Term
| What is the midbrain a part of? |
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Definition
| The midbrain is part of the brainstem (midbrain, pons and medulla oblongata). |
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Term
| What is the term 'bulb' used for? |
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Definition
| The term “bulb” is used for nerves originating from or terminating in brainstem, e.g. ‘corticobulbar’. |
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Term
| What nerves come from the midbrain? |
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Definition
| cranial nerves; oculomotor (III) and trochlear (IV) |
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Term
| What tracts does the midbrain conduct? |
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Definition
| ascending and descending tracts |
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Term
| What nuclei is in the midbrain? |
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Definition
| contains nuclei that process visual and auditory information and control reflexes triggered by these stimuli |
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Term
| Therefore, what does the midbrain contain? |
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Definition
- sensory motor area
- cranial nerve nuclei
- long range fibre tracts
- substantia nigra |
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Term
| Where is the diencephalon? |
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Definition
- within the forebrain
- bilaterally paired diencephalon and cerebral hemispheres on each side
- The diencephalon is continuous with the rostral part of the midbrain, lying between the brain stem and the cerebral hemisphere (inferior to the cerebral hemispheres but superior to the midbrain). |
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Term
| What are the parts of the diencephalon from dorsal to ventral? |
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Definition
| epithalamus, thalamus, and hypothalamus. |
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Term
| How do you spot the midbrain? |
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Definition
| spot the dark regions of the substantial nigra |
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Term
| During development, how does the cerebral aqueduct change? |
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Definition
| becomes smaller as cells proliferate and differentiate |
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Term
| What does the tectum differentiate into? |
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Definition
| inferior and superior colliculus |
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Term
| What information does the superior colliculus receive? |
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Definition
receives sensory information; controls the reflex
movements of the eyes, head and neck in response to visual stimuli, such as a bright light. |
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Term
| What information does the inferior colliculus receive? |
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Definition
receives sensory information; controls reflex
movements of the head, neck and trunk in response to auditory stimuli. The inferior colliculus serves as an important relay station for auditory information en route to the thalamus. |
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Term
| In the midbrain, what do the alar plates develop into? |
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Definition
| move down and out to form red nucleus and substantial nigra (there is some controversy and could come from basal plates) |
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Term
| In the midbrain, what do the basal plates develop into? |
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Definition
| Edinger-Westphal nucleus (general visceral efferent) and oculomotor nucleus (general somatic efferent) |
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Term
| What are the 3 main regions of the midbrain? |
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Definition
tectum
tegmenjtum
cerebral peduncle |
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Term
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Definition
| lies posterior to the cerebral aqueduct. |
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Term
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Definition
| the base of the tectum (most anterior part) up to but not including the substantia nigra. |
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Term
| What makes up the cerebral peduncle? |
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Definition
| the tegmentum, crus cerebri and pretectum |
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Term
| What tracts run through the cerebral peduncles? |
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Definition
| The corticospinal tract and the corticobulbar tract have fibers running through the cerebral peduncles. As their names suggest, these are descending pathways. |
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Term
| What are the crus cerebri? |
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Definition
| the anterior portion of the cerebral peduncle which contains the motor tracts. |
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Term
| Where are the colliculi visible? |
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Definition
dorsal surface
4 central round bulbs |
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Term
| What does the superior colliculus receive? |
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Definition
| visual, auditory and somatosensory inputs that are in register with motor outflow - these refer to the point of origin of the stimulus |
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Term
| What does the superior colliculus produce? |
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Definition
| motor response that orientates the head and eyes towards the stimulus |
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Term
| What pathway is therefore associated with the superior colliculus? |
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Definition
tectum region therefore tectospinal pathway
innervates head and neck to enable positioning towards stimulus |
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Term
| What follows a superior colliculus lesion? |
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Definition
| they do not lose complete motor response due to parallel pathways |
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Term
| What does the inferior colliculus receive? |
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Definition
| auditory information from hindbrain structures |
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Term
| What does the inferior colliculus produce? |
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Definition
| auditory information to superior colliculus and thalamus |
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Term
| What follows a inferior colliculus lesion? |
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Definition
| not deaf therefore parallel pathway must be present |
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Term
| Why is the red nucleus red? |
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Definition
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Term
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Definition
| are motor nuclei associated with the cerebellum – they are involved in motor coordination. Issue subconscious motor commands that affect upper limb position and background muscle tone. |
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Term
| What does the midbrain/mesencephalic locomotor region stimulate? |
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Definition
| pattern generator in spinal cord to initiate locomotion |
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Term
| What does the midbrain/mesencephalic locomotor region regulate? |
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Definition
| patter and speed of locomotion |
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Term
| Where is the oculomotor nerve? |
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Definition
The oculomotor nerve leaves the anterior surface of the brainstem between the midbrain and the pons.
major nerve that comes out of the midbrain |
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Term
| What fibres are carried by the oculomotor nerve? |
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Definition
1. General somatic efferent (GSE) fibres which innervate most of the extra-ocular muscles. The oculomotor nucleus gives rise to GSE.
2. General visceral efferent (GVE) fibres which are part oft he parasympathetic section of the autonomic division of the peripheral nervous system. The Edinger-Westphal nucleus gives rise to GVE. |
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Term
| What does the oculomotor nerve control? |
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Definition
| It controls four of the six muscles that move the eye and the muscle responsible for movement of the upper eyelid. |
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Term
| What is the medial longitudinal fasciculus? |
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Definition
| It connects the vestibular nuclei with the following nuclei: (1) oculomotor (2) trochlear, and (3) abducens. |
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Term
| What is the vestibular system? |
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Definition
| contributes to balance in most mammals and to the sense of spatial orientation, is the sensory system that provides the leading contribution about movement and sense of balance. |
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Term
| Where is the trochlear nerve and what does it control? |
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Definition
- only cranial nerve to exit from the surface of the CNS and is therefore susceptible to damage.
