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 receptor 2. Sensory neuron 3. Interneuron 4. Motor neuron 5. Effector

The Action Potential

The Synapse Terminal Axon

Neurotransmitter substances can be either excitatory or inhibitory. 1. excitatory neurotransmitters – cause the movement of Ca 2+ 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: Neurotransmitt er EnzymeFunction of Neurotransmitter Acetylcholine Cholinestera se 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-epinephrineRegulates the stress “fight or flight” response GABAInhibitory 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…”)