Gen Physiology Prelims

• General functions of the renal system:

  • Elimination of waste products
  • Controls the plasma volume in the body
  • Maintains acid-base balance
  • Regulates blood pressure through the Renin-Angiotensin-Aldosterone System (RAAS)
• Renin-Angiotensin-Aldosterone System (RAAS) process:

  • Dehydration/excessive bleeding leads to decreased blood volume and blood pressure
  • Activation of juxtaglomerular cells produces Renin
  • Renin acts on Angiotensinogen to form Angiotensin 1
  • Angiotensin 1 is converted to Angiotensin 2 (a potent vasoconstrictor) by ACE
  • Angiotensin 2 stimulates the adrenal cortex to release Aldosterone, maintaining electrolytes and water reabsorption, increasing blood volume, normalizing blood pressure
• The kidneys' anatomy:

  • Bean-shaped organs located retroperitoneally between T12-L3
  • External anatomy includes the renal capsule, adipose tissue, and renal fascia
  • Internal anatomy consists of the renal cortex and renal medulla, which contains renal pyramids
• The nephron is the functional unit of the kidneys responsible for urine formation and consists of structures like the glomerulus, Bowman's capsule, proximal and distal convoluted tubules, and collecting tubules/ducts
• Urine formation stages:

  • Glomerular filtration allows water and small solutes to pass through while preventing proteins, platelets, and blood cells
  • Tubular reabsorption occurs in the PCT, thin and thick ascending/descending loops of Henle, DCT, and collecting tubules, resulting in the formation of diluted urine
• The ureter is 25-30 cm long and composed of smooth muscle, while the urinary bladder is composed of the detrusor muscle for urine storage
• The urethra, the terminal portion of the renal system, varies in length between males (20 cm) and females (2-3 cm), with the external urethra sphincter being voluntary and the internal urethra sphincter involuntary
• Location of Brain stem

  • Cn1 – Telencephalon (not in Brainstem)
  • Cn2 - Diencephalon
  • 3 types of Brainstem – Cn3,4
  • Cn5,6,7,8
  • Cn7,8,9,10,11,12
• Brain stem stroke - Weber


  Medial basal midbrain (Cn3)
• Brain stem stroke - Benedikt


  Tegmentum of the midbrain (Cn3)
• Brain stem stroke - Locked-in


  Bilateral basal pons (all in the pons)
• Brain stem stroke - Millard Gabler


  Lateral pons (Cn6,7)
• Brain stem stroke - Wallenburg

  Lateral Medalla (Cn5) (because of Pain and temperature of facial sensation)
• 3 Sensory Nuclei


  • MB 1. Mesencephalon - Function-(Cn5) Proprioception of face and position sense
  • Pons 2. Main Sensory - Function –(Cn5) Light touch
  • MO 3. Spinal Nucleus - Function –(Cn5) Pain and Temperature
• Exit Points


  • Cribriform plate of Ethmoid - Cn1
  • Optic - Cn2
  • Superior Orbital fossa - Cn3,4,5 V1,6
  • Foremen of Rotundum - Cn5 V2
  • Foremen of Ovalle - Cn5 V3
  • Internal Acoustic Meatus - Cn7,8
  • Jugular foremen - Cn9,10,11
  • Hypoglossal Cortex - Cn12
• General Function


  • Full sensory – CN1,2,8
  • Full motor – CN3,4,6,11,12
  • Both Sensory and Motor or mixed CN5,7,9,10 (1975)
  • Vagal system
  • Cough reflex
  • Vomiting reflex
  • Salivary-taste reflex
  • Carotid sinus reflex- increase of pressure it will decrease the heart rate
  • Gag reflex (afferent Cn 9, Efferent Cn 10)
• Trivia's


  • Largest CN – 5
  • Longest CN -10
  • Shortest CN - 1
  • Thickest myelin in Cn - 2
  • Multiple Sclerosis – Cn2
  • Marcus Gunn Pupil – Cn2
  • Weber syndrome – Cn3
  • Benedikt syndrome –Cn3
  • Diabetes Mellitus – Cn3,6
  • Myasthenia Gravis – Cn3,4,6
  • Traumatic Brain Injury – Cn3,7,1
  • Parkinson’s disease –Cn3,7,9
  • Bell’s Palsy – Cn7
  • Moebius –Cn7
  • Leprosy- Cn7
  • Millard Gabler Cn6,7
  • Sjogren – Cn7,9
• Cranial Nerve 1 “OLFACTORY”


  For sensory, Smell, Lesion: Anosmia, Most common Contused because of the location, CSF RHINORRHEA (nose) secondary to BASILAR skull fracture, CSF SIALORRHEA (mouth) - drooling, CSF OTORRHEA (ear)
• Cranial Nerve 2 “OPTIC”

  For sensory, Vision, Lesion: Anopsia, Other conditions: Myopia – near sightedness (impaired far vision), Hyperopia – far sightedness (impaired near vision), Presbyopia – old sightedness (blurred vision), Nyctalopia – night blindedness (deficient of vit A) “retinol”, Amaurosis Fugax – Monocular blindness (one eye is blind), Tested by Snellen's chart (central visual acuity) and Confrontation test (peripheral visual acuity), Other tests: ISHIHARA - color vision testing, Tonometry intralocular pressure, Retinoscopy - to measure refraction errors
• Cranial Nerve 3 “OCULOMOTOR”

