Lab - Dogfish Shark Nervous System

Question 1

Describe the major parts of the neuron

Answer 1

Cell body which is nucleated and carries out normal cell functions, receptive region (may contain dendrites), axon which conducts impulses away from cell body toward other neurons or things like muscles and glands via **telodendrites **

Question 2

_____ neurons are those that recieve outside stimuli and transmit them toward the brain/spinal cord. _____ neurons are those that conduct impulses away from the brain and spinal cord and their axons take the impulse toward _____ (such as muscles or glands)

Answer 2

Afferent neurons (sensory), efferent neurons (motor), effectors

Question 3

____ neurons can connect afferent and efferent neurons within the gray matter of the spinal cord

Answer 3

Interneurons

Question 4

What are the three major divisions of the nervous system? Describe each

Answer 4

Central nervous system includes the brain and spinal cord
Peripheral nervous system includes cranial (originate from the brain) and spinal nerves (originate from spinal cord as dorsal and ventral root with swellings called ganglia, used to transmit sensory information from receptors of the body to the CNS)
Autonomic nervous system (primarily functions in unconscious tasks such as heartbeat, lung ventilation, etc.

Question 5

Describe the classes of receptors.
What are the effectors?

Answer 5

Divided into general and special receptors.
General receptors break down into somatic (perceive pain, touch, temperature as well as contraction and placement of muscles) and visceral (pertaining to the feeling of fullness, thirst, hunger.
Special receptors are those in the head region including vision, taste, hearing, smell, and balance. These are also divided into somatic (Sight, hearing, baland) and visceral (taste, smell).
Effectors are muscles and glands that respond to stimuli provided by receptors

Question 6

Describe the naris and olfactory sac of the shark

Answer 6

The naris has two openings, the lateral (and small) incurrent aperture and the medial excurrent aperture (the larger one). Water flows in through the incurrent, into the olfactory sax, then out through the excurrent.
The interior of the sac contains highly folded olfactory lamellae (covered in olfactory neurons) which provide a large surface area for smell

Question 7

Describe the neuromast of the lateral line system

Answer 7

Neuromasts contain hair cells, which are composed of numerous stereocilia and a single kinocilium within a cupula

Question 8

Describe the tunics of the eye as well as the lens

Answer 8

Fibrous tunic - Front is transparent and known as cornea, and the back is whitish and known as sclera. Fibrous tunic is covered in a loose layer of epithelium known as conjuctiva
Vascular tunic - The middle layer is a pigmented layer known as the coroid (forms blackish layer at the back of the eye), and becomes modified as the iris at the front of the eye, which controls the amount of light coming into the eye
The lens is highly curved and is held in place by the ciliary body (black layer extending from coroid), but is also held in place by gelatinous material known as vitrious body
Retina is the final layer, containing sensory cells responsible for sight, and the sensory information is conveyed via the optic nerve at the back of the eye

Question 9

Name the structures labelled in this picture

Answer 9

A - Dorsal oblique
B - Ventral oblique
C - Ventral rectus
D - Lateral rectus
E - Medial rectus
F - Dorsal rectus

Question 10

What are the structures of the eye labelled in this picture?

Answer 10

A - Vitreous humor
B - Lens
C - Iris

Question 11

The membranous sacs and ducts of the inner ear are collectively referred to as the ______

Answer 11

Membranous labyrinth

Question 12

The membranous labyrinth is filled with a fluid called _____ and floats in a fluid called ______

Answer 12

Endolymph, perilymph

Question 13

Briefly describe the structure and function of the inner ear

Answer 13

It consists of three semicircular ducts , two vertical and one horizontal. These each bear a swelling called an ampulla at their ventral attachment. The ampullae contain sensory organs called cristae (really just neuromasts). The semicircular ducts detect rotational movements in space. The sacculus and utriculus each contain a macula for detecting the position of the head. In the macula is a bed of crystals (referred to as an otilith) on top of cristae. This is the main mechanism used to detect acceleration

Question 14

Name the structures labelled in the picture

Answer 14

A - Posterior vertical semicircular duct
B - Anterior vertical semicicular duct

Question 15

Name these structures within the brain. What is the function of structure E?

Answer 15

A - Olfactory sac
B - Olfactory bulb
C - Olfactory tract
D - Cerebral hemispheres
E - Telachordia - secretes spinal fluid
F - Optic lobes
G - Oracle of the cerebellum
H - Body of cerebellum

Question 16

Name and describe the “thalamuses”. In which area of the brain are they located? What is the final part of this area of the brain?

Answer 16

Epithalamus - Roof of diencephalon - contains an olfactory centre and pineal eye homologue
Thalamus - Side walls of diencephalon - relay centre between parts of brain
Hypothalamus - Floor of diencephalon - regulates sleep, hunger, thirst, gut activity, digestion, sexual activity, blood sugar levels, water and salt levels, etc.
The roof of the diencephalon is the tela choroidea, which secretes cerebrospinal fluid

Question 17

Name the sections of the dogfish brain

Answer 17

A - Telencephalon
B - Diencephalon
C - Mesencephalon
D - Metencephalon
E - Myelencephalon

Question 18

Describe, in detail, cranial nerve X

Answer 18

X Vagus nerve - Several branches. Visceral branch services branchial pouches 2-5. Visceral branch becomes intestinal branch as it enters pleuroperitoneal cavity. Lateral branch lies between epaxial and hypaxial musculature. When occipital nerves and first several spinal nerves unite, it;s called the hypobranchial nerve

Question 19

Name these nerves (including numbers)

Answer 19

A - Superficial ophthalmic nerve (combination of Trigeminal V and Facial VII)
B - Trigeminal V
C - Glossopharyngeal IX
D - Vagus nerve X

Question 20

Name these nerves

Answer 20

A - Trochlear IV
B - Superficial ophthalmic nerve

Question 21

Name these nerves (and maybe muscles). What are the two branches of D?

Answer 21

A - Optic nerve II
B - Occulamotor nerve III
C - Hyomandibular branch of Facial nerve VII
D - Infraorbital nerve (branches are maxillary from trigeminal V and buccal from facial VII)
E - Preorbitalis

Question 22

Name and describe nerves I-IV and VI

Answer 22

I Olfactory nerve - very hard to see, takes sensory impulses from olfactory bulb
II Optic nerve - thick white nerve that attaches to the back of the eye
III Oculomotor nerve - innervates 4/6 extrinsic eye muscle, thin yellowish strand seen from ventral view of eye
IV Trochlear nerve - Thin nerve. Heads to dorsal oblique in eye from large superficial ophthalmic
VI Abducens nerve - Feeds lateral rectus

Question 23

Describe, in detail, nerve V and its branches

Answer 23

V - Trigeminal nerve - has several branches. Superficial ophthalmic branch is made of both nerve V and nerve VII, heads through dorsal orbit to the rostrum. Deep ophthalmic branch is a small nerve passing through the orbit. Maxillary branch gives way to infraorbital nevre (just below orbit, by the preorbitalis). Mandibular branch is thick and located at the back of the orbit.

Question 24

Name and describe nerves VII to IX

Answer 24

VII Facial nerve - Has several branches, two of which travel with nerve V: Superficial opthalmic branch and buccal branch. Hyomandibular branch is associated with the hyoid arch, right by the levator hyomandibulae
VIII Vestibulocochlear nerve - Runs from sacculus to posterior vertical semicircular duct
IX Glossopharyngeal nerve - Services first gill pouch. Has pre-trematic and post-trematic branches