The nervous system

Peripheral Nervous System
3 kinds of neurons connect CNS to the body
sensory
motor
interneurons
Motor - CNS to muscles and organs
Sensory - sensory receptors to CNS
Interneurons: Connections Within CNS

Peripheral Nervous System

Somatic System
Nerves to/from spinal cord
control muscle movements
somatosensory inputs
Both Voluntary and reflex movements
Skeletal Reflexes
simplest is spinal reflex arc

Autonomic System
Two divisions:
sympathetic
Parasympatheitic
Control involuntary functions
heartbeat
blood pressure
respiration
perspiration
digestion
Can be influenced by thought and emotion

Sympathetic
“ Fight or flight” response
Release adrenaline and noradrenaline
Increases heart rate and blood pressure
Increases blood flow to skeletal muscles
Inhibits digestive functions

Parasympathetic
“ Rest and digest ” system
Calms body to conserve and maintain energy
Lowers heartbeat, breathing rate, blood pressure

Summary of autonomic differences

Central Nervous System
Brain and Spinal Cord

Left & Right sides are separate
Corpus Callosum : major pathway between hemispheres
Some functions are ‘lateralized’
language on left
math, music on right
Lateralization is never 100%
Brain has 2 Hemispheres

Each hemisphere is
divided into 4 lobes

Sensory Information sent to opposite hemisphere
Principle is Contralateral Organization
Sensory data crosses over in pathways leading to the cortex
Visual Crossover
left visual field to right hemisphere
right field to left
Other senses similar

Contralateral Motor Control
Movements controled by motor area
Right hemisphere controls left side of body
Left hemisphere controls right side
Motor nerves cross sides in spinal cord

Corpus Callosum
Major ( but not only) pathway between sides
Connects comparable structures on each side
Permits data received on one side to be processed in both hemispheres
Aids motor coordination of left and right side

Corpus Callosum
What happens when the corpus callosum is cut?
Sensory inputs are still crossed
Motor outputs are still crossed
Hemispheres can’t exchange data

The ‘Split Brain’ studies
Surgery for epilepsy : cut the corpus callosum
Roger Sperry, 1960’s
Special apparatus
picture input to just one side of brain
screen blocks objects on table from view

Picture to left brain
can name the object
left hand cannot identify by touch
Picture to right brain
can’t name the object
left hand can identify by touch
The ‘Split Brain’ studies

Localization of function

Occipital Lobe
Input from Optic nerve
Contains primary visual cortex
most is on surface inside central fissure
Outputs to parietal and temporal lobes
Occipital
Lobe
Visual
Lobe

Temporal Lobe
Inputs are auditory, visual patterns
speech recognition
face recognition
word recognition
memory formation
Outputs to limbic System, basal Ganglia, and brainstem
Contains primary auditory cortex

Parietal Lobe
Inputs from multiple senses
contains primary somatosensory cortex
borders visual & auditory cortex
Outputs to Frontal lobe
hand-eye coordination
eye movements
attention

Frontal Lobe
Contains primary motor cortex
No direct sensory input
Important planning and sequencing areas
Broca’s area for speech
Prefrontal area for working memory

Frontal Lobe Disorders
Broca’s area
productive aphasia
Prefrontal area
lose track of ongoing context
fail to inhibit inappropriate responses
Often measured with the Wisconsin Card Sorting Task

Wisconsin Card Sorting Task
Patient is given a deck of 64 different cards
Told to place each card under the one it best matches
Told correct or incorrect after each card
Row of 4 example cards set out
Must deduce what the underlying rule is.
Correct!

Wisconsin Card Sorting Task

Wisconsin Card Sorting Task

Wisconsin Card Sorting Task

Wisconsin Card Sorting Task

Wisconsin Card Sorting Task

Wisconsin Card Sorting Task