The Nervous System The Nervous System Chapter 6 Chapter 6
The Nervous SystemThe Nervous SystemChapter 6Chapter 6
The Nervous SystemThe Nervous SystemChapter 6Chapter 6
The Nervous system has three major functions:
Sensory
monitors internal & external environment through presence of receptors
Integration
Interprets sensory information
Motor
response to information processed through stimulation of effectors
Two Anatomical Divisions Central nervous system (CNS)
Brain Spinal cord
Peripheral nervous system (PNS) All the neural tissue outside CNS Afferent division (sensory input) Efferent division (motor output)
Organization of the Nervous System
Afferent vs Efferent
Afferent Nerves
Sensory Nerves Receive Information Transmit sensory
information gathered from the skin, muscles, and joints to the CNS
Efferent Nerves
Motor Nerves Send information on Carries information from
the CNS out to the muscles and glands
Sensory nerve cells: Afferent pathwayCNS (brain and spinal cord): Integration centersMotor nerve cells: Efferent pathway
Organization of the Nervous System
Brain & spinal cord
Cells of the Nervous System
Two types of neural cells in the nervous system:
Neurons
Process, transfer, and store information
Neuroglia – (also called “glial cells”)
Support and protect neurons
Structure of a Neuron
•Most axons of the nervous system are surrounded by myelin
•The presence of myelin speeds up the transmission of signals along the axon
•Myelin will get laid down in segments along the axon, leaving unmyelinated gaps known as “nodes of Ranvier”
ELECTRICITY!!!
Conductivity: the property of neurons that give them the ability to transmit nerve impulses
Electrical impulses (action potentials) are “all-or-none” responses
Axon terminals do not actually touch the other neuron or muscle. The gap
is called the synapse.
Neurotransmitters are chemical messengers.
The Structure of a Typical Synapse
Classification of Neurons
Structural classification based on number of processes coming off of the cell body
We will talk about three neuron structures:
1.Multipolar
2.Bipolar
3.Unipolar
Multipolar neuron
• multiple dendrites
• single axon
• most common type
• ALL motor neurons are multipolar
Bipolar neuron• two processes coming off cell body
• one dendrite • one axon
• only found in eyes, ears & nose• Process sensory information
Unipolar neuron
• single process coming off cell body
• dendrites at one end
• axon makes up the rest of the process
• some sensory neurons in PNS are unipolar
Anatomical structure of Nerves
Fig. 14.6
Efferent Divisions
Somatic Nervous System Voluntary Stimulates skeletal
muscles Stimulates them to
contract
Autonomic Nervous System Involuntary Controls cardiac muscle of
the heart and smooth muscle of internal organs
2 Categories Sympathetic
Fight or Flight response Releases adrenaline
Parasympathetic Rest and digest response Day-in-day-out functions
Reflexes (Simple, rapid, involuntary, programmed responses to stimuli)
Somatic Reflexes Stimulation of skeletal
muscles Ex: Withdrawing hand
from something hot before you even realize it is hot
Fast because doesn’t travel to brain and back (sensory neuron spinal cord motor neuron)
Autonomic Reflexes Send involuntary stimuli
to cardiac muscle of heart and smooth muscle of internal organs
Ex: Digestion, elimination, sweating, blood pressure
Nervous System Overview
Nerve Impulses
Synapses In Detail