Spinal Cord, Spinal nerves, reflexes

Gray matter

Mostly cell bodies

Where is gray matter located

surrounds the central canal, which is filled with cerebrospinal fluid

White matter

Composed of myelinated fiber tracts

What are the three regions of white matter of the spinal cord?

Dorsal, lateral, ventral columns

Dorsal (posterior) horn

Receive information from sensory neurons in the dorsal root; cell bodies housed in dorsal root ganglion

Ventral (anterior) horn

Send motor information out ventral root. house motor neurons of the

somatic (voluntary) nervous system

Lateral horn

Lateral outpocketing of gray matter on each side

Central canal

Contains cerebrospinal fluid

Dorsal root

Contains association neurons and sensory fibers that enter the spinal cord through the dorsal root

Dorsal root ganglion

an enlarged area of the dorsal root where Cell bodies of the dorsal root are found in

Ventral root

transmits motor signals from the spinal cord to the body's peripheral muscles and glands

Spinal nerve

carry impulses to and from the spinal cord

Posterior column

major ascending white matter pathway in the spinal cord

Lateral column

primarily involved in the sympathetic nervous system. Gray matter T1-L2

Anterior column

most forward structural unit of the spinal column

Ascents (sensory) tracts

Conduct impulses toward brain

Descending (motor) tracts

carry impulses from brain to skeletal muscles

Reflex

Rapid, predictable, and involuntary responses to stimuli

Somatic reflexes

Involuntary reflexes that stimulate the skeletal muscles

Autonomic reflexes

Regulate the activity of smooth muscles, the heart, and glands

Monosynaptic reflex

a simple, involuntary neural pathway involving a single synapse between a sensory neuron and a motor neuron

Polysynaptic reflex

a rapid, involuntary neural pathway involving multiple interneurons and synapses (two or more) within the CNS

Autonomic reflex

Activate smooth muscle, cardiac muscle and the glands of the body. They regulate body functions such as digestion and blood pressure

Somatic reflex

all reflexes that stimulate skeletal muscles

Patellar reflex

The patellar ligament is struck by the reflex hammer. Assesses L2-L4

Pupillary reflex

The retina of the eye is the receptor, the optic nerve contains the afferent fibers, the oculomotor nerve conducts efferent impulses to the eye, smooth muscle of the iris is the effector

Reaction time

the voluntary, conscious time taken to perceive and respond to a stimulus

What features protect the spinal cord?

Vertebrae and meninges

What are the five steps of a typical reflex arc.

1.) Sensory receptor- reacts to a stimulus

2.) Sensory neuron- carries message to the integration center

3.) Integration center (CNS)- Processes information and directs motor output

4.) Motor neuron- Carries message to an effector

5.) Effector organ- Is the muscle or gland to be stimulated

Somatic sensroy (afferent) fibers

Carry information from the skin, skeletal muscles and joints

Visceral sensory (afferent) fibers

Carry information from visceral organs

Five units of the reflex arc

Receptor, sensory neuron, integration center, motor neuron, effector