Download neuron

Starting small: The Neuron
• neuron: a nerve cell;
receives signals from other
neurons or sensory organs,
processes these signals, and
sends signals to other
neurons, muscles, or bodily
organs
– the basic unit of the nervous
system
The Neuron
• 3 types of neurons:
– 1. sensory neurons: respond to input from sensory
organs (skin, eyes, etc.)
– 2. motor neurons: send signals to muscles to control
movement
– 3. interneurons: connect the sensory neurons and
motor neurons
• most of the neurons in the brain = interneurons
• average human brain  100 billion neurons
Structure of the Neuron
Structure of the Neuron
• cell body (soma): the central part of the neuron, contains
the nucleus
– regulates cell functioning
• dendrites: the branching part of the neuron that receives
messages from other neurons and relays them to the cell
body
Structure of the Neuron
• axon: the long, cable-like extension that delivers messages to other
neurons
• myelin sheath: layer of fatty tissue that insulates the axon and helps
speed up message transmission
– multiple sclerosis: deterioration of myelin leads to slowed
communication with muscles and impaired sensation in limbs
• knobs: structure at the end of one of the axon’s branches that
releases chemicals into the space between neurons, when the neuron
is fired
From Neuron to Neuron
• ≈100 billion neurons in a human brain,
connected to an average of 10,000 others;
some up to 100,000
• synapse: the place where an axon of one
neuron meets with the dendrite/cell body of
another neuron
From Neuron to Neuron
From Neuron to Neuron
• neurotransmitters:
a chemical that
sends signals from
one neuron to
another over the
synapse
From Neuron to Neuron
• Neurotransmitters are
stored in vesicles in
the knobs, and bind to
receptors on the cell
membrane of the next
neuron.
– Each receptor can
only bind with one
kind of
neurotransmitter.
(Some) Neurotransmitters
Neurotransmitter
Function
Examples of
malfunctions
Acetylcholine
(ACh)
Enables muscle action,
learning & memory
Alzheimer’s disease 
less ACh production
Dopamine
Influences movement,
learning, attention, &
emotion
Excess 
schizophrenia
Undersupply 
Parkinson’s disease
Serotonin
Affects mood, hunger,
sleep, and arousal
Undersupply 
depression
Norepinephrine
Helps control alertness &
arousal
Undersupply 
depressed mood
Glutamate
Excitatory neurotransmitter
involved in memory
Excess 
overstimulation of
brain, seizures
The Nervous System
The Nervous System
Central Nervous System (CNS)
Brain
Peripheral Nervous System (PNS)
Spinal Cord
•
Motor Neurons
Somatic Nervous System
voluntary movements via
skeletal muscles
Sympathetic
- “Fight-or-Flight” responses
•
Sensory Neurons
Autonomic Nervous System
organs, smooth muscles
Parasympathetic
- maintenance
The Nervous System
• Made up of the
1. central nervous system
and the
2. peripheral nervous system
The Nervous System
The Central Nervous
- brain and spinal cord
• Peripheral Nervous System: links
central nervous system to organs
–comprised of the somatic nervous system
and the autonomic nervous system
(sympathetic and parasympatheic nerves)
CNS
PNS
Motor division
Sensory division
Sympathetic
division
Parasympathetic
division
Human Anatomy and Physiology, 7e
by Elaine Marieb & Katja Hoehn
Autonomic
nervous
system
Somatic
nervous
system
Copyright © 2007 Pearson Education, Inc.,
publishing as Benjamin Cummings.