The Synapse and Reflexes

Synapse: Is a junction where a axon interacts with another neuron

Presynaptic Terminal: End of the axon

Postsynaptic Membrane: Membrane of the dendrite

Synaptic Cleft: Space between the presynaptic membrane and postsynaptic membrane

Synaptic vesicles: Stores chemical neurotransmitters

Structure of a Synapses

Excitatory - increase membrane permeability, increases chance for threshold to be achieved to trigger an action potential

Inhibitory - decrease membrane permeability, decrease chance for threshold to be achieved to trigger an action potential

Neurotransmitters

Acetylcholine ACh - stimulates muscle contraction

Norepinephrine & Dopamine (sense of feeling good, low levels = probable cause to depression)

Serotonin (sleepiness)Endorphins (reduce pain, inhibit receptors)

Types of Neurotransmitters

Reflex: An involuntary reaction in response to a stimulus

Reflex Arch: Pathway in which a reflex occurs.

Reflexes

Sensory Nerves - conduct impulses into the brain or spinal cord

Motor Nerves - carry impulses to muscles of glands from the brain and spinal cord

Mixed Nerves - contain both sensory and motor nerves

Types of Nerves

5 steps of Reflex Arch1. Sensory Receptor 2. Afferent neuron 3. interneuron 4. Motor neuron 5. Effector organ

Reflex Arch Pathway

Reflex arc - only includes a few neuronsReflex Behavior – automatic and

subconscious responsesStretch or Knee-jerk reflex – Muscles

contract when applied force it put on them (patellar reflex)

Withdrawal reflex - avoidance of painful stimuli

Nerve Pathways

Converging Pathways: More than one neuron synapses converge on the same neuron. (more than one neuronal pathway)

Diverging Pathways: The axon from one neuron divides or diverges with one or more neurons. (one neuronal pathways can diverge into multiple pathways)

Neuronal Pathways