-causing stimuli (pinching, capsaicin, extreme heat or cold)
Propioceptor
A sensory receptor, found chiefly in muscles, tendons, joints, and the inner ear, that detects the motion or position of the body or a limb by responding to stimuli arising within the organism.
Receptors classification by Location
- Exteroceptors
- Interoceptors
- Propioceptors
Exteroceptors
- Respond to stimuli arising outside the body receive external stimuli
- Hearing, vision, smell, taste, touch, pressure, pain, vibration, and temperature
Interoceptors
- Monitors internal environment (VB or viscera)
- not consious except for pain or pressure
Examples of Exteroceptors
- Pacinian Corpuscles (pressure) = dermis
- Meissner Corpuscles (touch) = dermis
- Mekel disks (touch in the epidermis)
- Free nerve endings (pain)
Baroreceptors
- Mechanoreceptors for regulation of visceral function.
- Baroreceptors of digestive tract
- Baroreceptors of bladder wall
- Baroreceptors carotid sinus and aortic sinus
- Baroreceptors of lung
- Baroreceptors of colon
Baroreceptors of Carotid sinus and aortic sinus
- Provide information on Blood Pressure to cardiovascular and respiratory control centers.
3 Main levels of neural integration in the somatosensory system
- RECEPTOR LEVEL = the sensor receptors
- CIRCUIT LEVEL = ascending pathways
- PERCEPTUAL LEVEL = neuronal circuits in the cerebral cortex
Tonic receptors
- do NOT adapt or adapt slowly
- Pain receptors, propioceptors, DON’T ADDAPT. Blood pressure reseptors.
- Slow addaptation = Merkel’s discs, Ruffini’s corpuscles and interoceptors that respond to chemical levels in the blood
Phasic receptors
- Adapt rapidly
- Receptors responding to pressure, touch and smell adapt quickly
Nerve
- A nerve is an enclosed, cable-like bundle of 100s or 1000s peripheral axons.
Endoneurium
Loose connective tissue that encloses axons and their myelin sheaths
Perineurium
Coarse connective tissue that bundles fibers fascicles
Epineurium
tough fibrous sheath around a nerve
reversed
tough fibrous sheath around a nerve
Epineurium
Loose connective tissue that encloses axons and their myelin sheaths
Endoneurium
Coarse connective tissue that bundles fibers fascicles
Perineurium
What is the largest cranial nerve?
Which parts of the body it innervate?
• Nerve V, The Trigeminal nerve,
- The ophthalmic nerve (V1) carries sensory information from the scalp and forehead, the upper eyelid, the conjunctiva and cornea of the eye, the nose.
- The maxillary nerve (V2) carries sensory information from the lower eyelid and cheek, the upper lip, the upper teeth and gums, the nasal mucosa, the palate and roof of the pharynx, the maxillary, ethmoid and sphenoid sinuses.
- The mandibular nerve (V3) carries sensory information from the lower lip, the lower teeth and gums, the chin and jaw, parts of the external ear. The mandibular nerve carries touch/position and pain/temperature sensation from the mouth. It does not carry taste sensation. The motor root of the mandibular nerve innervates the four muscles of mastication.
Importance of Phrenic Nerve.
Name its associated plexus
- The Phrenic Nerve innervates the Diaphragm (sole motor nerve supply)
- Branches from the Cervical Plexus
Spinal nerves in the:
- Cervical region
- Thoracic region
- Lumbar region
- Sacral region
- Coccygeal region
- 8 Cervical (C1 - C8)
- 12 Thoracic (T1 -T12)
- 5 Lumbar (L1 - L5)
- 5 Sacral (S1 - S5)
- 1 Coccygeal (Co1)
What is the largest spinal nerve and its innervations?
- Sciatic nerve in the Sacral plexus
- It supplies the entire lower limb, except the anteromedila thigh. The sciatic supplies nearly the whole of the skin of the leg, the muscles of the back of the thigh, and those of the leg and foot.
- Consis of 2 major branches
- The tibial
- common fibular
Cervical plexus
(most of its branches are cutaneous nerves)
Cervical plexus (C1 to C5)
- Cutaneous branches:
- a. Lesser occipital (C2, C3): posterior head and neck
- b. Greater auricular (C2, C3): ear, parotid gland
- c. Transverse cervical (C2, C3): anterior neck
- d. Supraclavicular (C3-C4): shoulder
- Motor branches:
- a. Ansa cervicalis (C1-C3): Infrahyoid muscles of neck
- b. Segmental and other muscular branches (C1-C5) : deep muscles of neck (scalenes, trapezius, sternocleidomastoid)
- c. Phrenic (C3-C5): Diaphragm
Region that contains part of the system that helps maintain cerebral alertness and regulates skeletal and visceral muscle activity. (location)
Reticular Formation (medulla oblongata, pons, midbrain)
• Reticular Formation (location, function)
- medulla oblongata, pons, midbrain
- Region that contains part of the system that helps maintain cerebral alertness and regulates skeletal and visceral muscle activity
Brachial plexus
Brachial plexus (C5 to T1)
- Muscolocutaneous nerve (C5-C7): biceps brachii, brachialis
- Median nerve (C8, T1, C5-C7): Flexors (carpi radialis), pronator teres, Thenar muscles
- Ulnar nerve (C8, T1): Flexor (carpi ulnaris), hypothenar muscles
- Radial nerve (C5-C8, T1): Triceps brachii, extensors
- Axillary nerve (C5, C6): Deltoid, Teres minor
Lumbar plexus
Lumbar plexus (L1 to L4)
- Femoral nerve (L2-L4): Iliacus, sartorius, rectus femoris, pectineus, vastus (lateralis, medialis, intermedius)
- Obturator nerve (L2-L4): Adductur (magnus, brevis, longus), Gracilis, pectineus, obturator externus
Sacral plexus
Sacral plexus (L4 to S4)
- Sciatic nerve
- a. Tibial nerve (L4-S3): biceps femoris, semitendinosus, adductor magnus, semimembranosus, gastrocnemius, soleus, Flexors
- b. Common fibular nerve (L4-S2): Biceps femoris, tibialis anterior, extensors
- Superior gluteal
- Inferior gluteal
- Posterior femoral cutaneous
- Pudendal (S2-S4) most of skin and muscles of perineum (anus, clitoris, labia, vaginal, penis, scrotum
