Lesson 3 The Nervous System

• Nervous system - includes biochemical processes that affect our moods and influence behavior
• Nerve cell or neuron - basic building block of the nervous system
• A nerve cell is composed of cell body(soma), axons, and dendrites
• Cell body(soma) - contains the nucleus of the cell
• axons and dendrites - two fibers that branch off from the cell body
• axons - send impulse from the cell body to other neurons or the muscles
• each branch of the axon ends in a terminal button
• axons in the brain and spinal cord are covered by white fatty layers called myelin sheath
• myelin sheath - covers the axon, acts as an insulator, and aids the conduction of impulses
• nerve trunks - connect neurons from the brain and spinal cord to outer body parts
• dendrites - receive nerve impulses from other neurons and send them to the cell body
• types of neurons - motor neurons, sensory or afferent(incoming) neurons, and interneurons or association neurons
• motor neurons - relay messages from the brain to the muscles or glands, the cell body is located in the spinal cord
• sensory or afferent(incoming) neurons - receive stimuli and carry them to the brain(sensation) for interpretation(perception), the cell body is located in the nerve root
• interneurons or association neurons - connect sensory neurons to motor neurons
• absolute refractory period - a period that a nerve fiber is completely unresponsive to new stimulation
• synapse - gaps between the axon tip of one neuron and the dendrite or the cell body of another neuron
• Synaptic Vesicles - tiny sacs that release a transmitting substance that crosses the synaptic gap
• Nerve impulses - pass only from the axon to the dendrite or the cell body, never in the opposite direction
• The Central Nervous System - consists of the brain and spinal cord
• Spinal Cord - serves as a pathway through which nerve impulses from sensory organs(affectors) pass to the brain(effector)
• The Brain has three parts: the hindbrain, the midbrain, and the forebrain
• The Forebrain - the largest part of the brain
• three parts of the forebrain - cerebrum, thalamus, and hypothalamus
• The Hindbrain - responsible for muscle tone, body balance, and coordinator of voluntary movements
• The Midbrain - controls auditory and visual responses
• three parts of the hindbrain - the medulla, the cerebellum, and the pons
• The Medulla - controls respiration, digestion, and circulation
• The Cerebellum - the "little brain", governs body balance, posture, and muscle coordination
• Pons - contain nerve fibers that connect the upper brain to the spinal cord
• The Peripheral Nervous System - consists of the nerves that connect the brain and spinal cord to the rest of the body
• two systems of the peripheral nervous system: the somatic nervous system, and the autonomic nervous system
• The Somatic Nervous System - concerned with voluntary muscle movements and with carrying most sensory input to the brain
• The Autonomic Nervous System - regulates the glands, internal organs and blood vessels, and other involuntary movements
• two divisions of the autonomic nervous system: the sympathetic division, and the parasympathetic division
• the sympathetic division - associated with the fight-or-flight response, prepares the body for action
• the parasympathetic division - day-to-day control of the individual functions of bodily organs
• stimulus activates a receptor cell
• reflex arc - the circuit in which nerve impulses travel
• Cerebrum - governs higher emotion, learning, thinking, remembering, and sense perception