Anatomy Practical Week 4

central nervous system (CNS)

division of the nervous system that contains the brain and spinal cord

peripheral nervous system (PNS)

division of the nervous system that contains the spinal nerves, the dorsal root ganglia, the somatic nerves, and the cranial nerves

• can be broken down into 2 division: sensory and motor

sensory

afferent

part of the peripheral nervous system

motor

efferent

part of the peripheral nervous system

sensory or afferent division

division of the PNS that conducts impulses from the body to the CNS

motor or efferent division

division of the PNS that conducts impulses from the CNS to the body

two

the motor division has ___ subdivision: somatic nervous system and autonomic nervous system

somatic nervous system

the subdivision of the motor division that takes impulses from the CNS and innervates muscles - under conscious control

autonomic nervous system

the subdivision of the motor division that innervates glands, smooth muscle, cardiac muscles and organs- usually not under conscious control

neuron

an impulse conducting cell that contains an axon, dendrite, and a neuron cell body

synapse

a neuron that picks up a stimuli in your toes continues as a single cell up your leg and thigh to ____ with other neurons in the lower back

meter

neurons are often over a _____ long and carry these stimuli for a long distance

receptive

the ____ end of the neuron is the dendrites or the neuron cell body

axon

the _____ carries the stimuli along long strands of neurofibrils that are wrapped in myelin sheaths

sensory neurons (afferent)

conducts impulses to the CNS from the extreminties

motor neurons (efferent)

coducts impulses away from the CNS

multipolar neuron

consists of several dendrites, a single neuron cell body and a single axon

bipolar neuron

the neuron cell body has 2 poles. dendrites receive info and conduct it to one pole of the neuron cell body. at the other pole, an axon leaves the neuron cell body and transmits the impulse away from the cell body.

pseudo-unipolar neuron

a cell body has a single process attached to it. It has no dendrites. The neuron cell body sends impulses to the axon which transmits that info from the cell body

synapse

• the space between neurons

• neurons are not attached to each other

• they communicate by sending neurotransmitters across the short spaces between them

Glial Cells

• non-neuron cells in the CNS and PNS that do not produce electrical impulses

• they are referred to as the “glue”

• the common glial cell of the PNS is the SCHWANN CELL

• these glial cells wrap around the axon, leaving thin regions between successive cells called NODES OR RANVIER

• the wrapped portion between the nodes of ranvier becomes the MYELIN SHEATH, which is formed by the Schwann cells

Dorsal (posterior) Horns

receive sensory information from the somatic nerve

Ventral (anterior) Horns

send motor signals to the spinal nerves

Lateral Horn

only visible in some areas of the spinal cord

spinal cord

the ___ is covered in meninges just like the brain:

inner layer- pia mater

middle layer- arachnoid mater

outer layer- dura mater

both

the brain and the spinal cord _____ consist of gray and white mater

• in the brain, the gray matter is the outer layer and the white matter is the inner layer

• in the spinal cord, the gray matter is the inner layer and the white matter is the outer layer

31

there are ____ pairs of spinal nerves

mixed

the spinal nerves are ______ nerves carrying both sensory and motor information

origin

the spinal nerves are named according to their region of ______

cervical nerves

• C1-C8

• mostly innervate the head and neck

Phrenic nerve

a cervical nerve that runs to the diaphragm and is responsible for contraction in breathing

thoracic nerves

• T1-T12

• mostly innervate the ribs, muscles and other structures of the thoracic wall

• notice that most of these nerves do not belong to a plexus

lumbar nerves

• L1-L5

• mostly innervate lower limbs

sacral nerve

• S1-S5

• mostly innervate lower limbs

coccygeal nerve; plexuses

• Co

• some of these nerves exit the spinal cord and branch out to parts of the body individually, but the ventral rami form a branching network with other spinal nerves. these networks are called ______

cervical plexus

• C1-C4

• mostly innervates the muscles and skin of the neck and the ears

brachial plexus

• C5-T1

• mostly innervates the upper extremities

• axillary nerve and radial nerve

axillary nerve

major nerve of the brachial plexus that innervates the upper shoulder

radial nerve

major nerve of the brachial plexus that innervates the extensions of the hand

Lumbosacral Plexus

• sometimes the lumbar plexus and sacral plexus are combined and called ______

• note: both the lumbar and sacral plexus’ take sensory information from and motor info to the lower limbs

• (take sensory info from the lower limbs and send motor info to the lower limbs)

Lumbar plexus

• L1-L4

• contains the obturator nerve and the femoral nerve

Obturator Nerve

major nerve of the lumbar plexus that innervates the adductor muscles of the thigh

Femoral Nerve

major nerve of the lumbar plexus that innervates muscles of the anterior thigh

Sacral Plexus

• L4-S4

• the tibial nerve and the common fibular nerve unite to form the Sciatic nerve which innervates the leg and foot

Coccygeal Plexus

S5-Co

Sciatic Nerve

composed of the medial tibial nerve and the lateral common fibular nerve and can be seen at the distal part of the thigh

Tibial Nerve

found in the sacral plexus and helps make up the sciatic nerve

Common Fibular Nerve

found in the sacral plexus and is the second nerve that helps make up the sciatic nerve