Download Notes - The Nervous System

The Nervous System
Functions of the Nervous System
• The nervous system is the body’s command
system.
– Receives information about what is happening
both inside and outside your body.
– Stimuli
– Directs that way in which your body needs to
respond to this information.
– Response
– Helps the body to maintain homeostasis.
Organization of the Nervous System
• Made up of nervous tissue
• Has two divisions:
– Central nervous system (CNS)
– Peripheral nervous system (PNS)
• Main organs:
– Brain
– Spinal cord
– Sensory organs; eyes, ears, nose, tongue, and skin
Nervous Tissue
• Made up of cells called Neurons, nerve cell.
– Carry information through your nervous system.
Dendrites
Cell Body
Nucleus
Axon
Axon
Terminals
Synapse
Characteristics of a Neuron
• Parts of the Neuron:
– Dendrites
• Carry impulses toward the cell body
– Cell body
• Contains the nucleus
• Controls all the activities of the cell
– Axon
Nerve Fibers – a
bundle of nerve
fibers – nerve.
• Carry impulses away from the cell body
– Axon Terminal
• Ends of an axon
• Pass a message on to the neighboring neuron’s dendrites
– Synapse
• Space separating the axon terminal of one neuron and the
dendrites of the neighboring neurons.
Path of a Nerve Impulse
• Nerve Impulse – the message being carried
throughout the body by nerves.
– ONLY travel in one direction
– Travel as fast as 120 m/sec
• Carried as both electrical and chemical messages
– Messages come in from different stimuli and trigger
electrical impulses.
– At the end of the axon it is changed into a chemical
message so it can cross over the synapse –
neurotransmitters.
Nerve Impulse
Synapse
Impulses come in as electrical signals
Changed to chemical
Signals to cross
over the synapse
Dendrites
Cell Body
Nucleus
Axon
Axon
Terminals
Synapse
Types of Neurons
1. Sensory Neuron – picks up stimuli from the internal
and external environments.
– Location where the stimuli is received - Receptor.
• Eyes, ears, nose, mouth, skin
2. Interneurons – carry nerve impulses from one
neuron to another.
– The brain and spinal cord interpret messages and
determine appropriate reactions.
3. Motor Neuron – Send an impulse to the muscle
resulting in a response to the stimuli.
– Muscle tissue responds by contracting – Effector
1. Receptors in your ear hear the phone.
–
Interneuron
The ear is a sensory organ.
2. Receptors trigger nerve impulses in sensory
neurons.
3. Nerve impulses pass to interneurons in the
brain.
4. The interneurons interpret the nerve
impulses and decide on a response, you
should answer the phone.
5. Impulses travel along motor neurons to the
muscles.
6. Muscles in the arm carry out the response
and you reach to pick up the phone.
Is this an example of an automatic response that
occurred rapidly without conscious control?
NO
Why?
Sensory
Neuron
Motor
Neuron
The brain was involved in
creating a response – not automatic
and with conscious control
Central Nervous System
• Made up of the brain
and spinal cord.
• Forms the largest part
of the nervous system.
• Responsible for
communication,
memory and thought.
Brain
Spinal
Cord
Peripheral Nervous System
• Connects the brain and
spinal cord to the rest of the
body.
• Made up of 43 nerve pairs:
– 12 pairs of cranial nerves
– 31 pairs of spinal nerves
• 2 divisions:
– Somatic
• Controls voluntary actions
– jogging
– Autonomic
• Controls involuntary actions
– Breathing & digestion
Cranial
Nerves
Spinal
Nerves
BrainPop – Nervous System
Reflexes
• An automatic response that occurs very
rapidly and without conscious control.
– Skeletal muscles contract with the involvement of
the spinal cord only, not the brain.
Reflex
Receptor
Interneuron
Stimuli
Motor
Neuron
Sensory
Neuron
Muscle Contracts - effector