Nervous system

9. Describe the role of "peripheral load" in development of the spinal cord.

Peripheral load determines amount of cell death in both spinal cord and ganglia.

1. Explain how the autonomic nervous system differs from the somatic system regarding general function and structure of neuronal pathways.

The somatic nervous system controls voluntary activities (innervation of skeletal muscle). The autonomic nervous system controls involuntary activities (innervation of smooth muscle and glands). The autonomic nervous has some sensory neurons, but is primarily a motor system. The somatic nervous system uses a signal neuron from the CNS to the effector organ, while the autonomic nervous system used two- neuron system. The preganglionic neuron projects to an autonomic ganglion and the postganglionic neuron then projects to the target organ. The autonomic system can stimulate or inhibit, while the somatic system can only stimulate.

8. Describe the early development of the spinal cord, including the location of dividing and differentiating cells.

The spinal cord is derived from the neural tube of the early embryo. The cord grows by mitosis within the epithelium. The mantle and marginal layers are formed as cells cease dividing and differentiate within the cord. Neurons differentiate within the mantle (future gray matter) and fibers grow into the marginal layer (future white matter).

2. Indicate the embryonic origin of ganglia of the autonomic nervous system.

The sympathetic ganglia develop from neural crest cells and contain the cell bodies of motor neurons.

6. Give examples of specific functions controlled by the sympathetic system and indicate how it interacts with the adrenal gland.

Those with cell bodies in the cervical ganglia innervate the iris, salivary glands, and the heart. Those with cell bodies in a chain ganglion send axons back to a spinal nerve via the "gray ramus"; they innervate sweat glands, muscles of skin, bronchial tubes, arteries and the heart. Those with cell bodies in the mesenteric and coeliac ganglia innervate muscle of the stomach, intestines, and bladder, the pancreas, liver, adrenal medulla, and the genitalia. The medulla of the adrenal gland (an endocrine organ) is innervated by preganglionic neurons. All preganglionic neurons that enter these ganglia synapse with a postganglionic neuron, except for those which innervate the adrenal medulla. These preganglionic neurons run through the ganglion and terminate in the medulla. Thus the adrenal medulla, itself, acts as a large postganglionic neuron and secretes adrenergic hormones into the blood stream.

1. Distinguish between the central vs. peripheral nervous system and the somatic vs. autonomic nervous system.

he central nervous system (CNS) consists of the brain and spinal cord. The peripheral nervous system (PNS) consists of nerves and ganglia. The somatic nervous system controls voluntary activities (innervation of skeletal muscle). The autonomic nervous system controls involuntary activities (innervation of smooth muscle and glands).

7. Define "ganglion" and indicate where spinal and sympathetic ganglia are located in the mammalian body.

. Ganglia are clusters of neuronal cell bodies in the peripheral nervous system. and sympathetic ganglia are located close to and on either side of the spinal cord. Spinal ganglia are located in the dorsal root

6. Define "nerve" and distinguish between a nerve and a neuron.

A nerve is a bundle of axons. A neuron is the basic cell of the nervous system and is made of the cell body, dendrites, and an axon.

6. Explain the functions of a "reflex arc".

A reflex is a muscular response that does not require input from the brain. This is possible because many sensory neurons make connect to motor neurons via association neurons within the spinal cord. Thus a stimulus can elicit an immediate response prior to the sensory stimulus reaching the brain.

2. Indicate the location of cerebral spinal fluid within the spinal cord.

Cerebral spinal fluid flows through the subarachnoid space and central canal.

5. Describe the anatomy of the sympathetic system and be able to trace a command through this system from the spinal cord to various target organs.

Chain ganglia are connected to form the "sympathetic trunk". Each ganglion is connected to a spinal nerve by white and gray rami. A few ganglia are located elsewhere in the body (called collateral ganglia). Cervical ganglia are in the neck. Mesenteric and coeliac ganglia are in the abdominal cavity. 2. Sympathetic neurons Preganglionic neurons are cholinergic and originate in the spinal cord. Their cell bodies are in the motor horns. Their axons leave the spinal nerve via the "white ramus". They synapse with a second sympathetic neuron within a ganglion. Postganglionic neurons are adrenergic and originate in a sympathetic ganglion. Those with cell bodies in the cervical ganglia innervate the iris, salivary glands, and the heart. Those with cell bodies in a chain ganglion send axons back to a spinal nerve via the "gray ramus"; they innervate sweat glands, muscles of skin, bronchial tubes, arteries and the heart. Those with cell bodies in the mesenteric and coeliac ganglia innervate muscle of the stomach, intestines, and bladder, the pancreas, liver, adrenal medulla, and the genitalia.

5. Describe the structure of a spinal nerve, including dorsal and ventral roots, spinal (sensory) ganglion, and dorsal and ventral rami.

Each spinal nerve is connected to the spinal cord by a dorsal and ventral root. Each dorsal root contains a spinal ganglion which contains cell bodies of sensory neurons. Each ventral root contains the axons of motor neurons. Each spinal nerve splits into a dorsal and ventral branch immediately after passing through the vertebral column. The dorsal branch innervates (supplies) dorsal skin and epaxial muscles. The ventral branch innervates ventral skin, hypaxial muscles and limbs (at cervical and lumbar levels).

4. Draw a cross section of the spinal cord and indicate the location and functional significance of gray matter (dorsal vs. ventral regions) and white matter.

