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===Limbic System===

===Limbic System===

The Limbic system is made up of parts of the brain bordering the '''corpus collosum'''. The Limbic system contains areas of '''cerebral cortex''', the '''cingulate gyrus''' (dorsally), the '''parahippocampus gyrus''' (ventrally), the '''amygdala''', parts of the '''[[Hypothalamus - Anatomy & Physiology|Hypothalamus Anatomy and Physiology]]''' (mamillary body) and the '''hippocampus'''. The limbic system is principally responsible for emotions and the various types of emotion can affect the activity of the '''[[Autonomic_Nervous_System_-_Anatomy_%26_Physiology|Autonomic Nervous System]]''', facilitated by the [[Hypothalamus - Anatomy & Physiology|hypothalamus]].

The Limbic system is made up of parts of the brain bordering the '''corpus collosum'''. The Limbic system contains areas of '''cerebral cortex''', the '''cingulate gyrus''' (dorsally), the '''parahippocampus gyrus''' (ventrally), the '''amygdala''', parts of the '''[[Hypothalamus - Anatomy & Physiology|Hypothalamus Anatomy and Physiology]]''' (mamillary body) and the '''hippocampus'''. The limbic system is principally responsible for emotions and the various types of emotion can affect the activity of the '''[[Autonomic_Nervous_System_-_Anatomy_%26_Physiology|Autonomic Nervous System]]''', facilitated by the [[Hypothalamus - Anatomy & Physiology|hypothalamus]].

===Olfactory Bulb===

===Olfactory Bulb===

The olfactory bulb is responsible for olfaction and the bulb itself is located within the rostral forebrain area, supported by the ''cribiform plate'' and the ''ethmoid bone''. The [[Equine Cranial Nerves - Horse Anatomy|olfactory nerves]] are connected directly to the limbic system. As a result, olfaction plays a central role and is particularly important in regulating/stimulating sexual behaviour.

The olfactory bulb is responsible for olfaction and the bulb itself is located within the rostral forebrain area, supported by the ''cribiform plate'' and the ''ethmoid bone''. The [[Equine Cranial Nerves - Horse Anatomy|olfactory nerves]] are connected directly to the limbic system. As a result, olfaction plays a central role and is particularly important in regulating/stimulating sexual behaviour.

==Midbrain==

==Midbrain==

The midbrain or mesencephalon represents the connection between the [[Hindbrain - Anatomy & Physiology#Hind Brain Structures & Functions|brain stem]] and the higher centres of the brain and is involved in most body systems including '''sleep/consciousness, vision, hearing and temperature regulation'''.  

The midbrain or mesencephalon represents the connection between the [[Hindbrain - Anatomy & Physiology#Hind Brain Structures & Functions|brainstem]] and the higher centres of the brain and is involved in most body systems including '''sleep/consciousness, vision, hearing and temperature regulation'''.  

The midbrain is located between the diencephalon and the hind brain, or brain stem. More specifically, it can be found ventral to the [[Cerebrum|cerebral cortex]] and between the cerebral pedicles of the diencephalon and the pons. It is a relatively short portion of the upper brain stem and connects higher brain centres with the lower centres and spinal cord.  

The midbrain is located between the diencephalon and the hind brain, or brainstem. More specifically, it can be found ventral to the [[Cerebrum|cerebral cortex]] and between the cerebral pedicles of the diencephalon and the pons. It is a relatively short portion of the upper brain stem and connects higher brain centres with the lower centres and [[Equine Spinal Cord - Horse Anatomy|spinal cord]].  

The midbrain has a stratified structure comprising various layers including the '''tectum, tegmentum '''and '''cerebral peduncle'''. These structures are found in a dorsoventral sequence. The tectum lies dorsally to the cerebral aqueduct and it has four major rounded surface swellings; colliculi (see below). The tegmentum is the core of the midbrain and a large proportion of it is made up by the [[Sensory Pathways - Anatomy & Physiology#Ascending Reticular Formation (Spinoreticular Tract)|reticular formation]].

The midbrain has a stratified structure comprising various layers including the '''tectum, tegmentum '''and '''cerebral peduncle'''. These structures are found in a dorsoventral sequence. The tectum lies dorsally to the cerebral aqueduct and it has four major rounded surface swellings; colliculi (see below). The tegmentum is the core of the midbrain and a large proportion of it is made up by the [[Sensory Pathways - Anatomy & Physiology#Ascending Reticular Formation (Spinoreticular Tract)|reticular formation]].

