Chapter 14 - Spinal Cord and Spinal Nerves Flashcards
Spinal Cord Functions
- Conduction
- Neural Integration
- Locomotion
- Reflexes
Spinal Meninges
- Dura Mater
- Arachnoid Mater
- Pia Mater
Dura Mater
- meninge
- tough, outer layer
- dense collagen fibers
- within epidural space
Arachnoid Mater
- meninge
- middle layer
- subarachnoid space with CSF
- shock absorber & diffusion medium
Pia Mater
- meninge
- delicate, inner layer
- elastic and collagen fibers
Nerve
several axons wrapped by connective tissue
Endoneurium
wraps one axon
Perineurium
wraps a fascicle of axons
Epineurium
wraps entire nerve
Afferent Nerve Fibers
carry sensory signals from receptors to CNS
Efferent Nerve Fibers
carry motor signals from CNS to effectors
Somatic Nerve Fibers
innervate skin, skeletal muscles, bones, and joints
Visceral Nerve Fibers
innervate blood vessels, glands, and viscera
General Nerve Fibers
innervate widespread organs such as muscles, skin, glands, viscera, and blood vessels
Special Nerve Fibers
innervate more localized organs in the head, including the eyes, ears, olfactory and taste receptors, and muscles of chewing, swallowing, and facial expression
How many spinal nerves?
31 pairs
- C1-C8
- T1-T12
- L1-L5
- S1-S5
- Co1
Proximal Branches of Spinal Nerves
- occur as it passes through the intervertebral space
- dorsal root (w/ dorsal root ganglion)
- ventral root
Distal Branches of Spinal Nerves
- posterior ramus (innervates muscles and joints in the region of the spine and skin of the back)
- anterior ramus (innervated the anterior and lateral skin and muscles of the back and gives rise to the nerves of the limbs)
- meningeal branch (reenters vertebral canal and innervates the meninges, vertebrae, and spinal ligaments)
Ganglion
cluster of cell bodies outside the CNS that contains sensory neurons
Plexuses
anterior rami branch and merge repeatedly to give rise to 5 web-like nerve plexuses or peripheral nerves
- Cervical plexus (neck)
- Brachial plexus (shoudler)
- Lumbar plexus (lower back)
- Sacral plexus (below lumbar)
- Coccygeal plexus (lower sacrum and coccyx)
Cervical Plexus
- C1-C5
- innervates:
- muscles of the neck
- diaphragm (**phrenic nerve)
- skin of neck & superior part of chest
Brachial Plexus
- C5-T1 (C4 & T2)
- innervates:
- pectoral girdle
- upper limbs (**ulnar nerve)
Lumbar Plexus
- T12-L4
- Innervates:
- pelvic girdle
- lower limbs
Sacral & Coccygeal Plexuses
- L4-S4
* *sciatic nerve
Properties of a Reflex
- Requires stimulation
- Quick
- Involuntary
- Stereotyped
- Big role in homeostasis
Reflex Arc
Route followed by nerve impulse
- arrival of stimulus & activation of receptor
- sensory neuron activated (to posterior horn of grey)
- information processing in CNS
- motor neuron activated (from anterior horn of grey)
- peripheral effector responds
Visceral (Autonomic) Reflex
- glands, cardiac muscle, smooth muscle
- heart rate, respiration, digestion, urination
- controlled by autonomic nervous system
- sympathetic NS = fight or flight
- parasympathetic NS = rest and digest
Somatic Reflex
- involuntary control of skeletal muscles
- controlled by somatic nervous system
- stretch reflex = pateller reflex
- tendon reflex = skeletal muscle can’t break tendon
- withdrawal (flexor) reflex = pain
- plantar reflex = corticospinal tracts working
Spinal Shock
syndrome of paralysis and absence of reflexes after transection of cord
Neurogenic Shock
dangerous drop in blood pressure due to lack of sympathetic nervous system activity
Paraplegia
paralysis of both lower limbs due to lesions from T1-L1
Quadriplegia
paralysis of all four limbs due to lesions above C5
Hemiplegia
paralysis on one side of the body usually due to stroke or brain lesions
