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The Nervous System
and the Brain
Information in this presentation is taken from UCCP content
The Nervous System
Our nervous system has three primary functions:
1. to gather and process information
2. produce responses to stimuli
3. coordinate the working of different cells
It is divided into two parts: central nervous
system (brain and spinal cord) and the peripheral
nervous system.
Peripheral Nervous System
The peripheral nervous system consists of neurons that transmit
messages to and from the central nervous system.
There are two types of neurons in this system: sensory neurons
and motor neurons.
Sensory, or afferent, neurons receive the information from
muscles and glands and transmit the message to the brain and
spinal cord.
Motor, or efferent, neurons receive messages from the brain and
spinal cord and transmit the information to muscles and glands.
An easy way to remember what afferent and efferent neurons do is
to remember the mnemonic, SAME. Sensory neurons (S) are
Afferent neurons (A); Motor neurons are Efferent neurons (E).
Peripheral Nervous System
There are two divisions of the peripheral nervous system: the
somatic nervous system and the autonomic nervous system.
The somatic nervous system connects the CNS to sensory
receptors and muscles. Neurons in the somatic nervous system
transmit messages about sights, sounds, smell, temperature, and
body position to the CNS. It also transmits information from
the brain to produce purposeful motor movements.
The autonomic nervous system is “automatic”. It controls and
regulates the glands and muscle of internal organs. For example,
it controls activities such as heart rate, respiration (breathing),
digestion, and pupil dilation. These activities occur
automatically.
Autonomic Nervous System
There are two branches of the autonomic nervous system:
sympathetic and parasympathetic.
The sympathetic nervous system is most active during processes
that involve spending the body’s energy from stored reserves. It
prepares the body to respond in times of danger or high
emotion. Basically, it is arousing the body to take action.
(example: if you see a mean dog running towards you, your
body will prepare you to expend your energy and RUN!)
The parasympathetic nervous system is most active during
processes that replenish reserves of energy. It quiets the body
and lowers its level of arousal. It is most active after high
emotional states. It works to keep your heart rate and breathing
at moderate levels.
The Nervous System
The somatic and autonomic nervous systems work
together to coordinate the inner world of the body with
what is going on in the outside world. For example, if
a large dog growls and lunges at you, your autonomic
nervous system (sympathetic) increases your blood
pressure and heart rate and prepares you to react. At
the same time, the somatic nervous system is sending
messages to your leg muscles allowing you to run.
Sometimes people’s sympathetic nervous system
overreacts. In the absence of external threats, their
bodies still respond as if they were faced with danger,
such as in anxiety or panic attacks.
The Central Nervous System
The central nervous system consists of the brain
and spinal cord.
Its primary functions are to:
1) receive, process, interpret and store sensory
input and
2) initiate motor outputs
The Central Nervous System
The spinal cord is like an information highway. It is a
column of nerves that transmits messages (1) from
sensory receptors to the brain and (2) from the brain to
muscles and glands. The most basic pattern of neural
responses, however, does not even include the brain.
Spinal reflexes are unlearned, automatic responses to
stimuli that typically include only two neurons, a
sensory neuron and a motor neuron. Sometimes
interneurons will transmit the neural impulse from the
sensory neuron through the spinal cord to the motor
neuron.
The Central Nervous System
The pain reflex illustrates this neural pathway. Imagine if your right
hand touches the burner on the stove. The sensory neurons in
your hand detects the pain and instantly fires off a message to
your spinal cord. When the message reaches your spinal cord it
connects with an interneuron that in turn activates a motor
neuron. The motor neuron sends a message to cells in your arm
muscles that are capable of muscle movement. Muscle cells in
your right arm contract, causing you to lift your right hand off
the stove. If this happened, would it require any brain activity or
thinking on your part?
However, the spinal cord will also send a message to the brain
notifying it about what you have done. After you withdraw your
hand, you will most likely feel the pain and shout, “Ouch!”
The Brain
The brain consists of three major regions:
1) The hindbrain
2) The midbrain
3) The forebrain
Our forebrain is most important in those aspects
of life that are most relevant to psychology
(e.g. perception, memory, thinking and social
behavior).
The Hindbrain
The hindbrain controls some basic functions such as breathing and
heart rate. It is also important in attention, sleep, alertness,
body movement, and balance. The primary structures of the
hindbrain are the following:
1)
The cerebellum coordinates motor behavior, muscle
coordination, and balance.
2)
The medulla regulates unconscious functions such as
breathing and circulation.
3)
The pons connects the brain stem to the cerebellum and is
involved in sleep and arousal as well as transmits information
about body movement.
4)
The reticular formation controls arousal and attention.
The Midbrain
The midbrain plays a role in vision, hearing, motor
movements, attention, and sleep. For our
purposes, the midbrain is a conduction and
switch center that serves as a link between the
hindbrain and the forebrain.
The Forebrain
The primary structures of the forebrain are:
1)
Thalamus – relay station that receives and relays
sensory information to the appropriate area of the
cerebral cortex (e.g. sensory info. from the eyes)
2)
Hypothalamus – regulates autonomic nervous system,
motivation and emotion. It also controls eating,
drinking, sexual behaviors and aggression.
3)
Limbic System – includes the amygdala, hippocampus
and parts of the hypothalamus. The amygdala is
involved in aggression and fear responses. The
hippocampus is important in learning and memory.