Nervous System
Responds to stimuli to maintain homeostasis. Stimulus (Stimuli) = a signal to which an organism reacts Response = some action or movement of an organism brought on by a stimulus
Nerve cells The cells of the nervous system are called neurons. Neurons carry messages called impulses Nerves = send messages to the spinal cord, muscles, and glands for response
The Neuron Cell body (cyton): contains nucleus, cell organelles; site of metabolic activities Nucleus : contains the genetic material Dendrite: receives impulses from other neurons and carries them toward the cell body
The Neuron Axon: carries impulses away from the cell body Schwann cell nucleus Schwann cell: surrounds the axon; produces the myelin sheath
The Neuron node of Ranvier: gap between neighboring Schwann cells Myelin sheath: insulation that increases the speed at which the impulse can travel
The Neuron Terminal branches the axon terminates (ends) with the terminal branches Synaptic knobs: release neurotransmitters into the synapse
The Neuron Synapse: small gap between two successive neurons ***Neurotransmitters are chemicals used to transmit an impulse from the axon of one neuron to the dendrites of the next neuron
Types of Neurons Sensory Neurons: transmit impulses from sensory organs (receptors) to the spinal cord and brain Sensory organs: eyes, ears, nose, mouth, skin
Types of Neurons Motor Neurons: transmit impulses from the spinal cord and brain to muscles and glands (effectors)
Types of Neurons Interneurons: connect sensory and motor neurons Found ONLY in the Central Nervous System (brain and spinal cord)
Reflex Arc Receptor sensory neuron interneuron motor neuron effector
Reflexes Automatic responses to stimuli We do not have to think about the response They are inborn All connections have been formed by the time we are born They are fast They take the shortest path The speed of the response is protective reflex arc animation
Central Nervous System Part of the nervous system that contains the brain and spinal cord.
The Brain Coordinates all of your body activities The brain is made of 100 billion neurons Interprets stimuli, sends impulses to the body
Cerebrum Largest part of the brain Thinking takes place here Controls: Memory Movement Thinking
Cerebellum Coordinates voluntary muscle movement Maintains muscle tone Maintains balance Receives stimuli from eyes, ears, muscles, and tendons.
Brain Stem Located at the base of the brain Connects the brain to the spinal cord Contains: Midbrain and Pons = pathways connecting various parts of the brain with each other Medulla = controls involuntary actions
Spinal Cord Extension of the brain stem Made of bundles of neurons that carries impulses to all parts of the body
The peripheral nervous system (PNS) All the nerves that extend out of the brain an spinal cord Most of the PNS is under your direct control
THE PNS Autonomic Nervous System: controls body activities that are involuntary Contractions of heart muscle Movement of smooth muscles
Disorders of the Nervous System Alzheimer's Diseases A progressive disease that destroys memory and other important mental functions Brain cell connections and the cells themselves degenerate and die There is no cure
Disorders of the Nervous System Amyotrophic Lateral Sclerosis (ALS) Weakens muscles and impacts physical function Nerve cells break down, which reduces the function of muscles. There is no cure for ALS
Disorders of the Nervous System Epilepsy A disorder in which nerve cell activity in the brain is disturbed, causing seizures Can be caused by genetics or a brain injury Treated by medications, surgery, devices, or dietary changes
Disorders of the Nervous System Meningitis Infection and inflammation of the membranes surrounding the brain or spinal cord Vaccines can prevent some forms of meningitis Depending on the cause, it may get better on its own, or it can be life-threatening
Disorders of the Nervous System Multiple Sclerosis Our WBCs attack and destroy Schwann cells This slows down the impulses from neurons