Chapter 7 pt 1

What are the primary functions of the nervous system?

Sensory input, integration, motor output.

What are the two major structural divisions of the Central Nervous System (CNS)?

Brain and spinal cord.

What are the two major divisions of the Peripheral Nervous System (PNS)?

Sensory (afferent) division and motor (efferent) division.

How many cranial nerve pairs and spinal nerves are there?

12 pairs of cranial nerves and 31 pairs of spinal nerves.

What parts of the nervous system send commands to effector targets?

The motor (efferent) division.

What is a sensory (afferent) neuron?

Carries information to the CNS from receptors; found in the PNS.

What is a motor (efferent) neuron?

Carries commands away from the CNS to muscles or glands; found in the PNS.

What is an interneuron?

Connects sensory and motor neurons; found only in the CNS.

What type of structures are served by somatic nerves?

Skeletal muscles.

What type of structures are served by autonomic nerves?

Smooth muscle, cardiac muscle, and glands.

What is myelin and what are its functions?

A fatty covering around axons that insulates, protects, and speeds up nerve impulse conduction.

What is Multiple Sclerosis?

An autoimmune disease that destroys myelin in the CNS, slowing or blocking nerve signals.

What PNS neuroglial cell produces myelin?

Schwann cells.

What CNS neuroglial cell produces myelin?

Oligodendrocytes.

What is a node of Ranvier?

A small gap between myelin segments on an axon.

What structures are concentrated in the node area?

Sodium and potassium channels.

What is continuous conduction?

Action potential travels along the entire axon (unmyelinated); slower.

What is saltatory conduction?

Action potential jumps from node to node (myelinated); much faster.

What are the three types of neurons?

Unipolar, bipolar, and multipolar.

Where are unipolar neurons found?

Most sensory neurons.

Where are bipolar neurons found?

Retina, inner ear, olfactory receptors.

Where are multipolar neurons found?

Most neurons in the brain and spinal cord; motor neurons.

What are the four types of neuroglial cells in the CNS?

Astrocytes, oligodendrocytes, microglia, ependymal cells.

What are the two types of neuroglial cells in the PNS?

Schwann cells and satellite cells.

What is the blood-brain barrier?

A protective barrier that prevents harmful substances from entering the brain, made mainly of capillary endothelial cells with help from astrocytes.

What is the approximate resting membrane potential of a neuron?

About -70 mV.

What ions are concentrated outside and inside a resting neuron?

Outside: Sodium (Na⁺), Chloride (Cl⁻); Inside: Potassium (K⁺), negatively charged proteins.

What are leakage channels?

Always open; help maintain resting potential.

What are ligand-gated channels?

Open when neurotransmitters bind; found on dendrites and cell body.

What are voltage-gated channels?

Open when membrane voltage changes; found mainly on axons; create action potentials.

What is the all or none principle of action potentials?

If threshold is reached, a full action potential occurs; if not, no action potential occurs.

What is depolarization?

Na⁺ enters; membrane becomes more positive.

What is repolarization?

K⁺ leaves; membrane returns toward resting.

What is hyperpolarization?

Membrane becomes more negative than resting before returning to normal.

What is a refractory period of a neuron?

A short time after an action potential when another action potential cannot or is less likely to occur.

What is a group of cell bodies called in the PNS?

Ganglion.

What is a group of cell bodies called in the CNS?

Nucleus.

What are the three horns of grey matter?

Posterior (dorsal) horn, anterior (ventral) horn, lateral horn.

Where are the cell bodies of motor neurons to skeletal muscle found?

In the anterior (ventral) horn.

What is the arrangement of grey and white matter in the spinal cord?

Gray matter inside, white matter outside.

What is the arrangement of grey and white matter in the brain?

Gray matter outside (cortex), white matter inside.

What are tracts?

Bundles of axons in the CNS.

What are nerves?

Bundles of axons in the PNS.

What information is carried in the ascending tracts?

Sensory information to the brain.

What information is carried in the descending tracts?

Motor commands from the brain.

What does the term decussate mean?

To cross from one side of the body to the other.

What are some general sensory receptors?

Nociceptors, mechanoreceptors, proprioceptors, muscle spindle, Golgi tendon organ.

What are spinal roots?

Connect spinal nerves to the spinal cord.

What types of neuron fibers are in the dorsal roots?

Sensory (afferent) fibers.

What structures are found in the dorsal root ganglion?

Cell bodies of sensory neurons.

What types of neuron fibers are found in the ventral roots?

Motor (efferent) fibers.

Where are the cell bodies for the neurons exiting the cord through the ventral roots located?

In the ventral (anterior) horn of the spinal cord.

What are mixed nerves?

They contain both sensory (afferent) and motor (efferent) fibers.

What is the dorsal ramus?

Supplies the back muscles and skin.

What is the ventral ramus?

Supplies the front and sides of the body and limbs.

What are rami communicantes?

Connect spinal nerves to the sympathetic nervous system.

What is a plexus?

A network of intersecting ventral rami that forms major peripheral nerves.

What are the nerve root levels of the plexuses?

Cervical (C1-C5), brachial (C5-T1), lumbar (L1-L4), sacral (L4-S4).

What regions do the cervical plexus innervate?

Neck and diaphragm.

What regions do the brachial plexus innervate?

Shoulder and upper limb.

What regions do the lumbar plexus innervate?

Lower abdomen and front of leg.

What regions do the sacral plexus innervate?

Buttocks, back of leg, foot, pelvis.

What is a reflex arc?

The pathway that produces a quick, automatic response to a stimulus.

What are the basic components of any reflex arc?

Receptor, sensory (afferent) neuron, integration center, motor (efferent) neuron, effector.