18.3. The Brain and its Development Flashcards
Vertebrate nervous system…
Most of the nerves are concentrated within a central region.
This is the primary region for storage and processing.
The CNS is the brain and spinal cord, the level of complexity changing across vertebrates.
Vertebrate brains…
Brain stem: controls basic, autonomic functions (heart rate / breathing).
Cerebellum: integrates sensory and motor movements.
Cerebrum: complex behaviours, emotions, learning and memory. This dominates the brain.
The sizes of regions in the brain vary greatly between organisms.
Shark brain…
Very simple, effectively an autonomic organism. It eats and swims.
It has few complex behaviours, hence little cerebrum.
The brain mainly deals with autonomic function, sensory input and motor response.
Alligator brain…
Slightly more complex, but still very autonomic, hence very little cerebrum.
It has a few more complex behaviours.
Sensory activity is required as it lives in and out of water.
Motor responses can be complex (pulling prey underwater to eat them).
Pig brain…
Starting to take on a more human structure.
Socially aware animals that display personalities and memory.
Highly developed sense of smell (more than humans, hence larger olfactory bulb).
Coordinated and precise motor and sensory systems mean it has a larger cerebrum and cerebellum.
Human brain…
A highly complex brain.
The most prominent area is the cerebrum (as we have high social awareness, emotions, learning and memory).
We are capable of advanced learning and memory and have a complex personality structure.
Also have a highly evolved cerebellum, giving us huge capacity of integration and allowing us to use precise and fine motor skills.
Underdeveloped olfactory bulb, potentially as we are heavily reliant on our other sensory systems:
- But, have we made up for this with integration from other sensory inputs that create a multidimensional perspective of the world?
- This could explain why we don’t need such a developed olfactory bulb, as a single sensory stimuli activates multiple senses at the same time.
Development of the human nervous system…
Start with the neural tube (hollow tube that runs on the dorsal surface of the embryo).
The swelling of the forebrain, midbrain, hindbrain and spinal cord will fold and develop into the main divisions of the CNS.
Telencephalon…
Becomes the cerebrum.
Divided into two halves called hemispheres.
Via the corpus callosum, which helps communication:
- A thick band of nerve fibres.
- 200-250 million axonal projections.
Divided further into grey (cell bodies) and white (mainly axons) matter. Grey matter forms a layer of the brain surface and is highly folded, to allow the cortex to fit into the skull.
Made up of ridges (gyrus) and valleys (sulcus).
Each hemisphere is divided into lobes (elaborate) and has a role in perception, memory, learning and conscious behaviour.
Functions work contralaterally (opposite lobe).
Diencephalon…
Becomes a forebrain relay site.
Hindbrain…
Cerebellum (dorsal outgrowth): intricate control of motor and sensory functions.
Pons and medulla (brain stem): connects the spinal cord to the brain, controlling involuntary movements.
Midbrain…
Also a part of the brain stem.
Has a number of structures associated with sensory inputs, mainly vision and olfaction.
