Spinal Cord, Meninges, and Ventricles Flashcards
Peripheral Nervous System
The parts of the nervous system outside of the brain and spinal cord:
- cranial nerves
- spinal nerves
- Autonomic Nervous System: sympathetic and parasympathetic
Somatic Nervous System
Voluntary control; sensory and motor nerves innervate the muscles and skin
Autonomic Nervous System
Involuntary control; sensory and motor nerves innervate visceral organs and glands
Provides neural control of smooth muscle, cardiac muscle, glandular secretory cells or a combination of these;
Cranial nerves, medulla (involuntary fxs), hypothalamus (autonomic function, hormone) receive info from ANS
Sympathetic System
Part of the ANS: energy expenditure via involuntary arousal of glands/organs; flight or fight response
Parasympathetic System
Part of the ANS: energy conservation via calming aroused glands/organs; restoration of homeostasis
Spinal Cord Anatomy
Origin = Foramen Magnum
Termination = around Vetebra L1
Divided into five sections:
cervical (n = 8)
thoracic (n = 12)
lumbar (n= 5)
sacral ( n = 5)
coccygeal (n = 1)
31 sections of vertebrae and 31 pairs of spinal nerves (one each side)
Spinal Cord Info
Thoracic and lumbar regions of SC thicker and bigger than higher or lower areas; all sections have same orientation points:
- Two ventral horns/two dorsal horns
- Ventral root/dorsal root
Gray/white matter reverse of brain; white ext, gray int
CSF flows through central canal; Spinal cord contained in vertebral canal
S input collected somewhere in the body and transferred to the brain /S up, M down/
impulse travels to spinal cord through dorsal horn; goes straight up thru SC, through thalamus, to processing cortex; Motor impulse sent back down through basal ganglia, SC, thru ventral horn, to muscles
Spinal Nerves
are sensory, motor and mixed orientation
each spinal nerve per hemisphere is connected by 2 roots: Dorsal root collects S inputs/ Ventral root sends M impulses
Roots are sometimes included in the entirity of the nerve, but somewhat separate; two roots per spinal nerve side; one V, one D
spinal nerves enter and exit the vertebrae via Intervertebral foramen; Discs keep pressure off nerves
Upper Motor Neurons
Cell bodies in the motor cortex and their descending axonal processes that synapse on the cranial and spinal motor neurons
Lower Motor Neurons
Motor neurons of cranial nerves and spinal cord which send their axonal processes to the skeletal muscle loss of these neurons leads to weakness, twitching (fasciculation) and atrophy of muscles
UMN vs LMN Injury
Damage to horns, roots of nerves – LMN; Damage within tract of SP – UMN
LMN damage is always a ventral issue; Descending tracts are always motor tracts
Once impulse leaves spinal tracts and reaches the ventral horn of the appropriate spinal nerve, it chxs from UMN to LMN
Examples: damage to the dorsal horn of the vestibulospinal tract will signify a LMN damage – False, bc dorsal is S only
Lesion in midbrain – UMN; maxillary branch of the trigeminal nerve – LMN
Relex Arc
Motor response initiated at spinal level; reflexive response – pain, hot –
Once impulse reaches dorsal horn will jump to interneuron – interneuron will xfer impulse to ventral horn and back out thru the nerve to muscles for movement without transferring impulse up spinal cord to brain
An ex of cooperation btwn CNS and PNS to conserve energy
Damage on SC, cant send appropriate S message; cant initiate response (Hand laying on hot stove – no S input, no input of pain, no M response)
Plexus
Collection of spinal nerves that serve a specific fx cervical plexus:
nerves C1 to C5* - diaphragm, muscles of shoulder and neck
brachial plexus: C5 to T1 – triceps, arms, wrists
lumbar plexus: T12 to L4 – lwr abdomen, buttocks, antr thigh
saccral plexus: L4 to S4 -
meninges
The three protective membranes that cover the central nervous system; cerebrum, cerebellum and spinal cord
- Dura mater - thickest, provides most protection; two layers
- Arachnoid mater
- Pia mater - closest to the tissues, softest layer
Dura Mater
Cerebral: Adheres to the inner skull; composed of two fused (periosteal-outer and meningeal-inner) layers that split to form sinuses that carry blood from veins and absorb CSF
Two potential spaces only present in pathologies; both sites of vascular hemorrhage
- epidural (betwn dura and bone)
- subdural (betwn dura and archnoid)
Spinal: Composed only of meningeal layer; seperates from vertebrae by epidural space
Dural Extensions
supportive tents of connective tissues that helps to keep the cerebrum and cerebellum supported and stable, especially during severe head movements (concussions, car accidents, etc); can tear easily
Falx cerebri - largest ext; sickle-shaped; separates the cerebrum hemis
Tentorium cerebelli - covers cerebellum; attaches to temporal bone and falx cerebri
Falx cerebelli - smalles ext; triangular; separates the cerebullum hemis
Arachnoid Mater
Cerebral: thin, non-vascular membrane that surrounds the sulci and folds of the brain bridges the area between dura mater and pia mater; has distinctive structures:
- Arachnoid mater; separated from dura by subdural space
- Arachnoid traebeculae; “stalks” that fill space btwn pia and arachnoid (subarachnoid space)
- Subarachnoid space; filled with CSF; Arachnoid granulations drain old CSF into vascular system
Spinal: subarachnoid space filled with CSF as it surrounds the spinal cord
Pia Mater
Cerebral: “Gentle mother”; thin transparent, collagenous membrane; closely attached to the surface of the brain, surrounds the perivascular space
interwoven with a network of arteries/veins; helps maintain and support blood vessels so that brain receives appropriate nutrients (crucial role)
the arachonoid and pia together termed leptomeninges
Spinal: tightly surrounds the spinal cord; the dorsal/ventral roots of spinal nerves will pierce the pia mater to make contact with spinal cord
