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 sections The Central Nervous System Brain and spinal cord coordinating center for incoming and outgoing information Peripheral Nervous system Nerves that extend to the rest of the body Carries information between organs and the CNS.

Two basic types of Nerves sensory or afferent nerves Carry signals to CNS motor or efferent nerves Carry signals from CNS

Peripheral Nervous System (PNS) Somatic nerves connect skin, skeletal muscles and bones to CNS Autonomic nerves Connect visceral organs

Somatic nerves control skeletal muscles, bones and skin Voluntary Sensory to CNS CNS to Motor Reflexes

Autonomic nerves Special motor nerves that control the internal organs Comprised 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 Neurons Supportive cells Neuroglia Schwann cells

Nerve Cells Neurons transmit electrochemical signals along their length cell body dendrites Axon axon terminals

Cell Body The Cell body contains all of the cell organelles. Such as the: Nucleus Mitochondria… 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 PNS Neuroglia in CNS Schwann cells in PNS

Glial Cells in PNS

Myelin Sheath Myelin is the fatty substance that wraps around axons and protects/insulates them Formed by Schwann Cells in the PNS, gaps called Nodes of Ranvier are left between the myelin Myelination 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 cord Other one with either the skin or muscle.