Comparative Vertebrate Anatomy Final

Ch. 13-15, and some cumulative from previous chapters; Includes quiz questions (UNFINISHED)

The nervous system consists of two interconnected parts:

• Central Nervous System (CNS)

• Peripheral Nervous System (PNS)

What is in the CNS?

The brain and spinal cord

What is in the PNS?

All nervous tissue outside of the CNS

The nervous system receives stimuli from ____?

Receptors

The nervous system transmits information to ____?

Effectors

What are the two types of cells within the nervous system?

• Neurons

• Neuroglial cells (glia)

Neuroglial cells do not transmit impulses, they instead:

Support, nourish, and insulate neurons

What are the specialized types of neuroglial?

• Microglia

• Oligodendroglia and Schwann cells

• Ependymal cells

• Astrocytes

What do microglia do?

Engulf foreign material and bacteria

What do oligodendroglia and Schwann cells do?

Insulate the axons of neurons

What do ependymal cells do?

Line the central canal of the brain and spinal cord

What do astrocytes do?

Pass nutrients between blood capillaries and neurons.

Neurons are specialized for what?

Long-distance transmission of electrical stimuli throughout the body.

What does a neuron consist of?

• Perikaryon (the body or soma of cell)

• Thin processes = Nerve fibers

What are the two types of nerve fibers and function?

• Axon — Carry impulses away from the perikaryon

• Dendrites — Transmit incoming electrical impulses toward the perikaryon

There is usually one ______ per neuron and one or many _____.

axon, dendrites

Neurons are grouped by the number of their processes. What are the types of groupings?

• Unipolar neurons (single stem divided into a dendrite and an axon)

• Bipolar neurons (two processes, opposite ends)

• Multipolar neurons (many processes)

A collection of nerve fibers running together are called:

• Tract (in CNS)

• Nerve (in PNS)

A collection of nerve cell bodies is called what if its in the CNS?

Nucleus

What is a collection of nerve cell bodies called when it is in the PNS?

Ganglion

Neuroglial cells wrap some axons in a:

Myelin sheath

Fibers that are wrapped in a sheath are called _____, and those without a sheath are called _____.

Myelinated nerves, unmyelinated nerves

What are Nodes of Ranvier?

Breaks in the myelin sheath that allow the nerve signal to jump between nodes.

Myelin producers are ____in the PNS

Schwann cells

Myelin producers are _______ in the CNS

Oligodendroglial cells

Transmission is electrical through the plasma membrane. What are the two kinds of impulses?

• Graded potential

• Action potential

A wave of electrical excitation proportional to the magnitude of the stimulus that triggers it.

Graded potential

All-or-none phenomenon. Once initiated, it propagates without decrement along a nerve fiber.

Action Potential

A gap between processes of one neuron and the next

Synapse

Cross synapse and trigger transmission of impulse

Neurotransmitters

Peripheral nerves serve either _____ or_______ tissues and carry sensory or motor information.

Somatic, visceral

Pass to or from somatic tissues (skeletal muscle, skin, and their derivatives).

Somatic nerves

Pass to or from the viscera (involuntary muscles and glands)

Visceral nerves

Somatic nerves are broken down further into two different neurons. What are the two neurons?

• Afferent (or sensory neurons)

• Efferent (or motor neurons)

Afferent neurons carry information which way?

From tissues to the CNS

Efferent neurons carry information which way?

Away from the CNS

Peripheral nerve development arises from:

• Neurons that differentiate in the spinal cord

  • Axons grow outwards to ganglia or effectors they supply.

  • Ventral roots

• Neural crest

  • Migrate to specific locations and grow processes back to CNS

  • Dorsal roots

The source of somatic muscles

Myotomes

The source of dermal connective tissue and muscle

Dermatome

Which cranial nerve is not technically a nerve but an extension of the brain?

Nerve II

Which cranial nerve is just the fusion of nerve X (10) and the first two spinal nerves?

Nerve XI

Most amniotes are said to have 10 numbered cranial nerves plus—

6 pairs of unnumbered, lateral line cranial nerves

What dorsal nerves do not fuse in the head?

• V

• VII

• IX

• X

What ventral nerves do not fuse in the head?

• III

• IV

• VI

• XII

Special cranial nerves are nerves that are concerned with localized senses. What are some of the nerves?

• I

• II

• VIII

• Lateral line

• Taste

Primitively, cranial nerves that serve the branchial pouches form 3 branches per pouch:

• Pretrematic

• Posttrematic

• Pharyngeal

Anamniotes typically have how many cranial nerves?

17

Describe the Olfactory Nerve (I)

Olfactory cells with short axons that go to the olfactory bulb. Each axon constitutes an olfactory fiber. Collectively, the olfactory fibers form the short olfactory nerve, which is the only cranial nerve composed of the axons of the receptor cells themselves.

Describe the Optic Nerve (II)

A sensory tract, develops as an outpocketing of the brain.

Describe the Oculomotor Nerve (III)

Primarily supplies the extrinsic eye muscles (superior rectus, medial rectus, inferior rectus, and inferior oblique muscles). It is a motor nerve that also carries a few visceral motor fibers to the iris and ciliary body of the eye.

Describe the Trochlear Nerve (IV)

A motor nerve that supplies the extrinsic, superior oblique eye muscle.

Describe the Trigemenal (trigeminus) Nerve (V)

First branchial arch; formed of three branches:

• Deep Ophthalmic (V₁): May be independent (arises from placode, not neural crest)

• Maxillary (V₂): To upper jaw (pretrematic)

• Mandibular (V₃):To lower jaw (posttrematic)

Describe the Abducens Nerve (VI)

The third of the three cranial nerves that innervate muscles controlling movements of the eyeball. It is a motor nerve that supplies the extrinsic lateral rectus eye muscle.