===Cranial Nerve Nuclei===

===Cranial Nerve Nuclei===

The major cranial nerve nuclei within the midbrain are the mesencephalic nuclei of the [[Cranial Nerves - Anatomy & Physiology|trigeminal nerves (V)]], the trochlear nuclei (IV), the principle and parasympathetic oculomotor nuclei [[Cranial Nerves - Anatomy & Physiology|(Cranial Nerve III)]], the 'red nuclei' (so named due to its pronounced vascularity) and the periaqueductal grey nuclei. The periaqueductal grey nucleus is a core of grey nervous tissue located adjacent to the cerebral aqueduct. The oculomotor nerve emerges from the mid brain rostral to the pons.

The major [[Equine Cranial Nerves - Horse Anatomy|cranial nerve]] nuclei within the midbrain are the mesencephalic nuclei of the [[Cranial Nerves - Anatomy & Physiology|trigeminal nerves (V)]], the trochlear nuclei (IV), the principle and parasympathetic oculomotor nuclei [[Cranial Nerves - Anatomy & Physiology|(Cranial Nerve III)]], the 'red nuclei' (so named due to its pronounced vascularity) and the periaqueductal grey nuclei. The periaqueductal grey nucleus is a core of grey nervous tissue located adjacent to the cerebral aqueduct. The oculomotor nerve emerges from the mid brain rostral to the pons.

===Cerebral Aqueduct===

===Cerebral Aqueduct===

Within the lumen of the midbrain lies the cerebral aqueduct, which acts as a simple passage between the spinal cord and the third and fourth ventricles.

Within the lumen of the midbrain lies the cerebral aqueduct, which acts as a simple passage between the spinal cord and the third and fourth ventricles.

The caudal colliculi are widely spaced and are joined by a substantial commissure. The caudal colliculi act as '''integration centres for auditory pathways'''. The caudal colliculi also have a further connection to the thalamus via the ipsilateral '''medial geniculate body'''. This body is effectively a swelling of the [[thalamus]].  

The caudal colliculi are widely spaced and are joined by a substantial commissure. The caudal colliculi act as '''integration centres for auditory pathways'''. The caudal colliculi also have a further connection to the thalamus via the ipsilateral '''medial geniculate body'''. This body is effectively a swelling of the [[thalamus]].  

====Rostral Colliculi====

====Rostral Colliculi====

The rostral colliculi are placed closer together in comparison to the caudal. The rostral colliculi are also joined to the thalamus, but by the '''lateral geniculate bodies''' rather than the medial. The rostral colliculi help to '''integrate the visual pathways''' and also are involved in '''somatic reflexes''' that are caused by visual cues. The rostral colliculi have also been suggested to be involved in spatial integration.

The rostral colliculi are placed closer together in comparison to the caudal. The rostral colliculi are also joined to the [[thalamus]], but by the '''lateral geniculate bodies''' rather than the medial. The rostral colliculi help to '''integrate the visual pathways''' and also are involved in '''somatic reflexes''' that are caused by visual cues. The rostral colliculi have also been suggested to be involved in spatial integration.

===Substantia Nigra===

===Substantia Nigra===

The substantia nigra is a prominent area of the mid brain and is identifiable on cross sections by its darker pigmentation. This pigmentation is due to the gradual accumulation of pigmentation of neurons and is associated with basal nuclei within the tissue. The '''substantia nigra''' nuclei are involved in the '''control of voluntary movement'''.

The substantia nigra is a prominent area of the mid brain and is identifiable on cross sections by its darker pigmentation. This pigmentation is due to the gradual accumulation of pigmentation of neurons and is associated with basal nuclei within the tissue. The '''substantia nigra''' nuclei are involved in the '''control of voluntary movement'''.

===Crura Cerebri===

===Crura Cerebri===

These are visible on the ventral surface of the mid brain and consist of fibre tracts that are in passage between the telencephalon and the brain stem. The oculomotor nerves (see above) also emerge in this region of the mid brain, directly rostral to the pons.

These are visible on the ventral surface of the mid brain and consist of fibre tracts that are in passage between the telencephalon and the brainstem. The [[Equine Cranial Nerves - Horse Anatomy#Oculomotor Nerve (III)|oculomotor nerves]] (see above) also emerge in this region of the mid brain, directly rostral to the pons.

