LC 2 - functional systems

Question 1

visual system

Answer 1

• Receptive field of retinas ganglion cells = area of environment that the receptor can perceive (measured in degrees)

o Parvocellular system: small cells, colour, small receptive fields
o Magnocellular system: big cell, no colour, motion, large receptive fields

Question 2

visual brain network

Answer 2

o Projection neurons –> long axons
o Multiple central projections (superior colliculus (optic tectum in other animals), LGB–>V1)
o 55% crossover at optic chiasm (nasal part of retina crosses over)

Question 3

Auditory system

Answer 3

• Longitudinal pressure waves in the air makes eardrum vibrate –> amplified by middle ear bones –> oval window vibration –> longitudinal waves in perilymph of cochlea –> mechanoreceptors (look into the hair cells)
• 8th cranial

Question 4

auditory brain network

Answer 4

1. Projections to medulla (cochlear nucleus) 2. inferior nucleus (tectum, midbrain)
2. thalamus (medial geniculate n.)
3. primary auditory (superior temporal gyrus); has a map of auditory projections just as the cochlea does (in frequencies)

o Some crossing over at the medulla: complicated since there is a visual space map that is computed and a frequency map;
 ITD – inter aural time difference (sound reaches ears at different times, phase locking is used to identify and match the correct sounds and thus to compute ITD)
 ILD – inter aural level difference (sound level based calculation)
 HRTFs - head-related transfer functions (frequency based)

Question 5

chemosensation - taste

Answer 5

• Taste buds (4 areas of different papillae that contain the taste buds)
  o 5 different taste stimuli can be detected by the taste chemoreceptors receptors
  o Cells can respond to multiple taste stimuli the combination of all cells leads to the taste perception
• 7th, facial and 9th nerves also a little bit vagus
  o The neurons that innervate the mouth sit in ganglia right below the temporal lobe and project to medulla (nucleus of solitary tract) –> thalamus –> gustatory cortex (insula) primary taste cortex

Question 6

chemosensation - olfaction

Answer 6

• Olfactory bulb
• Cells sit in epithelium of nerve and their dendrites sense while their axon projects to the olfactory bulb (to the mitral cells of the glomeruli which project to brain –> primary olfactory cortex in temporal lobe – this one goes directly to cortex no thalamus; there is projection to the thalamus tho)

Question 7

somatosensation

Answer 7

• Nociceptors (pain)
• Mechanoreceptors (touch, vibration)
  o 4 types; different stimuli and receptive fields
  o Innervated by axons of nerves that sit in dorsal root ganglia which have axons in dorsal horn of spinal cord
• Proprioception
• From the spinal cord there are pathways that go up to the brain
  o Spinal thalamic tract (pain - spinoreticular, temp, mechano)
  o Anterior thalamic tract (pain, temp, mechano)
  o Dorsal thalamic tract (only mechano)
  o Pain has collateral projections to the reticular formation (open nerve endings no receptors, just like temp: there is hot and cold types tho)

Question 8

limbic system

Answer 8

• Cirle around inside of the brain under the cortex –> papez circuit
• emotional and memory regulation
  o Cingulate gyrus (cortex)
  o Parahippocampal (cortex)
  o Hippocampus
  o Amygdala
  o Also connects to hypothalamus
  o Mammillary
• Various connecting systems between these parts also links endocrine system to sensory system (hypothalamus)

Question 9

papez circuit

Answer 9

1. Hippocampus: The hippocampus is a seahorse-shaped structure located deep within the temporal lobe. It plays a crucial role in the formation and retrieval of new episodic memories, which are memories of specific events or experiences. The entorhinal cortex connect other brain areas to the hippocampus
2. Fornix: The fornix is a bundle of nerve fibers that connects the hippocampus to the mammillary bodies and is essential for transmitting information between these two structures.
3. Mammillary bodies: These are small, paired structures located on the underside of the brain, part of the hypothalamus. They are involved in the processing of spatial memory and are connected to the hippocampus.
4. Mammillothalamic fasciculus, also known as the mammillothalamic tract or mammillothalamic bundle, is a neural pathway in the brain that connects the mammillary bodies to the anterior thalamic nuclei.
5. Anterior thalamic nuclei: These thalamic nuclei serve as relay stations for information between the mammillary bodies and the cingulate cortex, helping to integrate and process memory-related information.
6. Cingulate cortex: The cingulate cortex is a part of the brain’s limbic system and is involved in various functions related to emotion and memory, including decision-making, empathy, and emotional regulation.
7. Cingulum: This is a bundle of white matter fibers that connect the cingulate cortex with other parts of the brain, facilitating communication within the circuit.

Question 10

motor system

Answer 10

• All motor neurons are in ventral horn of spinal cord (can be cervical – t – l – cervical)
  o Somatic (ventral) alfa and gamma
  o Visceral (intermediate horn more dorsal part of ventral horn)
• Look into reflexes/ central pattern generators
• Pyramidal and extra-pyramidal pathways
  o Pyramidal= M1  motor neurons (spinal cord; cross over)  muscle
  o Extra (not voluntary)= M1  reticular formation and red nucleus (incorporates vestibular system and cerebellum)  motor neurons
• Look into basal ganglia (mostly extra pyramidal, but also important for initiation of pyramidal movement) and cerebellum for their motor input

o Don’t have to know the exact mechanism of BG
- Cerebellum incorporates vestibular, proprioceptive and visual info into motor control