Nervous System: Part 2Nervous System: Part 2

Organization of the Nervous SystemOrganization of the Nervous SystemThe SensesThe Senses

Nervous System OrganizationNervous System Organization

Central Nervous System (CNS)

Peripheral Nervous System (PNS)

spinal cordbrain

Sensory nervescarry sensory informationinto brain and spinal cord

Motor nervescarry motor informationfrom CNS to effectors

somatic sensorynerves: signals

from skin,muscles,

joints, specialsenses

visceral sensorynerves:

signals frombody organs

Somatic motornerves: signals

to skeletalmuscles,

voluntary

Autonomic motor nerves:

signals to smoothmuscle, cardiacmuscle, glands,

involuntary

Sympatheticdivision

“fight or flight”

Parasympatheticdivision

“rest and digest”

Parts of the BrainParts of the Brain

musclecoordination

Cortex: thinking, learning, memory, speech movement,

senses

breathing, heart rate, blood pressure

sends sensory input to cerebrum

homeostasis

Spinal Cord Spinal Cord and Reflex Arcsand Reflex Arcs

white matter

ventral root

axon of motor neuron

axon of sensory neuron

cell body of sensory neuron

pin

dorsal root ganglion

cell body of interneuron

Dorsalgray matter

central canal

ventral horn

sensoryreceptor(in skin)

effector(muscle)

cell body ofmotor neuron

Ventral

dorsalhorn

Involve the Somatic Nervous System

Autonomic Nervous SystemAutonomic Nervous System

dilates pupilsconstricts

pupils

speeds heart slows heart

dilates air passages

constricts bronchioles

decreases stomach and

intestinal activity

increases stomach and

intestinal activity

Nervous System Case Study: Nervous System Case Study: HemimegalenchephalyHemimegalenchephaly

• Dylan Catania was born with an oversized right Dylan Catania was born with an oversized right hemisphere in his brain that was causing constant hemisphere in his brain that was causing constant seizuresseizures

• His only hope of survival and brain development His only hope of survival and brain development involved early surgery to sever the connections involved early surgery to sever the connections between the right and left hemispheres of the brainbetween the right and left hemispheres of the brain

Nervous System Case Study: Nervous System Case Study: HemimegalenchephalyHemimegalenchephaly

Nervous System Case Study: Nervous System Case Study: Surgery for HemimegalenchephalySurgery for Hemimegalenchephaly

Nervous System Case Study: Nervous System Case Study: Surgery for HemimegalenchephalySurgery for Hemimegalenchephaly

Nervous System Case Study: Nervous System Case Study: HemimegalenchephalyHemimegalenchephaly

Dylan has been seizure free Dylan has been seizure free since his surgery!since his surgery!

Sensation and PerceptionSensation and Perception

Sensation: impulses arrive

at cerebral cortex

Perception: cortex interprets

meaning of sensations

Sensory Areas on Cerebral CortexSensory Areas on Cerebral Cortex

Sense of Vision: Structure of the EyeSense of Vision: Structure of the Eyephotoreceptors

detect light

takes nerve impulses to

brain

focuses light on retina

lens

photoreceptors

Photoreceptors synapse with neurons that take signal to optic nerve

Sense of Vision: PhotoreceptorsSense of Vision: Photoreceptors

detects color detects light absorbs light,initiates series

of steps leading to nerve signal

Sense of Hearing: Sense of Hearing: Structure of the EarStructure of the Ear

1. Sound enters auditory canal

3. Ossicles (bones) of middle ear multiply pressure of vibration

4. Membrane-covered opening transfers pressure to inner ear

5. Pressure enters fluid-filled chamber containing mechanoreceptors

2. Eardrum vibrates slightly due to sound waves

Sense of Hearing: MechanoreceptorsSense of Hearing: Mechanoreceptors

Vibrates in response to pressure in

inner ear

mechanoreceptor

Bend when basilar membrane moves

takes nerve impulses to

brain

Sense of Taste: Sense of Taste: ChemoreceptorsChemoreceptors

Taste buds occur along the walls of

papillae

Molecules bind to receptors on

microvilli of taste cells

Nerve impulses are sent to brain

chemoreceptor

Signal from receptor is transmitted

within the cell

Sense of TasteSense of TasteSignal Transmission for Salty and Sour TastesSignal Transmission for Salty and Sour Tastes

Sodium binds and opens a channel for more sodium

to enter

Protons bind and open a channel

for more protons to enter

Release of calcium triggers

neurotransmitter release and neuron

stimulation

Sense of TasteSense of TasteSignal Transmission for Sweet and Bitter TastesSignal Transmission for Sweet and Bitter Tastes

Internal communication leads to neuron

stimulation