==Hindbrain==

==Hindbrain==

[[File:Brain sagittal section stem highlighted.svg|thumb|right|300px|Brain sagittal section stem highlighted]]

[[File:Brain sagittal section stem highlighted.svg|thumb|right|300px|Brain sagittal section stem highlighted]]

The hind brain is also called the '''[[CNS Development - Anatomy & Physiology#Development of the Brain|rhombencephalon]]''', it provides the connection between the spinal cord and the rest of the brain. The hindbrain contains many vital structures including the '''Medulla Oblongata''', the '''Pons''' (the link between the cerebellum, forebrain and mid-brain) and the majority of the [[Cranial Nerves - Anatomy & Physiology|'''cranial nerves''']] III to XII. In general the brain stem governs essential functions that are carried out sub-consciously via reflexes.  As well as containing numerous cranial nerves, the hind brain also contains many ''''extra-pyramidal pathways'''' which include the '''reticular formation''', the '''olivary nucleus''' and the '''pontine nuclei'''. Nuclei within the hindbrain are also responsible for the '''reflexive control of posture and eye movement'''.

The hind brain is also called the '''[[CNS Development - Anatomy & Physiology#Development of the Brain|rhombencephalon]]''', it provides the connection between the [[Equine Spinal Cord - Horse Anatomy|spinal cord]] and the rest of the brain. The hindbrain contains many vital structures including the '''Medulla Oblongata''', the '''Pons''' (the link between the cerebellum, forebrain and mid-brain) and the majority of the [[Equine Cranial Nerves - Horse Anatomy|'''cranial nerves''']] III to XII. In general the brainstem governs essential functions that are carried out sub-consciously via reflexes.  As well as containing numerous [[Equine Cranial Nerves - Horse Anatomy|cranial nerves]] , the hindbrain also contains many ''''extra-pyramidal pathways'''' which include the '''reticular formation''', the '''olivary nucleus''' and the '''pontine nuclei'''. Nuclei within the hindbrain are also responsible for the '''reflexive control of posture and eye movement'''.

The '''reticular formation''' is a diffuse interconnection of neurons running throughout the brainstem receiving  both sensory and motor nerve tracts. This information is then passed on to higher centres in the brain such as the [[cerebrum]]. One important aspect of the reticular formation is that in order to transition from sleep to consciousness, the reticular formation is required to activate the cerebral cortex (ascending reticular activating system). It also contains '''cerebellar pathways''' and peduncles facilitating a connection from the brain stem to the cerebellum. There are also a number of ''''pyramidal pathways'''' and afferent pathways including the '''cuneate''' and '''gracile''' pathways.

The '''reticular formation''' is a diffuse interconnection of neurons running throughout the brainstem receiving  both sensory and motor nerve tracts. This information is then passed on to higher centres in the brain such as the [[cerebrum]]. One important aspect of the reticular formation is that in order to transition from sleep to consciousness, the reticular formation is required to activate the cerebral cortex (ascending reticular activating system). It also contains '''cerebellar pathways''' and peduncles facilitating a connection from the brain stem to the cerebellum. There are also a number of ''''pyramidal pathways'''' and afferent pathways including the '''cuneate''' and '''gracile''' pathways.

The generalised function of the cerebellum is to receive information regarding any '''movement''' in progress or any intended movement via inputs from the muscles, vestibular system and motor centres of the pyramidal and extrapyramidal systems. The most important function of the cerebellum is to minimise the difference between the intended and the actual movements. The cerebellum then projects corrections regarding these movements to all motor centres of the brain via feedback circuits between the pyramidal and extrapyramidal systems. It should be noted that the cerebellum '''cannot initiate movement'''.

The generalised function of the cerebellum is to receive information regarding any '''movement''' in progress or any intended movement via inputs from the muscles, vestibular system and motor centres of the pyramidal and extrapyramidal systems. The most important function of the cerebellum is to minimise the difference between the intended and the actual movements. The cerebellum then projects corrections regarding these movements to all motor centres of the brain via feedback circuits between the pyramidal and extrapyramidal systems. It should be noted that the cerebellum '''cannot initiate movement'''.

==References==

==References==

{{citation|initiallast = Dyce|initialfirst = K.M|2last = Sack|2first = W.O|finallast = Wensing|finalfirst = C.J.G|year = 2002|title = Textbook of Veterinary Anatomy|ed =3rd|city = Philadelphia|pub = Saunders}}

{{citation|initiallast = Dyce|initialfirst = K.M|2last = Sack|2first = W.O|finallast = Wensing|finalfirst = C.J.G|year = 2002|title = Textbook of Veterinary Anatomy|ed =3rd|city = Philadelphia|pub = Saunders}}