Synapse - junction between two communicating
neurons
Nerve pathway - nerve impulse travels from neuron to neuron
Synaptic Transmission
Dendrite --> cell body --> along axon --> synapse (gap)
To complete the signal, a NEUROTRANSMITTER is released at the gap to signal the next neuron
Excitatory - increase membrane permeability,
increases chance for threshold to be achieved
Inhibitory - decrease membrane permeability, decrease chance for threshold to
be achieved
Types of Neurotransmitters
Acetylcholine - stimulates muscle
contraction
Monoamines - Norepinephrine & Dopamine (sense of feeling good, low levels
= depression)
Serotonin (sleepiness)
Endorphins (reduce pain, inhibit receptors)
Synapses are highly susceptible to drugs and fatigue
|
9.8 Impulse Processing
Neuronal pool - groups of neurons that make hundreds of synaptic connections and work together to perform a common function
9.9 Types of Nerves
Sensory Nerves - conduct impulses
into the brain or spinal cord
Motor Nerves - carry impulses to muscles of glands
Mixed Nerves - contain both sensory and motor nerves
9.10 Nerve Pathways
Reflex arc - simple pathway, includes only a few neurons (reflexes)
Reflex Behavior - automatic, subconscious
responses to stimulu
Knee-jerk reflex - stimulus knee ' sensory nerve ' spinal cord ' motor nerve
Withdrawal reflex - occurs when you touch something painful
9.11 Meninges = membranes located
between bone and soft tissues of the nervous system
Dura mater = outmost layer, blood
vessels, nerves
Arachnoid mater = no blood vessels, located between
Pia mater = contains many nerves and blood vessels to nourish cells of brain
and spinal cord
*Cerebrospinal fluid = between arachnoid and pia maters
9.12 Spinal Cord
- nerve column, passes from brain down through the vertebral canal
- has 31 segments, each with a pair of spinal nerves
Cervical enlargement = supplies
nerves to upper limbs (neck)
Lumbar enlargement = supplies nerves to the lower limbs (lower back)
FUNCTION: conducting nerve impulses, serves as a center for spinal reflexes
Ascending tracts = carry sensory
info to the brain
Descending tracts = carry motor impulses from the brain to the muscles
Spinal reflexes - reflex arcs pass through the spinal cord
