Nerves are bundles of neurons surrounded by connective tissue membranes. They transmit signals through reflex arcs, which are automatically programmed responses to stimuli that do not require conscious thought. There are two types of reflexes - somatic reflexes which stimulate skeletal muscle responses and autonomic reflexes which stimulate smooth muscle responses like digestion.

1. ANATOMY
Unit 2 Notes:
Nerve
Structure &
Reflexes

2. (1) What is a Nerve?
• Nerve = Bundle of neurons.
• Nerves Are Made Of:
– Fascicles
– Neurons
– Epineurium
– Perineurium
– Endoneurium

4. (2) Nerve Membranes
• Endoneurium:
The membrane which encases a single
neuron.
• Perineurium:
The membrane which binds together a
bundle of neurons (also called a fascicle).
• Epineurium:
The membrane which binds together a
bundle of fascicles.

5. (3) Reflexes
• Automatically programmed response to a
specific stimulus.
• All reflexes are involuntary, however do not
need to travel through the individual
nervous system divisions.
• Reflex Arc Path:
–Stimulus triggers nerve impulse.
–Impulse sent to CNS, but at spinal cord
routes directly back out to effector organ.

8. (4) Types of Reflexes
• Somatic:
A reflex which stimulates a response in the
skeletal muscle.
– Example: Retracting your arm from a hot
stove.
• Autonomic:
A reflex which stimulates a response in smooth
muscle.
– Example: Your stomach releasing gastric
juice and churning once food is dropped in.