Describe the Facial Nerve (VII)

Sensory fibers from taste buds, motor fibers that serve the derivatives of the second (hyoid) arch, and sensory fibers to the skin

Describe the Auditory Nerve (VIII)

The sensory octaval nerve (acoustic, vestibulocochlear, statoaucoustic) that carries sensory fibers from the inner ear, which is concerned with balance and hearing.

Describe the Glossopharyngeal Nerve (IX)

Supplies the third branchial arch. It contains sensory fibers from the taste buds, the first gill pouch, and the adjacent pharyngeal lining.

Define the Vagus Nerve (X)

Serves areas of the mouth, pharynx, and most of the viscera. It is formed by the union of several roots across several head segments.

Describe the Spinal Accessory Nerve (XI)

In amniotes, it is a small but distinct motor nerve that supplies derivatives of the cucullaris muscle (cleidomastoid, sternomastoid, trapezius).

Describe the Hypoglossal Nerve (XII)

In amniotes, it is a motor nerve that innervates hyoid and tongue muscles

Once thought that they were branches of other nerves, this structure arose separately from dorsal placodes.

Lateral Line Nerves

Describe the Recurrent Laryngeal Nerve

A branch of the vagus, innervates the larynx. Helps us speak and swallow. Instead of running straight to the larynx, it takes a detour around the aorta

The Sympathetic Nervous System prepares the body for strenuous activity. What are the other things it causes?

• Inhibits the alimentary canal

• Promotes contraction of the spleen to release more RBC

• Increases heart rate and blood pressure

• Dilates coronary arteries

• Mobilizes glucose from glycogen storage

The Parasympathetic Nervous System does what?

• Stimulates alimentary canal

• Lowers activity level

• Restores the body to a restful state

Which of the following is stimulated in the Sympathetic system?

Heart

What are the three sources of information that the CNS receives?

• The sensory receptors (interoceptors)

• Exteroreceptors

• Memory

What are proprioceptors?

A type of interoceptors; sense of self, where your body parts are — somatosensory system

What are the three embryonic regions of the brain?

• Prosencephalon

• Mesencephalon

• Rhombencephalon

What does the prosencephalon differentiate into?

Forebrain

What does the mesencephalon differentiate into?

Midbrain

What does the rhombencephalon differentiate into?

Hindbrain

The brain and spinal cord are wrapped in meninges. What are the three layers?

• Dura mater

• Arachnoid

• Pia mater

What is the center for higher thought in humans?

Forebrain

What is the center for higher thought in fishes?

Midbrain

Are the areas for higher thought in the cerebrum homologous among taxa?

No

In fish, the meninges consist of a single membrane, which is wrapped around the brain and spinal cord.

Primitive menix

In amphibians, reptiles, and birds, the meninges split into —

A thick dura mater and a thin inner secondary menix.

In mammals, the dura mater persists but division in the secondary menix yields——

The arachnoid and the pia mater

What is the choroid plexus and what does it do?

Small tufts of blood vessels and ependymal cells that project into ventricles at specific sites and is the primary source of cerebrospinal fluid

Cerebrospinal fluid flows in what spaces?

Subdural and subarachnoid spaces

What is white matter?

Myelinated nerves. Nerve fibers linking sections of the spinal cord with each other and the brain.

What is gray matter?

Non-myelinated nerves. Nerve cell bodies that lie in the core of the spinal cord

What is the function of the spinal cord?

• Simple reflexes

• Pathways of diverging and converging info

What makes up the hindbrain?

• Medulla oblongata

• Pons

• Cerebellum

What makes up the midbrain?

• Tectum

• Tegmentum

What makes up the forebrain?

• Telencephalon (cerebrum)

• Diencephalon (Thalamus)

The brainstem includes what regions?

• Hindbrain (except for the cerebellum)

• Midbrain

Explain forebrain enlargement

Independently, the forebrain tends to enlarge in various vertebrate groups. Some of this is correlated with the increased importance of olfactory information.

Explain forebrain enlargement in Amniotes

Forebrain enlargement also accompanies increasingly complex behaviors and muscle control. Limb posture and body carriage change with the legs being under the body in archosaurs and mammals. Coordination in limb oscillation is complex, especially in bipedal archosaurs and birds. Increase in somatosensory input and output of motor responses.

Describe the Autonomic Nervous System in Hagfishes

• ANS is fragmentary

• Cranial autonomic fibers only in cranial nerve X

• Spinal autonomic fibers distribution poorly known

Describe the ANS in Lamprey

• Autonomic system is also fragmentary, but better developed than in hagfishes

• Cranial autonomic fibers are only in cranial nerves VII, IX, X

• Spinal autonomic fibers supply most viscera

The medulla oblongata serves as——

A route for ascending and descending pathways

The medulla oblongata controls:

Unconscious, essential functions such as breathing, blood circulation, and muscle tone

The pons is located—

in the floor of the hindbrain

The cerebellum is absent in what species?

Agnathans

In fishes, the cerebellum contains —-

• Medial Corpus

• Lateral Auricles

In tetrapods, what is homologous to the dorsal half of the auricle in fishes?

Flocculus

Which organ is a good example of nerve mapping?

Diaphragm

Cranial nerves are part of the _____ nervous system

Peripheral

Which cells are responsible for myelinating axons in the central nervous system?

Oligodendroglia

A bundle of nerve fibers running in the central nervous system is known as _______.

Tract