A2 Biology Revision - The Different Parts Of The Brain

The Cerebral Cortex Diagram
The Cerebral Cortex Diagram | Source

Cerebrum

  • The cerebrum makes up 75% of our brain's volume, and 85% of it's weight!
  • It is split into two hemispheres (left and right) by the longitudinal fissure. This is what people refer to when they say "I am left brained" and "this exercise is good for the left part of your brain".
  • The left hemisphere generally controls the right side of the body and vis versa, so if you're right handed, you're 'left brained'.
  • The cerebrum is covered by a sheet of neural tissue called the "cerebral cortex" or "neocortex".
  • Roughly 90% of the brain's neurons are located in this 2-4mm thick sheet. This is achieved by having many folds, increasing available surface area.


The Cerebral Cortex

The cerebral cortex consists of 4 parts:

  1. Frontal Lobe "the higher centers of the brain"
  • Decision making, planning, reasoning, consciousness of emotion.
  • Concerned with forming associations by combining information from the other 3 parts of the cortex and our ideas.
  • Includes the primary motor cortex - the area that contains neurons that connect directly to the spinal cord and brain stem (and from there, our muscles). The primary motor cortex sends impulses to muscle cells via motor neurons. This part of the brain also stores information about carrying out different movements.

2. Occipital Lobe - "the visual center of the brain"

  • Also known as the "visual cortex"
  • Concerned with processing information from the eyes: vision, colour, shape & perspective

3. Temporal Lobe - "the hearing center of the brain"

  • Concerned with process auditory information: hearing, sound recognition, and speech (only in the left temporal lobe)

4. Parietal Lobe

Concerned with:

  • Orientation,
  • Movement,
  • Sensation,
  • Calculation
  • Some times of recognition and memory.

Cerebellum
Cerebellum

The Three Lower regions of the brain

Cerebellum - The cerebellum is only 1/8 the size of the cerebrum but is nevertheless very important and controls:

  • Co-ordination,
  • Balance, movement,
  • Breathing,
  • Digestion,
  • The circulation of blood around the body.
  • Receiving information from the primary motor cortex and muscles & joints.

Midbrain - 'The Brain's Junction'

  • Relays information to the cerebral hemispheres
  • Oral information to the temporal lobe
  • Visual information to the occipital lobe

Medulla Oblongata

Unconscious processes:

  • Heart rate
  • Breathing
  • Blood pressure

Brain Stem on a Simple Brain Diagram
Brain Stem on a Simple Brain Diagram

The Brain Stem

  • The brain stem connects the rest of the brain to the spinal cord (and so to the rest of the body).

It also has roles in:

  • Cardiovascular system control,
  • Respiratory control,
  • Pain sensitivity control,
  • Alertness,
  • Consciousness

Detailed diagram of the brain
Detailed diagram of the brain

Other parts of the brain

The Thalamus

  • Responsible for routing all of the incoming sensory information to the correct parts of the brain via the axons of the white matter.

Hypothalamus

  • Lies below the thalamus
  • Contains the thermoregulatory center - monitors core body & skin temperature, initiates negative feedback responses to restore body to optimum temperature.
  • Also contains other centers that control: sleep, thirst, hunger
  • Acts as endocrine gland - secretes hormones like anti-diuretics which controls water re-absorption (in kidneys) and thus controls blood concentration.
  • Hypothalmus is attached directly to the pituitary gland.

Hippocampus

  • Involved in long term memory

Basal Ganglia

  • Group of neurons that lie deep within each hemisphere
  • Responsible for selecting and initiating stores programs for movement

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