  For motor, Edinger Westphal Nerve, PERRLA – Pupil Equally Round Reactive to Light Accommodation, Ptosis – drooping of the eyelid (Levator palpebrae superioris muscle), Damage causes Mydriasis (dilated pupil), Anisocoria – unequal size of the pupil, Pupillary Light Reflex, Direct Light reflex (one is constricted) and Consensual effect (both constricted), Formula: EOM3, LR6, SO4, SUPERIOR RECTUS - 3, LATERAL RECTUS - 6, INFERIOR RECTUS - 3, MEDIAL RECTUS - 3, INFERIOR OBLIQUE – 3, SUPERIOR OBLIQUE - 4, Diplopia – double vision (eye patch), vertical – CN4, horizontal – CN6, Nystagmus
• Cranial Nerve 4 “trochlear”


  For motor, Superior Oblique
• Cranial Nerve 5 “Trigeminal”

  For sensory and motor, Largest cranial nerve, “Gasserian ganglion”, “Semilunar ganglion”, “MOTOR” - Muscles of Mastication (TIME), Temporalis muscle, Internal (MEDIAL) pterygoid muscle closes the mouth, Masseter muscle, External (LATERAL) pterygoid muscle – opens the mouth, “SENSORY” Facial sensation, CN5 v1 – Ophthalmic (corneal reflex – blink) (Sneeze reflex – 5 v1 is afferent, 9 and 10 is efferent), CN5 v2 – Maxilla, CN5 v3 – Mandible (also motor), Eye Opening – CN3, Eye Closing – CN7
• Cranial Nerve 6 “Abducens”

  For motor, Lateral Rectus
• Cranial Nerve 7 “Facial”

  For sensory and motor, Muscle of Expression, Frowning – Corrugator Supercilii, Surprise – Occipitofrontalis, Smile – Major Zygomaticus, Kissing – Orbicularis Orris, Sucking – Buccinator, Sneezing – Levator Anguli Oris, Blinking/winking – Orbicularis oculi, Egad – platysma
• Muscle movements controlled by Cranial Nerve 7 "Facial"

  1. Frowning – Corrugator Supercilii

  2. Surprise – Occipitofrontalis

  3. Smile – Major Zygomaticus

  4. Kissing – Orbicularis Orris

  5. Sucking – Buccinator

  6. Sneezing – Levator Anguli Oris

  7. Blinking/winking – Orbicularis oculi

  8. Egad – platysma
• Cranial Nerve 7 "Facial"


  • For sensory and motor functions
  • Responsible for muscle movements of expression
  • Sensory function includes taste in the anterior 2/3 of the tongue
  • General sensation in the posterior 1/3
• Cranial Nerve 8 "Vestibulocochlear"

  1. Vestibular part for balance, Cochlear part for hearing

  2. Special tests: Weber test for lateralization of hearing loss, Rinne test for air conduction vs bone conduction
• Cranial Nerve 8 "Vestibulocochlear"


  • For sensory functions
  • Vestibular part related to balance, Cochlear part related to hearing
  • Cortical deafness and Heschl's Gyrus mentioned
• Cranial Nerve 9 "Glossopharyngeal Nerve"

  1. Motor function for Stylopharyngeus Muscle

  2. Sensory function for taste and general sensation in the posterior 1/3 of the tongue

  3. Autonomic function for monitoring the Parotid Gland
• Cranial Nerve 9 "Glossopharyngeal Nerve"


  • For sensory and motor functions
  • Innervates Stylopharyngeus Muscle
  • Sensory function includes taste and general sensation in the posterior 1/3 of the tongue
  • Autonomic function for the Parotid Gland
• Cranial Nerve 10 "Vagus"

  1. Motor function for pharynx and larynx muscles

  2. Sensory function for skin of pinna of external ear and sensation to the pharynx, larynx, and epiglottis

  3. Autonomic function for 75% of Parasympathetic innervation
• Cranial Nerve 10 "Vagus"

  • For sensory and motor functions
  • Longest Cranial nerve
  • Innervates muscles of the pharynx and larynx
  • Sensory function includes skin of pinna of external ear and sensation to the pharynx, larynx, and epiglottis
  • Autonomic function for 75% of Parasympathetic innervation
• Cranial Nerve 11 "Spinal Accessory"

  1. Cranial part for Vagal system, Spinal part for sternocleidomastoid and trapezius muscles

  2. Related to lateral winging of the Scapula and Radical neck dissection
• Cranial Nerve 11 "Spinal Accessory"


  • For motor functions
  • Consists of cranial and spinal parts
  • Innervates sternocleidomastoid and trapezius muscles
  • Passes through foramen Magnum
  • Related to lateral winging of the Scapula and Radical neck dissection
• Cranial Nerve 12 "Hypoglossal Nerve"

  1. For tongue movement

  2. Related to Dysarthria
• Cranial Nerve 12 "Hypoglossal Nerve"


  • For motor functions
  • Controls tongue movement
  • Related to Dysarthria