The Neuron

Some neurons contain the following additional parts:

• Schwann cells- a special kind of glial cell that produces a myelin sheath

• myelin sheath-white fatty covering that insulates the axon

• nodes of Ranvier-gaps in the myelin sheath

5 Components of a Reflex Arc:

1. Sensory receptor2. Sensory neuron3. Interneuron4. Motor neuron5. Effector

The Action Potential

The Synapse

Terminal Axon

• Neurotransmitter substances can be either excitatory or inhibitory.

1. excitatory neurotransmitters – cause the movement of Ca2+ ions into the cell or the opening of Na+ channels to cause depolarization

2. inhibitory neurotransmitters –block Na+ channels and opening K+ channels or move Cl- ions into the neuron to cause hyper-polarization

-inhibits action potentials

-may require more than one neuron to release neurotransmitters

Some of the more common neurotransmitters (and their enzymes) include:

Neurotransmitter

Enzyme Function of Neurotransmitter

Acetylcholine Cholinesterase

Involved with muscle contraction of the skeletal muscles

Dopamine Monoamine oxidase enzyme

Responsible for voluntary movement and emotions of pleasure

Serotonin Monoamine oxidase enzyme

Regulates temperature, sensory perception, sleep and involved in mood stabilization and control

Nor-epinephrine Regulates the stress “fight or flight” response

GABA Inhibitory action of motor behavior

The Brain

The PNS is subdivided into two major parts:

1. The Somatic Nervous System

-contains all the nerves that serve the muscular-skeletal system and the sensory organs.

-conscious and deliberate.

2. The Autonomic Nervous System

-contains all the nerves that serve the internal organs.

-unconscious and automatic.

-made of two parts:

A. Sympathetic nervous system

-responsible for the fight or flight response

-ex) dilation of the pupils, increased heart rate, increased breathing rate, slowed digestion, enhanced performance, increase in blood sugar

Internal Structures of the Eye

The Eye

The Ear-mechanoreceptor(“…all the better to hear you with my dear…”)