Neurophysiology 1 Flashcards
The origins of the brain
are thought to have developed ~1400 MYA
This is when we believe that the first protosynapses developed in single celled organisms
Protosynapses are used for decisions and adaptations to the environment
1462 proteins in the human neocortex PSD (synapse)
~30 in a unicellular protosynapse
Brain size is proportional to synapse complexity
Neuroscience definition
The study of systems that allow organisms to sense and react to the world around them
Even single celled organisms can sense/react to stimuli
e.g. to avoid harmful chemicals, obstacles or extreme cold or heat
Sensory perception of stimulus -> reaction -> adaptation
Trends in evolution of the nervous system
Complexity , centralisation and cephalisation
Skull and vertebral column serve a protective function
Allowing for larger brains and longer spinal cords
Reflex arcs
Intermediate is the simplest form stimulus ->sensory neuron -> effector
Complex reflex arcs involve two or more neurons
e.g. stimulus -> sensory neuron -> integrator neuron -> effector neuron -> effector
The brain can modify the basic reflex arc response aka cephalisation
Or the spinal cord can be used bypassing the brain for a quicker response aka centralisation
Platyhelminths and annelids
Platyhelminths (e.g. Flat worms):
longitudinal nerve cords that coordinate
nervous activity with a peripheral nervous system (PNS)
Anterior ganglia (“brain”) coordinate signals from sensory organs such as eyespots
Bilateral nerve cords send motor signals to effectors located
bilaterally along elongated body
Annelids (e.g. earthworms) :
-CNS with bilobed brain with nerve cord and ganglia in most body segments connecting with separate sensory and motor neurons in PNS.
- Segmental ganglia connected by bundles of axons
- Regionalization - ganglia in each segment coordinate functions of that segment
- One-way conduction
Arthropods
Arthropods
Anterior end animal CNS larger-super ganglion or brain
Evolution trend that the head moves forward so encounters stimulus first.
Ganglia are larger
Generally one ganglion per segment. Each ganglion specialized for the segment and
coordinates regional functions - for the legs, wings, abdomen segments
Decentralized brain function - a decapitated mantis can continue to move
Cephalopods
True CNS is associated with bilateral symmetry
Molluscs have two nerve cords
Several ganglia present on each
nerve cord
Anterior most ganglion fused to
form lobed brain
Cuttlefish
Cephalopod molluscs
Most advanced brains found in cephalopods and ultimately vertebrates
Increase in cephalization of the nervous system
Complex functions such as processing complex sensory
information, learning and memory
Evolution involved adding bits to brain rather than modification of existing structures
Size of bit relates to relative importance of new structures
Visual cortex primates, optic lobe birds reflect importance of visual information
Cephalopods have complex brain structure
Anterior ganglia are enlarged and organized in lobes
Many similarities to vertebrate brain -
a) lobes with complex folds;
b) similar electric wave pattern;
c) distinct regions of the brain are associated with specific functions
d) Specialization in brain hemispheres - favour one eye over the other
e) Protected by skull like structure
Control chromatophores (pigment cells) in the skin - mating, alarm signals, camouflage
Ring brain surrounding the esophagus (not a smart design!)
Some decentralization - Arm cut from animal, if stimulated, can curl around prey
Do butterflies remember being caterpillars?
Yes.
Brain structures called mushroom bodies associated with learning were studied in caterpillars to see if a scent that becomes associated with fear is still feared after the caterpillars pupate. Researchers found this to be the case and that the butterfly retained the fear it had as a caterpillar.
Vertebrate nervous system
see notes for diagram
Afferent – input
Efferent – output
Note: the autonomic nervous system can be impacted by the somatic nervous system
e.g. digestion can be affected by stress
Magawa the rat and Joy Milne
An African Pouched rat named Magawa was capable of sniffing out land mines in Cambodia
(important as these rats are smaller and lighter than sniffer dogs so don’t set off mines
Joy Milne has hereditary hyperosmia allowing her to identify individuals with Parkinsons disease
Vertebrate nervous system: brain : Forebrain (cerebrum)
Cerebrum: Largest portion of the brain.
Two hemispheres connected by the corpus callosum
Cerebral cortex is the outer shell of gray matter (neurons and glial cells) with an inner core of white matter (bundles of myelinated nerve fibres)
Four major functional regions named after the skull bones covering the region
Occipital: Initial processing of visual input
Temporal: Auditory sensation received initially
Parietal: Receiving and processing sensory input
Frontal: Voluntary motor activity, speaking, thought
Regions of the brain are associated with different functions
Motor cortex - somatic motor association area
Auditory cortex - primary auditory cortex + auditory
association area
Sensory cortex - somatic sensory association area
Visual cortex - primary visual cortex + visual
association area
Vertebrate nervous system: brain: cerebellum
Lies underneath the occipital lobe of the cerebral cortex and attached to back of the upper portion of brain stem
Important in
Balance
Voluntary movement
Inputs from visual, auditory, and balance organs are integrated and used for orientation
Motor signals for movement originate in the cerebral cortex. Signals (for balance, fast movement, muscle tone) are coordinated in the cerebellum
Vertebrate nervous system: brain: brain stem
Link between other parts of the brain and the spinal cord
Nerve fibres between the peripheral nervous system and different brain centres synapse in the brain stem region
Functions:
Input of sensation and motor output through cranial nerves (12 pairs)
Reflex control (involuntary) of heart, blood vessels, respiration, digestion
Receives and integrates input from synapses and sends signals to different regions of the cortex
Modulation of pain
Sleep control
Vertebrate nervous system brain summary
(see notes for diagram)
Forebrain
- Cerebrum: Largest part of the brain. Contains the Cerebral cortex, underlying white matter, three deep structures - basal ganglia, amygdala, hippocampus
Most complex area - behaviour and intellect - Diencephalon: Thalamus (Essential in pathway of sensory information from periphery to sensory regions in cerebral hemisphere)
- Hypothalamus (Behaviour, Circadian rhythms)
- Cerebellum
Posture. Coordination of hand, eye, arm
movement. Learning motor skills. Language
Brain stem
- Medulla, Pons, Midbrain.
Oldest region of the brain (evolutionarily)
Mediates sensation and motor control of head neck and face. - Sensory input and motor output carried by 12 cranial nerves. Gets information from hearing, balance and taste.
Effect on cardiac output, blood pressure, gut, peristalsis, pupil constriction.
Carries information to other parts of the CNS.
Regulation of alertness and arousal
Evolutionary newer regions are located on top
Primitive regions lie below:
* Forebrain
* Cerebellum
* Brain stem
Vertebrate/ human brain
Grey matter – contains neural cell bodies
White matter – contains neural processors
Humans have a central sulsus between the two lobes that is also observed in great apes
The pons and the medulla are the most ancient parts of the brain which control basic function.
Damage to these areas has widespread catastrophic impact.
Around the thalamus is a space containing cerebral spinal fluid it is the largest of the brains ventricles known as the ‘lateral ventricle’
2nd largest human brain bank worldwide is located in Newcastle
Functions of brain areas
*Controls movement
*Senses environment and danger
*Processes what you hear
*Processes what you see
*Processes what you smell
*Processes what you feel
*Encodes memories
*Regulates sleep and feeding
*Regulates autonomic physiology
*Controls who you are & your behaviour
Adjusting feeding times can cause alzheimers type symptoms e.g. affecting cortisol levels
This is useful as alzheimers only occurs in humans so mimicking these symptoms allows scientists to use non-human subjects to study it.
Brain slicing terminology
Brain slices can be taken:
coronially (across the middle)
horizontally
sagittally (front to back)
