Embryological development and divisions

EMBRYOLOGICAL DEVELOPMENT AND DIVISION

  • 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).
    • 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.
    • 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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  • 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.
    • 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
        • 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: Friday, 11 May 2012, 7:41 AM