Week 13: Anatomy of the Peripheral nervous system Flashcards
Somatic nervous system
Transmitting sensory information + voluntary movement
Somatic nervous system pairs of nerves
12 cranial, 31 spinal
Cranial nerves
emerge direct from brain, supply skin of face, muscles of face, special sense in head, vision, smell, balance
Spinal nerves regions
Cervical:8, Thoracic:12, Lumbar:5, Sacral:5, coccygeal:1
Where is the most excitable part of an axon?
Near axon Hillock
Resting potential
-70mV
Threshold potential
-55mV
When are action potentials triggered
When membrane potential increases above -55mV
What happens during action potential (to the membrane potential)
Shoots up, the abruptly down
What info goes along unmylenated fibres?
pain from skin, motor fibres controlling BV and heart
What info travels along myelinated fibres?
fine touch from skin, joint positon. motor fibres - skeletal muscle
Pacinian corpuscles
Found in areaas of skin sensitive to touch e.g. fingertips - When deformed, nerve fibre emits sodium and an action potential is triggered
Nociceptors
pain! Found in many places, part in skin. = FREE-nerve endings - chemical, thermla or mechanical changes cause AP
what detects Skin stretch
Corpuscle of Ruffini
What detects Pressure, position and features such as shapes and edges
Corpuscle of Merkle
What is sensitive to light touch
Meissner’s corpuscle
Where does Spinal cord extend to
Space between L1 and L2
Spinal cord functions
Cpndiut of motor info -travelling caudially. Conduit of sensory info - rostrally. Centre for coordinating reflexes.
Gray matter
Ventral, dorsal, lateral horns
Ventral horn
Cell bodies - motor neurons
Dorsal horn
Axons and terminals of somatosensory neurons
Lateral horn
T1-L2/L3 - Cell bodies of sympathetic neurons
White matter
Contains axons of ascending and descending fibre tracts.
Dorsal column tract
A. same side. carry: discriminatory touch, proprioception, pressure and vibration.
Spinothalamic tract
Lateral to ventral horn - nociceptor and temperature. Cross spinal cord - A. on op side
Corticospinal tract
Lateral to dorsal horn. D. carries motor nerons - (skeletal muscles) info from brain. Crosses op side at brainstemish level - terminate in ventral horn
Which tract is located lateral to dorsal horn
Corticospinal tract
Loss of fine touch - where lesion ?
Dorsal column tract
Loss of pressure and vibration - where lesion ?
dorsal column tract
Loss of pain and temperature on op side body - where lesion?
Spinothalamic tract
Loss of voluntary motor control on same side - Where lesion?
Corticospinal tract
