Exam 3; Nervous System

Question 1

What is the function of the nervous system?

Answer 1

The nervous system receives information about the internal and external environment, processes information and determines a response, and issues commands to cells to carry out the response. Functions in sensory perception, integration, and motor planning.

Question 2

What are the two main divisions of the nervous system?

Answer 2

Central Nervous system- brain and spinal cord

Peripheral nervous system- nerves and ganglia

Question 3

What are the two subcategories of the peripheral nervous system?

Answer 3

PNS has sensory and motor division. The sensory (afferent) division carries signals from sensory receptors through afferent nerve fibers to the brain or spinal cord. The motor (efferent) division carries signals from the CNS through efferent nerve fibers to the effectors which are the cell or organs carrying out the responses.

The sensory division is further separated into the visceral and somatic sensory division. Visceral sensory division carries signals from viscera of the thoracic and abdominal cavities whereas the somatic sensory division carries signal from receptors in the skin, muscles, bones, and joints.

The motor division is divided into visceral and somatic motor division. Visceral motor division is also called the autonomic nervous system and carries messages to glands, cardiac muscle, and smooth muscle. The ANS is further divided into the sympathetic and parasympathetic nervous system divisions. The somatic motor division sends signals to skeletal muscles many of which are under voluntary control.

Question 4

What are the 3 universal properties of neurons?

Answer 4

1. Excitability/ irritability- neurons are highly responsive to stimuli
2. Conductivity- neurons respond to stimuli by producing electrical signals
3. Secretion- neurons secrete a neurotransmitter when an electrical signal reaches the end of the nerve fiber.

SEC!!

Question 5

What are the 3 functional classes of neurons?

Answer 5

1. Sensory/ afferent- Sensory neurons are specialized the detect stimuli and carry information to brain or spinal cord.
2. Interneurons/ association- interneurons lie within the CNS. They receive, process, store, and retrieve information. They interconnect incoming sensory pathways and outgoing motor pathways. Where the decisions are made about the response to a stimuli
3. Motor/ efferent- motor neurons send signals to effectors like muscles of glands that carry out responses.

Question 6

What are the important structures within the neuron?

Answer 6

Cytoskeleton compartmentalizes the rough ER into dark-stained regions called Nissl bodies which is unique to neurons.
Mature neurons lack centrioles and do not undergo mitosis. Additionally know dendrites, axon, axon hillock, synapse, and synaptic knob.

Question 7

What are the 6 types of glial cells present in CNS and PNS?

Answer 7

In CNS…
1. Oligodendrocytes
2. Ependymal cells
3. Microglia
4. Astrocytes

In PNS…
1. Schwann cells
2. Satellite cells

Question 8

What is the function of oligodendrocytes in the CNS?

Answer 8

These cells form the myelin sheath around nerve fibers in the CNS.

Question 9

What is the function of ependymal cells in the CNS?

Answer 9

These cells resemble cuboidal epithelial cells and line the internal cavities of the brain and spinal cord. They produce cerebrospinal fluid.

Question 10

What is the function of microglia in the CNS?

Answer 10

These are small macrophages that derive from WBCs. They wander the CNS and phagocytize microorganisms, dead tissue, and foreign matter.

Question 11

What is the function of astrocytes in the CNS?

Answer 11

Astrocytes are the most abundant glial cells in the CNS. Star like shape. They have numerous functions including providing structural support to neurons, contribute to the BBB, converts glucose to lactate to supply neurons with nutrients, secrete factors for neuronal growth, regulate chemical composition of tissue fluid, and more.

Question 12

What is the function of Schwann cells in the PNS?

Answer 12

Schwann cells form the myelin sheath and assist in the regeneration of damaged fibers.

Question 13

What is the function of satellite cells in the PNS?

Answer 13

These cells surround the neuron cell bodies in the ganglia in the PNS and regulate the chemical environment. They provide support and nourishment.

Question 14

What is the difference between myelin coverings in the CNS versus the PNS?

Answer 14

Insulation in the CNS is called myelin sheath and is made by oligodendrocytes. It consists of the plasma membranes of the glial cells and lipids. Nerve cells in CNS do not have neurilemma or an endoneurium.

In the PNS, Schwann cells surround the axon and form sleeve called the neurilemma. External to that is a thin covering of fibrous CT called the endoneurium. These two components are essential for regeneration of damaged nerve fibers.

Question 15

What are the two factors in changing signal conduction in the nervous system?

Answer 15

1. Diameter of fiber- larger is faster
2. Presence of myelin- myelinated is faster

Question 16

What are electrical synapses?

