Download Comparative Anatomy Interactive Notes Set 12

Comparative Anatomy Interactive Notes Set 13
NERVOUS SYSTEM - Chapter 16
- brain is built in accordance with single architectural plan
- same all the way
Primitive State
1. Prosencephalon - forebrain
- smell
2. Mesencephalon - midbrain
- vision
3. Rhombencephalon - hindbrain
- hearing
- Primary Brain Vesicles - subdivided
1. Hindbrain - rhombencephalon
- divided into - Myelencephalon - becomes medulla oblongata
- vagal lobes – prominent in fishes with large
number of taste buds
- Metencephalon - cerebellum - dorsally
- pons - ventrally
- cerebellum - reflex control
- cavity in hindbrain - 4th ventricle
- 3rd ventricle - portion of subdivision of forebrain
- 2 cerebral hemispheres - lateral ventricles
- roof of hindbrain is thin tissue - posterior choroid plexus
- as brain evolves, some parts of brain become enlarged, others are reduced
Hindbrain - myelencephalon - medulla oblongata
- metencephalon - cerebellum
- associated with reflex control of skeletal muscles
- medulla - involuntary reflexes
- roof of medulla - tela choroidea - thin membrane
- tissue that dips into 4th ventricle - posterior choroid plexus
- roof of metencephalon - cerebellum
Midbrain - no further subdivisons
- roof of mesencephalon is a pair of optic lobes
- well developed in birds
- optic reflex centers
- pair of auditory lobes are caudal to optic lobes beginning with reptiles
- when these two lobes are together and present = superior and inferior
colliculi
Superior - optic
Inferior - auditory
- collectively they are they corpora quadrigemina
- ventricle of midbrain (3rd) is large in fish and amphibians
- extends to optic lobe as optic ventricles
- get higher phylogenetically - optic lobes aren’t there and ventricles disappear
- region becomes restricted and represented by passageways cerebral aqueduct or aqueduct of Sylvius
Forebrain - Diencephalon - sagittal view, find optic chiasma
- this is where 2 optic nerves cross - ventral landmark
- marks cephalic boundary at diencephalon
- Pituitary Gland - caudal to optic chiasma
- on ventral floor - thin wall evagination behind the pituitary in some fish - saccus
vasculosus
- deep sea fish, thought to be associate with depth perception
- floor itself is known as hypothalamus
- number of nuclei present
- autonomic nervous system
- walls of diencephalon - thalmus
- cavity inside thalmus - 3rd ventricle
- in lower vertebrates - thalamus is small
- mammals - so large that walls bulge into ventricle almost obliterates the 3rd ventricle
rd
- 3 ventricle - communicates with lateral ventricles of cerebral hemispheres
- connection between the two
- hole there is called foramen of Monro
- roof of diencephalon - Epithalamus
- number of evaginations - simple or complex
- anteriorly there is paraphysis
- there are 2 bulges found in all vertebrates
- pineal and parapineal organs
- together they are the epiphyseal complex
- serve as photoreceptors in lower vertebrates
- parapineal is widely distributed in ancient pineal
-becomes pineal eye - 3rd eye
Telencephalon - anterior Rhombencephalon - forebrain associated with olfaction
- posterior - cerebral hemispheres
- lower vert. - Rhombencephalon is as prominent as hemisphere
- higher vert. -hemispheres increase in size and bulge forward to overtake
Rhombencephalon
Cerebrum of Fish - 2 portions that can be identified
1. Primitive sensory and association area
- dorsal area - Pallium
2. Ventrally - motor area
- Subpallium - Globus pallidus
- 1 term that used to be applied to globus pallidus - Striatum
Cerebrum of Amphibians
- pallium and globus pallidus are similar
- have left and right hemisphere now
- split in amphibians
Cerebrum of Reptiles
-become huge compared to amphibians
- massive increase of lateral wall of each cerebrum
- this has pushed into the lateral ventricle
- Dorsal ventricular ridge
- receives visual, auditory, and somatic sensory stimuli
- increase in muscular complexity
Cerebrum of Bird - basically reptilian
- another stratum of neurons that has capped the ridge
- avian ridge or hyperstriatum
- this processes visual information and it is assumed this region may play
a role in instinctive stereotypic behavior
Ex. Migration, courtship
- one problem - birds aren’t only animals to do this
- fish do this
Cerebrum of Mammals
- walls and roof of lateral ventricles has become greatly expanded
- forms Neocortex
- in humans - 13 billion neurons
- grooves – sulci (sulcus)
- folds – gyri (gyrus)
- portion of primitive brain has been retained
- lies ventral medially
- ancient olfactory pallium called hippocampus
- tucked under temporal lobe
- topographically we find various lobes
- thought that memory storage is associated with hippocampus - not confirmed
- the globus pallidum has been pushed interiorly
- new nuclei have formed interiorly
- together - basal ganglia
- pathological changes in basal ganglia - may see motor disfunction
Ex. Parkinson’s Disease
- pick up cerebral hemispheres - find caudate nucleus
- neocortex - area of higher mental facitilities
CRANIAL NERVES
- 12 in amniotes
- 10 in anamniotes
- now there are at least 25 cranial nerves recognized in craniates
- Amniotes - 12 pairs - know name, number (roman) innervention, and function
Number
Name
Innervation
I
Olfactory
Olfactory Epithelium
II
Optic
Retina
III
Oculomotor
Intrinsic and Extrinsic
Eyeball Muscles
IV
Trochlear
Extrinsic Eye Muscles
V
Trigeminal
Jaw musculature, skin
of face, snout
VI
Abducens
Extrinsic Eye Muscles
VII
Facial
Facial Musculature,
salivary and tear
glands, taste buds
VIII
Acoustic
Vestibular and cochlear
organs
IX
Glossopharyngeal
Pharynx, salivary
glands, taste buds
X
Vagus
Visceral organs of
throat and abdomen,
larynx, pharynx, taste
buds
XI
Spinal Accessory
Sternocleidomastoid
and trapezius muscles
Function
XII
Hypoglossal
-
Tongue, syrinx
terminal nerve is nerve 0 - seldom seen is humans - not see in birds