N261 Chapter 16: Pathways and Higher-Order Functions

homunculus

a maplike representation of regions of the body in the brain

there is a continuous flow of information between the brain, spinal cord, and peripheral nerves

many subtle forms of interaction, feedback, and regulation link higher centers with the various components of the brain stem

nerve pathways, called tracts, connect

the CNS and PNS

sensory pathways:

-posterior column

-spinothalamic pathway

-spinocerebellar pathway

sensory pathways usually contain three neurons:

-1st= to the CNS

-2nd= interneuron in either the spinal cord or brainstem

-3rd= carries info from thalamus to cerebral cortex

posterior column pathway

-fasciculus gracilis

-fasciculus cuneatus

spinocerebellar pathway

-posterior spinocerebellar tract

-anterior spinocerebellar tract

fasciculus gracilis

proprioception, fine touch, pressure, and vibration from the inferior half of the body

fasciculus cuneatus

Proprioception, fine touch, pressure and vibration from the SUPERIOR half of the body

lateral spinothalamtic tracts

pain and temperature sensations

anterior spinothalamic tracts

crude touch and pressure sensations

spinocerebellar pathway

-posterior and anterior tracts

-NO THIRD ORDER NEURON

-proprioception

motor pathways

-corticospinal pathway

-medial and lateral pathways

motor pathways usually contain two neurons:

SNS:

-upper motor neuron= within the CNS

-lower motor neuron= from CNS to effector

ANS:

-preganglioninc neuron

-ganglionic neuron

spastic paralysis

upper motor neuron damage

flaccid paralysis

lower motor neuron damage

characteristics of higher-order functions:

-performed by the cerebral cortex

-involve complex interconnections and communication between areas within the cerebral cortex and other areas of the brain

-conscious and unconscious information processing

-functions are subject to modification and adjustment over time (learning)

cortical areas

act as centers for complex sensory stimuli and motor responses

general interpretive area (Wernicke's area)

-receives information from all sensory association areas

-only present in one hemisphere (left)

speech center (Broca's area)

regulates patterns of breathing and vocalization

prefrontal cortex

-coordinates information from the secondary and special association areas of the cortex

-performs abstract intellectual functions

Broca's aphasia

inability to produce speech

Wernkicke's aphasia

cannot say what you want to say

memory

-process of accessing stored bits of information acquired through experience

-long-term memories are stored in the cerebral cortex

memory consolidation

conversion from a short-term memory to a long-term memory

-amygdaloid body and the hippocampus (limbic system)

delirium

disorientation, restlessness, confusion, hallucinations, agitation, alternating with other conscious states

dementia

progressive decline in spatial orientation, memory, behavior, and language

confusion

reduced awareness, easily distracted, easily startled by sensory stimuli, alternates between drowsiness and excitability

normal consciousness

aware of self and external environment, well-oriented, responsive

somnolence

extreme drowsiness, but will respond to normal stimuli

chronic vegetative state

conscious but unresponsive, no evidence of cortical function

asleep

can be aroused by normal stimuli

stupor

can be aroused by extreme and or/repeated stimuli

coma

cannot be aroused and does not respond to stimuli

age-related anatomical changes in the nervous system:

-reduction in brain size and weight

-reduction in the number of neurons

-decrease in blood flow to the brain

-changes in synaptic organization of the brain

-intracellular and extracellular changes in CNS neurons