The Nervous SystemThe Nervous System
Or:
What makes me do that Voodoo that I Do So Well
Nervous SystemNervous System
Central– Brain– Spinal Cord
Peripheral– Everything Else
Central Nervous System Central Nervous System (CNS)(CNS)
Brain– Lobes
Frontal Parietal Temporal Occipital
– Cerebellum
Spinal Cord
BrainBrain Frontal Lobe
The Cerebral Cortex: The Cerebral Cortex: Localization of FunctionLocalization of Function
Brodmann’s Area Map of the brain (Based on cyto-architecture)– Language and
Comprehension– Cognition– Emotion– Motor– Somatosensory– Vision
The Cerebral Cortex: Location The Cerebral Cortex: Location of Functionof Function
Can also be organized into:– Motor Cortex– Somatosensory Cortex– Association Cortex
The Homunculus– Penfield
Lateralization of FunctionLateralization of Function
Two halves (hemispheres) of our brain – connected by the corpus callosum
Right Brain / Left Brain specialization The right brain
– responsible for movement on the left-side of the body The left brain
– specialized for language (Stroke victims) The right brain
– specialized for spatial relationships
Roger Sperry (1913-1994): Roger Sperry (1913-1994): Split Brain ResearchSplit Brain Research
Two halves of the brain are in constant communication with each other
if you cut the corpus callosum you disrupt the communication (severe epilepsy)– Visual abilities (L vs. R visual field)– Tactile stimulation– Auditory ability
Sperry: Visual AbilitiesSperry: Visual Abilities Flashing lights across both visual
fields,– PTs responds by saying they only saw
lights on the R side of the board Flashing lights to the left visual field
– the PTs said they saw nothing But if asked to point to the lights
presented in both visual fields they would respond correctly (identifying all the lights)
Conclusion: Both halves were perceiving the lights, but only the left half of the brain could respond verbally
Sperry: Tactile AbilitiesSperry: Tactile Abilities
When a hidden object is placed in right hand, the PT was able to name what it was
When a hidden object is placed in the left hand, the PT could not name or describe it
Peripheral Nervous SystemPeripheral Nervous System
PNSPNS
ReceptorsAfferent NeuronsEfferent NeuronsEffectors
Receptors - VisionReceptors - Vision
Rods– rods are responsible for vision in dim light
do not support colour vision in very dim light, all objects appear in different
shades of grey
Receptors - Vision (con’t)Receptors - Vision (con’t)
Cones– three types (in humans), each maximally
sensitive to a different wavelength of light less sensitive to light than rods, but faster temporal
response
– concentrated mostly in the centre of the retina (the "fovea")
(it's hard to read by moonlight due to the low spatial resolution of the rods)
Receptors - SkinReceptors - Skin
Hair Follicle Ending – A-beta
– Responds to hair displacement
Receptors - SkinReceptors - Skin
Ruffini Endings – A-beta – Responds to pressure
on skin
Receptors - SkinReceptors - Skin
Krause corpuscle – A-beta– Responds to pressure
Receptors - SkinReceptors - Skin
Pacinian corpuscle – A-beta – Responds to vibration.
Most sensitive in 150-300 Hz range
Receptors - SkinReceptors - Skin
Meissner corpuscle – A-beta – Responds to vibration.
Most sensitive in 20-40 Hz range
Receptors - SkinReceptors - Skin
Free nerve endings – A-delta and C – Different types of free
nerve endings that respond to mechanical, thermal or noxious stimulation
Skin ReceptorsSkin Receptors
Merkel Cells – A-beta – Responds to pressure
of the skin
Receptors - SoundReceptors - Sound
Cochlea Basilar Membrane
– Cilia
Auditory Nerve
Chemical ReceptorsChemical Receptors
Taste Bud – approximately 10,000
in humans) is made up of many (between 50-150) receptor cells. Receptor cells live for only 1 to 2 weeks and then are replaced
– Each receptor in a taste bud responds best to one of the basic tastes.
OlfactionOlfaction
OlfactionOlfaction
Reflex ArcReflex Arc
Stimulus– afferent
Signal Split Response
– efferent
The ANSThe ANS
Regulates physiological activity– Involuntary– Not under conscious control
The ANSThe ANS
Consists of two divisions– The Sympathetic System– The Parasympathetic System
The ANSThe ANS
Eye Salivary glands Trachea Bronchi Heart Stomach
Liver Gallbladder Adrenal Glands Kidney GI Tract Urinary Bladder
The ANSThe ANS
Function is to maintain Homeostasis– Tendency to maintain a variable (like
temperature) within a fixed range
Control steady state of the internal environment
Anatomy of the ANSAnatomy of the ANS
Control centers are located within the CNS– The hypothalamus (the brain)
Peripheral network of afferent and efferent nerves
The HypothalamusThe Hypothalamus
The HypothalamusThe Hypothalamus
Regulation of Body TemperatureWater BalanceBlood PressureEmotionSleepSexual Reflexes
Efferent NervesEfferent Nerves
These are Motor or Effector nervesComprised of a two-neuron chain
– Preganglionic neuron Originates in the CNS
– Postganglionic neuron Originates in the ganglion
GanglionGanglion
Loosely organized collection of nerve fibers and cell bodies
Postganglionic NeuronsPostganglionic Neurons
Directly innervate effector organs– Impulse at the neuroeffector junction
CNS ANSOrgan
Pre Post
Ganglion
Afferent NeuronsAfferent Neurons
Usually Sensory Nerves– Transmit unconscious info
Blood pressure Heart rate GI motility Visceral info (semi conscious)
– Nausea. Hunger
ANS DivisionsANS Divisions
ParasympatheticParasympathetic
Ganglia are near the innervated organ– Long Pre short Post
The post innervates only a single organ Reflects function of discretely regulating processes
such as digestion
SympatheticSympathetic
Ganglia are near the vertebrae– Short pre Long post
The post has wide diffusion Reflects function of a whole body response
– The fight or flight response
– One nerve cell may innervate 25,000 effector cells
Adrenal GlandsAdrenal Glands
Adrenal GlandsAdrenal Glands
Consists of two parts– Adrenal cortex– Adrenal Medulla
Adrenal GlandsAdrenal Glands
Adrenal CortexAdrenal Cortex
Produces a hormone called cortisol– Mobilizes energy reserves and suppresses
immune system
Physiology of the ANSPhysiology of the ANS
Acetylcholine (ACh)Acetylcholine (ACh)
A major NT in the ANS and CNSCatalyzed by Choline acetyltransferaseAcetyl CoA + Choline ACH + CoA
Dopamine, Norepinephrine Dopamine, Norepinephrine and Epinephrineand Epinephrine
Major NTs in the CNS and ANS
Tyrosine
DOPA
DA
NE
E
Tyrosine Hydroxalase
Aromatic amino-acid decarboxylase
DA-Beta Decarboxylase
Phenylethanolamine N methyltransferase
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