midbrain and diencephalon

Question 1

midbrain components

Answer 1

sensory and motor areas, cranial nerve nuclei, long range fibre tracts, substantia nigra,

Question 2

diencephalon components

Answer 2

thalamus, subthalamus, epithalamus, hypothalamus

Question 3

midbrain functions

Answer 3

motor movement - particularly the eye, auditory processing, visual processing

Question 4

development of midbrain

Answer 4

alar plates - migrate to form superior & inferior colliculi, substantia nigra and red nucleus, basal plates - migrate to form two ocular nuclei (general somatic efferent) and two edinger-westphal nucleus (general visceral efferents)

Question 5

midbrain

Answer 5

tectum - lies posterior to cerebral aqueduct, tegmentum - base of tectum to (not including) substantia nigra, basis pedunculi - anterolateral section-substantia nigra and crus cerebri (primary depending pathway)

Question 6

midbrain ventral surface

Answer 6

rostral limit to midbrain - exit of crura cerebri from cerebral hemishpheres, and by casual limit of mammillary bodies, caudal limit to midbrain - formed where each crus enters pons

Question 7

tectum

Answer 7

rear portion of midbrain formed by pair of round swellings, superior colliculi - receives visual, auditory and somatosensory inputs that are in register with motor outflow-these refer to the point of origin of the stimulus, produces motor response that orientates the head and eyes towards the stimulus (tectospinal pathway - midbrain, pons, medulla, cervical cord), inferior colliculi - receives auditory input from hindbrain structures, sends auditory information to superior colliculi and thalamus

Question 8

tegmentum

Answer 8

infant of tectum, consists of fibre tracts and 2 regions distinguished by colour, red nucleus - coordination of sensorimotor information, pre-aqueductal grey - involved in pain suppression

Question 9

anterior midbrain

Answer 9

red nucleus - high iron content, motor nucleus associated with cerebellum (parvocellular pathway) and spinal cord (magnocellular pathway)

Question 10

posterior midbrain

Answer 10

midbrain locomotor areas (mesencephalic locomotor region) - stimulates pattern generator in spinal cord to initiate locomotion, regulates pattern and speed of locomotion

Question 11

periaqueductal grey

Answer 11

made of great matter few myelinated axons, pain suppression die to naturally high endorphins

Question 12

basal pedunculi

Answer 12

in front of tegmentum, fibre tracts and 2 regions distinguished by colour, substantial nigra - large pigmental cluster that contains dopaminergic neurones, crus cerebri - consists of neurones that connect the cerebral hemispheres to cerebellum

Question 13

substantia nigra pars compacta (SNC)

Answer 13

rich in melanin, use dopamine as neurotransmitter, project to striatum (caudate nucleus and putamen)

Question 14

ventral tegmental area (VTA)

Answer 14

projects to frontal cortex (mesocortical pathway) - higher cortical functions: memory, emotion an thought, projects to ventral striatum (mesolimbic pathway) - arousal, locomotor activity, reward and motivational, inhibiting dopamine neurones in VTA causes depression like symptoms in mice

Question 15

disorders linked to dopamine systems

Answer 15

SNC to striatum - Parkinson’s disease, VTA to ventral striatum - drug addiction, OCD, ADHD, VTA to frontal cortex - schizophrenia

Question 16

ocularmotor nerve (3rd cranial nerve)

Answer 16

somatic motor and viceral motor components, somatic efferent to extra ocular muscles, visceral to sphincter and ciliary muscles, medial longitudinal fasciculus - vestibular input to cranial nerve nuclei 3, 4 and 6

Question 17

trochlear nerve (4th cranial nerve)

Answer 17

controls superior oblique muscle, crossed pathway, only cranial nerve to exit from dorsal surface of CNS

Question 18

abducens nerve (6th cranial nerve)

Answer 18

abducens nucleus is in the hindbrain, controls lateral rectus muscle

Question 19

diencephalon

Answer 19

thalamus - relay sensory and motor signals to cerebral cortex to regulate consciousness, sleep and alertness, subthalamus - receives afferents from striatum and substantia nigra to regulate skeletal muscle movements, epithalamus - some functions of its components include secretion of melatonin by pineal gland and regulation of motor pathways and emotions, hypothalamus - controls body temperature, hunger, thirst, energy, balance, fatigue, sleep, circadian cycles

Question 20

other structures of diencephalon

Answer 20

reticular nucleus - GABAergic input to thalamus; brain wave activity, subthalamic nucleus - basal ganglia; motor control

Question 21

subthalamic nucleus

Answer 21

ultimate processing centre of movement, emotion and cognitive nerve signals-almost everything the body needs to live, serves as primary connection between midbrain and diencephalon, subthalamic cells have been found to be inactive majority of the time, cessation of inhibition results in hyperactivity of not only subthalamic cells but the globus pallidus as well-key trait in parkings’s disease (deep brain stimulation)

Question 22

epithalamus

Answer 22

small region of diencephalon consisting of: pineal gland - contains no true neurones only glial cells and pinealocytes (produce melatonin), through complicated process involving melatonin it participates in regulation of circadian rhythms, habenular nuclei - main integrator area of olfactory, somatic and visceral afferent pathways, medial and lateral nuclei connected by commissure, stria medullaris - conveys input to both habenular nuclei, the habenular commissure a small bundle of fibres riding the upper edge of the posterior commissure, connects the habenular regions of the two sides

Question 23

suprachiasmatic nucleus (SCN) and circadian rhythm

Answer 23

bilateral structure located in anterior part of hypothalamus, central pacemaker of circadian timing system and regulates most circadian rhythms in the body