Intro To The Nervous System Flashcards
Functions of the nervous system
Sensation, integration, action SIA
Sensation
Constant monitoring of internal and external environment by receptors that respond to appropriate stimuli
Integration
Interpretation and processing of sensory information and decision to act or not
Action
Activation or inhibition of effectors
Divisions of the nervous system
CNS - brain and spinal cord derived from neural tube,where integration and cognition occur
PNS-cranial and spinal nerves, transmit electrical impulses (action potentials) Afferent signals-from receptors to CNS (sensory) Efferent signals-from CNS to effectors (motor)
Neuron types
Bipolar, pseudo-unipolar,multipolar
Bipolar neuron
One axon, one dendrite
Special sensory
Pseudo-unipolar neuron
Sensory neurons
Single axon (one end in PNS, other in CNS)
PNS-somatic and visceral sensory
Multipolar neurons
Motor neurons
Single axon, many dendrites
Common in CNS and brain
Nervous system connective tissues
- Endoneurium: covers a single axon (nerve fiber)and its myelin sheath
- Perineuriumi covers a fascicles composed of several axons
- Epineurium:covers multiple fascicles, fatty tissue,and vasculature; forms an anatomical nerve
EPE
Nerve cell bodies
Typically clustered together
Nucleus: group of nerve cell bodies in the CNS
Ganglion:group of nerve cell bodies in the PNS
Nelly can’t get past
Collection of axons (nerve fibers)
- Tract= collection/bundle of axons in the CNS often connecting nuclei (neighboring or distant)
- Nerves= collection/bundle of axons in the PNS
- E.g. Maxillary nerve or facial nerve
- other terms: Ramus, root, trunk, division, cord
GSA
General Somatic Afferent
Somatosensory
Touch, temperature, pain,and proprioception from the somatic/conscious body
GVA
General Visceral afferent
Viscerosensory
Pain, chemo-, baro-,mechano-,sensation from the visceral/internal organs
SSA
Special somatic Afferent
Vision, hearing, balance
SVA
Special Visceral Afferent
Taste and smell
GSE
General Somatic Efferent
Somatomotor
To skeletal muscle: carried by cranial nerves Ill, IV, VI, XIs (11 spinal segment),XII, and Spinal nerves
3, 4, 6, 11, 12
GVE
General Visceral Efferent
Visceromotor
To smooth and cardiac muscles: carried by autonomic nerves (sympathetic and parasympathetic)
SVE
Special Visceral Efferent
Branchiomotor
To skeletal muscles derived from the branchial arches; carried by cranial nerves V,VII,IX,X,XIc (11 cranial portion)
5, 7, 9, 10, 11
Sensory neurons with axons in PNS
Called first order or primary neurons
Cell bodies in dorsal root ganglia
Sensation types and receptors
- Mechanoreception:fine/discriminative touch (localization), crude touch, pressure,vibration
- Thermoreception:temperature
- Nocioception:pain
- Proprioception:relative position of body parts and joints
- Photoreception: light
- Barosensation:pressure and touch
- Chemoreception:taste and smell, O2/CO2 receptors
Complex sensations
- Peripheral nerves are bundles of neurons and often carry multiple modalities and multiple types of sensation
- Sensory loss can involve multiple pathways (e.g. touch and pain)if the nerve or circulation is compromised
Hypoesthesia
Numbness
Parasthesia
Pins and needles
Tingling, pricking, or burning sensation
Motor (efferent) division
Motor neurons with axons in PNS
- Lower motor neurons
- Cell bodies in CNS (ventral horn motor neurons)
- Somatic (GSE):to skeletal (striated)muscle
- Visceral(GVE):to smooth and cardiac muscle
- visceral motor:autonomic nervous system
- Branchial (SVE): carried only by cranial nerves
Autonomic nervous system
- Visceral motor (GVE)
- Sympathetic-fight or flight
- Parasympathetic-rest and digest
- Regulates involuntary bodily functions
- Presynaptic neuron
- have cell bodies in the CNS
- from CNS to ganglion or directly to target organ
- Post synaptic neuron
- have cell bodies in the ganglion
- from ganglion to effector organ
Difference between sympathetic and parasympathetic nervous systems
Different Actions of Sympathetic and Parasympathetic Nervous System
Meningeal Spaces
Regions of vertebral column
cervical, thoracic, lumbar, sacral, coccygeal
Vertebral foramen
form a longitudinal canal for the passage of the spinal cord
Intervertebral foramen
formed by 2 adjacent vertebrae, allow nerves to exit/enter the spinal cord
Intervertebral discs
(outer/inner)
Outer annulus fibrosis
Inner nucleus pulposis
outside, a falcon is preying
Meninges
- Protect and support the CNS
- Connective tissues:
- dura mater (outer layer)
- endosteal layer: only found inside skull
- meningeal layer: surrounds brain and spinal cord
- continuous with epineurium around spinal cord
- arachnoid mater
- loose, web layer allows flow of cerebral spinal fluid
- pia mater
- inseperable from surface of spinal cord
- dura mater (outer layer)
Spinal cord
Extends from?
Surrounded by?
Ends in?
Anchored by?
- extends from foramen magnum to L1-L2 vertebral level
- surrounded by meninges (meningeal layer of dura mater, arachnoid mater, and pia mater)
- ends in conus medularis
- anchored inferiorly by the filium terminale, a fibrous strand of pia mater
- spinal roots and nerves form lumbar-coccygeal levels of cord continue as the cauda equina (“horse tail” of nerve roots)
Numbering Spinal Nerves
- cervical segments: spinal nerves emerge from the intervertebral foramen above the vertebrae of the same number; C8 nerve emerges below C7 and above T1
- thoracic-coccygeal segments: spinal nerves emerge from the intervertebral foramen below the vertebra of the same number
Cross Section of Spinal Cord
- white matter: nerve tracts=myelinated axons
- gray matter: cell bodies
- dorsal horn: sensory (GSA/GVA) cell bodies
- ventral horn: motor (GSE) cell bodies
- lateral horn
- autonomic (GVE) cell bodies
- T1-L2 (sympathetic) spinal levels
- S2-S4 (parasympathetic) spinal levels
Root
contains either motor or sensory fibers leaving the spinal cord
Spinal nerve
contains all neurons- motor and sensory, epaxial and hypaxial
Ramus
contains neurons going to epaxial or hypaxial regions
dorsal horn + root=
ventral horn + root=
sensory
motor
Dorsal root ganglion
contains cell bodies of sensory neurons
part of the PNS (outside of spinal cord)
found in or near the intervertebral foramen
dorsal ramus=
ventral ramus=
motor + sensory to epaxial region
motor + sensory to hypaxial region
