Peripheral nervous system

What does the peripheral nervous system consist of?

All nerves projecting from the brain and spinal cord

What are nerves?

Bundles of neurons

What are sensory nerves?

Bundles of dendrites from sensory neurons

What are motor nerves?

Bundles of axons from motor neurons

What are mixed nerves?

Dendrites of sensory neurons and axons of motor neurons running together

Bundles of nerves

Where are neuron cell bodies found?

Only in the brain, spinal cord, and ganglia

What is a ganglion?

A collection of cell bodies from many neurons in the PNS

What does a ganglion appear as?

An enlarged portion of the nerve

What are cranial nerves?

Nerves that go to and from the brain

How many cranial nerves are there?

12

Are cranial nerves sensory, motor, or mixed?

They can be just sensory, just motor, or mixed

What are spinal nerves?

Nerves that go to and from the spinal cord

How many spinal nerves are there?

Are spinal nerves sensory, motor, or mixed?

Just mixed

What does the somatic nervous system contain?

Nerves that control skeletal muscles, joints, and exterior sense organs like skin

What does the somatic nervous system do?

Receives and acts on external stimuli (voluntary control)

What are the two divisions of the peripheral nervous system?

Somatic and autonomic

What are the two divisions of the autonomic nervous system?

Sympathetic and parasympathetic

What does the autonomic nervous system contain?

Nerves that control the smooth muscles of the internal organs and the glands

What are examples of smooth muscles working in internal organs and glands?

Peristalsis or vasoconstriction in blood vessels

What does autonomic mean?

Automatic

What does the autonomic nervous system do?

Controls things without the need for conscious thought (involuntary things)

What do autonomic motor signals use to work?

Two motor neurons that synapse at a ganglion

The first neuron has a cell body within the CNS

The second neuron has a cell body within the ganglion

In an autonomic motor signal, what is the first neuron called?

The preganglionic fibre

In an autonomic motor signal, what is the second neuron called?

The postganglionic fibre

What is the sympathetic nervous system used for?

Emergency situations/acton (fight or flight)

For the sympathetic nervous system, where is the origin of nerves?

The spine, thoracic and lumbar section in particular

How does the sympathetic nervous system work?

Sudden simultaneous release of the neurotransmitter (released by a neuron) norepinephrine (also called noradrenaline), from all the sympathetic neurons (as in times of fright) has a large effect across the body

What does the release of norepinephrine/noradrenaline cause?

The release of the hormone (released by an endocrine gland) epinephrine/adrenaline from the adrenal medulla (interior of the adrenal glands) located on top of the kidneys

What does the norepinephrine/noradrenaline and epinephrine/adrenaline initiate and sustain?

The fight or flight response

How does the fight or flight response prepare your body to respond to danger (5 ways)?

Increases the heart rate so that more blood is supplied to the body more quickly

Wider air passageways so that more air can be exchanged with each breath

Sudden contraction of some muscles to tense the body up for action

Increased blood flow to skeletal muscles so they are more able to act

Decreased digestive activity so less energy is spent on digestion

How does the sudden contraction of muscles prepare the body for action?

The contraction of the diaphragm causes a person to gasp/inhale suddenly

The iris of the eye contracts, widening/dilating the pupil to maximize visual alertness

What is the parasympathetic nervous system?

Normal activity / rest and digest

What does the parasympathetic nervous system release?

The neurotransmitter acetylocholine

Where is the origin of the parasympathetic nervous system?

Spine, cranial and sacral

What does the release of acetylcholine cause?

Decreased heart rate

Constricted air passageways

Muscles stop contracting (pupils close/constrict)

Energy goes to the digestive system

Decreased blood flow to skeletal muscles

What are reflexes?

Automatic, involuntary responses to changes occurring inside or outside the body

What are the two types of reflex arcs?

The autonomic reflex arc and somatic reflex arc

What does the autonomic reflex arc affect?

Inner organs

What does the somatic reflex arc affect?

Muscles

What does the reflex arc allow?

It allows us to react to internal and external stimuli

What is the main functional unit of the nervous system?

The reflex arc

What are examples of the reflex arc?

The patellar reflex, blinking the eye, moving your hand away from a hot object

In the reflex arc, why does the brain not have to be involved?

Time

If it were, by the time the impulse travelled to the brain, the brain figured out what was happening, and sent a response to the body, serious damage might occur, so the body evolved a method of bypassing the brain

What are the stages of the reflex arc?

Receptor (sensory neuron) is stimulated and generates nerve impulses/formulates a message

Sensory neuron takes the message back the CNS/spinal cord

Interneuron passes the message to a motor neuron

Motor neuron takes the message away from the CNS to the effector (muscle/organ)

The muscle/organ receives the nerve impulse (message) and reacts

When does the brain find out what happens during the reflex arc and when do you feel pain?

After

You do not feel pain until your brain receives the information (via the ascending tract) and interprets it

Which direction does the impulse of a reflex arc travel in?

Clockwise

What are the two paths an impulse can follow at an interneuron?

The reflex arc pathway back to the effector muscle causing motion

The ascending tract to the brain to sense pain

What is the somatic nervous system responsible for?

Reflexive movement of muscles (not consciously controlled), as well as conscious controlled movement of the muscle