Year 12 Human Biology - The Brain and Spinal Cord

what are the general brain functions

control and integration centre

fundamental body function control

high order functions

receive, process and execute info from senses

what are the 4 main parts

brain stem, diencephalon, cerebrum and cerebellum

describe the structure and functions of the medulla oblongata

top part of the spinal cord, connecting the brain to the spinal cord

it controls basic life functions such as the cardiac centre (regulate heart rate), respiratory centre (initiate breathing) and vasomotor centre (regulate blood vessel diameter)

it controls reflexes

gives rise to the vagus nerve

what are the 2 parts of the brain stem

medulla oblongata and pons

describe the structure and functions of the pons

above the medulla oblongata

connects cerebellum, spinal cord and cerebrum

controls respiratory centre in the medulla

where is the hypothalamus found

it is the floor of the 3rd ventricle in the centre of the brain

what are the functions of the hypothalamus

control autonomic nervous system (therefore most bodily functions)

maintain homeostasis

regulate body temp, water balance, water and food intake, sexual behaviour, basic emotions, endocrine system via pituitary, urinary bladder, sleep cycle, metabolism and stress

secrete antidiuretic hormone, oxytocin, releasing and inhibiting factors

how is nervous tissue organised in the cerebrum

white matter → myelinated fibres

grey matter → cell bodies or neurons, unmyeinated axons and dendrites

grey matter is on the outside and white matter inside

within white matter is basalganglia

describe the cerebrum surface

highly convoluted for increased surface area to hold more neurons

raised ridges → gyri

shallow downfolds → sulci

deep downfolds → fissure

2-4mm of outer layer is the cortex, made of grey matter

what are the 4 lobes of the cerebrum

frontal, parietal, temporal, occipital

(insula is deep within)

what does the frontal lobe control

higher intellect → think, plan, organise, judge, decide, solve, spoken language, working memory)

personality

emotion

voluntary motion

what does the parietal lobe control

process sensory info (temp, pain, touch, taste) from receptors in skin, muscle, mucus membranes

memory

what does the temporal lobe control

sound/hearing

understanding speech

memory

what does the occipital lobe control

visual information

describe the 3 functional areas of the cortex

sensory → receive and process sensory info

assosciation → interpret sensory info and make it useful (intellectual and emotional processes)

motor → send impulses to the muscles, especially for motor control

describe the structure and function of the corpus callosum

large bundle of myelinated fibres connecting both the cerebral hemispheres

lies underneath the cerebrum at the base of the longitudinal fissure

allows the 2 hemispheres to communicate

how do nerves exist in PNS vs CNS

PNS → nerves enclosed in connective tissue

CNS → tracts (nerve fibre bundles in white matter)

describe the structure and functions of the cerebellum

2nd largest part, at lower rear of brain

parallel ridges on the surface, with grey matter outer and branching white matter inner

controls posture, balance, muscel tone, fine coordination of muscle movement

muscle memory

how does the cerebellum correct impulses

it does not initiate impulses, but will compare what the cerebral cortex intended to happen and what is actually happening, then fix the impulse before it reaches the muscle

describe alzheimers

a progressive and degenerative brain disorder

it is the most common type of demetia

what changes does alzheimers cause to the brain

brain shrinkage due to neuron death in the frontal cortex and hippocampus

increase in ventricle size

sulci deepen

what are the reasons for these changes from alzheimers

beta amyloid plaques between neurons prevent communication between the neurons

tau proteins form neurofibrillary tangles within the neurons, causing them to die

drop in levels of acetylcholine transmitter

what are the symptoms of alzheimers

forgetfulness

confusion

cognitive function decline

personality change

what are the treatments for alzheimers

medicine to raise ACh levels, inhibit acetylcholinestrase or block glutamase

cell therapy → inject stem cells (pluripotent) to replace ACh produicng neurons, restoring function or reducing symptoms

describe parkinsons disease

a neurodegenerative disorder characterised by excessive muscle tremors or rigidity

what causes the changes seen in parkinsons disease

neurons in substantia nigra, basal ganglia in cerebrum and motor cortex which control voluntary movement are affected

low dopamine levels or an ACh and dopamine imbalance

what treatment is available for Parkinsons

medicine to substitue or increase dopamine, or inhibit MAO-B or a dopamine precursor (levodopa)

cell therapy (as described fro alzheimers)

describe the spinal cord briefly

it is a nerve cord running from the foreamen magnum to the waist

it is enclosed by the vertebral canal, 3 meninges and epidural fat

what are the functions of the spinal cord

communication pathway between brain and body

sensory info via ascending tracts

motor info via descending tracts

coordinates spinal reflexes

gives rise to 31 nerves of PNS

what is the structure of the spinal cord

white matter outer

grey matter inner

dorsal root ganglion (swelling in dorsal root containing sensory neuron soma)