L7 - The Mammalian Brain Flashcards
What are the 4 main parts of the cerebral hemisphere and what does each do?
1) Thalamus - relay station for sensory information
2) HPA axis - hormonal axis
3) Cerebellum - ‘little brain’ coordinates movement sequences
4) Pons and Medulla - autonomic functions
What is the cerebrum (2 x cerebral hemispheres) appearance in:
a) fish and amphibians
b) birds
c) mammals
a) fish and amphibians = small
b) birds = largish and smooth
c) mammals = large and grooved/creased
How many layers of neurons does the cortex usually have?
6
How much does the average brain weight?
1.2-1.8kg (around 2.1%) of your body mass
What are pyramidal neurons?
Pyramid shaped cell bodied neurons.
They are the most numerous excitory cell type in the cerebrum.
They have hundreds of inputs form excitory (glu) and inhibitory (GABA) synapses
What are spindle neurons?
General quite rare, they are larger modified versions of pyramidal neurons.
Their structure is simpler with fewer dendrites
In a human retina, how many are there of these cell types:
a) rods
b) cones
c) retinal ganglion cells
Human:
a) 120 million rods
b) 5m cones
c) 1.3m retinal ganglion cells
What does ‘receptive field’ mean?
Receptive field of a neuron: area of space within which stimulus causes a response in the neuron
What are:
a) on-centre/off surround RGCs
b) off-centre/on-surround RGCs
a) Some retinal ganglion cells are excited by light to the central part of their receptive field and inhibited by light within the surrounding region. ‘On-centre’.
b) Others are ‘off-centre’.
Opposition between the central part and surround is established by pathways within the retina involving horizontal cells.
Who first found that many neurons in the primary visual cortex respond to lines or edges?
Hubel & Wiesel - 1959 - cortical neuron receptive fields.
What is a ‘mirror neuron’?
Mirror neurons respond both when an animal makes a particular movement or when it sees another do the same action.
Could play a role in animals interpreting each others’ action and intentions
For example in Parma, Italy, in the 1980s:
A brain neuron that spiked vigorously whenever a monkey reached for a peanut as was seen to spike vigorously when the monkey saw another monkey reaching for a peanut
What do neurons in the primary visual cortex respond to?
Lines or edges: specific, vigorous responses.
What are ommatida?
optical units that make up the compound eye of arthropods. Each has its own narrow-angle lens which directs light onto photoreceptor cells. The inner borders of photoreceptors have microvilli that contain rhodopsin and trap light. Axons from these send the light information to the nervous system
What kind of cell does night vision depend mostly on?
Night vision depends mostly on rod cells, this is because cone cells have a low sensitivity to light, therefore vision in dim lights most looks tone of grey
Describe how rod cells give out information if they do not produce APs
Rod cells release NT from their basre wherer they form synapses with the next cell in the visual pathway.
In response to a flash of light, the the plasma membrane of the rod cell, which is packed tightly with rhodopsin, hyperpolerises
