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