Neuromuscular Digestive and Respiratory Systems_ Embryo Logical Development and Divisions

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VPB121: Veterinary Physiology II (2+1)

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development and divisions

EMBRYOLOGICAL DEVELOPMENT AND DIVISION

Embryonic neural tube which is a hollow structure from epithelial origin, develop

into brain and spinal cord.

Brain is derived from anterior portion and spinal cord is divided from posterior

portion of neural tube.

Anterior portion develop into three swellings viz.

Rombencephalon (Hind brain)

Mesencephalon (Mid brain)

Prosencephalon (Fore brain)

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Cavity that develop in the centre is known as ventricles which are filled with

cerebrosipinal fluid (CSF) and ependymal cells, a type of glial cell allow the

circulation of CSF into ventricular and spinal cord due to their ciliary action.

Hind brain controls reflex responses and regulate involuntary behaviour (breathing,

equilibrium, maintenance of body position).

Mid brain is predominantly involved in co-ordinating visual, auditory or sensory

information from mechanoceptors (touch/pressure ) from parts of the body. It acts

as a routing centre.

Fore brain is involved in processing olfactory information, integerates with other

sensory information, regulates body vegetative functions. It is designated to



perform complex tasks like memory processing etc.

Size of the brain varies with body size individual structures type of activity

pertaining to the environment of the animal.

Basal nuclei is the cluster of grey matter situated deep into the brain.

Hind brain: (Pons , Medulla and cerebellum)�

Location: Between spinal cord mid brain. Functions together to support vital body

functions such as respiration cardiac function and movement.

Medulla

Located at the top of the spinal cord

Has centres that control reflex activities such as respiration, heart rate,

vasodilation and blood pressure.

Houses neural pathways that connects cerebral cortex and spinal cord seat of

some of the cranial nerves (9th, 10th and 12th).

Pons

Structures present above the medulla functions as bridging and

communicating informations between medulla, cerebellum and fore brain

structures.

Has neurons that control rate of respiration.

Concerned control of alertness.

Cerebellum

Encased in cerebellar hemisphere and is located in the back of the brain.

Responsible for motor co ordination by integerating sensory inputs from

receptors of muscle, eyes and ears with motor orders of the forebrain.

Maintain Equilibrium and posture.

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Mid brain

Relay centre

Roof of midbrain is known as tectum which has pair of brain centres namely optic

lobes in non mammalian species.

Superior Colliculi is a similiar structure as optic lobes in mammals functions as

reflex optical response (orientation towards visual stimuli, focussing etc).

Tectum has a pair of inferior colliculi which are neurons concerned with hearing.



Tegmentum is the posterior part of midbrain that possess fine control of muscles.

Brain stem is the grouping of midbrain with the pons and medulla.

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Fore brain

Involved in processing and integrating sensory information and co ordinates

behaviour.

Structures of the fore brain consists of cerebrum , thalamus, epithalamus and

hypothalamus.

Cerebrum

Has outer layer known as cerebral cortex which is divided into two cerebral

hemispheres.

Hemispheres excercise control over opposite side of the body.

Hemispheres functions independently of each other.

Two hemispheres are connected by a mass of white matter known as corpus

collosum through which they communicate.

Hypothalamus

Present in the base of the forebrain, below the thalamus.

Maintains homeostasis by controlling internal organs and interacts with

autonomic nervous system.

Regulates endocrine system and links endocrine and neural systems.

Controls vegetative functions of the body.

If forms the part of limbic system which influences emotion and behaviour.

Limbic system is a network of connected structures that lie between the

cortex and reset of the brain.

Structures associated with limbic systems are hypothalamus, amygdala,

hippocampus and olfactory bulbs.

Structures of limbic system

Amygdala

Concerns with emotional responses of fear and aggressiveness.

It is also involved in maintenance of memories of the emotion.

Hippocampus

Structures convert short term memories to long term memories.

Olfactory bulb

Organ of importance for sensing the smell. Behaviours are smell

driven in animals. Sensory neurons from the olfactory epithelium



are connected to the olfactory bulb.

Olfactory information reaches directly here without passing

through thalamus.

Information are transmitted to cortex for processing .

It is connected to amygdala and hippocampus. Emotional

behaviours are mediated through odours in animals and human

beings.

Thalamus

Act as relay centre, largest sensory ganglion of the brain

Has group of grey matter located deep into the forebrain.

Receive all sensory information for upward transmission except olfaction.

Reticular formation is a set of neurons extend from thalamus to brain stem

including pons, medulla and midbrain, that filters incoming sensory

information.

Epithalamus

Located above the thalamus harbours pineal complex, that establishes

circadian rhythm and secretes melatonin.

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Last modified: Thursday, 9 June 2011, 09:40 AM

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Neuromuscular Digestive and Respiratory Systems_ Embryo Logical Development and Divisions