Exercise Dissection of the Sheep Brain Flashcards | Easy Notecards
A virtual sheep brain dissection guides anatomy studies with photos & blank diagrams. Also shop complete dissection kits: guide, tools & preserved specimen. Human behavior and motor control is typically controlled by the cerebellum, and a sheep's brain has a much smaller cerebellum than the. Use the labeled picture to identify the corpus callosum, medulla, pons, midbrain, and the place where Hypothalamus and pituitary gland anatomy in the human brain extremely basic brain map, Link to Kim Gaynor for SLP websites!.
The hemispheres are connected by five commissures that span the longitudinal fissurethe largest of these is the corpus callosum. There are many small variations in the secondary and tertiary folds. These areas are distinctly different when seen under a microscope. The primary sensory areas receive signals from the sensory nerves and tracts by way of relay nuclei in the thalamus.
Primary sensory areas include the visual cortex of the occipital lobethe auditory cortex in parts of the temporal lobe and insular cortexand the somatosensory cortex in the parietal lobe.
The remaining parts of the cortex, are called the association areas.
These areas receive input from the sensory areas and lower parts of the brain and are involved in the complex cognitive processes of perceptionthoughtand decision-making. The temporal lobe controls auditory and visual memorieslanguageand some hearing and speech. Below the corpus callosum is the septum pelluciduma membrane that separates the lateral ventricles.
Beneath the lateral ventricles is the thalamus and to the front and below this is the hypothalamus. The hypothalamus leads on to the pituitary gland. At the back of the thalamus is the brainstem. Below and in front of the striatum are a number of basal forebrain structures.
These include the nucleus accumbensnucleus basalisdiagonal band of Brocasubstantia innominataand the medial septal nucleus. These structures are important in producing the neurotransmitteracetylcholinewhich is then distributed widely throughout the brain. The basal forebrain, in particular the nucleus basalis, is considered to be the major cholinergic output of the central nervous system to the striatum and neocortex.
- Comparative Anatomy of the Horse, Ox, and Dog The Brain and Associated Vessels
- Difference Between Human and Sheep Brain
Cerebellum Human brain viewed from below, showing cerebellum and brainstem The cerebellum is divided into an anterior lobea posterior lobeand the flocculonodular lobe.
Brainstem The brainstem lies beneath the cerebrum and consists of the midbrainpons and medulla. It lies in the back part of the skullresting on the part of the base known as the clivusand ends at the foramen magnuma large opening in the occipital bone.
In the horse, the ganglion is located dorsal to the foramen lacerum; in the ox, it sits dorsal to the foramen ovale; and in the dog, it is contained within the trigeminal canal of the petrous temporal bone. More limited information is available in the ox. The trigeminal motor nucleus is located within the pons, and the afferent nucleus of the trigeminal nerve, which receives primary afferent projections, is positioned lateral to the motor nucleus as a column running through the mesencephalon, metencephalon, and myelencephalon and within the cranial cervical spinal cord.
The lacrimal branch in all species contains associated postganglionic parasympathetic fibers from the pterygopalatine ganglion that distribute to the lacrimal gland. The lacrimal nerve also contains general somatic afferents that provide sensation to the lateral superior eyelid in the ox and horse; in the dog, this nerve does not innervate facial skin.
Oxen lack an alar canal; therefore, the foramen orbitorotundum acts as the egress point for the maxillary nerve in this species. In the horse, the mandibular nerve exits the calvaria by way of the foramen lacerum; in the ox and dog, egress is through the foramen ovale. The auriculotemporal nerve carries sensory input from the medial ear, temporal area, and, in the horse, portions of the guttural pouch.
It also carries special somatic afferent fibers that have cell bodies located in the geniculate ganglion of the facial nerve and that convey taste information. The facial nerve contains general somatic efferent fibers that innervate muscles of facial expression and the caudal digastricus; general somatic afferent fibers that supply the inner surfaces of the pinnae; general visceral efferent parasympathetic fibers that go to select salivary glands, the lacrimal gland, and the nasal gland; and special visceral afferent fibers that are responsible for taste in the rostral two-thirds of the tongue.
The vestibulocochlear nerve contains special somatic afferent fibers that project from the vestibular apparatus and cochlea. The nerve exits the calvaria via the internal acoustic meatus.
Similarities and Differences of by Alex Joseph on Prezi
Both species seem to have lower thresholds for high-frequency sound compared with low-frequency sound, with normal latency of auditory evoked potentials only determined in the horse. In the horse, ox, and dog, the nerve exits the calvaria via the jugular foramen.
After exiting the jugular foramen, it reaches extracranial structures by coursing through the tympanoccipital fissure.
The vagus, accessory, and hypoglossal nerves are very similar in the horse, dog, and ox. The vagus nerve contains general visceral efferent parasympathetic fibers that innervate the heart and gastrointestinal system, general somatic efferent fibers pharynx, larynxgeneral somatic afferent fibers nonosseus external acoustic canalgeneral visceral afferent fibers gastrointestinal system, lungsand special visceral afferent fibers to convey taste from the epiglottis.
It supplies, in part, the sternocephalicus, omotransversarius, and brachiocephalicus muscles in all species discussed here. The Guttural Pouch Guttural pouch mycosis is the third most common upper respiratory condition of the horse and the only disease of the guttural pouch that consistently causes neurologic signs.
The guttural pouch is a ventral diverticulum of the auditory tube found only in horses Figure 3. It is bounded by the sphenoid and occipital bones and atlas dorsally, the pharynx and esophagus ventrally, and the pterygoids, parotid salivary gland, and mandibular salivary gland laterally. Cerebrovascular accidents strokesseptic emboli, and pituitary abscesses all result from lesions within blood vessels.
Dissemination of neoplasia and infection also depends on vascular anatomy. Cerebrovascular accidents not resulting from infection are rarely reported in large animals. In other species, animals with stroke present with acute-onset, lateralized central nervous system signs that may resolve with time. Septic emboli are probably the most common cause of central nervous system vasculopathy in oxen and represent a subclassification of cerebrovascular accident.
The caudally directed basilar artery flow of the ox may lead to patterns of embolization in this species that are altered compared with those of the dog and horse. Blood flow is also important in generating pituitary abscesses. Oxen may be more frequently affected than other species due to their complex rete mirabile discussed below. The ventral spinal artery and the vertebral arteries contribute to the basilar artery; however, in the dog, the occipital anastomoses of the vertebral supply to the basilar artery are small.
The internal carotid artery is particularly large, distributing blood to all but the most caudal portions of the cerebrum. In the ox, this network has interconnected rostral and caudal divisions that are supplied by maxillary and occipital condylar or vertebral artery branches, respectively.
The rostral cerebral artery courses dorsally in the longitudinal fissure to supply the rostromedial portions of the cerebrum. In general, the dorsal system begins at the convergence of several dorsal cerebral veins in the area of the crista galli of the cribriform plate in the rostral fossa. Along its course, it receives cerebral veins, meningeal veins, and diploic veins from the skull.