Answer 16

These are adjacent cells joined by gap junctions. The gap junctions allow ions to diffuse directly from one cell to the next allowing for quick transmission but does not allow cells to integrate information or make decisions.

Question 17

What are the 3 main functions of the spinal cord?

Answer 17

1. Conduction- nerve fibers conduct information up and down connecting the different levels of the cord with the brain
2. Locomotion- walking requires coordinated contractions of muscle groups. Groups of neurons in cord serve as central pattern generators.
3. Reflexes- cord is responsible for certain involuntary, stereotyped responses to stimuli.

Question 18

What are the 4 separate sections of the spinal cord and why are they named the way they are?

Answer 18

1. Cervical
2. Thoracic
3. Lumbar
4. Sacral

Named for the level of the vertebral column from which the spinal nerve emerge.

Question 19

What are the three layers of the meninges, the connective tissue layer that encloses the brain and spinal cord?

Answer 19

1. Dura mater- most superficial layer. Protective sheath around nervous tissue. The space between dura mater and bone is the epidural space.
2. Arachnoid mater- spider wed-like structure that adheres to the dural sheath. It is made of simple squamous epithelium and loose mesh of collagenous and elastic fibers.
3. Pia mater- thin inner translucent membrane layer that adheres to spinal cord and follows its contours.

Question 20

What is grey matter?

Answer 20

Grey matter contains somas, dendrites, and proximal parts of the axons of neurons. It is the sit of synaptic contact between neurons and where information is processed in the CNS. Contains little myelin.

Question 21

What is white matter?

Answer 21

White matter consists of mainly myelinated axons that are organized into bundles called tracts that carry signals from one part of the CNS to another. White matter in spinal cord surrounds grey matter.

Question 22

Describe the ascending and descending spinal tracts.

Answer 22

Ascending spinal tracts carry sensory information to the brain. Sensory pathways contain first, second, and third order nerve fibers.

Descending tracts carry motor information from the brain to muscles. Many tracts cross over at midline.

Question 23

What are two important ascending tracts in the CNS?

Answer 23

Posterior column-medial lemniscus pathway
Spinothalamic pathway

Question 24

What are the two important descending tracts in the CNS?

Answer 24

Lateral corticospinal fibers
Anterior corticospinal fibers

Question 25

Describe the different coverings over a nerve.

Answer 25

A nerve is several axons wrapped by connective tissue. The endoneurium wraps 1 axon. The perineurium wraps a fascicle of axons. Epineurium wraps the entire nerve.

Question 26

What is the ganglion?

Answer 26

This is a cluster of nerve cell bodies in the PNS that is associated with nerves.

Question 27

Describe how spinal nerves carrying sensory and motor signals.

Answer 27

Dorsal and ventral root of spinal nerve merge and penetrate the dural sac and exit through intervertebral foramen as a complete spinal nerve carrying both types of signals. After that, it divides into a dorsal ramus, ventral ramus, and meningeal branch. The branch reenters the vertebral canal and innervates the meninges, vertebra, and spinal ligaments. The dorsal ramus supples muscles, joints, and back skin. Ventral ramus innervates lateral and ventral skin and muscles of trunk and gives rise to the nerves of the limbs.

Question 28

What are nerve plexuses?

Answer 28

Plexuses receive fibers from anterior rami and gives rise to peripheral nerves. There is the cervical, brachial, lumbar, sacral, and coccygeal plexus.

Question 29

What does the cervical plexus innervate?

Answer 29

Innervates structures in the head and neck. Arises from ventral rami of nerves C1 to C5. It gives rise to the phrenic nerve and supplies diaphragm.

Question 30

What does the brachial plexus innervate?

Answer 30

All the nerves that supply the upper limbs lie within the brachial plexus. They arise from ventral rami of nerves C3 to T2.

Question 31

What does the lumbar plexus innervate?

Answer 31

It gives rises to nerves that supply structure in the lower abdomen and thing, and skin of the leg. Arises from ventral rami of nerves L1 to L4 with some fibers from T12.

Question 32

What does the sacral plexus innervate?

Answer 32

The sacral plexus gives off to the sciatic nerve which is a combo of the tibial and common fibular nerves. Arises from nerves L4, L5, and S1 to S4.

Question 33

What is a dermatome?

Answer 33

This is an area of the skin that each spinal nerve except C1 receives input from.

Question 34

What are somatic reflexes?

Answer 34

These are reactions to stimulation that show the characteristics of being quick, involuntary, and response is the same. These have relatively simple neural pathways.