Anatomy Test 3 Review –
Chp 11 – Functional Organization of Nervous Tissue
(Acetylcholine, Serotonin, Dopamine, Norepinephrine, Endorphins)
Structure and Function of Brain – 1. Nervous system 2. Endocrine system
Purpose – to regulate and coordinate bodily functions and maintain homeostasis
Conscious vs unconscious mind
Function of Nervous System –
1.Maintaining homeostasis. Regulate and coordinate physiology
2.Receiving sensory input. Monitor internal and external stimuli
3.Integrating information. Brain and spinal cord process sensory input and initiate responses
4.Controlling muscles and glands
5.Establishing and maintaining mental activity. Consciousness, thinking, memory, emotion
CNS – Brain + spinal cord
PNS – All nervous tissue outside CNS [nerves to face, ganglia, nerves to upper limb, nerves to
lower limb]
Cells of nervous system are neurons- sending electrical messages from their cell bodies via axons
PNS 
Sensory receptors: ending of neurons or separate, specialized cells that detect such things as
temp, pain, touch, pressure, light, sound, odors
Nerve: bundle of axons and their sheaths that connects CNS to sensory receptors, muscles, and
glands
- Cranial nerves – originate from brain; 12 pairs
- Spinal nerves – originate from spinal cord; 31 pairs
Plexus: extensive network of axons, and sometimes neuron cell bodies, located outside CNS
2 Division of PNS – Sensory and Motor
Sensory = Afferent = transmits action potentials from receptors to CNS (processing)
Motor = Efferent = transmits action potentials from CNS to effectors (Muscles, glands)
Motor Division – Somatic and Autonomic
Somatic – from CNS to skeletal muscles
Voluntary division of motor division
Single neuron system – cell bodies are within the CNS
Synapse: junction of a nerve cell with another cell ex. Neuromuscular junction is a synapse
between a neuron and a skeletal muscle cell
Autonomic – from CNS to smooth muscle, cardiac muscle and certain glands
–Subconscious or involuntary control.
–Two neuron system: first from CNS to ganglion; second from ganglion to effector.
–Divisions of ANS
•Sympathetic. Prepares body for physical activity. Fight or Flight
•Parasympathetic. Regulates resting or vegetative functions such as digesting food or emptying
of the urinary bladder.Rest and digest
•Enteric. plexuses within the wall of the digestive tract. Can control the digestive tract
independently of the CNS, but still considered part of ANS because of the parasympathetic and
sympathetic neurons that contribute to the plexi.
Receptor – sensory NS – CNS – Motor NS – Effector
Glial cells – support and protect neurons
Neurons – receive stimuli
- Cell body – nucleus = center of info
- Dendrites – input = receiving portion of neuron
- Axons – output- terminate by branching into extensions called resynaptic terminals
Types of neurons –
Sensory/afferent – action potential towards CNS
Motor/efferent – action potential away from CNS
Interneurons – within CNS from on neuron to another
Multipolar – most neurons in CNS [ many dendrites and an axon]
Bipolar – specialized sensory for smell, sight, taste, hearing, balance [ a dendrite and an axon]
Psuedo-unipolar – single process that divides into two branches [appears to have axon and no
dendrites]
Synapse – junction between two cells
Presynaptic cell – before the synapse transmitting signal towards synapse
Postsynaptic cell – target cell receiving the signal after synapse
2 types –
Electric synapses – Gap junctions allow graded current to flow between adjacent cells
Connexons – protein tubes in cell membrane
In cardiac and many types of smooth muscle
Chemical synapses – when a neurotransmitter is used to communicate a message to an effector
–Presynaptic terminal: location where neurotransmitter is released by the action potential
–Synaptic cleft
–Postsynaptic membrane
–Synaptic vesicles: action potential causes Ca2+to enter cell that causes neurotransmitter to be
released from vesicles
–Diffusion of neurotransmitter across synapse
–Postsynaptic membrane: where Ach binds to receptor, further propagating the action potential
1. Action potential arrives at the presynaptic terminal causes voltage gated Ca2+ channels to
open
2. Ca2+ diffuse into the cell and cause synaptic vesicles to release neurotransmitter molecules
3. Neurotransmitter molecules diffuse from the presynaptic terminal across the synaptic cleft
4. Neurotransmitter molecules combine with receptor sties and cause ligand gated Na+ channels
to open. Na+ diffuse into the cell or out of the cell and cause a change in membrane potential
A few key points from the videos
•Neurotransmitters transmit signals from a nerve cell to others. Can be passed from one nerve
cell to another, from one nerve cell to a muscle cell or to a gland cell.
