A&P Class 21
Key points of spinal tracts/pathways (4)
(1) Decussation: most pathways cross from one side of the CNS to the other at some point (2) Relay: pathway consist of a chain of 2-3 neurons (3) Somatotopy: most pathways have precise spatial relations with tract fiber which reflect orderly map of the body (4) Symmetry: all paths are paired
Components of Reflex Arc
(1) Receptor (2) Sensory Neuron (3) Integration Center (4) Motor Neuron (5) Effector
Levels of neural integration in sensory systems
(1) Receptor Level (2) Circuit Level (3) Perceptual Level
Parkinson's Disease:
Degeneration of dopamine-releasing neurons of substantia nigra, basal nuclei deprived of dopamine become overactive, resulting in tremors at rest
White Matter of the Spinal Cord
Exterior, neuron fibers provide communion between spinal cord and brain Contains: Dorsal (posterior) Lateral Ventral (anterior)
Huntington's Disease
Fatal hereditary disorder caused by accumulation of protein huntingtin in brain cells; Leads to degeneration of basal nuclei and cerebral cortex; Usually fatal within 15 years of onset
Gray Matter of the Spinal Cord
Interior, Contains: Dorsal Horns, Ventral Horns, Lateral Horns
Spinal Reflexes
Occur without direct involvement of higher brain center Brain advised of reflex and can have an effect of reflex
Somatosensory System
Receives input from exteroceptors, proprocepos, and interoceptors, relays the information towards the head processing it along the way
Interoceptors
Respond to stimuli arising in internal viscera and blood vessels Sensitive to chemical changes, tissue stretch and temperature changes
Exteroceptors
Respond to stimuli arising outside of body Receptors in skin for touch, pressure, pain and temperature
Proprioceptors
Respond to stretch in skeletal muscles, tendons, joints, ligaments, connective tissue coverings of bones and muscles Inform the brain of one's' movements
Limbic system location
Structures on medial aspects of hemispheres and diencephalon; most output via hypothalamus
Spinal Cord Function
Two way communication Major reflect center - reflexes are initiated and completed at the spinal cord
Somatic Reflexes
activate skeletal muscle
Autonomic Reflexes
active visceral effectors (smooth or cardiac muscles or glands)
grey commissure
bridge of gray that connects masses of grey matter on each side, encloses the central canal
Ventral Root
bundle of motor neurons axons exiting the spinal cord
Dorsal root ganglia
cell bodies of sensory neurons
Nerve
cordline organ of PNS A bundle of myelinated and unmyelinated peripheral axons enclosed by connective tissue Types: mixed, sensory, motor
pia mater
directly attached to the brain, follows every convolution contains tiny blood vessels which feed the brain
Fornix
fiber tract that links limbic system regions
Spinal Nerves
forms via the fusion of dorsal and ventral roots 31 pairs of spinal nerves All are mixed nerves; Supply all body parts except head and part of neck
Reticular Formation
has axonal connections with hypothalamus, thalamus, cerebral cortex, cerebellum; sends impulses to cerebral cortex to keep it alert/conscious; filters out repetitive or weak stimuli
Blood Brain barrier function
helps maintain stable environment for brain, selectively permeable (denies metabolic waste, drugs, tonixs) (allows fat-soluble substances)
Nerve Fiber Regeneration
if the soma (cell body) of the damaged nerve is intact, the peripheral axon may regenerate in PNS; does not occur in CNS
Limbic System function
makes us consciously aware of emotion richness in our lives
Arachnoid mater
middle later, subarachnoid space contains CSF and th largest blood vessels of the brain
Functional Brain Systems
network of neurons that work together 2 types: limbic system and reticular formation
Periosteal layer
part of dura mater, attaches to inner surface of the skull, found only in the brain
Meningeal layer
part of dura mater,true external layer of the brain, extends into vertebral canal as spinal dura mater
Meninges
protect the brain, contain CSF 3 layers: dura mater, arachnoid mater, pia mater
Spinal Cord Structure
protected by bone, meninges and CSF; one layer of spinal dura mater; doesn't attach to vertebrae, begins at the foramen magnum and ends at L1 or L2 vertebrae
Intrinsic/Inborn Reflex
rapid, involuntary, predicable motor response to stimulus, can be modified by learning and conscious effort
Chemoreceptors
respond to chemicals
Photoreceptors
respond to light energy
Mechanoreceptors
respond to touch, pressure, vibration, and stretch
Learned/Acquired Reflex
result from practice or repetition
Thermoreceptors
sensitive to changes in temperature
Nociceptors
sensitive to pain-causing stimuli
Dorsal Root
sensory input to spinal cord
The Peripheral Nervous System (PNS) contains...
sensory receptors, peripheral nerves, associated ganglia, efferent motor endings
Sensory Receptors
specialized to respond to changes in environment (stimuli), Activation results in graded potentials that trigger nerve impulses
Sensation
the awareness of changes in the internal and external environment; survival depends upon
Perception
the conscious interpretation of those stimuli; survival depends on
Transection (cross sectioning) of spinal cord at any level results in...
total motor and sensory loss in regions inferior to cut
Dura mater
tough, outmost layer, contains 2 layers: periosteal and meningeal layer
Paraplegia
transection between T1 and L1 Paralysis in lower extremities - lower limbs
Quadriplegia
transection in cervical region Paralysis in 4 limbs
Classification of Sensory Receptors
type of stimulus, body location, and structural complexity
