The brain - Dr Ronnie Chen PDF

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Notes from a lecture by Dr Ronnie Chen for the 'Central Nervous System' part of the course. Lectures given in Cycle 3 on the 18th February 2020. ...

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Dr Ronnie Chen

18/02/2020

THE BRAIN 

The brain is a mass of 100 billion neurones which interpret info obtained from the senses to monitor & regulate the body, as well as being responsible for thinking, learning, memory, and emotion

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There are 4 main brain regions

Cerebrum The largest portion of the brain; split into 2 hemispheres connected by the corpus callosum. The hemispheres are each divided into 3 regions – superficial cortex of grey matter, internal white matter & the basal nuclei (islands of grey matter found deep within white matter). *BASAL NUCLEI/GANGLIA* A set of nuclei deep within white matter. Includes the caudate nucleus, putamen, Globus pallidus & substantia nigra. It regulates voluntary movement, provides subconscious control of skeletal muscle tone & other somatic motor activities (e.g. slow stereotypic activities, such as walking). Responsible for many things: - Thought - Intelligence - Language - Memory - Senses - Self-awareness - Communication - Recognition Sensory areas allow for conscious recognition of stimuli. These are found in the parietal, occipital, and temporal lobes. Association areas allow for the analysis of this sensory input. These are the prefrontal cortex, language areas, general interpretation area & the visceral association area.

Diencephalon This forms the central core of the fore brain; contains 3 paired structures (all are grey matter): - THALAMUS 80% of the diencephalon; the sensory relay station where sensory signals can be edited, sorted & routed. Also has input on motor & cognitive function via the basal ganglia & cerebellum. -

EPITHALAMUS Sits above the thalamus; contains the pineal gland (releases melatonin) and the habenula (involved in food & water intake).

Dr Ronnie Chen -

18/02/2020

HYPOTHALAMUS The “boss”; its anterior & medial regions direct parasympathetic function, while its posterior & lateral regions direct sympathetic function. Connects to the limbic system, which mediates the fight-or-flight response. Relationship between the hypothalamus and the amygdala & periaqueductal grey matter allows the fear response. Has many functions:  Autonomic regulatory centre  Emotional response  Temperature regulation  Food intake regulation  Water balance regulation  Sleep/wake cycle regulation  Hormonal control

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The limbic system is a series of structures surrounding the limit between the cerebral hemispheres & the brainstem. This includes: Amygdalae (emotion centre) Hippocampus (formation of new s-t memories about past experiences; located in temporal lobes) Cingulate gyus (coordinates smells & sights with pleasant memories, induces emotional reactions to pain & regulates aggressive behaviour) Thalamus (changes in emotional activity) Hypothalamus (changes in emotional activity) Basal ganglia (organises motor behaviour & coordinates rule-based habit learning)

Brainstem Connects the spinal cord, thalamus & cortex and gives rise to most cranial nerves. Contains the midbrain & pons (pathways connecting various parts of the brain) and the medulla oblongata (contains several control centres essential to life -> e.g. pacemaker, breath centre, etc.). Often referred to as the “reptilian brain”. The medulla oblongata is responsible for: - Breathing (inc. coughing) - Swallowing (inc. vomiting) - Heartbeat - Blood pressure

Cerebellum Located at the base of the brain; this is the second largest region, making up 10% of the brain by volume – but containing 50% of its neurones. Can be permanently damaged by trauma/a stroke, or temporarily affected by drugs (e.g. alcohol), which causes a disturbance in balance (i.e. coordination, precision & timing of movement).

Dr Ronnie Chen Responsible for: - Muscle coordination (inc. memory of physical skills) - Balance - Posture

18/02/2020...