Transcript Neurons & the Nervous System

Neurons & the Nervous System
Chapter 2: The Brain and
Behavior
Today’s Goal  You will be able to….
• Identify the parts of a neuron and their functions in
creating & sending neural messages.
Parts of the Neuron
• Neurons: nerve cells
• Dendrites: branch-like end of neuron which receives
messages
• Cell body (soma): contains nucleus
• Axon: long tail-like end of neuron which transmits
(sends) messages
• Myelin: fatty substance that speeds up
transmission of impulse
• Axon terminals/Terminal buttons: contain
neurotransmitters, release them during
neural impulse
Types of Neurons
• Sensory neurons: send
messages from sensory
receptors to the spinal cord &
brain
• Motor neurons: relay messages
from brain & spinal cord to
muscles & glands
• Interneurons: transmits neural
stimulus between sensory &
motor neurons (found only in
Central nervous system)
Simple Reflex Arc
• Communication goes directly from interneurons
in spinal cord to motor neurons to move
(reflexively) at the same time the info is going to
the brain to be perceived
The Nervous
System
Peripheral
Somatic
Central
Autonomic
Sympathetic
Parasympathetic
Central v. Peripheral
• Central contains brain &
spinal cord
• Peripheral – sensory &
motor neurons that
transmit messages
between brain and
muscles & glands
Autonomic v. Somatic
• Somatic – voluntary - controls purposeful
body movements
• Autonomic – involuntary – automatic
activities
– heartbeat, respiration, digestion, dilation of
pupils, etc.
Sympathetic v. Parasympathetic
• Sympathetic = “Fight-orflight” response
– Uses energy reserves to
cope with stress or
emergency
– Adrenaline!
• Parasympathetic = “Rest
and digest”
– Conserves & builds up
stored energy reserves
Today’s Goal  You will be able to….
• Describe how neurons communicate to send
messages in the brain and body
The Synapse
• Synapse (synaptic cleft): gap between dendrites of one
neuron and axon of another
• Receptor sites: parts of dendrite which receive
neurotransmitters
• Neurotransmitters:
chemical substances
involved in sending
neural impulses
Neural Impulse: electrochemical firing of
a nerve cell
• Resting potential: electric
potential when neuron not
firing (-70 millivolts)
• Threshold: level of
stimulation required to
trigger a neural impulse
(excitatory – inhibitory =
threshold)
Neural Impulse: electrochemical firing of
a nerve cell
• Action potential: when a
neuron fires the impulse
(sends the message)
• Refractory period: phase
after firing an impulse,
neuron will not fire
• All-or-none principle:
neuron will fire or not fire,
no in-between
Resting potential
Synapses
• Excitatory neurotransmission: increases the
likelihood that postsynaptic neuron will fire
• Inhibitory neurotransmission: decreases
likelihood that postsynaptic neuron will fire
Today’s Goal  You will be
able to…
• Discuss how the major
neurotransmitters affect the body
and one’s behavior
Substances that Affect Neurotransmitters
• Agonist: similar to the NT, mimics its effects
• Antagonist: inhibits the release of NT by sending
neuron, or blocks receptor site for NT on
receiving neuron
Neurotransmitters
• Acetylcholine (ACh)
EXCITATORY (sometimes inhibitory)
Memory, muscle contractions, learning
Malfunctions: Alzheimer’s Disease
Neurotransmitters
• Dopamine (DA)
Reward/pleasure, movement, attention
Malfunctions: Too little 
Parkinson’s, Too much 
Schizophrenia
• Serotonin
– Mood regulation, sleep and
appetite regulation,
concentration, learning
– Imbalance  depression
Neurotransmitters
• Norepinephrine
– Involved in autonomic nervous system (sympathetic)
arousal
– Imbalances: Depression, seizures
• GABA
– Function: Reduce anxiety, relax for sleep
Imbalance: Anxiety disorders, tremors, insomnia
• Endorphins  pain control