Gray matter of the spinal cord contains neuronal cell bodies and neuroglial cells, whereas white matter contains mainly neuronal fibers (no cell bodies). Ventral horns of the gray matter are larger; they contain the cell bodies of motor neurons. Dorsal horns of the gray matter contain cell bodies of association neurons; they send sensory information to the brain and connect sensory and motor neurons within the cord. look at photo

10. Describe the location of the vagus nerve and list several organ functions which it controls.

It extends from the brain stem to the abdomen, via various organs including the heart, esophagus and lungs. involuntary nervous system and commands unconscious body procedures, such as keeping the heart rate constant and controlling food digestion.

11. Define "enteric nervous system" and describe its general structure and function.

It is located within the intestinal wall and regulates peristalsis and other intestinal functions.

3. Describe the location within the body of: sympathetic (chain) ganglia collateral ganglia terminal ganglia (parasympathetic system) sympathetic trunks

Most ganglia are located along sides of the spinal cord (called paravertebral or chain ganglia). A few ganglia are located elsewhere in the body (called collateral ganglia) terminal ganglia lie near or within (respectively) the organs they innervate. Many tiny ganglia are found within organs of the thoracic and abdominal cavity (called "terminal" ganglia). Chain ganglia are connected to form the "sympathetic trunk"

4. Distinguish between preganglionic vs. postganglionic neurons.

Preganglionic neurons are cholinergic and originate in the spinal cord. Their cell bodies are in the motor horns. Their axons leave the spinal nerve via the "white ramus". They synapse with a second sympathetic neuron within a ganglion. Postganglionic neurons are adrenergic and originate in a sympathetic ganglion.

5. Describe the structure and function of the myelin sheath and indicate how it is formed.

Schwann cells are responsible for the formation of myelin sheaths around neuronal fibers. This sheath insulates the fiber and speeds the conduction rate.. First the axon sinks into the cytoplasm of a Schwann cell. Next the edge of the Schwann cell begins to wrap around the axon. As the wrapping proceeds, the cytoplasm is squeezed out, leaving only layers of Schwann cell plasma membrane. These membrane layers form the myelin sheath

4. List and describe the types of neuroglia cells found in the nervous system and give the function of each.

Schwann cells form a myelin sheath around axons in the PNS. Oligodendrocytes form a myelin sheath around axons in the CNS. Astrocytes support and nourish neurons in the CNS. Microglial cells are the "macrophages" of the CNS.

7. Indicate the path by which sensory information is transmitted from a sensory organ to the brain.

Sensory information enters the spinal cord on the same side of the body as the stimulus. Ascending tracts cross over the midline of the body to the contralateral side of the thalamus. The thalamus directs the signal to the cerebral cortex for conscious perception. The pathway is direct with very few neurones involved.

8. Describe the anatomy of the parasympathetic system and be able to trace a command through this system from the brain or spinal cord to various target organs.

Several large collateral ganglia are located in the head. Many tiny ganglia are found within organs of the thoracic and abdominal cavity (called "terminal" ganglia). 3. Parasympathetic neurons All neurons are cholinergic. Preganglionic neurons originate within the brain or sacral region of spinal cord. The axons of cell bodies located in the brain join cranial nerves as they grow to the periphery. The axons of sacral neurons leave the spinal cord via the spinal nerves. Postganglionic neurons originate in the parasympathetic ganglia. Neurons of the collateral ganglia have long axons which innervate the iris, tear and salivary glands. Neurons of the terminal ganglia are very short and innervate the respiratory and digestive organs, heart, bladder and genitalia.

1. Name and describe the 3 meninges of the spinal cord (indicate the location and function of each).

The cord is covered by 3 layers of connective tissue called meninges. The dura mater is a tough protective covering. The archnoid layer and pia mater (inside layer) are thin, vascular coverings which nourish the cord.

7. Explain how the function of the adrenal medulla overlaps that of the sympathetic nervous system.

The medulla of the adrenal gland secretes the hormone epinephrine which has similar actions on the body as the sympathetic nerves. Thus the adrenal gland and sympathetic nervous system have overlapping functions in activating the body for stress.

2. Describe the basic structure of a neuron and indicate the function of the following parts: neuronal cell body dendrite axon

The neuron cell body produces all proteins and energy for the neuron and its parts. The dendrites receive signals from other cells. The axon conducts electrical signals and transmits information to different cells. look at picture

3. Describe the fiber pattern, function, and location within the CNS of: pseudounipolar neurons bipolar neurons multipolar neurons

Unipolar or pseudounipolar neurons have only one fiber attached to the cell body which resides in a ganglion; have a sensory function. Bipolar neurons have one axon and one dendrite attached to the cell body which resides in the brain or spinal cord; have an integrative function (association neurons). Multipolar neurons have one axon and many dendrites attached to the cell body which reside mainly in the spinal cord; have a motor function.

3. Indicate the location of the neuronal cell bodies of sensory, motor, and association neurons.

Unipolar or pseudounipolar neurons have only one fiber attached to the cell body which resides in a ganglion; have a sensory function. Bipolar neurons have one axon and one dendrite attached to the cell body which resides in the brain or spinal cord; have an integrative function (association neurons). Multipolar neurons have one axon and many dendrites attached to the cell body which reside mainly in the spinal cord; have a motor function.

9. Compare the sympathetic and parasympathetic system regarding: general function location of ganglia relationship to the CNS **

Whereas the sympathetic system acts as an accelerator of most bodily functions, the parasympathetic system acts as a brake. It returns the body to its "resting state". Sympathetic ganglia are located near the spinal cord and have a lot of branching so many organs can be controlled at once. Parasympathetic ganglia are located near the target organ and hardly has any branching.