- controls superior oblique muscle |
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Term
| Where is the abducens nerve and what does it control? |
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Definition
hindbrain
controls lateral rectus movement |
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Term
| What does the pupillary light reflex control? |
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Definition
the diameter of the pupil, in response to the intensity (luminance) of light that falls on the retina of the eye, thereby
assisting in adaptation to various levels of darkness and light, in addition to retinal sensitivity.
- Greater intensity light causes the pupil to become smaller (allowing less light in).
- Lower intensity light causes the pupil to become larger (allowing more light in).
Thus, the pupillary light reflex regulates the intensity of light entering the eye. |
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Term
| What are the 4 possible outcomes to oculomotor nerve damage on one eye? |
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Definition
1. The ipsilateral direct reflex is lost. (Example: when the left eye is stimulated, only the right pupil constricts)
2. The ipsilateral consensual reflex is lost. (Example: when the right eye is stimulated, only the right pupil constricts)
3. The contralateral direct reflex is intact
4. The contralateral consensual reflex is intact |
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Term
| What causes the contralateral direct reflex to stay intact? |
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Definition
because light shone into both eyes can
still signal to the brain, and the pupil on the undamaged side will still be able to constrict via its normal oculomotor nerve |
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Term
| What causes the contralateral consensual reflex to stay intact? |
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Definition
| because light shone into the left eye can still signal to the brain via the normal optic nerve, causing attempted constriction of both pupils; the contralateral pupil constricts via its normal oculomotor nerve, but the ipsilateral pupil is unable to constrict due to its damaged oculomotor nerve |
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Term
| Where does the substantial nigra and pars compacts project to? |
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Definition
| the striatum, a sub-cortical part of the forebrain consisting of two sections: the caudate nucleus and the putamen (lenticular nucleus). (It is split into these two sections by a white matter tract called the internal capsule). |
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Term
| What is the ventral tegmental area (VTA)? |
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Definition
| The VTA is a group of neurones located close to the midline on the floor of the midbrain. |
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Term
| What is the relevance of the VTA and drug treatment? |
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Definition
| The VTA is the origin of the dopaminergic cell bodies of the mesocorticolimbic dopamine system and is widely implicated in the drug and natural reward circuitry of the brain. It is important in cognition, motivation, drug addiction, intense emotions relating to love, and several psychiatric disorders. The VTA contains neurones that project to numerous areas of the brain, from the prefrontal cortex to the caudal brainstem and several regions inbetween. |
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Term
| Where does the VTA project to? |
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Definition
1. frontal cortex (mesocortical dopaminergic)
2. ventral striatum (mesolimbic dopaminergic) |
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Term
| What disorders are linked to the dopaminergic system from substantia migrants to striatum? |
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Definition
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Term
| What disorders are linked to the dopaminergic system from VTA to ventral striatum? |
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Definition
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Term
| What disorders are linked to the dopaminergic system from VTA to frontal cortex? |
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Definition
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Term
| How do you tell if a mouse is depressed? |
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Definition
tail suspension test
sucrose preference test |
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Term
| How are mice made to be depressed? |
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Definition
| inhibiting dopamine neurones in the VTA |
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Term
| What function does the thalamus serve? |
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Definition
- the thalamus is the final relay point for ascending sensory information that will be projected to the primary sensory cortex.
- It acts as a filter, passing on only a small portion of the arriving sensory information.
- The thalamus also coordinates the activities of the basal nuclei and cerebral cortex by relaying information between them. |
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Term
| Where is the epithalamus and what does it control? |
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Definition
| A dorsal structure of the diencephalon, this is responsible for the regulation of circadian rhythms: anything with a time length of a day. In red, ‘upon the’ thalamus. Some functions of its components include the secretion of melatonin by the pineal gland (involved in circadian rhythms), and regulation of motor pathways and emotions. It is wired with the limbic system and basal ganglia. |
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Term
| Describe the reticular nucleus |
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Definition
| GABAergic input to the thalamus |
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Term
| Describe the subthalamic nucleus |
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Definition
The subthalamic nucleus is a small lens-shaped nucleus in the brain where it is, from a functional point of view, part of the basal ganglia system.
It is involved in motor control. |
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Term
| Where is the hypothalamus? |
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Definition
| inferior to the thalamus. It extends from the area superior to the optic chiasm to the posterior margins of the mammillary bodies. |
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Term
| What are hypothalamic centres stimulate by? |
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Definition
1. sensory information from the cerebrum, brainstem and spinal cord.
2. changes in the compositions of the CSF and interstitial fluid.
3. chemical stimuli in the circulating blood that move rapidly across highly permeable capillaries to enter the hypothalamus (where there is no blood- brain barrier). |
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Term
| What functions does the hypothalamus perform? |
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Definition
- the subconscious control of skeletal muscle contraction.
- the control of autonomic function.
- the coordination of activities of the nervous and endocrine systems.
- the secretion of two hormones:
1. Antidiuretic hormone (ADH) or ‘vasopressin’.
2. Oxytocin (OXT) |
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Term
| Where is ADH produced and what does it do? |
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Definition
| ADH is produced by the supraoptic nucleus and restricts water loss via the kidneys. |
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Term
| Where is OCT produced and what does it do? |
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Definition
| OXT is produced by the paraventricular nucleus and stimulates smooth muscle contractions in the uterus and mammary glands of females and in the prostate gland of males. |
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