central nervous system

Central Nervous System

Central Nervous System (CNS) Consists of the brain and spinal cord Integrates and processes information

by nerves

Peripheral Nervous System (PNS) Divided into Somatic and Autonomic

systemsSomatic Nervous System (Voluntary) Consists of sensory receptors Nerves that carry sensory information or

instructions to the CNS to the skeletal muscles

Autonomic Nervous System (Involuntary) Controls glandular secretions Sympathetic and parasympathetic

Autonomic Nervous System (Involuntary)

Autonomic Nervous System

• Sympathetic nervous systemallow body to function under stressfight or flight

• Parasympathetic nervous systemcontrols vegetative functionsfeed or breed or restconstant opposition to sympathetic system

The Organization of the Brain

Cells of the Nervous System Two main cells:

1) Neurons Specialized cells to respond to

physical and chemical stimuli Release chemicals that regulate

various body processes Individual neurons are organized

into tissues called nerves

Cells of the Nervous System Cont…

2) Glial Cells Supports the nervous system tissue Removes waste Defend against infections

The structure of a neuron Specialized cell structures that enable

them to transmit nerve impulses Features:

1) Dendrites Receive nerve impulses from other

neurons and sends back to the cell body 2) Cell body Site of metabolic reactions Processes input from dendrites and

sends to the axon

The structure of a neuron cont…3) Axon Conducts impulses away from the

cell body Releases chemical signals to the

receptors and dendrites Myelin sheath protects the neuron

and speeds up the rate of nerve impulse transmission

Classifying Neurons

Nerve Impulse Generation and Resting Membrane Potential

Nerve Impulses Galvani and Volta performed experiments using

leg muscles Muscles contracted after experiencing

stimulation from electric currents Resting neuron: the outside of the cellular

membrane is negative, relative to the inside This causes a potential difference between the

inside and outside of the neuron

More on Resting Potential

Potential difference across the membrane of a resting neuron

Remains relatively constant for all neurons, approximately -70 mV

Controlled by electrochemical gradients, protein presence and active transport

Electrochemical Gradient Large, negatively charged proteins cause

the inside of the membrane to be charged

Potassium and sodium ions control the electrochemical gradient

Gradient is adjusted, maintained and controlled through active transport

Blue – SodiumYellow – ChlorineOrange – AnionsPurple - Potassium

Controlled by various channel proteins such as the one used for potassium shown in the diagram

Action Potential

What Is It?

Movement of electrical impulse

Rapid change in polarity

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__the_nerve_impulse.html

History

Discovered by 2 British Scientists Used giant squid Revealed that action potential is

dependant on voltage gated Na and K channels

When does this occur?

Occurs when Threshold Potential occurs

Threshold Potential Varies

Strength of stimulus does not = strength of Action Potential

Events

Action Potential triggered by Threshold Potential

Voltage gated Sodium channels open Sodium channel closed Potassium

Channels open Potassium Channels closes after

hyperpolarization Membrane Potential brought back to

-70mV

Does natural = safe? Natural and synthetic neurotoxins work by

blocking the “action potential” Tetrodoxin (pufferfish) blocks sodium

channel Dendrotoxin (black mamba) blocks

potassium channel Applications: chemical weapons?

Insecticides?

Extended Information

Tetraodontidae (Pufferfish)

Contains Tetrotoxin (1200x more poisonous than cyanide)

Synaptic Transmission

Synaptic Transmission

Postsynaptic neuron

Presynaptic neuron

Synaptic cleft

(protein)http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter14/animation__chemical_synapse__quiz_1_.html

Reflex Arc

Reflex Arc and Feedback

Reflex arc: simple connection of neurons that results in a reflex action in response to a stimulus

Your nervous system reacts to sensory input through a basic impulse pathway

Reflexes: Sudden involuntary responses to certain stimuli

Requires 3 neurons (sensory input, integration, motor output)

Reflex Arc and Feedback

Sensory Input Neuron

Sensory receptors such as those in the skin, receive stimuli and form a nerve impulse

Sensory neurons transmit impulses from the sensory receptors to the central nervous system

Integration Neurons

Interneurons are found entirely within the central nervous system

They act as a link between the sensory and motor neurons

They process and integrate incoming sensory information and relay outgoing motor information

Motor Output

Motor neuron transmits information from the central nervous system to effectors

Effectors include muscles, glands and other organs that respond to impulses from motor neurons

Putting it all together

1. receptors in skin sense the pressure or temperature change

2. Impulse is carried by the sensory neurons then activates the internuron in the spinal cord

3. The interneuron signals the motor neuron to instruct the muscle

Loss of Homeostasis

What can be seen through synaptic transmission? Parkinson’s Dopamine▪ Controls body movements▪ Sensations of pleasure

Serotonin▪ Regulates temperature and sensory

perception ▪ Depression

Deep Brain Stimulation

Take Home Message

Synapse = connection between neurons or neuron and effector

Impacts homeostasis through neurotransmitters Movement Temperature Natural painkilling Danger/stress reactions