Nervous System Structure Flashcards
Somatic Nervous System
Composed of PNS and CNS
- Supply sensory and motor to entire body except viscera, smooth mm, and glands
SENSORY - carries conscious sensations of pain, pressure, temperature and pressure
- Sensations reach conscious level
-Innervates only skeletal m.
o Exceptions: viscera, smooth m. and glands
o Voluntary and reflexive movements via muscle contraction
Autonomic Nervous System (2 divisions)
1) Sympathetic
2) Parasympathetic
Central Nervous System (CNS)
- Consists of brain and spinal cord
- Integrates and coordinates
- Carries out higher mental functions e.g. thinking and learning
Peripheral Nervous System (PNS)
o Everything that isn’t CNS
o Conducts impulses to or away from CNS
o Somatic Nervous System (SNS)
o Autonomic Nervous System (ANS)
Nerve Fiber
Consists of an axon, its neurolemma and surrounding connective.
Ganglion
A collection of neuron cell bodies outside CNS
There are both motor (autonomic) and sensory ganglia
Afferent (sensory) fibers
Convey neural impulses to CNS from sense organs
Convey neural impulses from sensory receptors in various parts of body
Efferent (motor) fibers
Convey Neural impulses from CNS to effector organs
Cranial Nerves
Exit cranial cavity via foramina in cranium
AKA Spinal accessory nerve or CN XI
Spinal (segmental) Nerves
Spinal no. Arise in bilateral pairs from a specific segment of spinal cord
Exit vertebral column via intervertebral foramina
Ventral (anterior) nerve root
Consists of motor fibers from cell bodies in anterior horn of spinal cord to effector organs located peripherally
Dorsal (posterior) nerve root
Consist of sensory fibers from cell bodies in dorsal root ganglion (DRG)
DRG extend peripherally to sensory endings and centrally to dorsal hot of spinal cord
Dorsal Primary Ramus
Motor sensory fibers
Gives off medial and lateral cutaneous branches
Supply synovial joints of vertebral column, deep mm. Of back and overlying skin in a segmental pattern
Ventral primary ramus (VPR)
Motor and sensory fibers
Supplies anterior and lateral regions of trunk, upper and lower limbs
Dermatome
unilateral area of skin innercate do by sensory fibers of a single spinal n
Paravertebral ganglia
Linked to form sympathetic trunks (Chains) on each side of vertebral column
Functions of Divisions of ANS
Catabolic (energy-expanding) system
Heart- increase heart rate and force of contraction
Bronchi-dilate
Pupils-dilate
Digestive tract-inhibits peristalsis/decrease blood flow
Skin vessels-constrict
Skeletal m. Vessels-dilate
Sweat glands-increase perspiration
Functions of Parasypathetic
Anabolic (energy-conserving) system
Heart-decrease rate and force of contraction
Bronchi-constrict
Pupils-constrict
Digestive tract-increased peristalsis/blood flow
Nerve Fiber consists of:
- Axon
- Neurolemma
- Surrounding connective tissue
2 forms of Neurolemma
Myelinated
Unmyelinated
Never consists of:
- Bundle of nerve fibers outside CNS
- Connective tissue coverings that bind nerve fibers and fascicles together
- Blood vessels that nourish nerve fibers and coverings
Ganglion
- A collection of neuron cell bodies outside CNS
- Motor (autonomic) and sensory ganglia
2 Types of Nerves
- AFFERENT (sensory) fibers
- –> Convey neural impulse TO CNS from sense organs (ex. Eyes)
- –> Convey neural impulse from sensory receptors in various parts of body (skin)
EFFERENT (motor) fibers
- –> Convey neural impulse FROM CNS to effector organs (ex. Muscles and glands)
- –> Are either cranial nerves, spinal, or derivatives of them
Cranial Nerves Carry 4 types of Fibers:
- Somatic afferent fibers
- Somatic efferent fibers
- Visceral afferent fibers
- Visceral efferent fibers
Spinal Nerves are also known as:
Segmental Nerves
How do Spinal nerves exit the vertebral column?
Via the intervertebral foramina
How many pairs of spinal nerves are there?
31
List 5 regions of spinal nerves and how many pairs there are in each region?
Cervical (C) - 8 Thoracic (T) - 12 Lumbar (L) - 5 Sacral (S) - 5 Coccygeal (Cox) - 1
How do the spinal (segmental) nerves arise from the spinal cord?
As rootless
Rootlets converge to form what?
2 nerve roots
1) Ventral (Anterior) nerve root
2) Dorsal (posterior) nerve root
Mixed spinal nerve divers into 2 rami called what?
1) Dorsal primary ramus
2) Ventral primary ramus
Do dorsal primary rami form major plexuses?
No
Do ventral primary rami for nerve plexuses?
Yes - majority of VPR merge with one another to form somatic nerve plexuses
4 Somatic nerve plexuses
Cervical (C1-4)
Brachial (C5-T1; sometimes C4-T2)
Lumbar (L1-4; sometimes T12)
Sacral plexus (L4-S4
**T2-12 do not usual join a plexus and remain segmental
Dermatomes are a
Unilateral area of skin inner ate do by sensory fibers of a single spinal nerve
Cutaneous nerves carry:
Sensory info from skin; motor innervation to glands and smooth m
General sensory (somatic afferent) fibers transmit:
Sensations from body to CNS
Ex. Sensations from skin (pain, pressure, temperature)
Ex. Sensations from mm, tendons, joints
General motor (somatic efferent) fibers transmit:
Impulses to skeletal mm (voluntary)
Visceral sensory (afferent) fibers transmit:
Sensations from hollow organs or blood vessels to CNS
- Pain or subconscious visceral reflex sensations (dissension, blood gas and blood pressure)
Visceral motor fibers (visceral efferent) transmit
Impulses to smooth (involuntary) m and glandular tissue
- has pre- and postsynaptic fibers
ANS motor fibers are accompanied by what?
- Visceral afferent fibers (not part of ANS, but hitch a ride
ANS consists of what type of motor fibers?
Visceral efferent (from CNS TO destination)
Sympathetic (Thoracolumbar) division of Autonomic Nervous System cell bodies are located between which vertebral levels?
T1-L2 or L3
