The Nervous System… … is an organ system consisting of special cells called neurons that transmit signals between different parts of the body.
The Nervous System… It connects the different parts of the body together… like phones and internet connect the world!
Functions The nervous system: ▫Enables us to adapt and react to changes in our internal and external environments.
Functions Nerves also act as a control system regulating visceral organs ▫Heart ▫Stomach ▫Intestines and others Nerves are also in charge when we are unconscious. ▫Knocked unconscious ▫Sleeping ▫States of coma
Neurons The nervous system is composed entirely of neurons These special cells run all throughout your body! The average adult brain contains about 100 billion neurons!
The neuron: The neuron is an electrically excitable specialized cell that processes and transmits information by electrical and chemical signaling. They enable many functions like: ▫Movement ▫Perception ▫Thought ▫Emotion ▫Learning
Parts of a neuron Soma – neuron cell body Dendrite – branches that receive messages from other neurons Axon – long branch that conducts the message away from the soma Axon Terminals – The end of the axon where the message is passed to the next neuron Myelin Sheath – insulation covering the axon Schwann Cells – Surround the axon and create the myelin sheath
How they work together Axon terminals send electrochemical messages to the dendrites of a neighboring neuron The terminals can send messages to multiple dendrites The dendrites can receive messages from multiple axons
The message The ‘message’ that is passed along consists of electrical and chemical components ▫The message itself is electrical ▫It is move along through the axon and from neuron to neuron via chemical processes using ions such as: Sodium Potassium Chloride Calcium
Reflex Arc is the pathway that nerves follow Afferent neurons pick up the message from the source Efferent neurons bring the response back to the muscle
Two halves of the nervous system Central Nervous SystemPeripheral Nervous System Consists of ▫Brain ▫Spinal Cord Consists of: ▫All nerves outside the brain and spinal cord ▫Cranial Nerves ▫Spinal Nerves
Two halves of the peripheral nervous system Somatic Nervous SystemAutonomic Nervous System Associated with ▫Voluntary muscles ▫(skeletal) ▫Sensory reception of external stimuli Efferent nerves Associated with unconscious control of vitals: ▫Heart rate ▫Digestion ▫Breathing Afferent nerves
Autonomic Nervous System SympatheticParasympathetic Remember: FIGHT or FLIGHT ▫Adrenaline is released ▫Heart rate increases ▫Blood vessels dilate ▫Pupils dilate ▫Digestion stops Remember: REST and DIGEST ▫Acetylcholine is released ▫Heart rate slows ▫Blood vessels constrict ▫Pupils constrict ▫Digestion starts again