The Nervous System

Control Center for Maintaining Homeostasis

Nervous System

The nervous system coordinates the activities of all of the body’s organ systems so that they work in concert with one another

What systems must cooperate during exercise?

What do we use to respond to changes in the external environment?

Do the senses operate individually?

Components of the Nervous System

Two main sectionsThe Central Nervous System

Brain and spinal cordcoordinating center for incoming and outgoing

informationPeripheral Nervous system

Nerves that extend to the rest of the bodyCarries information between organs and the CNS.

Two basic types of Nerves

sensory or afferent nervesCarry signals to CNS

motor or efferent nervesCarry signals from CNS

Peripheral Nervous System (PNS)

Somatic nervesconnect skin, skeletal muscles and bones to CNS

Autonomic nervesConnect visceral organs

Somatic nerves

control skeletal muscles, bones and skinVoluntarySensory to CNSCNS to Motor

Reflexes

Autonomic nerves

Special motor nerves that control the internal organsComprised of two divisions that work in opposition

Sympathetic nerves• Fight or flight response (survival)

Parasympathetic nerves• Active when body is at rest • “resting and digesting”

Autonomic

Broken into two different divisions (systems) the Parasympathetic and Sympathetic

Parasympathetic House keeper division Uses acetylcholine (neurotransmitter)

Sympathetic Excitatory division Uses norephinephrine (neurotransmitter)

What is a Nerve

A Collection of nerve fibers in the peripheral nervous system

Cells of the Nervous System

Two type of cells that make up nerve fibers

NeuronsSupportive cellsNeurogliaSchwann cells

Nerve Cells

Neurons transmit electrochemical signals along their length

cell bodydendritesAxonaxon terminals

Cell Body

The Cell body contains all of the cell organelles. Such as the:

NucleusMitochondria…

Important in the manufacturing of Neural transmitters.

Dendrites

The Branching structure that receives signals from other Nerves or if they are sensory Neurons receive signals externally.Conducts the nerve impulse to towards the cell body.

Axon

the long extension of a neuron that carries nerve impulses away from the body of the cell.

Link the Nerve to either the next nerve (sensory or interneuron) or to a muscle (motor neuron)

Axon

Usually much longer than a Dendrite and usually covered with a insulating layer called the myelin sheath.axon terminals - the the hair-like ends of axon

Release chemicals (neurotransmitters) to transmit signal to next neuron in junction Junctions between neurons and another cell called a synapse

Supportive Nerve Cells

Glial Cells supporting cells that usually form a type of protection and insulation for electical conduction

Proper names for CNS and PNSNeuroglia in CNS

Schwann cells in PNS

Glial Cells in PNS

Myelin Sheath

Myelin is the fatty substance that wraps around axons and protects/insulates themFormed by Schwann Cells in the PNS,

gaps called Nodes of Ranvier are left between the myelinMyelination and the Nodes of Ranvier increase the speed that the electrical signal moves down the axon.

Myelin Sheath

New research suggest that the electrical wave that travels down the axon actually jumps from one node to another. Thereby increasing the speed of transmission.Multiple sclerosis is caused by the destruction of the myelin sheath

Neurilemma

All nerves in the peripheral nervous system contain a thin membrane called the neurilemma.It surrounds the axon and promotes regeneration of damaged axons.

Neurilemma

Nerves in the brain that contain myelin sheath and neurilemma are called white matter and those that aren’t is the gray matter. Damage to the gray matter is permanent.

Different Types of Neurons

They all carry electro-chemical nerve signals, but differ in structure

(the number of processes, or axons, emanating from the cell body) and are found in different parts of the body.

Sensory neurons Motor-neurons Interneurons

Interneurons

form all the neural wiring within the CNS. have two axons (instead of an axon and a dendrite). one axon communicates with the spinal cordOther one with either the skin or muscle.