The central nervous system

what does CNS include?

• The brain: processes information about external and internal stimuli and co-ordinates the body's responses

• The spinal cord connects the brain to the rest of the nervous system by carring nerve fibres into and out of brain as well as coordinating some reflex responses.

Formation of the brain

• In veertebrates the brian forms as a swelling in the hollow neural tube at the anterior (front) end of a vertebrae embryo and folds back on itself

• Three main areas, forebrain, midbrain and hindbrain.

compelxity of brain

• Some vertebrates have simple brains which have simpler functions such as sight and smell.

• Other vertebrate are more complex like humans.

• The three areas of the brain are difficult to see as the cerebrum, made of two cerebral hemispheres is folded over the entire brain.

what is grey matter

the cell bodies of neurones in the CNS

What is white matter

the nerve fibres of neurones in the CNS

Structure of cerebrum

The cerebrum is divided into two halves known as the

cerebral hemispheres. Cerebrum is biggest and most

highly developed parts of the brain.

• The hemispheres are joined together by a band of nerve fibres known as the corpus callosum

• The right hemisphere controls the left side of the body and the left one controls the right side

• Thin outer later called cerebral cortex

what is cerebral cortex

• The cerebrum has a thin outer layer known as the cerebral cortex or 'grey matter'

  • The cerebral cortex consists of the cell bodies of neurones

  • It is highly folded, which increases its surface area and allows it to contain a greater number of neurones

    • With more neurones in the brain, more neurone connections can be made

    • This is important, as the more connections between neurones in the brain, the greater the ability of the brain to carry out more complex behaviours

what is beneath cerebral cortex

• Beneath the cerebral cortex or grey matter layer is the 'white matter'

  • The white matter consists of the myelinated axons of neurones

fucntion of cerebrum

• The cerebrum is the largest part of the brain in humans, accounting for about 80% of the total mass of the brain

• It carries out a large variety of functions

  involved with conscious activities, including:

  Vision

  Hearing

  Speech

  Thinking

  Memory

what does hypothalamus monitor

• The hypothalamus monitors the blood as it flows through the brain and, in response, releases hormones or stimulates the neighbouring pituitary gland to release hormones

  • The hypothalamus plays an important role in some homeostatic mechanisms and coordinates the autonomic nervous system

Functions of hypothalamus

• Regulating body temperature

  • The hypothalamus monitors blood temperature and initiates a homeostatic response if this temperature gets too high or too low

• Osmoregulation

  • Cells in the hypothalamus monitor the water balance of the blood and releases the hormone ADH if the blood becomes too concentrated

    • ADH increases absorption of water in the kidneys

• Regulating digestive activity

  • The hypothalamus regulates the hormones that control appetite as well as the secretion of digestive enzymes

• Controlling endocrine functions

  • The hypothalamus causes the pituitary gland to release hormones that control a variety of processes e.g. metabolism, growth and development, puberty, sexual functions, sleep, and mood

what is cerebellum?

• Coordinates smooth movement

• Uses information from the muscles and the ears and eyes to control balance and maintain posture

what is the medulla oblongata

• Also known as the medulla

• The medulla contains co-ordination centres that control different unconscious functions e.g.

  • The cardiac centre controls heart rate

  • The respiratory centre controls breathing rate 

• The medulla controls functions that are able to maintain life even if other parts of the brain are damaged. Controls reflex actions eg coughing, sneezing, swallowing, paristalsis and saliva production

job of pituitary gland

• Its role is to produce a range of hormones

  • Some of these directly influence and regulate processes in the body while some stimulate the release of further hormones from other endocrine glands

pituitary gland structure

• The pituitary gland is located below the hypothalamus

• The pituitary gland is divided into two sections; the anterior pituitary and posterior pituitary

  • The anterior pituitary produces and releases hormones

  • The posterior pituitary stores and releases hormones produced by the hypothalamus e.g. ADH and oxytocin