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