•NT's can have one of two effects on the post-synaptic cell: 1-Excitatory or 2-Inhibitory.
•An Excitatory effect is one where the NT induces a depolarization making the cell more likely
to generate an action potential
•An Inhibitory effect is where the NT induces a hyperpolarization making the cell less likely to
generate an action potential. It makesthem more negative (-) by increasing the stimulus required
to move the membrane potential to action potential threshold
.•Different types of NT's help regulate breathing, digestion, heartbeat and can also affect
concentration, sleep and mood.
•There are over 100 different types of NT's that have been identified
.•Some general actions:
•Acetycholine: for activating muscles
•Norepinephrine: Increases HR and Bp.
•Dopamine: deals with pleasure and rewards
•Gaba: suppresses some types of anxiety
•Serotonin: promotes the sensation of well-being and happiness
NT’s categorized by structure –
Amino Acids – Glutamate(most common excitatory NT’s), Gaba + Glycine (most common
inhibitory NT’s of the nervous system. Gaba in brain and glycine in spinal cord)
Monoamines – Indoleamines: Serotonin and Histamine; Catecholamines: Dopamine,
norepinephrine and epinephrine
Serotonin
Histamine
Chp 12 Spinal Cord and Spinal Nerve’s
31 pairs of spinal nerves
Cervical
Thoracic
Lumabar
Sacral
Cervical and Lumbar Enlargement
Conus medullaris – tapered inferior end
Cauda equina – origins of spinal nerves extending inferiorly from lumbosacral enlargement and
conus medullaris
Spinal Cord cross section –
Commissures: connections between left and right halves
Roots: spinal nerves arise as rootlets then combine to form roots
Dorsal root ganglion: collections of cells bodies of unipolar sensory neurons forming dorsal
roorts
Motor neuron cell bodies are in anterior and lateral horns of spinal cord gray matter
Reflexes –
Sensory to inter to motor
Effector organ responds with reflex
Not every reflex utilizes interneuron
Arc ---- sensory receptor detects stimulus, sensory neuron conducts action potentials through the
nerve and dorsal root to the spinal cord, sensory neyron synapses with interneuron in spinal
cord, interneuron synapses with motor neuron, motor neuron axon conducts action potentials
through ventral root and spinal nerve to an effector organ
Stretch reflex –
Muscle spindle : specialized muscle cells that respond to stretch
Golgi tendon reflex – prevents contracting muscles from applying excessive tension to tendons
- Golgi tendon organ – encapsulated nerve endings that have their end snumerous terminal
branches with small swellings associated with bundles of collagen fibers in tendon. Prevent
damage to tendons
Withdrawal reflex (flexor)
Involves sensory pain receptors
To remove body limb or part from painful stimulus
Reciprocal innervation: causes relaxation of extensor muscle when flexor muscle contracts
Crosses extensor reflex: when a withdrawal reflex is initiated in one lower limb, the crosses
extensor reflex causes extension of opposite lower limb
31 pairs of nerves
Dermatome is area of skin supplied with sensory innervation by a pair of spinal nerves
All but C1 have this
Branches of spinal nerves:
Dorsal Ramus
Ventral Ramus
Communicating Rami