Coordinating Movement, etc.! Nerve SystemsCoordinating Movement, etc.! Nerve Systems

Electrical Transmission -- Chemical Connection.

Released from vesicles

inputnucleus

transmission

output

In peripheral nerves, the tissue is mostly axons, tightly In peripheral nerves, the tissue is mostly axons, tightly packed like the wires in a complex phone cable!packed like the wires in a complex phone cable!

Conduction of action potential along neuronConduction of action potential along neuron

A bit slower than electrical wire, but does not need heavy, rigid metal and, for typical organism sizes, is fast enough!

Myelin Sheath Increases Rate of TransmissionMyelin Sheath Increases Rate of Transmission

Multiple Sclerosis and Guillain-Barré SyndromeMultiple Sclerosis and Guillain-Barré Syndrome

Electrical current passes rapidly (150 vs 30 m/s) down the sheathed axon segments

Coordinating Movement, etc.! Nerve SystemsCoordinating Movement, etc.! Nerve Systems

Regulation by ACH or NE.

Neurotransmitter RolesNeurotransmitter Roles

Opposing Muscles

Glands

Neurotransmitter diffusion is fast enough…Neurotransmitter diffusion is fast enough…

Because the synapse gap is about 0.001 mmBecause the synapse gap is about 0.001 mm

AcetylCholineAcetylCholine

• Stimulates muscle contraction in the Stimulates muscle contraction in the neuromuscular junction.neuromuscular junction.

• Atropine blocks Ach reception…relaxation of irisAtropine blocks Ach reception…relaxation of iris• Slows the pacemaker in the heart.Slows the pacemaker in the heart.

Adrenaline (nor-epinephrine)Adrenaline (nor-epinephrine)

• Promotes nutritional release to bloodPromotes nutritional release to blood

• Speeds the pacemaker in the heart.Speeds the pacemaker in the heart.

• Higher blood pressure, more oxygenationHigher blood pressure, more oxygenation

• Fright, Flight, or Fight stimulantFright, Flight, or Fight stimulant

Simple Nervous SystemsSimple Nervous Systems> > dendritedendriteO O somasoma------- ------- axonaxon> > synaptic terminalsynaptic terminal

S sensorS sensorM muscle cellM muscle cell

>O------------>>O------------> neuron neuron-->-->>O>>O>>O--- interneuron>O--- interneuron>O------------>>O------------>M motor neuronM motor neuronSS>O---------->>O----------> sensory neuron sensory neuron

Reflex Arc:Reflex Arc:S>O---------->>O>>O------------M (one of each)S>O---------->>O>>O------------M (one of each)tendon spinal cord muscletendon spinal cord muscle

A neuron can have many synaptic terminalsA neuron can have many synaptic terminals

These synaptic terminals are neuromuscular These synaptic terminals are neuromuscular junctions…how can you tell?junctions…how can you tell?

The spinal cord has cell bodies surrounded by dendrites The spinal cord has cell bodies surrounded by dendrites and axonsand axons

Reflex arcs connect via interneurons here in the Reflex arcs connect via interneurons here in the spinal cord!spinal cord!

Complex Nervous SystemsComplex Nervous Systems

• Cell bodies in ganglia in Cell bodies in ganglia in peripheral nervesperipheral nerves

• Cell bodies in spinal cord Cell bodies in spinal cord and brainand brain

• Much of Central Nerve Much of Central Nerve System are interneuronsSystem are interneurons

• Connect to Sensors, Connect to Sensors, Muscles, Glands, etc.Muscles, Glands, etc.

• Connect to each other!Connect to each other!

Mapping a Portion of the BrainMapping a Portion of the Brain

• Here you can see Here you can see where portions of where portions of the brain map out to the brain map out to body parts.body parts.

• You might notice You might notice that the body has that the body has biases in terms of biases in terms of mapping various mapping various areas.areas.

• The head and face The head and face covers as much covers as much neural tissue as the neural tissue as the rest of the body.rest of the body.

The Sensory InputsThe Sensory Inputs

• Taste sensors have Taste sensors have receptors for molecules receptors for molecules “of interest” to the “of interest” to the organism.organism.

• Taste cells transduce Taste cells transduce receptor-molecule receptor-molecule complex into action complex into action potential.potential.

• Action potential is Action potential is transmitted to sensory transmitted to sensory neuron with soma in a neuron with soma in a nearby ganglion.nearby ganglion.

• Sensory neuron may be Sensory neuron may be connected to a reflex arc connected to a reflex arc and/or the central and/or the central nervous system.nervous system.

The sensitive tongue of reptiles is for “tasting” the air!The sensitive tongue of reptiles is for “tasting” the air!

Chemotaxis is Signal Tranduction Too!Chemotaxis is Signal Tranduction Too!

• Bacterium movement Bacterium movement haphazard without signalhaphazard without signal

• Straight line movement in Straight line movement in signal pathsignal path

• Haphazard movement Haphazard movement when off-targetwhen off-target

• Restored straight line Restored straight line movement on pathmovement on path

The Largest Organ of the Body has Many Sensors!The Largest Organ of the Body has Many Sensors!

• Dendrites (nerve endings) Dendrites (nerve endings) for pain, and itchfor pain, and itch

• Pressure sensorsPressure sensors• Stretch receptors to hair Stretch receptors to hair

shaftsshafts• Touch and pressure Touch and pressure

receptorsreceptors• Temperature flow Temperature flow

sensors… can be sensors… can be confused!confused!

• Sensor density varies Sensor density varies over the body…face and over the body…face and hands are dense!hands are dense!

Arthropod legs have chemical, pressure, and other sensorsArthropod legs have chemical, pressure, and other sensors

Sound WavesSound Waves

• Sound travels as Sound travels as pressure wavespressure waves

• Wavelength Wavelength (frequency) is pitch (frequency) is pitch (short=fast=high)(short=fast=high)

• Amplitude (height) is Amplitude (height) is intensity (decibels)intensity (decibels)

• >100 = damaging>100 = damaging

The Sound TransducerThe Sound Transducer

• Sound collected by outer earSound collected by outer ear• Pressure waves vibrate eardrumPressure waves vibrate eardrum• Former jawbones amplify the Former jawbones amplify the

vibrationsvibrations• Tapping on Cochlea (inner ear) Tapping on Cochlea (inner ear)

vibrates fluid-surrounded vibrates fluid-surrounded ciliated transduction cellsciliated transduction cells

• Action potential sent to auditory Action potential sent to auditory nervesnerves

• Auditory nerves connect to CNSAuditory nerves connect to CNS• Perception of sound in CNSPerception of sound in CNS• Cultural appreciation based Cultural appreciation based

upon experienceupon experience• Plants cannot do this!Plants cannot do this!

The antennae of a moth are for chemical and sonic stimuliThe antennae of a moth are for chemical and sonic stimuli